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UBC Theses and Dissertations

Productivity and diversity of rocky intertidal macroalgae in relation to a seasonally fluctuating environment Pecchioli, Joel Albert 1984

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PRODUCTIVITY AND DIVERSITY OF ROCKY INTERTIDAL MACROALGAE IN RELATION TO A SEASONALLY FLUCTUATING ENVIRONMENT By JOEL ALBERT PECCHIOLI B. S. , Southampton College of Long Island University, 1981 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Department of Botany) We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA A p r i l 1984 © Joel Albert P e c c h i o l i , 1984 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree th a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r agree t h a t permission f o r e x t e n s i v e copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the head o f my department o r by h i s or her r e p r e s e n t a t i v e s . I t i s understood th a t copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without my w r i t t e n permission. Department of fYPt/vY The U n i v e r s i t y of B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date // Ap#-/t~ /^Y i i ABSTRACT The productivity, d i v e r s i t y and community structure of the i n t e r t i d a l macroalgal community i n the v i c i n i t y of Bamfield, B. C , Canada were studied over a f i f t e e n month period (June 1982 to August 1983). Four study s i t e s were examined as representative along a gradient of wave exposure. Algal standing crops were estimated at semi-weekly in t e r v a l s ; these data were used to calculate algal d i v e r s i t y and, i n conjunction with concurrent measurements of photosynthesis, algal productivity. Fucus distichus was most abundant at the upper levels of the three more sheltered s i t e s where i t formed an extensive canopy. The lower shore at the sheltered s i t e s was characterized by a series of spring/summer annual and ephemeral species ( Leathesia difformis , Cryptosiphonia woodii , Ulva  fenestrata , e t c . ) . As wave exposure increased, F. distichus abundance decreased. Mid-shore levels at the exposed s i t e were characterized by an "algal t u r f " while lower levels were dominated by Hedophyllum s e s s i l e Standing crop of a l l species was greatest in spring/summer and least i n winter. At the sheltered s i t e s , d i v e r s i t y was very low in those areas dominated by Fj^ distichus and greater on lower levels of the shore. Diversity was i i i g r e a t e s t i n t h e m i d - s h o r e " a l g a l t u r f " a s s e m b l a g e a t t h e e x p o s e d s i t e and l o w e r i n t h e d i s t i c h u s ( u p p e r ) and H. s e s s i l e ( l o w e r ) d o m i n a t e d z o n e s . I t was p r o p o s e d t h a t t h e o b s e r v e d v e r t i c a l ( t i d a l h e i g h t ) , h o r i z o n t a l (wave e x p o s u r e ) and s e a s o n a l p a t t e r n s o f a l g a l d i v e r s i t y were t h e r e s u l t o f t h e i n t e r a c t i v e e f f e c t s of wave a c t i o n and d e s i c c a t i o n s t r e s s . H e r b i v o r y (by L i t t o r i n a s c u t u l a t a and L. s i t k a n a ) and t h e p r e s e n c e of a F\_ d i s t i c h u s canopy were s e c o n d a r y i n f l u e n c e s . Net d a i l y p h o t o s y n t h e s i s i n F. d i s t i c h u s was g r e a t e s t d u r i n g t h e s p r i n g and e a r l y summer and was p o s i t i v e l y c o r r e l a t e d w i t h water t e m p e r a t u r e . P h o t o s y n t h e t i c r a t e s v a r i e d l i t t l e t h r o u g h o u t t h e y e a r , i n d i c a t i n g t h a t d a y l e n g t h , and n o t p h o t o n f l u x d e n s i t y p e r  se , was more r e s p o n s i b l e f o r t h e o b s e r v e d s e a s o n a l d i f f e r e n c e s i n n e t d a i l y p h o t o s y n t h e s i s . P o s i t i v e n e t d a i l y p r o d u c t i v i t y was o b s e r v e d a l l y e a r , but i n c r e a s e d wave a c t i o n d u r i n g t h e f a l l / w i n t e r l i m i t e d a l g a l s t a n d i n g c r o p s . I t was p r o p o s e d t h a t E\_ d i s t i c h u s p r o d u c t i v i t y i s l i m i t e d by wave a c t i o n i n t h e f a l l and w i n t e r and n u t r i e n t / d e s i c c a t i o n s t r e s s d u r i n g t h e summer. i v TABLE OF CONTENTS Page Abstract 1 1 L i s t of Tables v L i s t of Figures v i i i Acknowledgements x i Chapter One: Introduction 1 Chapter Two: Environmental Monitoring Program 8 Chapter Three: Biomass of I n t e r t i d a l Macroalgae 37 Chapter Four: Invertebrate Abundances 99 Chapter Five: D i v e r s i t y of the Macroalgae . . 134 Chapter Six: P r o d u c t i v i t y of the Macroalgae 165 Concluding Remarks 270 Summary 275 References Cited 278 Appendix A: Photosynthesis-Irradiance Curves 299 V LIST OF TABLES Page 1. Wave exposure ratings at each study s i t e 30 2. C o r r e l a t i o n matrix for selected a b i o t i c environmental factors . 34 3. Per cent time exposed to a i r for each zone and study s i t e f o r selected months 44 4. Sampling i n t e r v a l s f or each s i x - week or two - month "sample month" 45 5. L i s t of i n t e r t i d a l macroalgae c o l l e c t e d during the study 48 6. Combined ( t o t a l ) a l g a l standing crop [g dry wt m-2; (std. dev.)] for each zone at the study s i t e s averaged over the e n t i r e study period 50 7. Analysis of variance of combined a l g a l standing crop (g dry wt m-2) at each study s i t e 51 8. Mu l t i p l e regression analyses of t o t a l a l g a l standing crop (g dry wt m-2) at a l l s i t e s and zones on selected a b i o t i c environmental factors , 54 9. Analysis of variance of Fucus d i s t i c h u s standing crop (g dry wt m-2) i n Zones I and II at each study s i t e , 61 10. M u l t i p l e regression . analyses of Fucus d i s t i c h u s standing crop (g dry wt m-2) at a l l s i t e s and zones on selected a b i o t i c environmental factors . . . 67 11. M u l t i p l e regression analyses of Fucus d i s t i c h u s standing crop (g dry wt m-2) for each zone on selected a b i o t i c environmental factors . . . . . . . . 68 12. Analysis of variance of Leathesia difformis standing crop (g dry wt m-2) i n Zone I I I at Haines, Helby and Wizard f o r 1982 and 1983 75 14. M u l t i p l e regression analysis of Cryptosiphonia woodii standing crop (g dry wt m-2) on selected a b i o t i c environmental factors 15. Summary of standing crop data (g dry wt m-2) and analyses of variance f o r the common secondary species 16. Analysis of variance of Cladophora spp. standing crop (g dry wt m-2) at each study s i t e 22. Fucus d i s t i c h u s c l e a r i n g experiment: analysis of variance of l i t t o r i n e d e n s i t i e s (it 0.0625 m-2) i n the experimental quadrats v i Page 13. M u l t i p l e regression analysis of Leathesia d i f f o r m i s standing crop (g dry wt m-2) on selected a b i o t i c environmental factors 75 77 79 83 17. Analysis of variance of L i t t o r i n a sitkana d e n s i t i e s (# 0.0625 m-2) i n Zones I and II at the study s i t e s . 118 18. Analysis of variance of L i t t o r i n a scutulata d e n s i t i e s (# 0.0625 m-2) i n Zones I and II at the study s i t e s . 1 1 9 19. M u l t i p l e regression analyses of L i t t o r i n a sitkana and L i t t o r i n a scutulata d e n s i t i e s on selected a b i o t i c environmental factors and Fucus d i s t i c h u s standing crop 121 20. Fucus d i s t i c h u s c l e a r i n g experiment: macroalgal standing crops (g dry wt m-2) and l i t t o r i n e d e n s i t i e s (# 0.0625 m-2) 1 2 2 21. Fucus d i s t i c h u s c l e a r i n g experiment: analysis of variance of Fucus d i s t i c h u s standing crop (g dry wt m-2) i n the experimental quadrats ^ 2 3 124 23. Macroalgal standing crop and d i v e r s i t y data for Cape Beale i n the summer 1983 . . . . . . . 1 3 9 24. M u l t i p l e regression analyses of species richness and d i v e r s i t y on selected a b i o t i c environmental factors . ^ - ^ l v i i Page 25. Ash-free (organic) dry weight (g AFW g DRY-1) for selected macroalgae during each six-week sampling i n t e r v a l 184 26. Summary of meteorological data on those days when di u r n a l photosynthesis experiments were performed . 186 27. Summary of the d i u r n a l photosynthesis experiments for Fucus d i s t i c h u s 187 28. Analysis of variance of photosynthesis and r e s p i r a t i o n of Fucus d i s t i c h u s from Zones I and II at Helby 190 29. Results of multiple regression analyses of net and gross d a i l y photosynthesis (mg C g dry wt-1 d-^ -1) of Zone I and II Fucus d i s t i c h u s from Helby on selected a b i o t i c environmental factors 197 30. Summary of the d i u r n a l photosynthesis experiments for Hedophyllum s e s s i l e 206 31. M u l t i p l e regression analyses of net and gross d a i l y photosynthesis(mgC g dry wt-1 d-1) i n Hedophyllum s e s s i l e on selected a b i o t i c environmental factors . 207 32. Ln s i t u blade growth i n Hedophyllum s e s s i l e 209 33. Summary of d i u r n a l photosynthesis experiments for selected i n t e r t i d a l macroalgae 226 34. D a i l y and annual net p r o d u c t i v i t y f o r selected i n t e r t i d a l macroalgae at Haines 232 35. Da i l y and annual net pro d u c t i v i t y for selected i n t e r t i d a l macroalgae at Helby 234 36. Da i l y and annual net pr o d u c t i v i t y f o r selected i n t e r t i d a l macroalgae at Wizard 236 37. D a i l y and annual net pr o d u c t i v i t y f o r selected i n t e r t i d a l macroalgae at Nudibranch 238 38. Summary of d a i l y and annual net pr o d u c t i v i t y by marine benthic macroalgae 262 39. Calculated and estimated parameters of the PS v I re l a t i o n s h i p of selected i n t e r t i d a l macroalgae . . . 322 v i i i LIST OF FIGURES Page 1. Schematic diagram of the re l a t i o n s h i p s between various a b i o t i c environmental f a c t o r s , b i o t i c i n t e r a c t i o n s , macroalgal p r o d u c t i v i t y and macroalgal standing crop . 10 2. Map of the study area i n the v i c i n i t y of Bamfield B r i t i s h Columbia, Canada 12 3. Monthly means of a i r and water temperature, and d a i l y photon f l u x density at the Bamfield Marine Station . . 19 A. Monthly means of surface s a l i n i t y and seawater n i t r a t e + n i t r i t e conentration at each study s i t e 2 3 5. General diagrams of the i n t e r t i d a l transects established at each study s i t e . ^1 6. Mean standing crop (+ or - one standard deviation) of Fucus d i s t i c h u s i n Zones I and II at each study s i t e for each "sample month" 56 7. Mean standing crop (+ & - 1 standard deviation) of Hedophyllum s e s s i l e i n Zone III at Nudibranch f o r each "sample month" 65 8. Mean standing crops of Leathesia d i f f o r m i s , Cryptosiphonia woodii, and C o r a l l i n a V a n c o u v e riensis at each semi-weekly sample time i n Zone I I I at Haines, Helby, and Wizard during the spring and summer of 1982 and 1983 7 1 2 9. Diagram of the 1 m experimental pl o t s set up i n the Fucus d i s t i c h u s c l e a r i n g experiment 104 2 10. Mean d e n s i t i e s (number per 0.0625 m ± one standard deviation) o f L i t t o r i n a sitkana i n Zones I and II at each study s i t e f o r each "sample month" 108 2 11. Mean d e n s i t i e s (number per 0.0625 m ± one standard deviation) of L i t t o r i n a scutulata i n Zones I and II at each study s i t e for each "sample month" 113 I X Page 12. Species richness and d i v e r s i t y of the i n t e r t i d a l macroalgae at Haines f o r each six-week sampling i n t e r v a l 140 13. Species richness and d i v e r s i t y of the i n t e r t i d a l macroalgae at Helby f o r each six-week sampling i n t e r v a l 142 14. Species richness and d i v e r s i t y of the i n t e r t i d a l macroalgae at Wizard f o r each six-week sampling i n t e r v a l 144 15. Species richness and d i v e r s i t y of the i n t e r t i d a l macroalgae at Nudibranch f o r each six-week sampling i n t e r v a l 146 16. Summary of the c l u s t e r analysis of the reduced site-zone-time biomass matrix 152 17. Plot of exp(H') against wave exposure and desiccation stress 158 18. Diurnal curves of net photosynthesis f o r Fucus dist i c h u s from Zones I and II at Helby (mean ± 1 standard deviation) 191 19. Diurnal curves of net photosynthesis f o r Fucus d i s t i c h u s from Zone I at Nudibranch ( mean ± 1 standard deviation) 200 20. Diurnal curves of net photosynthesis f o r Hedophyllum s e s s i l e from Zone III at Nudibranch ( mean ± 1 standard deviation) 203 21. Diurnal curves of net photosynthesis f o r Cladophora spp. ( mean ± 1 standard deviation) 212 22. Diurnal curves of net photosynthesis f o r C o r a l l i n a V a n c o u v e r i e n s i s ( mean ± 1 standard deviation ) . . . . 214 23. Diurnal curve of net photosynthesis f o r Cryptosiphonia woodii (mean ± 1 standard deviation) . . . . . . . 216 24. Diurnal curves of net- photosynthesis f o r Halosaccion americanum (mean ± 1 standard deviation) 218 25. Diurnal curves of net photosynthesis for Leathesia  di f f o r m i s (mean ± 1 standard deviation) 220 X Page 26. Diurnal curves of net photosynthesis for NeorhodOmela l a r i x (mean ± 1 standard deviation) . . . . . . . 222 27. Diurnal curves of net photosynthesis f o r Ulva fenestrata (mean ± 1 standard deviation) 224 28. Photosynthesis-irradiance curves for Fucu9 d i s t i c h u s from Zone I at Helby . 305 29. Photosynthesis-irradiance curves for Fucus dis t i c h u s from Zone II at Helby . 3 0 9 30. Photosynthesis-irradiance curves for Fucus d i s t i c h u s from Zone I at Nudibranch 312 31. Photosynthesis - irradiance curve for Hedophyllum s e s s i l e (21 May 1983) 3 1 4 32. Photosynthesis - i r r a d i a n c e curve for C o r a l l i n a ' vancouveriensis (29 A p r i l 1983) . 316 33. Photosynthesis - i r r a d i a n c e curves for Leathesia d i f f ormis 3 1 8 34. Photosynthesis - irradiance curve for Ulva fenestrata (7 A p r i l 1983) . . . . . . . . 320 v. ACKNOWLEDGEMENTS I would f i r s t l i k e t o thank my r e s e a r c h s u p e r v i s o r , R. E. Foreman, f o r h i s s u p p o r t , a d v i c e , and t h e freedom t o work on a p r o b l e m of g r e a t p e r s o n a l i n t e r e s t . At t i m e s , t h e amount of work i n v o l v e d was o v e r w h e l m i n g , and i t was e n c o u r a g i n g t o know t h a t someone e l s e a l s o b e l i e v e d i n t h e r e s e a r c h . My t h e s i s a d v i s o r y c o m m i t t e e - R. E. DeWreede, A. D. G l a s s , P. G. H a r r i s o n and P. J . H a r r i s o n - c a n o n l y be d e s c r i b e d a s " s u p e r b " . T h e i r s u g g e s t i o n s f o r e x p e r i m e n t a l d e s i g n , comments on t h e m a n u s c r i p t , and w i l l i n g n e s s t o d i s c u s s t h e r e s e a r c h were a g r e a t h e l p . The s t a f f s of t h e B a m f i e l d M a r i n e S t a t i o n , U. B. C. B o t a n y Department and Woodward B i o m e d i c a l L i b r a r y made l i f e much e a s i e r . B a r b a r a B u n t i n g was a g r e a t h e l p i n w o r k i n g i n t h e g r e e n h o u s e and L e s l i e Rimmer p e r f o r m e d t h e n i t r a t e a n a l y s e s . J u l i e O l i v e i r a , D a v i d G a r b a r y and M i c h a e l Hawkes a s s i s t e d w i t h t h e i n d e n t i f i c a t i o n o f some of t h e a l g a e . I am a l s o i n d e b t e d t o t h e O h i a t Band f o r g r a n t i n g me p e r m i s s i o n t o use t h e H a i n e s I s l a n d s t u d y s i t e . S p e c i a l t h a n k s t o a l l my f e l l o w g r a d u a t e s t u d e n t s a t BMS ( e s p e c i a l l y D i a n n a P a d i l l a and C h r i s t i n e Cooke) and my o f f i c e m a t e s a t U. B. C. : y o u r j o k e s , c o o k i n g , and f r i e n s h i p were i n v a l u a b l e . I would a l s o l i k e t o t h a n k M u r r a y x i i Schneider and Catherine Tetu for helping me keep my perspective on the research. This research was supported d i r e c t l y through a series of U. B. C. Graduate Fellowships to J . A. Pecchioli and i n d i r e c t l y via Science Council of B r i t i s h Columbia Grants to R. E. Foreman. F i n a l l y , I would l i k e to dedicate this thesis to my father: thanks for everything (...and I know you've been watching . . . ) . 1 CHAPTER ONE - INTRODUCTION M a r i n e b e n t h i c m a c r o a l g a e a r e an i m p o r t a n t p a r t of many c o a s t a l e c o s y s t e m s (Kuhn and H e l f r i c h , 1957; R y t h e r , 1963; N o r t h , 1971; J o h n s t o n e t a l . , 1977; G u t e r s t a m , 1981; S m i t h , 1981; Mann, 1982). L i k e t h e i r c o u n t e r p a r t s i n t e r r e s t r i a l c o m m u n i t i e s , b e n t h i c m a c r o a l g a e a r e b o t h p r i m a r y p r o d u c e r s and i m p o r t a n t s p a t i a l / t e m p o r a l s t r u c t u r i n g a g e n t s . M a c r o a l g a l beds p r o v i d e t h e h a b i t a t and n u r s e r y g r o u n d s f o r many f i s h and i n v e r t e b r a t e s p e c i e s . The p o t e n t i a l i m p o r t a n c e o f t h e s e p l a n t s a s p r i m a r y p r o d u c e r s i s i n d i c a t e d by t h e s t u d y of Mann ( 1 9 7 2 b ) : t h e a n n u a l p r o d u c t i o n of o r g a n i c m a t t e r by b e n t h i c m a c r o a l g a e i n S t . M a r g a r e t ' s Bay, Nova S c o t i a e x c e e d e d t h a t of t h e p h y t o p l a n k t o n t h r e e - f o l d (603 g C r r r 2 v s 190 g C m" 2) . E x c r e t i o n o f d i s s o l v e d o r g a n i c m a t t e r (DOM) by m a c r o a l g a e may be a c o n s i d e r a b l e p o r t i o n of t h e c a r b o n f i x e d i n p h o t o s y n t h e s i s and a major p a r t of t h e c a r b o n and e n e r g y b u d g e t s f o r c o a s t a l e c o s y s t e m s ( K h a i l o v and B u r l a k o v a , 1969; J o h n s t o n e t a l . , 1977; Mann, 1982). E v e n t u a l l y , a l l o f t h e b e n t h i c p l a n t b i o m a s s , w h i c h c a n be s u b s t a n t i a l ( s e e C h a p t e r 3 ) , e n t e r s d e t r i t a l s y s t e m s . In t e m p e r a t e a r e a s , o n l y a s m a l l p r o p o r t i o n of t h e i n t e r t i d a l m a c r o a l g a l b i o m a s s i s a p p a r e n t l y a c t i v e l y g r a z e d by h e r b i v o r e s (Mann, 1973; 2 Hawkins and H a r t n o l l , 1983); t h u s most of t h e p l a n t b i o m a s s i s i n c o r p o r a t e d i n t o f o o d webs i n n e a r b y b e n t h i c and c o a s t a l a r e a s . S m i t h (1979) has c o n c l u d e d t h a t 80% o f t h e p l a n t l i t t e r from a s i t e i n t h e S t r a i t of G e o r g i a i s t r a n s p o r t e d i n t o c o a s t a l w a t e r s where i t e n t e r s d e t r i t a l f o o d webs. I t t h u s a p p e a r s t h a t b e n t h i c m a c r o a l g a e a c c o u n t f o r a l a r g e p r o p o r t i o n of t h e p r i m a r y p r o d u c t i o n of c o a s t a l w a t e r s and a r e i m p o r t a n t i n many d e t r i t a l and f i l t e r - f e e d i n g f o o d webs. An u n d e r s t a n d i n g of t h e p r i m a r y p r o d u c t i v i t y o f a community i s f u n d a m e n t a l t o f u r t h e r c o m p r e h e n s i o n o f o t h e r e c o l o g i c a l and e n e r g e t i c a s p e c t s o f t h e community ( W e s t l a k e , 1963; C o n n e l l and O r i a s , 1964; M a r g a l e f , 1966; P a i n e , 1966; Mann, 1969). P r i m a r y p r o d u c t i v i t y , as u s e d h e r e , i s t h e r a t e of f l o w of e n e r g y (or c a r b o n ) i n t o t h e f i r s t ( p r o d u c e r ) t r o p h i c l e v e l ( W e s t l a k e , 1965). - ~ S t u d i e s e x a m i n i n g t h e p r i m a r y p r o d u c t i v i t y o f m a r i n e m a c r o a l g a e have g e n e r a l l y been of l i m i t e d s c o p e and a p p l i c a b i l i t y , but have i n d i c a t e d t h e p o t e n t i a l l y h i g h p r o d u c t i v i t y of t h e s e p l a n t s (Mann, 1973, 1982). Most s t u d i e s have examined o n l y one o r two s p e c i e s ( e . g. Wassman and Ramus, 1973; Z a v o d n i k , 1973; K i n g and Schramm, 1976a; P a r k e r , 1981) o r have measured p r o d u c t i v i t y o v e r s h o r t t i m e p e r i o d s and e x t r a p o l a t e d t h e s e d a t a t o e s t i m a t e a n n u a l p r o d u c t i v i t y ( e . g. J o h n s t o n , 1969; Towle and P e a r s e , 1973). O t h e r m e t h o d o l o g i c a l p r o b l e m s i n c l u d e b a s i n g p r o d u c t i v i t y measurements on b i o m a s s c h a n g e s ( w h i c h can 3 g r e a t l y u n d e r e s t i m a t e p r o d u c t i v i t y — see Mann, 1972b; B r i n k h u i s , 1977c) or m e a s u r i n g p h o t o s y n t h e s i s d u r i n g o n l y p a r t of t h e day and i g n o r i n g p o s s i b l e d i u r n a l c h a n g e s i n p h o t o s y n t h e t i c r a t e s (Ramus and R o s e n b e r g , 1980; Kremer, 1981). V e r y few s t u d i e s have combined s a m p l i n g programs t o e s t i m a t e m a c r o a l g a l b i o m a s s w i t h c o n c u r r e n t measurements o f p h o t o s y n t h e s i s o v e r a c o m p l e t e y e a r t o c a l c u l a t e a n n u a l p r i m a r y p r o d u c t i v i t y ( B r i n k h u i s 1977a,b,c; H a t c h e r e t a l . , 1977; J o h n s t o n e t a l . , 1977). The p r o d u c t i v i t y o f v a r i o u s k e l p s p e c i e s has been s t u d i e d i n some d e t a i l (Mann, 1972b; H a t c h e r e t a l . , 1977; J o h n s t o n e t a l . , 1977; G e r a r d and Mann, 1979). However, s i m i l a r c o m p r e h e n s i v e and l o n g - t e r m s t u d i e s of i n t e r t i d a l m a c r o a l g a e a r e r a r e ( Z a v o d n i k , 1973). The r e l a t i o n s h i p s between m a c r o a l g a l p r o d u c t i v i t y and v a r i o u s e n v i r o n m e n t a l f a c t o r s a r e , e x c e p t f o r a few s p e c i e s , p o o r l y u n d e r s t o o d . The work o f Chapman and C r a i g i e (1977, 1978), H a t c h e r e t a l . ( 1 9 7 7 ) , Chapman and L i n d l e y ( 1 9 8 0 ) , Mann e t a l . (1980) and Gagne e t a l . (1982) on v a r i o u s s p e c i e s o f L a m i n a r i a i n Nova S c o t i a and t h e A r c t i c have shown t h a t l i g h t may l i m i t g r o w t h d u r i n g p a r t of t h e y e a r w h i l e t h e a v a i l a b i l i t y of n i t r o g e n may be l i m i t i n g a t o t h e r t i m e s . L a m i n a r i a may s t o r e n i t r o g e n and c a r b o n f o r l a t e r use when, r e s p e c t i v e l y , ambient n i t r o g e n or l i g h t l e v e l s a r e l i m i t i n g t o g r o w th (Chapman and C r a i g i e , 1977; Chapman and L i n d l e y , 1980). T h i s a b i l i t y may be c h a r a c t e r i s t i c o f p e r e n n i a l m a c r o a l g a e and may, i n p a r t , e x p l a i n t h e o b s e r v e d 4 h i g h p r o d u c t i v i t y of t h e s e p l a n t s ( T o p i n k a , 1978; Wheeler and N o r t h , 1980; Mann, 1982; R o s e n b e r g and Ramus, 1982a). The a t t a c h e d h a b i t of b e n t h i c m a c r o a l g a e , c o n t i n u a l l y washed by waves and c u r r e n t s , e n s u r e s a c o n s t a n t r e p l e n i s h m e n t of n u t r i e n t s and d i s s o l v e d g a s s e s , and may a l s o be an i m p o r t a n t f a c t o r i n f l u e n c i n g m a c r o a l g a l p r o d u c t i v i t y . By b r e a k i n g down b a r r i e r s t o d i f f u s i o n ( i . e . b o u n d a r y l a y e r s a r o u n d t h e p l a n t t h a l l i ) , water m o t i o n may enhance r a t e s of p h o t o s y n t h e s i s and n u t r i e n t u p t a k e ( W h e e l e r , 1980; P a r k e r , 1981; G e r a r d , 1982); however, h i g h l e v e l s of water m o t i o n and may l i m i t a l g a l s t a n d i n g c r o p s and p r o d u c t i v i t y ( G e r a r d and Mann, 1979; Mann e t a l . , 1980). The s i t u a t i o n i s more complex w i t h i n t e r t i d a l m a c r o a l g a e , e x p o s e d as t h e y a r e t o t h e f l u c t u a t i n g e n v i r o n m e n t a l c o n d i t i o n s imposed by t h e t i d a l c y c l e . R e c e n t s t u d i e s have d e m o n s t r a t e d t h a t i n t e r t i d a l m a c r o a l g a e may show a d a p t a t i o n s o f p h o t o s y n t h e s i s and n u t r i e n t u p t a k e t o t h e t i d a l c y c l e . P h o t o s y n t h e s i s by some i n t e r t i d a l m a c r o a l g a e has been shown t o be g r e a t e s t when t h e p l a n t s a r e e x p o s e d t o a i r and d e s i c c a t e d 10-25% ( J o h n s o n e t a l . , 1974; B r i n k h u i s e t a l . , 1976; Q u a d i r e t a l . , 1979; D r i n g and Brown, 1982). The r e s p o n s e o f p h o t o s y n t h e s i s t o p e r i o d i c submergence and e x p o s u r e has been i m p l i c a t e d a s a p o s s i b l e mechanism i n f l u e n c i n g t h e z o n a t i o n of i n t e r t i d a l m a c r o a l g a e ( J o h n s t o n e t a l . , 1974; Schonbeck and N o r t o n , 1978; Q u a d i r e t a l . , 1979; D r i n g and Brown, 1982; O a t e s and M u r r a y , 5 1983). T h e s e p l a n t s may a l s o show a d a p t a t i o n s t o t a k e a d v a n t a g e o f t h e l i m i t e d p e r i o d s of submergence t o t a k e up n u t r i e n t s (Thomas and T u r p i n , 1980; Thomas, 1983). The main g o a l of t h i s r e s e a r c h i s t o a c q u i r e an i n c r e a s e d u n d e r s t a n d i n g o f t h e m a g n i t u d e and r o l e o f m a c r o a l g a l p r o d u c t i v i t y i n r o c k y i n t e r t i d a l c o m m u n i t i e s . A number of w o r k e r s have d e m o n s t r a t e d t h e i m p o r t a n c e of a b i o t i c f a c t o r s and b i o l o g i c a l i n t e r a c t i o n s i n s t r u c t u r i n g r o c k y i n t e r t i d a l c o m m u n i t i e s (Lodge, 1948; Burrows and Lodge, 1950; D a y t o n , 1971, 1975; C o n n e l l , 1972; C u b i t , 1974; P a i n e , 1974, Menge, 1976, 1978; L u b c h e n c o and Menge, 1978; S o u s a , 1979; L u b c h e n c o , 1980, 1983; Underwood, 1980; Hawkins, 1981, 1983; S a n t e l i c e s e t a l . , 1981; Sousa e t a l . , 1981; Underwood and J e r n a k o f f , 1981; K a s t e n d i e k , 1982; J e r n a k o f f , 1983; Underwood e t a l . , 1983). However, t h e l a c k of a l g a l p r o d u c t i v i t y d a t a has l i m i t e d t h e c o n c l u s i o n s w h i c h can be drawn from t h e s e s t u d i e s ( L u b c h e n c o and G a i n e s , 1981; Hawkins and H a r t n o l l , 1983). L o n g - t e r m s t u d i e s a r e needed t o p r o p e r l y e v a l u a t e t h e i n t e r a c t i o n s between a l g a l p r o d u c t i v i t y , a l g a l g r o w t h s t r a t e g i e s , i n t e r t i d a l community s t r u c t u r e , and a s e a s o n a l l y f l u c t u a t i n g e n v i r o n m e n t . The r e l a t i o n s h i p between n e t p r o d u c t i v i t y , as e s t i m a t e d w i t h p h y s i o l o g i c a l d e t e r m i n a t i o n s of p h o t o s y n t h e s i s and r e s p i r a t i o n , and t h e s t a n d i n g c r o p of m a c r o a l g a e may p r o v i d e i n s i g h t i n t o t h e e c o l o g y and e n v i r o n m e n t a l p h y s i o l o g y of t h e s e p l a n t s . 6 Five main objectives are approached in the course of this research: 1) to quantify the productivity of rocky i n t e r t i d a l macroalgae and relate this to a number of environmental factors, such as l i g h t , nutrient a v a i l a b i l i t y , and herbivory; 2) to examine the relationship between photosynthesis, in the form of net productivity, and alg a l standing crop; 3) to examine diurnal and seasonal changes in alga l photosynthetic rates and relate these changes to problems 1 and 2 ; 4) to study patterns of alg a l species d i v e r s i t y along both the v e r t i c a l ( t i d a l exposure) and horizontal (wave exposure) gradients and to relate a l g a l species d i v e r s i t y to productivity; 5) to examine the relat i o n s h i p between macroalgal productivity and i n t e r t i d a l community structure. Although this study cannot provide d e f i n i t i v e answers to each of the above-mentioned problems — the lim i t a t i o n s imposed by geography and time are apparent — the information gained should provide insight into the role of macroalgae in the ecology of rocky i n t e r t i d a l communities. Rocky i n t e r t i d a l organisms interact in a number of complex ways 7 w i t h t h e i r e n v i r o n m e n t and w i t h e a c h o t h e r . Any i n f o r m a t i o n c o n c e r n i n g s u c h i n t e r a c t i o n s can o n l y add t o our u n d e r s t a n d i n g of t h e s e communites and t o t h e f u r t h e r d e v e l o p m e n t of g e n e r a l e c o l o g i c a l p r i n c i p l e s . 8 CHAPTER 2 - ENVIRONMENTAL MONITORING PROGRAM Photosynthesis and resp i r a t i o n , the primary metabolic processes determining algal productivity, are affected by various environmental factors in complex and interactive ways. Ecological processes, d i s t i n c t from physiological processes, may further influence a l g a l productivity. Temperate latitudes generally have seasonal cycles in a number of abiotic factors which may be important influences on productivity. Also, b i o t i c interactions, such as herbivory and competition, may l i m i t a l g a l standing crop (thus reducing productivity) and be a major structuring agent in the i n t e r t i d a l community. In order to better understand the effects of some of these factors on alg a l productivity, selected environmental parameters were monitored throughout the study: 1) l i g h t 2) a i r and water temperature 3) seawater n i t r a t e concentration 4 ) s a l i n i t y 5) wave exposure 6) invertebrate abundances 7 ) t i d a l cycle Figure 1 is a schematic diagram of the possible interactions between those a b i o t i c and b i o t i c factors most 9 l i k e l y t o i n f l u e n c e i n t e r t i d a l a l g a l p r o d u c t i v i t y . E a c h of t h e s e f a c t o r s may a f f e c t p r o d u c t i v i t y and f a c t o r i n t e r a c t i o n s may p r o d u c e s y n e r g i s t i c - e f f e c t s . S e a s o n a l c h a n g e s i n t h e s e f a c t o r s , c o u p l e d w i t h c y c l e s of g r o w t h , r e p r o d u c t i o n and r e c r u i t m e n t , must a l s o be c o n s i d e r e d V a r i a t i o n s i n t h e r e c r u i t m e n t o f i n d i v i d u a l s may be a m a j o r i n f l u e n c e on a l g a l p r o d u c t i v i t y and i n t e r t i d a l community s t r u c t u r e , but l i t t l e work has been c o m p l e t e d on t h i s a s p e c t o f t h e e c o l o g y o f i n t e r t i d a l m a c r o a l g a e ( L e w i s , 1977; Hruby and N o r t o n , 1979; G u n n i l l , 1980; Underwood e t a l . , 1983). The S t u d y A r e a The s t u d y was c o n d u c t e d i n t h e v i c i n i t y of t h e B a m f i e l d M a r i n e S t a t i o n , B a r k l e y Sound, V a n c o u v e r I s l a n d , B.C., Canada (48° 52' 30" N, 125° 07' 30' W; F i g u r e 2 ) . Due t o u p w e l l i n g o f d eep w a t e r , t h i s a r e a i s a " b i o l o g i c a l h o t s p o t " and i m p o r t a n t c o m m e r c i a l f i s h e r y (Thomson, 1981). The t i d a l r a n g e i s a p p r o x i m a t e l y 4.1 m (-0.2 t o +3.9 m C a n a d i a n datum; I n s t i t u t e of Ocean S c i e n c e s , Sydney, B.C.) w i t h t h e l o w e s t low t i d e s d u r i n g t h e e a r l y m o r n i n g i n t h e summer and t h e h i g h e s t t i d e s i n December and J a n u a r y . F i v e s i t e s were c h o s e n , b a s e d on i n i t i a l s u b j e c t i v e e v a l u a t i o n s , as r e p r e s e n t a t i v e a r e a s a l o n g a g r a d i e n t of 10 Figure 1 Schematic diagram of the r e l a t i o n s h i p s between various a b i o t i c environmental f a c t o r s , b i o t i c i n t e r a c t i o n s , macroalgal p r o d u c t i v i t y , and macroalgal standing crop. T i d e C y c l e L i g h t T e m p e r a t u r e N u t r i e n t s Wa te r M o t i o n S a l i n i t y Net P r o d u c t i v i t y —* H e r b i v o r y Wave A c t i o n O t h e r s «— D O M E x c r e t i o n • S t a n d i n g C r o p 12 Figure 2 Map of the study area in the v i c i n i t y of Bamfield, B r i t i s h Columbia, Canada. 14 wave e x p o s u r e ( F i g u r e 2 ) . The s u b s t r a t e a t e a c h s i t e c o n s i s t e d of s o l i d p l a t f o r m s o f medium g r a i n e d g r a n o d i o r i t e and q u a r t z d i o r i t e ( M u l l e r , 1974). From most s h e l t e r e d t o most e x p o s e d , t h e f i v e s t u d y s i t e s a r e H a i n e s I s l a n d , H e l b y I s l a n d , W i z a r d I s l e t , N u d i b r a n c h P o i n t , and Cape B e a l e ( h e r e a f t e r c a l l e d " H a i n e s " , " H e l b y " , " W i z a r d " , " N u d i b r a n c h " , and " B e a l e " ; F i g u r e 2 ) . The f i r s t f o u r s i t e s c an be d e s i g n a t e d as " p r o t e c t e d o u t e r c o a s t " and B e a l e as "open c o a s t " , as p e r R i c k e t t s e t a l . ( 1 9 6 8 ) . The H a i n e s s i t e i s l o c a t e d on a f l a t s h e l f w i t h i n t h e c o n f i n e s of Dodger C h a n n e l and b e h i n d two n a t u r a l b r e a k w a t e r s w h i c h p r o t e c t i t from t h e heavy s w e l l i n T r e v o r C h a n n e l . The wave a c t i o n a t t h i s s i t e i s u s u a l l y m i n i m a l , even d u r i n g s e v e r e w i n t e r s t o r m s . O f f s h o r e o f t h e s i t e , t h e s u b s t r a t e i s sandy and p o p u l a t e d by a bed o f Z o s t e r a m a r i n a L. and M a c r o c y s t i s i n t e g r i f o l i a B o r y . H e l b y i s i n many ways s i m i l a r t o H a i n e s ( i . e . a r e l a t i v e l y f l a t s h e l f p r o t e c t e d from heavy s w e l l by a s e r i e s of n a t u r a l b r e a k w a t e r s ) . However, s t r o n g w i n d s from t h e n o r t h w e s t i n c r e a s e wave a c t i o n a t t h i s . s i t e . In a d d i t i o n , f a i r l y r a p i d t i d a l c u r r e n t s f l o w p a s t t h e H e l b y s i t e . O f f s h o r e , t h e s u b s t r a t e c o n s i s t s o f s a n d , s h e l l s and c o b b l e , w i t h a s m a l l bed of i n t e g r i f o l i a . Human d i s t u r b a n c e , i n t h e f o rm o f l a n d c l e a r i n g above t h e s i t e , may have a f f e c t e d t h e upper l e v e l s o f t h e s h e l f i n t h e f a l l o f 1982 and w i n t e r of 1983. 15 W i z a r d i s l o c a t e d a t t h e j u n c t u r e of T r e v o r C h a n n e l and S a t e l l i t e P a s s a g e , and t h u s i s e x p o s e d t o f a i r l y s t r o n g t i d a l and w i n d - i n d u c e d c u r r e n t s . However, H e l b y I s l a n d b l o c k s most o f t h e o c e a n i c s w e l l and t h e t r a n s e c t s were l a i d on t h e p r o t e c t e d s i d e o f W i z a r d . S m a l l beds of M. i n t e g r i f o l i a and N e r e o c y s t i s l u e t k e a n a ( M e r t . ) P o s t . e t Rupr. a r e l o c a t e d j u s t o f f s h o r e o f t h i s s i t e . The N u d i b r a n c h s i t e i s e x p o s e d t o heavy wave a c t i o n when o c e a n i c s w e l l s a r e from t h e s o u t h ; wave a c t i o n i s r e d u c e d when t h e winds a r e from t h e n o r t h , b u t s t i l l g r e a t e r t h a n t h a t a t t h e t h r e e more p r o t e c t e d s i t e s . Due t o s e v e r e weather and s e a c o n d i t i o n s , no q u a n t i t a t i v e d a t a c o u l d be o b t a i n e d a t N u d i b r a n c h between December 1982 and l a t e - M a r c h 1983. An e x t e n s i v e bed of N^ l u e t k e a n a l i e s j u s t o f f s h o r e of t h e s i t e . Cape B e a l e i s an e x t r e m e l y e x p o s e d p o i n t o f l a n d a t t h e s o u t h w e s t e n t r a n c e t o B a r k l e y Sound. T h e r e i s no p r o t e c t i o n from t h e o n s h o r e s w e l l o f t h e P a c i f i c Ocean. B e c a u s e o f t h e h a z a r d o u s c o n d i t i o n s , B e a l e was v i s i t e d on o n l y two o c c a s i o n s i n the* summer o f 1983. The s h o r e a t B e a l e i s d o m i n a t e d by P o s t e l s i a p a l m a e f o r m i s Rupr. and M y t i l u s  c a l i f o r n i a n u s C o n r a d , an a s s e m b l a g e c h a r a c t e r i s t i c of o n l y t h e most e x p o s e d s h o r e s ( R i g g and M i l l e r , 1949; P a i n e , 1979). 16 Methods and M a t e r i a l s T h r i c e d a i l y measurements, a t 0800h, 1200h, and I600h PST, o f p h o t o n f l u x d e n s i t y (PFD; PAR, 400-700 nm), a i r and water t e m p e r a t u r e , and g e n e r a l m e t e o r o l o g i c a l c o n d i t i o n s ( c l o u d c o v e r , e t c . ) were made a t t h e B a m f i e l d M a r i n e S t a t i o n . T e m p e r a t u r e was measured w i t h e i t h e r a m e r c u r y o r r e d - a l c o h o l t h e r m o m e t e r. Water t e m p e r a t u r e was o b t a i n e d a t a d e p t h o f 0.5 m. I n s t a n t a n e o u s PFD was m e a s u r e d w i t h a LICOR Model L I - 1 8 5 Quantum meter (Lambda I n s t r u m e n t C o r p o r a t i o n ) . T o t a l d a i l y p h o t o n f l u x was o b t a i n e d u s i n g a LICOR Model LI-500 I n t e g r a t o r . P r e c i p i t a t i o n d a t a was o b t a i n e d f r o m P. J a n i t i s ( p e r s . comm.). At l e a s t once e a c h week d u r i n g t h e s t u d y p e r i o d (June 1982 t o A u g u s t 1983), t h e f o l l o w i n g p a r a m e t e r s were measured a t e a c h s t u d y s i t e ( e x c e p t B e a l e ) : 1) a i r and water t e m p e r a t u r e 2) s a l i n i t y 3) s e a w a t e r n i t r a t e c o n c e n t r a t i o n 4) wave a c t i o n A l l measurements were t a k e n from a b o a t 10 t o 50 m o f f s h o r e of t h e t r a n s e c t s a t e a c h s i t e . Water t e m p e r a t u r e was measured a t a d e p t h o f 0.5 m. The v a l u e s of a i r and water t e m p e r a t u r e were t a k e n f o r p u r p o s e s of c o m p a r i s o n w i t h t h e more c o m p l e t e d a t a c o l l e c t e d a t t h e B a m f i e l d M a r i n e S t a t i o n (BMS). The water t e m p e r a t u r e and s a l i n i t y d a t a f o r B e a l e 17 were p r o v i d e d by t h e B a m f i e l d M a r i n e S t a t i o n . S u r f a c e s e a w a t e r samples were c o l l e c t e d i n 30 ml o r 125 ml a c i d washed (10% HC1) p o l y p r o p y l e n e b o t t l e s . Samples f o r n i t r a t e a n a l y s i s were p r e s e r v e d w i t h a few d r o p s of c h l o r o f o r m , f r o z e n when r e t u r n e d t o t h e l a b o r a t o r y , and l a t e r a n a l y z e d . N i t r a t e (+ n i t r i t e ) c o n c e n t r a t i o n was d e t e r m i n e d u s i n g a T e c h n i c o n I I A u o t o a n a l y z e r and t h e m e t h o d o l o g y of S t r i c k l a n d and P a r s o n s ( 1 9 7 2 ) . S a l i n i t y was d e t e r m i n e d i n t h e l a b o r a t o r y w i t h a c o n d u c t i v i t y meter (Type CDM 2e R a d i o m e t e r ) . The measurement o f n e a r s h o r e w a t e r movement has been a p r o b l e m p l a g u i n g i n t e r t i d a l e c o l o g i s t s f o r many y e a r s . I t i s e x t r e m e l y d i f f i c u l t t o o b t a i n m e a n i n g f u l q u a n t i t a t i v e d a t a f o r wave a c t i o n and c u r r e n t s . D r u e h l (1981) e v a l u a t e d t h e d r o g u e - t e c h n i q u e ( J o n e s and D e m e t r o p o u l o u s , 1968) and t h e p l a s t e r - o f - p a r i s c o n s t r u c t m e t h o d o l o g y (Muus, 1968; Do t y , 1971) and f o u n d b o t h p r o c e d u r e s l a c k i n g . In l i g h t of D r u e h l ( 1 9 8 1 ) , I have f a l l e n back on a s u b j e c t i v e measure of wave a c t i o n as t h e b e s t a v a i l a b l e method t o rank s i t e s r e l a t i v e t o one a n o t h e r . At e a c h v i s i t t o e a c h s t u d y s i t e , a s u b j e c t i v e r a t i n g of 1 t o 10, b a s e d on t h e sea s t a t e and d e g r e e of " p o u n d i n g " of t h e s h o r e , was made t o d e s c r i b e t h e o b s e r v e d wave e x p o s u r e . I t s h o u l d be n o t e d t h a t t h e s e a r e " m i n i m a l r a n k i n g s " , a s s e v e r e w e a t h e r c o n d i t i o n s o f t e n p r o h i b i t e d t r a v e l t o t h e s t u d y s i t e s . 18 R e s u l t s a) L i g h t and T e m p e r a t u r e The l i g h t , a i r and water t e m p e r a t u r e d a t a c o l l e c t e d a t th e B a m f i e l d M a r i n e S t a t i o n a r e summarized i n F i g u r e 3. A l l t h r e e a b i o t i c f a c t o r s showed a s t r o n g s e a s o n a l p a t t e r n , w i t h the, l o w e s t v a l u e s r e c o r d e d i n t h e w i n t e r (November t o J a n u a r y ) and t h e h i g h e s t v a l u e s r e c o r d e d i n t h e summer (June t o A u g u s t ) . Mean m o n t h l y a i r t e m p e r a t u r e r a n g e d between 6.0° C i n November 1982 and 18.3° C i n A u g u s t 1983. The l o w e s t mean m o n t h l y water t e m p e r a t u r e was 6.6° C ( J a n u a r y 1983) and t h e h i g h e s t , 16.0° C (June 1982). Water t e m p e r a t u r e was 1.0-3.4° C l e s s t h a n a i r t e m p e r a t u r e e a c h month ( e x c e p t November 1982). M o n t h l y mean a i r and water t e m p e r a t u r e s were r e l a t i v e l y c o n s t a n t d u r i n g t h e summer months. Mean d a i l y PFD p e r month showed a s e a s o n a l p a t t e r n s i m i l a r t o t h a t of a i r and wa t e r t e m p e r a t u r e . A maximum v a l u e o f 33 E i n r r r 2 d a y " 1 was r e c o r d e d i n June .1982 and a minimum v a l u e o f 3 E i n r r r 2 d a y " 1 o b s e r v e d i n December 1982. The water and a i r t e m p e r a t u r e d a t a c o l l e c t e d a t e a c h s t u d y s i t e were c o m p a r a b l e t o e a c h o t h e r and t o t h e BMS d a t a . No b e t w e e n - s i t e d i f f e r e n c e s were a p p a r e n t . In a l l a n a l y s e s , t h e r e f o r e , t h e BMS d a t a w i l l be u s e d and assumed 19 Figure 3 Monthly means of a i r and water temperature, and d a i l y photon flux density at the Bamfield Marine Station. • = A i r Temperature • = Water Temperature A = Photon Flux Density Month o 21 t o be r e p r e s e n t a t i v e of t h e c o n d i t i o n s a t e a c h s i t e . However, t h e w ater t e m p e r a t u r e a t B e a l e was s l i g h t l y l o w e r d u r i n g t h e summer 1982, and h i g h e r d u r i n g t h e w i n t e r 1982-83, t h a n a t t h e o t h e r s i t e s . D a i l y v a r i a t i o n i n a i r t e m p e r a t u r e a v e r a g e d 3.8° C and was g r e a t e s t i n June 1982 (5.5° C ) , September 1982 (5.4° C ) , and A p r i l and A u g u st 1983 ( 5 . 4 ° C ) ; l e a s t d a i l y v a r i a t i o n i n a i r t e m p e r a t u r e was r e c o r d e d i n J a n u a r y 1983 (0.6° C ) . D a i l y v a r i a t i o n i n s u r f a c e water t e m p e r a t u r e a v e r a g e d 1.0° C w i t h t h e maximum v a r i a t i o n r e c o r d e d i n June 1982 (3.0° C) and t h e minimum v a r i a t i o n i n December 1982 ( 0 . 1 ° C ) . I n s t a n t a n e o u s PFD ( m o n t h l y mean, I200h) g r e a t e r t h a n 1000 JJE ITT 2 s " 1 were r e c o r d e d i n June t o A u g u s t 1982 and A p r i l t o A u g u s t 1983. The l o w e s t r e c o r d e d PFD ( m o n t h l y mean, 1200h) was 220 pE r r r 2 s " 1 i n December 1982. B) Seawater N i t r a t e C o n c e n t r a t i o n The n i t r a t e d a t a c o l l e c t e d a t e a c h s t u d y s i t e a r e p r e s e n t e d i n F i g u r e s 4a-d. A g e n e r a l s e a s o n a l p a t t e r n i n s u r f a c e n i t r a t e (+ n i t r i t e ) c o n c e n t r a t i o n i s a p p a r e n t . At e a c h s i t e , v a l u e s were h i g h and v a r i a b l e between September 1982 and M a r c h 1983. N i t r a t e c o n c e n t r a t i o n was a l w a y s g r e a t e r t h a n 2.5 u g - a t NO^ l " 1 d u r i n g t h e s e months and u s u a l l y e x c e e d e d 6.0 y g - a t N O ^ l ~ 1 . A marked d r o p i n n i t r a t e c o n c e n t r a t i o n o c c u r r e d a t a l l s i t e s i n A p r i l 1983. 22 From A p r i l t o A u gust 1983 n i t r a t e l e v e l s were c o n s i s t e n t l y below 2 p g - a t NO^ 1~ 1 and u s u a l l y l e s s t h a n 1.0 p g - a t N O ^ l " 1 . I t s h o u l d be n o t e d , however, t h a t t h r e e s e a w a t e r s a m p l e s c o l l e c t e d i n June 1983 had n i t r a t e c o n c e n t r a t i o n s e x c e e d i n g 10 p g - a t N O ^ l " 1 ( t h e s e v a l u e s were not i n c l u d e d i n t h e c a l c u l a t e d means p r e s e n t e d i n F i g u r e s 4a-d) . C) S a l i n i t y The s a l i n i t y d a t a c o l l e c t e d a t e a c h s i t e a r e p r e s e n t e d i n F i g u r e s 4a~e. S a l i n i t y t e n d e d t o v a r y g r e a t l y from one month t o a n o t h e r . The o n l y e v i d e n t s e a s o n a l t r e n d was a maximum o b s e r v e d from A u g u s t t o O c t o b e r 1982 a t e a c h s i t e . S a l i n i t y was g r e a t e s t a t B e a l e , and g e n e r a l l y g r e a t e r a t H a i n e s and N u d i b r a n c h compared t o H e l b y and W i z a r d . Mean s u r f a c e s a l i n i t i e s f o r e a c h s i t e o v e r t h e e n t i r e s t u d y p e r i o d were: H a i n e s — 27.6 p p t ; H e l b y — 25.7 p p t ; W i z a r d — 25.0 p p t ; N u d i b r a n c h - 27.6 p p t ; B e a l e - 29.7 p p t . On a s e a s o n a l b a s i s , t h e d i f f e r e n c e s i n s a l i n i t i e s a t H a i n e s / N u d i b r a n c h and H e l b y / W i z a r d were l e a s t d u r i n g A u g u s t t o September 1982 and g r e a t e s t (and more v a r i a b l e ) d u r i n g t h e r e s t of t h e y e a r . 23 F i g u r e A Monthly means of s u r f a c e s a l i n i t y and seawater n i t r a t e + n i t r i t e c o n c e n t r a t i o n s at each study s i t e , A) Haines B) Helby C) Wizard D) Nudibranch E) B e a l e ( s a l i n i t y o n l y ) # = S a l i n i t y • = N 0 3 + N0 2 M o n t h 28 29 D) Wave A c t i o n The d a t a f o r wave e x p o s u r e , b a s e d on a s u b j e c t i v e r a t i n g s c a l e , a r e p r e s e n t e d i n T a b l e 1. A s e a s o n a l t r e n d i s e v i d e n t , w i t h g r e a t e s t e x p o s u r e o c c u r r i n g i n t h e f a l l and w i n t e r ( O c t o b e r 1982 t o March 1983) and c a l m e r c o n d i t i o n s p r e v a i l i n g i n t h e s p r i n g and summer ( A p r i l t o S e p t e m b e r ) . N o t e t h a t t h e r e was v e r y l i t t l e s e a s o n a l change i n t h e wave a c t i o n a t H a i n e s . S t r o n g e r s e a s o n a l p a t t e r n s were o b s e r v e d a t W i z a r d and N u d i b r a n c h . The method of B a a r d s e t h (1970) f o r c a l c u l a t i n g an i n d e x of wave e x p o s u r e was a d a p t e d f o r t h i s s t u d y . T h i s method i s b a s e d on t h e r e l a t i o n s h i p between wave e x p o s u r e and t h e d e g r e e s o f a r c open t o t h e s e a . A f e t c h of 1 km ( n o t 7.5 km) was u s e d due t o t h e g e o g r a p h y of t h e s t u d y a r e a . The f o l l o w i n g d a t a ( i n d e g r e e s of a r c ) were o b t a i n e d f o r t h e s t u d y s i t e s : H a i n e s — 0; H e l b y — 25; W i z a r d — 81; N u d i b r a n c h - 148; B e a l e - 182. D i s c u s s i o n The v a l u e s r e c o r d e d f o r t h e v a r i o u s e n v i r o n m e n t a l f a c t o r s m o n i t o r e d d u r i n g t h e s t u d y p e r i o d a g r e e d w i t h t h o s e n o t e d by o t h e r w o r k e r s f o r B a r k l e y Sound. T a b l e 1. Wave exposure r a t i n g s a t each s tudy s i t e . MONTH HAINES HELBY MIN MAX MIN MAX EXP EXP EXP EXP WIZARD MIN MAX EXP EXP NUDIBRANCH MIN EXP MAX EXP MEAN MIN MEAN MAX 1982 August September Oc tober November December 1983 January F e b r u a r y March Apr i 1 May June J u l y August Mean 2 2 1 3 3 2 3 2 1 1 2 1 1 1.2 1.1 1.8 3 5 3 3 6 6 4 3 4 2 2 4 3 1.8 3.7 6 6 8 7 7 8 8 4 3 5 5 5 4 1 . 3 1 . 3 1 .8 1 . 5 2 . 5 3 . 5 2.0 1 . 8 1 . 3 1 . 3 1 . 3 i .0 1 .0 3.0 3 . 5 3.5 3 . 5 4 . 3 4.3 4 . 3 2 . 5 2 . 3 2.8 2 . 5 2.8 2.3 2.6 5.8 O 31 Thomson (1981) c i t e d a v e r a g e water t e m p e r a t u r e s of 6 t o 8° C i n t h e w i n t e r and 18-20° C i n t h e summer f o r B a r k l e y Sound. T h i s i s c o m p a r a b l e t o t h e ran g e of v a l u e s r e p o r t e d h e r e : 6.6° C i n J a n u a r y 1983 and 16.0° C i n June 1982. The s a l i n i t y a t e a c h s i t e (25.0 27.6 p p t ) was below p u r e o c e a n i c w a t e r s . S i m i l a r l e v e l s were r e c o r d e d f o r s u r f a c e water a t M a c k e n z i e A n c h o r a g e ( l o c a t e d between H e l b y and D i a n a I s l a n d s ; F i g u r e 2) by B. Emmet ( p e r s . comm.). Water from a d e p t h o f 5 m, however, showed h i g h e r s a l i n i t i e s (28-32 p p t ) . The g r a d i e n t of d e c r e a s i n g s a l i n i t y o b s e r v e d from B e a l e t o H a i n e s / N u d i b r a n c h t o H e l b y / W i z a r d was p r o b a b l y t h e r e s u l t of wind and t i d e m i x i n g of h i g h s a l i n i t y c o a s t a l water w i t h t h e e s t u a r i n e w a t e r s of B a r k l e y Sound ( A u s t i n e t a l . , 1971). The n i t r a t e + n i t r i t e l e v e l s o b s e r v e d were s i m i l a r t o t h o s e r e c o r d e d by L.D. D r u e h l and R.E. Foreman ( p e r s . comm. ) f o r t h e B a m f i e l d a r e a . The s h a r p d e c l i n e i n n i t r a t e c o n c e n t r a t i o n i n A p r i l 1983 c o i n c i d e d w i t h a s p r i n g p h y t o p l a n k t o n bloom. B. Emmet ( p e r s . comm. ) n o t e d an i n c r e a s e i n c h l o r o p h y l l (a+b+c) a t 5 m e t e r s d e p t h i n M a c k e n z i e A n c h o r a g e from 5 pg c h l 1~ 1 i n m i d - F e b r u a r y t o 27 pg c h l l " 1 i n mid-March 1983. Emmet a l s o r e c o r d e d h i g h c h l o r o p h y l l l e v e l s d u r i n g J u l y and Au g u s t 1982 and a f a l l p h y t o p l a n k t o n bloom i n O c t o b e r 1982. However, t h e O c t o b e r 1982 bloom was not p a r a l l e l e d by a d e c l i n e i n se a w a t e r n i t r a t e c o n c e n t r a t i o n ( F i g u r e s 4 a - d ) . 32 Ammonium and p h o s p h a t e l e v e l s i n t h e B a m f i e l d I n l e t a r e g e n e r a l l y low and c o n s t a n t t h r o u g h o u t t h e y e a r (<1.5 u g - a t NH l " 1 ; <1 y g - a t P 0 4 l " 1 ; L.D. D r u e h l , p e r s . comm.). Thus, n i t r a t e i s p r o b a b l y t h e major s o u r c e o f n i t r o g e n f o r m a r i n e p l a n t s . E m p h a sis s h o u l d be g i v e n t o t h e h i g h n i t r a t e c o n c e n t r a t i o n s o b s e r v e d s p o r a d i c a l l y i n June 1983 (>10 u g - a t N C ^ l " 1 ) . These e l e v a t e d c o n c e n t r a t i o n s were p r o b a b l y due t o s t o r m - i n c r e a s e d m i x i n g o f t h e w a t e r c o l u m n . A l t h o u g h s h o r t - l i v e d and i n f r e q u e n t , t h e s e p u l s e s o f n i t r a t e c o u l d have been v e r y i m p o r t a n t t o p l a n t s whose g r o w t h may be n i t r o g e n - l i m i t e d d u r i n g t h e summer. The s u b j e c t i v e r a n k i n g of wave e x p o s u r e i s of " r e l a t i v e i m p o r t a n c e " a t b e s t . The two s h e l t e r e d s i t e s , H a i n e s and H e l b y , showed v e r y l i t t l e s e a s o n a l change i n wave e x p o s u r e , whereas wave a c t i o n was n o t i c e a b l y g r e a t e r d u r i n g t h e f a l l and w i n t e r a t W i z a r d and N u d i b r a n c h . T h i s s u g g e s t s t h a t t h e s i t e s can be d i v i d e d i n t o a t l e a s t two e x p o s u r e g r o u p s . C r a i k (1980) q u a n t i f i e d t h e r e l a t i v e s c o u r i n g (wave a c t i o n p l u s t y p e and c o n c e n t r a t i o n o f s u s p e n d e d s o l i d s ) a t a number of s i t e s i n B a r k l e y Sound. Cape B e a l e was r a n k e d a s most e x p o s e d and H a i n e s I s l a n d v e r y s h e l t e r e d ( c o m p a r a b l e t o a " c a l m " t a n k ) . A H e l b y I s l a n d s i t e ( p r o b a b l y more e x p o s e d t h a n t h e s i t e i n t h i s s t u d y ) was r a n k e d s i g n i f i c a n t l y more e x p o s e d t h a n H a i n e s I s l a n d . F i r s t Beach, c o m p a r a b l e t o 33 W i z a r d I s l e t , was r a n k e d s i g n i f i c a n t l y more e x p o s e d t h e n H e l b y I s l a n d and l e s s e x p o s e d t h a n Cape B e a l e . The o b s e r v a t i o n s of C r a i k ( 1 9 8 0 ) , c o m b i n e d w i t h t h e r a n k i n g o f t h e s t u d y s i t e s u s i n g t h e method o f Baardse.th (1970) and d i s c u s s i o n w i t h o t h e r w o r k e r s a t B a m f i e l d a r e s u p p o r t i v e e v i d e n c e f o r t h e e x p o s u r e r a n k i n g g i v e n t o t h e f i v e s t u d y s i t e s : Cape B e a l e > N u d i b r a n c h Pt > W i z a r d > H e l b y > H a i n e s A m u l t i p l e c o r r e l a t i o n a n a l y s i s (MIDAS) was p e r f o r m e d on a s e t of t h i r t y - s e v e n a b i o t i c f a c t o r s m o n i t o r e d d u r i n g t h e s t u d y . T h e s e i n c l u d e d m o n t h l y means of a i r and water t e m p e r a t u r e , d a i l y l i g h t f l u x , v a r i o u s i n s t a n t a n e o u s and i n t e g r a t e d d i u r n a l l i g h t and t e m p e r a t u r e f a c t o r s ( e . g. i n s t a n t a n e o u s PFD a t 0800h, 1200h, and 1600h), d a i l y v a r i a t i o n s i n a i r and water t e m p e r a t u r e , t o t a l p r e c i p i t a t i o n , and t h e s a l i n i t y , n i t r a t e and wave e x p o s u r e d a t a c o l l e c t e d a t e a c h s i t e . B a s e d on t h e r e s u l t s of t h i s a n a l y s i s , t h e number o f e n v i r o n m e n t a l f a c t o r s t o be u s e d i n f u t u r e c o r r e l a t i o n a n a l y s e s w i t h a l g a l b i o m a s s and p r o d u c t i v i t y has been r e d u c e d t o t h e s i x f a c t o r s p r e s e n t e d i n T a b l e 2 and t h e s a l i n i t y , n i t r a t e , wave e x p o s u r e and a i r e x p o s u r e d a t a f o r e a c h s t u d y s i t e . The o t h e r f i f t e e n f a c t o r s , w h i c h i n v o l v e T a b l e 2 C o r r e l a t i o n m a t r i x f o r s e l e c t e d a b i o t i c e n v i r o n m e n t a l f a c t o r s F 1 F2 F3 F4 F5 F6 F1-monthly mean a i r temperature (°C) 1.0000 0.9151 0.9295 -.7841 0.6047 0.5999 F2-monthly mean water temperature (' C) 1.0000 0.9564 -.9001 0.6990 0.6874 F3-monthly mean d a i l y 1 i ght f 1 ux E i n irr 2 ) 1.0000 -.8913 0.7043 0.7326 F4-monthly t o t a l ra i n f a 11 (mm) 1.0000 .7192 -.6691 F5-monthly mean d a i l y v a r i a t i o n a i r - T C O 1.0000 0.5730 F6-monthly mean d a i l y v a r i a t i o n water-T (' C) 1.0000 For s i g n i f i c a n c e p<0.01, r=0.6411 35 d i u r n a l v a r i a t i o n s i n l i g h t and t e m p e r a t u r e , a r e a d e q u a t e l y r e p r e s e n t e d by t h e i r r e s p e c t i v e m o n t h l y means. S i g n i f i c a n t p o s i t i v e c o r r e l a t i o n s (r=0.9151-0.9564, P<0.01) were f o u n d between t h e m o n t h l y means o f l i g h t , a i r and water t e m p e r a t u r e ( T a b l e 2). T o t a l m o n t h l y r a i n f a l l however, was s i g n i f i c a n t l y i n v e r s e l y c o r r e l a t e d w i t h a l l of th e l i g h t and t e m p e r a t u r e f a c t o r s (r=-0.669l t o -0.9001, P<0.01; T a b l e 2). R a i n f a l l was p o s i t i v e l y c o r r e l a t e d w i t h s e a w a t e r n i t r a t e c o n c e n t r a t i o n a t e a c h s t u d y s i t e (r=0.6439-0.7976, p<0.0l), but was not c o r r e l a t e d w i t h s a l i n i t y . T h i s s u g g e s t s t h a t r a i n f a l l may be a s i g n i f i c a n t s o u r c e of n i t r a t e f o r t h i s s y s t e m , e i t h e r d i r e c t l y o r i n d i r e c t l y ( v i a t e r r e s t r i a l r u n o f f ) . S a l i n i t y a t H a i n e s and N u d i b r a n c h were p o s i t i v e l y c o r r e l a t e d (r=0.8989, p<0.01); l i k e w i s e f o r H e l b y and W i z a r d (r=0.8375, p<0.0l). O n l y one o t h e r p a i r w i s e c o r r e l a t i o n was s i g n i f i c a n t ( H a i n e s and W i z a r d , r=0.6617, p<0.0l), s u g g e s t i n g t h a t t h e s e two s i t e g r o u p s were i n d i f f e r e n t s a l i n i t y r e g i m e s . The d i f f e r e n c e s i n s a l i n i t y were not t h a t l a r g e (25.0 v s 27.6 p p t ) and t h u s may not have been an i m p o r t a n t f a c t o r a f f e c t i n g a l g a l p r o d u c t i v i t y . N i t r a t e l e v e l s a t most s i t e s were s i g n i f i c a n t l y p o s i t i v e l y c o r r e l a t e d (r> 0.81, p<0.0! f o r a l l but t h e 36 H a i n e s / H e l b y c o r r e l a t i o n ; r=0.6055, 0.01 < p < 0.05). Thus, e a c h s i t e was e x p o s e d t o a r e l a t i v l y s i m i l a r n i t r o g e n r e g i m e . O n l y t h e more e x p o s e d s t u d y s i t e s ( W i z a r d and N u d i b r a n c h ) showed s i g n i f i c a n t p o s i t i v e c o r r e l a t i o n s between t h e wave e x p o s u r e r a t i n g s and o t h e r e n v i r o n m e n t a l f a c t o r s . T h i s i s not s u r p r i s i n g , f o r wave e x p o s u r e showed l i t t l e s e a s o n a l v a r i a t i o n a t H a i n e s and H e l b y . In g e n e r a l , wave e x p o s u r e , l i g h t and t e m p e r a t u r e were n e g a t i v e l y c o r r e l a t e d ( W i z a r d minimum e x p o s u r e vs o t h e r s r = -0.54 t o -0.85; N u d i b r a n c h maximum e x p o s u r e vs o t h e r s r = -0.44 t o - 0 . 7 9 ) . S i g n i f i c a n t p o s i t i v e c o r r e l a t i o n s , however, were f o u n d between e x p o s u r e and t o t a l m o n t h l y r a i n f a l l a t W i z a r d and N u d i b r a n c h (r=0.6580-0.7376, p < 0 . 0 l ) . T h e s e c o r r e l a t i o n s s u g g e s t t h a t t h e s u b j e c t i v e r a t i n g of wave e x p o s u r e was f a i r l y a c c u r a t e , as i t c o r r e l a t e d q u i t e w e l l w i t h t h o s e a b i o t i c f a c t o r s u s u a l l y a s s o c i a t e d w i t h w i n t e r c o n d i t i o n s and s t o r m s ( i . e . d e c r e a s e d l i g h t and t e m p e r a t u r e , and i n c r e a s e d r a i n f a l l ) . 37 CHAPTER 3 - BIOMASS OF INTERTIDAL MACROALGAE B a s i c t o any s t u d y o f p r i m a r y p r o d u c t i v i t y i s t h e d e t e r m i n a t i o n o f t h e p l a n t b i o m a s s i n t h e s y s t e m . M a c r o a l g a e show a wide v a r i e t y of complex t h r e e - d i m e n s i o n a l g r o w t h f o r m s . E s t i m a t i n g m a c r o a l g a l a b u d a n c e s u s i n g p e r c e n t c o v e r d a t a o n l y p r o v i d e s i n f o r m a t i o n a b o u t r e l a t i v e a l g a l a b u n d a n c e s , and may be m i s l e a d i n g , a s i t measures a b u n d a n c e s i n o n l y two d i m e n s i o n s ( s e e N e i l l , 1977). In a d d i t i o n , p e r c e n t c o v e r d a t a may show d i f f e r e n t p a t t e r n s t h a n b i o m a s s d a t a ( e . g. Thorn, 1983). C o m p a r i s o n s w i t h o t h e r a r e a s and between s p e c i e s a r e a l s o o n l y p o s s i b l e u s i n g a measure of a b s o l u t e p l a n t abundance, s u c h as b i o m a s s . The e n v i r o n m e n t a l f a c t o r s d i s c u s s e d i n C h a p t e r 2 may a f f e c t b o t h a l g a l p h y s i o l o g y and s t a n d i n g c r o p s ; f a c t o r i n t e r a c t i o n s a r e a l s o t o be e x p e c t e d . F o r example, G e r a r d and Mann (1979) d e m o n s t r a t e d t h e i m p o r t a n c e of w ater m o t i o n on t h e t h a l l u s m o r p h o l o g y o f L a m i n a r i a l o n g i c r u r i s de l a P y l . T h a l l u s m o r p h o l o g y i n t u r n i n f l u e n c e d c o m p e t i t i o n f o r l i g h t , l i m i t i n g p l a n t d e n s i t y a t one s i t e . L a m i n a r i a  l o n g i c r u r i s w i t h d i f f e r i n g m o r p h o l o g i e s a l s o showed d i f f e r e n t s e a s o n a l g r o w t h p a t t e r n s and a b i l i t i e s t o t a k e up n i t r o g e n . The end r e s u l t was t h a t L ^ l o n g i c r u r i s f r o m a s h e l t e r e d s i t e was more p r o d u c t i v e t h a n p l a n t s f r o m a more e x p o s e d s i t e . W h i l e i n c r e a s e d w a t e r m o t i o n may enhance 38 r a t e s of p h o t o s y n t h e s i s and n u t r i e n t u p t a k e ( W h e e l e r , 1980; P a r k e r , 1981; G e r a r d , 1982), a l g a l s t a n d i n g c r o p may be l i m i t e d by t h e same water m o t i o n ( G e r a r d and Mann, 1979; Mann e t a l . , 1980). M u l t i p l e r e g r e s s i o n a n a l y s e s i n v o l v i n g e n v i r o n m e n t a l f a c t o r s , a l g a l s t a n d i n g c r o p , a l g a l p h y s i o l o g y , and a l g a l p r o d u c t i v i t y may p r o d u c e f u r t h e r i n s i g h t i n t o t h e e c o l o g y of i n t e r t i d a l m a c r o a l g a e . T h e r e have been r e l a t i v e l y few s t u d i e s w h i c h have q u a n t i f i e d t h e bi o m a s s of i n t e r t i d a l m a c r o a l g a e , and o n l y some of t h e s e have l o o k e d a t s e a s o n a l d i f f e r e n c e s i n any d e t a i l ( B l i n k s , 1955; B r i n k h u i s , 1976, 1977; N e i l l , 1 977; Munda and Markham, 1982; Chock and M a t h i e s o n , 1983; Thorn, 1983). Most s t u d i e s o f i n t e r t i d a l m a c r o a l g a e have u s e d p e r c e n t a g e c o v e r as an e s t i m a t e of a l g a l a b u n dance. T h i s c h a p t e r p r e s e n t s t h e b a s i c d a t a on i n t e r t i d a l m a c r o a l g a l biomass and community s t r u c t u r e w h i c h i s e s s e n t i a l t o a d d r e s s i n g t h e f i v e p r o b l e m s p r e s e n t e d i n C h a p t e r 1. M u l t i p l e r e g r e s s i o n a n a l y s e s a r e a l s o p e r f o r m e d f o r a l g a l s t a n d i n g c r o p and t h e e n v i r o n m e n t a l f a c t o r s d i s c u s s e d i n C h a p t e r 2. 39 Methods and M a t e r i a l s T h r e e p a r a l l e l t r a n s e c t s , e x t e n d i n g from t h e upper t o t h e l o w e r i n t e r t i d a l , were e s t a b l i s h e d a t e a c h of t h e s t u d y s i t e s ( n o t e : o n l y one t r a n s e c t was e s t a b l i s h e d a t B e a l e ; t h e d a t a c o l l e c t e d a t B e a l e w i l l be p r e s e n t e d i n C h a p t e r 5 ) . E a c h t r a n s e c t was two m e t e r s (2m) wide and s e p a r a t e d from n e i g h b o r i n g t r a n s e c t s by a t l e a s t one meter (1m). T h r e e r e p r e s e n t a t i v e i n t e r t i d a l t r a n s e c t s were u s e d a t e a c h s i t e so as t o a c c o u n t f o r t h e l a r g e amount of s m a l l - s c a l e h o r i z o n t a l v a r i a b i l i t y i n s p e c i e s d i s t r i b u t i o n s and a b u ndances n o t e d by o t h e r w o r k e r s ( J o n e s e t a l . , 1979; Underwood, 1981). E a c h t r a n s e c t was d i v i d e d v e r t i c a l l y i n t o t h r e e z o n e s . At H a i n e s , H e l b y and W i z a r d , Zone I was d o m i n a t e d by F u c u s  d i s t i c h u s L., Zone II by F\_ d i s t i c h u s w i t h some s e c o n d a r y s p e c i e s , and Zone I I I by a s e r i e s of spring/summer a n n u a l s . Zones I and II a r e e s s e n t i a l l y e q u i v a l e n t t o t h e Main F u c u s Z o n e of S t e p h e n s o n and S t e p h e n s o n ( 1 9 6 1 a ) , w i t h Zone I I I s i m i l a r t o t h e i r " B e a r d Zone" w i t h " F u c u s O u t l i e r s " . At N u d i b r a n c h , Zone I was d o m i n a t e d by F ^ d i s t i c h u s and P e l v e t i o p s i s 1 i m i t a t a G a r d n . , Zone I I by an " a l g a l t u r f " c o n s i s t i n g of a r e l a t i v e l y l a r g e number of p a t c h i l y d i s t r i b u t e d s p e c i e s , and Zone I I I by H e d o p h y l l u m s e s s i l e 40 (C. Ag.) S e t c h e l l . The a l g a l community a t N u d i b r a n c h seemed s i m i l a r t o t h a t o f "Rocky S h o r e s Near V i c t o r i a " d e s c r i b e d by S t e p h e n s o n and S t e p h e n s o n ( 1 9 6 1 b ) , e x c e p t t h a t L e a t h e s i a  d i f f o r m i s ( L . ) A r e s c h . was r a r e a t N u d i b r a n c h . T h i s d i v i s i o n of t h e i n t e r t i d a l i n t o z o n e s b a s e d on s p e c i e s d i s t r i b u t i o n s has been done by o t h e r w o r k e r s , and i s p e r h a p s t h e b e s t method f o r d i v i d i n g t h e i n t e r t i d a l i n t o m e a n i n g f u l v e r t i c a l u n i t s ( R i g g and M i l l e r , 1949; S t e p h e n s o n and S t e p h e n s o n , 1949; N e i l l , 1977; Hardwick-Witman and M a t h i e s o n , 1983). T i d a l h e i g h t s a l o n g e a c h t r a n s e c t were d e t e r m i n e d u s i n g a s u r v e y o r ' s l e v e l and s t a d i a r o d , w i t h r e f e r e n c e t o p r e d i c t e d t i d a l h e i g h t s f o r B a m f i e l d ( O c e a n o g r a p h i c I n s t i t u t e , Sydney, B . C . ) . F i g u r e s 5a-d a r e s c h e m a t i c d i a g r a m s of t h e t r a n s e c t s a t e a c h s i t e , s howing t h e t i d a l h e i g h t s , z o n e s , e t c . T a b l e 3 p r e s e n t s a summary o f t h e p e r c e n t t i m e e a c h zone a t e a c h s i t e was e x p o s e d t o a i r . At b i - w e e k l y i n t e r v a l s ( m o n t h l y i n t e r v a l s d u r i n g t h e w i n t e r ) f i v e t o s e v e n 25 x 25 cm (0.0625 m 2) randomly c h o s e n q u a d r a t s were sampled from e a c h zone of one of t h e t r a n s e c t s a t e a c h s i t e . The t r a n s e c t s were v i s i t e d i n a s e t s e q u e n c e so t h a t o v e r a s i x - w e e k p e r i o d , t h e t h r e e t r a n s e c t s a t e a c h s i t e were s a m p l e d . E a c h s i x - w e e k p e r i o d has been t r e a t e d a s a "sample month". T a b l e 4 l i s t s t h e r e a l t i m e s a m p l i n g i n t e r v a l f o r e a c h "sample month". No q u a d r a t a r e a was s a m p l e d more t h a n once d u r i n g t h e c o u r s e o f t h e s t u d y . Figure 5 General diagrams of the i n t e r t i d a l transects established at each study s i t e . T i d a l heights are i n meters above lower low water. A) Haines B) Helby C) Wizard D) Nudibranch C h a r a c t e r i s t i c Species Fd = Fucus d i s t i c h u s C l = Cladophora spp. Ld = Leathesia d i f f o r m i s Cv = C o r a l l i n a V a n c o u v e r i e n s i s Cw = Cryptosiphonia woodii PI = P e l v e t i o p s i s l i m i t a t a Hs = Hedophyllum s e s s i l e 42 A - H a i n e s » Cw | i r " 1 1 r 4 12 2 0 H o r i z o n t a l D i s t a n o e ( m ) C- W i s a r d I I 6 IO H o r i z o n t a l D i s t a n c e ( m ) T a b l e 3. Per cent t ime exposed to a i r f o r each zone and s tudy s i t e f o r s e l e c t e d months SITE : ZONE : TIDAL HT* MONTH 1982 : June October 1983: Feb rua ry June 1982 T o t a l HAINES HELBY WIZARD NUDIBRANCH I II III I II III I II III I II I I I .80 1.90 0 .90 2.40 1.80 0.70 2.40 1.40 0 .80 2.80 2.00 1.20 86 50 78 41 12 10 69 46 60 39 69 29 10 60 26 86 53 78 40 2 1 18 68 32 86 48 11 50 29 68 42 50 14 68 25 68 34 86 51 19 81 44 10 65 41 65 26 8 81 48 18 Note : * meters above lower low water ; h e i g h t s a re the lowest v e r t i c a l e x t e n s i o n of the zone T a b l e 4. S a m p l i n g i n t e r v a l s f o r e a c h s i x - w e e k o r two-month "sample month". 45 "SAMPLE MONTH" 1982: June August September November 1983: J a n u a r y March Apr i 1 May June August DATES SAMPLES COLLECTED 6 June - 9 J u l y 18 J u l y - 22 August 31 A u g u s t - 2 O c t o b e r 13 O c t o b e r - 13 November 10 December - 23 J a n u a r y 5 F e b r u a r y - 5 March 18 March - 19 A p r i l 27 A p r i l - 31 May 10 June - 14 J u l y 22 J u l y - 27 A u g u s t 46 A l l the macroalgae were co l l e c t e d from each quadrat, stored in separate p l a s t i c bags, and returned to the Bamfield Marine Station for analysis. Fresh biomass of each a l g a l species in each quadrat was measured to the nearest 0.1 g after submergence for 0.5 to 1.0 h and removal of surface water by b r i s k l y shaking the plants. Samples of each species were then dried at 105°C in a gravity convection oven for at least 24h and freshrdry weight ratios were calculated. Unless otherwise noted, a l l biomass values are expressed in terms of dry weight. The biomass data were analyzed using analysis of variance techniques (UBC*GENLIN) and multiple regression analyses (MIDAS). Those quadrats landing on bare rock, in tide pools, or containing excessively large amounts of algae were not used in these analyses. Tide pools generally contained a l g a l species d i f f e r e n t from those on the emergent rock (see also Lubchenco, 1978), while areas of bare rock were usually found only at the the top of the transects and above the Fucus zone. Occasionally, quadrats were coll e c t e d which contained 800-1000 g dry wt of plant material ( i . e . up 16 kg dry wt i r r 2 ) ; these samples were not used in the analysis because they were obviously not representative of the a l g a l assemblage. The UBC*GENLIN program was used because i t can handle missing data resulting from unsuitable 47 q u a d r a t s o r t r a n s e c t s not b e i n g sampled due t o weather c o n d i t i o n s , e t c . R e s u l t s A t o t a l o f s i x t y (60) s p e c i e s o f m a c r o a l g a e were f o u n d d u r i n g t h e s t u d y . The s p e c i e s c a n g e n e r a l l y be p l a c e d i n t o one of f o u r g r o u p s : 1) abundant p e r e n n i a l s , 2) abundant a n n u a l s , 3) common s e c o n d a r y s p e c i e s , and 4) r a r e s p e c i e s . T a b l e 5 l i s t s t h e s p e c i e s c o l l e c t e d ; t h e a b u n d a n c e s and d i s t r i b u t i o n of e a c h of t h e s p e c i e s i n g r o u p s 1-3 w i l l be d i s c u s s e d i n v a r i o u s d e g r e e s of d e t a i l . T o t a l m a c r o a l g a l s t a n d i n g c r o p d a t a f o r e a c h zone o f e a c h s i t e , a v e r a g e d o v e r t h e e n t i r e f i f t e e n (15) month s t u d y p e r i o d , a r e p r e s e n t e d i n T a b l e 6. An a n a l y s i s of v a r i a n c e (ANOVA) o v e r s i t e , z one, and month was p e r f o r m e d on t h i s d a t a ( T a b l e 7 ) . The o n l y n o n - s i g n i f i c a n t d i f f e r e n c e s were f o u n d f o r t h e Zone and t h r e e - w a y i n t e r a c t i o n t e r m s . U s i n g Student-Newman-Keuls (S-N-K) m u l t i p l e r a n g e t e s t s ( p < 0 . 0 l ) , t h e s i t e s c a n be d i v i d e d i n t o t h r e e g r o u p s b a s e d on a l g a l s t a n d i n g c r o p : H a i n e s > H e l b y , W i z a r d > N u d i b r a n c h 48 Table 5. L i s t of i n t e r t i d a l macroalgae  coll e c t e d during the study. Abundant perennial species: Fucus distichus L. Hedophyllum s e s s i l e (C. Ag.) Setch. Abundant annual species: Cryptosiphonia woodi i ( J . Ag.) J . Ag. Leathesia difformis TL.) Aresch. Common secondary/fugitive species: Ceramium pac i f icum (Coll.) Kyi. Cladophora columbiana C o l l . Cladophora sericea (Huds.) Kutz. Cladophora stimpsoni i Harv. Corallina Vancouveriens is Yendo ** Endocladia muricata (Post. & Rupr.) J . Ag. * Halosaccion americanum Lee * Iridaea cornucopiae Post. & Rupr. Microcladia borealis Rupr. * Neorhodomela l a r i x ("Turn.) Maruda * Pelvet iopsis 1imi tata Gardn. Polysiphonia brodiaei (Dillw.) Spreng. Polysiphonia hendryi Gardn. * Ulva fenestrata Post. & Rupr. * Rare species: Phaeophyta: Alar ia sp. Analipus japonicus (Harv.) Wynne Colpomenia bullosa (Saund.) Yamada Costaria costata (C. Ag.) Saunders Desmerestia v i r i d i s (Mull.) Lamour. Eqregia menziessi i (Turn.) Aresch. Macrocystis i n t e q r i f o l i a Bory Postelsia palmaeformis Rupr. Sargassum muticum (Yendo) Fensh. Scytosiphon lomentaria (Lyngb.) J . Ag. Soranthera ulvoidea Post. & Rupr. 49 Chlorophyta: Codium f r a g i l e (Sur.) Harv. Enteromorpha sp. Rhodophyta: A h n f e l t i a g i g a r t i n o i d e s J . Ag. B o s s i e l l a o r b i g n i a n a (Dec.) S i l v a C a l l i t h a m n i o n pikeanum Harv. * Ceramium eatonianum ( F a r l . ) DeToni C o r a l l i n a o f f i c i n a l i s L. Cryptonemia obovata J . Ag. Cryptonemia o v a f o l i a K y i . Cumogloea andersoni i ( F a r l . ) S. & G. * Gastroclonium s u b a r t i c u l a t u m (Turn.) Kutz. = G^ c o u l t e r i (Harv.) K y i . Gelidium sp. G i g a r t i n a corymbi f e r a (Kutz.) J . Ag. G i g a r t i n a p a p i l l a t a (C. Ag.) J . Ag. * G r a t e l o u p i a s e t c h e l l i i K y i . Gymnogongrus p l a t y p h y l l u s Gardn. Hymenena sp. I r i d a e a f l a c e ida (S. & G.) S i l v a I r i d a e a heterocarpa Post. & Rupr. * Lomentaria hakodatensis Yendo M i c r o c l a d i a c o u l t e r i Harv. Nemalion helminthoides ( V e i l . ) B a t t . Odonthalia f l o c c o s a ("Isp. ) F a l k . * Odonthalia w a s h i n g t o n i e n s i s K y i . * Plocarnium sp. Porphyra sp. P r i o n i t i s l a n c e o l a t a (Harv.) Harv. P r i o n i t i s l y a l l i i Harv. * P t e r o s i p h o n i a b i p i n n a t a (Post. & Rupr.) F a l k . Rhodoglossum af f ine (Harv.) K y i . Rhodomela l y c o p o d i o i d e s (L.) C. Ag. Schizymenia sp. / " Note: * f u g i t i v e s p e c i e s * * o b l i g a t e understory s p e c i e s as per Dayton (1975) T a b l e 6 Combined ( t o t a l ) a l g a l s t a n d i n g c r o p [g d ry wt m-2; ( s t d . d e v . ) ] f o r each zone at the s tudy s i t e s averaged over the e n t i r e s tudy p e r i o d . S ITE: HAINES HELBY WIZARD NUDIBRANCH ZONE I 1019 .6 433 . 2 509 .0 162 . 2 (567 .7) (386 .0) (394 .2) ( 166 .0) II 640. .0 625 . 7 600 .0 288 .6 (558 . .0) (402 .4) (429 . 2) (210. .9) II I 288 . 5 239 .6 410. .2 532 . 5 (330. 1) (236 . . 1) (338 . 2) (359 . 4) O T a b l e 7 A n a l y s i s of v a r i a n c e f o r combined a l g a l s t a n d i n g c r o p (g d r y wt m-2) at each s tudy s i t e . SOURCE SUM OF SQUARES DF MEAN SQUARE F-RATIO •PROBABILITY Si te Zone Si t e *Zone Month S i te*Month Zone*Month S*Z*M Res i dua1 T o t a l 1 . 1361E+05 74030 1.7686E+05 1.6386E+05 36323 25037 36658 6.7048E+05 ' 1.2430E+06 3 2 6 9 25 16 46 1417 1524 37869 37015 29476 18207 1452.9 1564 . 8 796.91 473 . 17 80.034 1.2558 62 . 295 38.479 3.0706 3.3070 1.6842 0.00000 * * 0.35029 ns 0.00000 * * 0.00000 * * 0.00000 * * 0.00001 * * 0.00309 ns Note: Zone mean square t e s t e d a g a i n s t S i te+Zone mean square ( f i x e d - e f f e c t s model) 52 The months can a l s o be d i v i d e d i n t o t h r e e g r o u p s : summer 1982 > f a l l 1982,spring/summer 1983 > w i n t e r 1982-83 F u r t h e r a n a l y s i s of t h e two-way i n t e r a c t i o n t e r m s was done u s i n g t h e r e s p e c t i v e one-way ANOVAs. A t e a c h s i t e , t h e p a t t e r n of a l g a l b i o m a s s d i s t r i b u t i o n o v e r z o n e s d i f f e r e d . B ased on S-N-K a n a l y s i s , t h e f o l l o w i n g p a t t e r n s were f o u n d : H a i n e s : Zone I > Zone I I > Zone I I I H e l b y : Zone II > Zone I > Zone I I I W i z a r d : Zone I , I I > Zone I , I I I N u d i b r a n c h : Zone I I I > Zone I I > Zone I L i k e w i s e , e a c h zone showed d i f f e r e n t s t a n d i n g c r o p l e v e l s o v e r t i m e . Zone I was d i v i d e d i n t o two g r o u p s by S-N-K a n a l y s i s ( p < 0 . 0 l ) , however s e v e n o f t h e t e n "sample months" were p r e s e n t i n b o t h g r o u p s ( i . e. t h e g r o u p s were v e r y homogeneous). The d a t a f o r Zone II were s e g r e g a t e d i n t o f i v e g r o u p s , w h i c h more g e n e r a l l y c an be r e d u c e d t o t h r e e g r o u p s : summer 1982,1983 > f a l l 1 9 8 2 , s p r i n g 1983 > w i n t e r 1982-83 Fo r Zone I I I , t h e summer 1982 a l g a l s t a n d i n g c r o p was g e n e r a l l y g r e a t e r t h a n t h a t of t h e r e s t of t h e s t u d y p e r i o d . 53 A t H a i n e s and N u d i b r a n c h , t h e r e was l i t t l e change i n a l g a l s t a n d i n g c r o p ; however, i t s h o u l d be n o t e d t h a t t h e r e were no w i n t e r 1982-1983 d a t a f o r N u d i b r a n c h . A t H e l b y and W i z a r d , t h e summer a l g a l s t a n d i n g c r o p was g r e a t e r t h a n t h a t of t h e o t h e r months. T h e r e was l i t t l e d i f f e r e n t i a l g r o u p i n g of t h e f a l l 1982 t o s p r i n g 1983 d a t a a t t h e s e two s i t e s (S-N-K a n a l y s i s , p<0.01). A m u l t i p l e r e g r e s s i o n a n a l y s i s ( b a c k w a r d , s t e p w i s e ; MIDAS) o f t o t a l a l g a l s t a n d i n g c r o p (g d r y wt irr 2) on t e n e n v i r o n m e n t a l f a c t o r s was p e r f o r m e d . R e s u l t s o f t h i s a n a l y s i s f o r a) c o n t e m p o r a n e o u s measurements of t h e f a c t o r s and b) t h e p r e v i o u s ( a n t e c e d e n t ) months v a l u e s f o r t h e f a c t o r s , a r e p r e s e n t e d i n T a b l e 8. The MULTIPLE-R and p a r t i a l c o r r e l a t i o n c o e f f i c i e n t s f o r t h e r e g r e s s i o n e q u a t i o n s a r e q u i t e low and t h e e q u a t i o n s a c c o u n t f o r o n l y 23.8-33.9% o f t h e o b s e r v e d v a r i a n c e i n t o t a l a l g a l s t a n d i n g c r o p . Water t e m p e r a t u r e , p e r c e n t t i m e e x p o s e d t o a i r , and th e minimum + maximum wave e x p o s u r e r a t i n g were p r e s e n t i n b o t h e q u a t i o n s . A) Abundant P e r e n n i a l S p e c i e s F u c u s d i s t i c h u s s t a n d i n g c r o p was g r e a t e s t i n t h e h i g h e r z o n e s a t e a c h s i t e . S t a n d i n g c r o p d a t a f o r Zones I and I I a r e p r e s e n t e d i n F i g u r e s 6a-d. F u c u s d i s t i c h u s was a l s o p r e s e n t i n Zone i l l o f t h e s h e l t e r e d s i t e s b u t i t s T a b l e 8. M u l t i p l e r e g r e s s i o n a n a l y s e s of t o t a l a l g a l s t a n d i n g c r o p (g d r y wt m-2) a t a l l s i t e s and zones on s e l e c t e d a b i o t i c env i r onmenta l f a c t o r s . a) Contemporaneous var i a b l e s SOURCE DF SUM OF SOUARES Regress i on E r r o r T o t a l 5 102 107 3.5122E+06 6 . 8458E+06 1.0358E+07 MEAN SOUARE 7.0245E+05 671 16 F-RATIO 10.466 PROBABILITY 0.0000 * * MULTIPLE R = 0.58231 SE = 259.07 p a r t i a l c o r r e l a t i o n c o e f f i c i e n t s : PFD (uEIN m-2 day -1 ) Water Temperature ( 'C ) Ra i n f a l 1 (mm) Min + Max Wave Exposure Time Exposed to A i r (%) EQUATION V i l l a : - 0 . .34465 (P =0. .0003) 0. 19571 (P =0. .0465) - 0 . 21076 (P =0. .0317) - 0 . 40426 (P = 0. .0000) 0. 32772 (P =0. .0007) Stand i ng Crop = 578 .8 - 28.4(PFD) + 61 .6 (H20-T ) - 0. ,5(RAIN) - 54 .0(WAVE EXP) + b) Antecedent v a r i a b l e s SOURCE DF SUM OF SQUARES MEAN SQUARE F-RATIO PROBABILITYY Regress i on 3 1 . . 9968E+06 6.6560E+05 9.5989 0.OOOO * * E r r o r 92 6 . ,3794E+o6 6934 1 T o t a l 95 8 . 3762E+06 MULTIPLE R = 0.48825 SE = 263.33 p a r t i a l c o r r e l a t i o n c o e f f i c i e n t s : Water Temperature (*C) Min + Max Wave Exposure Time Exposed to A i r (%) 0.20626 (P=0.0461) -0.33691 (P=0.0009) 0.28625 (P=0.0052) EQUATION V H I b : S t a n d i n g Crop = 265.59 + 21.0(H2D-T) - 47.2(WAVE EXP) + 2.9(AIR EXP) 55 d i s t r i b u t i o n was p a t c h y and b i o m a s s much l o w e r . A t e a c h s i t e , F_^ d i s t i c h u s s t a n d i n g c r o p showed s e a s o n a l d e c r e a s e s d u r i n g t h e w i n t e r months ( F i g u r e s 6 a - d ) . The r e s u l t s of a m u l t i - w a y ANOVA of F ^ d i s t i c h u s b i o m a s s o v e r s i t e , zone ( o n l y Zones I and I I ) , and t i m e a r e p r e s e n t e d i n T a b l e 9. As i n t h e ANOVA f o r t o t a l a l g a l b i o m a s s , t h e o n l y n o n - s i g n i f i c a n t terms were t h e Zone and thr e e - w a y i n t e r a c t i o n . T h i s i s n o t s u r p r i s i n g , a s most of th e a l g a l b i o m a s s a t t h e t h r e e s h e l t e r e d s i t e s was F. d i s t i c h u s . F u c u s d i s t i c h u s s t a n d i n g c r o p d e c r e a s e d w i t h i n c r e a s i n g wave e x p o s u r e . A v e r a g e d o v e r z o n e s and t i m e , t h e f o l l o w i n g p a t t e r n was r e s o l v e d by S-N-K a n a l y s i s ( p < 0 . 0 l ; g d r y wt m~ 2 ) : H a i n e s (820.5) > H e l b y ( 5 3 2 . 1 ) , W i z a r d (527.5) > > N u d i b r a n c h (65.8) I t s h o u l d a l s o be n o t e d t h a t t h e p l a n t s a t N u d i b r a n c h were much s m a l l e r i n s i z e a s compared w i t h t h o s e a t t h e s h e l t e r e d s i t e s and d i d not form an e x t e n s i v e c a n o p y . S e a s o n a l l y , t h e F_;_ d i s t i c h u s b i o m a s s d a t a c a n be d i v i d e d i n t o t h r e e g e n e r a l g r o u p s u s i n g S-N-K a n a l y s i s (p<0.01>: summer 1982 > spring/summer 1983 > f a l l 1 9 8 2 , w i n t e r 1982-83 Figure 6 Mean standing crop ( + or - one standard deviation) of Fucus d i s t i c h u s i n Zones I and II at each study s i t e for each "sample month". A) Haines B) Helby C) Wizard D) Nudibranch (Zone 1 only) • = Zone I • = Zone II Month 1 6 0 0 1 2 0 0 -•o 8 0 0 O) CO 3 o a u. 4 0 0 -88 J n i l l n i } r -I 1 1 I A S N 8 3 J a M A p M y J n M o n t h 00 -1 1 1 r — — i 1 1 1 1 r Jn A S N 8 3 Ja M Ap My Jn A Month D - Nudibranch ^ - i 1 1 1—ir> 1 i 1 1 r Jn A S N Ja M Ap My Jn A Month o T a b l e 9 A n a l y s i s of v a r i a n c e of Fucus d i s t i chus s t a n d i n g c r o p (g d r y wt m-2) in Zones I and II at each s tudy s i t e . SOURCE SUM OF SQUARES DF MEAN SQUARE F-RATIO PROBABILIT' Si t e 8 .4501E+07 3 2 .8167E+07 207.64 0 .0 * * Zone 1 .9192E+06 1 1 .9192E+06 0.4547 0. 54844ns S i t e *Zone 1 .2S64E+07 3 4 . 2212E+06 31.118 0 .00000* * Month 3. .2852E+07 9 3 .6502E+06 29.908 0 .00000* * S i te*Month 1 . .0136E+07 25 4 . 0545E+05 2 .9889 0 .00000* * Zone*Month 4 . 1359E+06 9 4 . 5945E+05 3.3877 0 .00000* * S*Z*M 5 . 9770E+06 25 2 . 3908E+05 1.7624 0.01199ns Res i dua1 1 . .3496E+08 995 1 . .3565E+05 T o t a l 2 . 7418E+08 1070 Note: Zone mean square t e s t e d a g a i n s t S i t e * Z o n e mean square ( f i x e d e f f e c t s model) 62 The l o w e r d i s t i c h u s s t a n d i n g c r o p d u r i n g t h e summer 1983 as compared w i t h t h e summer 1982 i s e v i d e n t i n F i g u r e s 6a-d. A n a l y s i s o f t h e Zone*Month i n t e r a c t i o n showed t h a t t h e s e a s o n a l b i o m a s s d i s t r i b u t i o n was more homogeneous i n Zone I t h a n i n Zone I I . T h i s was t h e r e s u l t o f w i n t e r d e c r e a s e s i n F. d i s t i c h u s s t a n d i n g c r o p i n Zone I I a t e a c h s i t e b u t no d e c l i n e i n t h e w i n t e r F_;_ d i s t i c h u s s t a n d i n g c r o p i n Zone I a t H a i n e s ( s e e F i g u r e 6 a ) . S i g n i f i c a n t s e a s o n a l c h a n g e s i n F\ d i s t i c h u s b i o m a s s were o b s e r v e d a t e a c h s i t e ; however, t h e d e g r e e of change v a r i e d a t e a c h s i t e . T h e r e was r e l a t i v e l y l i t t l e change a t H a i n e s and N u d i b r a n c h , b ut t h e s t a n d i n g c r o p was a l w a y s l a r g e a t H a i n e s and s m a l l a t N u d i b r a n c h . At H e l b y and W i z a r d , t h e summer 1982 d a t a were s e p a r a t e d i n t o a d i s t i n c t g r o u p by S-N-K a n a l y s i s ( p < 0 . 0 O . The f a l l 1982, w i n t e r 1982-83, and spring/summer 1983 p e r i o d s were l e s s d i s t i n c t l y s e g r e g a t e d . A n a l y s i s of t h e Z o n e * S i t e i n t e r a c t i o n showed s i g n i f i c a n t d i f f e r e n c e s between Zones I and II a t e v e r y s i t e b u t W i z a r d (F=1.1684 1,300df; P=0.28061ns). At H a i n e s and N u d i b r a n c h , Fj_ d i s t i c h u s s t a n d i n g c r o p i n Zone I was g r e a t e r t h a n t h a t i n Zone I I ; t h e r e v e r s e was t r u e a t H e l b y . A v e r a g e d o v e r t h e e n t i r e s t u d y p e r i o d , t h e s t a n d i n g c r o p s i n Zone I I I a t e a c h s i t e were: H a i n e s , 90.1 g d r y wt i r r 2 , H e l b y , 159.4 g d r y wt i r r 2 , W i z a r d , 245.0 g d r y wt n r 2 , N u d i b r a n c h , 0 g d r y wt i r r 2 . In e a c h c a s e , t h e s t a n d a r d 63 d e v i a t i o n e x c e e d e d t h e mean s t a n d i n g c r o p . F u c u s d i s t i c h u s b i o m a s s i n Zone I I I was low e r t h a n t h a t i n Zones I and I I . A n a l y s i s o f v a r i a n c e o f t h e Zone I I I d a t a o v e r s i t e and month showed s i g n i f i c a n t s i t e and month d i f f e r e n c e s , but t h e S i t e * M o n t h i n t e r a c t i o n was n o t . s i g n i f i c a n t (F=1.8516 14,334df; P=0.03073ns). S-N-K a n a l y s e s (p<0.0l) o v e r t i m e p r o d u c e d two r e l a t i v e l y s i m i l a r g r o u p s — t h u s t h e c h a n g e s i n bi o m a s s o v e r t i m e p r o b a b l y a r e not t r u e s i g n i f i c a n t d i f f e r e n c e s . However, t h e mean b i o m a s s d u r i n g t h e summer months (200-285 g d r y wt n r 2 ) was much g r e a t e r t h a n t h a t d u r i n g t h e o t h e r months (70-140 g d r y wt i r r 2 ) . S-N-K a n a l y s i s ( p < 0 . 0 l ) o v e r s i t e p r o d u c e d two g r o u p s : W i z a r d , H e l b y > H e l b y , H a i n e s S t a n d i n g c r o p s a t e a c h s i t e were a l s o h i g h l y v a r i a b l e , so t h e s t a t i s t i c a l s i g n i f i c a n c e o f t h e b e t w e e n - s i t e d i f f e r e n c e s i s q u e s t i o n a b l e . R e s u l t s o f t h e m u l t i p l e r e g r e s s i o n a n a l y s i s of F. d i s t i c h u s s t a n d i n g c r o p on s e l e c t e d a b i o t i c e n v i r o n m e n t a l f a c t o r s a r e p r e s e n t e d i n T a b l e 10. B o t h wave e x p o s u r e and a i r e x p o s u r e were s i g n i f i c a n t , but t h e c o e f f i c i e n t s f o r e a c h were a l m o s t t w i c e t h o s e f o r t h e s e f a c t o r s i n t h e t o t a l a l g a l s t a n d i n g c r o p r e g r e s s i o n e q u a t i o n s ( T a b l e s 8 and 10). The MULTIPLE-R and p a r t i a l c o r r e l a t i o n c o e f f i c i e n t s were h i g h e r i n t h e F ^ d i s t i c h u s r e g r e s s i o n s , b u t t h e e q u a t i o n s s t i l l 64 a c c o u n t e d f o r l e s s t h a n f i f t y p e r c e n t (50%) o f t h e v a r i a n c e i n ¥\_ d i s t i c h u s s t a n d i n g c r o p . To e l i m i n a t e some of t h e " n o i s e " c a u s e d by t h e v a r i a b i l i t y i n d i s t i c h u s s t a n d i n g c r o p t h r o u g h o u t t h e s t u d y a r e a , and t h u s p e r h a p s o b t a i n r e g r e s s i o n e q u a t i o n s w i t h l a r g e r c o r r e l a t i o n c o e f f i c i e n t s w h i c h would t h e n have some p r e d i c t i v e v a l u e , F\_ d i s t i c h u s s t a n d i n g c r o p i n e a c h zone was s u b j e c t e d t o a s e p a r a t e r e g r e s s i o n a n a l y s i s ( T a b l e 11). R e g r e s s i o n e q u a t i o n s w i t h h i g h e r c o r r e l a t i o n c o e f f i c i e n t s were o b t a i n e d . However, t h e f a c t o r s p r e s e n t i n t h e r e g r e s s i o n e q u a t i o n s , and t h e m a g n i t u d e s of t h e i r c o e f f i c i e n t s , d i f f e r e d g r e a t l y . Mean m o n t h l y b i o m a s s of H e d o p h y l l u m s e s s i l e i n Zone I I I a t N u d i b r a n c h i s p r e s e n t e d i n F i g u r e 7. A one-way ANOVA ( s t a n d i n g c r o p by month) was n o t s i g n i f i c a n t (F=1.8110 7,90df; P=0.09470ns). Thus, t h e r e were no s i g n i f i c a n t s e a s o n a l v a r i a t i o n s i n t h e s t a n d i n g c r o p o f H_j_ s e s s i l e a t N u d i b r a n c h . I t s h o u l d be n o t e d , however, t h a t t h e r e a r e no d a t a f o r December 1982 t o M a r c h 1983. T h i s i s t h e " r o u g h e s t " t i m e o f y e a r , i n t e r m s of wave a c t i o n , a t N u d i b r a n c h ( T a b l e 1 ) . T hus, one m i g h t e x p e c t a d e c r e a s e i n 1L s e s s i l e b i omass d u r i n g t h e s e months, w h i c h m i g h t t h e n r e s u l t i n a s t a t i s t i c a l l y s i g n i f i c a n t s e a s o n a l change i n s t a n d i n g c r o p . E v i d e n c e t h a t t h e w i n t e r of 1982-83 d i d i n d e e d r e d u c e H. s e s s i l e b i o m a s s a t N u d i b r a n c h comes from t h e g r o w t h Figure 7 Mean standing crop (• + & - 1 standard deviation) of Hedophyllum s e s s i l e i n Zone III at Nudibranch f or each "sample month." 1400 E t 1000-T3 01 Month T a b l e 10. M u l t i p l e r e g r e s s i o n a n a l y s e s of Fucus d i s t i chus s t a n d i n g c r o p (g d r y wt m-2) at a l l s i t e s and zones on s e l e c t e d a b i o t i c e n v i r o n m e n t a l f a c t o r s . Contemporaneous var i a b l e s SOURCE DF SUM OF SOUARES R e g r e s s i o n 4 6.9425E+06 E r r o r 103 6.8640E+06 T o t a l 107 1.3807E+07 MULTIPLE R = 0.70911 SE = 258.15 p a r t i a l c o r r e l a t i o n c o e f f i c i e n t s : PFD (uE i n m-2 day -1 ) Water Temperature (*C) Min + Max Wave Exposure Time Exposed to A i r (%) EQUATION Xa: MEAN SQUARE 1.7356E+06 66641 F-RATIO 26 .045 -0.29984 (P=0.0019) 0.30627 (P=0.0015) -0.60717 (P=0.0000) 0.53581 (P=0.0000) PROBABILITY 0.0000 * * S t a n d i n g Crop = -3 .3788 - 22.8(PFD) + 80.3 (H20-T) - 93.2 (WAVE EXP) + 6.0(AIR EXP) An tecedent v a r i a b l e s SOURCE Regress i on E r r o r T o t a l DF 3 92 95 SUM OF SQUARES 5.3205E+06 5.6725e+06 1.0993E+07 MULTIPLE R = 0.69569 SE = 248.31 p a r t i a l c o r r e l a t i o n c o e f f i c i e n t s : Min + Max Wave Exposure S a l i n i ty (g kg-1) Time Exposed to A i r (%) EQUATION Xb: S t a n d i n g Crop MEAN SQUARE 1.7735E+06 61657 F-RATIO 28.763 -0.55784 (P=0.0000) -0.23492 (P=0.0227) 0.53224 (P=0.0000) PROBABILITY O.0000 * * 1198.4 - 72.8(WAVE EXP) - 28.1(SAL) + 5.8(AIR EXP) 0> T a b l e 11. M u l t i p l e r e g r e s s i o n a n a l y s e s of Fucus d i s t i chus s t a n d i n g c r o p (g d r y wt m-2) f o r each zone on s e l e c t e d a b i o t i c e n v i r o n m e n t a l f a c t o r s . ZONE I ( a l l sj_tes) a) Contemporaneous v a r i a b l e s S t a n d i n g Crop = -679.4 - 67.5(PFD) + 127.4(H20-T) - 136.0(WAVE EXP) - 76.8(N03) + 70.9(AIR EXP) MULTIPLE R = 0.77482 SE = 268.8 b) An tecedent v a r i a b l e s S t a n d i n g Crop = 611.8 - 108.9(AIR-T VAR) - 119.2(WAVE EXP) -11.7(A IR EXP) MULTIPLE R = 0.77660 SE = 252.4 ZONE 11 (exc1ud i ng Nud ibranch ) a) Contemporaneous v a r i a b l e s s S t a n d i n g Crop = 477.2 - 29.2(PFD) + 93 .0 (H20 -T ) - 146.7(H20-T VAR) - 0.8(RAIN) MULTIPLE R = 0.91524 SE = 115.0 b) An tecedent v a r i a b l e s S t a n d i n g Crop = 753.1 - 46.9(N03) MULTIPLE R = 0.80021 SE = 148.2 ZONE III ( e x c l u d i n g Nud ibranch ) a) Contemporaneous v a r i a b l e s S t a n d i n g Crop = -460.3 + 35.4 (H20-T) + 45.0(WAVE EXP) MULTIPLE R = 0.65000 SE = 93.5 b) An tecedent v a r i a b l e s S t a n d i n g Crop = 842.7 + 23.0(PFD) + 38.9(WAVE EXP) + 62.1(N03) - 63 .5 (SAL ) + 20.4(AIR EXP) CO MULTIPLE R = 0.87209 SE = 64 .0 69 e x p e r i m e n t s p e r f o r m e d on t h e s e p l a n t s ( s e e C h a p t e r 6 ) . O n l y two (2) of s i x t e e n (16) p l a n t s t a g g e d i n Sepetember 1982 s u r v i v e d i n t o May 1983, and t h e s e p l a n t s c o n s i s t e d of t h e h o l d f a s t w i t h a b o u t 5 cm o f h e a v i l y e r o d e d t h a l l u s t i s s u e . In a d d i t i o n , two p o i n t s s h o u l d be m e n t i o n e d : 1 ) A l t h o u g h H_^  s e s s i l e was t h e most abundant s p e c i e s of a l g a e i n Zone I I I a t N u d i b r a n c h , i t s abundance was s t i l l p a t c h y ( o v e r a l l mean = 407.6 ± 377.2 g d r y wt i r r 2 ; CV = 9 2 . 5 % ) ; 2) The mean s t a n d i n g c r o p f o r March t o August 1983 (304.7 g d r y wt n r 2 ) was a b o u t 55% of t h e mean s t a n d i n g c r o p f o r June t o November 1982 (558.8 g d r y wt n r 2 ) . B) Abundant A n n u a l S p e c i e s The two s p e c i e s of i n t e r e s t , L e a t h e s i a d i f f o r m i s and C r y p t o s i p h o n i a woodi i ( J . Ag.) J . Ag., were most abundant i n Zone I I I a t H a i n e s , H e l b y , and W i z a r d . T h e s e m a c r o a l g a e were a l s o f o u n d s p o r a d i c a l l y i n Zone I I o f t h e s e s i t e s , but o n l y i n v e r y m o i s t a r e a s ( s h a l l o w d e p r e s s i o n s , e t c . ) . N e i t h e r s p e c i e s were p r e s e n t i n any abundance a t N u d i b r a n c h . S t a n d i n g c r o p d a t a f o r d i f f o r m i s and C_^  woodi i d u r i n g 1983 a r e p r e s e n t e d i n F i g u r e s 8a-c ( b i o m a s s d a t a f o r C o r a l l i n a V a n c o u v e r i e n s i s Yendo and f o r 1982 a t H a i n e s a r e a l s o shown i n F i g u r e 8 a ) . B o t h s p e c i e s behaved as 70 spring/summer a n n u a l s , however t h e i r p e r i o d o f peak s t a n d i n g c r o p d i f f e r e d . At H e l b y and W i z a r d , woodi i b i o m a s s was g r e a t e s t i n mid-May 1983 and d i f f o r m i s s t a n d i n g c r o p p eaked a month l a t e r ( F i g u r e s 8 b , c ) . C r y p t o s i p h o n i a was s c a r c e ( s t a n d i n g c r o p a l w a y s l e s s t h a n 8 g d r y wt n r 2 ) a t H a i n e s , but C o r a l l i n a V a n c o u v e r i e n s i s a p p e a r e d t o " r e p l a c e " i t a t t h i s s i t e . C r y p t o s i p h o n i a woodi i was f i r s t o b s e r v e d i n M a r c h 1983 ( a l t h o u g h i t may have been p r e s e n t e a r l i e r i n t h e y e a r ) , r e a c h e d a peak b i o m a s s i n May (40-116 g d r y wt r r r 2 ) , and d i s a p p e a r e d by J u l y ( F i g u r e s 8 b , c ) . A two-way ANOVA on t h e biom a s s d a t a f o r H a i n e s , H e l b y , and W i z a r d was p e r f o r m e d ; t h e o n l y s i g n i f i c a n t t e r m was t h e Site*Week i n t e r a c t i o n (F = 3.3093 14,-132df; P=0.00015). F u r t h e r a n a l y s i s of t h i s i n t e r a c t i o n u s i n g one-way ANOVAs showed t h a t t h e o n l y s i g n i f i c a n t d i f f e r e n c e s i n C_^  woodi i b i o m a s s o v e r t i m e were a t W i z a r d (F=5.8925 6,35df; P=0.00025). S-N-K a n a l y s i s ( p <0.0l) of t h e W i z a r d d a t a p r o d u c e d two d i s t i n c t g r o u p s : 1) The week o f maximum b i o m a s s (16 May 1983; 116.1 g d r y wt nr 2 ) ; 2) A l l o t h e r weeks t e s t e d . L e a t h e s i a d i f f o r m i s was f i r s t o b s e r v e d i n l a t e A p r i l -e a r l y May 1983. Peak s t a n d i n g c r o p of t h i s a l g a was r e c o r d e d i n mid-June (96-130 g d r y wt rn"2) and r e m a i n e d a t 71 Figure 8 Mean standing crops of Leathesia d i f f o r m i s , Cryptosiphonia woodii, and C o r a l l i n a  Vancouveriensis at each semi-weekly sample time i n Zone III at Haines, Helby, and Wizard during the spring and summer of 1982 and 1983. A) Haines B) Wizard C) Helby • = di f f o r m i s • = Cj_ vancouveriensis • = C. woodii Month 74 f a i r l y h i g h l e v e l s f o r a month b e f o r e d e c l i n i n g ( F i g u r e s 8 a - c ) . The r e s u l t s of t h e ANOVAs f o r L ^ d i f f o r m i s s t a n d i n g c r o p i n 1982 and 1983 a r e shown i n T a b l e 12. In b o t h y e a r s , L. d i f f o r m i s s t a n d i n g c r o p v a r i e d s i g n i f i c a n t l y o v e r t i m e (a s would be e x p e c t e d o f an a n n u a l s p e c i e s ) . The S i te*Week i n t e r a c t i o n was a l s o s i g n i f i c a n t d u r i n g 1983. F u r t h e r a n a l y s i s o f t h i s t e r m w i t h one-way ANOVAs showed t h a t s t a t i s t i c a l l y s i g n i f i c a n t c h a n g e s i n d i f f o r m i s s t a n d i n g c r o p o c c u r r e d a t H a i n e s and W i z a r d , but n o t a t H e l b y (F=2.5300 11,54df; P=0.01185ns). A l t h o u g h t h e r e were no s t a t i s t i c a l l y s i g n i f i c a n t b e t w e e n - s i t e d i f f e r e n c e s i n L ^ d i f f o r m i s s t a n d i n g c r o p , i n b o t h 1982 and 1983 d i f f o r m i s b i o m a s s a t H a i n e s was g r e a t e r t h a n t h a t a t H e l b y , w h i c h i n t u r n was g r e a t e r t h a n t h a t a t W i z a r d . The l a c k of s t a t i s t i c a l l y s i g n i f i c a n t between s i t e d i f f e r e n c e s was p r o b a b l y due t o t h e h i g h l y v a r i a b l e w i t h i n - s i t e a b u n d a n c e s o f d i f f o r m i s ( i . e . mean l e s s t han s t a n d a r d d e v i a t i o n ) . The r e s u l t s of t h e m u l t i p l e r e g r e s s i o n a n a l y s e s f o r L. d i f f o r m i s and woodi i s t a n d i n g c r o p a r e p r e s e n t e d i n T a b l e s 13 and 14, r e s p e c t i v e l y . L a r g e r MULTIPLE-R and p a r t i a l c o r r e l a t i o n c o e f f i c i e n t s were o b t a i n e d when t h e a n a l y s e s were r e s t r i c t e d t o t h e d a t a f o r Zone I I I a t H a i n e s , H e l b y and W i z a r d ( t h e o n l y a r e a s where t h e s e p l a n t s were f o u n d i n any s i g n i f i c a n t a b u n d a n c e ) . T a b l e 12. A n a l y s i s o f v a r i a n c e of Lea thes i a d i f f o r m i s s t a n d i n g c r o p (g d r y wt m-2) i n Zone III at Ha ine s , He lby , and Wizard f o r 1982 and 1983. SOURCE SUM OF SQUARES DF MEAN SQUARE F-RATIO PROBABILITY 1982: Si t e Week Si te*Week Res i dua l T o t a l 30518 3.7076E+05 68G44 3.9660E+05 8.7435E+05 2 7 12 96 117 15259 52966 5720.3 4131 .2 3.6936 12.821 1.3847 0.02849 ns O.OOOOO * * 0.18655 ns 1983 : Si te Week S i te*Week Res i dua l T o t a l 16787 1.5326E+05 1.3245R+05 4.0052E+05 7.0129E+05 2 1 1 18 159 190 8393.3 13932 7358.2 2519.0 3.3320 5.5310 2.921 1 0.03823 ns 0.00000 * * 0.00017 * * Ul T a b l e 13. M u l t i p l e r e g r e s s i o n a n a l y s i s of Lea thes i a d i f f o r m i s s t a n d i n g c r o p (g d ry wt m-2) on s e l e c t e d a b i o t i c e n v i r o n m e n t a l f a c t o r s . A11 5i tes and Al1 Zones a) Contemporaneous v a r i a b l e s S t a n d i n g Crop = 90.0 - 2.7(PFD) + 6 .4 (H20-T ) - 3.9(N03) - 0.3(AIR EXP) MULTIPLE-R = 0.53249 SE = 20.3 b) An tecedent v a r i a b l e s S t a n d i n g Crop = 21.1 + 1.2(PFD) - 2 .7 (H20-T) - 0.2(AIR EXP) MULTIPLE-R = 0.46403 SE = 13.7 Zone III at Ha ine s , He lby and Wizard Only a) Contemporaneous v a r i a b l e s S t a n d i n g Crop = 114.4 - 7.0(PFD) + 16.7(H20-T) - 26.0(AIR VAR) - 11.1(N03) MULTIPLE-R = 0.88278 SE = 22.0 b) An tecedent v a r i a b l e s S t a n d i n g Crop = 57.7 + 5.9(PFD) - 13.3(H20-T) MULTIPLE-R = 0.66529 SE = 22.1 T a b l e 14. M u l t i p l e r e g r e s s i o n a n a l y s i s of C r y p t o s i phoni a wood i i s t a n d i n g c r o p (g d ry wt m-2) on s e l e c t e d a b i o t i c e n v i r o n m e n t a l f a c t o r s . A1 1 S i tes and A11 Zones a) Contemporaneous v a r i a b l e s S t a n d i n g Crop = 57.5 - 1.7(H20-T) - 0.2(RAIN) - 1.0(SAL) - 0.1(AIR EXP) MULTIPLE-R = 0.49210 SE = G.1 b) Antecedent v a r i a b l e s S t a n d i n g Crop = 15.1 + 0.5(PFD) - 1.7(H20-T) - 0.1(AIR EXP) MULTIPLE-R = 0.42809 SE = 6.3 Zone III at Ha i nes , Helby and W i z a r d Only a) Contemporaneous v a r i a b l e s S t a n d i n g Crop = 188.6 + 1,2(PFD) - 8 .7 (H20-T ) - 0.1(RAIN) - 3 .1(SAL) MULTIPLE-R = 0.74364 SE = 9.4 b) An tecedent v a r i a b l e s S t a n d i n g Crop = 59.3 + 2.1(PFD) - 7 .7 (H20-T) MULTIPLE-R = 0.67647 SE = 10.2 78 C) Common S e c o n d a r y S p e c i e s T h o s e i n t e r t i d a l m a c r o a l g a e c l a s s i f i e d as "common s e c o n d a r y s p e c i e s " were l e s s abundant and more p a t c h i l y d i s t r i b u t e d t h e n t h e "abundant p e r e n n i a l / a n n u a l s p e c i e s " . At t h e t h r e e s h e l t e r e d s i t e s , t h e s e s p e c i e s were g e n e r a l l y r e s t r i c t e d i n Zones I and II t o a r e a s under t h e Fucus c a n o p y . Some of t h e s e s p e c i e s had l a r g e r s t a n d i n g c r o p s i n Zone I I I of t h e s e s i t e s and were a l s o i m p o r t a n t components of t h e " a l g a l t u r f " of Zone II a t N u d i b r a n c h ( e . g. C l a d o p h o r a spp., P o l y s i p h o n i a s p p . ) . Most o f t h e s e m a c r o a l g a e were c l a s s i f i e d by D a y t o n (1975) as e i t h e r " f u g i t i v e " or " o b l i g a t e u n d e r s t o r y " s p e c i e s ( s e e T a b l e 5 ) . T a b l e 15 p r e s e n t s a summary of t h e s t a n d i n g c r o p d a t a f o r t h e s e common s e c o n d a r y s p e c i e s . A n a l y s i s of v a r i a n c e t e s t s were p e r f o r m e d o n l y f o r t h o s e z o n e s a t e a c h s i t e where a . s p e c i e s showed more t h a n a s p o r a d i c or i n f r e q u e n t o c c u r r e n c e . E a c h s p e c i e s showed s p r i n g o r summer maxima i n s t a n d i n g c r o p , a l t h o u g h n o t e v e r y s p e c i e s showed s t a t i s t i c a l l y s i g n i f i c a n t s e a s o n a l c h a n g e s . P e l v e t i o p s i s 1 i m i t a t a , E n d o c l a d i a m u r i c a t a ( P o s t . & Rupr.) J . Ag., and I r i d a e a c o r n u c o p i a e P o s t . & Rupr. were common i n Zones I and I I a t N u d i b r a n c h . T h e i r s t a n d i n g c r o p s were g e n e r a l l y l e s s t h a n 10 g d r y wt i r r 2 , but peak b i o m a s s l e v e l s up t o 29 g d r y wt m~2 were r e c o r d e d . O n l y I . c o r n u c o p i a e showed s t a t i s t i c a l l y s i g n i f i c a n t z o n a l T a b l e 1 5 . S u m m a r y o f s t a n d i n g c r o p d a t a l g d r , w t m - 2 ) a n d a n a i > s e s o f v a r i a n c e f o r t h e c o m m o n s e c o n d a r y s p e e » e s . S P E C I E S C . p a c * f i c u m  C 1 a d o p h o r a s p p . C . Vancouver i e n s i s E . m u r i c a t a  H . a m e r i c a n u m I _ . c o r n u c o p i a e M_ b o r e a l i s N , I a n . P . 1 u r n t a t a P o i y s i p h o n i a s p p U . f e n e s t r a t a S I T E ! 1 ) M O N T H S O F G B E & T E S T E I O M A S S f 2 \ N 3 e 2 o n 1 y n s - s u m m e r 8 2 ( 1 8 1 A 8 5 s u m m e r ( A . 1 3 - 1 3 1 H 19 e a ) 1 I H . 1 8 - 5 2 1 W 9 7 n s ( 3 1 I W 1 7 - 2 5 1 N 1 3 1 ( N 2 1 - 2 6 1 A 1 5 8 3 o n l y s p r m g 8 3 ( 6 7 1 N B 9 5 2 * 3 l o n e 3 - n s n s ( J 1 s u m m e r 8 2 1 2 7 3 1 s o r i n g 8 3 ( 2 2 9 1 N 5 . 1 * 2 n s - s u m m e r 1 7 - 1 0 1 n s ( i I A 1 6 e 3 o n l y - 1 3 1 s u m m e r 8 3 1 18 - 2 J 1 H 7 6 N 2 6 8 2 o n l v n s - s u m m e r 8 2 ( 3 9 - 6 0 1 N s e e 1 : 8 0 S u m m e r 8 2 ( 1 : 2 1 1 z o n e ( 5 1 2 : 3 7 ( 2 : 1 7 1 N 7 e 2 o n l y n s - s u m m e r 8 2 s p r , n g 8 3 ( 2 2 - 2 3 I A se 1 3 o n l y ( 3 1 S u m m e r 8 2 ( 1 0 1 - U 3 I U 5 5 3 N J 4 8 2 o n l y n s - s u m m e r 8 2 ( 1 0 5 1 N 1 0 5 1 o n l , n s - s p r , n g 8 3 1 2 6 - 2 9 1 N 1 2 1 2 o n l y S u m m e r 8 2 / s p r m g 8 3 ( 1 8 H 8 0 3 o n l , - n s - s o r i n g 8 3 ( 1 3 1 w : s e e z o n e < 5 ) 2 J J 3 : 1 2 7 2 o n l y Summer 82 I 2 2C I ( 3 3 5 1 S u m m e r ( 1 6 - 2 2 I N o t e s : I I ) o v e r a 1 1 m e a n s 1 a n d i n g c r o p ( g d r y w t m ') A » H A J N E S . H « M E L B T . W - W I Z A R D . N = N U D 1 B R A N C H ( 2 ) v a l u e s ' n ( ) a r e m a x i m u m r e c c o e d 5 l a n o \ n g c r o p * r . g dr •, w 1 m s e a s o n s t a t e d i s t h a t p e r i o d o f m a x i m u m s t a n d i n g c r o p n s - n o s i g n i f i c a n t d i f f e r e n c e s m s t a n d i n g c r o p b v m o n t h ( A N O V A t < 3 > n s - n o s i g n i f i c a n t d i f f e r e n c e s m s t a n d i n g c r o p b e t w e e n s i t e s ( A N O V A I ( 4 ) n s - n o s i g n i f i c a n t d i f f e r e n c e s m s t a n d m g c r o p b e t w e e n ? o n e s I A N D v f i ) ( 5 ) s i g n i f i c a n t d i f f e r e n c e s i n s t a n d i n g c r o p b e t w e e n z o n e s ( A N D V A J 80 (F=6.8391 1 , l 9 5 d f ; P=0.00962) and s e a s o n a l (F=8.4272 7 , l 9 5 d f ; P=0.00000) c h a n g e s i n b i o m a s s . M a c r o a l g a l b i o m a s s i n Zone II a t N u d i b r a n c h was d o m i n a t e d by C o r a l l i n a V a n c o u v e r i e n s i s (maximum b i o m a s s = 272 g d r y wt i r r 2 ) and Neorhodomela l a r i x ( T u r n . ) Maruda (maximum b i o m a s s = 105 g d r y wt n r 2 ) . C l a d o p h o r a spp., H a l o s a c c i o n americanum L e e , M i c r o c l a d i a b o r e a l i s Rupr., P o l y s i p h o n i a s p p . , and U l v a f e n e s t r a t a P o s t . & Rupr. were a l s o f a i r l y a b u n d a n t i n t h i s zone (maximum s t a n d i n g c r o p s o f 16-26 g d r y wt n r 2 ) . T hese s p e c i e s were g e n e r a l l y p a t c h i l y d i s t r i b u t e d and formed an " a l g a l t u r f " . S i g n i f i c a n t s e a s o n a l c h a n g e s i n a l g a l b i o m a s s were f o u n d f o r C l a d p h o r a s pp. ( s e e T a b l e 16), C o r a l l i n a  v a n c o u v e r i e n s i s (F=4.0846 7,99df; P=0.00056), P o l y s i p h o n i a spp. (F=2.8358 7,99df; P=0.00976), and U l v a f e n e s t r a t a (F=5.3553 7,99df; P=0.00003). However, S-N-K a n a l y s e s ( p<0.0l) d i d not s e g r e g a t e t h e s t a n d i n g c r o p d a t a f o r t h e s e s p e c i e s i n t o d i s t i n c t g r o u p s b a s e d on month. C o r a l l i n a Vancouver i e n s i s , C l a d o p h o r a spp., H. amer icanum , N_^  l a r i x , and l h f e n e s t r a t a were a l s o f o u n d i n Zones I I and I I I a t H a i n e s , H e l b y and W i z a r d . As m e n t i o n e d p r e v i o u s l y , C^ V a n c o u v e r i e n s i s seemed t o " r e p l a c e " C r y p t o s i p h o n i a woodi i i n Zone I I I a t H a i n e s ( F i g u r e s 8 a - c ) . A n a l y s i s of v a r i a n c e showed s i g n i f i c a n t s e a s o n a l v a r i a t i o n i n C_^  v a n c o u v e r i e n s i s s t a n d i n g c r o p i n Zone I I I a t H a i n e s (F=7.6327 7,121df; P=0.0000). S-N-K a n a l y s i s (p<0 . 0 D 81 s e p a r a t e d t h e A p r i l 1983 month from a l l o t h e r months as t h e t i m e o f g r e a t e s t b i o m a s s (67 g d r y wt r r r 2 ) . Neorhodomela l a r i x was a l s o f o u n d i n Zone I I I a t b o t h H a i n e s and W i z a r d , but o n l y o c c a s i o n a l l y a t H e l b y . An a n a l y s i s o f v a r i a n c e showed b e t w e e n - s i t e d i f f e r e n c e s i n N. l a r i x b i omass (F=2.8467 7,215df; P=0.00737). However, S-N-K a n a l y s i s ( p < 0 . 0 l ) d i d not d i v i d e t h e months i n t o any d i s t i n c t g r o u p s . S i g n i f i c a n t d i f f e r e n c e s i n H a l o s a c c i o n americanum s t a n d i n g c r o p i n Zone I I I were f o u n d between H a i n e s and H e l b y (F=19.873 1,239df; P=0.00001). H a l o s a c c i o n americanum was f o u n d o n l y r a r e l y a t W i z a r d . An a n a l y s i s of v a r i a n c e showed s i g n i f i c a n t s e a s o n a l c h a n g e s i n b i o m a s s (F=3.0149 7,239df; P=0.00439), but S-N-K a n a l y s i s ( p < 0 . 0 l ) d i d not s e p a r a t e t h e months. U l v a f e n e s t r a t a was f o u n d t h r o u g h o u t t h e i n t e r t i d a l a t e a c h s i t e , b u t showed i t s g r e a t e s t d e v e l o p m e n t i n Zone I I I at H e l b y , Zones II and I I I a t W i z a r d , and Zone II a t N u d i b r a n c h . C o m p a r i s o n of U^ f e n e s t r a t a s t a n d i n g c r o p i n Zone I I I of H e l b y and W i z a r d w i t h Zone I I a t N u d i b r a n c h showed no s i g n i f i c a n t d i f f e r e n c e s . L i k e w i s e f o r Zone II a t W i z a r d w i t h Zone I I a t N u d i b r a n c h . U^ f e n e s t r a t a b i o m a s s i n Zone I I I of W i z a r d d i f f e r e d s i g n i f i c a n t l y f r o m t h a t a t H e l b y (F = 7.6293 1,213-df; P=0.00624) and from Zone I I a t W i z a r d (F=11.794 1,235df; P = 0 . 0 0 0 7 0 ) . S i g n i f i c a n t s e a s o n a l c h a n g e s i n s t a n d i n g c r o p were f o u n d a t W i z a r d (F=3.4994 9,235df; 82 P=0.00044), however, t h e g r o u p s d i s t i n g u i s h e d by S-N-K a n a l y s i s ( p<0.0l) were v e r y s i m i l a r . C l a d o p h o r a spp. were p e r h a p s t h e most w i d e l y d i s t r i b u t e d of t h e "common s e c o n d a r y s p e c i e s " . T a b l e 16 shows t h e ANOVA r e s u l t s f o r C l a d o p h o r a spp. s t a n d i n g c r o p o v e r a l l s i t e s , z o n e s , and months. S i g n i f i c a n t b e t w e e n - s i t e and s e a s o n a l d i f f e r e n c e s were f o u n d . S-N-K a n a l y s i s (p<0.01) by month p r o d u c e d t h r e e g r o u p s , but t h e y were v e r y s i m i l a r . A n a l y s i s of t h e Zone*Month i n t e r a c t i o n showed s i g n i f i c a n t s e a s o n a l c h a n g e s i n t h e s t a n d i n g c r o p s o f Zone I (F=2.7809 9,498df; P=0.00346) and Zone I I (F=6.0181 9,552df; P=0.00000), b u t not i n Zone I I I . However, once a g a i n S-N-K a n a l y s i s ( p < 0 . 0 l ) d i d n o t d i v i d e t h e months i n t o v e r y d i s t i n c t g r o u p s . F u r t h e r a n a l y s i s o f t h e S i t e * Z o n e i n t e r a c t i o n a t e a c h s i t e u s i n g one-way ANOVAs showed s i g n i f i c a n t z o n a l d i f f e r e n c e s a t H a i n e s (F=6.3543 2,434df; P=0.00191), W i z a r d (F=12.140 2,402df; P=0.00001) and N u d i b r a n c h (F=21.491 2,306df; P=0.00000), b u t not a t H e l b y . C l a d o p h o r a s p p . b i o m a s s a t W i z a r d and N u d i b r a n c h was g r e a t e s t i n Zone II (S-N-K t e s t , p < 0 . 0 l ) . A t H a i n e s , S-N-K a n a l y s i s (p<0.0) showed t h a t C l a d o p h o r a s t a n d i n g c r o p was g r e a t e s t i n Zone I I I . T a b l e 16. A n a l y s i s of v a r i a n c e of C1adophora spp. s t a n d i n g c r o p (g d ry wt m-2) at each s tudy s i t e . SOURCE SUM OF SQUARES DF MEAN SQUARE F-RATIO PROBABILITY Si t e Zone S i te*Zor ie Month S i te*Month Zone*Month S*Z*M Res i dua1 T o t a l 21809 40843 56277 86785 68222 49756 1.1383E+05 2.1696E+06 2.6304E+06 3 2 6 9 25 16 46 1419 1526 7269.7 20422 9379.6 9642.8 2728.9 3109.7 2474.6 1529.0 4.7546 2. 1772 6.1346 6.3067 1.7848 2.0339 1.6185 0.00265 * * 0.19457 ns 0 .00000 * * 0 .00000 * * 0.01007 ns 0.00905 * * 0 .00590 * * Note : Zone mean square t e s t e d a g a i n s t S i t e * Z o n e mean squa re ( f i x e d e f f e c t s model) 84 D i s c u s s i o n M a c r o a l g a l s t a n d i n g c r o p v a r i e d w i t h t i d a l h e i g h t , wave e x p o s u r e and s e a s o n ; t h e r e were a l s o d i f f e r e n c e s i n bi o m a s s between summer 1982 and summer 1983. S p e c i e s d i s t r i b u t i o n s and d i v e r s i t y ( s e e C h a p t e r 5) a l s o v a r i e d a l o n g t h e s e t h r e e g r a d i e n t s . Wave e x p o s u r e a p p e a r e d t o have a major e f f e c t on t h e d i s t r i b u t i o n and abundance of i n t e r t i d a l m a c r o a l g a e . S i g n i f i c a n t b e t w e e n - s i t e d i f f e r e n c e s i n a l g a l s t a n d i n g c r o p were f o u n d ( T a b l e 7 ) . Z o n a t i o n and s p e c i e s c o m p o s i t i o n a l s o v a r i e d between t h e s t u d y s i t e s ( F i g u r e s 5 a - d ) . The abundance of F_;_ d i s t i c h u s i n s h e l t e r e d a r e a s o b s e r v e d i n t h i s s t u d y , d e c r e a s i n g w i t h i n c r e a s i n g wave e x p o s u r e , h a s a l s o been n o t e d by o t h e r w o r k e r s (Burrows e t a l . , 1954; Southward and O r t o n , 1954; S t e p h e n s o n and S t e p h e n s o n , 1961b; D a y t o n , 1971; Menge 1976, 1978; L e w i s , 1977; L u b c h e n c o , 1 980) . In t h e r e g r e s s i o n e q u a t i o n s o f t o t a l a l g a l s t a n d i n g c r o p on s e l e c t e d a b i o t i c e n v i r o n m e n t a l f a c t o r s , t h e MULTIPLE-R and p a r t i a l c o r r e l a t i o n c o e f f i c i e n t s a r e r e l a t i v e l y low ( T a b l e 8 ) . T h i s i s not s u r p r i s i n g , a s many s p e c i e s , w i t h d i f f e r e n t g r o w t h s t r a t e g i e s ( e . g. a n n u a l v s p e r e n n i a l , c o m p e t i t i v e dominant vs f u g i t i v e ) were p r e s e n t , e ach r e s p o n d i n g d i f f e r e n t l y t o t h e e n v i r o n m e n t a l f a c t o r s . 85 In b o t h a n a l y s e s , w ater t e m p e r a t u r e , t h e p e r c e n t t i m e e x p o s e d t o a i r , and t h e minimum + maximum wave e x p o s u r e r a t i n g were s i g n i f i c a n t . Wave e x p o s u r e had a s t r o n g n e g a t i v e c o e f f i c i e n t i n t h e r e g r e s s i o n e q u a t i o n s w h i l e p e r c e n t t i m e e x p o s e d t o a i r had a s m a l l p o s i t i v e e f f e c t ( T a b l e 8 ) . A l t h o u g h t h e r e s u l t s of t h e r e g r e s s i o n a n a l y s i s do n o t p r o v e c a u s a t i o n , t h e y a r e e v i d e n c e i n s u p p o r t of t h e i m p o r t a n c e o f wave e x p o s u r e ( a c t i n g as a d i s t u r b a n c e t o remove a l g a l b i o m a s s ) and t i d a l h e i g h t ( i . e. p e r c e n t t i m e e x p o s e d t o a i r ) i n d e t e r m i n i n g i n t e r t i d a l a l g a l a b u n d a n c e s . H a r d w i c k - Witman and M a t h i e s o n (1983) a l s o f o u n d s i g n i f i c a n t e f f e c t s of t i d a l h e i g h t and p o s i t i o n on an e s t u a r i n e g r a d i e n t on a l g a l a b u n d a n c e s u s i n g m u l t i p l e r e g r e s s i o n t e c h n i q u e s . However, s u b s t r a t u m t y p e was a l s o v e r y i m p o r t a n t i n t h e i r s t u d y . Thorn (1980) f o u n d a s m a l l n e g a t i v e c o r r e l a t i o n (r=-0.33) between emergence time and a l g a l abundance f o r a low i n t e r t i d a l a l g a l community i n Puget Sound. A l g a l abundance was most s t r o n g l y c o r r e l a t e d w i t h a i r t e m p e r a t u r e ( r = 0 . 8 l ) and l i g h t ( r = 0 . 6 2 ) , and n e g a t i v e l y c o r r e l a t e d w i t h r a i n f a l l (r=-0.93; Thorn, 1980). V e r t i c a l d i s t r i b u t i o n s ( t i d a l h e i g h t s ) of t h e i n t e r t i d a l a l g a e i n t h e B a m f i e l d a r e a were c o m p a r a b l e w i t h t h e i r d i s t r i b u t i o n s i n o t h e r a r e a s o f t h e P a c i f i c n o r t h w e s t ( R i g g and M i l l e r , 1949; S t e p h e n s o n and S t e p h e n s o n , 1961a; Widdowson, 1965a; D a y t o n , 1971; D r u e h l and G r e e n , 1982). The v e r t i c a l d i s t r i b u t i o n of a l g a l b i omass v a r i e d a l o n g t h e 86 wave e x p o s u r e g r a d i e n t . The m a c r o a l g a l a s s e m b l a g e a t N u d i b r a n c h (most exposed) was d i s t i n c t l y d i f f e r e n t from t h a t a t H a i n e s , H e l b y , and W i z a r d . A l t h o u g h S t e p h e n s o n and S t e p h e n s o n (1961b) d i d not c o l l e c t any q u a n t i t a t i v e d a t a , t h e i r q u a l i t a t i v e d e s c r i p t i o n s o f a l g a l a b u n d a n c e s and d i s t r i b u t i o n s ( t i d a l h e i g h t and wave e x p o s u r e ) f o r t h e s o u t h e a s t c o a s t of V a n c o u v e r I s l a n d seem s i m i l a r t o t h o s e o b s e r v e d i n t h i s s t u d y f o r t h e B a m f i e l d a r e a . F u c u s d i s t i c h u s formed an e x t e n s i v e c a n o p y a t t h e t h r e e s h e l t e r e d s i t e s ; s t a n d i n g c r o p s i n c r e a s e d i n t h e l o w e r z o n e s ( I I and I I I ) and d e c r e a s e d i n Zone I as wave e x p o s u r e i n c r e a s e d ( T a b l e 6 ) . S t e p h e n s o n and S t e p h e n s o n (1961b) a l s o n o t e d a r e d u c t i o n i n F u c u s and i n c r e a s e i n H^ s e s s i l e abundance w i t h i n c r e a s i n g wave e x p o s u r e . D a y t o n (1971) and L u b c h e n c o (1980) n o t e d s i m i l a r c h a n g e s i n f u c o i d abundance as f o u n d h e r e . As wave e x p o s u r e i n c r e a s e d , f u c o i d s became more abundant ( p e r c e n t c o v e r ) l o w e r on t h e s h o r e . In a d d i t i o n , t h e r e was an i n c r e a s e i n " f u g i t i v e " or " e p h e m e r a l " s p e c i e s a s wave e x p o s u r e i n c r e a s e d ( s e e T a b l e 1 i n b o t h D a y t o n , 1971 and L u b c h e n c o , 1980). F u c u s d i s t i c h u s was t h e most abundant s p e c i e s o f m a c r o a l g a e i n t h e s t u d y a r e a , a t t i m e s r e a c h i n g s t a n d i n g c r o p l e v e l s o f 1 kg d r y wt m" 2. The v a l u e s f o u n d h e r e a r e s i m i l a r t o t h o s e r e p o r t e d by N e i l l (1977) f o r F u c u s s p i r a l i s L. i n n o r t h w e s t S p a i n , and Thorn (1983) f o r F u c u s d i s t i c h u s s s p . e d e n t a t u s (de l a P y l . ) P o w e l l i n Puget Sound. F u c o i d 87 b i o m a s s i n H e l g o l a n d r a n g e d between 0.5 kg d r y wt r r r 2 f o r F. s p i r a l i s and 3 kg d r y wt i r r 2 f o r F u c u s s e r r a t u s L. and F u c u s v e s i c u l o s u s L. (Munda and Markham, 1982). In Nova S c o t i a , M a c F a r l a n e (1952) r e p o r t e d a mean v a l u e of a b o u t 3.4 kg d r y wt n r 2 and Mann (1972a) f o u n d a mean of 1.6 kg d r y wt i r r 2 f o r t h e combined s t a n d i n g c r o p s of A s c o p h y l l u m nodosum ( L . ) L e j o l i s and F u c u s spp. ( v a l u e s c o n v e r t e d from f r e s h w e i g h t u s i n g a r a t i o of 0.2 d r y : f r e s h w e i g h t ) . In e s t u a r i n e a r e a s , f u c o i d b i o m a s s r a n g e s between 100-500 g d r y wt n r 2 ( B r i n k h u i s , 1976, 1977c; Chock and M a t h i e s o n , 1983). Thus, t h e s t a n d i n g c r o p l e v e l s f o u n d f o r F. d i s t i c h u s i n t h i s s t u d y a r e a b o u t mid-way a l o n g t h e r a n g e of v a l u e s p r e v i o u s l y r e p o r t e d f o r c o a s t a l and e s t u a r i n e a r e a s t h r o u g h o u t N o r t h A m e r i c a and E u r o p e . Low MULTIPLE-R and p a r t i a l c o r r e l a t i o n c o e f f i c i e n t s were f o u n d i n t h e r e g r e s s i o n a n a l y s e s o f F\_ d i s t i c h u s s t a n d i n g c r o p on s e l e c t e d a b i o t i c e n v i r o n m e n t a l f a c t o r s . Thorn (1983) a l s o r e p o r t e d low MULTIPLE-R v a l u e s f o r a s i m i l a r r e g r e s s i o n a n a l y s i s o f F\_ d i s t i c h u s c o v e r and d e n s i t y on s e l e c t e d e n v i r o n m e n t a l f a c t o r s . In a d d i t i o n , t h e f a c t o r s p r e s e n t i n t h e r e g r e s s i o n e q u a t i o n s , and t h e m a g n i t u d e s of t h e i r c o e f f i c i e n t s , d i f f e r e d g r e a t l y . I t i s a l s o i m p o r t a n t t o n o t e t h o s e e n v i r o n m e n t a l f a c t o r s w h i c h d i d not f i g u r e i n t o t h e r e g r e s s i o n e q u a t i o n s i n T a b l e s 8 and 10. Water t e m p e r a t u r e was s i g n i f i c a n t , b ut n e i t h e r a i r t e m p e r a t u r e nor t h e d a i l y v a r i a t i o n i n a i r o r 88 water t e m p e r a t u r e were i m p o r t a n t . The l a c k of s i g n i f i c a n c e of t h e l a t t e r two f a c t o r s was e a s i l y u n d e r s t o o d , f o r n e i t h e r showed a s t r o n g s e a s o n a l p a t t e r n . However, a i r and water t e m p e r a t u r e were h i g h l y c o r r e l a t e d ( r = 0 . 9 l 5 1 ; T a b l e I I I ) . However, w h i l e water t e m p e r a t u r e was r e l a t i v e l y s t a b l e d u r i n g t h e summer months, a i r t e m p e r a t u r e was i n c r e a s i n g ; s t a n d i n g c r o p l e v e l s were a l s o r e l a t i v e l y s t a b l e d u r i n g t h e summer. In a d d i t i o n , t h e y e a r l y range o f water t e m p e r a t u r e s was l e s s t h a n t h a t of a i r t e m p e r a t u r e . T h e s e d i f f e r e n c e s may a c c o u n t f o r t h e i n c l u s i o n of water t e m p e r a t u r e i n t h e e q u a t i o n s and n o t a i r t e m p e r a t u r e . Thorn ( 1 9 8 0 ) , however, f o u n d s t r o n g c o r r e l a t i o n s between a l g a l p e r c e n t c o v e r and a i r t e m p e r a t u r e ( r = 0 . 8 l ) i n Puget Sound, and o n l y s m a l l (and o p p o s i t e ) c o r r e l a t i o n s w i t h water t e m p e r a t u r e (r=-0.39) and t h e amount o f t i m e e x p o s e d t o a i r ( r = - 0 . 3 3 ) . F u c u s  d i s t i c h u s c o v e r and d e n s i t y were a l s o c o r r e l a t e d w i t h a i r t e m p e r a t u r e i n Puget Sound (Thorn, 1983). An a n a l y s i s o f s e a s o n a l c h a n g e s i n F ^ d i s t i c h u s s t a n d i n g c r o p i n Zones I and I I o f t h e s h e l t e r e d s i t e s showed t h a t F ^ d i s t i c h u s b i o m a s s d e c r e a s e d d u r i n g t h e w i n t e r i n e v e r y zone b u t Zone I a t H a i n e s ( F i g u r e s 6a~c) . The w i n t e r s t a n d i n g c r o p l e v e l s were a b o u t t w e n t y - f i v e p e r c e n t (25%) o f t h e summer 1982 l e v e l s . S i m i l a r s e a s o n a l c h a n g e s i n f u c o i d abundance were n o t e d by N e i l l ( 1 9 7 7 ) , Chock and M a t h i e s o n ( 1 9 8 3 ) , and Thorn ( 1 9 8 3 ) . 89 W h i l e i n c r e a s e d wave a c t i o n d u r i n g t h e w i n t e r may have r e d u c e d d i s t i c h u s s t a n d i n g c r o p a t H e l b y and W i z a r d , i t i s d o u b t f u l t h a t wave a c t i o n c o u l d have done so a t H a i n e s ( T a b l e 1 ) . The h y p o t h e s i s t h a t F\ d i s t i c h u s may u n d e r g o a s e a s o n a l d e c l i n e , p e r h a p s due t o a p o s t - r e p r o d u c t i v e l o s s of v i g o u r , s t i l l d oes not e x p l a i n t h e d i f f e r e n t s e a s o n a l p a t t e r n s i n Zone I and Zone II a t H a i n e s . A s e c o n d h y p o t h e s i s , b a s e d on t h e work of Schonbeck and N o r t o n ( 1 9 7 9 ) , i s t h a t t h e c o m b i n a t i o n of l o n g e r p e r i o d s of submergence and e l e v a t e d s e a w a t e r n i t r a t e c o n c e n t r a t i o n s d u r i n g t h e w i n t e r r e s u l t e d i n t h e d e a t h of t h e Zone II p l a n t s a t H a i n e s . Schonbeck and N o r t o n (1979) f o u n d t h a t P e l v e t i a c a n a l i c u l a t a ( L . ) Dene, e t T h u r . and F ^ s p i r a l i s s e n e s c e d and d e c a y e d when submerged f o r l o n g p e r i o d s ( 2 0 h o u r s d " 1 ) a t h i g h n i t r a t e c o n c e n t r a t i o n s (33 p g - a t NO ^ 1 " 1 ) , but not a t l o w e r c o n c e n t r a t i o n s (6.6 p g - a t NO^ 1" 1 ) . At H a i n e s , t h e r e was a l a r g e d i f f e r e n c e i n t h e p e r c e n t t i m e t h e Zone I and Zone I I p l a n t s were e x p o s e d t o a i r d u r i n g t h e w i n t e r ( T a b l e 3; F e b r u a r y 1983). A l s o , t h e n i t r a t e c o n c e n t r a t i o n a t H a i n e s d u r i n g J a n u a r y 1983 was r e l a t i v e l y h i g h (18.6 p g - a t N0 3 l " 1 ) . T h u s , t h e c ombined e f f e c t s of i n c r e a s e d submergence and e l e v a t e d n i t r a t e c o n c e n t r a t i o n d u r i n g t h e w i n t e r may have c o n t r i b u t e d t o t h e d e c l i n e i n F\ d i s t i c h u s s t a n d i n g c r o p i n Zone I I a t H a i n e s ; t h e Zone I p l a n t s were s p a r e d t h e s e c o n d i t i o n s and s u r v i v e d . A d d i t i o n a l e x p e r i m e n t a t i o n i s needed t o e v a l u a t e 90 t h i s h y p o t h e s i s and e l u c i d a t e t h e m e c h a n i s m ( s ) r e s p o n s i b l e f o r i n t e r a c t i n g e f f e c t s o f e l e v a t e d n i t r o g e n c o n c e n t r a t i o n s and i n c r e a s e d submergence. In a d d i t i o n t o b e i n g t h e most abundant s p e c i e s of i n t e r t i d a l m a c r o a l g a e i n t h e s t u d y a r e a , F\_ d i s t i c h u s a p p e a r e d t o p l a y an i m p o r t a n t s t r u c t u r a l r o l e i n t h i s community. Many of t h e "common s e c o n d a r y s p e c i e s " ( e . g. C l a d o p h o r a s p p . and P o l y s i p h o n i a spp.) were o n l y f o u n d a s u n d e r s t o r y s p e c i e s i n t h e upper i n t e r t i d a l of t h e more p r o t e c t e d s i t e s . F u c u s d i s t i c h u s a l s o a p p e a r e d t o be an i m p o r t a n t i n f l u e n c e on t h e d i s t r i b u t i o n and abundance of L i t t o r i n a s p p . ( t h e r o l e s o f F ^ d i s t i c h u s i n i n t e r t i d a l community s t r u c t u r e w i l l be d i s c u s s e d i n more d e t a i l i n C h a p t e r 5 ) . The o t h e r a bundant p e r e n n i a l s p e c i e s , H e d o p h y l l u m  s e s s i l e , was d ominant o n l y i n Zone I I I a t N u d i b r a n c h ; o c c a s i o n a l p l a n t s were a l s o f o u n d i n Zone II a t t h i s s i t e . D a y t o n (1975) a l s o n o t e d t h a t t h e d i s t r i b u t i o n of s e s s i l e was l i m i t e d t o s h o r e s e x p o s e d t o m o d e r a t e d e g r e e s of wave a c t i o n . A l t h o u g h t h e " p h y s i o l o g i c a l l y o p t i m a l " s i t e s ( b a s e d on r a t e s o f r e c o v e r y a f t e r r e m o v a l ) f o r H_;_ s e s s i l e g r o w t h were t h e most e x p o s e d s i t e s , s e s s i l e was o u t c o m p e t e d a t t h e s e s i t e s by L e s s o n i o p s i s l i t t o r a l i s ( F a r l . e t S e t c h . ) R e i n k e and L a m i n a r i a s e t c h e l l i i S i l v a . D a y t o n (1975) a t t r i b u t e d t h e a b s e n c e o f s e s s i l e f r o m s h e l t e r e d s i t e s t o t h e h a r m f u l e f f e c t s of i n c r e a s e d s i l t a t i o n a t t h e s e s i t e s on 91 t h e g a m e t o p h y t e . However, w h i l e s i l t a t i o n may have been a p r o b l e m a t H a i n e s and H e l b y (a t h i n l a y e r of sand was p r e s e n t i n Zone I I I a t t h e s e s i t e s ) , t h e r e was l i t t l e e v i d e n c e of s i l t a t i o n a t W i z a r d . A l t h o u g h t h e r e were no s i g n i f i c a n t s e a s o n a l d i f f e r e n c e s i n H_;_ s e s s i l e s t a n d i n g c r o p , t h i s may have been due t o t h e l a c k of d a t a f o r t h e w i n t e r 1982-1983. A l l but two o f t h e p l a n t s t a g g e d i n t h e f a l l of 1982 f a i l e d t o s u r v i v e t h e w i n t e r ( s e e C h a p t e r 6 ) . Widdowson (1965b) r e p o r t e d t h a t f a l l and w i n t e r s t o r m s were p a r t i c u l a r l y damaging t o H. s e s s i l e p o p u l a t i o n s . However, n o t e t h a t H^ s e s s i l e i s r e l a t i v e l y p a t c h i l y d i s t r i b u t e d , so t h a t s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e s would be d i f f i c u l t t o o b t a i n i n any c a s e . Mean H^ s e s s i l e b i o m a s s d u r i n g t h e s u m m e r / f a l l 1982 r a n g e d between 450 and 725 g d r y wt i r r 2 , w h i l e PL s e s s i l e s t a n d i n g c r o p was l e s s t h a n 375 g d r y wt n r 2 d u r i n g t h e spring/summer 1983. J u v e n i l e s p o r o p h y t e s were a l s o abundant d u r i n g t h e summer 1982, but r a r e d u r i n g t h e spring/summer 1983. The l o w e r H_;_ s e s s i l e s t a n d i n g c r o p d u r i n g 1983 may, t h e r e f o r e , have been t h e r e s u l t o f r e d u c e d r e c r u i t m e n t t h a t y e a r and s e v e r e wave a c t i o n d u r i n g t h e w i n t e r ( s e e a l s o Widdowson, 1965b). L a r g e r MULTIPLE-R and p a r t i a l c o r r e l a t i o n c o e f f i c i e n t s were o b t a i n e d when t h e r e g r e s s i o n a n a l y s e s o f C\ w o o d i i and L. d i f f o r m i s s t a n d i n g c r o p were r e s t r i c t e d t o t h e d a t a f o r 92 Zone I I I a t H a i n e s , H e l b y and W i z a r d . The f o l l o w i n g d i s c u s s i o n w i l l t h e r e f o r e be l i m i t e d t o t h e r e g r e s s i o n e q u a t i o n s p e r t a i n i n g o n l y t o t h e Zone I I I d a t a ( E q u a t i o n s 12-2ab and 13-2ab). In e a c h r e g r e s s i o n e q u a t i o n , l i g h t (PFD) and water t e m p e r a t u r e were s i g n i f i c a n t , w i t h t h e c o e f f i c i e n t s f o r w a t e r t e m p e r a t u r e t w o - t o - t h r e e t i m e s (2-3x) t h o s e f o r l i g h t . The r e s p e c t i v e c o e f f i c i e n t s i n t h e L_^_ d i f f o r m i s e q u a t i o n s were about t w i c e t h a t of t h e woodi i e q u a t i o n s , r e f l e c t i n g t h e f a c t t h a t d i f f o r m i s b i o m a s s was a b o u t t w i c e t h a t o f C. woodi i . E x c e p t f o r E q u a t i o n 12-2b ( d i f f o r m i s , a n t e c e d e n t ) , t h e c o e f f i c i e n t s f o r l i g h t were p o s i t i v e and t h o s e f o r w a t e r t e m p e r a t u r e n e g a t i v e . T h e r e i s v e r y l i t t l e e c o l o g i c a l i n f o r m a t i o n on e i t h e r L. d i f f o r m i s o r woodi i . In a d d i t i o n , t h e r e does not a p p e a r t o have been any p r e v i o u s e c o l o g i c a l s t u d i e s of i n t e r t i d a l a r e a s s i m i l a r t o Zone I I I a t H a i n e s , H e l b y and W i z a r d . N e i t h e r R i c k e t t s e t a l . (1968) nor D a y t o n (1971, 1975) m e n t i o n d i f f o r m i s . DeWreede (1983) has s t u d i e d t h e i n t e r a c t i o n s between Rhodomela l a r i x ^(Turn.) C. Ag. (= Neorhodomela l a r i x ) and S a r g a s s u m muticum (Yendo) F e n s h . , b u t t h e s e p l a n t s were p a t c h i l y d i s t r i b u t e d i n Zone I I I a t t h e s h e l t e r e d B a m f i e l d s i t e s . Thorn (1980) o b s e r v e d low (<4.9% c o v e r ) a b u n d a n c e s of C. woodi i a t v a r i o u s t i m e s of t h e y e a r d u r i n g a two y e a r s t u d y . In Puget Sound, Hurd (1917) f o u n d t e t r a s p o r i c , 93 c a r p o s p o r i c and "young" C. woodi i from December t o F e b r u a r y . R. E. Foreman ( u n p u b l i s h e d d a t a ) c o l l e c t e d p l a n t s f r o m December t o A u g u s t a t a s u b t i d a l l o c a t i o n i n t h e S t r a i t of G e o r g i a . Maximum b i o m a s s was 23.5 g d r y wt n r 2 , wh i c h was s l i g h t l y l o w e r t h a n t h a t f o u n d i n t h i s s t u d y . Thus, C. woodi i may not be a s t r i c t spring/summer a n n u a l . H a r l i n (1969) r e p o r t e d f i n d i n g d i f f o r m i s d u r i n g May and J u n e , but o n l y on a sandy s h o r e where i t was e p i p h y t i c on worm t u b e s . The maximum d i f f o r m i s b i o m a s s i n G r e a t Pond, M a s s a c h u s e t t s was n o t e d i n June ( C o n o v e r , 1958). In t h e S t r a i t o f G e o r g i a , R. E. Foreman ( u n p u b l i s h e d d a t a ) c o l l e c t e d J J ^ d i f f o r m i S between F e b r u a r y and O c t o b e r . As w i t h C_^  woodi i , maximum s t a n d i n g c r o p i n t h e S t r a i t of G e o r g i a (38.8 g d r y wt n r 2 ) was l e s s t h a n t h a t i n B a m f i e l d . In Nova S c o t i a , Chapman and Goudey (1983) have r e c e n t l y s t u d i e d t h e demography of d i f f o r m i s . The a l g a was f i r s t o b s e r v e d i n e a r l y June and s u r v i v e d i n t o mid-September. Peak s t a n d i n g c r o p , i n m i d - J u l y , was about 5.5 g d r y wt n r 2 . Thus, d i f f o r m i s i s a b o u t t w e n t y t i m e s (20x) l e s s abundant i n Nova S c o t i a a s compared w i t h B a r k l e y Sound. Chapman and Goudey (1983) a t t r i b u t e d d i f f o r m i s m o r t a l i t y t o i n c r e a s e d c r o w d i n g . They a l s o n o t e d an i n c r e a s e i n m o r t a l i t y w i t h i n c r e a s e d wave a c t i o n , however t h e y u s e d o n l y one s t u d y s i t e w h i c h t h e y d e s c r i b e d as " e x p o s e d t o heavy s u r f t h r o u g h o u t much of t h e s t u d y p e r i o d " , and wave a c t i o n i n c r e a s e d d u r i n g t h e summer. W h i l e 94 L. d i f f o r m i s was o n l y abundant a t t h e s h e l t e r e d s i t e s a t B a m f i e l d , i t was a p p a r e n t l y f o u n d a t an " e x p o s e d " s i t e i n Nova S c o t i a . T h i s may a l s o p a r t l y e x p l a i n t h e g r e a t d i f f e r e n c e i n d i f f o r m i s s t a n d i n g c r o p between t h e two c o a s t s . A l t h o u g h no s i g n i f i c a n t b e t w e e n - s i t e d i f f e r e n c e s i n L. d i f f o r m i s s t a n d i n g c r o p were f o u n d a t B a m f i e l d , L. d i f f o r m i s b i o m a s s d i d d e c r e a s e a l o n g t h e i n c r e a s i n g wave e x p o s u r e g r a d i e n t from H a i n e s t o N u d i b r a n c h . The "common s e c o n d a r y s p e c i e s " were e i t h e r w i d e l y d i s t r i b u t e d t h r o u g h o u t t h e i n t e r t i d a l and t h e s t u d y a r e a ( e . g. C l a d o p h o r a s p p . ) , or showed maximum ab u n d a n c e s i n p a r t i c u l a r a r e a s a n d / o r t i m e s , w i t h s p o r a d i c o c c u r r e n c e s o t h e r w i s e ( e . g. C o r a l l i n a V a n c o u v e r i e n s i s , H a l o s a c c i o n  americanum , Neorhodomela l a r i x ). The s t a n d i n g c r o p l e v e l s f o r t h e s e s p e c i e s were c o m p a r a b l e t o t h o s e f o r s i m i l a r s p e c i e s i n S p a i n ( N e i l l , 1977), H e l g o l a n d (Munda and Markham, 1982) and a New E n g l a n d e s t u a r y ( C o n o v e r , 1958), but much g r e a t e r t h a n t h o s e r e p o r t e d by Chock and M a t h i e s o n (1983) f o r a New Hampshire e s t u a r y . B e c a u s e of t h e i r r e l a t i v e l y p a t c h y d i s t r i b u t i o n s , i t i s d i f f i c u l t t o make any c o n c l u s i o n s c o n c e r n i n g t h e s e s p e c i e s . Some o f t h e s e s p e c i e s a r e a l m o s t c e r t a i n l y r e s t r i c t e d by p a r t i c u l a r p h y s i c a l c o n d i t i o n s , w h i l e b i o t i c i n t e r a c t i o n s ( s u c h as t h e p r e s e n c e of an a l g a l c a n o p y ) a r e 95 a l s o i m p o r t a n t . The s c a l e of t h i s s t u d y does not a l l o w f o r s u c h f i n e d i s c r i m i n a t i o n s , but more g e n e r a l s t a t e m e n t s a b o u t some of t h e s e s p e c i e s a r e p o s s i b l e . P e l v e t i o p s i s 1 i m i t a t a was f o u n d o n l y i n Zone I a t N u d i b r a n c h . T h i s a l g a has been c h a r a c t e r i s t i c a l l y a s s o c i a t e d w i t h t h e h i g h e r z o n e s o f r e l a t i v e l y more wave e x p o s e d s h o r e s ( R i g g and M i l l e r , 1949; R i c k e t t s e t a l . , 1968; D a y t o n , 1971). The p r e s e n c e o f t h e " a l g a l t u r f " i n Zone II a t N u d i b r a n c h may be a s e l f - r e i n f o r e i n g phenomenon, p e r m i t t i n g t h e c o e x i s t e n c e o f a l a r g e number of s p e c i e s i n h i g h e r a b u n d a n c e s t h a n f o u n d e l s e w h e r e . Hay (1981) has shown t h a t t h e t u r f s s u f f e r l e s s p h y s i o l o g i c a l damage due t o d e s i c c a t i o n s t r e s s and a r e more r e s i s t a n t t o h e r b i v o r e s . The m o r p h o l o g y of N e orhodomela l a r i x d i f f e r e d between Zone I I I a t H a i n e s and Zone II a t N u d i b r a n c h . In t h e f o r m e r c a s e , t h e t h a l l i were t o u g h , w i r y , and r o p e - l i k e , w i t h s h o r t s e c o n d a r y b r a n c h l e t s but l o n g m a j o r a x e s . N_j_ l a r i x was much s h o r t e r and b u s h i e r a t N u d i b r a n c h , w i t h l o n g e r s e c o n d a r y b r a n c h l e t s o f a s o f t e r t e x t u r e . S i m i l a r c h a n g e s i n t h e m o r p h o l o g y o f t h i s s p e c i e s have been r e p o r t e d by D e t h i e r ( 1 9 8 2 ) , and may have been due t o t h e i n f l u e n c e s o f wave a c t i o n , s a n d a b r a s i o n , and h e r b i v o r y . C o r a l l i n a Vancouveriens i s was c l a s s i f i e d as an " o b l i g a t e u n d e r s t o r y s p e c i e s " by D a y t o n ( 1 9 7 5 ) . However, a t B a m f i e l d , V a n c o u v e r i e n s i s was f o u n d as p a r t of t h e " a l g a l t u r f " i n Zone II a t N u d i b r a n c h , i n Zone I I I a t H a i n e s , and 96 u n d e r t h e s e s s i l e canopy i n Zone I I I a t N u d i b r a n c h . I t t h u s seems e r r o n e o u s t o d e s c r i b e v a n c o u v e r i e n s i s as an " o b l i g a t e " u n d e r s t o r y s p e c i e s , but i t does a p p e a r t o be v e r y s u s c e p t i b l e t o d e s i c c a t i o n o r h e a t s t r e s s . C o r a l l i n a  v a n c o u v e r i e n s i s was most abundant i n t h e e a r l y s p r i n g . A t H a i n e s , t h e Zone I I I p o p u l a t i o n v i r t u a l l y d i s a p p e a r e d w i t h t h e o n s e t of warmer weather i n May; t h e p o p u l a t i o n a t N u d i b r a n c h a l s o d e c l i n e d , b u t s t i l l s u r v i v e d t h e summer. D e f i n i t e s i g n s o f b l e a c h i n g were o b s e r v e d a t b o t h s i t e s . T h i s s u g g e s t s t h a t even l i m i t e d e x p o s u r e t o d e s i c c a t i o n or h e a t s t r e s s c a n be v e r y h a r m f u l t o t h i s p l a n t . As w i t h F\ d i s t i c h u s and H_j_ s e s s i l e , t h e s t a n d i n g c r o p s o f t h e "common s e c o n d a r y s p e c i e s " were l o w e r i n t h e summer 1983 as compared w i t h t h e summer 1982. T h i s s u g g e s t s some o v e r a l l c l i m a t i c d i f f e r e n c e between t h e two y e a r s . However, t h e v a l u e s f o r t h e v a r i o u s e n v i r o n m e n t a l f a c t o r s m o n i t o r e d were r e l a t i v e l y s i m i l a r d u r i n g t h e two p e r i o d s ( s e e C h a p t e r 2 ) , a l t h o u g h w ater t e m p e r a t u r e was s l i g h t l y l o w e r and a i r t e m p e r a t u r e h i g h e r i n 1983. The c r u c i a l p e r i o d , however, may have been t h e l a t e w i n t e r - e a r l y s p r i n g of 1983. T h i s i s t h e t i m e o f r e c r u i t m e n t f o r many o f t h e s e s p e c i e s ( e . g. H_;_ s e s s i l e ) and t h e b e g i n n i n g o f t h e new y e a r ' s g r o w t h . An a l l - t i m e r e c o r d r a i n f a l l f o r B a m f i e l d was r e c o r d e d i n F e b r u a r y 1983 (660.3 mm), and i t seemed a s i f t h e w i n t e r of 1982-83 was u n u s u a l l y warm and r o u g h . In a d d i t i o n , t h e r e was some 97 c o n c e r n t h a t t h e E l N i n o e v e n t o f 1982-83 had e x t e n d e d i n t o B a r k l e y Sound. I t was o b v i o u s t h a t v a r i o u s a n i m a l s p e c i e s were " b e h a v i n g oddly".- The u s u a l spawning run o f t h e s q u i d L o l i g o o p a l e s c e n s B e r r y , w h i c h a n n u a l l y o c c u r s i n March, was l i t e r a l l y n o n e x i s t e n t i n 1983. In a d d i t i o n , v a r i o u s t y p i c a l l y o c e a n i c s p e c i e s , s u c h as t h e scyphomedusan C h r y s a o r a m e l a n a s t e r B r a n d t , were f o u n d i n B a m f i e l d I n l e t and i t s e n v i r o n s . I h e s i t a t e t o a t t r i b u t e t h e o b s e r v e d y e a r - t o - y e a r v a r i a t i o n i n a l g a l s t a n d i n g c r o p s t o t h e e f f e c t s of an E l N i n o i n B a r k l e y Sound, but t h i s may have been a c o n t r i b u t i n g f a c t o r . S h o r t p e r i o d s of e l e v a t e d water t e m p e r a t u r e s may have a d v e r s e l y d i s r u p t e d t h e r e c r u i t m e n t and g r o w t h of s p o r e l i n g s . I t s h o u l d be n o t e d t h a t t h e r e were no s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e s - i n t h e m a c r o a l g a l s t a n d i n g c r o p s between summer 1982 and summer 1983. J o n e s e t a l . (1979) have a l s o s t r e s s e d t h a t y e a r l y v a r i a t i o n s i n abundance have been f o u n d f o r many i n t e r t i d a l o r g a n i s m s . They c o n c l u d e d t h a t s u c h v a r i a t i o n l i m i t e d t h e v a l u e of s h o r t - t e r m " b a s e l i n e " s t u d i e s . C o n o v e r (1958) n o t e d y e a r l y d i f f e r e n c e s i n a l g a l a b u n d a n c e s i n a M a s s a c h u s e t t s e s t u a r y , and a t t r i b u t e d t h i s t o i r r e g u l a r f a c t o r s ( s e v e r e w e a t h e r , e t c . ) and u n u s u a l d e p a r t u r e s from t h e no r m a l s e a s o n a l v a l u e s o f a number of e n v i r o n m e n t a l f a c t o r s . E x p e r i m e n t e r - i n d u c e d b i a s , as d i s c u s s e d by F a l k ( 1 9 7 4 ) , must a l s o be c o n s i d e r e d a s a p o s s i b l e i n f l u e n c e . C o n t i n u o u s s a m p l i n g o v e r a f i f t e e n 98 month p e r i o d may have a f f e c t e d t h e t r a n s e c t s ; t r a m p i n g t h r o u g h t h e i n t e r t i d a l c a n e a s i l y d i s l o d g e p l a n t s , c r u s h a n i m a l s , e t c . However, t h e use o f t h r e e t r a n s e c t s a t e a c h s i t e , v i s i t e d a t s i x - w e e k i n t e r v a l s , and t h e c o l l e c t i o n of o n l y t h e minimum number of q u a d r a t s t o o b t a i n r e a s o n a b l e v a r i a n c e e s t i m a t e s , s h o u l d have m i n i m i z e d any e x p e r i m e n t e r i n d u c e d e f f e c t s . The o b s e r v e d v a r i a t i o n s i n a l g a l s t a n d i n g c r o p s e m p h a s i z e t h e need f o r l o n g - t e r m s t u d i e s , c e r t a i n l y e x c e e d i n g one y e a r , and p r o b a b l y t h r e e y e a r s o r l o n g e r i n d u r a t i o n , t o p r o p e r l y and a c c u r a t e l y a s s e s s t h e p r o d u c t i v i t y of i n t e r t i d a l m a c r o a l g a e . 99 CHAPTER FOUR - INVERTEBRATE ABUNDANCES H e r b i v o r e s may a f f e c t t h e p r o d u c t i v i t y o f i n t e r t i d a l m a c r o a l g a e i n a number of ways. By f e e d i n g on s p o r e s and s m a l l s p o r e l i n g s , a s w e l l as p r e y i n g upon mature p l a n t s , h e r b i v o r e s c o u l d s e v e r e l y r e d u c e a l g a l s t a n d i n g c r o p s . At e q u i v a l e n t r a t e s o f n e t p h o t o s y n t h e s i s , t h e l o w e r t h e s t a n d i n g c r o p t h e low e r t h e a l g a l p r o d u c t i v i t y . They may a l s o i n f l u e n c e v e g e t a t i v e p r o p a g a t i o n by s e l e c t i v e f e e d i n g on g r o w i n g t i p s . However, t h e e f f e c t s of h e r b i v o r y may n o t be as s i m p l e a s t h i s , f o r h e r b i v o r e s , by c r o p p i n g back m a c r o a l g a e , may p r e v e n t s e l f - s h a d i n g and t h u s m a i n t a i n p r o d u c t i v i t y a t h i g h l e v e l s . In a d d i t i o n , ' h e r b i v o r e s may d i f f e r e n t i a l l y i n f l u e n c e v a r i o u s s p e c i e s , and one might a l s o e x p e c t p o s i t i v e and n e g a t i v e f e e d b a c k l o o p s between a l g a l a b u n d a n c e s and h e r b i v o r e s . F o r example, w h i l e an " a l g a l t u r f " may r e s t r i c t h e r b i v o r e a b u n d a n c e s and d i s t r i b u t i o n s (Hay, 1981; Underwood and J e r n a k o f f , 1981), o t h e r i n v e r t e b r a t e s may be c l o s e l y a s s o c i a t e d w i t h m a c r o a l g a e ( G u n n i l l , 1982; Hawkins and H a r t n o l l , 1983). A number of w o r k e r s have> examined t h e impact o f h e r b i v o r e s on i n t e r t i d a l m a c r o a l g a e (Lodge, 1948; Burrows and Lodge, 1950; C a s t e n h o l z , 1961; D a y t o n , 1971; Menge, 1976; L u b c h e n c o 1980, 1983; Underwood, 1980; Underwood and 1 0 0 J e r n a k o f f , 1981; B e r t n e s s e t a l . , 1983; J e r n a k o f f , 1983; P e t r a i t i s , 1983; Underwood e t a l . , 1983). However, t h e r e have been no s t u d i e s w h i c h have d i r e c t l y e xamined t h e r e l a t i o n s h i p s between h e r b i v o r y and a l g a l p r o d u c t i v i t y . C u b i t (1974) s t u d i e d t h e h i g h i n t e r t i d a l community on t h e O regon c o a s t and c o n c l u d e d t h a t w h i l e h e r b i v o r y c o u l d l i m i t a l g a l a b u n d a n c e s , under t h e p r o p e r e n v i r o n m e n t a l c o n d i t i o n s a l g a l p r o d u c t i v i t y may be so g r e a t as t o "swamp" t h e h e r b i v o r e s , l i m i t i n g t h e i r i n f l u e n c e on community s t r u c t u r e . The r e s u l t s of o t h e r s t u d i e s s u g g e s t t h a t t h i s t y p e of phenomenon may be of more g e n e r a l o c c u r r e n c e ( C a s t e n h o l z , 1961; D a h l , 1964; D a y t o n , 1975; L u b c h e n c o , 1978, 1980; L u b c h e n c o and Menge, 1978; S o u s a , 1979b; L u b c h e n c o and G a i n e s , 1981; Hawkins and H a r t n o l l , 1983; J e r n a k o f f , 1983). C u b i t (1974) c o n c l u d e d t h a t b i o l o g i c a l i n t e r a c t i o n s , e s p e c i a l l y t h o s e between h e r b i v o r y and a l g a l p r o d u c t i v i t y , were t h e most i m p o r t a n t f a c t o r s c o n t r o l l i n g t h e abundance, and p o s s i b l y t h e s p e c i e s c o m p o s i t i o n , of o r g a n i s m s i n h i g h i n t e r t i d a l a r e a s . P h y s i c a l f a c t o r s i n f l u e n c e d t h e abundance of a l g a e by a f f e c t i n g t h e s e s p e c i e s i n t e r a c t i o n s . T h i s c h a p t e r p r e s e n t s t h e d a t a on t h e a b u n d a n c e s of t h o s e i n t e r t i d a l i n v e r t e b r a t e s w h i c h have been f o u n d by p r e v i o u s w o r k e r s t o be i m p o r t a n t i n f l u e n c e s on i n t e r t i d a l community s t r u c t u r e and t h u s may a l s o a f f e c t a l g a l p r o d u c t i v i t y . A l t h o u g h no f e e d i n g o r c a g i n g e x p e r i m e n t s were p e r f o r m e d , r e f e r e n c e t o p r e v i o u s work may a l l o w an 101 e s t i m a t i o n of t h e p o s s i b l e i m p a c t of h e r b i v o r y on a l g a l p r o d u c t i v i t y i n t h e s t u d y a r e a . The r e l a t i o n s h i p s between F u c u s d i s t i c h u s , s e c o n d a r y a l g a l s p e c i e s , and l i t t o r i n e s a r e examined u s i n g r e g r e s s i o n a n a l y s e s and a F u c u s d i s t i c h u s c l e a r i n g e x p e r i m e n t . Methods and M a t e r i a l s In c o n j u n c t i o n w i t h t h e s a m p l i n g p r o g r a m t o e s t i m a t e i n t e r t i d a l m a c r o a l g a l s t a n d i n g c r o p s ( s e e C h a p t e r 3 ) , t h e i n v e r t e b r a t e s p r e s e n t i n e a c h o f t h e q u a d r a t s sampled t o e s t i m a t e a l g a l s t a n d i n g c r o p s ( e x c e p t amphipods, b a r n a c l e s , and m u s s e l s ) were c o l l e c t e d and c o u n t e d . The main p u r p o s e of t h i s s a m p l i n g was t o o b t a i n some i d e a o f t h e p o s s i b l e e f f e c t s of h e r b i v o r y on a l g a l s t a n d i n g c r o p and p r o d u c t i v i t y , t h u s p a r t i c u l a r a t t e n t i o n was g i v e n t o t h e h e r b i v o r o u s g a s t r o p o d s ( l i t t o r i n e s a nd l i m p e t s ) . A l t h o u g h b a r n a c l e s and m u s s e l s may have i n f l u e n c e d a l g a l p r o d u c t i v i t y t h r o u g h c o m p e t i t i o n f o r s p a c e , f i l t e r i n g o f r e p r o d u c t i v e d i s s e m i n u l e s f r o m t h e water column, e t c . ( D a y t o n , 1971; N a s s i c h u k , 1975; Menge, 1976; Hawkins, 1981), t h e s e s p e c i e s i n t e r a c t i o n s were not examined. The method of c o l l e c t i n g i n v e r t e b r a t e s p r o v e d i m p r a c t i c a l f o r e s t i m a t i n g amphipod d e n s i t i e s and p r o b a b l y 102 s l i g h t l y u n d e r e s t i m a t e d t h e d e n s i t i e s of l i t t o r i n e s and l i m p e t s . S u b s t r a t u m h e t e r o g e n e i t y ( b a r n a c l e s , c r e v i c e s , e t c . ) and t h e c r y p t i c c o l o r a t i o n of t h e g a s t r o p o d s made i t i m p o s s i b l e t o c o l l e c t a l l t h e i n d i v i d u a l s i n e a c h q u a d r a t ( s e e D a y t o n , 1971). The i n v e r t e b r a t e d e n s i t i e s p r e s e n t e d s h o u l d t h e r e f o r e be v i e w e d as lo w e r t h a n t h e t r u e f i e l d v a l u e s , but as r e a l i s t i c e s t i m a t i o n s of t h e r e l a t i v e m a g n i t u d e of t h e s p e c i e s d e n s i t i e s a t t h e s t u d y s i t e s . D u r i n g t h e w i n t e r 1982-83 i t was o b s e r v e d t h a t b o t h l i t t o r i n e d e n s i t i e s and F u c u s d i s t i c h u s s t a n d i n g c r o p s were r e d u c e d i n c o m p a r i s o n w i t h t h e summer l e v e l s . T h i s a p p e a r e d t o be a " n a t u r a l c l e a r i n g " , and so t o e v a l u a t e t h e p o s s i b l e i n t e r a c t i o n s between F\_ d i s t i c h u s , l i t t o r i n e s and s e c o n d a r y a l g a l s p e c i e s when s p r i n g g r o w t h resumed, t h i s n a t u r a l s e a s o n a l d e c l i n e i n F ^ d i s t i c h u s and l i t t o r i n e s was m o d i f i e d . T h i s e x p e r i m e n t was d e s i g n e d t o t e s t i f t h e F. d i s t i c h u s c a n o p y a l l e v i a t e d d e s i c c a t i o n s t r e s s and was t h e r e f o r e an i m p o r t a n t i n f l u e n c e on l i t t o r i n e a b u n d a n c e s and t h e growth o f s e c o n d a r y m a c r o a l g a e i n t h e upper (Zones I and I I ) i n t e r t i d a l . In a d d i t i o n , c h a n g e s i n s p e c i e s p r e s e n c e / a b u n d a n c e o v e r t i m e a f t e r t h e c l e a r i n g e v e n t were s t u d i e d . E x p e r i m e n t a l 1 m2 p l o t s were e s t a b l i s h e d a t H a i n e s and W i z a r d i n F e b r u a r y 1983. Two p l o t s were c l e a r e d on e a c h s i d e of t h e s e t of t r a n s e c t s a t t h e s i t e s , a t v e r t i c a l l e v e l s a p p r o x i m a t e l y i n t h e m i d d l e of Zones I and I I ; t h e r e 1 0 3 were t h u s e i g h t e x p e r i m e n t a l p l o t s a t e a c h s i t e . A l l F. d i s t i c h u s and l i t t o r i n e s were removed from e a c h p l o t a s i l l u s t r a t e d i n F i g u r e 9. In t h e two c e n t r a l 25 cm x 25 cm (0.0625 m 2) q u a d r a t s , a l l t h e c a n o p y F ^ d i s t i c h u s was removed; i n one of t h e s e q u a d r a t s t h e u n d e r s t o r y F. d i s t i c h u s ( p l a n t s a p p r o x i m a t e l y 5 cm i n h e i g h t ) were a l s o removed ( T o t a l R e m o v a l ) , w h i l e t h e u n d e r s t o r y p l a n t s were l e f t i n t a c t i n t h e o t h e r q u a d r a t ( C a n o p y - O n l y R e m o v a l ) . These 25 cm x 25 cm q u a d r a t s , t o t a l l y u n i n f l u e n c e d by a F. d i s t i c h u s c a n o p y , were c o n s i d e r e d t h e " e x p e r i m e n t a l q u a d r a t s " and a l l q u a n t i t a t i v e measurements were made on t h e s e q u a d r a t s o n l y . D a t a on a l g a l s t a n d i n g c r o p and l i t t o r i n e d e n s i t i e s c o l l e c t e d d u r i n g t h e no r m a l s a m p l i n g p r o g r am were c o n s i d e r e d as c o n t r o l s . Growth and d e v e l o p m e n t of F\_ d i s t i c h u s and s e c o n d a r y a l g a l s p e c i e s , and i n v e r t e b r a t e a b u n d a n c e s , i n t h e e x p e r i m e n t a l q u a d r a t s were f o l l o w e d q u a l i t a t i v e l y f o r t h e n e x t s i x months. Q u a n t i t a t i v e d e t e r m i n a t i o n s of a l g a l s t a n d i n g c r o p and i n v e r t e b r a t e d e n s i t i e s were made on one-h a l f of t h e 1 m 2 e x p e r i m e n t a l p l o t s i n mid-June and on t h e o t h e r h a l f i n l a t e - J u l y . One of t h e 1 m2 p l o t s from e a c h s i d e and e a c h zone a t b o t h s t u d y s i t e s was sampled a t e a c h t i m e . The e x p e r i m e n t a l q u a d r a t s were sampl e d and a n a l y z e d as d e s c r i b e d i n C h a p t e r 3 f o r t h e m a c r o a l g a l s t a n d i n g c r o p s a m p l i n g p r o g r a m . Figure 9 Diagram of the 1 m experimental plo t s set up i n the Fucus d i s t i c h u s c l e a r i n g experiment. Hashed Area = cleared of a l l algae and invertebrates Experimental Quadrats (25 x 25 cm): T o t a l Clear = a l l algae and invertebrates removed Canopy Only = canopy |\_ d i s t i c h u s only and invertebrates removed; understory ]?\_ d i s t i c h u s l e f t i n t a c t 105 106 R e s u l t s E x c e p t f o r L i t t o r i n a s c u t u l a t a G o u l d and s i t k a n a P h i l i p p i ( h e r b v i v o r o u s g a s t r o p o d s ) , i n v e r t e b r a t e abundances a t e a c h s t u d y s i t e were r e l a t i v e l y low. L i m p e t s were f o u n d o n l y r a r e l y and were u s u a l l y s m a l l i n s i z e ( l e s s t h a n 10 mm i n l e n g t h ) . P a g u r u s h i r s u t i u s c u l u s Dana ( h e r m i t c r a b ) was f a i r l y common, but d e n s i t i e s a v e r a g e d l e s s t h a n 16 n r 2 . The g a s t r o p o d s T e g u l a f u n e b r a l i s Adams, T h a i s e m a r g i n a t a D e s h a y e s and T h a i s l a m e l l o s a G m e l i n were f o u n d s p o r a d i c a l l y i n Zones II and I I I . Amphipods were o f w i d e s p r e a d o c c u r r e n c e , but no a c c u r a t e e s t i m a t i o n o f t h e i r d e n s i t i e s was p o s s i b l e . T h r e e s p e c i e s were o b s e r v e d t o have somewhat l i m i t e d d i s t r i b u t i o n s . Amphissa c o l u m b i a n a D a l l ( g a s t r o p o d ) was u s u a l l y a s s o c i a t e d o n l y w i t h N eorhodomela l a r i x i n Zone I I I a t H a i n e s ( o v e r a l l mean d e n s i t y = 24 n r 2 ) . The s e a s t a r P i s a s t e r o c h r a c e u s B r a n d t was r a r e l y f o u n d a t t h e t h r e e s h e l t e r e d s i t e s , but was abu n d a n t i n Zones I I and I I I a t N u d i b r a n c h ( o v e r a l l mean d e n s i t y = 3.2 n r 2 ) . 'The c h i t o n K a t h a r i n a t u n i c a t a Wood was f o u n d o n l y i n Zones I I and I I I a t N u d i b r a n c h ( o v e r a l l mean d e n s i t y = 6.4 n r 2 ) . L i t t o r i n e s were abundant i n Zones I and I I of t h e s h e l t e r e d s i t e s and i n Zone I a t N u d i b r a n c h ( F i g u r e s I0a-d and 1 1 a - d ) . B o t h s p e c i e s of L i t t o r i n a were f o u n d a t e a c h 107 s i t e , but L_j_ s i t k a n a was v e r y abundant a t H a i n e s and r a r e a t W i z a r d . R e s u l t s of m u l t i - w a y a n a l y s e s of v a r i a n c e of l i t t o r i n e d e n s i t y o v e r s i t e , month and zone ( Z o n e s I and I I o n l y ) a r e p r e s e n t e d i n T a b l e s 17 and 18. The s i g n i f i c a n t two-way i n t e r a c t i o n terms were f u r t h e r a n a l y z e d u s i n g t h e r e s p e c t i v e one-way ANOVAs. The o n l y s i g n i f i c a n t s e a s o n a l c h a n g e s i n L ^ s i t k a n a abundance were, f o u n d a t H a i n e s ( T a b l e 17), but S-N-K a n a l y s i s ( p < 0 . 0 l ) d i d n o t d i v i d e t h e months i n t o p a r t i c u l a r l y w e l l - d e f i n e d g r o u p s . However, mean L_j_ s i t k a n a d e n s i t i e s were g r e a t e s t i n summer 1982. A l t h o u g h t h e Zone*Month i n t e r a c t i o n was s i g n i f i c a n t , n e i t h e r o f t h e Zones showed i n d i v i d u a l s e a s o n a l c h a n g e s i n L_;_ s i t k a n a d e n s i t y . At e a c h s i t e , s i t k a n a abundance was g r e a t e s t i n Zone I . The s i g n i f i c a n t S i t e * Z o n e i n t e r a c t i o n r e f l e c t e d t h e d i f f e r e n t d e n s i t i e s of s i t k a n a a t e a c h s i t e . I n c o n t r a s t w i t h L_;_ s i t k a n a , t h e o n l y n o n - s i g n i f i c a n t s e a s o n a l d i f f e r e n c e s i n s c u t u l a t a abundance were f o u n d a t H a i n e s ( T a b l e 1 8 ) . In g e n e r a l , s c u t u l a t a d e n s i t i e s were g r e a t e s t d u r i n g t h e summer months, but t h e s e d i f f e r e n c e s were not c l e a r l y d i s t i n g u i s h e d by S-N-K a n a l y s i s ( p < 0 . 0 l ) f o r t h e Zone*Month and N u d i b r a n c h * M o n t h i n t e r a c t i o n s . L i t t o r i n a s c u t u l a t a was most abundant i n Zone I a t e a c h s i t e but H e l b y . R e s u l t s o f t h e m u l t i p l e r e g r e s s i o n a n a l y s e s of l i t t o r i n e d e n s i t i e s on v a r i o u s a b i o t i c e n v i r o n m e n t a l f a c t o r s Figure 10 2 Mean d e n s i t i e s (number per 0.0625 m ± one standard deviation) of L i t t o r i n a sitkana i n Zones I and II at each study s i t e for each "sample month". A) Haines B) Helby C) Wizard • D) Nudibranch • = Zone I • = Zone II a) H a i n e s M o n t h o M o n t h M o n t h Figure 11 2 Mean d e n s i t i e s (number per 0.0625 m ± one standard deviation) of L i t t o r i n a scutulata in Zones I and II at each study s i t e for each "sample month". A) Haines B) Helby C) Wizard D) Nudibranch • = Zone 1 • = Zone II L . s c u t u l a t a ( N o . - 0 . 0 6 2 5 m ~ 2 ) M « w O O O J - i 1 • • M o n t h L . s c u t u l a t a ( N o . • 0 . 0 6 25 m " 2 ) ill T a b l e 17. A n a l y s i s of v a r i a n c e of L i t t o r i na s i tkana d e n s i t i e s (# 0.0625m-2) in Zones I and II a t the s tudy s i t e s SOURCE SUM OF SQUARES DF MEAN SQUARE F-RATIO PROBABILITY Si te Zone S i t e *Zone Month S i te*Month Zone*Month S*Z*M Res i dua1 T o t a l 22899 1822 1 9085.8 4813.9 16273 4269.4 12551 1 .5617E+05 2.4429E+05 3 1 3 9 25 9 24 840 914 7633 .0 1822 1 3028.6 534.87 650.92 474 . 38 522.98 185.92 41.055 98.007 16.290 2.8769 3.5011 2 . 5515 2.8129 0.00000 O.OOOOO 0.00000 .00237 .00000 .00678 .00001 O. 0. O. 0. I n t e r a c t i o n ANOVAs SOURCE DF MEAN SQUARE F-RATIO PROBABILITY Zone I*Month Zone I I *Month 9,424 9,471 916.00 58 .867 2.1030 0.85S91 0.02816 ns 0.56398 ns Ha i nes*Month He lby*Month Wizard*Month Nudib'r*Month 266 194 251 166 1946.9 119.52 28.187 403.70 1050 1803 6563 3307 0.00006 * * 0.30950 ns 0.10008 ns 0.23876 ns Ha ines *Zone He lby *Zone Wizard*Zone Nud i b r *Zone 1 , 274 1 ,202 1 , 259 1 , 172 1936.2 878.99 276.80 7350.0 42.673 8.9488 16.873 27.580 0.00000 * * 0.00312 * 0.00005 * * 0.00000 * * 00 T a b l e 18. A n a l y s i s of v a r i a n c e of L i t t o r i na s c u t u 1 a t a d e n s i t i e s O 0.0625m-2) in Zones I and II of the s tudy s i t e s . SOURCE SUM OF SQUARES DF MEAN SQUARE F-RATIO PROBABILITY S i te Zone S i t e *Zone Month S i t e * M o n t h Zone*Month S*Z*M Res i dua1 T o t a l 14772 17488 4790.4 10946 12491 3922 . 2 9826.9 1.1411E+05 1.8583E+05 3 1 3 9 25 9 25 838 913 4924 .0 17488 1596.8 1216.2 499 .62 435.80 393.08 136. 17 36. 160 128.42 11.726 8.9312 3.6691 3.2004 2.8866 0.00000 0.00000 00000 00000 00000 00081 00000 * * * * I n t e r a c t ion ANOVAs SOURCE DF MEAN SQUARE F-RATIO PROBABILITY Zone I*Month Zone I I *Month 9.423 9,471 1 100.00 466.60 5.0669 3.4474 0.00000 * * 0.00039 * * Ha ines*Month He lby*Month Wizard*Month Nudi br *Month 9,265 9, 194 9,254 7 , 166 231 . 12 924 . 18 127.64 191.16 5249 6518 0796 2421 0. 13901 ns 0.00031 * * 0.00000 * * 0.00299 * Ha i nes*Zone He lby*Zone Wi z a rd *Zone Nud ib r *Zone 1 , 273 1 , 202 1 , 259 1 , 172 3616.2 794.88 1603.0 2012.6 25.557 2.8359 89.005 37.984 0.00000 * * 0.09372 ns 0.00000 * * 0.00000 * * 120 ( s e e C h a p t e r 3) and F u c u s d i s t i c h u s s t a n d i n g c r o p a r e shown i n T a b l e 19. B o t h s p e c i e s show s i g n i f i c a n t r e g r e s s i o n s w i t h F. d i s t i c h u s b i o m a s s , but F ^ d i s t i c h u s s t a n d i n g c r o p was s i g n i f i c a n t o n l y i n t h e m u l t i p l e r e g r e s s i o n e q u a t i o n f o r L. s i t k a n a . Per c e n t t i m e e x p o s e d t o a i r has t h e h i g h e s t p a r t i a l c o r r e l a t i o n c o e f f i c i e n t s i n b o t h a n a l y s e s . The q u a n t i t a t i v e d a t a from t h e F\_ d i s t i c h u s c l e a r i n g e x p e r i m e n t ( b i o m a s s o f E\_ d i s t i c h u s and o t h e r m a c r o a l g a e , l i t t o r i n e d e n s i t i e s ) a r e p r e s e n t e d i n T a b l e 20. S e c o n d a r y s p e c i e s ( C l a d o p h o r a spp. , G i g a r t i n a p a p i l l a t a , e t c . ) were f o u n d o n l y r a r e l y i n t h e Zone I e x p e r i m e n t a l q u a d r a t s . The s t a n d i n g c r o p d a t a f o r t h e s e s p e c i e s were p r o b a b l y not t h e maximum t h e y a c h i e v e d , f o r some d y i n g back of t h e s e p l a n t s was o b s e r v e d d u r i n g t h e summer. R e s u l t s of ANOVAs of F. d i s t i c h u s s t a n d i n g c r o p and l i t t o r i n e d e n s i t i e s a r e p r e s e n t e d i n T a b l e s 21 and 22, r e s p e c t i v e l y . F u c u s d i s t i c h u s s t a n d i n g c r o p was g r e a t e s t a t W i z a r d and i n t h o s e e x p e r i m e n t a l q u a d r a t s where t h e u n d e r s t o r y p l a n t s were l e f t i n t a c t ( C a n o p y - O n l y R e m o v a l ) . T h e r e were no s i g n i f i c a n t z o n a l d i f f e r e n c e s i n F\ d i s t i c h u s b i o m a s s a t H a i n e s (F=0.24415 1,14df; P=0.62889ns), but F. d i s t i c h u s s t a n d i n g c r o p a t W i z a r d was g r e a t e s t i n Zone I I (F=12.733 1,14df; P=0.00309). F u c u s d i s t i c h u s b i o m a s s i n t h e c l e a r e d e x p e r i m e n t a l q u a d r a t s was much l e s s t h a n t h e c o n t r o l means. R e c o v e r y was g r e a t e r i n t h e C a n o p y - O n l y Removal t r e a t m e n t s , i n Zone I I , and a t W i z a r d ( T a b l e 2 0 ) . T a b l e 19 M u l t i p l e r e g r e s s i o n L i t t o r i na s c u t u 1 a t a env i r onmenta l f a c t o r s a n a l y s e s of L i t t o r i na s i t kana and d e n s i t i e s on s e l e c t e d a b i o t i c and Fucus d i s t i chus s t a n d i n g c r o p . MULTIPLE REGRESSIONS LSITKANA = - 4 . 7 - 1.1(H20-T) + O.OI(FUCUS) + 0.3(AIR EXP) MULTIPLE R = 0.68698 SE = 8.4281 P a r t i a l C o r r e l a t i o n C o e f f i c i e n t s : H20-T r = -0.29322 P=0.0112 FUCUS r = 0.46694 P=0.0000 AIR-EXP r = 0.61559 P=0.0000 LSCUTULATA = 33.4 - 1.2(SAL) - 1.1(WAVE EXP) + 0.2(AIR EXP) MULTIPLE R = 0.57521 SE = 7.8590 P a r t i a l C o r r e l a t i o n C o e f f i c i e n t s : SALINITY r = -0.03258 P=0.0047 WAVE-EXP r = -0.27383 P=0.0182 AIR-EXP r = 0.48808 P=0.0000 REGRESSIONS ON FUCUS DISTICHUS STANDING CROP ONLY LSITKANA = 0.6 + O.OI(FUCUS) r = 0.38253 1,74 df p<0.0006** SE LSCUTULATA = 5.0 + O.OKFUCUS) r = 0.32588 1,74 df p<0.0041** SE Note: L i t t o r i n e v a l u e s in numbers per 0.0625m' Fucus s t a n d i n g c r o p i n g d ry wt m~2 = 10.57 = 8.96 T a b l e 2 0 . F u c u s d i s t i c h u s c l e a r i n g e x p e r i m e n t , m a c r o a l g a l s t a n d i n g c r o p s ( g d r y * t m - 2 1 a n d l i t t o r i n e d e n s i t i e s ( » 0 . 0 6 2 5 m - 2 l D A T E T O T A L R E M O V A L C A N O P y - O N L ' R E M O V A L f u c u s O t h e r L 1 1 t o n n e s f u c u s O t h e r L i t t o r ; n e s Z O N E I W I z a r d / 1 3 J u n e 4 5 7 . 8 2 . 7 2 6 . 0 L e f t 6 7 1 6 . 0 2 7 3 2 5 1 0 5 5 R i g n t 2 1 6 1 . 0 7 6 7 8 0 2 1 % C o n t r o l 9 . 7 1 2 9 6 " 6 5 . 4 3 5 . 1 0 1 4 6 2 H a l n e s / 1 0 J u n e 9 8 6 5 1 8 5 2 3 6 L e t t 2 . 1 0 2 7 2 . 2 0 6 R i g h t 0 0 1 1 0 0 1 V . C o n t r o l 0 1 0 6 4 3 7 0 u 8 W i z a r d / 2 6 J u l y 5 5 9 7 2 8 3 8 2 L e f t 1 4 8 0 6 2 7 1 0 J R i g r i t 2 9 1 0 1 0 5 3 7 0 2 5 X C o n t r o l 3 . 9 0 2 0 9 7 2 0 3 8 0 H a i n e s / 2 2 J u l y 7 8 2 . 7 1 1 . 5 1 1 6 L e f t 0 0 0 3 7 5 0 4 R i g h t 1 6 4 0 3 2 1 8 . e 0 2 4 "I- C o n t r o l 0 8 0 1 2 9 16 . 0 1 2 0 7 ZONE 1J. W i z a r O / 1 3 J u n e 5 4 2 9 3 5 7 6 2 L e f t 1 2 9 . 5 6 . 0 2 4 8 1 . 9 2 7 R i g h t 1 4 8 4 3 5 2 10 3 4 0 7 2 1 7 X C o n t r o l 2 5 . 6 5 7 . 7 - • • 9 6 8 7 5 8 5 . 6 - • • 1 9 3 '. H a i n e s / 1 0 J u n e 7 7 8 . 3 1 3 . 6 1 7 . 6 L e f t 6 0 1 1 4 0 4 2 R i g h t 1 4 4 8 8 0 1 4 1 3 8 2 8 H C o n t r o l 1 , 3 3 6 0 * 2 8 1 1 7 3 7 . 5 - 31 3 W i z a r d / 2 6 J u l y 6 4 0 2 9 6 3 2 9 L e f t 2 0 4 7 0 7 3 9 2 0 0 3 7 R i g n t 2 1 7 2 1 6 . 5 3 0 3 2 0 0 1 5 5 2 'A C o n t r o l 3 3 0 8 . 6 - 6 3 7 9 5 5 6 8 0 * 6 7 2 J H e i n e s / 2 2 J u l y 7 2 4 8 7 0 10 7 L e f t 1 0 1 0 0 1 2 5 9 1 0 9 R I g h t 1 1 6 4 0 4 1 4 6 4 2 6 0 2 7 C o n t r o l 0 9 3 5 7 * « 18 7 18 8 1 9 2 9 * « 51 N o t e • C 1 a d o p n o r a s p p • • C r a d o p h p r a s p o . p a p i ) l a t a • • • C i a d o p n o r a s p p . p a p > M a t a  4 d i f f o r m i s . r c o r n u c o p i a e • + L d i f f Q r r n i s I C O r n u c o p 1 a e . 1 C O r n u c o p i a e , P o i y s i p n p n » a S P D . U _ f e n e s t r a t a C I a d o p n o r a s p p S _ l o m e n t a r i a T a b l e 21 Fucus d i s t i chus c l e a r i n g exper iment : A n a l y s i s o f Fucus d i s t i chus s t a n d i n g c rop (g d r y wt e x p e r i m e n t a l q u a d r a t s . of v a r i a n c e m-2) i n the SOURCE SUM OF SQUARES DF MEAN SQUARE F-RATIO PROBABILITY Si te Zone S i t e *Zone T i me S i t e * T i me Zone*T i me S*Z*T Remova1 S i te*Removal Zone*Remova1 S*Z*R T i me*Remova1 S*T*R Z*T*R S*T*Z*R Res i dua1 T o t a l .1 .2571E+05 97583 69294 58.590 1 1389 2375.3 7966.4 1.1375E+05 6157.7 1 1389 4600.8 2027.3 19459 104.04 215.80 71909 5.4399E+05 16 31 1.2571E+05 97583 69294 58.590 1 1389 2375 . 3 7966.4 1.1375E+05 6157.7 1 1389 4600.8 2027.3 19459 104.04 215.80 4494.3 27.972 21.713 15.418 .013037 2 . 5341 0. 52852. 1.7726 25.31 1 1.3701 2.5341 1.0237 0.45107 4.3297 .023149 .048017 0. O. O. 0. 0. 00007 * * 00026** 00120** 91052ns 13097ns 0.47773ns 0.20172ns 0 .00012* * O.25893ns 0.13097ns O.32670ns 0.51141ns 0.05388ns 0.88097ns 0.82932ns T a b l e 22. Fucus d i s t i c h u s c l e a r i n g expe r imen t : A n a l y s i s of v a r i a n c e of l i t t o r i n e d e n s i t i e s (# 0.0625m-2) i n the e x p e r i m e n t a l q u a d r a t s . SOURCE SUM OF SOUARES MEAN SOUARE F -RATIO PROBABILITY Si te 1225 . 1 1 1225 . 1 8 8099 0 00906* * Zone 98.OOO 1 98.000 0 70472 0 41357ns S i t e *Zone 28.125 1 28.125 0 20225 0 65895ns T ime 0 .0 1 0.0 0 0 1 OOOOOns S i t e * T i me 78.125 1 78.125 0 56180 0 46442ns Zone*T i me 242.00 1 242.00 1 7402 0 20568ns S*Z*T 465.12 1 465.12 3 3447 0 08612ns Removal 406 . 13 1 406.13 2 9204 0 10679ns S i te*Remova1 18.000 1 18.000 0 12944 0 72372ns Zone*Remova 1 9 1 . 125 1 91 . 125 0 65528 0 43011ns S*Z*R 24.500 1 24.500 0 17618 0 68026ns T i me*Remova1 15.125 1 15.125 0 10876 0 74583ns S*T*R 98.000 1 98.000 0 70472 0 42357ns Z*T*R 1.1250 1 1.1250 .0080899 0 92945ns S*T*Z*R 60.500 1 60.500 0 43506 0 51890ns Re s i dua l 2225.0 16 139.06 T o t a l 5076.0 31 125 The o n l y s i g n i f i c a n t d i f f e r e n c e i n l i t t o r i n e abundance was b e t w e e n - s i t e s ; d e n s i t i e s a t W i z a r d were g r e a t e r t h a n t h o s e a t H a i n e s ( T a b l e 2 0 ) . Compared w i t h t h e c o n t r o l means, l i t t o r i n e d e n s i t i e s were r e d u c e d a t H a i n e s i n a l l but t h e Zone I , 22 J u l y C a n o p y - O n l y Removal q u a d r a t . At W i z a r d , l i t t o r i n e a b u n d a n c e s were g r e a t e r i n t h e Zone II t r e a t m e n t s and i n t h e Zone I , 13 J une C a n o p y - O n l y Removal q u a d r a t , when compared w i t h c o n t r o l d e n s i t i e s . L i t t o r i n e d e n s i t i e s i n t h e T o t a l Removal q u a d r a t s were much r e d u c e d , w h i l e t h o s e i n t h e C a n o p y - O n l y Removal q u a d r a t s were not as low, and were o c c a s i o n a l l y g r e a t e r , t h a n t h e c o n t r o l means ( T a b l e 2 0 ) . D i s c u s s i o n Compared w i t h o t h e r i n t e r t i d a l c o m m u n i t i e s , i n v e r t e b r a t e d e n s i t i e s i n t h e B a m f i e l d a r e a were g e n e r a l l y much l o w e r . D a y t o n (1971) r e p o r t e d maximum l i m p e t ( Acmaea spp.) d e n s i t i e s of 680 i r r 2 and T h a i s s p p . d e n s i t i e s o f 400 n r 2 on t h e W a s h i n g t o n c o a s t ; b o t h l i m p e t s and t h a i d s were r a r e i n t h e s t u d y s i t e s . L i m p e t s were a l s o p r e s e n t i n low numbers i n New E n g l a n d ( L u b c h e n c o and Menge, 1978; L u b c h e n c o , 1980), but h i g h d e n s i t i e s of T h a i s l a p i l l u s have been r e p o r t e d (Menge 1976, 1978). In New S o u t h Wales, A u s t r a l i a , l i m p e t d e n s i t i e s ( C e l l a n a t r a m o s e r i c a ) were 126 between 65 and 86 irr 2 (Underwood and J e r n a k o f f , 1981; Underwood e t a l . , 1983). L i m p e t s were b o t h a bundant and l a r g e i n E n g l a n d , and have been shown t o be i m p o r t a n t s t r u c t u r i n g a g e n t s on E n g l i s h s h o r e s (Lodge, 1948; Burrows and Lodge,. 1950; Southward, 1964). L i m p e t s have been r e p o r t e d t o keep i n t e r t i d a l s u b s t r a t e s c l e a r of a l g a e , but o n l y when p r e s e n t i n d e n s i t i e s much h i g h e r t h a n t h o s e f o u n d i n t h i s s t u d y (Lodge, 1948; Borrows and Lodge, 1950; D a y t o n , 1971; Underwood, 1980; Underwood and J e r n a k o f f , 1981). C o n s i d e r i n g t h e i r s m a l l numbers, l i m p e t s and t h a i d s p r o b a b l y had o n l y a l i m i t e d i m pact on t h e i n t e r t i d a l community i n t h e s t u d y a r e a . S t e p h e n s o n and S t e p h e n s o n (1961a) a l s o s u g g e s t e d t h a t l i m p e t s were r e l a t i v e l y u n i m p o r t a n t on V a n c o u v e r I s l a n d s h o r e s . N a s s i c h u k (1975) o b s e r v e d P a g u r u s h i r s u t i u s c u l u s g r a z i n g on F u c u s i n t i d e p o o l s and low s h o r e l e v e l s . However, t h e s m a l l p o p u l a t i o n s (16 n r 2 ) of t h i s h e r m i t c r a b f o u n d a t t h e s t u d y s i t e s p r o b a b l y had o n l y a s m a l l impact on F. d i s t i c h u s s t a n d i n g c r o p l e v e l s . The l a c k o f E\ d i s t i c h u s i n Zone II a t N u d i b r a n c h may have been due t o p r e d a t i o n by P i s a s t e r o c h r a c e u s on b a r n a c l e s . F u c o i d s g e n e r a l l y s u r v i v e b e t t e r on uneven s u b s t r a t a ( s u c h as t h a t p r o v i d e d by b a r n a c l e s ) ; t h u s t h e l a c k of b a r n a c l e s i n t h i s zone, combined w i t h t h e p r e s e n c e of t h e " a l g a l t u r f " , may have l i m i t e d F\ d i s t i c h u s g r o w t h ( s e e N a s s i c h u k , 1975). However, 127 t h e low s t a n d i n g c r o p and s m a l l s t a t u r e of t h e p l a n t s i n N u d i b r a n c h / Z o n e I s u g g e s t e d t h a t wave a c t i o n a l s o had an i m p o r t a n t e f f e c t on E\_ d i s t i c h u s g r o w t h a t t h a t s i t e . D a y t o n (1975) r e p o r t e d s i m i l a r d e n s i t i e s of K a t h a r i n a  t u n i c a t a as f o u n d n e a r B a m f i e l d , and a l s o c o n c l u d e d t h a t t h i s h e r b i v o r e had l i t t l e e f f e c t on m a c r o a l g a e due t o t h e a b i l i t y o f t h e a l g a e t o "swamp" t h e a n i m a l s . A l t h o u g h no e x p e r i m e n t s s t u d y i n g t u n i c a t a g r a z i n g were p e r f o r m e d i n t h i s s t u d y , b a s e d on D a y t o n ( 1 9 7 5 ) , t h i s h e r b i v o r e p r o b a b l y had o n l y a s m a l l i mpact on t h e m a c r o a l g a l a s s e m b l a g e s i n Zones II and I I I a t N u d i b r a n c h . The o n l y i n v e r t e b r a t e s p r e s e n t i n l a r g e numbers were t h e h e r b i v o r o u s g a s t r o p o d s L i t t o r i n a s c u t u l a t a and L. s i t k a n a . L i t t o r i n e d e n s i t i e s were h i g h l y v a r i a b l e and showed s i g n i f i c a n t d i f f e r e n c e s between s i t e s and z o n e s , and s e a s o n a l l y ; s i g n i f i c a n t i n t e r a c t i o n terms were a l s o o b s e r v e d ( T a b l e s 17 and 18). The o b s e r v e d d e n s i t i e s were s i m i l a r t o t h o s e f o u n d by B e h r e n s (1971) f o r V a n c o u v e r I s l a n d and B e r t n e s s e t a l . (1983) i n New E n g l a n d . L u b c h e n c o (1980) r e p o r t e d c o m b i n e d t o t a l l i t t o r i n e d e n s i t i e s o f 2100-8000 nr 2 , 4-847 n r 2 , and 1-649 n r 2 i n t h e h i g h , mid, and low i n t e r t i d a l , r e s p e c t i v e l y , on New E n g l a n d s h o r e s . A v e r a g e d e n s i t i e s o f L i t t o r i n a 1 i t t o r e a L. on Long I s l a n d s h o r e s were 4000 n r 2 ( P e t r a i t i s , 1983). Lower l i t t o r i n e d e n s i t i e s have been f o u n d i n t i d e p o o l s i n W a s h i n g t o n (maximum d e n s i t y = 225 n r 2 ; D e t h i e r , 1982), i n a New 1 2 8 H a m p s h i r e e s t u a r y (maximum d e n s i t y = 155 m"2; H a r d w i c k -Witman and M a t h i e s o n , 1983), and i n t h e S t r a i t o f G e o r g i a (maximum d e n s i t y = 300 rn"2; N a s s i c h u k , 1975). E x c e p t f o r s c u t u l a t a a t H e l b y , l i t t o r i n e s were most ab u n d a n t i n Zone I a t e a c h s i t e . The l a c k o f a s i g n i f i c a n t L. s c u t u l a t a z o n a l d i f f e r e n c e a t H e l b y may have been due t o l o g damage i n Zone I d u r i n g t h e f a l l and w i n t e r ( s e e C h a p t e r 2 ) . B e h r e n s (1971) r e p o r t e d l i t t l e d i f f e r e n t i a t i o n i n t h e v e r t i c a l z o n a t i o n of s c u t u l a t a and s i t k a n a , but on e x p o s e d c o a s t s i t a p p e a r e d t h a t L ^ s i t k a n a was more abundant i n t i d e p o o l s ( B e h r e n s , 1971; McCormack, 1981). Chow (1975) and R i g g and M i l l e r (1949) n o t e d t h a t L ^ s c u t u l a t a and L. s i t k a n a i n h a b i t a r e a s between 1.0 and 4.9 m above MLLW, w i t h maximum d e n s i t i e s o f s c u t u l a t a a t a b o u t + 2.1-2.3 m (Chow, 1975). T h i s l e v e l was s l i g h t l y l o w e r t h a n t h e h e i g h t s o f maximum l i t t o r i n e d e n s i t y f o u n d i n t h i s s t u d y (Zone I began a t +2.4 o r +2.8 m; T a b l e 3 ) . L i t t o r i n e d e n s i t i e s may have been r e l a t e d t o t h e p r e s e n c e of a F u c u s d i s t i c h u s c a n o p y , w h i c h r e d u c e s d e s i c c a t i o n and p r e d a t i o n s t r e s s . The r e s u l t s from t h e F. d i s t i c h u s c l e a r i n g e x p e r i m e n t ( T a b l e 20) show t h a t l i t t o r i n e d e n s i t i e s were r e d u c e d a t H a i n e s and i n Zone I a t W i z a r d i n t h e a b s e n c e o f a F\_ d i s t i c h u s c a n o p y , b u t were g r e a t e r t h a n t h e c o n t r o l s i n t h e W i z a r d / Z o n e II e x p e r i m e n t a l q u a d r a t s . T h i s s u g g e s t e d t h a t a F ^ d i s t i c h u s c a n o p y may have a l l e v i a t e d d e s i c c a t i o n s t r e s s a t H a i n e s and i n 129 W i z a r d / Z o n e I , but was d e t r i m e n t a l t o l i t t o r i n e s i n Zone II a t t h e more wave-exposed W i z a r d s i t e ( p e r h a p s due t o an a l g a l " w h i p l a s h " e f f e c t ) . W h i l e l i t t o r i n e d e n s i t i e s i n Zone I were c o n s i s t e n t l y g r e a t e r t h a n i n Zone I I , c h a n g e s i n abundance a l o n g t h e wave e x p o s u r e g r a d i e n t were n o t as c l e a r . T h i s c an b e s t be seen by n o t i n g t h e r e s u l t s o f S-N-K a n a l y s i s ( p < 0 . 0 l ) f o r t h e S i t e * Z o n e i n t e r a c t i o n t e r m : L i t t o r i n a s c u t u l a t a WIZ-I,HELBY-I > HEL-II,HAIN-I > NUD-I,HAIN~II,WIZ-II,NUD-II L i t t o r i n a s i t k a n a HAIN-I > NUD-I,HEL-I > HAIN-11,HEL-11 > > WIZ-I > WIZ-II,NUD-II B o t h s p e c i e s showed l o w e r a b u n d a n c e s i n Zone II w i t h i n c r e a s i n g wave e x p o s u r e ; however, t h e p a t t e r n i n Zone I d i f f e r e d . L i t t o r i n a s c u t u l a t a d e n s i t i e s were g r e a t e s t on s h o r e s of moderate e x p o s u r e ( H e l b y , W i z a r d ) , w h i l e L. s i t k a n a a b u ndances were g r e a t e s t on. t h e most e x p o s e d ( N u d i b r a n c h ) and t h e most s h e l t e r e d ( H a i n e s ) s h o r e s . B e h r e n s (1971) f o u n d t h a t as wave e x p o s u r e i n c r e a s e d , t h e r a t i o of L ^ s c u t u l a t a t o U s i t k a n a d e n s i t i e s a l s o i n c r e a s e d . She a t t r i b u t e d t h i s r e s u l t t o t h e g r e a t e r a b i l i t y o f L_j_ s c u t u l a t a t o w i t h s t a n d t h e p o u n d i n g of waves. In a d d i t i o n , L. s i t k a n a was most abundant on s h e l t e r e d , 1 3 0 damp b e a c h e s w i t h many c r e v i c e s . I n t h i s s t u d y , s i t k a n a was most abundant a t H a i n e s , a s h e l t e r e d and v e r y b r o k e n s h o r e , i n agreement w i t h B e h r e n s ' (1971) o b s e r v a t i o n s . However, r e l a t i v e l y l a r g e L_;_ s i t k a n a p o p u l a t i o n s were a l s o f o u n d a t t h e most e x p o s e d s i t e ( N u d i b r a n c h ) . The i n v e r s e r e l a t i o n s h i p s i n s c u t u l a t a and L. s i t k a n a a b u n d a n c e s o b s e r v e d i n Zone I o f t h i s s t u d y s u g g e s t t h e p o s s i b i l i t y of c o m p e t i t i o n between t h e s e two s p e c i e s . T h e i r c o e x i s t e n c e and low numbers i n Zone I I i n d i c a t e t h a t t h i s s h o r e l e v e l i s l e s s h o s p i t a b l e t o t h e s e g a s t r o p o d s , and t h u s c o m p e t i t i o n p r o b a b l y does not o c c u r b e c a u s e t h e s n a i l p o p u l a t i o n s a r e s m a l l . Where s e a s o n a l c h a n g e s were o b s e r v e d , t h e r e was a r e l a t i v e l y l a r g e d e c r e a s e i n l i t t o r i n e d e n s i t i e s i n t h e f a l l and w i n t e r . S i m i l a r w i n t e r d e c l i n e s i n l i t t o r i n e a b u n dances have been r e p o r t e d by C a s t e n h o l z ( 1 9 6 1 ) , N a s s i c h u k ( 1 9 7 5 ) , L u b c h e n c o and C u b i t ( 1 9 8 0 ) , D e t h i e r (1982) and B e r t n e s s e t a l . ( 1 9 8 3 ) . T h e s e l o w e r d e n s i t i e s may be t h e r e s u l t of t h e d i s l o d g e m e n t of t h e l i t t o r i n e s due t o i n c r e a s e d wave a c t i o n o r because^ t h e g a s t r o p o d s a r e l e s s a c t i v e i n t h e w i n t e r ( C a s t e n h o l z , 1961; N a s s i c h u k , 1975; B e r t n e s s e t a l . , 1983). Mean l i t t o r i n e d e n s i t i e s d u r i n g t h e spring/summer 1983 were somewhat l o w e r t h a n i n t h e summer 1982. In c o n j u n c t i o n w i t h s i m i l a r o b s e r v a t i o n s o f a l g a l s t a n d i n g c r o p ( s e e C h a p t e r 3 ) , t h i s s u p p o r t s t h e h y p o t h e s i s t h a t some g e n e r a l c l i m a t i c c o n d i t i o n d u r i n g t h e w i n t e r / e a r l y - s p r i n g 1983 was 131 d e l e t e r i o u s t o t h e i n t e r t i d a l community. In e v a l u a t i n g t h e p o s s i b l e e f f e c t s of l i t t o r i n e g r a z i n g on m a c r o a l g a e , d a t a were o b t a i n e d f r o m two s o u r c e s : 1) P r e v i o u s s t u d i e s of l i t t o r i n e g r a z i n g , and 2) The F_j_ d i s t i c h u s c l e a r i n g e x p e r i m e n t p e r f o r m e d i n t h i s s t u d y . A l t h o u g h no d i r e c t ' e x p e r i m e n t a l m a n i p u l a t i o n s ( c a g i n g or e x c l o s u r e e x p e r i m e n t s ) were p e r f o r m e d , i n p a r t b e c a u s e of t h e p o s s i b l e i n t e r a c t i o n s w i t h t h e F\ d i s t i c h u s canopy, some c o n c l u s i o n s c an be made w i t h t h e a v a i l a b l e i n f o r m a t i o n . P r e v i o u s s t u d i e s have f o u n d t h a t b o t h L ^ s i t k a n a and L. s c u t u l a t a e a t t h e same t y p e s of a l g a e , m a i n l y d i a t o m s , U l v a , C l a d o p h o r a , P o r p h y r a , e t c . ( C a s t e n h o l z , 1961; D a h l , 1964; F o s t e r , 1964; B e h r e n s , 1971). In a d d i t i o n , L. s c u t u l a t a has been o b s e r v e d t o e a t f l e s h i e r a l g a e , s u c h as P e l v e t i a , L a m i n a r i a , and F u c u s , u n d e r l a b o r a t o r y c o n d i t i o n s ( D a h l , 1964; D e t h i e r , 1982). Thus, t h e s e s p e c i e s may a f f e c t t h e dom i n a n t s p e c i e s ( F\_ d i s t i c h u s ) as w e l l as s e c o n d a r y and e p h e m e r a l a l g a e . E c o l o g i c a l s t u d i e s i n t h e P a c i f i c N o r t h w e s t have shown t h a t l i t t o r i n e s a r e a b l e t o r e d u c e a l g a l s t a n d i n g c r o p s , but o n l y when p r e s e n t i n h i g h d e n s i t i e s and under f a v o r a b l e e n v i r o n m e n t a l c o n d i t i o n s . C a s t e n h o l z (1961) c o n c l u d e d t h a t 132 l i t t o r i n e d e n s i t i e s o f 300 irr 2 were c a p a b l e of p r e v e n t i n g t h e a p p e a r a n c e of a d i a t o m c o v e r i n h i g h i n t e r t i d a l a r e a s d u r i n g t h e summer. In t h e f a l l and w i n t e r , however, h i g h l i t t o r i n e d e n s i t i e s had l i t t l e e f f e c t on t h e d i a t o m c o v e r . D a h l (1964) s t a t e d t h a t s c u t u l a t a was a b l e t o p r e v e n t s p a r s e a l g a l p o p u l a t i o n s from i n c r e a s i n g , but had l i t t l e e f f e c t on e s t a b l i s h e d p o p u l a t i o n s . S i m i l a r r e s u l t s f o r t h e h i g h i n t e r t i d a l i n Oregon were f o u n d by C u b i t ( 1 9 7 4 ) . L i t t o r i n e d e n s i t i e s o f 930 r r r 2 ( t w i c e f i e l d v a l u e s ) p r e v e n t e d t h e g r o w th of m a c r o a l g a e on a s h e l t e r e d b e a c h , but n o r m a l (465 n r 2 ) d e n s i t i e s d i d not ( B e h r e n s , 1971). In New E n g l a n d , L u b c h e n c o (1978) c o n c l u d e d t h a t t h e p e r e n n i a l f u c o i d s were l e a s t a t t r a c t i v e t o l i t t o r i n e h e r b i v o r e s , and t h u s l i t t l e a f f e c t e d by t h e s e g a s t r o p o d s . However, L i t t o r i n a l i t t o r e a and L ^ o b t u s a t a r e a d i l y f e d upon E n t e r o m o r p h a and e p h e m e r a l a l g a e . P e t r a i t i s (1983) c o n c l u d e d t h a t low d e n s i t i e s o f L ^ 1 i t t o r e a c o u l d keep b a r e a r e a s c l e a r of E n t e r o m o r p h a , but h i g h e r d e n s i t i e s were r e q u i r e d t o e l i m i n a t e e s t a b l i s h e d p o p u l a t i o n s of t h e a l g a . S i m i l a r o b s e r v a t i o n s were made by L u b c h e n c o and Menge (1978) and L u b c h e n c o ( 1 9 8 0 ) . A l t h o u g h B e r t n e s s e t a l . (1983) d i d n o t d i r e c t l y s t u d y t h e e f f e c t s of h e r b i v o r y by L ^ 1 i t t o r e a on F u c u s , t h e y d i d o b s e r v e t h a t a l l e r e c t a l g a e were removed by heavy g r a z i n g p r e s s u r e on a s h e l t e r e d r o c k y b e a c h ( F u c u s was n o t abundant a t t h e s i t e ) . C h e m i c a l a n a l y s i s of. F u c u s e x t r a c t s have shown t h a t t h e p l a n t s c o n t a i n p o l y p h e n o l s , 133 w h i c h s e r v e a s a h e r b i v o r e d e f e n s e mechanism ( G e i s s e l m a n and M c C o n n e l l , 1981). I t t h u s a p p e a r s t h a t l i t t o r i n e s have o n l y a l i m i t e d impact on p e r e n n i a l f u c o i d s , but c a n l i m i t t h e a b u n d a n c e s of s e c o n d a r y and e p h e m e r a l s p e c i e s . However, i t s h o u l d be n o t e d t h a t Schonbeck and N o r t o n (1980) o b s e r v e d heavy l i t t o r i n e g r a z i n g on F u c u s s p i r a l i s , s u c h t h a t t h e l i n e a r g r o w t h r a t e of t h e p l a n t s was m e a s u r a b l y r e d u c e d . B a s ed on t h e s e s t u d i e s , t h e o b s e r v e d l i t t o r i n e d e n s i t i e s a t t h e s t u d y s i t e s were p r o b a b l y n ot h i g h enough t o l i m i t t h e g r o w t h o f m a c r o a l g a e . The one e x c e p t i o n t o t h i s w ould be i n Zone I a t H a i n e s d u r i n g t h e summer 1982, when l i t t o r i n e d e n s i t i e s e x c e e d e d 1000 n r 2 . H e r b i v o r e s a l m o s t c e r t a i n l y had o n l y a s m a l l e f f e c t on t h e m a c r o a l g a e d u r i n g t h e w i n t e r months; however, t h e combi n e d e f f e c t s of l i t t o r i n e g r a z i n g and d e s i c c a t i o n / h e a t s t r e s s , e t c . may have l i m i t e d a l g a l p r o d u c t i v i t y d u r i n g t h e summer. S e c o n d a r y a l g a l s p e c i e s were l e a s t a b u n d a n t i n Zone I a t e a c h s i t e ( s e e C h a p t e r 3 ) , where b o t h l i t t o r i n e g r a z i n g and p h y s i c a l s t r e s s e s were m a x i m a l . The r e s u l t s o f t h e d i s t i c h u s c l e a r i n g e x p e r i m e n t s u g g e s t t h a t d e s i c c a t i o n s t r e s s l i m i t s t h e a b u n d a n c e s o f b o t h l i t t o r i n e s and s e c o n d a r y m a c r o a l g a e i n t h e upper i n t e r t i d a l i n t h e a b s e n c e of a F\_ d i s t i c h u s c a n o p y . However, t h e s e s p e c i e s showed b i o m a s s i n c r e a s e s i n th e s p r i n g and summer, d e s p i t e t h o s e f a c t o r s o p e r a t i n g t o r e d u c e s t a n d i n g c r o p s , so t h a t e s c a p e s from g r a z i n g and p h y s i c a l s t r e s s were p o s s i b l e . CHAPTER 5 - DIVERSITY OF THE MACROALGAE 134 E c o l o g y has been d e f i n e d a s " t h e s c i e n t i f i c s t u d y o f t h e i n t e r a c t i o n s t h a t d e t e r m i n e t h e d i s t r i b u t i o n and abundance of o r g a n i s m s " ( K r e b s , 1978). I m p l i c i t i n t h i s d e f i n i t i o n i s t h e c o n c e p t of s p e c i e s d i v e r s i t y , by w h i c h i s meant a q u a n t i t a t i v e measure o f b o t h s p e c i e s p r e s e n c e ( r i c h n e s s ) and r e l a t i v e abundance ( H u r l b u r t , 1971). A number of i n d i c e s have been u s e d t o q u a n t i f y t h i s p r o p e r t y of c o m m u n i t i e s and e c o s y s t e m s ( r e v i e w e d by P e e t , 1974), however t h e r e have been v e r y few f i e l d s t u d i e s w h i c h have examined t h e d i v e r s i t y of e n t i r e c o m m u n i t i e s ( M i l l e r , 1982). The r o c k y i n t e r t i d a l s y s t e m i s amenable t o s t u d y i n g p a t t e r n s of s p e c i e s d i v e r s i t y . V e r t i c a l g r a d i e n t s i n t i d a l e m e r s i o n and h o r i z o n t a l g r a d i e n t s of wave e x p o s u r e a r e f o u n d w i t h i n narrow g e o g r a p h i c a l l i m i t s , p e r m i t t i n g t h e c o m p a r i s o n of a wide range o f h a b i t a t s . In a d d i t i o n , s u c c e s s i o n a l s e q u e n c e s , w h i c h c a n be i m p o r t a n t i n m a i n t a i n i n g s p e c i e s d i v e r s i t y ( e . g. S o u s a , 1979b), a r e g e n e r a l l y " c o m p l e t e d " i n a s h o r t t i m e ( f i v e t o t e n y e a r s ) . D e s p i t e t h e s e a d v a n t a g e s , few w o r k e r s have examined t h e d i v e r s i t y of i n t e r t i d a l m a c r o a l g a l c o m m u n i t i e s (Foreman, 1977; N e i l l , 1977; L u b c h e n c o , 1978; S o u s a , I 9 7 9 a b ) . 135 Sousa ( 1 9 7 9 a ) , w o r k i n g i n an i n t e r t i d a l b o u l d e r f i e l d i n C a l i f o r n i a , f o u n d e v i d e n c e s u p p o r t i n g H u s t o n ' s (1979) " g e n e r a l h y p o t h e s i s of s p e c i e s d i v e r s i t y . " The s t a t u s of t h e a l g a l a s s e m b l a g e a l o n g a l i n e o f s u c c e s s i o n was r e l a t e d t o t h e f r e q u e n c y w i t h w h i c h t h a t a s s e m b l a g e was d i s t u r b e d . I n t e r m e d i a t e f r e q u e n c i e s of d i s t u r b a n c e m a i n t a i n e d h i g h l e v e l s of b o t h i n t r a - and i n t e r - p a t c h d i v e r s i t y . H e r b i v o r e s had l i t t l e e f f e c t i n t h i s s y s t e m , due t o t h e i r low numbers and t h e a b i l i t y of t h e a l g a e t o "swamp" them w i t h p r o p a g u l e s ( S o u s a , 1979b). D a t a on t h e s p e c i e s r i c h n e s s and d i v e r s i t y of t h e i n t e r t i d a l m a c r o a l g a l a s s e m b l a g e s a t e a c h s t u d y s i t e , b a s e d on t h e s t a n d i n g c r o p d a t a p r e s e n t e d i n C h a p t e r 3, a r e d i s c u s s e d i n t h i s c h a p t e r . M u l t i p l e r e g r e s s i o n and c l u s t e r a n a l y s e s a r e a l s o p e r f o r m e d t o a s s i s t i n r e l a t i n g t h e o b s e r v e d p a t t e r n s o f d i v e r s i t y t o v a r i o u s e n v i r o n m e n t a l f a c t o r s . Methods and M a t e r i a l s Two d i v e r s i t y i n d i c e s , i n a d d i t i o n t o s p e c i e s r i c h n e s s (S, t h e number o f s p e c i e s p r e s e n t i n t h e c o l l e c t i o n s ) , c a l c u l a t e d on t h e b a s i s of t h e a l g a l s t a n d i n g c r o p d a t a (g d r y wt" 1 m" 2) p r e s e n t e d i n C h a p t e r 3 (Wilhm, 1968; P e e t , 136 1974), were u s e d t o d e s c r i b e t h e a l g a l a s s e m b l a g e s i n e a c h zone of t h e s t u d y s i t e s f o r e a c h s i x - w e e k s a m p l i n g i n t e r v a l : 1) Shannon-Weaver (1963) measure o f i n f o r m a t i o n c o n t e n t , e x p r e s s e d as e x p ( H ' ) , where H' = - £ _ p ( i ) [ l o g p ( i ) ] 2) The r e c i p r o c a l of S impson's Index, 1/q, where q = p ( i = 1 ) 2 + p ( 1 = 2 ) 2 + ... + p ( i = s ) 2 p ( i ) = t h e p r o p o r t i o n of t h e t o t a l a l g a l b i o m a s s f o r e a c h s i t e - z o n e - t i m e c o l l e c t i o n a c c o u n t e d f o r by s p e c i e s i . The Shannon-Weaver Index, e x p ( H ' ) , i s a Type I i n d e x , s e n s i t i v e t o t h e p r e s e n c e of r a r e s p e c i e s , w h i l e 1/q i s a Type I I i n d e x and i s s e n s i t i v e t o t h e more common s p e c i e s ( P e e t , . 1974) . The use o f b o t h i n d i c e s p r o v i d e s some measure f o r e s t i m a t i n g t h e i m p o r t a n c e of b o t h t h e r a r e and common s p e c i e s i n t h e a l g a l a s s e m b l a g e s . M u l t i p l e r e g r e s s i o n a n a l y s e s ( b a c k w a r d , s t e p w i s e ; MIDAS) o f S, e x p ( H ' ) , and 1/q on s e l e c t e d a b i o t i c e n v i r o n m e n t a l f a c t o r s ( s e e C h a p t e r 2) were p e r f o r m e d . A c l u s t e r a n a l y s i s on a " r e d u c e d " v e r s i o n of t h e s t a n d i n g c r o p d a t a m a t r i x was a l s o p e r f o r m e d . The c l u s t e r a l g o r i t h m was a p o l y t h e t i c a l minimum v a r i a n c e p r o c e d u r e u s i n g a E u c l i d e a n d i s t a n c e measure (MIDAS:MINVAR; Fox and G u i r e , 1976). O n l y t h o s e s p e c i e s whose b i o m a s s were 1% o r 137 g r e a t e r of t h e t o t a l a l g a l b i o m a s s ( d r y w e i g h t ) i n e a c h s i t e - z o n e - t i m e c o l l e c t i o n and f o u n d i n two o r more o f t h e sampled q u a d r a t s i n e a c h zone were u s e d ( C l i f f o r d and S t e p h e n s o n , 1975; F i e l d e t a l . , 1982). T h i s r e s u l t e d i n a " w o r k i n g " m a t r i x o f 23 s p e c i e s and 108 s i t e - z o n e - t i m e c o l l e c t i o n s . In a d d i t i o n , s t a n d i n g c r o p v a l u e s were r o u n d e d o f f t o two s i g n i f i c a n t f i g u r e s . T h i s d a t a " r e d u c t i o n " s i m p l i f i e d t h e c l u s t e r a n a l y s i s and r e d u c e d t h e " n o i s e " p r e s e n t i n t h e o r i g i n a l d a t a m a t r i x . The a n a l y s i s was t h u s more de p e n d e n t on c o n c u r r e n t s p e c i e s p r e s e n c e as o p p o s e d t o c o n c u r r e n t s p e c i e s a b s e n c e ( C l i f f o r d and S t e p h e n s o n , 1975). The a l g a l s t a n d i n g c r o p d a t a c o l l e c t e d a t B e a l e d u r i n g t h e summer 1983 i s a l s o p r e s e n t e d i n t h i s c h a p t e r . B e c a u s e of t h e rough w o r k i n g c o n d i t i o n s , d a t a a r e a v a i l a b l e o n l y f o r t h e t o p two m e t e r s of t h e B e a l e t r a n s e c t . An a c c u r a t e e s t i m a t i o n o f t i d a l h e i g h t s was not p o s s i b l e . Two ra n d o m l y s e l e c t e d 25 x 25 cm (0.0625 m 2) q u a d r a t s were sampled a l o n g e a c h meter of t h e t r a n s e c t d u r i n g b o t h v i s i t s t o t h e s i t e (16 J u l y and 15 A u g u s t 1983). The samples were c o l l e c t e d and a n a l y z e d as d e s c r i b e d i n C h a p t e r 3. 138 R e s u l t s A l g a l s t a n d i n g c r o p and d i v e r s i t y d a t a f o r B e a l e a r e p r e s e n t e d i n T a b l e 23. The a r e a s t u d i e d was d o m i n a t e d by P o s t e l s i a p a l m a e f o r m i s , w i t h C o r a l l i n a s pp. , Hymenena sp. , and Neorhodomela l a r i x as p r o m i n e n t " s e c o n d a r y " s p e c i e s . The s t a t u r e of N_^_ l a r i x was s i m i l a r t o t h a t o f t h e p l a n t s c o l l e c t e d a t N u d i b r a n c h ( s e e C h a p t e r 3 ) . Lower l e v e l s of t h e s h o r e were d o m i n a t e d by A l a r i a s p . , but no c o l l e c t i o n s were made from t h i s a r e a . T h e r e a p p a r e n t l y were o n l y two w e l l d i s t i n g u i s h e d z o n e s a t B e a l e . S p e c i e s r i c h n e s s (S) and d i v e r s i t y [ e x p ( H ' ) and 1/q] f o r e a c h s t u d y s i t e a r e p r e s e n t e d i n F i g u r e s 12-15. The l a r g e s t v a l u e s o f S, exp(H') and 1/q were f o u n d a t N u d i b r a n c h / Z o n e I I , w h i l e t h e l o w e s t v a l u e s were o b s e r v e d i n Zone I of H a i n e s , H e l b y , and W i z a r d . L i t t l e s e a s o n a l change i n t h e d i v e r s i t y v a l u e s was o b s e r v e d f o r Zones I and I I of the s h e l t e r e d s i t e s and Zones I and I I I a t N u d i b r a n c h . However, c o m p a r a t i v e l y w i d e r f l u c t u a t i o n s i n s p e c i e s r i c h n e s s o c c u r r e d i n t h e s e a s s e m b l a g e s . Zone I I a t N u d i b r a n c h and Zone I I I a t H a i n e s , H e l b y , and W i z a r d showed the l a r g e s t s e a s o n a l f l u c t u a t i o n s i n t h e d i v e r s i t y v a l u e s . In g e n e r a l , t h e z o n a l and s e a s o n a l p a t t e r n s of d i v e r s i t y were s i m i l a r a t H a i n e s , H e l b y , and W i z a r d , w h i l e N u d i b r a n c h showed d i f f e r e n t p a t t e r n s . S, 1/q and exp(H') 139 T a b l e 23. M a c r o a l g a l s t a n d i n g c r o p and d i v e r s i t y  d a t a f o r Cape B e a l e i n t h e summer 1983. SPECIES MEAN STANDING CROP* P o s t e l s i a p a l m a e f o r m i s 730.5 (485.2) Neorhodomela l a r i x 53.9 (115.3) Hymenena sp. 22.5 (38.0) C o r a l l i n a V a n c o u v e r i e n s i s 15.6 I r i d a e a c o r d a t a 12.6 C o r a l l i n a o f f i c i n a l i s 8.5 A l a r i a s p . 6.0 M i c r o c l a d i a b o r e a l i s 1.9 P o l y s i p h o n i a s p . 0.3 E n d o c l a d i a m u r i c a t a 0.3 P r i o n i t i s l a n c e o l a t a 0.3 S = 1 1 exp(H) = 1.90 1/q = 1 . 3 5 N o t e : * g d r y wt m~2 ( s t a n d a r d d e v i a t i o n ) Figure 12 Species richness and d i v e r s i t y of the i n t e r t i d a l macroalgae at Haines for each six-week sampling i n t e r v a l . A) Species richness B) exp (H') C) 1/q 9 = Zone I • = Zone 11 A - Zone III 141 A - H a i n e s • 2 J n S ~~T~ N T P J a Month 1 M — I Ap M y ~1— J n A Figure 13 Species richness and d i v e r s i t y of the i n t e r t i d a l macroalgae at Helby for each six-week sampling i n t e r v a l . A) Species richness B) exp (H') C) 1/q • = Zone I • = Zone II A = Zone III 143 Month F i g u r e IA Species richness and d i v e r s i t y of the i n t e r t i d a l macroalgae at Wizard for each six-week sampling i n t e r v a l . A) Species richness B) exp (H') C) 1/q • = Zone 1 • = Zone II A = Zone III 145 Figure 15 Species richness and d i v e r s i t y of the i n t e r t i d a l macroalgae at Nudibranch for each six-week sampling i n t e r v a l . A) Species richness B) exp (H') C) 1/q • = Zone 1 • = Zone II A = Zone III 147 Month 148 were g r e a t e s t i n Zone I I I of t h e s h e l t e r e d s i t e s , w h i l e a t N u d i b r a n c h d i v e r s i t y was g r e a t e s t i n Zone I I . At N u d i b r a n c h , s p e c i e s r i c h n e s s i n Zone I I I e x c e e d e d t h a t i n Zone I , w h i l e t h e d i v e r s i t y i n d i c e s were g e n e r a l l y l a r g e r f o r Zone I . At t h e s h e l t e r e d s i t e s , d i v e r s i t y v a l u e s i n Zones I and II were v e r y low, r e f l e c t i n g t h e dominance of F u c u s  d i s t i c h u s i n t h e s e a r e a s . N o t e , however, t h a t t h e d i v e r s i t y v a l u e s f o r Zone I I a t W i z a r d were somewhat h i g h e r t h a n t h o s e a t H a i n e s and H e l b y . S p e c i e s r i c h n e s s was a l s o g r e a t e r i n W i z a r d / Z o n e II ( r a n g e of 8-15; F i g u r e 14~a) compared t o Zone II a t H a i n e s and H e l b y (no more t h a n 9; F i g u r e s 12-a and 1 3 - a ) . S p e c i e s r i c h n e s s i n Zone I I I was a l s o g r e a t e r a t W i z a r d compared w i t h H a i n e s and H e l b y , w h i l e exp(H') v a l u e s t e n d e d t o be g r e a t e r a t H a i n e s and H e l b y . V a l u e s of 1/q were g r e a t e s t i n H a i n e s / Z o n e I I I ; v a l u e s d u r i n g t h e summer-f a l l 1982 were l a r g e r a t H e l b y compared w i t h W i z a r d , w h i l e t h o s e f o r spring-summer 1983 were l a r g e r a t W i z a r d . D i v e r s i t y i n Zone I I I o f t h e s h e l t e r e d s i t e s i n c r e a s e d i n t h e f a l l 1982 compared w i t h summer 1982, and d e c r e a s e d from t h e s p r i n g t o summer 1983. S p e c i e s r i c h n e s s showed a s i m i l a r p a t t e r n a t W i z a r d and f o r t h e spring-summer 1983 a t H a i n e s and H e l b y , but S d e c r e a s e d from summer t o f a l l 1982 a t H a i n e s and H e l b y . D i v e r s i t y and s p e c i e s r i c h n e s s were s i m i l a r d u r i n g summer 1982 and 1983 a t H a i n e s ; a t H e l b y , however, S and d i v e r s i t y i n June 1983 e x c e e d e d t h a t i n June 149 1982, a l t h o u g h t h e A u g u s t v a l u e s f o r e a c h y e a r were s i m i l a r . A t W i z a r d , a l l t h r e e v a l u e s were g r e a t e r i n t h e summer 1982 compared t o t h e summer 1983. At N u d i b r a n c h , d i v e r s i t y i n Zones I and I I I showed l i t t l e s e a s o n a l c h a n g e , t h o u g h i n c r e a s e s i n exp(H') and 1/q i n Zone I were o b s e r v e d d u r i n g t h e s p r i n g and summer 1983 ( F i g u r e 1 5 - b c ) ; however, t h e s p e c i e s r i c h n e s s p a t t e r n was n o t a s c l e a r . S p e c i e s r i c h n e s s and t h e d i v e r s i t y v a l u e s f o r Zone I I I d e c l i n e d d u r i n g t h e f a l l 1982, w h i l e t h o s e f o r Zone I i n c r e a s e d s l i g h t l y . In Zone I I , d r a m a t i c d e c l i n e s i n d i v e r s i t y were o b s e r v e d d u r i n g t h e f a l l 1982, w h i l e s p e c i e s r i c h n e s s was r e l a t i v e l y c o n s t a n t . D u r i n g t h e spring-summer 1983, a l l t h r e e p a r a m e t e r s i n Zone I I c l o s e l y p a r a l l e l l e d e a c h o t h e r ; d i v e r s i t y v a l u e s t r i p l e d between A p r i l and May 1983 w h i l e S showed a s i z e a b l e i n c r e a s e as w e l l . D e c r e a s e s i n a l l t h r e e p a r a m e t e r s were o b s e r v e d i n June 1983, w i t h some r e c o v e r y a p p a r e n t i n A u g u s t 1983. V a l u e s o f exp(H') and 1/q i n Zone II d u r i n g summer 1983 were l o w e r t h a n t h o s e f o r summer 1982, w h i l e s p e c i e s r i c h n e s s was s i m i l a r f o r t h e two y e a r s . R e s u l t s of t h e m u l t i p l e r e g r e s s i o n a n a l y s e s of S, exp(H') and 1/q on s e l e c t e d a b i o t i c e n v i r o n m e n t a l f a c t o r s a r e p r e s e n t e d i n T a b l e 24. The MULTIPLE-R and p a r t i a l c o r r e l a t i o n c o e f f i c i e n t s , t h o u g h s i g n i f i c a n t , a r e q u i t e low, i n d i c a t i n g t h a t t h e e n v i r o n m e n t a l f a c t o r s a c c o u n t f o r o n l y a s m a l l amount o f t h e v a r i a b i l i t y i n s p e c i e s r i c h n e s s and 150 d i v e r s i t y . The o n l y f a c t o r p r e s e n t i n a l l t h r e e of t h e e q u a t i o n s i s p e r c e n t t i m e e x p o s e d t o a i r , i n d i c a t i n g t h a t t h e l o n g e r t h e a l g a l a s s e m b l a g e s a r e e x p o s e d , t h e l o w e r t h e s p e c i e s r i c h n e s s and d i v e r s i t y v a l u e s . The r e s u l t s of t h e c l u s t e r a n a l y s i s , i n t h e form of a dendrogram, a r e p r e s e n t e d i n F i g u r e 16. The de n d r o g r a m i s a summary of t h e computer p r i n t - o u t , w i t h t h e s i g n i f i c a n t g r o u p s d i s t i n g u i s h e d . The c h o s e n l e v e l of s i g n i f i c a n c e i s somewhat a r b i t r a r y ( C l i f f o r d and S t e p h e n s o n , 1975), but seemed t o g r o u p t h e 108 s i t e - z o n e - t i m e c o l l e c t i o n s i n t o c o m p r e h e n s i b l e u n i t s . The u n i t s d i s t i n g u i s h e d i n F i g u r e 16 a r e c o m p r i s e d o f g e n e r a l s i t e - z o n e - s e a s o n g r o u p s , a l t h o u g h c e r t a i n p a r t i c u l a r s i t e - z o n e - m o n t h c o l l e c t i o n s a r e a l s o i d e n t i f i e d . The c o l l e c t i o n s f o r e a c h of t h e f o l l o w i n g s i t e -z o n e - t i m e s a r e c l a s s i f i e d i n t o s e p a r a t e g r o u p s : 1) H a i n e s / Z o n e I - s p r i n g & summer 1983 (Group B) 2) H a i n e s , H e l b y and W i z a r d / Z o n e II - s p r i n g & summer 1983 (Group F) 3) N u d i b r a n c h / Z o n e I I (Group H) 4) N u d i b r a n c h / Z o n e I I I (Group K) The r e m a i n i n g G r o u p s (A,C,D,E,G,I,J) were composed of v a r i o u s c o m b i n a t i o n s of t h e s i t e - z o n e - t i m e c o l l e c t i o n s . T a b l e 24. M u l t i p l e r e g r e s s i o n a n a l y s e s of s p e c i e s r i c h n e s s and d i v e r s i t y on s e l e c t e d a b i o t i c e n v i r o n m e n t a l f a c t o r s . 5 = 88.3 - 1 . 0 (H20-T) - 2.7(PFD) - 3.0(RAIN) - 0 .5 (VAR-H20-T) + 1.O(SAL) - O.1(AIREXP) MULTIPLE-R = 0.69228 SE = 7.7 P a r t i a l c o r r e l a t i o n c o e f f i c i e n t s : H20-T r = = -o. . 26791 P = = 0 .0062 PFD r = = -0 . .43704 P = = 0 .0000 RAIN r = = - 0 . 30602 P = = 0 .0017 VAR-H20-T r = •  -o. 63596 P = = 0. .0000 SALINITY r = = 0. 27710 . P = = 0. .0045 AIREXP r = •  -o. 381 10 P = = 0. .0001 exp(H) = -0 .04 + 0 .08 (A IR -T ) + 0 .04(SAL) -0 .02(A IR EXP) MULTIPLE-R = 0.48074 SE = 1.9 P a r t i a l c o r r e l a t i o n c o e f f i c i e n t s : AIR-T r = 0.32541 P = 0.0007 SALINITY r = 0.37824 P = 0.0001 AIREXP r = -0.27488 P = 0.0043 1/q = 2.0 + 0 .2 (SAL) - 0.09(N03) - O.OI(AIREXP) MULTIPLE-R = 0.39355 SE = 1.4 P a r t i a l c o r r e l a t i o n c o e f f i c i e n t s : SALINITY r = 0.26929 P = 0.0052 N03 r = -0.24061 P = 0 .0130 AIREXP r = -0 .27538 P = 0.0043 152 Figure 16 Summary of the cl u s t e r analysis of the reduced site-zone-time biomass matrix. A - Haines/Zone 1, F a l l and Winter Wizard/Zone I, June 1982 K B -Helby/Zone I, Summer 1982 Haines/Zone I, Spring and Summer 1983 Haines/Zone I I I , Summer C - Haines/Zone I, Spring and Summer 1983 Helby & Wizard/Zone I I , August 1983 D - Helby/Zone I, Spring 1983 Haines & Wizard/Zone I I , Winter Wizard/Zone I I I , Summer Helby/Zone I I I , Summer 1982 E - Wizard/Zone I, Spring 1983 Helby/Zone I I , Winter and Spring 1983 Helby & Wizard/Zone I, September 1982 F - Haines & Wizard/Zone I I , Spring and Summer 1983 Helby/Zone I I I , Summer 1983 G - Nudibranch/Zone I, Summer 1982 Helby/Zone I, Winter Wizard/Zone I I I , Spring 1983 Helby/Zone I I I , Summer 1982 Haines, Helby & Wizard/Zone I I , March 1983 H - Nudibranch/Zone II I - Haines/Zone I I I , Summer Wizard/Zone 111, F a l l 1982 J - Nudibranch/Zone I, Winter and Summer 1983 Helby/Zone I I I , November 1982 and A p r i l 1983 Haines/Zone I I I , May 1983 K - Nudibranch/Zone III 154 D i s c u s s i o n The r e s u l t s of t h e c l u s t e r a n a l y s i s ( F i g u r e 16) v a l i d a t e t h e o r i g i n a l d i v i s i o n of t h e i n t e r t i d a l a t e a c h s t u d y s i t e i n t o t h e i r r e s p e c t i v e z o n e s . T h i s i s p a r t i c u l a r l y e v i d e n t f o r N u d i b r a n c h , where Zones I I and I I I a r e c l e a r l y d i s t i n g u i s h e d . The a n a l y s i s a l s o shows, t o some e x t e n t , t h e e f f e c t s o f s e a s o n , t i d a l h e i g h t , and wave e x p o s u r e on t h e s t a n d i n g c r o p s o f t h e m a c r o a l g a e . In g e n e r a l , t h e s p r i n g and summer p e r i o d s f o r Zones I and I I a t H a i n e s , H e l b y and W i z a r d were d i s t i n g u i s h e d f r o m t h e o t h e r s i t e - z o n e - t i m e c o l l e c t i o n s . The spring-summer 1983 p e r i o d c o l l e c t i o n s were a l s o s e p a r a t e d (Groups C and F, F i g u r e 1 6 ) . The a l g a l a s s e m b l a g e s i n Zone I I I of t h e s h e l t e r e d s i t e s and N u d i b r a n c h / Z o n e I were c l a s s i f i e d t o g e t h e r i n v a r i o u s g r o u p s , r e f l e c t i n g t h e i m p o r t a n c e of F u c u s d i s t i c h u s i n t h e c l u s t e r a n a l y s i s . However, s e c o n d a r y s p e c i e s ( e . g. C l a d o p h o r a spp.) were f a i r l y a b undant a t b o t h N u d i b r a n c h / Z o n e I and Zone I I I of H a i n e s , H e l b y , and W i z a r d , so t h a t t h e c l a s s i f i c a t i o n i s not s o l e l y due t o s i m i l a r i t i e s i n F\_ d i s t i c h u s s t a n d i n g c r o p i n t h e s e a s s e m b l a g e s . N e i l l (1977) has r e p o r t e d v a l u e s and p a t t e r n s o f H' ( b a s e d on b i o m a s s ) f o r n o r t h w e s t S p a i n w h i c h were s i m i l a r t o t h o s e o b s e r v e d i n t h i s s t u d y . A t p r o t e c t e d s i t e s , a r e a s h i g h on t h e s h o r e were d o m i n a t e d by f u c o i d s ( P e l v e t i a 155 c a n a l i c u l a t a and F u c u s s p i r a l i s ) and H' was n e a r z e r o [ e x p ( H * ) = 1.0]. T h e s e a s s e m b l a g e s were s i m i l a r t o Zones I and II a t H a i n e s , H e l b y , and W i z a r d . In S p a i n , l o w e r l e v e l s on t h e s h o r e (+0.3-0.6 m above l o w e r s p r i n g t i d a l l e v e l ) a t more e x p o s e d s i t e s were d o m i n a t e d by H i m a n t h a l i a e l o n g a t a (L . ) S.F. G r a y . D i v e r s i t y i n t h i s zone r a n g e d between exp(H') = 2.7-20.0, w i t h numerous c h a n g e s t h r o u g h o u t t h e y e a r d e p e n d e n t on t h e d ominance o f H_;_ e l o n g a t a . The Zone I I I a s s e m b l a g e s a t t h e s h e l t e r e d s i t e s a p p e a r t o be s i m i l a r t o t h e H^ e l o n g a t a c o m m u n i t i e s i n S p a i n , a l t h o u g h t h e d i v e r s i t y v a l u e s were h i g h e r i n S p a i n . L u b c h e n c o (1978) s t u d i e d t h e impact o f h e r b i v o r y on t h e s p e c i e s r i c h n e s s and d i v e r s i t y (H', b a s e d on p e r c e n t c o v e r ) of i n t e r t i d a l a l g a e i n New E n g l a n d . The v a l u e s o f H', t h o u g h b a s e d on per c e n t c o v e r d a t a , were s i m i l a r t o t h o s e n e a r B a m f i e l d [exp(H') . = 1.0 - 4 . 1 ] . On emergent s u b s t r a t u m , a l g a l d i v e r s i t y d e c r e a s e d i n a l i n e a r f a s h i o n w i t h i n c r e a s i n g d e n s i t y of L i t t o r i n a l i t t o r e a . The h e r b i v o r e s p r e f e r e n t i a l l y g r a z e d e p h e m e r a l a l g a e , s u c h as U l v a , E n t e r o m o r p h a , and P o l y s i p h o n i a , but d i d not g r a z e f u c o i d s . Thus, f u c o i d s e v e n t u a l l y d o m i n a t e d t h e a r e a , and d i v e r s i t y was low [exp(H') = 1.01-1.20]. B o t h exp(H') and 1/q were low t h r o u g h o u t t h e s t u d y p e r i o d i n Zones I and I I a t H a i n e s , H e l b y , and W i z a r d , r e f l e c t i n g t h e dominance o f F\_ d i s t i c h u s i n t h e s e a l g a l a s s e m b l a g e s . D i v e r s i t y and s p e c i e s r i c h n e s s were a l s o 156 g r e a t e r i n W i z a r d / Z o n e II as compared w i t h t h e o t h e r upper i n t e r t i d a l a r e a s ( F i g u r e s 12-14). The l a r g e and v a r i a b l e f l u c t u a t i o n s i n s p e c i e s r i c h n e s s i n t h e s e z o n e s , i n c o n t r a s t t o t h e s t a b l e d i v e r s i t y v a l u e s ( F i g u r e 12-14), s u g g e s t t h a t t h e p r e s e n c e of s e c o n d a r y s p e c i e s was due t o c h a n c e e n v i r o n m e n t a l f l u c t u a t i o n s a f f e c t i n g r e p r o d u c t i o n , r e c r u i t m e n t , a n d / o r h a b i t a t a v a i l a b i l i t y , t h e F\_ d i s t i c h u s c a n o p y , and s u b s t r a t u m h e t e r o g e n e i t y ( s h a l l o w d e p r e s s i o n s , e t c . w h i c h r e t a i n water when t h e t i d e goes o u t ) . L a t e s u m m e r - f a l l , i n c r e a s e s i n d i v e r s i t y were o b s e r v e d f o r W i z a r d / Z o n e II and N u d i b r a n c h / Z o n e I ( F i g u r e s 14-15). The s e a s o n a l c h a n g e s i n d i c a t e t h a t c o n d i t i o n s were more s t r e s s f u l d u r i n g t h e summer, when wave a c t i o n i s m i n i m a l and d e s i c c a t i o n s t r e s s g r e a t e r due t o t h e l o w e r d a y t i m e t i d a l h e i g h t s . L e s s r i g o r o u s c o n d i t i o n s d u r i n g t h e f a l l p e r m i t t e d t h e g r o w t h o f s e c o n d a r y s p e c i e s , and d i v e r s i t y was t h e r e f o r e s l i g h t l y g r e a t e r d u r i n g t h i s t i m e o f t h e y e a r . At t h e s h e l t e r e d s i t e s , d i v e r s i t y and s p e c i e s r i c h n e s s were g r e a t e s t i n Zone I I I ( F i g u r e s 12-14). At a l l t h r e e s i t e s , s p e c i e s r i c h n e s s and d i v e r s i t y i n Zone I I I i n c r e a s e d d u r i n g t h e f a l l 1982 and d e c r e a s e d d u r i n g t h e spring-summer 1983, s u g g e s t i n g t h a t p h y s i o l o g i c a l s t r e s s e s were i m p o r t a n t i n g o v e r n i n g t h e o c c u r r e n c e of m a c r o a l g a e i n t h i s a s s e m b l a g e . P l a n t s l i v i n g i n t h i s zone were e x p o s e d t o t h e a i r l e s s t h a n 10% of t h e t i m e ( T a b l e 3 ) ; t h u s p e r i o d s o f p h y s i o l o g i c a l s t r e s s were i n f r e q u e n t . However, t h e a l g a e 157 t h a t l i v e i n t h i s zone c o u l d o n l y t o l e r a t e h i g h s t r e s s f o r s h o r t amounts of t i m e ; p e r i o d s of h i g h s u n l i g h t and a i r t e m p e r a t u r e , c o n c u r r e n t w i t h low t i d e s ( s u c h as o c c u r r e d d u r i n g t h e e a r l y summer), may have been v e r y h a r m f u l t o t h e s e p l a n t s ( e . g. t h e d e c l i n e i n C o r a l l i n a V a n c o u v e r i e n s i s i n Zone I I I a t H a i n e s ; C h a p t e r 3 ) . The h i g h e s t d i v e r s i t y and s p e c i e s r i c h n e s s were o b s e r v e d i n Zone II a t N u d i b r a n c h ( F i g u r e 15). D i v e r s i t y was l o w e s t d u r i n g t h e f a l l 1982 and e a r l y s p r i n g 1983, when wave a c t i o n was g r e a t e s t ( T a b l e 1 ) . The r e c o r d e d s e a s o n a l p a t t e r n s u g g e s t s t h a t wave a c t i o n was i m p o r t a n t i n l i m i t i n g t h e d e v e l o p m e n t o f t h e N u d i b r a n c h / Z o n e II a l g a l a s s e m b l a g e . By p r e v e n t i n g t h e d e v e l o p m e n t o f a F ^ d i s t i c h u s canopy and r e d u c i n g p h y s i o l o g i c a l s t r e s s , wave a c t i o n - e n a b l e d t h e d e v e l o p m e n t of t h e " a l g a l t u r f " community; however, h i g h wave e x p o s u r e was a l s o a p p a r e n t l y d e s t r u c t i v e t o t h e f i l a m e n t o u s and s t r u c t u r a l l y s i m p l e a l g a e p r e s e n t i n t h e zo n e . Exp(H*) i s p l o t t e d a g a i n s t d i s t u r b a n c e (wave e x p o s u r e ) and p h y s i o l o g i c a l s t r e s s ( d e s i c c a t i o n b e i n g t h e major c o n s i d e r a t i o n ) i n F i g u r e 17. Wave e x p o s u r e i s b a s e d on t h e s u b j e c t i v e r a t i n g s made a t e a c h s t u d y s i t e ( s e e T a b l e 1, C h a p t e r 2 ) . P h y s i o l o g i c a l s t r e s s i s s u b j e c t i v e l y r a n k e d from 1 t o 4, and i n c r e a s e s w i t h i n c r e a s i n g t i d a l h e i g h t . I t i s a l s o assumed t h a t a s wave e x p o s u r e i n c r e a s e s , p h y s i o l o g i c a l s t r e s s a t c o m p a r a b l e t i d a l h e i g h t s i s r e d u c e d Figure 17 P l o t o f exp (H') against wave exposure and d e s i c c a t i o n s t r e s s . A - Haines, Helby & Wizard/Zone I Haines & Helby/Zone II B - Wizard/Zone II C - Nudibranch/Zone I D - Haines, Helby and Wizard/Zone I I I E - Nudibranch/Zone III F - Nudibranch/Zone I I , Summer G - Nudibranch, Zone I I , F a l l and Spring H - Beale 160 ( S t e p h e n s o n and S t e p h e n s o n , 1949; L e w i s , 1964, 1968; J o n e s and D e m e t r o p o u l o u s , 1968). W i t h th e l i m i t e d d a t a a v a i l a b l e , i t i s h y p o t h e s i z e d t h a t t h e o b s e r v e d p a t t e r n of s p e c i e s d i v e r s i t y ( F i g u r e 17) i s b e s t e x p l a i n e d i n l i g h t of H u s t o n ' s (1979) " g e n e r a l h y p o t h e s i s o f s p e c i e s d i v e r s i t y " , as c a u s e d by t h e i n t e r a c t i v e e f f e c t s of wave a c t i o n and d e s i c c a t i o n s t r e s s . Waves a c t as a d i s t u r b a n c e , l i m i t i n g p l a n t b i o m a s s and s p e c i e s d i s t r i b u t i o n s , b ut a l s o a l l e v i a t e p h y s i o l o g i c a l s t r e s s e s f a c e d by i n t e r t i d a l m a c r o a l g a e . The p r e s e n c e o f a F. d i s t i c h u s c a n o p y , s u b s t r a t u m h e t e r o g e n e i t y ( c r e v i c e s , b a r n a c l e s , e t c . ) , and h e r b i v o r y a r e of s e c o n d a r y i m p o r t a n c e . F u r t h e r e x p e r i m e n t a t i o n , i n c l u d i n g m a n i p u l a t i o n s a s s e s s i n g t h e r o l e s o f c o m p e t i t i o n and h e r b i v o r y , a r e needed t o c o n f i r m t h i s h y p o t h e s i s . However, t h e r e s u l t s o f t h e a l g a l and i n v e r t e b r a t e s a m p l i n g p r o g r a m s and t h e E\ d i s t i c h u s c l e a r i n g e x p e r i m e n t a r e s u p p o r t i v e e v i d e n c e . H u s t o n (1979) assumes t h a t most c o m m u n i t i e s a r e i n a n o n - e q u i l i b r i u m c o n d i t i o n , where c o m p e t i t i v e e x c l u s i o n i s p r e v e n t e d by p e r i o d i c p o p u l a t i o n r e d u c t i o n s and e n v i r o n m e n t a l f l u c t u a t i o n s . D i v e r s i t y i s d e p e n d e n t on t h e r a t e s a t w h i c h c o m p e t i t i v e d i s p l a c e m e n t o c c u r . Where c o m p e t i t i v e d i s p l a c e m e n t o c c u r s a t a h i g h r a t e , e q u i l i b r i u m i s a p p r o a c h e d and community d i v e r s i t y i s low. D i v e r s i t y i s h i g h e r i n c o m m u n i t i e s where t h e r a t e of c o m p e t i t i v e d i s p l a c e m e n t i s low. C o n d i t i o n s w h i c h enhance t h e g r o w t h 161 r a t e o f a few s p e c i e s ( t h u s i n c r e a s i n g c o m p e t i t i v e a b i l i t y ) s h o u l d r e d u c e d i v e r s i t y , w h i l e d i v e r s i t y w i l l be m a i n t a i n e d or i n c r e a s e d where growth r a t e s a r e l o w e r . F u c u s d i s t i c h u s d o m i n a t e d t h e a l g a l a s s e m b l a g e s i n Zones I and II a t H a i n e s , H e l b y , and W i z a r d and d i v e r s i t y was v e r y low. The abundance of s e c o n d a r y s p e c i e s , as seen i n t h e r e s u l t s o f t h e F\_ d i s t i c h u s c l e a r i n g e x p e r i m e n t ( T a b l e 20), a p p e a r l i m i t e d more by p h y s i o l o g i c a l s t r e s s t h a n by c o m p e t i t i o n w i t h F ^ d i s t i c h u s . E n v i r o n m e n t a l c o n d i t i o n s were g e n e r a l l y s t a b l e , but r i g o r o u s , t h r o u g h o u t t h e y e a r i n t h e s e z o n e s . C o m p e t i t i o n t h u s d i d n o t seem t o be i m p o r t a n t i n t h e s e a s s e m b l a g e s ( u n l e s s i t was o c c u r r i n g between t h e s e c o n d a r y s p e c i e s t h e m s e l v e s ) . The s t a b l e and r e l a t i v e l y h a r s h p h y s i c a l c o n d i t i o n s a p p a r e n t l y l i m i t e d t h e g r o w t h of a l l b u t F_j_ d i s t i c h u s , so a l g a l d i v e r s i t y was low. P h y s i c a l c o n d i t i o n s were more b e n i g n i n Zone I I I o f t h e s t u d y s i t e s ; t h u s t h o s e s p e c i e s f o u n d o n l y s p o r a d i c a l l y i n Zones I and I I grew t o some abundance h e r e . The a l g a e p r e s e n t i n t h i s zone were g e n e r a l l y f a s t e r g r o w i n g a n n u a l , e p h e m e r a l and e p i p h y t i c s p e c i e s ( e . g. U l v a f e n e s t r a t a , L e a t h e s i a d i f f o r m i s , C r y p t o s i p h o n i a woodi i , H a l o s a c c i o n  americanum , C l a d o p h o r a s p p . ) , none o f w h i c h were a b l e t o d o m i n a t e t h e a s s e m b l a g e . C o m p e t i t i v e d i s p l a c e m e n t s a p p e a r e d t o have been m i n i m a l , so d i v e r s i t y was h i g h . A l t h o u g h H. s e s s i l e was a l a r g e p e r c e n t a g e o f t h e t o t a l a l g a l b i o m a s s i n N u d i b r a n c h / Z o n e I I I , many o t h e r s p e c i e s were a l s o a b l e t o 162 grow t h e r e . D i v e r s i t y was t h u s c o m p a r a t i v e l y h i g h i n t h i s a s s e m b l a g e a l s o . I n c r e a s e d wave a c t i o n a t N u d i b r a n c h r e d u c e s p h y s i o l o g i c a l s t r e s s but a l s o l i m i t s t h e s t a t u r e and biomass of t h e a l g a e ( n o t e t h i s i n t h e c a s e s o f F_;_ d i s t i c h u s and N. l a r i x ). The p l a n t s a r e d i s t r i b u t e d i n a m o s a i c of s m a l l p a t c h e s and a t u r f o f i n t e r m i n g l e d f i l a m e n t s . The p a t c h y d i s t r i b u t i o n i s p r o b a b l y t h e r e s u l t o f wave shock p r e v e n t i n g t h e d e v e l o p m e n t of more e x t e n s i v e g r o w t h and l i m i t i n g r a t e s o f c o m p e t i t i v e d i s p l a c e m e n t ; d i v e r s i t y i s t h u s v e r y h i g h i n t h i s z o ne. At B e a l e , a l t h o u g h p h y s i o l o g i c a l s t r e s s i s p r o b a b l y low, t h e h i g h d e g r e e o f wave e x p o s u r e i s l i m i t i n g t o many s p e c i e s . C o m p e t i t i o n , p a r t i c u l a r l y w i t h M y t i l u s c a l i f o r n i a n u s , i s a l s o i m p o r t a n t a t t h i s s i t e ( D a y t o n , 1971; P a i n e , 1979). R a t e s o f c o m p e t i t i v e d i s p l a c e m e n t and d i s t u r b a n c e a r e h i g h , so t h a t d i v e r s i t y i s r e l a t i v e l y low . The e f f e c t s o f water m o t i o n have o f t e n been c i t e d a s major i n f l u e n c e s on t h e s t r u c t u r e of i n t e r t i d a l c o m m u n i t i e s ( S t e p h e n s o n and S t e p h e n s o n , 1949; Southward and O r t o n , 1954; L e w i s , 1968, 1977; R i c k e t t s e t a l . , 1968; D a y t o n , 1971; L u b c h e n c o and Menge, 1978). C o n n e l l (1975) s t a t e d t h a t " t h e d i s t r i b u t i o n and abundance of a s p e c i e s a r e u l t i m a t e l y d e t e r m i n e d by t o l e r a n c e s t o e x t r e m e s of p h y s i c a l c o n d i t i o n s , but a s p e c i e s i s u s u a l l y l i m i t e d t o a s m a l l e r range of h a b i t a t s and p o p u l a t i o n s i z e by i n t e r a c t i o n s w i t h o t h e r 163 o r g a n i s m s . " In t h e B a m f i e l d a r e a h e r b i v o r y seems t o be o f l i m i t e d i m p o r t a n c e , and c o m p e t i t i o n r e s t r i c t e d t o s e c o n d a r y and a n n u a l s p e c i e s . A l g a l d i s t r i b u t i o n s and a b u n d a n c e s a p p e a r t o be c o n t r o l l e d l a r g e l y by t h e p h y s i c a l e n v i r o n m e n t . However, as a l s o n o t e d by C o n n e l l ( 1 9 7 5 ) , t h e a l g a e t h e m s e l v e s a l t e r t h e p h y s i c a l e n v i r o n m e n t . Thus t h e F. d i s t i c h u s c a n o p y r e d u c e s d e s i c c a t i o n s t r e s s and P. p a l m a e f o r m i s and H^ s e s s i l e r e d u c e wave s h o c k , so a d d i t i o n a l s p e c i e s c an s u r v i v e i n t h e i r p r e s e n c e ; t h e " a l g a l t u r f " i s a s e l f - r e i n f o r e i n g g r o w t h form w h i c h r e d u c e s d e s i c c a t i o n s t r e s s . T h i s may, i n p a r t , a l s o e x p l a i n t h e low c o r r e l a t i o n between t h e s e l e c t e d a b i o t i c e n v i r o n m e n t a l f a c t o r s and d i v e r s i t y i n t h e m u l t i p l e r e g r e s s i o n a n a l y s i s ( T a b l e 24; see a l s o t h e r e g r e s s i o n s f o r a l g a l s t a n d i n g c r o p p r e s e n t e d i n C h a p t e r 3 ) . The p r e s e n c e of o t h e r a l g a l s p e c i e s ( t h e F ^ d i s t i c h u s c a n o p y , t h e " a l g a l t u r f " ) , c o mbined w i t h t h e e f f e c t s of wave a c t i o n , may have p r o d u c e d an e n v i r o n m e n t t o w h i c h t h e a l g a e a r e e x p o s e d w h i c h has l i t t l e r e s e m b l a n c e t o t h e measured p h y s i c a l e n v i r o n m e n t . The r e s u l t s o f t h i s s t u d y s u g g e s t t h a t t h e B a m f i e l d a r e a d i f f e r s i n many ways from t h o s e i n t e r t i d a l s h o r e s u s u a l l y a s s o c i a t e d w i t h t h e P a c i f i c N o r t h w e s t . P r e d a t i o n has been s t r e s s e d a s h a v i n g a v e r y i m p o r t a n t r o l e i n i n t e r t i d a l community s t r u c t u r e on W a s h i n g t o n s h o r e s ( P a i n e , 1966; D a y t o n , 1971; Menge and S u t h e r l a n d , 1976; Menge and L u b c h e n c o , 1981). C o m p e t i t i o n has been f o u n d t o o c c u r o n l y 164 s p o r a d i c a l l y due t o t h e h i g h p r e d a t i o n p r e s s u r e . The d i f f e r e n c e s o b s e r v e d h e r e a r e p r o b a b l y i n l a r g e p a r t due t o d i f f e r e n c e s i n t h e d e g r e e o f wave e x p o s u r e a t t h e s i t e s s t u d i e d . The H a i n e s , H e l b y and W i z a r d s t u d y s i t e s a r e a l m o s t c e r t a i n l y more p r o t e c t e d t h a n t h e W a s h i n g t o n c o a s t , and t h u s F_j_ d i s t i c h u s i s t h e dom i n a n t i n t e r t i d a l o r g a n i s m . P a s t s t u d i e s of P a c i f i c N o r t h w e s t i n t e r t i d a l c o m m u n i t i e s ( e x c e p t N a s s i c h u k , 1975) have a l l b u t i g n o r e d t h e r o l e of F. d i s t i c h u s and i n t e r a c t i o n s w i t h s e c o n d a r y s p e c i e s ( e . g. D a y t o n , 1971). The B a m f i e l d a r e a , t h o u g h p r o b a b l y n o t u n i q u e , r e p r e s e n t s a s e r i e s of i n t e r t i d a l h a b i t a t s which have been l i t t l e s t u d i e d by m a r i n e e c o l o g i s t s . F u r t h e r d e s c r i p t i v e and e x p e r i m e n t a l s t u d i e s a r e needed t o p r o p e r l y p l a c e t h i s a r e a i n r e l a t i o n t o o t h e r i n t e r t i d a l a r e a s and t o examine t h e h y p o t h e s e s p r e s e n t e d i n t h i s c h a p t e r r e g a r d i n g t h e o r g a n i s a t i o n of t h e i n t e r t i d a l a l g a l community. 165 CHAPTER 6 - PRODUCTIVITY OF THE MACROALGAE I t i s g e n e r a l l y a c k n o w l e d g e d t h a t m a r i n e m a c r o a l g a e a r e v e r y p r o d u c t i v e p l a n t s . R y t h e r (1963) p r o p o s e d t h a t m a c r o a l g a e may a c c o u n t f o r 10% o f t h e p r o d u c t i v i t y of t h e o c e a n s ' s p h y t o p l a n k t o n , even t h o u g h t h e y o c c u p y o n l y 0.1% of t h e a r e a a v a i l a b l e t o p h y t o p l a n k t o n . Mann (1973) s t a t e d t h a t t h e p r o d u c t i v i t y o f m a c r o a l g a l c o m m u n i t i e s i s c o m p a r a b l e t o t h a t of t h e most p r o d u c t i v e t e r r e s t r i a l s y s t e m s ( s u c h as t r o p i c a l r a i n f o r e s t s and managed a g r i c u l t u r a l c r o p s ) . A n n u a l c a r b o n b u d g e t s have been d e t e r m i n e d f o r L a m i n a r i a s a c c h a r i n a ( J o h n s t o n e t a l . , 1977) and L. l o n q i c r u r i s ( H a t c h e r e t a l . , 1977). T h i s i n f o r m a t i o n , combined w i t h t h e s t u d i e s o f Mann ( I 9 7 2 a , b ) , G e r a r d and Mann (1 9 7 9 ) , and Chapman and L i n d l e y ( 1 9 8 1 ) , p r o v i d e i n f o r m a t i o n on t h e p r o d u c t i v i t y o f v a r i o u s s p e c i e s o f L a m i n a r i a . Chapman and C r a i g i e (1977, 1978), A n d e r s o n e t a l . ( 1 9 8 1 ) , and Gagne e t a l . (1982) examined t h e r e l a t i o n s h i p s between g r o w t h , s t o r a g e o f c a r b o n and n i t r o g e n , and ambient e n v i r o n m e n t a l c o n d i t i o n s , and p r o v i d e d e x p l a n a t i o n s f o r t h e o b s e r v e d p a t t e r n s and m a g n i t u d e s o f L a m i n a r i a p r o d u c t i v i t y . 166 S i m i l a r c o m p r e h e n s i v e knowledge o f i n t e r t i d a l m a c r o a l g a e i s l a c k i n g . T h e r e have been v e r y few s t u d i e s w h i c h have combined e s t i m a t e s of a l g a l s t a n d i n g c r o p s w i t h c o n c u r r e n t measurements of p h o t o s y n t h e s i s t o c a l c u l a t e p r o d u c t i v i t y . B r i n k h u i s (1977a,b,c) s t u d i e d t h e p r o d u c t i v i t y of s a l t - m a r s h p o p u l a t i o n s of A s c o p h y l l u m  nodosum , F u c u s v e s i c u l o s u s , and U l v a l a c t u c a . L i t t l e r e t a l . (1979) r e p o r t e d on t h e p r o d u c t i v i t y of a r o c k y i n t e r t i d a l a l g a l community i n s o u t h e r n C a l i f o r n i a , but t h e y sampled o n l y f o u r t i m e s d u r i n g t h e y e a r and assumed s t a n d i n g c r o p was e q u i v a l e n t t o p e r c e n t c o v e r . In a d d i t i o n , t h e y c a l c u l a t e d p r o d u c t i v i t y a s s u m i n g t h a t p h o t o s y n t h e s i s r a t e s f o r e a c h s p e c i e s on an a r e a b a s i s ( i . e . mg C f i x e d r r r 2 t h a l l u s ) were d i r e c t l y a p p l i c a b l e t o t h e p e r c e n t o f i n t e r t i d a l s u b s t r a t e o c c u p i e d by t h e s p e c i e s . In t h i s s t u d y , d a t a from t h e s t a n d i n g c r o p s a m p l i n g p r o g r am ( C h a p t e r 3) was c o m b i n e d w i t h measurements of d i u r n a l p h o t o s y n t h e s i s t o o b t a i n e s t i m a t e s o f d a i l y , m o n t h l y , and a n n u a l p r o d u c t i v i t y . M u l t i p l e r e g r e s s i o n a n a l y s e s were a l s o p e r f o r m e d i n an a t t e m p t t o r e l a t e d a i l y p h o t o s y n t h e s i s (mg C g d r y wt" 1 d " 1 ) and p o p u l a t i o n / c o m m u n i t y p r o d u c t i v i t y ( p e r m2 of i n t e r t i d a l s u b s t r a t e ) w i t h s e l e c t e d a b i o t i c e n v i r o n m e n t a l f a c t o r s . 167 D e f i n i t i o n of Terms A major p r o b l e m i n p r e v i o u s p r i m a r y p r o d u c t i v i t y s t u d i e s has been t h e v a r i o u s meanings g i v e n t o t h e words " p r o d u c t i v i t y " and " p r o d u c t i o n " . C o n s e q u e n t l y , i t i s sometimes d i f f i c u l t t o u n d e r s t a n d what was m e a s u r e d and t o i n t e r p r e t t h e r e s u l t s . In o r d e r t o m i n i m i z e any s u c h c o n f u s i o n r e g a r d i n g t h e p r e s e n t a t i o n and i n t e r p r e t a t i o n o f my d a t a , t h e f o l l o w i n g t e r m s , d e f i n e d as p e r W e s t l a k e ( 1 9 6 5 ) , w i l l be u s e d : s t a n d i n g c r o p — t h e mass of o r g a n i c m a t e r i a l t h a t can be s ampled or h a r v e s t e d by n ormal methods a t any one t i m e from a g i v e n a r e a ( u n i t s : g d r y wt r r r 2 ) ; p r i m a r y p r o d u c t i o n — t h e mass of new o r g a n i c m a t e r i a l c r e a t e d by p h o t o s y n t h e s i s , o r t h e e n e r g y t h i s r e p r e s e n t s , i n a g i v e n u n i t a r e a a t any one t i m e . P r i m a r y p r o d u c t i o n must be v i e w e d i n t e r m s o f n e t and g r o s s p r o d u c t i o n , as d e f i n e d below f o r n e t and g r o s s p r o d u c t i v i t y ( u n i t s : g C n r 2 ) ; p r i m a r y p r o d u c t i v i t y — t h e r a t e of p r i m a r y p r o d u c t i o n . The r a t e of f l o w o f e n e r g y i n t o t h e f i r s t ( p r o d u c e r , p l a n t ) t r o p h i c l e v e l ( u n i t s : g C n r 2 d a y " 1 ) ; 168 g r o s s p r o d u c t i v i t y — t h e r a t e of p r o d u c t i o n of new o r g a n i c m a t e r i a l or f i x a t i o n o f e n e r g y , i n c l u d i n g t h a t s u b s e q u e n t l y l o s t a s t h e r e s u l t o f r e s p i r a t i o n ; n e t p r o d u c t i v i t y — t h e r a t e o f a c c u m u l a t i o n of new o r g a n i c m a t e r i a l or s t o r e d e n e r g y . In terms of p r o d u c t i o n , t h e o r g a n i c m a t e r i a l o r e n e r g y a v a i l a b l e f o r use by t h e nex t t r o p h i c l e v e l . C l a r k e (1946) p r e s e n t s a s e r i e s of e q u a t i o n s m o d e l l i n g p r o d u c t i v i t y b a s e d on i n s t a n t a n e o u s and mean r a t e s and d i s c u s s e s t h e i r a p p l i c a t i o n s . The f o l l o w i n g e q u a t i o n s a r e an e x t e n s i o n of C l a r k e ' s (1946) e q u a t i o n s w i t h some c h a n g e s i n s y m b o l i s m and w i t h p a r t i c u l a r r e f e r e n c e t o t h e p r i m a r y p r o d u c t i v i t y of m a r i n e m a c r o a l g a e . . The g r o s s and n e t p r i m a r y p r o d u c t i v i t y c a n be e s t i m a t e d u s i n g t h e f o l l o w i n g two e q u a t i o n s : 1) G r o s s p r i m a r y p r o d u c t i v i t y = GPP = SC (GPS) 2) Net p r i m a r y p r o d u c t i v i t y = NPP = SC (NPS) = SC (GPS - R) 169 where: SC = s t a n d i n g c r o p o f m a c r o a l g a e (g d r y wt irr 2) GPS = r a t e o f g r o s s p h o t o s y n t h e s i s ( m g C g d r y wt" 1 h " 1 ) NPS = r a t e o f net p h o t o s y n t h e s i s (mg C g d r y wt" 1 h " 1 ) R = r a t e o f r e s p i r a t i o n (mg C g d r y wt" 1 h " 1 ) The p o t e n t i a l s t a n d i n g c r o p (PSC) a t t h e end of some t i m e i n t e r v a l (t=0) t o ( t = i ) , a s s u m i n g no l o s s e s t o h e r b i v o r y , wave e r o s i o n of t i s s u e s , e t c . , can be c a l c u l a t e d u s i n g e q u a t i o n ( 3 ) : 3) P S C ( t = i ) = S C ( t = 0 ) { e [ e x p ( G P S - R ) t ] } Net p r o d u c t i v i t y o v e r t h e t i m e i n t e r v a l ( t = i ) t o (t=0) i s 4) NPP = [ P S C ( t = i ) - S C ( t = 0 ) ] / t T h i s i s e s s e n t i a l l y t h e " p r o d u c t i o n " o f R i c k e r ( 1 9 5 8 ) : " t h e t o t a l e l a b o r a t i o n of new body s u b s t a n c e i n a s t o c k d u r i n g u n i t t i m e , i r r e s p e c t i v e of whether or not i t s u r v i v e s t o t h e end of t h a t t i m e . " 170 The losses of plant biomass (LOS) due to herbivory, etc. , can then be estimated using equation (5): 5) LOS = (DOM + HER + OTH) = PSC(t=i) - SC(t=i) where: DOM = loss/excretion of dissolved organic matter HER = loss of plant production to herbivores OTH = loss of plant material due to other causes (e. g. wave erosion of tissues) LOS = t o t a l loss of fixed carbon/energy excluding that due to respiratory metabolism The procedures used in t h i s study can provide an estimate of the LOS term, but not for the individual terms (DOM, HER, OTH) which contribute to the LOS term. The terms in equations (3), (4) and (5) should be in units of carbon or energy. Equation (5) w i l l give a rough estimate of the LOS term. Considering the large v a r i a b i l i t y in the measurement of standing crop, photosynthetic rates, and the rather imprecise method of c a l c u l a t i n g the LOS term, i t s accuracy is somewhat limited. However, i t should be possible to make an estimate of the magnitude of t h i s term and compare i t with other properties of the system. 171 Methods and M a t e r i a l s P r o d u c t i v i t y of i n t e r t i d a l m a c r o a l g a e was c a l c u l a t e d u s i n g t h e s t a n d i n g c r o p d a t a p r e s e n t e d i n C h a p t e r 3 and measurements o f d i u r n a l p h o t o s y n t h e s i s and r e s p i r a t i o n . R a t e s of p h o t o s y n t h e s i s and r e s p i r a t i o n were measured as oxygen e v o l u t i o n and d e p l e t i o n , r e s p e c t i v e l y , u s i n g t h e l i g h t : d a r k b o t t l e method ( S t r i c k l a n d and P a r s o n s , 1972; V o l l e n w e i d e r , 1974). D i u r n a l p h o t o s y n t h e s i s e x p e r i m e n t s were p e r f o r m e d on s e l e c t e d s p e c i e s of m a c r o a l g a e . R a t e s of p h o t o s y n t h e s i s were d e t e r m i n e d m o n t h l y f o r F u c u s d i s t i c h u s and H e d o p h y l l u m s e s s i l e and s p o r a d i c a l l y f o r a d d i t i o n a l s p e c i e s ( L e a t h e s i a d i f f o r m i s , Neorhodomela l a r i x , C l a d o p h o r a s p p . , e t c . ) as t h e i r a b u n d a n c e s w a r r a n t e d . The p l a n t m a t e r i a l u s e d i n t h e p h o t o s y n t h e s i s e x p e r i m e n t s was t a k e n from t h e a l g a e c o l l e c t e d d u r i n g t h e s t a n d i n g c r o p s a m p l i n g p r o g r a m . A d d i t i o n a l p l a n t s were c o l l e c t e d , when needed, t o e n s u r e enough m a t e r i a l f o r a t l e a s t f o u r 2-h i n c u b a t i o n s w i t h s u i t a b l e r e p l i c a t i o n . The a l g a e u s e d were c o l l e c t e d o n l y f r o m H e l b y and N u d i b r a n c h , as t h e s e s i t e s were r e p r e s e n t a t i v e of t h e wave e x p o s u r e g r a d i e n t and s u i t a b l e q u a n t i t i e s o f a l l s p e c i e s o f i n t e r e s t c o u l d be f o u n d t h e r e . O n l y h e a l t h y t h a l l i were u s e d i n t h e e x p e r i m e n t s . A p i c a l s e c t i o n s of F u c u s d i s t i c h u s , c o n s i s t i n g o f a t l e a s t f o u r d i c h o t o m i e s , were c u t from whole 172 p l a n t s ; s u c h p i e c e s were g e n e r a l l y r e p r e s e n t a t i v e of whole p l a n t s and i n c l u d e d b l a d e and s t i p e p o r t i o n s . S e c t i o n s of t h a l l i were c u t from t h e b l a d e , d i s t a l t o t h e m e r i s t e m , o f H. s e s s i l e . F o r a l l o t h e r s p e c i e s , e i t h e r whole p l a n t s ( U l v a f e n e s t r a t a , H a l o s a c c i o n amer icanum , d i f f o r m i s ) , whole b r a n c h e s ( C o r a l l i n a v a n c o u v e r i e n s i s , C r y p t o s i p h o n i a  woodi i , N e orhodomela l a r i x ), o r clumps ( C l a d o p h o r a spp.) were u s e d whenever p o s s i b l e . In e a c h c a s e , t h e p l a n t m a t e r i a l u s e d was as r e p r e s e n t a t i v e as p o s s i b l e of t h a t c o l l e c t e d a t t h e s t u d y s i t e . The a l g a e were c o l l e c t e d and p r e p a r e d ( i . e . c u t t o s i z e and c l e a n e d o f most e p i p h y t e s ) t h e day p r e v i o u s t o t h e p h o t o s y n t h e s i s e x p e r i m e n t s . The p l a n t s were m a i n t a i n e d o v e r n i g h t i n water t r o u g h s i n a g r e e n h o u s e a t t h e B a m f i e l d M a r i n e S t a t i o n . L i g h t c o n d i t i o n s (PFD and d u r a t i o n ) were c o m p a r a b l e t o t h o s e i n n a t u r e , a s t h e g r e e n h o u s e f i l t e r e d l e s s t h a n 15% of t h e ambient s u n l i g h t . The w ater t r o u g h s were e q u i p p e d w i t h 45 urn f i l t e r e d s e a w a t e r ( f r o m 20 m d e p t h i n B a m f i e l d I n l e t ) and b u b b l e d a i r ( f o r m i x i n g ) . T h i s t r e a t m e n t s h o u l d have r e d u c e d any p o s s i b l e e f f e c t s c u t t i n g t h e p l a n t s m i g h t have had on t h e p h o t o s y n t h e t i c r a t e d e t e r m i n a t i o n s ( H a t c h e r , 1977; D r o m g o o l e , 1978; L i t t l e r and A r n o l d , 1980). The a l g a e were c u t so t h a t a l g a l c o n c e n t r a t i o n s i n t h e 300 ml BOD b o t t l e s u s e d i n t h e e x p e r i m e n t s d i d not e x c e e d I. 0 g d r y wt J o h n s t o n (1969) f o u n d t h a t t h e use o f up 173 t o 0.3 g d r y wt a l g a e l " 1 s e a w a t e r i n e x p e r i m e n t s up t o 24 h i n d u r a t i o n d i d n o t a l t e r t h e r e s u l t s due t o n u t r i e n t o r c a r b o n d i o x i d e d e p l e t i o n i n t h e b o t t l e s . One would e x p e c t , however, t h a t t h e p o s s i b l e e f f e c t s of e n c l o s i n g a l g a e i n b o t t l e s would depend on t h e s p e c i e s u s e d and ambient e n v i r o n m e n t a l c o n d i t i o n s . A l t h o u g h he c o u l d n o t e x p l a i n h i s r e s u l t s , Buesa (1975) f o u n d t h a t i n c r e a s i n g b o t t l e s i z e t o c a . 1 l i t e r and u s i n g 20-195 mg d r y wt a l g a e l " 1 r e s u l t e d i n h i g h e r r a t e s o f p h o t o s y n t h e s i s . L i t t l e r (1979) o b s e r v e d t h a t t h e e f f e c t s o f b o t t l e s i z e and a l g a l c o n c e n t r a t i o n on measurement of p h o t o s y n t h e s i s v a r i e d w i t h t h e s p e c i e s u s e d . S i g n i f i c a n t d i f f e r e n c e s were f o u n d w i t h U l v a l o b a t a ( K u t z . ) S e t c h . and G a r d n . , w h i c h has v e r y h i g h r a t e s o f p h o t o s y n t h e s i s ; t h e r e were no s i g n i f i c a n t d i f f e r e n c e s f o r C o l p o m e n i a s i n u o s a (Roth) D e r b . and S o l . , w h i c h p h o t o s y n t h e s i z e s a t a v e r y low r a t e . The use o f two hour i n c u b a t i o n s and s m a l l q u a n t i t i e s o f p l a n t m a t e r i a l i n t h i s s t u d y s h o u l d have l i m i t e d any p o s s i b l e b o t t l e e f f e c t s and p r o v i d e d a c c u r a t e measurements of a l g a l p h o t o s y n t h e s i s o v e r s h o r t t i m e p e r i o d s . The s e a w a t e r u s e d i n t h e e x p e r i m e n t s was c o l l e c t e d f r o m t h e s u r f a c e 10-20 m o f f s h o r e o f t h e s t u d y s i t e from w h i c h t h e a l g a e o r i g i n a t e d , f i l t e r e d t h r o u g h 45 urn N i t e x s c r e e n i n g t o remove l a r g e r p h y t o p l a n k t o n , z o o p l a n k t o n and d e b r i s , and s t o r e d i n p o l y e t h y l e n e c a r b o y s o v e r n i g h t . The water was 174 shaken a t i n t e r v a l s f o r one h o u r p r i o r t o use t o e q u i l i b r a t e d i s s o l v e d oxygen w i t h a t m o s p h e r i c l e v e l s ( L i t t l e r , 1979). The d i u r n a l p h o t o s y n t h e s i s e x p e r i m e n t s were begun a t 0600 h o r s u n r i s e ( d u r i n g t h e f a l l and w i n t e r ) and c o n t i n u e d f o r c a . 14 h ( u n t i l s u n s e t d u r i n g t h e f a l l and w i n t e r ) . C o n t i n u o u s l y r u n n i n g s e t s of two-hour i n c u b a t i o n s were p e r f o r m e d t h r o u g h o u t t h e day. E a c h i n c u b a t i o n s e t c o n s i s t e d of 3-6 l i g h t b o t t l e s and two d a r k b o t t l e s . F o u r l i g h t and f o u r d a r k c o n t r o l b o t t l e s ( w i t h o u t m a c r o a l g a e ) were e s t a b l i s h e d t o c o r r e c t f o r p l a n k t o n and b a c t e r i a l m e t a b o l i s m . The l i g h t b o t t l e s m e asured n e t p h o t o s y n t h e s i s and t h e d a r k b o t t l e s , r e s p i r a t i o n ; t h e sum o f t h e two v a l u e s e q u a l e d g r o s s p h o t o s y n t h e s i s . . M i x i n g was p r o v i d e d e v e r y 15 min by p l a c i n g t h e b o t t l e s on m a g n e t i c s t i r r e r s ( e a c h BOD b o t t l e c o n t a i n e d a T e f l o n - c o a t e d m a g n e t i c s t i r r i n g b a r ) f o r c a . 1-2 m i n u t e s . The e x p e r i m e n t s were run under n a t u r a l l i g h t i n a wet t a b l e i n t h e g r e e n h o u s e . F l o w i n g s e a w a t e r a r o u n d th e b o t t l e s m a i n t a i n e d w ater t e m p e r a t u r e s ± 1°C t h a t of t h e s u r f a c e w ater i n B a m f i e l d I n l e t . P h o ton f l u x d e n s i t y was measured w i t h a LICOR Model LI-500 I n t e g r a t o r (Lambda I n s t r u m e n t C o r p o r a t i o n ) . Oxygen c o n c e n t r a t i o n was measured w i t h a Beckman Model 0260 Oxygen A n a l y z e r e q u i p p e d w i t h BOD S t i r r e r . The oxygen meter was c a l i b r a t e d u s i n g t h e W i n k l e r t i t r a t i o n method ( S t r i c k l a n d and P a r s o n s , 1972). V a l u e s were c o n v e r t e d t o c a r b o n e q u i v a l e n t s u s i n g a p h o t o s y n t h e t i c 175 q u o t i e n t (PQ) of 1.20 and a r e s p i r a t o r y q u o t i e n t (RQ) of 1.00 ( W e s t l a k e , 1963; S t r i c k l a n d and P a r s o n s , 1972). The p l a n t s i n e a c h BOD b o t t l e were p l a c e d i n s e p a r a t e , l a b e l l e d aluminum c o n t a i n e r s , d r i e d a t 105°C f o r a t l e a s t 48 h i n a g r a v i t y c o n v e c t i o n oven, and massed t o t h e n e a r e s t 0.01 g. Net p h o t o s y n t h e s i s and r e s p i r a t i o n r a t e s a r e r e p o r t e d as mg C g d r y wt" 1 h " 1 . The m e t h o d o l o g y u s e d i s e s s e n t i a l l y t h a t o f L i t t l e r and c o - w o r k e r s ( L i t t l e r and M u r r a y , 1974; L i t t l e r , 1979; L i t t l e r e t a l . , 1979; L i t t l e r and A r n o l d , 1980); however, t h e i n c u b a t i o n p e r i o d s were s h o r t e r (2 h vs 4-6 h) and d i u r n a l c h a n g e s were e x a m i n e d . T h e s e m o d i f i c a t i o n s a l l o w e d f o r much g r e a t e r a c c u r a c y i n d e t e r m i n i n g d a i l y p r o d u c t i v i t y (Ramus and R o s e n b e r g , 1980). D i u r n a l and m o n t h l y d i f f e r e n c e s i n n e t p h o t o s y n t h e s i s and r e s p i r a t i o n (where p o s s i b l e ) were t e s t e d u s i n g a n a l y s i s of v a r i a n c e t e c h n i q u e s (UBC*GENLIN). D i u r n a l c o n d i t i o n s ( i . e . t i m e o f day) were not i d e n t i c a l i n a l l months compared; however t h e y g e n e r a l l y d i f f e r e d by l e s s t h a n one hour and l i g h t c o n d i t i o n s were s i m i l a r d u r i n g t h e r e s p e c t i v e i n c u b a t i o n s . Thus, t h e ANOVAs p e r f o r m e d s h o u l d be c o n s i d e r e d v a l i d t e s t s of m o n t h l y and d i u r n a l d i f f e r e n c e s i n p h o t o s y n t h e s i s. The a p p e a r a n c e of b u b b l e s i n t h e BOD b o t t l e s was o b s e r v e d o n l y o c c a s i o n a l l y , and g e n e r a l l y o n l y w i t h t h o s e s p e c i e s w i t h v e r y h i g h r a t e s of p h o t o s y n t h e s i s 176 ( f e n s t r a t a , C l a d o p h o r a s p p . , N_;_ l a r i x ). The d a t a from t h o s e b o t t l e s i n w h i c h b u b b l e s a p p e a r e d were compared w i t h t h e v a l u e s from " b u b b l e - f r e e " b o t t l e s and i f t h e c a l c u l a t e d p h o t o s y n t h e s i s r a t e s a p p a r e n t l y d i f f e r e d , t h e f o r m e r v a l u e s were n o t i n c l u d e d i n any f u r t h e r a n a l y s e s ( t h i s o c c u r r e d o n l y r a r e l y ) . In most c a s e s , t h e oxygen c o n c e n t r a t i o n a t t h e end of an i n c u b a t i o n was above s a t u r a t i o n l e v e l s . T h e s e e l e v a t e d oxygen l e v e l s may have i n h i b i t e d p h o t o s y n t h e s i s and e n h a n c e d r e s p i r a t i o n ( T o l b e r t , 1974; L i t t l e r , 1979). Dromgoole (1978) n o t e d a h y p e r b o l i c r e l a t i o n s h i p between d a r k r e s p i r a t i o n and oxygen t e n s i o n and a l i n e a r r e d u c t i o n i n a p p a r e n t p h o t o s y n t h e s i s w i t h i n c r e a s i n g oxygen c o n c e n t r a t i o n . Thus, t h e p r e s e n t e d r a t e s a r e i n a l l p r o b a b i l i t y l o w e r t h a n t h o s e i n n a t u r e . A l t h o u g h t h i s adds an unknown e r r o r t o t h e p r o d u c t i v i t y c a l c u l a t i o n s , t h i s e r r o r i s a c o n s e r v a t i v e one and p r o b a b l y q u i t e s m a l l (< 10%; see H a t c h e r e t a l . , 1977). D a i l y n e t p h o t o s y n t h e s i s p e r g d r y w e i g h t o f a l g a e was c a l c u l a t e d f o r e a c h s p e c i e s f o r e a c h d i u r n a l p h o t o s y n t h e s i s e x p e r i m e n t . T h e r e a p p e a r e d t o be few d i u r n a l c h a n g e s i n r e s p i r a t i o n , a l t h o u g h t h e l i m i t e d r e p l i c a t i o n made t e s t s of t h i s u n f e a s i b l e . T o t a l d a i l y r e s p i r a t i o n was c a l c u l a t e d as t h e mean of t h e h o u r l y d i u r n a l r e s p i r a t i o n r a t e s t i m e s t w e n t y - f o u r . The summed d i u r n a l p h o t o s y n t h e s i s was a d j u s t e d f o r n i g h t t i m e r e s p i r a t i o n , a s s u m i n g t h a t t h e n i g h t r e s p i r a t i o n r a t e e q u a l l e d t h e mean d i u r n a l r e s p i r a t i o n r a t e . 177 D i u r n a l p h o t o s y n t h e s i s was c a l c u l a t e d as t h e a r e a under t h e c u r v e o f p h o t o s y n t h e s i s r a t e s v s t i m e of day f o r e a c h e x p e r i m e n t . E x t r a p o l a t i o n s t o s u n r i s e and s u n s e t were made a s s u m i n g t h a t t h e p h o t o s y n t h e s i s r a t e s f o r t h e f i r s t and l a s t i n c u b a t i o n s of t h e e x p e r i m e n t , r e s p e c t i v e l y , c o n t i n u e d t o s u n r i s e and s u n s e t . P h o t o s y n t h e t i c e f f i c i e n c y (PSE) was c a l c u l a t e d a s n e t d a i l y p h o t o s y n t h e s i s d i v i d e d by t o t a l d a i l y p h o t o n f l u x f o r t h e day on w h i c h t h e e x p e r i m e n t was p e r f o r m e d . A l g a l p r o d u c t i v i t y p e r s q u a r e meter of i n t e r t i d a l s u b s t r a t e was c a l c u l a t e d f o r e a c h s i x - w e e k s a m p l i n g i n t e r v a l u s i n g t h e e q u a t i o n s p r e s e n t e d e a r l i e r . The mean s t a n d i n g c r o p and median d a t e f o r e a c h i n t e r v a l were u s e d t o e s t i m a t e p r o d u c t i v i t y between i n t e r v a l s ; t h e s e were t h e n summed t o p r o v i d e an e s t i m a t e of a n n u a l p r o d u c t i v i t y . A l g a l s t a n d i n g c r o p d a t a were c o n v e r t e d t o c a r b o n e q u i v a l e n t s a s s u m i n g t h a t 80% of t h e p l a n t ' s a s h - f r e e ( o r g a n i c ) d r y w e i g h t was c a r b o h y d r a t e , and 40% o f t h i s was c a r b o n ( i . e . g C = g a s h -f r e e d r y wt x 0.32; W e s t l a k e , 1963; A t k i n s o n and S m i t h , 1983). A s h - f r e e w e i g h t s were d e t e r m i n e d by c o m b u s t i o n a t 550°C f o r t w e l v e h o u r s ( P a i n e , 1971). Two d i f f i c u l t i e s were e n c o u n t e r e d when u s i n g t h e c a l c u l a t e d d a i l y p h o t o s y n t h e s i s v a l u e s t o e s t i m a t e p r o d u c t i v i t y o v e r l o n g e r p e r i o d s : t h o s e of t i d a l e x p o s u r e and v a r y i n g l i g h t c o n d i t i o n s . The r e s u l t s of t h e PS v s I e x p e r i m e n t s f o r a number o f t h e a l g a e ( s e e A p p e n d i x A) 178 showed t h a t p h o t o s y n t h e s i s was g e n e r a l l y s a t u r a t e d a t f a i r l y low l e v e l s (<200 uE n r 2 s" 1 ) and t h e p l a n t s s h o u l d be p h o t o s y n t h e s i z i n g a t maximum r a t e s on a l l but o v e r c a s t d a y s . L i g h t l i m i t a t i o n m i ght be o c c u r r i n g i n d i s t i c h u s (due t o s e l f - s h a d i n g ) and i n IL s e s s i l e and C_^  v a n c o u v e r i e n s i s ( p h o t o s y n t h e s i s s a t u r a t e d a t 350-450 uE n r 2 s ~ 1 and t h e s e p l a n t s a r e f o u n d l o w e r on t h e s h o r e ) . B e c a u s e s e l f - s h a d i n g i n F_;_ d i s t i c h u s was a p r o b l e m not e a s i l y s e p a r a b l e from i n c r e a s e i n s t a n d i n g c r o p , no c o r r e c t i o n s were made f o r t h i s f a c t o r i n t h e p r o d u c t i v i t y c a l c u l a t i o n s . In a d d i t i o n , F\ d i s t i c h u s s t a n d i n g c r o p s were r e d u c e d i n summer 1983 compared w i t h summer 1982 (see C h a p t e r 3 ) , s u g g e s t i n g t h a t s e l f - s h a d i n g was p r o b a b l y not a major i n f l u e n c e on d i s t i c h u s p r o d u c t i v i t y . The number of o v e r c a s t d a y s ( c l o u d c o v e r >50% a t 2 of the 3 d a i l y o b s e r v a t i o n s ; see C h a p t e r 2) d u r i n g e a c h s a m p l i n g i n t e r v a l was r e c o r d e d . On o v e r c a s t d a y s , d a i l y p h o t o s y n t h e s i s i n H_j_ s e s s i l e and C^ v a n c o u v e r i e n s i s was assumed t o be 50% t h a t o f t h e v a l u e s c a l c u l a t e d f r o m t h e d i u r n a l e x p e r i m e n t s ( e x c e p t when t h e e x p e r i m e n t a l d a y s were t h e m s e l v e s o v e r c a s t ) and c o r r e c t i o n s were made i n t h e p r o d u c t i v i t y c a l c u l a t i o n s a c c o r d i n g l y . P r o d u c t i v i t y of Neorhodomela l a r i x a t t h e s h e l t e r e d s i t e s was c a l c u l a t e d u s i n g t h e d a t a f o r N u d i b r a n c h Neorhodomela l a r i x . B e c a u s e o f t h e a p p a r e n t l y g r e a t e r amount o f s t r u c t u r a l m a t e r i a l i n t h e t h a l l i o f t h e s h e l t e r e d 179 p l a n t s ( s e e C h a p t e r 3 ) , n e t d a i l y p h o t o s y n t h e s i s of t h e s h e l t e r e d N_;_ l a r i x was assumed t o be 50% t h a t of t h e N u d i b r a n c h p l a n t s (on a d r y w e i g h t b a s i s ) . A number of w o r k e r s have shown t h a t p h o t o s y n t h e s i s by i n t e r t i d a l f u c o i d s , i n c l u d i n g E\ d i s t i c h u s , i s g r e a t e s t i n a i r and when t h e p l a n t s a r e d e s i c c a t e d c a . 25% ( J o h n s o n e t a l . , 1974; B r i n k h u i s e t a l . , 1976; Q u a d i r a t a l . , 1979). However, h i g h e r l e v e l s of w a ter l o s s r e s u l t e d i n d e c r e a s e d r a t e s o f b o t h p h o t o s y n t h e s i s and r e s p i r a t i o n . T h e s e r e s u l t s have been c o n s i d e r e d i n t h e c a l c u l a t i o n o f F ^ d i s t i c h u s p r o d u c t i v i t y as f o l l o w s : 1) Zone I p l a n t s were e x p o s e d f o r c a . 70-90% of t h e t i m e d u r i n g t h e summer, and t h e r e f o r e , d e s i c c a t i o n s t r e s s may have r e d u c e d d a i l y p h o t o s y n t h e s i s . T h u s , v a l u e s of 50% o f t h e c a l c u l a t e d d a i l y p h o t o s y n t h e s i s f o r Zone I F. d i s t i c h u s d u r i n g t h e months of May t o A u g u s t ( i n c l u s i v e ) were u s e d i n t h e p r o d u c t i v i t y c a l c u l a t i o n s ; 2) The Zone I I p l a n t s were e x p o s e d c a . 50% of t h e t i m e and a p p a r e n t l y s u f f e r e d o n l y l i m i t e d d e s i c c a t i o n s t r e s s . No c o r r e c t i o n s were made on t h e c a l c u l a t e d n e t d a i l y p h o t o s y n t h e s i s v a l u e s when u s e d t o e s t i m a t e l o n g - t e r m p r o d u c t i v i t y ; i n f a c t , b a s e d on t h e a b o v e - m e n t i o n e d s t u d i e s , t h e p r o d u c t i v i t y o f Zone I I F\_ d i s t i c h u s may have been u n d e r e s t i m a t e d ; 1 8 0 3) The Zone I I I p l a n t s were e x p o s e d l e s s t h a t 10% of t h e t i m e , and t h u s no c o r r e c t i o n s were a p p l i e d t o t h e d a i l y p h o t o s y n t h e s i s v a l u e s . The o t h e r s p e c i e s s t u d i e d were g e n e r a l l y r e s t r i c t e d t o low e r s h o r e l e v e l s and a p p a r e n t l y l i t t l e a f f e c t e d by d e s i c c a t i o n ; e xtreme s t r e s s u s u a l l y r e s u l t e d i n t h e a l g a ' s d e a t h . Thus, no c o r r e c t i o n s were made when u s i n g t h e d a i l y p h o t o s y n t h e s i s v a l u e s i n the l o n g - t e r m c a l c u l a t i o n s , a s d e c r e a s e s i n s t a n d i n g c r o p due t o d e s i c c a t i o n s t r e s s would a c c o u n t f o r any r e d u c t i o n i n p r o d u c t i v i t y . The s c o p e and d e t a i l of t h i s s t u d y does n o t a l l o w f o r any f i n e r c o r r e c t i o n f a c t o r s to' be a p p l i e d , and i n any c a s e , c o r r e c t i o n f a c t o r s c a n n o t p o s s i b l y a c c o u n t f o r t h e wide f l u c t u a t i o n s i n s u n l i g h t (due t o c l o u d s , o t h e r p l a n t s moving i n t h e water column, e t c . ) , t e m p e r a t u r e , and n u t r i e n t s w h i c h t h e p l a n t s a r e e x p o s e d t o i n n a t u r e (see L i t t l e r e t a l . , 1979). P h y s i o l o g i c a l s t u d i e s of p h o t o s y n t h e s i s a r e needed t o p r o p e r l y e v a l u a t e t h e e f f e c t s o f d e s i c c a t i o n o r l i g h t -l i m i t a t i o n i n F\_ d i s t i c h u s , H. s e s s i l e , C. V a n c o u v e r i e n s i s , and l a r i x . The c o r r e c t i o n f a c t o r s were a p p l i e d b a s e d on t h e a s s u m p t i o n t h a t t h e s e f a c t o r s were r e d u c i n g p h o t o s y n t h e t i c r a t e s , and a 50% r e d u c t i o n u s e d t o s i m p l y " s p l i t t h e d i f f e r e n c e " i n t h e p r o d u c t i v i t y c a l c u l a t i o n s . The main r e a s o n f o r t h e a p p l i c a t i o n of t h e s e c o r r e c t i o n f a c t o r s i s t o r e d u c e t h e p o s s i b l e e r r o r i n t h e p r o d u c t i v i t y 181 c a l c u l a t i o n s and, i f p o s s i b l e , t o make t h e c a l c u l a t i o n s more c o n s e r v a t i v e . In o r d e r t o o b t a i n an e s t i m a t e of t h e t o t a l m a c r o a l g a l p r o d u c t i v i t y i n Zones I and I I a t N u d i b r a n c h ( f o r c o m p a r s i o n p u r p o s e s w i t h t h e o t h e r z o n e s ) , t h e p h o t o s y n t h e s i s d a t a f o r F. d i s t i c h u s , U. f e n e s t r a t a , and C l a d o p h o r a s p p . were u s e d t o c a l c u l a t e p r o d u c t i v i t y o f Zone I P e l v e t i o p s i s l i m i t a t a , Zone I I r i d a e a c o r n u c u p i a e and Zone II P o l y s i p h o n i a s pp. , r e s p e c t i v e l y . The p r o d u c t i v i t y v a l u e s r e p o r t e d f o r t h e s e l a t t e r s p e c i e s a r e t h u s o n l y r o u g h a p p r o x i m a t i o n s , as t h e y were c a l c u l a t e d u s i n g d a t a from o t h e r s p e c i e s of s i m i l a r m o r p h o l o g y . M u l i t i p l e r e g r e s s i o n a n a l y s e s ( b a c k w a r d s , s t e p w i s e ; MIDAS) were p e r f o r m e d w i t h t h e c a l c u l a t e d d a i l y n e t and g r o s s p h o t o s y n t h e s i s and n e t p r o d u c t i v i t y e s t i m a t e s on s e l e c t e d a b i o t i c e n v i r o n m e n t a l f a c t o r s ( s e e C h a p t e r 3 ) . The v a l u e s u s e d w i t h t h e d a i l y p h o t o s y n t h e s i s e s t i m a t i o n s were t h o s e f o r t h e month i n w h i c h t h e e x p e r i m e n t was c o n d u c t e d . F o r t h e d a i l y p r o d u c t i v i t y c a l c u l a t i o n s , t h e v a l u e s of t h e e n v i r o n m e n t a l f a c t o r s f r o m t h e i n i t i a l s i x - w e e k s a m p l i n g i n t e r v a l i n t h e t i m e s e r i e s were us e d i n t h e r e g r e s s i o n a n a l y s e s . Growth o f s e s s i l e i n Zone I I I a t N u d i b r a n c h was f o l l o w e d by t a g g i n g p l a n t s l o c a t e d a d j a c e n t t o t h e t r a n s e c t s and m o n i t o r i n g b l a d e e l o n g a t i o n u s i n g methods s i m i l a r t o t h o s e o f Mann ( 1 9 7 2 b ) . Ten p l a n t s were t a g g e d on 25 A u g u s t 182 1982 and t e n on 8 September 1982 and t h e i r g r o w t h m o n i t o r e d u n t i l 22 September 1982; a d v e r s e weather c o n d i t i o n s p r e v e n t e d c o n t i n u a t i o n of t h e e x p e r i m e n t u n t i l s p r i n g 1983. Ten p l a n t s were t a g g e d on 30 A p r i l 1983 and 20 May 1983 and m o n i t o r e d u n t i l 9 A u g u s t 1983. Between t h e two d a t a s e t s , i n s i t u g r o w t h d a t a f o r s e s s i l e i s a v a i l a b l e f o r an e n t i r e May t o O c t o b e r p e r i o d . T h r e e b l a d e s were s e l e c t e d on e a c h p l a n t and one, two, or t h r e e 1 cm h o l e s punched 5 cm above t h e j u n c t u r e of t h e b l a d e and h o l d f a s t ( s e s s i l e has no s t i p e ) w i t h a c o r k b o r e r . S m a l l and t h i n n e r ( i n w i d t h ) b l a d e s had one h o l e p u n c h e d i n them w h i l e l a r g e r and w i d e r b l a d e s had t h r e e h o l e s ; t h u s , an a t t e m p t was made t o i n c l u d e a v a r i e t y of b l a d e m o r p h o l o g i e s i n t h e s t u d y . The p l a n t s were c h e c k e d a t two t o f o u r week i n t e r v a l s and t h e movement o f t h e h o l e s up t h e b l a d e measured. New h o l e s were pu n c h e d , i f needed, and b l a d e w i d t h a t t h e new and o l d h o l e s measured. Thus, a v a l u e o f s u r f a c e a r e a of t h a l l u s grown d u r i n g t h e time i n t e r v a l was o b t a i n e d . Wet w e i g h t : s u r f a c e a r e a r a t i o s o f s e s i l e were d e t e r m i n e d by m e a s u r i n g t w e n t y (20) b l a d e s d u r i n g e a c h e x a m i n a t i o n . N o n - t a g g e d p l a n t s were c o l l e c t e d and r e t u r n e d t o t h e l a b o r a t o r y where w i d t h was measured a t i n t e r v a l s of 0%, 25%, 50%, 75% and 100% o f t h e b l a d e l e n g t h . S u r f a c e a r e a was c a l c u l a t e d u s i n g t h e f o r m u l a f o r a rhombus and summing t h e f o u r v a l u e s . Wet:dry w e i g h t c o n v e r s i o n s from 183 t h e s t a n d i n g c r o p s a m p l i n g p r o g ram were a p p l i e d t o o b t a i n d r y w e i g h t : s u r f a c e a r e a r a t i o s . T h e s e v a l u e s were c o n v e r t e d t o c a r b o n e q u i v a l e n t s as d e s c r i b e d p r e v i o u s l y . R a t e s of e l o n g a t i o n a r e e x p r e s s e d i n a b s o l u t e terms as mg C b l a d e - 1 d a y " 1 . C o m p a r i s o n s between t i m e i n t e r v a l s were made u s i n g a n a l y s i s o f v a r i a n c e t e c h n i q u e s (UBC*GENLIN). The l o s s of t a g g e d p l a n t s p r e v e n t e d p e r f o r m i n g t h e a n a l y s i s on b l a d e s i z e as a c o v a r i a t e ( i . e . whether one, two o r t h r e e h o l e s had been punched i n t h e b l a d e ) . R e s u l t s The a s h - f r e e ( o r g a n i c ) w e i g h t s f o r s e l e c t e d i n t e r t i d a l m a c r o a l g a e , e x p r e s s e d as g a s h - f r e e wt g d r y w t " 1 , a r e p r e s e n t e d i n T a b l e 25. S e a s o n a l d i f f e r e n c e s i n o r g a n i c c o n t e n t were f o u n d f o r F u c u s d i s t i c h u s , C l a d o p h o r a spp., U l v a f e n e s t r a t a , H a l o s a c c i o n amer icanum , and t h e s h e l t e r e d morph of Neorhodomela l a r i x . O r g a n i c c o n t e n t o f F\_ d i s t i c h u s a t H a i n e s , H e l b y and W i z a r d was g r e a t e s t i n M a rch, A p r i l and May 1983 (ANOVA: F=14.390 9,434df; p=0.00000**; S-N-K a n a l y s i s , p < 0 . 0 l ) . W h i l e s i g n i f i c a n t s e a s o n a l d i f f e r e n c e s were a l s o f o u n d f o r N u d i b r a n c h F\ d i s t i c h u s (F=4.4417 7,46df; p=0.00077), S-N-K a n a l y s i s ( p < 0 . 0 l ) d i d n o t d i v i d e t h e months i n t o v e r y d i s t i n c t g r o u p s . Table 25. Ash-free (organic) dry weight (g AFW g DRY WT-1) for selected macroalgae during each six-week sampling i n t e r v a l . SPECIES JUN AUG SEP NOV APR MAY JUN AUG MEAN Cladophora spp.* 0 . 47 1 0 .458 0 .433 - - 0 . 367 0 . 391 0 . 420 0 .431 C. Vancouveriensis 0 . 332 0 . 289 0 . 263 0 . 240 0. . 273 0 . 264 0. .271 0 . 297 0 . 283 C. woodi i 0. , 46 E. muricata 0. . 75 F. distichus (1)* 0 .773 0 . 772 0 .779 0. , 785 0. 805 0. .815 0. . 768 0 . 766 0. . 782 F. distichus (2)* 0 . 791 0. .807 0. . 764 0. . 732 0. 753 0. . 770 0. 775 0. . 780 0. 774 H. americanum * 0. . 567 0. .690 0 .684 0. 776 0. 563 0. . 596 0. 573 0. .623 0. 647 H. sess i1e 0. .652 0. .673 0. .697 0. 707 0. 683 0. 654 0. 662 0. 677 0. 672 I. cornucopiae 0. 73 L. di fformi s 0. 347 N. l a r i x ( 1 )* 0. 550 0. 481 0. 477 0. 783 0. 865 0. 913 0. 862 0. 864 0. 695 N. l a r i x (2) 0. 696 0. 658 0. 650 0. 670 - 0. 625 0. 648 - 0. 660 P. 1i mi tata 0. 78 Polysiphonia spp. 0. 55 U. fenestrata * 0. 614 0. 681 0. 709 - 0. 647 0. 595 0. 632 0. 614 0. 643 Note: (1) Plants collected from Haines, Helby and Wizard (2) Plants collected from Nudibranch * Signifcant differences between months (ANOVA) Fucus distichus (1) JAN 1983 = 0.757, MAR 1983=0.794 185 A n a l y s i s o f v a r i a n c e f o r m o n t h l y d i f f e r e n c e s i n t h e o r g a n i c w e i g h t of C l a d o p h o r a spp. was s t a t i s t i c a l l y s i g n i f i c a n t (F=4.2365 6 , l 3 7 d f ; p=0.00061). A l t h o u g h t h e r e s u l t s of t h e S-N-K a n a l y s i s ( p < 0 . 0 l ) were not v e r y c l e a r , o r g a n i c w e i g h t was g r e a t e s t i n J u n e , A u g u s t and September 1982. O r g a n i c c o n t e n t i n americanum (F=9.3581 7,57df; p=0.00000) and f e n e s t r a t a (F=5.6663 6,70df; p = 0 . 0 0 0 0 8 ) was g r e a t e s t i n A u g u s t , September and November 1982 (S-N-K a n a l y s i s , p < 0 . 0 l ) . In c o n t r a s t w i t h t h e o t h e r s e c o n d a r y s p e c i e s , o r g a n i c c o n t e n t of t h e s h e l t e r e d morph of N^ l a r i x was l o w e s t d u r i n g J u n e , A u g u s t and September 1982 (F=67.231 7,49df; p=0.00000**;. S-N-K a n a l y s i s , p < 0 . 0 l ) . T a b l e 26 l i s t g e n e r a l m e t e o r o l o g i c a l c o n d i t i o n s , i n c l u d i n g t i m e o f s u n r i s e and s u n s e t , f o r e a c h day on w h i c h d i u r n a l p h o t o s y n t h e s i s e x p e r i m e n t s were p e r f o r m e d . S e l e c t e d d i u r n a l c u r v e s of n e t p h o t o s y n t h e s i s f o r F u c u s  d i s t i c h u s from Zones I and I I a t H e l b y a r e p r e s e n t e d i n F i g u r e I 8 a - c . The c u r v e s shown a r e r e p r e s e n t a t i v e o f a l l t h o s e o b t a i n e d . C a l c u l a t i o n s o f n e t d a i l y p h o t o s y n t h e s i s , t o t a l d a i l y r e s p i r a t i o n , d a i l y and d i u r n a l P/R r a t i o s , p h o t o s y n t h e t i c e f f i c i e n c y ( P S E ) , and t h e mean d i u r n a l r e s p i r a t i o n r a t e a r e g i v e n i n T a b l e 27. R e s u l t s of t h e a n a l y s e s o f v a r i a n c e of F ^ d i s t i c h u s p h o t o s y n t h e s i s and r e s p i r a t i o n by month, z o n e , and t i m e of day ( p h o t o s y n t h e s i s o n l y ) , a r e p r e s e n t e d i n T a b l e 28. T a b l e 2 6 . Summary o f m e t e o r o l o g i c a l d a t a o n t h o s e d a y s when d i u r n a l p h o t o s y n t h e s i s e x p e r i m e n t s w e r e p e r f o r m e d . DATE L I G H T ( 1 ) A I R ( 2 ) H 2 0 ( 2 ) SUNR ISE SUNSET CLOUDS 12 J U N 1982 2 9 . 6 14 . 8 - 1 9 .8 15 . 5 - 1 6 . 0 0 4 0 6 2 0 1 8 0 % 22 J U N 1982 3 0 . 5 15 . 0 - 1 9 . 2 \4 . 0 - 1 6 . 0 0 4 0 6 2 0 2 2 2 0 % 26 JUN 1982 22 . 9 14 . 0 - 1 9 . 0 14 . 5 - 1 5 . 8 0 4 0 8 2 0 2 3 * 100% 10 J U L 1982 28 . 2 15 . 0 - 1 8 . 6 15 . 2 - 1 7 . 2 0 4 1 7 2 0 1 8 10% 7 AUG 1982 4 0 . 1 16 . 2 - 2 3 . 8 14 . 0 - 1 6 . 8 0 4 5 2 1944 0% 19 AUG 1982 38 . 0 12 . 9 - 2 4 . 5 14 . 4 - 1 7 . 3 0 5 0 9 1923 0 % 2 SEP 1982 31 . 8 13 . 8 - 2 4 .8 12 . 0 - 1 2 . 5 0 5 2 0 1854 0% 6 SEP 1982 1 1 . 9 14 . 0 - 1 6 . 0 12 . 6 - 1 2 . 9 0 5 3 4 1846 * 100% 20 SEP 1982 8 . 6 13 . 0 - 1 5 • Q 12 . 0 - 1 3 .0 0 5 5 5 1816 * 1 0 0 % 3 OCT 1982 10. 4 8 .0 -11 . 3 10 . 1 - 1 0 . 8 0 6 14 1 748 100% 19 OCT 1982 16 . 6 4 . 0 - 1 4 .0 9 . 7 - 1 0 .0 0 6 3 9 1716 0 % 14 NOV 1982 9 . 6 0 . . 2 - 6 . 3 9 . 6 - 1 0 .0 0 7 2 0 1632 0 % 17 NOV 1982 8. •3 5, . 7 - 8 . 7 9 . 7 - 1 0 .0 0 7 2 5 1629 208. 15 J A N 1983 5. 1 3. . 6 - 7 .8 5 . 1 - 6 . . 5 0 8 0 3 1641 0% 9 FEB 1983 2 . 2 5. . 0 - 8 .0 8 . 1 - 8 . .6 0 7 2 8 1701 * 1 0 0 % 6 MAR 1983 12. 2 7 . . 4 -13 ' . . 2 9 . 4 - 1 0 . . 3 0 6 3 7 1747 * 1 0 0 % 16 APR 1983 34 . 4 6 . 1 -18. .8 1 1 . 0 - 1 2 . .9 0 5 0 4 1858 0 % 20 APR 1983 14 . 8 9 . 8 - 1 2 . .0 12 . 1 - 1 2 . 9 0 4 5 5 1904 * 100% 18 MAY 1983 NA 10. 9 - 17 . 3 13 . 2 - 1 5 . O 0 4 0 3 1950 0% 28 MAY 1983 NA 16 . 2 - 2 8 . 2 16 . 0 - 1 6 . 8 0 3 5 1 2 0 0 4 0% 27 JUN 1983 NA 14 . 0 - 1 6 . 0 15 . 0 - 16 . 0 0 3 4 1 2 0 2 4 5 0 % 29 J U N 1983 3 3 . 5 14 . 2 - 15 . 0 14 . 7 - 1 6 . 0 0 3 4 2 2024 * 1 0 0 % 13 J U L 1983 NA 13. 0 - 1 7 . 1 14 . 0 - 14 . 7 0 3 5 4 2 0 1 6 100% 24 J U L 1983 41 . 6 14 . 7 - 1 9 . 4 16 . 3 - 1 7 . 6 0 4 0 8 2 0 0 4 2 5 % 12 AUG 1983 38 . 0 16 . 0 - 2 0 . 3 14 . 0 - 1 6 . 6 0 4 3 7 1932 0% 24 AUG 1983 13 . 1 13 . 8 - 1 6 . 0 12 . 8 - 1 3 . 0 0 4 5 7 1908 * 1 0 0 % N o t e : ( 1 ) E m-2 d a y - 1 ( 2 ) ' C * T o t a l PFD f o r t h e d a y b e l o w t h e mean d a i l y PFD f o r t h e m o n t h oo T a b l e 2 7 . Summary o f t h e d i u r n a l p h o t o s y n t h e s i s e x p e r i m e n t s f o r F u c u s d i s t i c h u s ( 1 ) mg C g d r y w t - 1 d - 1 ; ( 2 ) x l O E - 0 7 mg C g d r y w t - 1 u E - 1 m-2 d - 1 ; ( 3 ) mg C g d r y w t - 1 h - 1 . DATE NET( 1 ) E i T O T A L ( 1 ) RESP DA I LY P/R D IURNAL P/R P S E ( 2 ) M E A N ( 3 ) RESP HELBY - ZONE I 22 J u n e 1982 7 . 68 2 . 4 0 3 .2 5 . 2 2 . 5 0 . 1 0 ± 0 . 0 5 19 A u g 1 9 8 2 * 5 .51 7 .68 0 . 7 2 .0 1 . 4 0 . 3 2 ± 0 . 2 5 3 O c t 1982 7 . 85 2 . 4 0 3 . 3 9 . 1 7 . 5 0 . 1 0 ± 0 . 0 5 17 Nov 1 9 8 2 * 7 . 9 5 1 . 20 6 .6 2 0 . 5 9 . 5 0 . 0 5 1 0 . 0 2 15 J a n 1983 4 . 7 0 3 . 36 1 . 4 6 . 2 9 . 1 0 . 1 4 1 0 . 0 5 9 F e b 1 9 8 3 * 5 . 6 3 2 . 16 2 . 6 8 . . 8 1 8 . 0 0 . 0 9 1 0 . 0 3 6 Ma r 1983 7 .05 2 . 16 3 . 3 10. . 1 5 . 8 0 . 0 9 1 0 . 0 3 18 May 1983 9 . 28 2 . 4 0 3 . 9 7 . . 3 - 0 . 1 0 1 0 . 0 3 29 J u n e 1983 1 0 . 6 7 2 . 88 3 . 7 6 . 0 3 . 2 0 . 1 2 1 0 . 0 4 13 J u l y 1 9 8 3 * 1 0 . 8 5 3. 6 0 3 . 0 5 . 3 - 0 . 1 5 + 0 . 0 5 12 A u g 1 9 8 3 * 9 .63 3 . 84 2 . 5 5 . 1 2 . 5 0 . 1 6 + 0 . 0 7 TABLE 27, CONTINUED DATE HELBY - ZONE I_I 22 dune 1982 19 Aug 1982* 2 Sep 1982* 3 Oct 1982* 17 Nov 1982* 15 Jan 1983* 9 Feb 1983* 6 Mar 1983* 20 Apr 1983* 18 May 1983 29 June 1983* 13 J u l y 1983* 12 Aug 1983* NET( 1 ) TOTAL( 1 ) PS RESP 11.45 4.08 14.16 3.84 10.20 4.32 8.59 2.64 7.72 2.16 ' 4.41 3.60 6.32 1.44 8.45 3.36 8.41 3.84 12.74 2.16 13.71 3.36 11.43 5.04 10.46 3.84 DAILY  P/R 2 . 8 '3 . 7 2.4 5.9 3.6 1 . 2 4 . 4 2 . 5 2 . 2 5.9 4 . 1 2 . 3 2 . 7 DIURNAL  P/R 4.9 8 . 3 5 . 4 8 . 2 11.3 5.6 13.5 6 . 8 4.8 10.2 6.6 4 . 2 5.4 PSE(2) 3.8 3 . 7 3.2 8 . 3 9.2 8.6 20.0 6.9 5 . 7 4 . 1 2.7 MEAN(3) RESP 0.1710.08 0. 1610. 10 O. 1810.06 0. 1110.06 0.0910.09 0. 1510.07 0.0610.02 0.1410.07 0.1610.05 0.0910.04 O.1410.05 0.21+0.05 0.1610.08 TABLE 2 7 , CONTINUED  DATE NUDIBRANCH 26 d u n e 1 9 8 2 * 10 d u l y 1982 7 Aug 1 9 8 2 * 19 O c t 1982 14 Nov 1 9 8 2 * 16 A p r 1 9 8 3 * 28 May 1 9 8 3 * 27 d u n e 1983 24 d u l y 1 9 8 3 * 24 Aug 1 9 8 3 * NET( 1 ) T O T A L ( 1 ) DA I LY D IURNAL P S E ( 2 ) M E A N ( 3 ) PS RESP P/R P/R RESP 8 . 2 0 5 . 0 4 1.6 1 1 . 0 6 9 . 3 6 1.2 8 . 3 9 4 . 3 2 1.9 6 . 9 9 3 . 6 0 1.9 0 . 7 6 8 . 1 6 0 .1 1 2 . 8 7 5 . 2 8 2 . 4 9 . 6 3 1.44 6 . 7 1 1 . 5 2 3 . 6 0 3 . 2 1 1 . 1 8 3 . 8 4 2 . 9 7 . 0 6 3. '12 2 . 3 3 . 3 3 . 6 0 . 2 1 ± 0 . 1 2 2 . 6 2 . 9 0 . 3 9 + 0 . 2 3 4 . 0 2.1 0 . 1 8 1 0 . 1 0 6 . 0 4 . 2 0 . 1 5 1 0 . 1 4 1.8 0 . 8 0 . 3 7 1 0 . 1 4 5 . 2 3 . 7 0 . 2 2 1 0 . 0 9 1 1 . 3 - 0 . 0 6 1 0 . 0 5 5 . 0 - 0 . 1 5 1 0 . 0 3 5 .2 2 . 7 0 . 1 6 1 0 . 0 3 4 . 7 4 .1 O . 1 3 1 0 . 0 5 N o t e : s i g n i f i c a n t d i u r n a l d i f f e r e n c e s i n p h o t o s y n t h e s i s r a t e s (ANOVA) T a b l e 28. A n a l y s i s of v a r i a n c e of p h o t o s y n t h e s i s and r e s p i r a t i o n of Fucus d i s t i chus from Zones I and II of Helby. PHOTOSYNTHESIS SOURCE SUM OF SQUARES DF MEAN SQUARE F-RATIO PROBABILITY Month Zone Month*Zone Time of Day Month*T i me Zone*T i me M*Z*T Res i dua1 T o t a l 7.3003 1.0392 7.0632 9.0555 22 . 775 1.3848 15.867 133.64 198 . 17 12 • 1 •10 5 50 5 41 578 702 0.60836 1.0392 0.70632 1.8111 0.45551 . 27696 .38700 .23121 0.0. 0. 6312 4944 0549 8332 9701 1979 6738 0.00197 * 0.03443 ns 0.00087 ** 0.00000 ** 0.00014 ** 0.30876 ns 0.00635 ns RESPIRATION Month Zone Month*Zone Res i dual T o t a l 0.34992 4.8490E-03 0.14860 0.90323 1.4121 12 1 10 188 21 1 2.9160E-02 4.8490E-03 1.4860E-02 4.8044E-03 6.0695 1.0093 3.0930 0.00000 ** 0.31637 ns 0.00114 ** D i u r n a l c u r v e s o f net p h o t o s y n t h e s i s f o r Fucus d i s t i c h u s from Zones I and I I at Helby (mean ± 1 s t a n d a r d d e v i a t i o n ) . A) 19 Aug 1982 • = Zone I • = Zone I I 12 Aug 1983 A = Zone I A = Zone II B) 17 Nov 1982 o = Zone I • = Zone I I 9 Feb 1983 * = Zone I A = Zone I I C) 6 Mar 1983 ° = Zone I • = Zone II 29 June 1983 A = Zone I A = Zone II C i - l • ^ P ' 1 3 S i l 193 I © 195 W h i l e s i g n i f i c a n t s e a s o n a l d i f f e r e n c e s i n p h o t o s y n t h e s i s were f o u n d , S-N-K a n a l y s i s ( p < 0 . 0 l ) d i d not c l e a r l y g r o u p t h e months; t h i s i s t h e r e s u l t o f t h e s i g n i f i c a n t Month*Zone i n t e r a c t i o n . The o n l y c l e a r d i s t i n c t i o n s b a s e d on t h e S-N-K a n a l y s i s ( p < 0 . 0 l ) were t h a t t h e Zone II p l a n t s on 19 A u g u s t 1982 and t h e Zone I p l a n t s on 18 May 1983 had h i g h e r p h o t o s y n t h e s i s r a t e s . T h i s i s v e r i f i e d i n t e r m s of n e t d a i l y p h o t o s y n t h e s i s f o r t h e Zone 11/19 A u g u s t 1982 p l a n t s , but not f o r t h e Zone 1/18 May 1983 p l a n t s ( T a b l e 2 7 ) . D i u r n a l d i f f e r e n c e s i n p h o t o s y n t h e s i s were common i n t h e Zone II F\_ d i s t i c h u s , but r a r e i n Zone I p l a n t s . R a t e s of p h o t o s y n t h e s i s were u s u a l l y l o w e s t i n t h e f i r s t i n c u b a t i o n of t h e day (S-N-K a n a l y s i s , p < 0 . 0 l ) ; t h e mid-day i n c u b a t i o n s (#2-4) were a l s o o c c a s i o n a l l y g r o u p e d by S-N-K a n a l y s i s ( p < 0 . 0 l ) a s t h e t i m e s o f h i g h e s t p h o t o s y n t h e s i c r a t e s . Where s i g n i f i c a n t d i f f e r e n c e s i n p h o t o s y n t h e s i s between Zone I and Zone II F\_ d i s t i c h u s were f o u n d , r a t e s were a l w a y s g r e a t e r i n t h e Zone I I p l a n t s . Z o n a l d i f f e r e n c e s i n p h o t o s y n t h e s i s were o b s e r v e d on t h r e e o c c a s i o n s : 22 June 1982, 19 A u g u s t 1982, and 18 May 1983. S t a t i s t i c a l l y s i g n i f i c a n t s e a s o n a l d i f f e r e n c e s i n r e s p i r a t i o n f o r t h e H e l b y d i s t i c h u s were a l s o o b s e r v e d ( T a b l e 2 8 ) ; t h e Month*Zone i n t e r a c t i o n was a l s o s i g n i f i c a n t . S-N-K a n a l y s i s ( p < 0 . 0 l ) d i d not c l e a r l y d i v i d e t h e months; however, r e s p i r a t i o n was g r e a t e s t i n t h e Zone I p l a n t s on 19 August 1982. A n a l y s i s of t h e Month*Zone i n t e r a c t i o n u s i n g 196 t h e r e s p e c t i v e one-way ANOVAs showed s i g n i f i c a n t z o n a l d i f f e r e n c e s i n r e s p i r a t i o n on 6 M a r c h 1983 and 21 J u l y 1983. R e s p i r a t i o n r a t e s were g r e a t e s t i n t h e Zone I I p l a n t s on b o t h d a t e s . Net d a i l y p h o t o s y n t h e s i s showed a s t r o n g s e a s o n a l p a t t e r n i n Zone I I F V d i s t i c h u s , w i t h h i g h e s t r a t e s i n t h e s p r i n g and summer ( T a b l e 2 7 ) . The p a t t e r n was l e s s c l e a r f o r Zone I p l a n t s , a l t h o u g h t h e l a r g e s t v a l u e s were r e c o r d e d d u r i n g spring/summer 1983. T o t a l d a i l y r e s p i r a t i o n , d a i l y P/R and d i u r n a l P/R showed wide and v a r i a b l e f l u c t u a t i o n s . The measure of p h o t o s y n t h e t i c e f f i c i e n c y (PSE) was g r e a t e s t d u r i n g t h e w i n t e r months i n d i s t i c h u s f r o m b o t h z o n e s ; n o t e t h e e s p e c i a l l y h i g h v a l u e s r e c o r d e d on 9 F e b r u a r y 1983. R e s u l t s of t h e m u l t i p l e r e g r e s s i o n a n a l y s e s ( b a c k w a r d s , s t e p w i s e ; MIDAS) of F ^ d i s t i c h u s n e t and g r o s s d a i l y p h o t o s y n t h e s i s on s e l e c t e d a b i o t i c e n v i r o n m e n t a l f a c t o r s a r e p r e s e n t e d i n T a b l e 29. W h i l e none of t h e e n v i r o n m e n t a l f a c t o r s were s i g n i f i c a n t l y r e l a t e d w i t h n e t d a i l y p h o t o s y n t h e s i s of Zone I F ^ d i s t i c h u s , g r o s s d a i l y p h o t o s y n t h e s i s was s t r o n g l y r e l a t e d t o water t e m p e r a t u r e . Water t e m p e r a t u r e was a l s o t h e o n l y s i g n i f i c a n t f a c t o r i n t h e r e g r e s s i o n e q u a t i o n s f o r t h e Zone I I p l a n t s . The M u l t i p l e - R c o e f f i c i e n t s were q u i t e h i g h , i n d i c a t i n g t h a t t h e r e g r e s s i o n e q u a t i o n s a c c o u n t e d f o r 70-89% of t h e v a r i a n c e i n n e t / g r o s s p h o t o s y n t h e s i s . T a b l e 29. R e s u l t s of m u l t i p l e r e g r e s s i o n a n a l y s e s of net and g r o s s d a i l y p h o t o s y n t h e s i s (mg C g dry wt-1 day-1) of Zone I and II Fucus  d i s t i chus from Helby on s e l e c t e d a b i o t i c environmental f a c t o r s . ZONE 1 FUCUS DISTICHUS Net D a i l y P h o t o s y n t h e s i s : MULTIPLE-R = 0.57362 F=4.4135 1,9df p=0.0650 ns NO VARIABLES IN REGRESSION EQUATION Gross D a i l y P h o t o s y n t h e s i s : GROSS PS = O.84(H20-T) + 3.74 MULTIPLE-R = 0.83477 SE = 1.3880 ZONE II FUCUS DISTICHUS Net D a i l y P h o t o s y n t h e s i s : NET PS = O.84(H20-T) - 0.62 MULTIPLE-R = 0.91421 SE = 1.2194 Gross D a i l y P h o t o s y n t h e s i s : GROSS PS = 1.02(H20-T) + 0.69 MULITPLE-R = 0.94179 SE = 1.1745 U3 198 D a i l y P/R r a t i o s ' f o r Zone I F\ d i s t i c h u s were not s i g n i f i c a n t l y c o r r e l a t e d w i t h any of t h e e n v i r o n m e n t a l f a c t o r s . D i u r n a l P/R showed s i g n i f i c a n t p o s i t i v e c o r r e l a t i o n s w i t h n i t r a t e c o n c e n t r a t i o n o f t h e s e a w a t e r (r=0.80l6, p<0.0l) and a n e g a t i v e c o r r e l a t i o n w i t h a i r t e m p e r a t u r e (r=-0.7555, 0.01<p<0.05). P h o t o s y n t h e t i c e f f i c i e n c y (PSE) of t h e Zone I p l a n t s was p o s i t i v e l y c o r r e l a t e d w i t h r a i n f a l l (r=0.8796, p<0.0l) and wave e x p o s u r e (r=0.7450, 0.01<p<0.05); n e g a t i v e c o r r e l a t i o n s were f o u n d w i t h water t e m p e r a t u r e (r=-0.8204, p<0.0l), p h o t o n f l u x d e n s i t y (r=-0.8231, p<0.0l), p e r c e n t t i m e e x p o s e d t o a i r (r=-0.8548, p<0.0l), and g r o s s d a i l y p h o t o s y n t h e s i s (r=-0.7794, 0.01<p<0.05). D i u r n a l P/R r a t i o s i n Zone II F ^ d i s t i c h u s showed p o s i t i v e c o r r e l a t i o n s w i t h s e a w a t e r n i t r a t e c o n c e n t r a t i o n (r=0.69l4, 0.0l<p<0.05) and wave e x p o s u r e (r=0.7383, 0.01<p<0.05). As i n t h e c a s e of Zone I BV d i s t i c h u s , p h o t o s y n t h e t i c e f f i c i e n c y i n Zone I I p l a n t s was p o s i t i v e l y c o r r e l a t e d . w i t h r a i n f a l l (r=0.8379, p<0.0l) and wave e x p o s u r e (r=0.7383, 0.0l<p<0.05) and n e g a t i v e l y c o r r e l a t e d w i t h water t e m p e r a t u r e (r=-0.7280, 0.01<p<0.05), ph o t o n f l u x d e n s i t y (r=-0.7243, 0.01<p<0.05), and a i r e x p o s u r e (r=-0.7594, 0.01<p<0.05). P h o t o s y n t h e t i c e f f i c i e n c y was a l s o n e g a t i v e l y c o r r e l a t e d w i t h n et (r=-0.6459, 0.0l<p<0.05) and g r o s s (r=-0.7798, 0.01<p<0.05) d a i l y p h o t o s y n t h e s i s i n Zone I I F. d i s t i c h u s . 199 S e l e c t e d d i u r n a l p h o t o s y n t h e s i s c u r v e s f o r F ^ d i s t i c h u s from Zone I a t N u d i b r a n c h a r e p r e s e n t e d i n F i g u r e 19. S i g n i f i c a n t s e a s o n a l d i f f e r e n c e s i n p h o t o s y n t h e s i s were f o u n d by a n a l y s i s of v a r i a n c e (F=15.997 9,200df; p=0.0000). S-N-K a n a l y s i s ( p < . 0 l ) d i v i d e d t h e months as f o l l o w s : 10 J u l y 82,16 Apr 83 > 19 O c t 82,24 J u l y 83,27 June 83 > a l l o t h e r d a t e s P h o t o s y n t h e s i s i n N u d i b r a n c h F ^ d i s t i c h u s v a r i e d d i u r n a l l y (F=36.592 5,200df; p=0.0000) and a s i g n i f i c a n t Month*Time i n t e r a c t i o n was a l s o n o t e d (F=4.8853 38,200df; p=0.0000). S i g n i f i c a n t d i u r n a l d i f f e r e n c e s i n p h o t o s y n t h e t i c r a t e s were not o b s e r v e d on o n l y t h r e e o c c a s i o n s ( T a b l e 2 7 ) . The c a l c u l a t e d p h o t o s y n t h e s i s p a r a m e t e r s f o r e a c h d i u r n a l e x p e r i m e n t a r e p r e s e n t e d i n T a b l e 27. Net d a i l y p h o t o s y n t h e s i s was g r e a t e s t i n t h e s p r i n g and summer, however t h e r e a r e no d a t a f o r t h e December 1982 t o March 1983 p e r i o d . T o t a l d a i l y r e s p i r a t i o n , d a i l y and d i u r n a l P/R, and PSE d i d n o t show any c o n s i s t e n t s e a s o n a l p a t t e r n . Mean d i u r n a l r e s p i r a t i o n r a t e d i f f e r e d s i g n i f i c a n t l y between months (F=5.7459 9,64df; P=0.0001), b u t S-N-K a n a l y s i s (p<0.0l) d i d not c l e a r l y d i v i d e t h e d a t a . Figure 19 Diurnal curves of net photosynthesis for Fucus d i s t i c h u s from Zone I at Nudibranch (mean ± 1 standard deviation). • = 10 July 1982 • = 19 Oct 1982 A = 16 Apr 1982 A =28 May 1982 2 0 1 © O 00 rH-H r-°-H i I \ | - ; ' - H ^ I—H M o «* H GO h w • a o o o OP o i — i — i — i — r o « * . « • M m O ( , - 1 , - » « * * P * - 3 8 m ) S J 202 N e i t h e r t h e d a i l y nor d i u r n a l P/R r a t i o had s i g n i f i c a n t c o r r e l a t i o n s w i t h any of t h e a b i o t i c e n v i r o n m e n t a l f a c t o r s m o n i t o r e d . P h o t o s y n t h e t i c e f f i c i e n c y (PSE) was n e g a t i v e l y c o r r e l a t e d w i t h p h o t o n f l u x d e n s i t y (r=-0.7686, 0.0l<p<0.05), a i r t e m p e r a t u r e (r=-0.8761, p < 0 . 0 l ) , water t e m p e r a t u r e (r=-0.7766, 0.01<p<0.05), and n e t (r=-0.8254, P<0.01) and g r o s s ( r = - 0 . 7 l 9 3 , 0.01<p<0.05) d a i l y p h o t o s y n t h e s i s . T h e r e were no s i g n i f i c a n t v a r i a b l e s i n t h e m u l t i p l e r e g r e s s i o n a n a l y s i s of N u d i b r a n c h F\_ d i s t i c h u s g r o s s d a i l y p h o t o s y n t h e s i s on s e l e c t e d a b i o t i c e n v i r o n m e n t a l f a c t o r s (F=1.8537 1,8df; p=0.2105ns; M u l t i p l e - R = 0.43373). However, a s i g n i f i c a n t r e g r e s s i o n e q u a t i o n (F=17.009 3,6df; p=0.0024) was f o u n d f o r net d a i l y p h o t o s y n t h e s i s : NET PS = 1.20(AIR-T) - 2.43(H20-T) + 9 . 0 6 ( A l R E 1 OP) - 51.8 MULTIPLE-R = 0.94593 SE = 1.3690 The p a r t i a l c o r r e l a t i o n c o e f f i c i e n t s f o r t h e s i g n i f i c a n t e n v i r o n m e n t a l f a c t o r s were a l s o q u i t e h i g h : a i r t e m p e r a t u r e r = 0.79884; w a t e r t e m p e r a t u r e r = -0.83949; p e r c e n t t i m e e x p o s e d t o a i r r=0.85914. S e l e c t e d d i u r n a l p h o t o s y n t h e s i s c u r v e s f o r H e d o p h y l l u m  s e s s i l e a r e p r e s e n t e d i n F i g u r e 20a,b. S i g n i f i c a n t s e a s o n a l (F=40.192 I 0 , l 0 6 d f ; p=0.0000) and d i u r n a l d i f f e r e n c e s (F=8.9040 4 , l 0 6 d f ; p=0.0000) i n p h o t o s y n t h e s i s were f o u n d . Diurnal curves of net photosynthesis for Hedophyllum s e s s i l e from Zone III at Nudibranch (mean ± 1 standard d e v i a t i o n ) . A) • = 26 June 1982 O = 27 June 1983 • = 7 Aug 19 82 • = 24 Aug 1983 B) • = 20 Sep 1982 • = 14 Nov 1982 A = 16 Apr 1983 A = 28 May 1983 T a b l e 30. Summary of the d i u r n a l p h o t o s y n t h e s i s e x p e r i m e n t s f o r Hedophy11 urn s e s s i 1 e ( 1 ) mg C g d ry wt-1 d - 1 ; (2) X 1 0 E - 0 7 mg C g d ry wt-1 uE-1 m-2 d - 1 ; (3) mg C g d r y wt-1 h - 1 . DATE NET( 1 ) PS TOTAL(1) RESP DAILY P/R DIURNAL P/R PSE(2) MEAN(3) RESP 26 June 1982 15 .02 4 . 56 3 . 3 5 .0 6.6 0 . 1 9 ± 0 . 2 3 24 J u l y 1982* 8 . 58 5 .04 1 . 7 2 .9 2.0 0. .21+0.09 7 Aug 1982* 5 .33 3 .60 1 . 5 3 .9 1 . 3 0 .15+0.07 20 Sep 1982 6 .08 2 . 16 2 .8 6 . 8 4 . 5 0. .09+0.05 19 Oct 1982 4 .02 2 .40 1 . 7 5 . 1 2.4 0. .10+0.13 14 Nov 1982 1 .66 3 . 12 0 .5 2 .8 1 . 7. 0. .13+0.06 16 Apr 1983 19 .68 2 . 16 9. . 1 15 . 8 5.7 0. 09+0.01 28 May 1983 10 .90 3 . 84 2 . 8 4 . 6 - 0. 16+0.09 27 June 1983 1 1 . 13 5 . 04 2 . 2 3 . 5 - 0. 21+0.13 24 J u l y 1983 9 . 10 3 . 12 2 . 9 5, .0 - 0. 13+0.05 24 Aug 1983* 6 .08 3 . 12 1 . .9 4 . 4 4.6 0. 13+0.07 Note: * s i g n i f i c a n t d i u r n a l d i f f e r e n c e s in p h o t o s y n t h e s i s r a t e s (ANOVA) T a b l e 31. M u l t i p l e r e g r e s s i o n a n a l y s e s of net and g r o s s d a i l y p h o t o s y n t h e s i s (mg C g dry wt-1 day-1) i n Hedophyl1 urn  sess i1e on s e l e c t e d a b i o t i c environmental f a c t o r s . Net D a i l y P h o t o s y n t h e s i s NET PS = 1.56(AIR-T) - 3.78(H20-T) - 2.88(SALINITY) + 2.43(AIREXP) + 71.34 MULTIPLE-R = 0.93623 SE = 2.3470 P a r t i a l C o r r e l a t i o n C o e f f i c i e n t s : A i r Temperature Water Temperature Sa1i n i ty A i r Exposure 0.65953 p=0.0752ns -0.76834 p=0.0259* -0.88315 p=0.0036** 0.88639 p=0.0034** Gross D a i l y P h o t o s y n t h e s i s GROSS PS = 1.92(AIR-T) - 1 .71(SALINITY) + 23.79 MULTIPLE-R = 0.86050 SE = 3.0863 P a r t i a l C o r r e l a t i o n C o e f f i c i e n t s : A i r Temperarture Sa1i n i ty r = 0.73407 p=0.0156* r = -0.79533 p=0.0059** K3 O 2 0 8 A s i g n i f i c a n t Month*Time i n t e r a c t i o n was a l s o n o t e d (F=3.4603 36,106df; p=0.0000); d i u r n a l d i f f e r e n c e s i n p h o t o s y n t h e t i c r a t e s were o b s e r v e d on 24 J u l y and 7 August 1982 and 24 A u g u s t 1983 ( T a b l e 3 0 ) . S-N-K a n a l y s i s (p<0.0l) showed t h a t p h o t o s y n t h e t i c r a t e s were g r e a t e s t on 10 A p r i l 1983 and 26 June 1983, w i t h l i t t l e d i f f e r e n c e between t h e o t h e r months. Net d a i l y p h o t o s y n t h e s i s i n H_;_ s e s s i l e showed a s t r o n g s e a s o n a l p a t t e r n w i t h h i g h e s t r a t e s i n t h e s p r i n g and summer ( T a b l e 3 0 ) . T o t a l d a i l y r e s p i r a t i o n , d a i l y and d i u r n a l P/R and PSE d i d not show any c o n s i s t e n t s e a s o n a l p a t t e r n and were not s i g n i f i c a n t l y c o r r e l a t e d w i t h any of t h e e n v i r o n m e n t a l f a c t o r s m o n i t o r e d . However, n o t e t h a t t h e P/R r a t i o s and PSE were r e l a t i v e l y l a r g e on 16 A p r i l 1983 ( T a b l e 3 0 ) . D a i l y P/R was p o s i t i v e l y c o r r e l a t e d w i t h net (r=0.8880, p<0.0l) and g r o s s ( r = 0 . 8 l 6 0 , 0.0l<p<0.05) d a i l y p h o t o s y n t h e s i s , but d i u r n a l P/R was c o r r e l a t e d s i g n i f i c a n t l y o n l y w i t h n e t d a i l y p h o t o s y n t h e s i s (r=0.7908, 0.01<p<0.05). Mean d i u r n a l r e s p i r a t i o n r a t e s d i d n o t v a r y s e a s o n a l l y (F=l.3194 I 0 , 5 4 d f ; p=0.24403ns). R e s u l t s of t h e m u l t i p l e r e g r e s s i o n a n a l y s i s o f H. s e s s i l e n e t and g r o s s d a i l y p h o t o s y n t h e s i s on s e l e c t e d a b i o t i c e n v i r o n m e n t a l f a c t o r s a r e p r e s e n t e d i n T a b l e 31. The M u l t i p l e - R c o e f f i c i e n t s a r e q u i t e l a r g e ; t h e r e g r e s s i o n e q u a t i o n s a c c o u n t f o r 74% ( g r o s s ) and 88% ( n e t ) of t h e v a r i a n c e i n t h e p h o t o s y n t h e s i s p a r a m e t e r s . O p p o s i n g e f f e c t s T a b l e 3 2 . In s i t u b l a d e g r o w t h i n H e d o p h v 1 1 u m s e s s i 1 e T I M E I N T E R V A L B L A D E G R O W T H Q ) 1 9 8 2 2 5 A U G - 8 S E P 2 7 . 7 ± 2 . . 7 8 S E P - 2 2 S E P 8 . 9 ± 3 . . 0 1 9 8 3 3 0 A P R - 2 0 M A Y 7 . 8 + 1 . . 9 2 0 M A Y - 1 2 J U N 1 1 . 9 ± 3 : . 0 12 J U N - 17 J U L 1 0 . . 7 + O . . 8 17 J U L - 9 A U G 8 , . 2 ± 6 . 2 T O T A L ( 2 ) 1 . 0 0 N o t e : ( 1 ) m g C b l a d e " 1 d ~ ' ( 2 ) g C b l a d e - 1 o v e r t h e s t u d y p e r i o d ho to a r e shown by water and a i r t e m p e r a t u r e , d e s p i t e t h e s e two f a c t o r s b e i n g p o s i t i v e l y c o r r e l a t e d w i t h e a c h o t h e r ( s e e C h a p t e r 2 ) . However, i t s h o u l d be n o t e d t h a t t h e r e a r e no p h o t o s y n t h e s i s d a t a f o r IU_ s e s s i l e f o r t h e w i n t e r and e a r l y s p r i n g , and t h e r e f o r e t h e r e g r e s s i o n e q u a t i o n s p r o b a b l y do n o t r e p r e s e n t a t r u e y e a r - r o u n d view of t h e r e l a t i o n s h i p s between p h o t o s y n t h e s i s i n H_;_ s e s s i l e and t h e e n v i r o n m e n t . B l a d e g r o w t h i n H_;_ s e s s i l e was g r e a t e s t f r o m 8 t o 22 September 1982 ( T a b l e 3 2 ) , however t h i s may have been due t o an e r r o r i n t h e c a l c u l a t i o n of wet w e i g h t : s u r f a c e a r e a r a t i o s ; t h e wet w e i g h t : s u r f a c e a r e a r e g r e s s i o n a t t h i s t i m e d i f f e r e d from t h e o t h e r s , and t h i s was t h e f i r s t t i m e t h e d a t a were c o l l e c t e d . S-N-K a n a l y s i s (p<0.01) d i d not s e p a r a t e t h e o t h e r t i m e i n t e r v a l s . A l t h o u g h no q u a n t i t a t i v e d a t a on H_^  s e s s i l e d e n s i t i e s were o b t a i n e d , q u a l i t a t i v e o b s e r v a t i o n s s u g g e s t t h a t p l a n t d e n s i t y was c a 32 n r 2 ( i . e. two p l a n t s p e r e a c h 25 x 25 cm q u a d r a t s ampled; see C h a p t e r 3 ) . I f one a l s o assumes t h a t t h e r e were s i x b l a d e s p e r p l a n t , t h e t o t a l n e t p r o d u c t i v i t y of H_;_ s e s s i l e d u r i n g t h e rn s i t u g r o w t h e x p e r i m e n t was 192.1 g C i r r 2 . S e l e c t e d d i u r n a l p h o t o s y n t h e s i s c u r v e s f o r v a r i o u s a n n u a l and s e c o n d a r y s p e c i e s a r e p r e s e n t e d i n F i g u r e s 21-27. The c a l c u l a t e d d a i l y p h o t o s y n t h e s i s p a r a m e t e r s f o r t h e s e p l a n t s a r e g i v e n i n T a b l e 33. The l a r g e s t p h o t o s y n t h e t i c r a t e s were o b s e r v e d i n t h e c h l o r o p h y t e s U l v a f e n e s t r a t a ( F i g u r e 27) and C l a d o p h o r a s p p . ( F i g u r e 21) and t h e l o w e s t r a t e s i n t h e r h o d o p h y t e s C o r a l l i n a v a n c o u v e r i e n s i s ( F i g u r e 22) and H a l o s a c c i o n americanum ( F i g u r e 2 4 ) . I n t e r m e d i a t e p h o t o s y n t h e t i c r a t e s ( s i m i l a r t o t h o s e o b s e r v e d i n F. d i s t i c h u s and s e s s i l e ) were n o t e d i n C r y p t o s i p h o n i a woodi i ( F i g u r e 2 3 ) , L e a t h e s i a d i f f o r m i s ( F i g u r e 25) and N eorhodomela l a r i x ( F i g u r e 2 6 ) . Net d a i l y p h o t o s y n t h e s i s and t o t a l d a i l y r e s p i r a t i o n were a l s o g r e a t e r i n t h o s e s p e c i e s w i t h t h e h i g h e r p h o t o s y n t h e t i c r a t e s ( f e n s t r a t a and C l a d o p h o r a spp. ). S i g n i f i c a n t d i u r n a l d i f f e r e n c e s i n p h o t o s y n t h e s i s were f o u n d i n C^ v a n c o u v e r i e n s i s , amer icanum and N_;_ l a r i x , but were n e v e r o b s e r v e d i n t h e o t h e r s p e c i e s ( e x c e p t C l a d o p h o r a spp. from N u d i b r a n c h on 7 A u g u st 1982). T h i s l a c k of d i u r n a l d i f f e - r e n c e s i n p h o t o s y n t h e s i c r a t e s i s due t o two f a c t o r s : 1) t h e l a r g e v a r i a n c e i n p h o t o s y n t h e t i c r a t e s i n t h e s e a l g a e , and (2) t h e f a c t t h a t most of t h e e x p e r i m e n t s w i t h t h e s e s p e c i e s d i d not have e a r l y m o r n i n g i n c u b a t i o n s , where l i g h t i n t e n s i t i e s m i ght have been l i m i t i n g t o p h o t o s y n t h e s i s . The l a c k of s i g n i f i c a n t d i u r n a l d i f f e r e n c e s i n p h o t o s y n t h e s i s by L_j_ d i f f o r m i s i s s u r p r i s i n g , as d i f f e r e n c e s were a p p a r e n t l y o b s e r v e d i n t h e PS v s I c u r v e s f o r t h i s p l a n t ( s e e A p p e n d i x A ) . P h o t o s y n t h e s i s i n C o r a l l i n a v a n c o u v e r i e n s i s ( F i g u r e 22) showed s i g n i f i c a n t m o n t h l y d i f f e r e n c e s (F=10.567 4,75df; p=0.0000). S-N-K a n a l y s i s ( p<0.0l) d i s t i n g u i s h e d t h e 20 September 1982 e x p e r i m e n t as t h e t i m e o f l o w e s t 212 Figure 21 Diurnal curves of net photosynthesis for Cladophora spp. (mean ± 1 standard d e v i a t i o n ) . • = 2 Sep 1982 • = 3 Oct 1982 A = 24 J u l y 1983 0600 1000 1400 T i m e ( P S T ) 1800 214 Figure 22 Diurnal curves of net photosynthesis for C o r a l l i n a vancouveriensis. (mean ± 1 standard deviation). • = 7 Aug 1982 • = 20 Sep 1982 A =18 Apr 1983 215 ( f_q . iCap 3 . o 3m ) Sd. 216 Figure 23 Diurnal curve of net photosynthesis for Cryptosiphonia woodii (mean ± 1 standard d e v i a t i o n ) . —I 1 1 1 1 1 1— 0600 1000 1400 1800 Time ( P S T ) 218 Figure 24 Diurnal curves of net photosynthesis for Halosaccion americanum (mean ± 1 standard d e v i a t i o n ) . • = 26 June 1982 • = 19 Oct 1982 219 Diurnal curves of net photosynthesis for Leathesia difformis (mean ± 1 standard deviation). • = 12 June 1982 • = 29 June 1983 A = 13 July 19E3 — i 1 1 1 r 1 1 — 0 6 0 0 1000 1400 1800 T i m e ( P S T ) ho ho M 222 Figure 26 Diurnal curves of net photosynthesis for Neorhodomela l a r i x . (mean ± 1 standard d e v i a t i o n ) . • = 10 July 1982 26 May 1983 27 June 1983 7 I Z — 1 1 1 • 1 r-0600 1000 1400 1800 T i m e ( P S T ) Figure 27 Diurnal curves of net photosynthesis for Ulva fenestrata (mean ± 1 standard d e v i a t i o n ) . • = 2 Sep 1982 • = 18 May 1983 A = 24 Aug 1983 8 . 0 - 1 9.74 6 .0 -6 a w 00 8.0 U l v a - ~ Z - - i 1 1 T r 0 6 0 0 I 1 1 lOOO 1 4 0 0 T i m e ( P S T ) i r 1800 tS3 T a b l e 33. Summary of d i u r n a l p h o t o s y n t h e s i s experiments f o r s e l e c t e d i n t e r t i d a l macroalgae. (1) mg C g dry wt-1 d-1; (2) xlOE-07 mg C g d r y wt-1 uE-1 m-2 d-1; (3) mg C g dry wt-1 h-1. SPECIES/DATE NET( 1 ) PS TOTAL(1) RESP DAILY DIURNAL P/R P/R PSE(2) MEAN(3) RESP C. Vancouver i ens i s 26 June 1982 . 7 Aug 1982* 6 Sep 1982 20 Sep 1982* 16 Apr 1983* 7 .57 5 . 55 6 .89 4 . 38 5.87 3.12 3.84 0. 48 0. 72 4 . 32 2 . 4 1 .4 14 . 4 6 . 1 1 . 4 4.4 3.4 29.0 13.3 3 . 3 3.3 1 .4 2 -.4 3.3 1 . 7 O. 13+0.10 0.16±0.17 0.02±0.01 0.03±0.01 0.18 C. woodi i 20 Apr 1983 13.68 5.04 2.7 7.0 9.2 0.21+0.08 TABLE 3 3 , CONTINUED S P E C I E S / D A T E NET( 1 ) PS TOTAL (1 RESP C l a d o p h o r a s p p . 2 Sep 1982 3 O c t 1982 H e l b y 33 . 54 1 2 . 4 7 1 1 .28 3 . 1 2 C 1 a d o p h o r a s p p . 7 Aug 1 9 8 2 * 6 S e p 1982 20 Sep 1982 24 J u l y 1982 N u d i b r a n c h 31 .79 4 0 . 2 6 27 . 74 35 . 84 9 . 12 8 . 4 0 6 . 0 0 9 . 36 H. amer i c anum 26 J u n e 1 9 8 2 * 20 S e p 1 9 8 2 * 19 O c t 1 9 8 2 * 24 J u l y 1 9 8 3 * 7 .46 7 . 30 3 . 8 7 6 . 27 2 . 4 0 1 .68 2 .88 4 . 8 0 DA I LY D IURNAL P S E ( 2 ) M E A N ( 3 ) P/R P/R RESP 3 . 0 6 . 8 1 1 . 0 0 . 4 7 ± 0 . 19 4 . 0 9 . 7 1 2 . 0 O . 1 3 + 0 . 0 7 3 . 6 7 . 0 7 . 9 0 . 3 8 ± 0 . 3 1 4 . 8 9 . 7 3 4 . 0 0 . 3 5 ± 0 . 2 5 4 . 6 9 . 9 2 1 . 0 0 . 2 5 ± 0 . 1 0 3 . 8 6 . 5 8 . 0 0 . 3 9 ± 0 . 1 9 3.1 6 . 0 3 . 3 0 . 1 0 + 0 . 0 7 4 . 3 9 . 7 8 . 5 0 . 0 7 1 0 . 0 3 1.3 4 . 2 2 . 3 0 . 1 2 1 0 . 1 2 1.3 2 . 7 1.5 0 . 2 0 + 0 . 12 TABLE 33, CONTINUED SPECIES/DATE NET( 1 ) PS TOTAL(1) RESP DAILY  P/R DIURNAL P/R PSE(2) MEAN(3) RESP L. d i f f o r m i s 22 dune 1982 29 June 1983 13 J u l y 1983 8 . 73 19.62 25.02 5.04 3.12 15 . 60 1 . 7 6 . 3 1 . 6 3 . 3 8 .7 3.6 2.0 5.9 0 . 2 1 ± 0 . 1 8 0 .13 0.65+0.26 N. 1ar i x 12 June 1982* 10 J u l y 1982* 6 Sep 1982 28 May 1983* 27 June 1983 14 . 25 12.00 16,72 17.85 18 . 98 4 . 32 13.92 5 . 76 2.88 •8.16 3 . 3 0 .9 2 . 9 6 . 2 2 . 3 5 . 4 1 .9 6 . 7 10.5 4 . 1 3 . 9 3 . 1 14 . 0 4 . 4 0 . 1 8 ± 0 . 1 1 0 . 5 8 ± 0 . 3 5 0 . 2 4 ± 0 . 0 9 0.12+0.02 0 . 3 4 ± 0 . 0 8 U. f e n e s t r a t a 2 Sep 1982 18 May 1983 24 Aug 1983 48.58 22 . 19 52 . 70 19.68 10. 56 12.96 2.5 2 . 1 4 . 1 5 . 5 3.8 8 . 3 15.0 40.0 Note: * s i g n i f i c a n t d i u r n a l d i f f e r e n c e s in p h o t o s y n t h e s i s r a t e s (ANOVA) 0 . 8 2 ± 0 . 1 7 0 . 4 4 ± 0 . 1 8 0 . 5 4 ± 0 . 0 9 00 p h o t o s y n t h e t i c r a t e s ; t h i s i s a l s o v e r i f i e d i n terms of n e t d a i l y p h o t o s y n t h e s i s ( T a b l e 3 3 ) . A l t h o u g h an ANOVA was n o t p e r f o r m e d , i t would a p p e a r t h a t r e s p i r a t i o n r a t e s i n C. V a n c o u v e r i e n s i s were much r e d u c e d i n September 1982, w i t h l i t t l e d i f f e r e n c e between t h e o t h e r months. D a i l y and d i u r n a l P/R r a t i o s were a l s o g r e a t e s t i n September 1982 ( T a b l e 3 3 ) . C l a d o p h o r a spp. ( F i g u r e 21) a l s o showed s i g n i f i c a n t l y d i f f e r e n t m o n t h l y r a t e s o f p h o t o s y n t h e s i s (F=10.488 5,86df; p=0.0000). Lowest r a t e s were o b s e r v e d on 3 O c t o b e r 1982 f o r H e l b y p l a n t s , w i t h t h e o t h e r months not s e g r e g a t e d by S-N-K a n a l y s i s ( p < 0 . 0 l ) . T h e r e were a p p a r e n t l y few d i f f e r e n c e s i n t h e P/R r a t i o s , b u t PSE was g r e a t e s t i n t h e N u d i b r a n c h / S e p t e m b e r 1982 p l a n t s ( T a b l e 3 3 ) . P h o t o s y n t h e s i s i n H a l o s a c c i o n americanum ( F i g u r e 24) d i d n o t d i f f e r s i g n i f i c a n t l y between months (F=2.7521 3,56df; p=0.05103ns), b u t d i d v a r y d i u r n a l l y (F=4.6793 4,56df; p=0.00250). The o t h e r p h o t o s y n t h e s i s p a r a m e t e r s d i d no t show any a p p a r e n t s e a s o n a l p a t t e r n s ( T a b l e 3 3 ) . S i g n i f i c a n t m o n t h l y d i f f e r e n c e s i n L e a t h e s i s d i f f o r m i s p h o t o s y n t h e s i s ( F i g u r e 25 ) were n o t e d (F=32.364 2,37df; p=0.0000); p h o t o s y n t h e s i s was g r e a t e s t on 13 J u l y 1983, but t h e o t h e r two d a t e s d i d n o t d i f f e r (S-N-K a n a l y s i s , p < 0 . 0 l ) . R e s p i r a t i o n r a t e s showed a p a t t e r n s i m i l a r t o t h e p h o t o s y n t h e s i s r a t e s , b ut p h o t o s y n t h e t i c e f f i c i e n c y and t h e P/R r a t i o s were g r e a t e s t on 29 June 1983 ( T a b l e 3 3 ) . 230 P h o t o s y n t h e s i s i n Neorhodomela l a r i x ( F i g u r e 26) v a r i e d m o n t h l y (F=10.046 4,70df;p=0.0000 ) , but S-N-K a n a l y s i s (P<0.01) d i d n o t c l e a r l y s e g r e g a t e t h e months. D i u r n a l d i f f e r e n c e s i n p h o t o s y n t h e t i c r a t e s were f o u n d i n t h e summer 1982 and May 1983 e x p e r i m e n t s . D a i l y and d i u r n a l P/R r a t i o s were g r e a t e s t i n May 1983 w h i l e PSE was g r e a t e s t i n September 1982. U l v a f e n e s t r a t a ( F i g u r e 27) showed s i g n i f i c a n t m o n t h l y d i f f e r e n c e s i n p h o t o s y n t h e t i c r a t e s (F=41.733 2,35df; p=0.0000) w i t h t h e l o w e s t v a l u e s r e c o r d e d on 18 May 1983 (S-N-K a n a l y s i s , p < 0 . 0 l ) . D a i l y P/R r a t i o s were s i m i l a r f o r a l l t h r e e months, a l t h o u g h t h e d i u r n a l P/R r a t i o s d i f f e r e d . R e s p i r a t i o n r a t e s were g r e a t e s t on 2 September 1982 and s i m i l a r on t h e o t h e r two e x p e r i m e n t a l d a y s ( T a b l e 3 3 ) . In terms of net mg C f i x e d g d r y wt" 1 d a y " 1 , p h o t o s y n t h e s i s was g r e a t e s t i n U^ f e n e s t r a t a (22.19-52.70) and C l a d o p h o r a spp. ( 1 2 . 4 7 - 4 0 . 2 6 ) . F a i r l y h i g h r a t e s were a l s o r e c o r d e d f o r C_;_ woodi i ( 1 3 . 6 8 ) , L ^ d i f f ormi s (8.73-25.02) and N. l a r i x ( 1 2 . 0 0 - 1 8 . 9 8 ) . Lowest n e t d a i l y p h o t o s y n t h e s i s r a t e s were o b s e r v e d i n C^ v a n c o u v e r i e n s i s (4.38-7.57) and H. americanum ( 3 . 8 7 - 7 . 4 6 ) . Net d a i l y p h o t o s y n t h e s i s i n F\ d i s t i c h u s r a n g e d between 4.70 and 10.85 i n H e l b y / Z o n e I p l a n t s , 4.41 and 14.16 i n H e l b y / Z o n e II p l a n t s , and 0.76 and 12.87 i n N u d i b r a n c h / Z o n e I p l a n t s . In H. s e s s i l e , n e t d a i l y p h o t o s y n t h e s i s was l o w e s t i n November 1982 (1.66) and h i g h e s t i n A p r i l 1983 ( 1 9 . 6 8 ) . 231 The n e t d a i l y p h o t o s y n t h e s i s r a t e s were u s e d i n c o n j u n c t i o n w i t h e s t i m a t e s of a l g a l s t a n d i n g c r o p ( C h a p t e r 3) t o c a l c u l a t e p r o d u c t i v i t y between e a c h s i x - w e e k s a m p l i n g i n t e r v a l ; t h e s e v a l u e s were t h e n summed t o g i v e an e s t i m a t e o f a n n u a l p r o d u c t i v i t y o v e r t h e June 1982 t o June 1983 p e r i o d . The r e s u l t s of t h e s e c a l c u l a t i o n s f o r e a c h s i t e a r e p r e s e n t e d i n T a b l e s 34 t o 37. I t s h o u l d be n o t e d t h a t , i n most c a s e s , t h e v a l u e of t h e LOS te r m ( l o s s e s due t o h e r b i v o r y , wave a c t i o n , e t c . ) f o r t h i s p e r i o d e x c e e d e d t h e c a l c u l a t e d a n n u a l n e t p r o d u c t i v i t y . T h i s i s t h e r e s u l t of th e r e d u c e d s t a n d i n g c r o p s o b s e r v e d d u r i n g t h e spring/summer 1983 compared w i t h summer 1982. T h i s a l s o s u g g e s t s t h a t t h e p r o d u c t i v i t y v a l u e s c a l c u l a t e d f o r June 1982 t o June 1983 were h i g h e r , a n d / o r l o s s e s l e s s , t h a n f o r t h e same p e r i o d i n 1981-1982. A n n u a l p r o d u c t i v i t y was g r e a t e s t i n t h e F\_ d i s t i c h u s p o p u l a t i o n s i n Zones I and II o f t h e s h e l t e r e d s i t e s (220-740 g C m~2 y e a r " 1 ) . P r o d u c t i v i t y was l o w e r i n t h e Zone I I I (72-192 g C n r 2 y e a r " 1 ) and N u d i b r a n c h / Z o n e I (55.8 g C n r 2 y e a r - 1 ) p o p u l a t i o n s o f t h i s p l a n t . F u c u s d i s t i c h u s p r o d u c t i v i t y was much g r e a t e r i n Zone I a t H a i n e s (740 g C n r 2 y e a r " 1 ) compared w i t h H e l b y (220 g C m"2 y e a r " 1 ) and W i z a r d (275 g C n r 2 y e a r " 1 ) ; t h e r e was l i t t l e d i f f e r e n c e i n the p r o d u c t i v i t y o f t h e Zone II F ^ d i s t i c h u s p o p u l a t i o n s a t th e t h r e e s h e l t e r e d s i t e s . T a b l e 3 4 . D a i l y a n d a n n u a l n e t p r o d u c t i v i t y f o r s e l e c t e d i n t e r t i d a l m a c r o a l g a e a t H a i n e s JUNE AUG SEPT NOV J A N MAR APR MAY JUNE J J ) T J ) J J ) J J 3 J J ] T 0 J J 3 T 0 TOTAL ( 2 ) TO AUG SEPT NOV J A N MAR APR MAY JUNE AUG ZONE I F . d i s t i c h u s LOS( 1 ) 2 .63 - 0 . .92 3 . 10 5 . . 17 NET P R O D U C T I V I T Y ( 1 ) 1 . 13 1 . . 26 3 .08 3 . .02 P/B RAT IO 0 . . 16 0 . . 23 0 . 38 0 . . 59 ZONE I I F. d i s t i c h u s LOS 4 . 27 3 . 23 7 . . 27 0 . 8 0 NET PRODUCT IV I TY 4 . 08 3 . 83 2 . 75 0 . 72 P/B RAT IO 0 . 68 0 . 70 0 . 42 0 . 56 ZONE I I I F. d i s t i c h u s LOS 2 .08 - 0 . . 29 0 . 20 NA NET PRODUCT IV ITY 0 . . 63 O, . 19 0 . 35 NA P/B RAT IO 0 . .36 0 . .68 0 . 4 2 NA L. d i f f o r m i s LOS 0 . .52 0 . 1 1 .004 NA NET PRODUCT IV ITY 0 . 18 0 . 04 .001 NA P/B RAT IO 0 . 43 0 . 47 0 . 4 3 NA - 1 . 13 3 . 39 3 . 69 0 . . 35 788 . 3 2 . 50 1 . . 1 1 2 . 35 2 . 7 0 1 . . 14 7 4 0 . 0 1 .31 0 . . 27 0 , .31 0 . . 49 0 . . 22 2 . 65 0 . 23 0 . 79 -1 . 36 0 . 95 2 . 31 8 3 6 . 3 3 . 1 1 0 . 44 0 . 6 0 1 . 61 2 . 91 7 3 6 . 9 2 . 77 0 . 27 0 . 38 0 . 54 0 . 71 4 . 26 0 . 62 NA NA - 0 . 1 5 0 . 0 6 1 0 0 . 2 0 .53 NA NA 0 . 0 4 0 . 22 72 .0 0 .27 NA NA 0 . 53 0 . 73 3 . 72 0 .62 NA - . 0 0 2 - . 0 08 - 0 . 23 38 . 5 0 . . 50 NA . 0 0 0 3 . 0 0 3 . 017 10 . 3 0 . .43 NA 1 . 0 0 1 .47 1 . 24 5 .04 1 . .75 ho CO hO TABLE 3 4 , CONTINUED JUNE AUG SEPT NOV J A N MAR APR MAY JUNE TO TO TO TO TO TO TO TO T O T A L ( 2 ) TO AUG SEPT NOV J A N MAR APR MAY JUNE AUG ZONE I I I C. v a n c o u v e r i e n s i s LOS .034 .014 • - . 0 1 1 NA NA - . 0 02 - . 0 08 - 0 . 23 8 . 9 . 002 NET PRODUCT IV ITY .01 1 . 004 . 0 005 NA NA . 0 0 6 6 . 0 38 .005 2 . 9 .001 P/B RAT IO 0 . 29 0 . 31 0 . 20 NA NA 0 . 26 0 . 3 0 0 . 2 3 1 . 59 0 . 25 N . 1 a r i x LOS 0 . 33 0 . 2 2 0 . 4 5 NA NA - 0 . 1 5 0 . 1 5 - 0 . 2 2 34 . 0 . 0 7 7 NET PRODUCT IV I TY 0 . 22 0 . 19 0 . 18 NA NA .01 1 . 0 79 .041 3 0 . 7 0 . 1 7 P/B RAT IO 0 . 33 0 . 4 3 0 . 41 NA NA 0 . 4 2 0 . 2 1 0 . 4 5 2 . 25 0 . 5 0 C l a d o p h o r a s p p . LOS - . 005 0 . 2 4 .004 NA NA - . 0 0 5 0 . 1 7 0 . 26 27 . 1 0 . 10 NET PRODUCT IV I TY .041 0 . 19 .003 NA NA . 0 02 0 . 19 0 . 2 3 2 8 . 5 0 . 14 P/B RAT IO 2 . 8 0 3 . 2 8 0 . 6 7 NA NA 0 . 9 4 4 . 2 0 3 . 35 1 5 . 2 3 . 6 7 H. a m e r i c a n u m LOS - . 002 0 . 1 1 0 . 1 5 NA NA - . 0 38 - 0 . 0 4 0 . 0 8 1 0 . 6 . 0 1 5 NET PRODUCT IV I TY .051 . 069 .036 NA NA . 0 0 0 8 . 0 1 2 .029 8 . 4 3 . 0 1 5 P/B RAT IO 0 . 37 0 . 1 2 0 . 24 NA NA 0 . 3 0 0 . 33 0 . 29 1 .65 0 . 3 1 TOTAL LOS TOTAL NET PRODUCT IV ITY 2 1 9 . 6 2 5 2 . 8 N o t e : ( 1 ) mg C m - ! d " 1 ( 2 ) g C m-* y ' ( J u n e 1982 - J u n e 1983 ) NA = n o t a v a l i a b l e T a b l e 35 D a i l y a n d a n n u a l n e t p r o d u c t i v i t y f o r s e l e c t e d i n t e r t i d a l m a c r o a l g a e a t H e l b y . JUNE AUG SEPT NOV J A N MAR APR MAY JUNE TO TO TO TO TO TO TO TO T O T A L ( 2 ) TO AUG SEPT NOV J A N MAR APR MAY JUNE AUG ZONE I F. d i s t i c h u s L 0 S ( 1 ) 0 .83 3 . 15 2 . 36 0 . 69 - 0 . 1 4 - 0 . .07 0 . 25 1 .04 377 .9 -1 .68 NET P R 0 D U C T I V I T Y ( 1 ) 0 . 8 0 0 .95 1 . 04 0 . 47 0 . 2 1 0 . .41 0 . 4 5 0 . 44 2 2 0 . 4 0 . 3 1 P/B RAT IO 0 . 16 0 . 20 0 . 4 1 0 . 65 0 . 22 0 . . 34 0 . 28 0 . 23 2 . 49 0 . 26 ZONE I I F. d i s t i c h u s LOS 4 .69 4 .92 3 . 96 0 . 85 1 . 57 - 0 . 74 0 . 5 9 3 .21 8 4 4 . 9 1.41 NET PRODUCT IV I TY 4 . 13 3 .86 1 . 93 0 . 83 0 . 6 0 0 . 6 0 1 . 4 0 2 . 67 7 1 5 . 2 1 .84 P/B RAT IO o .67 0 . 74 0 . 45 0 . 62 0 . 24 b. 43 0 . 5 3 0 . 74 4 . 4 0 0 . 6 3 C l a d o p h o r a s p p . LOS 0 . 12 0 . 24 0 . 22 . 057 0 0 0 - 0 . 15 2 3 . 4 0 . 5 2 NET PRODUCT IV I TY 0 . 16 0 . 3 0 0 . 1 1 . 034 0 0 0 . 0 08 2 7 . 9 0 . 5 4 P/B RAT IO 2 . 8 0 3 . 39 0 . 73 2 . 52 - - - 4 .51 1 3 . 9 5 3 . 4 3 TOTAL LOS TOTAL NET PRODUCT IV ITY 868 . 3 733 . 1 N3 Co T a b l e 3 5 , CONTINUED JUNE AUG SEPT NOV JAN MAR APR MAY JUNE 12 12 12 12 12 12 12 12 TOTAL TO AUG SEPT NOV JAN MAR APR MAY JUNE AUG ZONE I I I F . d i s t i c h u s LOS 1 .63 1 . .99 0 . 88 NA NA NA 0 . .44 0 . 1 1 2 2 0 . 7 0 . 19 NET PRODUCT IV ITY 1, .33 1 . . 17 0 . 35 NA NA NA 0 . 31 0 . 35 1 5 2 . 3 0 . 44 P/B RAT IO 0 .67 0 . , 74 0 . 45 NA NA NA 0 . 53 0 . 74 3 . 13 0 . 63 L. d i f f o r m i s LOS 0 . .28 . 008 0 NA NA 0 - . 0 3 6 - .031 10 . 42 0 . 35 NET PRODUCT IV ITY 0 . ,09 . 003 0 NA • NA 0 . 0 0 3 .055 39 . 95 0 , 23 P/B RAT IO 0 . 44 0 . 4 7 - NA NA - 1 . 37 1 . 28 3 . 56 1 . 88 U. f e n e s t r a t a LOS 0 . 13 0 . . 20 0 . . 56 NA NA - . 0 3 5 . 0 4 9 0 . 10 44 . 0 0 . 29 NET PRODUCT IV ITY 0 . 14 0 . . 24 0 . .51 NA NA . 004 . 0 6 5 .089 4 5 . 8 7 0 . . 27 P/B RAT IO 6 . 69 7 . 9 0 7 . .48 NA NA 1 . 54 1 . 65 1 . 54 26 . 8 0 6 . 5 0 C. wood i i LOS .044 0 0 NA NA - . 0 8 5 . 0 9 9 .055 4 .94 , • . 0 8 6 NET PRODUCT IV ITY 0 . 0 2 0 0 NA NA . 002 0 . 0 7 .045 5 . . 89 . 0 39 P/B RAT IO 0 . 78 - - NA NA 0 . 78 0 . 8 3 0 . 78 3. . 17 0 . 8 3 C 1 a d o p h o r a s p p . LOS NET PRODUCT IV ITY P/B RAT IO .032 - . 027 0 . . 38 NA NA - . 002 0 . 55 0 . 19 4 8 . .94 . 0 44 . 025 0 . 2 1 0 . 22 NA NA . 008 . 0 4 9 0 . 18 72 . .38 0 . 14 2 . 8 0 3 . 4 0 0 . 73 NA NA 3 .51 4 .02 3 . 51 17 . 97 3 . 8 4 TOTAL LOS " 3 2 9 . 0 TOTAL NET PRODUCT IV ITY 3 1 6 . 4 N o t e : ( 1 ) g C m - 2 d - 1 ( 2 ) g C m " 1 y - ' ( J u n e 1982 t o J u n e 1983 ) ^ NA = n o t a v a i l a b l e i_n T a b l e 36 D a i l y a n d a n n u a l n e t p r o d u c t i v i t y f o r s e l e c t e d i n t e r t i d a l m a c r o a l g a e a t W i z a r d . S P E C I E S JUNE TO AUG AUG TO SEPT SEPT TO NOV NOV TO J A N J A N TO MAR MAR TO APR APR MAY TO TO MAY JUNE T O T A L ( 2 ) JUNE TO AUG ZONE I d i s t i c h u s LOS( 1 ) 2 . 28 3 . 26 1 .47 1 .06 0 . 44 - 0 . . 64 0 . . 6 0 0 . 63 4 25 . 1 . 0 69 NET P R O D U C T I V I T Y ( 1 ) 1 .02 0 . .90 0 . .96 0 . .75 0 . 37 0 , .47 0 . .86 0 . 62 2 7 5 . 3 0 . 66 P/B RAT IO 0 . 16 0 . 19 0 . .40 0 . 57 0 . 32 0 . 31 0 . . 40 0 . 24 2 . 59 O. 25 ZONE I I F . d i s t i c h u s LOS 3 . 1 1 3 .95 3 . 4 9 0 . 7 5 1 . 32 - 1 . 44 . 0 56 3 . 51 734 . 7 1 .43 NET PRODUCT IV ITY 3 . 43 3 .95 1 .68 0 . 7 3 0 . 4 9 0 . 36 1 . 26 2 . 86 6 6 0 . 9 1 .99 P/B RAT IO 0 . .64 0 . 75 0 . 45 0 . 54 0 . 33 0 . 38 0 . 56 0 . . 76 4 . 4 1 0 . 6 3 C l a d o p h o r a s p p . LOS 0 . 25 .037 . 045 0 . 16 . 0 08 .001 - . 0 04 0 . 12 2 5 . 6 . 0 1 7 NET PRODUCT IV ITY 0 . 21 . 094 . 063 . 086 . 0 0 5 . 003 . 026 0 . 14 28 . 7 0 . 22 P/B RAT IO 2 . 8 0 3 . 4 0 0 . 7 1 1.14 0 . 8 9 0 . 6 1 4 . 39 3 . 67 1 7 . 6 3 .51 TOTAL LOS TOTAL NET PRODUCT IV ITY 7 6 0 . 6 89 . ON TABLE 3 6 , CONTINUED S P E C I E S JUNE AUG SEPT NOV J A N MAR APR MAY JUNE I ° I O I O J J ) T O T O T O T O TOTAL ( 2 ) TO AUG SEPT NOV J A N MAR APR MAY JUNE AUG ZONE I I I F. d i S t i c h u s LOS 0 . , 52 2 .48 0 . ,84 NET PRODUCT IV I TY 1 . .02 1 . .41 0 . 39 P/B RAT IO 0 . .66 0 . . 75 0 . 45 NA NA NA 1 , . 1 1 0 . . 27 2 3 3 . 3 . 017 NA NA NA 0 . 73 0 . 8 0 1 9 1 . 8 1 .01 NA NA NA 0 . 55 0 . 76 3 . 1 7 0 . 6 3 L. d i f f o r m i s LOS 0 . 37 . 037 0 o - 0 - . 0 0 0 8 - .08 . 038 15.1 0 , .43 NET PRODUCT IV I TY 0 . 12 . 012 0 0 0 . 0 0 2 9 . 007 . 0 99 1 0 . 3 0 . . 3 1 P/B RAT IO 0 . 44 0 . 48 - - - 1.11 1.51 0 . 9 8 4 . 5 2 1 . 87 U. f e n e s t r a t a LOS 0 . 25 0 . 76 1 .45 NA NA - . 018 . 038 0 . 0 1 1 0 8 . 6 0 . 27 NET PRODUCT IV I TY 0 . 31 0 .83 1 . 30 NA NA . 0 0 3 5 . 036 . 0 29 109 . 3 0 . . 3.1 P/B RAT IO 6 . 6 9 7 . 89 7 .08 NA NA 1 . 32 1 . 84 1 . 6 0 26 . 4 8 . 14 N. l a r i x LOS - . 098 .06 0 . . 30 NA NA - . 0 28 - . 13 0 . 0 4 28 .6 0 . .33 NET PRODUCT IV I TY .045 0 . 27 0 , . 27 NA NA .001 . 032 . 087 3 0 . 9 0 . 49 P/B RAT IO 0 . 30 0 . 98 0 . 43 NA NA 0 . 4 0 1 . 27 0 . 4 8 3 . 86 0 . 49 T O T A L . L O S 3 8 5 . 6 TOTAL NET PRODUCT IV ITY 3 4 2 . 3 N o t e : ( 1 ) g C m - ! d " ' ( 2 ) g C m- * y - ' ( J u n e 1 9 8 2 - J u n e 1983 ) NA = n o t a v a l a i l a b l e N3 Co T a b l e 37 D a i l y and annual net p r o d u c t i v i t y f o r s e l e c t e d i n t e r t i d a l macroa l gae at N u d i b r a n c h SPECIES JUNE AUG SEPT NOV JAN MAR APR MAY JUNE TO TO TO TO TO TO TO TO TOTAL(2) TO AUG SEPT NOV JAN MAR APR MAY JUNE AUG ZONE I F . d i s t i c h u s LOS( 1 ) 0. 25 1.17 0. 55 NA ' NA NA .091 0. 35 103 . 1 0. 33 NET PRODUCTIVITY( 1 ) 0.31 0. 38 0. 23 NA NA NA 0. 24 0.15 55 . 8 0.11 P/B RATIO 0.23 0. 28 0. 33 NA NA NA 0. 36 0. 25 1 . 45 0. 28 P. 1 im i t a t a ( u s e d F. d i s t i c h u s ; d a i l y p h o t o s y n t h e s i s d a t a ) LOS - .034 .056 .053 NA NA NA .094 .037 14.2 .045 NET PRODUCTIVITY .008 .021 .014 NA NA NA .094 .037 7 . 5 .013 P/B RATIO 0. 23 0. 27 0. 33 NA NA NA 0.61 0. 59 6 . 59 1 .92 I. c o r n u c o p i a e ( u s e d U. f e n e s t r a t a d a i l y p h o t o s y n t h e s i s d a t a X 0.5) LOS 0. 25 0. 22 .036 NA NA NA - .03 .039 22 .0 0. 10 NET PRODUCTIVITY 0.21 0.15 0.03 NA NA NA .007 0.03 18.2 .075 P/B RATIO 1 . 77 1.91 1.71 NA NA NA 0.61 0. 59 6 . 59 1 . 92 TOTAL LOS TOTAL NET PRODUCTIVITY 139. 3 81.5 W 00 TABLE 37, CONTINUED SPECIES JUNE AUG SEPT NIV JAN MAR APR MAY JUNE TO TO TO TO TO TO TO TO TOTAL TO AUG SEPT AUG AUG AUG AUG AUG AUG AUG ZONE I I U. f e n e s t r a t a LOS 0 . 26 0 .86 0 .62 NA NA NA 0 0 74 . 2 0.28 NET PRODUCTIVITY 0 . 33 0 .83 6 . 55 NA NA NA 0 0 72.9 0. 34 P/B RATIO 6 .69 7 .48 6 . 33 NA NA NA - - 20. 5 9.16 N. l a r i x LOS 0 . 55 0 .58 0 . 33 NA NA NA - . 18 0.13 59.9 0.76 NET PRODUCTIVITY 0. . 37 0 .39 0 . 18 NA NA NA .022 0. 26 51.9 0.44 P/B RATIO 0. .66 1 .09 0. .98 NA NA NA 1.15 1.15 5 .03 1.31 C. V a n c o u v e r i e n s i s LOS 0. 29 46 . 0. 65 NA NA NA - .014 .007 18 . 3 0.41 NET PRODUCTIVITY 0. 07 .015 0. 1 1 NA NA NA .018 .028 10. 1 .038 P/B RATIO 0. 25 0. 28 . o. 20 NA NA NA 0. 29 0. 28 1 . 30 0. 29 Cladophora spp. LOS .041 0. 85 0. 45 NA NA NA - .013 .066 59.8 .077 NET PRODUCTIVITY 0. 19 0. 80 0. 37 NA NA NA .009 .087 62.4 0.17 P/B RATIO 2 . 80 3 . 76 2 . 12 NA NA NA 3.67 3.51 15.86 3.94 TABLE 3 7 , CONTINUED S P E C I E S JUNE AUG SEPT NOV J A N MAR APR MAY JUNE TO TO TO TO TO TO TO TO TOTAL TO AUG SEPT NOV J A N MAR APR MAY JUNE AUG ZONE I I H. a m e r i c a n u m LOS . 013 - . 027 .073 NA NA NA - . 024 . 0 19 2 . 1 - . 0 06 NET PRODUCT IV ITY . 059 . 075 . 074 NA NA NA . 024 .011 1 0 . 2 . 0 08 P/B RAT IO 0 . 3 7 0 . 38 0 . 23 NA NA NA 0 . 3 1 0 . 3 0 1 . 59 0 . 3 2 F. d i s t i c h u s LOS - . 067 0 . 2 8 - . 079 NA NA NA - . 1 1 0 . 14 7 . 4 . 0 0 5 NET PRODUCT IV ITY .047 .084 .001 NA NA NA . 002 . 065 8 . 5 . 0 2 6 P/B RAT IO 0 . 5 1 1 .42 0 . 33 NA NA NA 1 . 73 0 . 54 4 . 5 3 1.64 P o l y s i p h o n i a s p p . ( u s e d C l a d o p h o r a s p p i . d a i l y p h o t o s y n t h e s i s x 0 . 5 ) LOS 0 . 18 0 . 49 . 029 NA NA NA . 043 0 . 43 5 0 . 2 0 . 1 3 NET PRODUCT IV ITY 0 . 2 2 0 . 39 .026 NA NA NA 0 . 1 1 0 . 3 6 47 . 3 0 . 1 1 P/B RAT IO 2 . 8 5 3 . 77 2 . 1 2 - NA NA NA 3 . 6 7 3 .51 15 . 92 3 . 84 TOTAL LOS TOTAL NET PRODUCT IV ITY 271 .9 2 4 3 . 3 K3 O TABLE 3 7 , CONTINUED S P E C I E S JUNE AUG SEPT NOV J A N MAR APR MAY JUNE TO TO TO TO TO TO TO TO TOTAL TO AUG SEPT NOV J A N MAR APR MAY JUNE AUG ZONE I I I H. s e s s i 1 e LOS 1 . 22 - 1 . 05 0 . 0 8 NA NA NA 0 . 6 3 1.11 82 .0 0 . 9 1 NET PRODUCT IV ITY 1 . 14 0 .51 0 . 6 4 NA NA NA 1.16 0 . 9 2 185 . 1 0 . 6 3 P/B RAT IO 0 . 5 1 0 . 25 0 . 16 NA NA NA 0 . 94 0 . 50 2 . 36 ' • 0 . 4 0 C. V a n c o u v e r i e n s i s LOS 0 . 1 3 0 . 50 . 073 NA NA NA 0 . 1 7 . 016 3 8 . 4 . . 0 9 3 NET PRODUCT IV ITY 0 . 1 4 0 . 15 . 027 NA NA NA . 057 .031 1 7 . 3 . 0 16 P/B RAT IO 0 . 29 0 . 30 0 . 20 NA NA NA 0 . 24 0 . 24 1 . 27 0 . 1 1 TOTAL LOS TOTAL NET PRODUCT IV ITY 1 2 0 . 4 2 02 .4 N o t e : ( 1 ) g C m - 1 d " 1 ( 2 ) g C m " ! y - ' ( J u n e 1 9 8 2 - J u n e 1983 ) NA = n o t a v a i l a b l e 242 Total productivity in Zone III of the sheltered s i t e s generally increased with increasing wave exposure: Haines(252.8) < Helby (316.4) < Wizard (342.3) Species other than di st ichus contributed between 2.85 and 30.1 g C r r r 2 year" 1 in Zone III at Haines (Table 34), while these secondary/annual species had p r o d u c t i v i t i e s of 5.89-72.4 g C r r r 2 year" 1 at Helby (Table 35) and 10.31-109.3 g C n r 2 year" 1 at Wizard (Table 36). Productivity of L. di f formis was greatest at Helby (39.95 g C n r 2 year" 1) but similar at Haines and Wizard (10.3 g C n r 2 y e a r " 1 ) . At Nudibranch, t o t a l productivity was approximately equal in Zone II (243.3 g C n r 2 year"1.) and Zone III (202.4 g C n r 2 year" 1) and lowest in Zone I (81.5 g C n r 2 y e a r " 1 ) . Ulva fenestrata , N^ l a r i x , Cladophora spp., and Polysiphonia spp. accounted for most of the productivity in Nudibranch/Zone II (Table 37), while H^ s e s s i l e dominated Zone III (185.1 g C n r 2 y e a r " 1 ) . Annual P/B ratios in sheltered F\_ distichus ranged between 2.65 and 4.41. P/B ratios were lowest in the Zone I populations and highest in the Zone II populations; there were l i t t l e differences in the ratios between s i t e s . However, the lowest P/B r a t i o (1.45) was observed in 243 Nudibranch/Zone I. The P/B rati o s indicate that F. di st ichus biomass "turns over" 1.5-4.4 times each year. P/B ratios in Cladophora spp. ranged between 13.95 at Helby/Zone II and 17.97 at Helby/Zone III (Table 35). Ulva  fenestrata showed a high turnover of biomass; P/B rati o s ranged between 20.5 and 26.8. P/B ratios in the other species were generally less than 4.0. Hedophyllum s e s s i l e at Nudibranch had an annual P/B r a t i o of 2.36 (Table 37). Differences in the P/B ratios for each time interval were apparent in the sheltered F^ di st ichus populations. Ratios were highest in the f a l l , winter and spring in the Zone I plants, r e f l e c t i n g the possible e f f e c t s of desiccation on photosynthesis rates as incorporated into the calcula t i o n s . In contrast, P/B rati o s in the Zone II and Zone III populations were greatest during the summer. There was l i t t l e seasonal v a r i a t i o n in the P/B r a t i o of Nudibranch/Zone I F\_ di st ichus (Table 37). Daily productivity (g Cm" 2 day" 1) showed a seasonal pattern similar to that of the P/B rati o s discussed above, but the pattern d i f f e r e d between study s i t e s . At Haines, dai l y productivity during the summer in Zone II (2.77-4.08 g C m"2 day" 1) was 2.1-3.6 times that of Zone I F^ di st ichus (1.13-1.31 g C m"2 day" 1). In contrast, fall/winter rates in Zone I plants (0.44-2.75 g C m"2 day" 1) were 1.1-4.2 times that of Zone II plants (0.44-2.75 g C irr 2 day" 1; Table 34). At Helby and Wizard, d a i l y productivity in Zone II was a l w a y s g r e a t e r t h a n t h a t i n Zone I ( T a b l e s 35 and 3 6 ) . D a i l y p r o d u c t i v i y of F\ d i s t i c h u s i n Zone I I I a t H e l b y and W i z a r d was a l s o g r e a t e r t h a n i n Zone I d u r i n g t h e summer, but n o t d u r i n g t h e f a l l and w i n t e r . P/B r a t i o s and net d a i l y p r o d u c t i v i t y was g r e a t e s t i n t h e s p r i n g and e a r l y summer f o r H_j_ s e s s i l e ( T a b l e 3 7 ) . E x c e p t f o r f e n e s t r a t a , w h i c h showed maximum P/B r a t i o s d u r i n g t h e summer, t h e r e was l i t t l e s e a s o n a l v a r i a t i o n i n th e P/B r a t i o s of t h e o t h e r s p e c i e s s t u d i e d . However, net d a i l y p r o d u c t i v i t y was g e n e r a l l y g r e a t e s t d u r i n g t h e summer f o r a l l t h e s e s p e c i e s . D a i l y p r o d u c t i v i t y of C. v a n c o u v e r i e n s i s was r e l a t i v e l y c o n s t a n t t h r o u g h o u t t h e y e a r . P r o d u c t i v i t y of C l a d o p h o r a s p p . i n H e l b y / Z o n e I I I ( T a b l e 35) and l a r i x i n W i z a r d / Z o n e I I I ( T a b l e 36) were g r e a t e s t d u r i n g A u g u st t o Novemember 1982. The m a g n i t u d e of t h e LOS te r m ( l o s s e s of f i x e d c a r b o n due t o h e r b i v o r y , wave e r o s i o n o f t i s s u e s , e t c . ) , a l s o showed s e a s o n a l p a t t e r n s . E x c e p t d u r i n g t h e s p r i n g , LOS e x c e e d e d n e t p r o d u c t i v i t y ; t h u s , a l t h o u g h t h e m a c r o a l g a e were a c t i v e l y f i x i n g c a r b o n , e x t e r n a l f a c t o r s (wave a c t i o n p r o b a b l y b e i n g t h e most i m p o r t a n t ) r e d u c e d a l g a l s t a n d i n g c r o p s . T h i s i s v e r y o b v i o u s when c o m p a r i n g n e t a n n u a l p r o d u c t i v i t y and t o t a l a n n u a l l o s s e s , and r e f l e c t s t h e d e c r e a s e d s t a n d i n g c r o p s o b s e r v e d i n spring/summer 1983 vs t h o s e i n summer 1982. Most s p e c i e s showed a -LOS v a l u e i n th e e a r l y s p r i n g (march t o A p r i l ) i n t e r v a l . In F\ d i s t i c h u s t h e month i n w h i c h a s p r i n g -LOS v a l u e was c a l c u l a t e d v a r i e d w i t h t h e s i t e and zone. N e g a t i v e LOS v a l u e s were o b s e r v e d i n Zone I d u r i n g t h e J a n u a r y - M a r c h i n t e r v a l a t H a i n e s and H e l b y (a -LOS r a t e was a l s o n o t e d i n H e l b y / Z o n e I i n M a r c h - A p r i l ) ; i n W i z a r d / Z o n e I , t h e -LOS v a l u e was o b s e r v e d i n t h e M a r c h - A p r i l i n t e r v a l . A n e g a t i v e LOS r a t e was c a l c u l a t e d i n Zone I I a t a l l t h r e e s h e l t e r e d s i t e s i n M a r c h - A p r i l . LOS was a l w a y s p o s i t i v e i n Zone I a t N u d i b r a n c h and i n Zone I I I a t H e l b y and W i z a r d , but -LOS r a t e s were o b s e r v e d i n H a i n e s / Z o n e I I I . Because of t h e l a r g e number of e n v i r o n m e n t a l f a c t o r s w h i c h may i n f l u e n c e a l g a l p r o d u c t i v i t y , and t h e l a c k o f w i n t e r and e a r l y s p r i n g d a t a f o r most o f t h e s p e c i e s s t u d i e d , a m u l t i p l e r e g r e s s i o n a n a l y s i s of d a i l y p r o d u c t i v i t y p e r m2 of i n t e r t i d a l s u b s t r a t e on s e l e c t e d a b i o t i c e n v i r o n m e n t a l f a c t o r s was p e r f o r m e d o n l y w i t h F u c u s  d i s t i c h u s . The f o l l o w i n g s i g n i f i c a n t r e g r e s s i o n e q u a t i o n (F=10.506 2 , 8 l d f ; p=0.0001) f o r t h e p r o d u c t i v i t y o f F. d i s t i c h u s (g C m"2 d a y " 1 ) , o v e r a l l s i t e s and z o n e s , was o b t a i n e d : NET DAILY PROD = 0.095(H2O-T) - 0.22(WAVE EXP) + 0.83 MULTIPLE-R = 0.45384 SE = 0.99657 246 Note t h a t t h e M u l t i p l e - R and p a r t i a l c o r r e l a t i o n c o e f f i c i e n t s f o r water t e m p e r a t u r e (r=0.23338) and wave e x p o s u r e (r=-0.39560) a r e q u i t e low. Thus, t h e r e g r e s s i o n e q u a t i o n a c c o u n t s f o r o n l y 20.6% of t h e o b s e r v e d v a r i a b i l i t y i n d a i l y p r o d u c t i v i t y of d i s t i c h u s . D i s c u s s i o n The o b s e r v e d p a t t e r n of p h o t o s y n t h e t i c r a t e s i s c o m p a t i b l e w i t h t h e " m o r p h o l o g i c a l f o r m - f u n c t i o n " h y p o t h e s i s of L i t t l e r ( 1 9 8 0 ) . P h o t o s y n t h e t i c r a t e s were g r e a t e s t i n t h e t h i n s h e e t U l v a f e n e s t r a t a (1.45-6.26 mg C g d r y wt" 1 h" 1 ) and t h e f i l a m e n t o u s C l a d o p h o r a s p p . (0.97-4.53 mg C g d r y wt" 1 h " 1 ) . I n t e r m e d i a t e r a t e s were o b s e r v e d i n t h e p e r e n n i a l and t h i c k - b l a d e d F u c u s d i s t i c h u s ( F i g u r e s 18-19) and H e d o p h y l l u m s e s s i l e ( F i g u r e 20a,b) and i n t h e c o a r s e l y b r a n c h e d Neorhodomela l a r i x (0.54-2.20 mg C g d r y wt" 1 h " 1 ) . P h o t o s y n t h e t i c r a t e s were l o w e s t i n t h e a r t i c u l a t e d c o r a l l i n e a l g a e C o r a l l i n a V a n c o u v e r i e n s i s (0.26-0.86 mg C g d r y wt" 1 h " 1 ) and i n H a l o s a c c i o n americanum (0.25-0.86 mg C g d r y wt" 1 h " 1 ) . However, i t s h o u l d be n o t e d t h a t d i u r n a l and s e a s o n a l c h a n g e s i n p h o t o s y n t h e t i c r a t e s c a n b l u r any d i s t i n c t i o n s b a s e d on t h a l l u s f o r m . P h o t o s y n t h e t i c r a t e s were a l s o more v a r i a b l e i n t h o s e s p e c i e s w i t h h i g h e r r a t e s . A l t h o u g h t h i s 247 may have been due to c o m p l i c a t i o n s in measuring e l e v a t e d oxygen c o n c e n t r a t i o n s , i t a l s o demonstrates the l i m i t a t i o n s of c l a s s i f y i n g algae i n t o broad groups based on p h o t o s y n t h e t i c r a t e s . In a d d i t i o n , very low p h o t o s y n t h e t i c r a t e s were observed i n amer icanum . T h i s a l g a has a parenchymatous and saccate t h a l l u s , and a c c o r d i n g to L i t t l e r (1980) would have been expected to have much higher r a t e s of p h o t o s y n t h e s i s . Although seasonal d i f f e r e n c e s i n r e s p i r a t i o n r a t e s a p p a r e n t l y o c c u r r e d i n some s p e c i e s ( F^ d i st ichus , C. v a n c o u v e r i e n s i s ), the-changes were not g r e a t . Newell and Pye (1968) concluded that r e s p i r a t i o n r a t e s in seven macroalgae ( i n c l u d i n g Ulva l a c t u c a and Fucus sp.) were r e l a t i v e l y u n a f f e c t e d by temperature f l u c t u a t i o n s w i t h i n the normal range of temperatures to which the p l a n t s are exposed. The observed r a t e s of p h o t o s y n t h e s i s f o r F^ d i s t i c h u s are comparable with those found by p r e v i o u s workers. Johnson et a l . (1974) r e p o r t e d a value of 0.9 ± 0.13 mg C g dry wt- 1 h" 1 f o r F\ d i s t i c h u s and ' Quadir et a l . (1979) found r a t e s of 0.61 and 1.23 mg C g dry wt" 1 h" 1 at 10 and 18°C, r e s p e c t i v e l y , f o r t h i s p l a n t . P h o t o s y n t h e t i c r a t e s ranging between 0.8 and 2.5 mg C g dry wt" 1 h" 1 have been repor t e d f o r a number of f u c o i d s (King and Schramm, 1976b; B r i n k h u i s , 1977b). Lower r a t e s were noted i n F^ d i s t i c h u s from C a l i f o r n i a (0.40 mg C g dry wt" 1 h " 1 ; L i t t l e r , 1980) 248 and for Fucus serratus L., E\_ s p i r a l i s , and P e l v e t i a  c a n a l i c u l a t a i n Scotland (0.20-0.35 mg C g dry w t - 1 h" 1, converted from the author's o r i g i n a l u n i t s ; Schonbeck and Norton, 1980). King and Schramm (1976a) observed maximum photosynthetic rates of 0.45-3.48 mg C g dry wt" 1 h" 1 (converted) i n F\ v e s i c u l o s u s . In f u c o i d s , photosynthetic rates were greatest i n the a p i c a l p o r t i o n s of the blades and decreased towards the base of the plant (King and Schramm, 1976a; B r i n k h u i s , 1977a,b). Care was taken in t h i s study to use plant m a t e r i a l comprised of both blade and s t i p e p o r t i o n s , so the observed photosynthetic rates were rep r e s e n t a t i v e of whole p l a n t s . Seasonal changes i n photosynthetic rates were g e n e r a l l y small and not c l e a r l y d i s t i n g u i s h e d by S-N-K a n a l y s i s (p<0.0l). Nudibranch F^ d i st ichus apparently had greatest rates i n the summer, but data are l a c k i n g for the winter and e a r l y s p r i n g . Previous s t u d i e s with fucoids have g e n e r a l l y found large seasonal d i f f e r e n c e s in photosynthetic r a t e s . Quadir et a l . (1979) reported higher photosynthetic rates i n F\ d i s t ichus during J u l y at 18°C than in January at 10°C. Maximum rates i n Ascophyllum nodosum, ecad s c o r p i o i d e s ( B r i n k h u i s , 1 977a) and v e s i c u l o s u s ( B r i n k h u i s , 1977b) were observed i n the spring and summer, with lower rates i n the f a l l and winter. In c o n t r a s t , photosynthesis in F. s e r r a t u s was greatest i n the winter and lowest i n the spring (King and Schramm, 1976b). Fucus v e s i c u l o s u s from 249 t h e B a l t i c showed r e l a t i v e l y c o n s t a n t r a t e s d u r i n g t h e f a l l , w i n t e r and s p r i n g ( K i n g and Schramm, 1976b). F u c o i d s t h u s a p p e a r t o show a wide v a r i e t y o f r e s p o n s e s t o c h a n g i n g e n v i r o n m e n t a l c o n d i t i o n s , w i t h i n t h e same s p e c i e s as w e l l as between d i f f e r e n t s p e c i e s i n t h e same g e o g r a p h i c a l a r e a . T h i s m ight r e s u l t i n d i f f e r e n t s e a s o n a l p a t t e r n s of p r o d u c t i v i t y ( s e e a l s o B r i n k h u i s , 1 9 7 7 a , b , c ) . S e a s o n a l d i f f e r e n c e s i n n e t d a i l y p h o t o s y n t h e s i s by F. d i s t i c h u s were more a p p a r e n t t h a n t h e c h a n g e s i n h o u r l y p h o t o s y n t h e t i c r a t e s . Thus, t h e s e a s o n a l v a r i a t i o n i n net d a i l y p h o t o s y n t h e s i s was p r o b a b l y due t o s e a s o n a l d i f f e r e n c e s i n d a y l e n g t h . N i t r a t e l i m i t a t i o n d u r i n g J u l y and A u g u s t may have c o n t r i b u t e d t o t h e l o w e r net p h o t o s y n t h e s i s r a t e s o b s e r v e d d u r i n g t h i s t i m e . In t h e H e l b y p l a n t s , water t e m p e r a t u r e was t h e o n l y s i g n i f i c a n t f a c t o r i n t h e m u l t i p l e r e g r e s s i o n a n a l y s i s of n e t d a i l y p h o t o s y n t h e s i s on s e l e c t e d a b i o t i c e n v i r o n m e n t a l f a c t o r s ( T a b l e 2 9 ) . S e a s o n a l c h a n g e s i n w ater t e m p e r a t u r e may have been more s t r o n g l y i n f l u e n c e d by d a y l e n g t h t h a n a b s o l u t e p h o t o n f l u x d e n s i t y ; t h e r e g r e s s i o n e q u a t i o n s may t h e r e f o r e i n d i r e c t l y (and a c c u r a t e l y ? ) a c c o u n t f o r t h e i n f l u e n c e of d a y l e n g t h on d a i l y n e t p h o t o s y n t h e s i s i n t h e s h e l t e r e d F. d i s t i c h u s . The v a r i o u s p h o t o s y n t h e s i s p a r a m e t e r s f o r t h e H e l b y p l a n t s - d a i l y and d i u r n a l P/R r a t i o s , PSE - g e n e r a l l y showed r e s p o n s e s i n d i c a t i v e of b i o c h e m i c a l a d j u s t m e n t s t o m i n i m i z e t h e e f f e c t s o f s e a s o n a l c h a n g es i n t h e e n v i r o n m e n t on p h o t o s y n t h e s i s r a t e s . The P/R r a t i o s were g e n e r a l l y l o w e r i n t h e summer and had s i g n i f i c a n t p o s i t i v e c o r r e l a t i o n s w i t h s e a w a t e r n i t r a t e c o n c e n t r a t i o n and n e g a t i v e c o r r e l a t i o n s w i t h a i r t e m p e r a t u r e . P h o t o s y n t h e t i c e f f i c i e n c y (PSE) i n c r e a s e d d u r i n g t h e w i n t e r ; s i g n i f i c a n t p o s i t i v e c o r r e l a t i o n s were o b s e r v e d w i t h r a i n f a l l and wave e x p o s u r e and n e g a t i v e c o r r e l a t i o n s w i t h w ater t e m p e r a t u r e , p h o t o n f l u x d e n s i t y , and p e r c e n t t i m e e x p o s e d t o a i r . N e g a t i v e c o r r e l a t i o n s were a l s o o b s e r v e d between PSE and n e t and g r o s s d a i l y p h o t o s y n t h e s i s , i n d i c a t i n g accommodation t o a m b ient s e a s o n a l l i g h t c o n d i t i o n s . R o s e n b e r g and Ramus (1982b) f o u n d i n c r e a s e d pigment l e v e l s d u r i n g t h e w i n t e r i n G r a c i l a r i a f o l i i f e r a ( F o r s k a l l ) B o r g e s o n and U l v a s p . They c o n c l u d e d t h a t t h e e f f e c t of t h e s e s e a s o n a l i n c r e a s e s would be t o l i m i t t h e d e c r e a s e i n i n t e g r a t e d net p h o t o s y n t h e s i s as l i g h t and t e m p e r a t u r e d e c r e a s e d . A l t h o u g h p i g m e n t l e v e l s were not m o n i t o r e d i n t h i s s t u d y , F ^ d i s t i c h u s was d a r k e r i n c o l o r d u r i n g t h e w i n t e r , so a s i m i l a r mechanism may have been o p e r a t i n g i n t h i s s p e c i e s . W i n t e r maxima i n c h l o r o p h y l l and c a r o t e n o i d s were o b s e r v e d i n F u c u s v i r s o i d e s (Don) J . Ag. by Z a v o d n i k ( 1 9 7 3 ) , but p h o t o s y n t h e t i c r a t e s were not c o r r e l a t e d w i t h pigment l e v e l s . The s e a s o n a l p a t t e r n o f p h o t o s y n t h e s i s i n F ^ d i s t i c h u s a t N u d i b r a n c h d i f f e r e d f r o m t h a t i n t h e s h e l t e r e d p l a n t s . The r e g r e s s i o n e q u a t i o n s f o r n e t d a i l y p h o t o s y n t h e s i s i n N u d i b r a n c h F\ d i s t i c h u s were a l s o d i f f e r e n t from t h o s e i n t h e H e l b y p l a n t s : water t e m p e r a t u r e had a n e g a t i v e e f f e c t w h i l e a i r t e m p e r a t u r e and p e r c e n t t i m e e x p o s e d t o a i r had p o s i t i v e e f f e c t s . T h e s e r a t h e r anomalous r e s u l t s , p e r h a p s due t o t h e l a c k of w i n t e r and e a r l y s p r i n g d a t a f o r t h e N u d i b r a n c h p l a n t s , s u g g e s t t h a t t h e r e g r e s s i o n e q u a t i o n does n o t a c c u r a t e l y r e f l e c t t h e f u n c t i o n a l r e l a t i o n s h i p between p h o t o s y n t h e s i s and t h e e n v i r o n m e n t . Z a v o d n i k (1973) a l s o n o t e d b e t w e e n - s i t e d i f f e r e n c e s i n s e a s o n a l p h o t o s y n t h e t i c r a t e s of F u c u s v i r s o i d e s , so t h e phenomena o b s e r v e d i n t h i s s t u d y may be of more g e n e r a l o c c u r r e n c e . A s h - f r e e ( o r g a n i c ) w e i g h t v a r i e d s e a s o n a l l y w i t h n e t d a i l y p h o t o s y n t h e s i s . O r g a n i c c o n t e n t was g r e a t e s t i n s h e l t e r e d F ^ d i s t i c h u s d u r i n g March-May 1983, w h i l e i n F. d i s t i c h u s from N u d i b r a n c h , o r g a n i c w e i g h t was g r e a t e s t i n J u ne and A u g u s t 1982. Z a v o d n i k (1973) a l s o r e p o r t e d s e a s o n a l c o n c o r d a n c e of e l e v a t e d o r g a n i c w e i g h t and maximum p h o t o s y n t h e t i c r a t e s i n F\_ v i r s o i d e s . S e a s o n a l d i f f e r e n c e s were a l s o o b s e r v e d i n n e t d a i l y p r o d u c t i v i t y ( p e r m 2 of i n t e r t i d a l s u b s t r a t e ) a t t h e s t u d y s i t e s . D a i l y p r o d u c t i v i t y was g r e a t e s t d u r i n g t h e spring/summer i n Zones II and I I I o f t h e s h e l t e r e d s i t e s and Zone I a t W i z a r d , but was h i g h e s t i n t h e f a l l / w i n t e r i n Zone I a t H a i n e s and H e l b y . At N u d i b r a n c h , d a i l y p r o d u c t i v i t y was g r e a t e s t i n t h e summer 1982, r e f l e c t i n g t h e d e c r e a s e d F. d i s t i c h u s s t a n d i n g c r o p a t o t h e r t i m e s . P/B r a t i o s showed a s e a s o n a l p a t t e r n s i m i l a r t o t h a t o f d a i l y p r o d u c t i v i t y a t t h e s h e l t e r e d s i t e s , but were r e l a t i v e l y c o n s t a n t a t N u d i b r a n c h . P a r t o f t h e o b s e r v e d d i f f e r e n c e s i n p r o d u c t i v i t y between Zone I and II p l a n t s a t t h e s h e l t e r e d s i t e s was due t o t h e a s s u m p t i o n s of d e s i c c a t i o n s t r e s s i n t h e summer r e d u c i n g t h e c a l c u l a t e d n e t d a i l y p h o t o s y n t h e s i s r a t e s by 50%. However, p h o t o s y n t h e t i c r a t e s i n Zone I p l a n t s were g e n e r a l l y l o w e r t h a n t h o s e i n Zone I I p l a n t s . In a d d i t i o n , t h e l a c k o f a w i n t e r d e c l i n e i n d i s t i c h u s s t a n d i n g c r o p i n Zone I a t H a i n e s ( C h a p t e r 3) and t h e s i m i l a r s e a s o n a l p a t t e r n of d a i l y p r o d u c t i v i t y i n Zones I and II a t W i z a r d , i m p l i c a t e wave a c t i o n as i n f l u e n c i n g t h e o b s e r v e d p a t t e r n . P h o t o s y n t h e s i s i n F\_ d i s t i c h u s i s a p p a r e n t l y g r e a t e s t when t h e p l a n t s a r e e x p o s e d and d e s i c c a t e d c a . 25% ( J o h n s o n e t a l . , 1974; Q u a d i r e t a l . , 1979). P h o t o s y n t h e t i c r a t e s d e c l i n e w i t h i n c r e a s i n g d e s i c c a t i o n above t h i s l e v e l , b ut t h e p l a n t s can m a i n t a i n a h i g h r a t e of p h o t o s y n t h e s i s f o r s e v e r a l h o u r s when e x p o s e d ( J o h n s o n e t a l . , 1974). N u t r i e n t u p t a k e by F\_ d i s t i c h u s a l s o shows accommodations ^to t h e i n c r e a s e d d e s i c c a t i o n s t r e s s and r e d u c e d n u t r i e n t l e v e l s f a c e d by t h e p l a n t s i n t h e summer. Thomas (1983) f o u n d t h a t r a t e s o f n u t r i e n t u p t a k e were e n h a n c e d a f t e r a few weeks of moderate (20-30%) d e s i c c a t i o n and n u t r i e n t l i m i t a t i o n . Schonbeck and N o r t o n (1979) a l s o r e p o r t e d accommodations i n F. s p i r a l i s and P_;_ c a n a l i c u l a t a s u c h t h a t g r o w t h d u r i n g t h e summer was j u s t as good when t h e p l a n t s were submerged one hour of e v e r y t w e l v e h o u r s as when submerged e l e v e n h o u r s p e r e v e r y t w e l v e h o u r s . In a d d i t i o n , upper l e v e l f u c o i d s c a n a p p a r e n t l y r e c o v e r t o maximum submerged p h o t o s y n t h e t i c r a t e s a f t e r a p e r i o d of e x p o s u r e more c o m p l e t e l y t h a n l o w e r l e v e l p l a n t s (Schonbeck and N o r t o n , 1978; D r i n g and Brown, 1982). D e s p i t e a d j u s t m e n t s f u c o i d s may make t o l i m i t t h e e f f e c t s of d e s i c c a t i o n s t r e s s and n u t r i e n t l i m i t a t i o n on p r o d u c t i v i t y , i t would a p p e a r t h a t Zone I F ^ d i s t i c h u s s t i l l i s e f f e c t e d a d v e r s e l y by t h e s e s t r e s s e s . Where i n c r e a s e d wave a c t i o n may r e d u c e t h e s e s t r e s s e s , a s i n Zone I a t W i z a r d , t h e s e a s o n a l p a t t e r n of d a i l y p r o d u c t i v i t y i s s i m i l a r t o t h a t of lo w e r s h o r e p l a n t s ( a l t h o u g h p r o d u c t i v i t y i s s t i l l r e d u c e d ) . Where wave a c t i o n i s even g r e a t e r s t i l l , a s a t N u d i b r a n c h , p h o t o s y n t h e s i s and p r o d u c t i v i t y a r e much r e d u c e d and show a d i f f e r e n t s e a s o n a l p a t t e r n t h a n a t t h e s h e l t e r e d s i t e s . S t a n d i n g c r o p s a r e l i m i t e d by t h e g r e a t e r wave a c t i o n and t h e p l a n t s a l s o p r o b a b l y show d i f f e r e n c e s i n t h a l l u s s t r u c t u r e ( see Thorn, 1983) and b i o c h e m i c a l c h a n g e s i n t h e p h o t o s y n t h e t i c a s s i m i l a t o r y mechanisms i n r e s p o n s e t o i n c r e a s e d wave a c t i o n . The o b s e r v e d d a i l y p r o d u c t i v i t y r a t e s a r e g r e a t e r t h a n t h o s e r e p o r t e d by B r i n k h u i s (1977c) f o r A_^_ nodosum e c a d s c o r p i o i d e s (0.6-1.4 g C i r r 2 d a y - 1 ) and F ^ v e s i c u l o s u s (0.24-0.75 g C n r 2 d a y 1 ) and by N e i l l (1977) f o r F. s p i r a l i s (0.50 g C r r r 2 day " 1 ) and c a n a l i c u l a t a (0.67 g C r r r 2 d a y - 1 ) . The d i f f e r e n c e s a r e a l m o s t c e r t a i n l y due t o d i f f e r e n c e s i n s t a n d i n g c r o p l e v e l s , as p h o t o s y n t h e t i c r a t e s were c o m p a r a b l e i n t h i s s t u d y and t h a t of B r i n k h u i s ( 1 9 7 7 c ) . N e i l l ' s (1977) d a t a , however, were b a s e d on b i o m a s s c h a n g e s , w h i c h may have u n d e r e s t i m a t e d p r o d u c t i v i t y by up t o 50% ( s e e B r i n k h u i s , 1 9 7 7 c ) . Z a v o d n i k (1973) e s t i m a t e d d a i l y p r o d u c t i v i t y o f F\_ v i r s o i d e s t o be 4.02 g C m"2 d a y " 1 , b a s e d on a s t a n d i n g c r o p o f 675 g d r y wt r r r 2 . B o t h t h e s t a n d i n g c r o p and d a i l y p r o d u c t i v i t y v a l u e s a r e s i m i l a r t o t h o s e f o u n d i n t h e s h e l t e r e d Zone II F. d i s t i c h u s p o p u l a t i o n s . S e a s o n a l d i f f e r e n c e s were a l s o o b s e r v e d i n t h e magni t u d e of t h e LOS t e r m ( l o s s e s due t o h e r b i v o r y , wave e r o s i o n of t i s s u e s , e t c . ) . N e g a t i v e LOS v a l u e s , i n d i c a t i n g t h a t t h e measured p h o t o s y n t h e t i c r a t e s were n o t h i g h enough t o a c c o u n t f o r t h e o b s e r v e d i n c r e a s e s i n F\ d i s t i c h u s s t a n d i n g c r o p , were n o t e d i n t h e e a r l y s p r i n g 1983 and o c c a s i o n a l l y i n t h e summer 1982. The t i m i n g of t h e s p r i n g -LOS r a t e a l s o v a r i e d between s i t e s : J a n u a r y - M a r c h i n Zone I p l a n t s a t H a i n e s and H e l b y , and M a r c h - A p r i l i n Zone II F. d i s t i c h u s and W i z a r d / Z o n e I p l a n t s . A n e g a t i v e LOS te r m was n e v e r o b s e r v e d i n t h e N u d i b r a n c h Zone I F\_ d i s t i c h u s p o p u l a t i o n . Most o f t h e l o s s e s were t h e r e s u l t of d e c r e a s e s i n s t a n d i n g c r o p ; t h e r e m a i n d e r c a n n o t be c o m p l e t e l y a t t r i b u t e d t o DOM e x c r e t i o n , d e s p i t e t h e h y p o t h e s i z e d m i n i m a l e f f e c t s of h e r b i v o r y ( s e e C h a p t e r 4) , a s f i x e d c a r b o n may a l s o have been s t o r e d d u r i n g t h e summer when ambient n i t r a t e c o n c e n t r a t i o n s were low. In a d d i t i o n , some of t h e LOS t e r m may have gone i n t o r e p r o d u c t i o n . The l a r g e s t a n d i n g c r o p i n c r e a s e s i n t h e s p r i n g were p r o b a b l y t h e r e s u l t of t h e g r o w t h of s m a l l g e r m l i n g s w h i c h have h i g h e r p h o t o s y n t h e t i c r a t e s t h a n more mature p l a n t s and a r e a d a p t e d t o grow under l o w e r l i g h t c o n d i t i o n s ( F a i n and M u r r a y , 1982; Thorn, 1983). A l s o , i f pigment and enzyme l e v e l s were e l e v a t e d d u r i n g t h e f a l l and w i n t e r ( i n r e s p o n s e t o r e d u c e d l i g h t and t e m p e r a t u r e and i n c r e a s e d a m bient n i t r a t e c o n c e n t r a t i o n s ) , t h e s e o r g a n i c m o l e c u l e s may have been m e t a b o l i z e d and u s e d f o r g r o w t h i n t h e e a r l y s p r i n g when l i g h t and t e m p e r a t u r e i n c r e a s e d and n i t r a t e c o n c e n t r a t i o n s d e c r e a s e d . T h i s may have c o n t r i b u t e d t o t h e c a l c u l a t e d -LOS v a l u e s o b s e r v e d i n t h e e a r l y s p r i n g . I c a n o f f e r no h y p o t h e s i s t o e x p l a i n t h e o b s e r v e d d i f f e r e n c e s i n t h e t i m i n g o f t h e -LOS v a l u e i n t h e s p r i n g between t h e Zone I and Zone I I p o p u l a t i o n s . The r e s u l t s o f t h e p h o t o s y n t h e s i s s t u d i e s and c a l c u l a t i o n s of p r o d u c t i v i t y s u g g e s t t h a t F_;_ d i s t i c h u s i s c a p a b l e of making maj o r a d j u s t m e n t s t o s e a s o n a l c h a n g e s i n l i g h t and t e m p e r a t u r e . P o s i t i v e n e t p h o t o s y n t h e s i s and p r o d u c t i v i t y were o b s e r v e d d u r i n g a l l months; i t t h u s a p p e a r s t h a t p r o d u c t i v i t y d u r i n g t h e f a l l and w i n t e r were l i m i t e d by i n c r e a s e d wave a c t i o n r e m o v i n g f \ d i s t i c h u s f r o m t h e i n t e r t i d a l , and by low n u t r i e n t c o n c e n t r a t i o n s and d e s i c c a t i o n s t r e s s i n t h e summer. Wave a c t i o n may r e d u c e d e s i c c a t i o n and n u t r i e n t s t r e s s e s d u r i n g t h e summer. Th e s e c o n c l u s i o n s a r e s u p p o r t e d by t h e r e s u l t s o f Thorn ( 1 9 8 3 ) , who o b s e r v e d t h a t mean g r o w t h o f t a g g e d d i s t i c h u s i n Puget Sound was g r e a t e r i n O c t o b e r - F e b r u a r y t h a n i n M a r c h - J u l y . F u c u s d i s t i c h u s p h o t o s y n t h e t i c r a t e s a r e not l i m i t e d by l i g h t or t e m p e r a t u r e i n w i n t e r and t h u s , under h i g h ambient s e a w a t e r n i t r a t e c o n c e n t r a t i o n s , i n d i v i d u a l p l a n t s may grow a t maximal r a t e s . Wave a c t i o n , however, l i m i t s t h e p o p u l a t i o n s t a n d i n g c r o p and p r o d u c t i v i t y . To my knowledge, t h e r e a r e no p r e v i o u s d a t a on r a t e s of p h o t o s y n t h e s i s i n H e d o p h y l l u m s e s s i l e . However, p h o t o s y n t h e t i c r a t e s i n L a m i n a r i a d i g i t a t a (Huds.) Lamour. (0.5-1.50 mg C g d r y wt" 1 h ~ 1 , c o n v e r t e d ; K i n g and Schramm, I9 7 6 a b ) , M a c r o c y s t i s p y r i f e r a ( L . ) C. Ag. (1.58 ± 0.37 mg C g d r y wt" 1 h " 1 , c o n v e r t e d ; Towle and P e a r s e , 1973), E g r e g i a  l a e v i g a t a S e t c h e l l (1.4 mg C g d r y wt" 1 h " 1 ; L i t t l e r and Mu r r a y , 1974), and E ^ m e n z i e s i i (0.7-2.8 mg C g d r y wt" 1 h " 1 ; L i t t l e r , 1980; L i t t l e r and A r n o l d , 1980), a r e s i m i l a r t o t h o s e f o u n d f o r s e s s i l e i n t h i s s t u d y . P h o t o s y n t h e t i c r a t e s and n e t d a i l y p h o t o s y n t h e s i s i n H. s e s s i l e showed a s t r o n g s e a s o n a l p a t t e r n , w i t h maximal r a t e s i n A p r i l t o June ( T a b l e 3 0 ) . R e s p i r a t i o n d i d not v a r y s e a s o n a l l y and none of t h e d a i l y p h o t o s y n t h e s i s p a r a m e t e r s were s i g n i f i c a n t l y c o r r e l a t e d w i t h any o f t h e a b i o t i c e n v i r o n m e n t a l f a c t o r s m o n i t o r e d . The r e s u l t s o f t h e m u l t i p l e r e g r e s s i o n a n a l y s i s ( T a b l e 3 1 ) , t h o u g h h i g h l y s i g n i f i c a n t , a s w i t h t h e N u d i b r a n c h d i s t i c h u s a r e d i f f i c u l t t o e x p l a i n due t o t h e l a c k of w i n t e r d a t a . D a i l y p r o d u c t i v i t y i n s e s s i l e , b a s e d on p h o t o s y n t h e s i s measurements and e s t i m a t e s of s t a n d i n g c r o p , were g r e a t e s t i n s p r i n g and summer ( T a b l e 3 7 ) . However, p r o d u c t i v i t y b a s e d on measurements o f b l a d e e l o n g a t i o n was g r e a t e s t i n l a t e summer ( o r , i f t h e r e were e r r o r s i n t h e c a l c u l a t i o n s - see R e s u l t s - t h e y were c o n s t a n t t h r o u g h o u t t h e s t u d y p e r i o d ) and o r g a n i c c o n t e n t of s e s s i l e d i d not v a r y s i g n i f i c a n t l y between months. D e s p i t e t h e s e c o n f l i c t i n g o b s e r v a t i o n s , p r o d u c t i v i t y c a l c u l a t e d by t h e two methods was s i m i l a r ( c a . 190 g C i r r 2 y e a r " 1 ) . F u r t h e r e x p e r i m e n t s a r e needed t o p r o p e r l y e v a l u a t e t h e o b s e r v e d p r o d u c t i v i t y and p h o t o s y n t h e s i s p a t t e r n s i n H^ s e s s i l e . Comp a r a b l e p h o t o s y n t h e t i c d a t a from t h e l i t e r a t u r e a r e not a v a i l a b l e f o r H a l o s a c c i o n americanum , Neorhodomela  l a r i x , C r y p t o s i p h o n i a woodi i , and L e a t h e s i a d i f f o r m i s . Chapman and Goudey (1983) r e p o r t e d d a i l y p r o d u c t i v i t y r a t e s o f 0.017g C m" 1 d a y " 1 f o r d i f f o r m i s i n Nova S c o t i a . C o n s i d e r i n g t h e d i f f e r e n c e s i n s t a n d i n g c r o p s between t h e B a m f i e l d s i t e s and Nova S c o t i a , t h e r a t e s f o u n d i n t h e two s t u d i e s a r e c o m p a r a b l e . W h i l e s e a s o n a l d i f f e r e n c e s were o b s e r v e d i n t h e o r g a n i c c o n t e n t o f H^ amer icanum , p h o t o s y n t h e s i s was c o n s t a n t f o r a l l t h e d a y s on w h i c h e x p e r i m e n t s were p e r f o r m e d . As o r g a n i c c o n t e n t was g r e a t e s t i n August-November and l o w e s t i n A p r i l - J u n e , H_;_ amer icanum may have been s t o r i n g c a r b o n / n i t r o g e n compounds f o r l a t e r g r o w t h i n t h e e a r l y s p r i n g . Net d a i l y p r o d u c t i v i t y was a l s o g r e a t e s t i n A u g u st t o November and a -LOS v a l u e was o b s e r v e d i n t h e e a r l y s p r i n g (Zone I I I / H a i n e s , T a b l e 34; Zone 1 1 1 / N u d i b r a n c h , T a b l e 3 7 ) , w h i c h l e n d some s u p p o r t t o t h i s h y p o t h e s i s . S e a s o n a l c h a n g e s were o b s e r v e d i n p h o t o s y n t h e s i s r a t e s i n N^ l a r i x , but t h e y were not g r e a t . D a i l y p r o d u c t i v i t y i n N u d i b r a n c h / Z o n e II ( T a b l e 37) was g r e a t e s t d u r i n g J u n e -September 1982 and J u n e - A u g u s t 1983, s u g g e s t i n g a s t r o n g s e a s o n a l p a t t e r n (but d a t a a r e l a c k i n g f o r w i n t e r ) . I n c r e a s e d wave a c t i o n d u r i n g t h e w i n t e r a p p a r e n t l y removed much of t h e N_^  l a r i x b i o m a s s from N u d i b r a n c h ; t h u s wave a c t i o n may have l i m i t e d N_;_ l a r i x p r o d u c t i v i t y d u r i n g t h e w i n t e r . However, t h e p h o t o s y n t h e s i s d a t a needed t o v e r i f y t h i s h y p o t h e s i s i s not a v a i l a b l e . P h o t o s y n t h e t i c r a t e s i n C o r a l 1 i n a v a n c o u v e r i e n s i s v a r c h i l e n s i s ( D e c a i s n e ) K u t z . r a n g e between 0.4 and 3.6 mg C g a s h - f r e e wt" 1 h" 1 ( L i t t l e r and M u r r a y , 1974; L i t t l e r , 1980; L i t t l e r and A r n o l d , 1-980); t h e s e v a l u e s a r e s i m i l a r t o t h o s e r e p o r t e d h e r e f o r v a n c o u v e r i e n s i s ( i f e x p r e s s e d i n terms of a s h - f r e e weight).. L i t t l e r and A r n o l d (1980) r e p o r t e d h i g h e r p h o t o s y n t h e t i c r a t e s d u r i n g O c t o b e r and December (3.0-3.6 mg C g a s h - f r e e wt' 1 h " 1 ) compared w i t h March and June (0.4-1.4 mg C g a s h - f r e e wt" 1 h" 1 ) i n o f f i c i n a l i s . S e a s o n a l d a t a c o u l d not be c o l l e c t e d f o r C o r a l l i n a  V a n c o u v e r i e n s i s , but p h o t o s y n t h e s i s was r e l a t i v e l y c o n s t a n t between A p r i l and September ( F i g u r e 2 2 ) . D a i l y p r o d u c t i v i t y i n C_^  Vancouver i e n s i s was g r e a t e s t i n September-November i n N u d i b r a n c h / Z o n e II and H a i n e s / Z o n e I I I , and d u r i n g i n A u g u s t - S e p t e m b e r i n N u d i b r a n c h Zone I I I . As d i s c u s s e d i n C h a p t e r 3, C_^  Vancouver i e n s i s s t a n d i n g c r o p s were a p p a r e n t l y r e d u c e d d u r i n g t h e summer due t o extreme d e s i c c a t i o n s t r e s s ; t h e n e t d a i l y p r o d u c t i v i t y c a l c u l a t i o n s a l s o show t h e e f f e c t s of t h e summer " d i e - b a c k " . The c a l c u l a t e d d a i l y p r o d u c t i v i t y i n C_^  Vancouver i e n s i s (0.02-0.14 g C n r 2 d a y " 1 ) were c o m p a r a b l e w i t h t h o s e f o u n d f o r C. o f f i c i n a l i s i n C a l i f o r n i a by L i t t l e r and M u r r a y (1974) and L i t t l e r and A r n o l d (1980; 0.07-0.20 g C n r 2 d a y " 1 ) . Many w o r k e r s have q u a n t i f i e d p h o t o s y n t h e t i c r a t e s i n v a r i o u s s p e c i e s of U l v a ; t h e r e p o r t e d v a l u e s r a n g e between 1.4 and 9.2 mg C g d r y wt" 1 h " 1 ( L i t t l e r and M u r r a y , 1974; B r i n k h u i s , 1977b; B u e s a , 1975; A r n o l d and M u r r a y , 1980; L i t t l e r j 1980). Q u a d i r e t a l . (1979) o b s e r v e d p h o t o s y n t h e t i c r a t e s of 2.46.± 0.41 mg C g d r y wt" 1 h " 1 and 6.17 ± 0.74 mg C g d r y wt" 1 t r 1 ( c o n v e r t e d ) a t 10 and 18°C, r e s p e c t i v e l y , i n U^ f e n e s t r a t a . T h e s e r a t e s a r e s i m i l a r t o t h o s e o b s e r v e d i n t h i s s t u d y f o r U^ f e n e s t r a t a . B r i n k h u i s (1977b) r e p o r t e d summer maxima and f a l l / w i n t e r minima i n p h o t o s y n t h e s i s by U^ l a c t u c a F a l l / w i n t e r measurements c o u l d n o t be made on f e n e s t r a t a as t h e p l a n t s were r a r e l y f o u n d d u r i n g t h e s e months. D a i l y p r o d u c t i v i t y was g r e a t e s t d u r i n g August-November, b ut s p o r a d i c "blooms" of IL f e n e s t r a t a were o b s e r v e d t h r o u g h o u t t h e summer. O r g a n i c c o n t e n t of IL f e n e s t r a t a was a l s o maximal i n A u g u s t - S e p t e m b e r 1982 ( T a b l e 2 6 ) . R o s e n b e r g and Ramus (1982a) r e p o r t e d t h a t i n t e r m i t t e n t p u l s e s o f n u t r i e n t s d u r i n g t h e summer were e s s e n t i a l t o t h e m a i n t e n a n c e o f h i g h g r o w t h r a t e s i n U l v a s p . S i m i l a r p u l s e s were o b s e r v e d i n t h i s s t u d y ( C h a p t e r 2) and may have been i m p o r t a n t i n f l u e n c e s on U. ' f e n e s t r a t a p r o d u c t i v i t y . In c o n t r a s t t o t h e s e s t u d i e s , Bottom (1981) f o u n d r e d u c e d p h o t o s y n t h e s i s r a t e s d u r i n g J u l y compared w i t h r a t e s i n September-November i n U_;_ l a c t u c a . He a t t r i b u t e d t h e m o n t h l y d i f f e r e n c e s t o th e h a r m f u l e f f e c t s of e l e v a t e d w a t e r t e m p e r a t u r e s d u r i n g J u l y . The o b s e r v e d range of d a i l y p r o d u c t i v i t y r a t e s f o r U. f e n e s t r a t a i n t h i s s t u d y a r e w i t h i n t h e range o f v a l u e s p r e v i o u s l y r e p o r t e d f o r U l v a c a l i f o r n i c a W i l l e ( L i t t l e r , 1973; L i t t l e r and M u r r a y , 1974; L i t t l e r e t a l . , 1979). Buesa (1975) o b s e r v e d p h o t o s y n t h e t i c r a t e s o f 1.85 ± 0.47 mg C g d r y w t - 1 h ~ 1 i n C l a d o p h o r a f u l i g i n o s a K u t z . , w h i l e v a l u e s f o r B a l t i c C l a d o p h o r a g l o m e r a t a ( L . ) K u t z . r a n g e d between 1.5 and 11.4 mg C g d r y w t - 1 h ~ 1 ( K i n g and Schramm, 1976b; W a l l e n t i u s , 1978). T h e s e r a t e s . a r e s i m i l a r t o t h o s e r e p o r t e d h e r e f o r C l a d o p h o r a s pp. L i t t l e r ( 1 9 8 0 ) , however, r e p o r t e d a low r a t e of 0.3 mg C g d r y wt" 1 h " 1 i n C l a d o p h o r a g r a m i n e a C o l l . P h o t o s y n t h e s i s i n C l a d o p h o r a s p p . was r e l a t i v e l y c o n s t a n t between A p r i l and September, w i t h l o w e r r a t e s o b s e r v e d i n O c t o b e r . D a i l y p r o d u c t i v i t y was g r e a t e s t d u r i n g t h e s p r i n g and summer and o r g a n i c c o n t e n t was h i g h e s t i n J u n e - A u g u s t 1982. A s i m i l a r c o r r e l a t i o n between i n c r e a s e d o r g a n i c c o n t e n t and i n c r e a s e d d a i l y p r o d u c t i v i t y i n C l a d o p h o r a s pp. was not o b s e r v e d d u r i n g summer 1983. A summary o f t h e r e s u l t s of some p r e v i o u s s t u d i e s of m a c r o a l g a l p r o d u c t i v i t y , t o g e t h e r w i t h t h e v a l u e s r e p o r t e d h e r e , i s g i v e n i n T a b l e 38. A n n u a l p r o d u c t i v i t y of F. d i s t i c h u s (56-740 g C m"2 y " 1 ) i s w i t h i n t h e range of v a l u e s p r e v i o u s l y r e p o r t e d f o r v a r i o u s F u c a l e s and L a m i n a r i a l e s . The a n n u a l P/B r a t i o s a r e a l s o s i m i l a r t o t h o s e f o u n d p r e v i o u s l y , a l t h o u g h p a s t s t u d i e s w i t h f u c o i d s have not r e p o r t e d a n n u a l P/B r a t i o s as h i g h a s 4.4 o b s e r v e d h e r e f o r F ^ d i s t i c h u s . P/B r a t i o s g e n e r a l l y d e c r e a s e d w i t h i n c r e a s i n g l e v e l s o f d i s t u r b a n c e (wave a c t i o n ) or s t r e s s ( d e s i c c a t i o n , n u t r i e n t s ) . G e r a r d and Mann (1979) f o u n d a P/B r a t i o o f 2.7 i n s h e l t e r e d L a m i n a r i a l o n q i c r u r i s , w h i l e t h e a n n u a l P/B r a t i o i n p l a n t s e x p o s e d t o h i g h e r l e v e l s of water movement was 1.6. They c o n c l u d e d t h a t e x p o s u r e t o h i g h i n t e n s i t y water movement i s more s t r e s s f u l t h a n b e n e f i c i a l t o some b e n t h i c m a r i n e p l a n t s , and a d j u s t m e n t s f o r s u r v i v a l under s u c h c o n d i t i o n s a r e c o s t l y i n terms o f T a b l e 38 Summary of d a i l y and annual net p r o d u c t i v i t y by marine b e n t h i c macroalgae. SPECIES ANNUAL PRODUCTIVITY DAILY PRODUCTIVITY ANNUAL P/B REFERENCE (q C m-2 y-1) (q C m-2 d-1) RATIO PERENNIAL SPECIES Ascophvllum nodusom ecad s c o r p i o i d e s 150 2 . 1 0.6 - 2. - 1 . . 8 . 4 1 .8 Westlake (1963) B r i n k h u i s (1977c) Cod i urn f raq i1e 22 :. 1 Wassman & Ramus ( 1973 C o r a l l i n a o f f i c i n a l i s var ch i1 ens i s 0.07 - 0. . 20 L i t t l e r e t a l . (1979) C o r a l l i n a v a n c o u v e r i e n s i s 2.9-17.3 0.02 - 0. . 14 1.3-1.6 T h i s study E q r e q i a m e n z i e s s i i 0.04 - 0. . 15 L i t t l e r e t a l . ( 1979) Fucus d i s t i c h u s ssp. edenatatus 56-740 964-1752 0.11 - 4. 08 1.5-4.4 2.8 T h i s study Thorn (1983) Fucus sp i ra1 i s 182 . 5 0. 50 1 . 99 N e i l l (1977) Fucus v e s i c u l o s u s 348 150 0. 24 - 0. 75 2 . 3 Guterstam (1981) Br i nkhu i s ( 1977c ) Fucus v i r s o i d e s 4 . 02 Zavodnik (1973) TABLE 38, CONTINUED SPECIES ANNUAL PRODUCTIVITY (q C m-2 V- 1 ) Hedophy11 urn sess i 1 e  H i m a n t h a l i a e l o n g a t a  L a m i n a r i a hyperborea  Lami nar i a 1ong i c r u r i s Lam i nar i a sacchar i na V a r i o u s L a m i n a r i a l e s Macrocyst i s pyr i f e r a 190 989 . 2 640-1320 143-428 288-576 120 1750 54-81 Pel vet i a c a n a l i c u l a t a 244 .6 V a r i o u s s p e c i e s DAILY ANNUAL PRODUCTIVITY P/B (g C m-2 d-1) RATIO 0.51 - 1 . 16 2.4 2.71 12.25 3.9 : • 1.6-2.7 3.8-20.4 6.8 0.67 1.98 1.5 - 21.4 REFERENCE T h i s s t u d y N e i l l (1977) Jupp & Drew (1974) Westlake (1963) Hatcher et a l . ( 1977) Ger a r d & Mann (1979) Johnston et a l . ( 1977) Mann (1972b) Aleem (1956) Towle & Pearse (1973) N e i l l (1977) Johnston et a l . (1969) TABLE 38, CONTINUED  SPECIES ANNUAL/EPHEMERAL SPECIES Chordar i a f1 age 11i form i s  Cladophora spp. Hal o s a c c i on amer icanum  Leathes i a d i f f o r m i s Neorhodomela l a r i x  U1va c a 1 i f o r n i ca U1va f e n s t r a t a ANNUAL PRODUCTIVITY (g C m-2 y- 1 ) 28-229 27.9-72 .4 8.4-10.2 10.3-40.0 30.7-51.9 45.9-109.3 U1va 1actuca V a r i o u s ephemerals 35 DAILY PRODUCTIVITY (g C m-2 d-1 ) 0.17-2.8 0.03-0.80 0.01-0.08 0.017 .008-0.43 0.01-0.44 .002-.013 2.8 0.03-1.30 0.1-1.3 ANNUAL REFERENCE P/B RATIO R i c e and Chapman (1982) 14.0-18.0 T h i s study 1.6 Thi s study Chapman & Goudey (1983) 3.6-5.0 T h i s study 2.3-5.0 T h i s study L i t t l e r e t a l . ( 1979) L i t t l e r (1973) 20.5-26.8 T h i s study B r i n k h u i s (1977c) L a p o i n t e e t a l . (1981) 2 6 5 p r o d u c t i v i t y . A s i m i l a r s i t u a t i o n a p p a r e n t l y a l s o o c c u r s i n F. d i s t i c h u s . I t s h o u l d be s t r e s s e d t h a t t h e c a l c u l a t e d a n n u a l n e t p r o d u c t i v i t y f o r most s p e c i e s was l e s s t h a n t h e t o t a l a n n u a l l o s s e s d u r i n g t h e J une 1982-June 1983 p e r i o d (a n o t a b l e e x c e p t i o n i s s e s s i l e ). T h i s i s t h e r e s u l t of t h e d e c r e a s e d a l g a l s t a n d i n g c r o p s o b s e r v e d d u r i n g t h e summer of 1983. As d i s c u s s e d i n C h a p t e r 3, t h i s may have been due t o t h e e f f e c t s of t h e E l N i n o e v e n t of 1983-1983. Maximum p r o d u c t i v i t y l e v e l s i n t h i s s y s t e m a r e p r o b a b l y a t l e a s t t h o s e o f t h e o b s e r v e d t o t a l a n n u a l LOS term, but t h i s may be c o m p l i c a t e d by c h a n g e s i n p o p u l a t i o n d y n a m i c s and p h o t o s y n t h e t i c r a t e s . A number of w o r k e r s have o b s e r v e d v e r y h i g h l e v e l s of d i s s o l v e d o r g a n i c m a t t e r e x c r e t i o n by some f u c o i d s and k e l p s ( K h a i l o v and B u r l a k o v a , 1969; S i e b u r t h , 1969); however, t h e t e c h n i q u e s u s e d i n t h e s e s t u d i e s may have o v e r e s t i m a t e d DOM e x c r e t i o n . O t h e r w o r k e r s , u s i n g more r i g o r o u s methods, have f o u n d o n l y low r a t e s o f DOM e x c r e t i o n , r a n g i n g between one and f o u r p e r c e n t o f t h e c a r b o n f i x e d i n p h o t o s y n t h e s i s (Majak e t a l . , 1966; H a r l i n and C r a i g i e , 1975; B r y l i n s k y , 1977; P r e g n a l l , 1983). However, H a t c h e r e t a l . (1977) p r o p o s e d t h a t c a . 35% of t h e c a r b o n f i x e d by L_^ l o n q i c r u r i s was e x c r e t e d as DOM. Thus, i n t h e k e l p H_j_ s e s s i l e , where a n n u a l n e t p r o d u c t i v i t y was much h i g h e r t h a n t o t a l a n n u a l l o s s e s ( T a b l e 3 7 ) , a l a r g e f r a c t i o n o f t h e c a r b o n f i x e d i n 2 6 6 p h o t o s y n t h e s i s may have a l s o been e x c r e t e d a s d i s s o l v e d o r g a n i c m a t t e r . In F ^ d i s t i c h u s , p r o d u c t i v i t y was g r e a t e s t d u r i n g t h e summer, but s t a n d i n g c r o p l e v e l s were g e n e r a l l y s t a b l e ( s e e C h a p t e r 3). The c a r b o n f i x e d i n p h o t o s y n t h e s i s and a c c o u n t e d f o r i n t h e LOS te r m c o u l d have been due t o t h e gr o w t h of u n d e r s t o r y Fj_ d i s t c h u s r e p l a c i n g l o s t c anopy p l a n t s . A l s o , i f n i t r a t e c o n c e n t r a t i o n s were l i m i t i n g g r o w t h d u r i n g t h e summer, t h e f i x e d c a r b o n may have been e x c r e t e d as DOM. In a d d i t i o n t o d i r e c t d e t e r m i n a t i o n s of DOM e x c r e t i o n r a t e s , p h y s i o l o g i c a l e x p e r i m e n t s e v a l u a t i n g t h e i n t e r a c t i o n s between p r o t e i n and c a r b o h y d r a t e m e t a b o l i s m , n i t r a t e u p t a k e , and p h o t o s y n t h e s i s , i n r e l a t i o n t o ambient l i g h t , t e m p e r a t u r e and n u t r i e n t c o n d i t i o n s , a r e needed t o e v a l u a t e t h e s e h y p o t h e s e s . V e r y s i g n i f i c a n t , and a p p a r e n t l y e c o l o g i c a l l y m e a n i n g f u l , r e g r e s s i o n e q u a t i o n s were p r o d u c e d w i t h n et d a i l y p h o t o s y n t h e s i s on s e l e c t e d a b i o t i c e n v i r o n m e n t a l f a c t o r s i n F\_ d i s t i c h u s . However, t h e e q u a t i o n s w i t h d a i l y p r o d u c t i v i t y a c c o u n t e d f o r o n l y a s m a l l p o r t i o n o f t h e o b s e r v e d v a r i a b i l i t y i n p r o d u c t i v i t y ; t h i s was o b v i o u s l y due t o t h e e f f e c t s of a l g a l s t a n d i n g c r o p i n t h e p r o d u c t i v i t y c a l c u l a t i o n s and r e g r e s s i o n a n a l y s e s ( see C h a p t e r 3). P h o t o s y n t h e s i s r a t e s can be l i m i t e d by o n l y one f a c t o r a t a tim e - i n t e m p e r a t e a r e a s , u s u a l l y by n u t r i e n t or d e s i c c a t i o n s t r e s s i n t h e summer and l i g h t o r t e m p e r a t u r e i n t h e w i n t e r . However, t h e p l a n t s c a n r a p i d l y a d j u s t t o l i m i t t h e e f f e c t s o f t h e s e s t r e s s f u l c o n d i t i o n s : n u t r i e n t u p t a k e r a t e s ; p h o t o s y n t h e s i s may be e n h a n c e d by d e s i c c a t i o n ; p i g m e n t l e v e l s and enzyme a c t i v i t i e s c a n i n c r e a s e w i t h r e d u c e d l i g h t and t e m p e r a t u r e s . In c o n t r a s t , a d j u s t m e n t s t o d i s t u r b a n c e s s u c h as wave a c t i o n would t a k e much l o n g e r ; i n f r e q u e n t and random s t o r m s would remove much p l a n t biomass f r o m t h e i n t e r t i d a l w h i l e c o n s t a n t h i g h i n t e n s i t y water movements would r e s u l t i n s t r u c t u r a l c h a n g e s i n t h e p l a n t s ( G e r a r d and Mann, 1979). A f t e r t h e r e l a t i v e l y c a l m c o n d i t i o n s of s p r i n g and summer, l a r g e r p l a n t s a r e r e a d i l y t o r n from t h e i n t e r t i d a l by t h e heavy wave a c t i o n d u r i n g f a l l and w i n t e r s t o r m s . In a d d i t i o n , t h e s e a s o n a l p a t t e r n of g r o w t h may be " u n c o u p l e d " from t h e ambient e n v i r o n m e n t a l c o n d i t i o n s . F o r example, some w o r k e r s have o b s e r v e d t e m p o r a l u n c o u p l i n g o f n i t r o g e n u p t a k e and a l g a l growth (Chapman and C r a i g i e , 1977; H a t c h e r e t a l . , 1977; Wheeler and N o r t h , 1980; Gagne e t a l . , 1982; R o s e n b e r g and Ramus, 1982a), so t h a t c o r r e l a t i o n s between p r o d u c t i v i t y and a m b i ent n i t r a t e c o n c e n t r a t i o n s (and o t h e r f a c t o r s ) m ight not be f o u n d . The above o b s e r v a t i o n s a l s o p a r t l y e x p l a i n t h e d i f f e r e n c e s i n t h e e c o l o g i c a l r e l e v a n c e of t h e r e g r e s s i o n e q u a t i o n s . P r o d u c t i v i t y i s t h e r e s u l t o f t h e i n t e r a c t i o n of m e t a b o l i c p r o c e s s e s r e s p o n d i n g t o e n v i r o n m e n t a l s t r e s s e s , and a l g a l s t a n d i n g c r o p , w h i c h i s i n f l u e n c e d by d i s t u r b a n c e s 268 as w e l l as s t r e s s . P h e n o t y p i c a d j u s t m e n t s t o s t r e s s a r e p o s s i b l e , but t h e y p r o d u c e v a r y i n g e f f e c t s on p l a n t g r o w t h and s t a n d i n g c r o p ( s e e G e r a r d and Mann, 1979). The s t o c h a s t i c e f f e c t s o f wave a c t i o n ( a c t i n g as a d i s t u r b a n c e ) a r e d i f f i c u l t t o measure; a l s o , wave a c t i o n may have a p o s i t i v e e f f e c t on p l a n t g r o w t h by a l l e v i a t i n g d e s i c c a t i o n / n u t r i e n t s t r e s s . I t i s t h u s not s u r p r i s i n g t h a t t h e p r o d u c t i v i t y r e g r e s s i o n e q u a t i o n s were n o t as c o m p r e h e n s i v e as t h o s e f o r d a i l y p h o t o s y n t h e s i s . M a r g a l e f (1966) s t a t e d t h a t p r o d u c t i v i t y s h o u l d be u s e d i n r e l a t i o n t o f a c t o r s w h i c h c o n v e y t h e n o t i o n of t i m e ; t h u s p r o d u c t i v i t y i s l i k e l y t o be c o r r e l a t e d i n a more m e a n i n g f u l way w i t h m a g n i t u d e s t h a t a r e d e r i v a t i v e s w i t h r e s p e c t t o t i m e . Such an a n a l y s i s may more a c c u a r a t l y c o r r e l a t e t h e o b s e r v e d r a p i d c h a n g e s i n n u t r i e n t l e v e l s d u r i n g t h e s p r i n g and i n c r e a s e s i n wave a c t i o n d u r i n g t h e f a l l and w i n t e r w i t h c h a n g e s i n a l g a l s t a n d i n g c r o p and p r o d u c t i v i t y . In g e n e r a l , p r o d u c t i v i t y and P/B r a t i o s were i n v e r s e l y r e l a t e d w i t h a l g a l d i v e r s i t y . A t t h e s h e l t e r e d s i t e s , d i v e r s i t y was l o w e s t and p r o d u c t i v i t y h i g h e s t i n t h e upper z o n e s d o m i n a t e d by F\ d i s t i c h u s . D i v e r s i t y was h i g h e r , but p r o d u c t i v i t y l o w e r , i n t h e Zone I I I a s s e m b l a g e s . At N u d i b r a n c h , however, p r o d u c t i v i t y and d i v e r s i t y were g r e a t e s t i n t h e Zone II " a l g a l t u r f " , a l t h o u g h p r o d u c t i v i t y was not much g r e a t e r t h a n t h a t f o u n d i n t h e Zone I I I a s s e m b l a g e d o m i n a t e d by s e s s i l e . 269 L a p o i n t e e t a l . (1981) a l s o n o t e d an i n c r e a s e i n p r o d u c t i v i t y and d e c r e a s e i n d i v e r s i t y a l o n g a " s u c c e s s i o n a l " g r a d i e n t i n a m u s s e l - r a f t a l g a l community i n n o r t h w e s t S p a i n . They a t t r i b u t e d t h e o b s e r v e d p a t t e r n t o t h e l a r g e r s i z e s of t h e p l a n t s i n t h e " c l i m a x " k e l p community compared w i t h t h e lo w e r s t a n d i n g c r o p s of t h e " e a r l y s u c c e s s i o n a l " e p h e m e r a l p l a n t s . When v i e w e d i n l i g h t of t h e r e s u l t s p r e s e n t e d i n C h a p t e r 5 r e g a r d i n g t h o s e f a c t o r s i n f l u e n c i n g a l g a l d i v e r s i t y ( i . e. wave e x p o s u r e and d e s i c c a t i o n s t r e s s ) , t h e a l g a l p r o d u c t i v i t y d a t a would seem t o f u r t h e r s u p p o r t t h e h y p o t h e s i s t h a t wave a c t i o n i s t h e major i n f l u e n c e on i n t e r t i d a l community o r g a n i s a t i o n i n t h e s t u d y a r e a . 270 CONCLUDING REMARKS The main g o a l of t h i s r e s e a r c h was t o a c q u i r e an i n c r e a s e d u n d e r s t a n d i n g o f t h e m a g n i t u d e and r o l e of m a c r o a l g a l p r o d u c t i v i t y i n a r o c k y i n t e r t i d a l s y s t e m . To t h i s end, a l g a l p r o d u c t i v i t y was s t u d i e d on t h r e e d i f f e r e n t , b u t i n t e r a c t i n g , l e v e l s : (1) m a c r o a l g a l s t a n d i n g c r o p s , (2) p h o t o s y n t h e t i c r a t e s , and (3) p r o d u c t i v i t y , c a l c u l a t e d u s i n g t h e s t a n d i n g c r o p and p h o t o s y n t h e s i s d a t a . P r o d u c t i v i t y i s t h e r e s u l t o f t h e i n t e r a c t i o n of p h y s i o l o g i c a l p r o c e s s e s ( p h o t o s y n t h e s i s , n u t r i e n t u p t a k e , p r o t e i n s y n t h e s i s , e t c . ) , e c o l o g i c a l p r o c e s s e s ( h e r b i v o r y , c o m p e t i t i o n , e t c . ) , and e n v i r o n m e n t a l c o n d i t i o n s ( l i g h t , wave a c t i o n , s a l i n i t y , e t c . ) . E s t i m a t i n g a l g a l p r o d u c t i v i t y i s a d i f f i c u l t t a s k , s u b j e c t t o a l a r g e d e g r e e o f e r r o r due t o t h e many p r a c t i c a l and m e t h o d o l o g i c a l p r o b l e m s w h i c h n e c e s s i t a t e t h e use o f s i m p l i f y i n g a s s u m p t i o n s ( c o n s t a n t PQ, c a r b o n c o n t e n t s , e t c . ) and t h e e x t r a p o l a t i o n of s h o r t - t e r m measurements o f p h o t o s y n t h e s i s t a k e n a t some t i m e i n t e r v a l ( e . g. m o n t h l y ) t o l o n g e r p e r i o d s . In a d d i t i o n , measurements o f e n v i r o n m e n t a l f a c t o r s may n o t be r e p r e s e n t a t i v e of t h o s e e x p e r i e n c e d by t h e p l a n t s , i n terms of b o t h m a g n i t u d e and v a r i a b i l i t y . T h e s e p r o b l e m s l i m i t t h e c o n c l u s i o n s w h i c h c a n be drawn r e g a r d i n g t h e r e l a t i o n s h i p s 271 between a l g a l p h y s i o l o g y , e c o l o g y , p r o d u c t i v i t y , and a s e a s o n a l l y f l u c u a t i n g e n v i r o n m e n t . However, as l i v i n g e n t i t i e s , m a c r o a l g a e a r e e x p e c t e d t o show t h e a b i l i t y t o a d j u s t t o c h a n g e s i n e n v i r o n m e n t a l c o n d i t i o n s . Thus, s h o r t - t e r m e n v i r o n m e n t a l f l u c t u a t i o n s of s m a l l m a g n i t u d e would be e x p e c t e d t o have o n l y a l i m i t e d i m pact on t h e a l g a e . Accommodation o f p h y s i o l o g i c a l p r o c e s s e s t o s e a s o n a l c h a n g e s i n t h e e n v i r o n m e n t a r e much more a p p a r e n t . The methods u s e d i n t h i s s t u d y e x amined p h o t o s y n t h e s i s r a t e s , t h e r e l a t i o n s h i p s between p r o d u c t i v i t y , a l g a l s t a n d i n g c r o p , and p h o t o s y n t h e s i s , and s e a s o n a l p a t t e r n s i n t h e s e p a r a m e t e r s i n r e l a t i o n t o a s e a s o n a l l y f l u c t u a t i n g e n v i r o n m e n t . By s t u d y i n g t h e s e i n d i v i d u a l p a t t e r n s , and t h e i r i n t e r a c t i o n s , h y p o t h e s e s were p r o p o s e d t o e x p l a i n t h e t h e o b s e r v e d m a g n i t u d e s and s e a s o n a l p a t t e r n s i n m a c r o a l g a l p r o d u c t i v i t y . The o b s e r v e d s t a n d i n g c r o p s , p h o t o s y n t h e t i c r a t e s , and c a l c u l a t e d p r o d u c t i v i t y v a l u e s were s i m i l a r t o t h e v a l u e s r e p o r t e d p r e v i o u s l y i n t h e l i t e r a t u r e . However, i n t h e c a s e o f p r o d u c t i v i t y , t h e range o f r e p o r t e d v a l u e s i s v e r y l a r g e (100-2000 g C n r 2 y 1 f o r f u c o i d s and k e l p s ) and a l g a l s t a n d i n g c r o p s showed a l a r g e amount o f s p a t i a l h e t e r o g e n e i t y ( s t a n d a r d d e v i a t i o n s were u s u a l l y > 50% o f t h e means). In c o n t r a s t , p h o t o s y n t h e t i c r a t e s w i t h i n a s p e c i e s showed o n l y a m o d e r a t e d e g r e e of v a r i a b i l i t y ( s t a n d a r d 272 d e v i a t i o n s were u s u a l l y < 30% of t h e mean) and were r e l a t i v e l y c o n s t a n t t h r o u g h o u t t h e y e a r . B e c a u s e of t h e d i f f e r e n c e i n t h e ma g n i t u d e of t h e u n i t s o f p h o t o s y n t h e s i s ( mg C g d r y wt" 1 d ~ 1 ) and s t a n d i n g c r o p ( g C i r r 2 d' 1 ) , most of t h e e r r o r i n t h e p r o d u c t i v i t y c a l c u l a t i o n s ( d e s p i t e t h e a s s u m p t i o n s u s e d and c o r r e c t i o n f a c t o r s a p p l i e d ) c an be a t t r i b u t e d t o t h e v a r i a b i l i t y i n a l g a l s t a n d i n g c r o p s . T h u s , t h e r e p o r t e d p r o d u c t i v i t y v a l u e s f o r F u c u s d i s t i c h u s and H e d o p h y l l u m s e s s i l e have an " e r r o r " o f c a . 50-75%. The r e s u l t s of t h e r e g r e s s i o n a n a l y s e s of e n v i r o n m e n t a l f a c t o r s and n e t d a i l y p h o t o s y n t h e s i s , a l g a l s t a n d i n g c r o p s , and p r o d u c t i v i t y , r e f l e c t how p r o d u c t i v i t y may be i n f l u e n c e d by t h e e n v i r o n m e n t . In F\_ d i s t i c h u s , water t e m p e r a t u r e was t h e o n l y s i g n i f i c a n t f a c t o r i n t h e r e g r e s s i o n e q u a t i o n s f o r n e t d a i l y p h o t o s y n t h e s i s , and t h e e q u a t i o n s a c c o u n t e d f o r 70-90% of t h e o b s e r v e d v a r i a n c e i n n e t d a i l y p h o t o s y n t h e s i s . P h o t o s y n t h e t i c r a t e s were r e l a t i v e l y c o n s t a n t d u r i n g t h e y e a r ; t h u s , F ^ d i s t i c h u s a d j u s t e d t o s e a s o n a l c h a n g e s i n l i g h t , t e m p e r a t u r e , n u t r i e n t c o n c e n t r a t i o n s , e t c . , and n e t d a i l y p h o t o s y n t h e s i s was d e t e r m i n e d by d a y l e n g t h . In c o n t r a s t , t h e r e g r e s s i o n e q u a t i o n s f o r s t a n d i n g c r o p and p r o d u c t i v i t y a c c o u n t e d f o r v e r y l i t t l e o f t h e o b s e r v e d s e a s o n a l v a r i a t i o n i n t h e s e p a r a m e t e r s and made l i t t l e " e c o l o g i c a l " s e n s e . T h i s may have been due t o two f a c t o r s : (1) t h e u n c o u p l i n g o f g r o w t h from ambient e n v i r o n m e n t a l c o n d i t i o n s , a n d / o r (2) t h e s t r o n g dependence o f a l g a l 273 s t a n d i n g c r o p s on wave a c t i o n . In a d d i t i o n , w h i l e p h o t o s y n t h e s i s c a n be l i m i t e d by o n l y one f a c t o r a t a t i m e , t h e sum t o t a l o f m e t a b o l i s m ( i . e. n e t p r o d u c t i v i t y ) i s t h e r e s u l t o f t h e i n t e r a c t i o n of many f a c t o r s . The i m p o r t a n c e of p o i n t (1) must be e v a l u a t e d a t t h e p h y s i o l o g i c a l l e v e l . Wave a c t i o n i s a r a t h e r s t o c h a s t i c i n f l u e n c e , i n terms of b o t h m a g n i t u d e and d u r a t i o n ; one s e v e r e s t o r m may have as much impact as t h r e e months of more "moderate" w e a t h e r . P h e n o t y p i c a d j u s t m e n t s and g e n o t y p i c a d a p t a t i o n s t o c h r o n i c l e v e l s of wave e x p o s u r e a r e p o s s i b l e , and a p p a r e n t l y o c c u r r e d i n t h e N u d i b r a n c h d i s t i c h u s , but a r e c o s t l y i n terms of n e t p r o d u c t i v i t y ( s e e a l s o G e r a r d and Mann, 1979). However, accommodation t o i n f r e q u e n t and random i n c r e a s e s i n wave a c t i o n i s p r o b a b l y e n e r g e t i c a l l y i n f e a s i b l e and e v o l u t i o n a r i l y i m p r a c t i c a l . C o n c l u s i v e q u a n t i t a t i v e e v i d e n c e of t h e e f f e c t s of wave a c t i o n on a l g a l p r o d u c t i v i t y , and t h e i n c o r p o r a t i o n of t h i s f a c t o r i n t o a model e x p l a i n i n g o r p r e d i c t i n g p r o d u c t i v i t y , i s t h u s p r o b a b l y not p o s s i b l e . However, t h e r e s u l t s of t h i s s t u d y f o r F\_ d i s t i c h u s s u g g e s t t h a t wave a c t i o n l i m i t s p r o d u c t i v i t y i n t h e f a l l and w i n t e r , w h i l e d e s i c c a t i o n / n u t r i e n t s t r e s s i s l i m i t i n g i n t h e summer. Wave a c t i o n a l s o a p p e a r s t o be t h e major e n v i r o n m e n t a l f a c t o r a f f e c t i n g i n t e r t i d a l community s t r u c t u r e : (1) a l g a l d i s t r i b u t i o n s , a b u n d a n c e s , and p r o d u c t i v i t y v a r i e d a l o n g t h e wave e x p o s u r e g r a d i e n t ; 274 (2) invertebrate d i s t r i b u t i o n s and abundances varied along the wave exposure gradient; (3) desiccation stress in the upper i n t e r t i d a l (Zones I and II) limited the growth of many macroalgal species, but increased wave action appeared to a l l e v i a t e desiccation stress. The observed pattern of alg a l d i v e r s i t y could thus be explained on the basis of the interacting e f f ects of wave action and desiccation stress. Although no experimental manipulations were performed, herbivory apparently has l i t t l e e f fect on macroalgal productivity; as a rough estimate, herbivores probably consume less than 5% of the annual macroalgal productvity of this i n t e r t i d a l system. Substratum heterogeneity, the presence of a F_;_ distichus canopy, and variations in reproduction and recruitment have greater impact on algal productivity. Additional experiments, both physiological and ecological, are needed to more f u l l y understand the productivity of the macroalgae in th i s i n t e r t i d a l system. SUMMARY 275 1) The p r o d u c t i v i t y , d i v e r s i t y and community s t r u c t u r e o f t h e i n t e r t i d a l a l g a l community i n t h e v i c i n i t y of B a m f i e l d , B.C., Canada were s t u d i e d o v e r a f i f t e e n month p e r i o d (June 1982 - A u g u s t 1 9 8 3 ) . F i v e s t u d y s i t e s , r e p r e s e n t a t i v e o f a g r a d i e n t i n wave e x p o s u r e , were ex a m i n e d . The s h o r e a t e a c h s i t e was d i v i d e d i n t o t h r e e z o n e s b a s e d on a l g a l p r e s e n c e ( d e s i g n a t e d I , I I and I I I , from t h e upper t o t h e l o w e r s h o r e ) and a l l measurements and c a l c u l a t i o n s were b a s e d on t h i s d i v i s i o n . 2) F u c u s d i s t i c h u s was most abundant i n Zones I and II o f t h e s h e l t e r e d s i t e s , where i t formed an e x t e n s i v e canopy and o c c a s i o n a l l y a c h i e v e d s t a n d i n g c r o p s of 1 kg d r y wt irr 2 . As wave e x p o s u r e i n c r e a s e d , F ^ d i s t i c h u s abundance d e c r e a s e d . Zone I I I o f t h e s h e l t e r e d s i t e s was c h a r a c t e r i z e d by a s e r i e s of s p r i n g and summer a n n u a l and e p h e m e r a l s p e c i e s ( L e a t h e s i a d i f f o r m i s , C r y p t o s i p h o n i a  woodi i , U l v a f e n e s t r a t a , e t c . ) . The a l g a l community a t t h e more e x p o s e d s i t e was c h a r a c t e r i z e d by a s m a l l p o p u l a t i o n o f F\_ d i s t i c h u s i n Zone I, an " a l g a l t u r f " i n Zone I I , and H e d o p h y l l u m s e s s i l e i n Zone I I I . 276 3) A l l s p e c i e s showed spring/summer maxima and w i n t e r minima i n s t a n d i n g c r o p . In a d d i t i o n , most s p e c i e s were l e s s a bundant d u r i n g summer 1983 compared w i t h summer 1982. M u l t i p l e r e g r e s s i o n a n a l y s e s o f s t a n d i n g c r o p on s e l e c t e d a b i o t i c e n v i r o n m e n t a l f a c t o r s p r o d u c e d e q u a t i o n s w h i c h g e n e r a l l y a c c o u n t e d f o r l e s s t h a n 50% of t h e v a r i a n c e i n a l g a l s t a n d i n g c r o p . 4) The o n l y a bundant h e r b i v o r e s were L i t t o r i n a  s c u t u l a t a and L ^ s i t k a n a . T h e s e a n i m a l s were most abundant i n Zone I of t h e s t u d y s i t e s and may have been p r e s e n t i n s u f f i c i e n t numbers t o l i m i t t h e . abundance o f s e c o n d a r y / e p h e m e r a l s p e c i e s , but p r o b a b l y had l i t t l e i mpact on F. d i s t i c h u s . 5) A l g a l d i v e r s i t y [ exp(H') and 1/q, b a s e d on s t a n d i n g c r o p ] and s p e c i e s r i c h n e s s were l e a s t i n Zones I and II of t h e s h e l t e r e d s i t e s and g r e a t e s t i n Zone I I I . The p a t t e r n a t t h e e x p o s e d s i t e was d i f f e r e n t : d i v e r s i t y was g r e a t e s t i n t h e Zone I I " a l g a l t u r f " a s s e m b l a g e . When p l o t t e d a g a i n s t wave e x p o s u r e and d e s i c c a t i o n s t r e s s , d i v e r s i t y showed a p a t t e r n p r e d i c t e d by t h e h y p o t h e s i s of H u s t o n ( 1 9 7 9 ) . I t was p r o p o s e d t h a t a l g a l d i v e r s i t y was t h e r e s u l t o f t h e 277 i n t e r a c t i v e e f f e c t s of wave a c t i o n and d e s i c c a t i o n s t r e s s , w i t h b i o t i c i n t e r a c t i o n s ( h e r b i v o r y and t h e F ^ d i s t i c h u s c a n o p y ) as s e c o n d a r y i n f l u e n c e s . 6) D i u r n a l p h o t o s y n t h e s i s was measured m o n t h l y i n F u c u s  d i s t i c h u s . Net d a i l y p h o t o s y n t h e s i s was s t r o n g l y c o r r e l a t e d w i t h w ater t e m p e r a t u r e ( m u l t i p l e r e g r e s s i o n a n a l y s i s ) and was g r e a t e s t d u r i n g t h e s p r i n g and summer. 7) A n n u a l p r o d u c t i v i t y was g r e a t e s t i n t h e Zone I and II p o p u l a t i o n s of F_^ d i s t i c h u s a t t h e s h e l t e r e d s i t e s (220-740 g C n r 2 y " 1 ) . . R e g r e s s i o n a n a l y s i s o f d a i l y p r o d u c t i v i t y p e r m 2 of i n t e r t i d a l s u b s t r a t e on s e l e c t e d a b i o t i c e n v i r o n m e n t a l f a c t o r s p r o d u c e d a s i g n i f i c a n t e q u a t i o n , but th e M u l t i p l e - R c o r r e l a t i o n c o e f f i c i e n t was v e r y low. P o s i t i v e n e t d a i l y p r o d u c t i v i t y was o b s e r v e d t h r o u g h o u t t h e y e a r , but i n c r e a s e d wave a c t i o n i n t h e w i n t e r a p p a r e n t l y l i m i t e d a l g a l s t a n d i n g c r o p s . H o u r l y p h o t o s y n t h e t i c r a t e s v a r i e d o n l y s l i g h t l y d u r i n g t h e y e a r , t h u s t h e s e a s o n a l d i f f e r e n c e s i n n e t d a i l y p h o t o s y n t h e s i s were t h e r e s u l t of d i f f e r e n c e s i n d a y l e n g t h , and n o t l i g h t i n t e n s i t y p e r se . I t i s p r o p o s e d t h a t E\_ d i s t i c h u s p r o d u c t i v i t y i s l i m i t e d by wave a c t i o n d u r i n g t h e f a l l and w i n t e r and n u t r i e n t / d e s i c c a t i o n s t r e s s d u r i n g t h e summer. 278 REFERENCES CITED Aleem, A. A. 1956. 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Use of b i o m a s s u n i t s i n Shannons f o r m u l a . E c o l o g y 49:153-156. W i n o k u r , M, 1948. P h o t o s y t h e s i s r e l a t i o n s h i p s o f C h l o r e l l a s p e c i e s . Amer. J . B o t . 35:207-214. Z a v o d n i k , N. 1973. S e a s o n a l v a r i a t i o n s i n r a t e of p h o t o s y n t h e t i c a c t i v i t y and c h e m i c a l c o m p o s i t i o n o f t h e l i t t o r a l seaweeds common t o t h e N o r t h A d r i a t i c . I . F u c u s v i r s o i d e s (Don) J . Ag. B o t . Mar. 16:155-165. 299 APPENDIX A - PHOTOSYNTHESIS-IRRADIANCE CURVES Knowledge o f t h e r e l a t i o n s h i p between r a t e s of p h o t o s y n t h e s i s and i n c i d e n t s u n l i g h t i s f u n d a m e n t a l t o t h e c a l c u l a t i o n and c o m p r e h e n s i o n o f m a c r o a l g a l p r i m a r y p r o d u c t i v i t y . Numerous models have been d e v e l o p e d t o d e s c r i b e t h e PS vs I r e l a t i o n s h i p ; t h e s e have been r e v i e w e d by Lederman and T e t t ( 1 9 8 1 ) . I n c l u d e d i n e a c h of t h e s e m o d e ls i s a p a r a m e t e r w h i c h a c c o u n t s f o r t h e o b s e r v e d p r o p o r t i o n a l i n c r e a s e i n r a t e s o f p h o t o s y n t h e s i s w i t h i n c r e a s i n g l i g h t i n t e n s i t y up t o some s a t u r a t i n g l e v e l . A d d i t i o n a l p a r a m e t e r s i n c l u d e t h e l i g h t i n t e n s i t y a t w h i c h p h o t o s y n t h e s i s i s s a t u r a t e d (IK, as p e r T a i l i n g , 1957) and f u n c t i o n s a c c o u n t i n g f o r t h e i n h i b i t i o n of p h o t o s y n t h e s i s a t h i g h e r l i g h t i n t e n s i t i e s ( p h o t o i n h i b i t i o n ) . R e c e n t work on b o t h p h y t o p l a n k t o n ( H a r d i n g e t e l . , 1982) and m a c r o a l g a e (Ramus and R o s e n b e r g , 1980) have shown t h a t t h e PS vs I r e l a t i o n s h i p may v a r y d i u r n a l l y and s e a s o n a l l y . The p u r p o s e o f t h e f o l l o w i n g e x p e r i m e n t s was t o o b t a i n i n f o r m a t i o n on t h e PS vs I r e l a t i o n s h i p f o r s e l e c t e d m a c r o a l g a e i n t h e s t u d y a r e a . B o t h d i u r n a l and s e a s o n a l a s p e c t s o f t h e r e l a t i o n s h i p were s t u d i e d . The main o b j e c t i v e was t o i d e n t i f y t h a t p h o t o n f l u x d e n s i t y a t w h i c h p h o t o s y n t h e s i s became s a t u r a t e d so t h a t c o r r e c t i o n s c o u l d be 300 made t o o b t a i n more a c c u r a t e e s t i m a t i o n s of a l g a l p r o d u c t i v i t y ( C h a p t e r 6 ) . Methods and M a t e r i a l s E x p e r i m e n t s t o d e t e r m i n e t h e r e l a t i o n s h i p between n e t p h o t o s y n t h e s i s and l i g h t (PS vs I ) were e s s e n t i a l l y m o d i f i e d v e r s i o n s of t h e p r o c e d u r e u s e d t o e s t i m a t e d i u r n a l p h o t o s y n t h e s i s r a t e s ( s e e C h a p t e r 6 ) . C u r v e s were d e t e r m i n e d o n l y on d a y s o f m i n i m a l c l o u d c o v e r and h i g h p h o t o n f l u x d e n s i t y t o e n s u r e s a t u r a t e d r a t e s o f p h o t o s y n t h e s i s and t o c h e c k f o r p h o t o i n h i b i t i o n . I n c u b a t i o n s were begun a t 0930 on t h e day of t h e e x p e r i m e n t . T h r e e s e t s o f 1.5 h i n c u b a t i o n s were r u n s e q u e n t i a l l y d u r i n g t h e day t o t e s t f o r d i u r n a l c h a n g e s i n t h e PS vs I r e l a t i o n s h i p (Ramus and R o s e n b e r g , 1980). E a c h i n c u b a t i o n s e t c o n s i s t e d o f t h r e e c l e a r 300 ml BOD b o t t l e s and t h r e e r e p l i c a t e BOD b o t t l e s wrapped w i t h one t o f o u r l a y e r s of n e u t r a l d e n s i t y s c r e e n i n g (1 mm mesh); c o n t r o l b o t t l e s ( w i t h o u t m a c r o a l g a e ) were a l s o u s e d t o measure p h y t o p l a n k t o n and b a c t e r i a l m e t a b o l i s m . The e x p e r i m e n t s were p e r f o r m e d i n a wet t a b l e i n a g r e e n h o u s e a t t h e B a m f i e l d M a r i n e S t a t i o n . F l o w i n g water a r o u n d t h e b o t t l e s m a i n t a i n e d water t e m p e r a t u r e s ± 1°C t h a t o f t h e s u r f a c e w a t e r i n t h e B a m f i e l d I n l e t . 301 L i g h t a t t e n u a t i o n due t o t h e s c r e e n i n g was d e t e r m i n e d u s i n g a LICOR Model 185A Quantum M e t e r (Lambda I n s t r u m e n t C o r p o r a t i o n ) . A b s o l u t e p h o t o n f l u x d e n s i t y (PAR 400-700 nm) was c a l c u l a t e d a s t h e t o t a l f l u x d u r i n g t h e i n c u b a t i o n p e r i o d (measured w i t h a LICOR MODEL LI-500 I n t e g r a t o r ) m u l t i p l i e d by t h e p e r c e n t a g e of l i g h t a t t e n u a t e d by t h e s c r e e n i n g , e x p r e s s e d a s uE irr2 s ~ 1 . No c o r r e c t i o n s were made f o r a t t e n u a t i o n due t o t h e BOD b o t t l e o r t h e water b a t h , t h u s t h e v a l u e s of PFD t o wh i c h t h e p l a n t s were a c t u a l l y e x p o s e d a r e low e r t h a n t h o s e u s e d i n t h e c a l c u l a t i o n s . In a d d i t i o n , PFD was c o n s t a n t l y c h a n g i n g d u r i n g any s i n g l e i n c u b a t i o n ( d i u r n a l c h a n g e s , c l o u d s , e t c . ) , so t h a t t h e v a l u e s of PFD u s e d a r e t h e mean PFD v a l u e s f o r t h e i n c u b a t i o n p e r i o d . A l t h o u g h l i g h t l e v e l s f l u c t u a t e d d u r i n g t h e i n c u b a t i o n s , and t h e p r o c e d u r e employed d i f f e r e d from t h e u s u a l methods i n d e t e r m i n i n g t h e PS vs I r e l a t i o n s h i p ( i . e . c o n s t a n t l i g h t and t e m p e r a t u r e d u r i n g t h e i n c u b a t i o n s ) , t h e c u r v e s p r o d u c e d s h o u l d be r e p r e s e n t a t i v e o f t h e PS v s I r e l a t i o n s h i p of t h e m a c r o a l g a e i n n a t u r e . R o s e n b e r g and Ramus (1982b) r e p o r t e d l i t t l e d i f f e r e n c e i n t h e PS v s I c u r v e s of U l v a s pp. and G r a c i l a r i a  f o l i i f e r a d e t e r m i n e d Ln s i t u (under f l u c t u a t i n g c o n d i t i o n s ) and i n t h e l a b o r a t o r y (under c o n s t a n t c o n d i t i o n s ) . P h o t o s y n t h e s i s was measured as oxygen e v o l u t i o n u s i n g a 302 Beckman Model 0260 Oxygen A n a l y z e r and c o n v e r t e d t o mg C g d r y wt" 1 h " 1 u s i n g a PQ of 1.20 ( W e s t l a k e , 1963; S t r i c k l a n d and P a r s o n s , 1972). Seawater u s e d i n t h e e x p e r i m e n t s was c o l l e c t e d t h e p r e v i o u s day from t h e s u r f a c e 10-50 m o f f s h o r e o f t h e s t u d y s i t e from w h i c h t h e p l a n t s were c o l l e c t e d . The water was f i l t e r e d t h r o u g h 45 jjm N i t e x s c r e e n i n g and shaken a t i n t e r v a l s f o r one hour b e f o r e use t o e q u i l i b r a t e t h e d i s s o l v e d oxygen i n t h e s e a w a t e r w i t h a t m o s p h e r i c l e v e l s ( L i t t l e r , 1979). A l g a l m a t e r i a l was c o l l e c t e d 24-48 h b e f o r e t h e e x p e r i m e n t s and h a n d l e d as i n t h e d i u r n a l p h o t o s y n t h e s i s e x p e r i m e n t s ( s e e C h a p t e r 6 ) . S p e c i m e n s were c u t t o s i z e so t h a t a l g a l c o n c e n t r a t i o n s i n t h e BOD b o t t l e s d i d not e x c e e d 1.0 g d r y wt l i t e r - 1 . J o h n s t o n (1969) d-id not r e p o r t any n u t r i e n t o r c a r b o n d i o x i d e d e f i c i e n c y p r o b l e m s d u r i n g 24-h e x p e r i m e n t s u s i n g up t o 0.3 g d r y wt a l g a e l i t e r - 1 , so t h e amount o f p l a n t m a t e r i a l u s e d f o r t h e 1.5 h i n c u b a t i o n s s h o u l d n o t have i n f l u e n c e d t h e r e s u l t s . The p l a n t s were h e l d f o r 24-48 h o u r s i n water t r o u g h s i n t h e g r e e n h o u s e e q u i p p e d w i t h f l o w i n g s e a w a t e r and b u b b l e d a i r so th e p o s s i b l e e f f e c t s of w o u n d - i n d u c e d r e s p i r a t i o n w o u l d be m i n i m i z e d . Whole p l a n t s o f C o r a l l i n a V a n c o u v e r i e n s i s and U l v a f e n e s t r a t a were u s e d where p o s s i b l e . P i e c e s o f H e d o p h y l l u m s e s s i l e and L e a t h e s i s d i f f o r m i s were c u t from i n d i v i d u a l t h a l l i w i t h a r a z o r b l a d e . A p i c a l s e c t i o n s o f 303 F u c u s d i s t i c h u s , c o n t a i n i n g a t l e a s t f o u r d i c h o t o m i e s , were u s e d i n t h e e x p e r i m e n t s . The d a t a were f i t t e d t o t h e PS vs I model of S m i t h ( 1 9 3 6 ) , Winokur ( 1 9 4 8 ) , and T a i l i n g ( 1 9 5 7 ) , w h i c h may be w r i t t e n as f o l l o w s (Lederman and T e t t , 1981): PS = PSSAT { a I / [ ( P S S A T ) 2 + ( a I ) 2 ] e x p 0 . 5 } where : PS = r a t e of p h o t o s y n t h e s i s p e r u n i t b i o m a s s (mg C g d r y wt" 1 h ' 1 ) ; PSSAT = l i g h t - s a t u r a t e d (maximum) r a t e o f p h o t o s y n t h e s i s; I = p h o t o n f l u x d e n s i t y (uE m"2 s _ 1 ) ; a = an e m p i r i c a l l y d e t e r m i n e d c o n s t a n t . Note t h a t IK=PSSAT/ a and IK=I where PS=PSSAT/(2)expO.5 Those d a t a p o i n t s w h i c h were v i s u a l l y e s t i m a t e d t o be a t or above t h e a p p a r e n t PFD f o r l i g h t s a t u r a t i o n of p h o t o s y n t h e s i s were summed and t h e mean v a l u e d e s i g n a t e d as PSSAT. L i n e a r r e g r e s s i o n a n a l y s e s (MIDAS) were p e r f o r m e d on t h o s e d a t a p o i n t s w h i c h were a p p a r e n t l y below s a t u r a t i o n l e v e l s and on t h e c o r r e s p o n d i n g a s c e n d i n g l i n e a r ( l i g h t -l i m i t e d ) p o r t i o n of t h e c u r v e ( P i a t t and J a s s b y , 1976). S a t u r a t i o n PFD (PFDSAT) was c a l c u l a t e d by p l u g g i n g t h e mean PSSAT v a l u e i n t o t h e e q u a t i o n g e n e r a t e d by t h e l i n e a r r e g r e s s i o n a n a l y s i s , but o n l y i f t h i s r e g r e s s i o n e q u a t i o n 3 0 4 was s t a t i s t i c a l l y s i g n i f i c a n t ; i n a l l o t h e r c a s e s , PFDSAT was e s t i m a t e d v i s u a l l y f r o m t h e c u r v e s of PS vs I . The IK v a l u e c o u l d a l s o be c a l c u l a t e d o n l y i f a s i g n i f i c a n t r e g r e s s i o n e q u a t i o n had been p r o d u c e d . In t h o s e e x p e r i m e n t s where s a t u r a t e d r a t e s of p h o t o s y n t h e s i s were a p p a r e n t l y o b s e r v e d a t t h e l o w e s t PFD u s e d , PSSAT was c a l c u l a t e d a s t h e mean o f t h e d a t a p o i n t s and PFDSAT as t h e l o w e s t PFD v a l u e where PSSAT was r e c o r d e d . T h e r e was no way t o d e t e r m i n e a or IK i n t h e s e l a t t e r c u r v e s . R e s u l t s and D i s c u s s i o n R e s u l t s of t h e e x p e r i m e n t s and t h e a s s o c i a t e d PS vs I p a r a m e t e r s a r e p r e s e n t e d i n F i g u r e s 28-34 and T a b l e 39. The l a c k of d a t a i n t h e l o w e r PFD ra n g e (< 100 uE r r r 2 s " 1 ) make t h e c o n s t r u c t i o n o f any f i r m c o n c l u s i o n s c o n c e r n i n g t h e PS vs I c u r v e s i m p o s s i b l e . However, t h e low v a l u e s of a and t h e l a r g e y - i n t e r c e p t s f o r t h e c u r v e s s u g g e s t t h a t t h e v a l u e s f o r a a r e not i n d i c a t i v e of t h e PS v s I r e l a t i o n s h i p a t s u b s a t u r a t i n g p h o t o n f l u x d e n s i t i e s f o r t h o s e s p e c i e s where i t was p o s s i b l e t o c a l c u l a t e a . The PSSAT v a l u e s g e n e r a l l y a g r e e w i t h t h e d a t a o b t a i n e d d u r i n g t h e d i u r n a l p h o t o s y n t h e s i s e x p e r i m e n t s ( s e e C h a p t e r 6 ) . However, t h e 21 June 1983 I n c u b a t i o n 3 PSSAT f o r L e a t h e s i a d i f f o r m i s was g r e a t e r t h a n any mean p h o t o s y n t h e t i c 305 Figure 28 Photosynthesis-irradiance curves f o r Fucus d i s t i c h u s from Zone I at Helby. A) 29 Sep 1982 B) 11 Apr 1983 C) 5 July 1983 1.4 A 29 S e p t 1982 i 1 1 1 1— 200 400 600 800 1000 PFD ( ^ / E i n m - ' s - 1 ) O 0"N 1 1 1 ! I 1 1 2 0 0 4 0 0 6 0 0 8 0 0 1000 1300 PFD ( j t E i n -n r ' - s - 1 ) C - 5 J u l y 1983 I 1 1 1 — I 1 1 2 00 4 0 0 6 0 0 8 0 0 1 0 0 0 1600 PFD ( j /E in-m- ' - s - 1 ) Figure 29 Photosynthesis-irradiance curves for Fucus d i s t i c h u s from Zone II at Helby. A) 24 May 1983 B) 8 July 1983 24 M a y 1983 _ , - i 1 — i 1 1 2 0 0 4 0 0 6 0 0 8 0 0 1 0 0 0 1600 PFotf / E i n - m - ' - s - * ) B - 8 J u l y 1983 > 1 i — r • 1 1 1 2 0 0 4 0 0 6 0 0 8 0 0 1000 1 6 0 0 P F D ( * / E i n - m - 2 s - 1 ) Figure 30 Photosynthesis-irradiance curves for Fucus dis t i c h u s from Zone I at Nudibranch. • 29 Sep 1982 • A Aug 1983 1.4H Fucus 1.0H 0.6H 0.2-^  —i r 1000 200 — i 1 r— 400 600 800 PFD (//Ein-nr'-s- 1) 1600 314 Figure 31 Photosynthesis-irradiance curve for Hedophyllum s e s s i l e (21 May 1983). 1.4 Hedophyl lum 1 X H 0.6-r* 0.2H 200 400 600 800 PFD ( j i E inm-'s- 1 ) — I 1 1 1000 1600 Figure 32 Photosynthesis-irradiance curve for C o r a l l i n a vancouveriensis (29 A p r i l 1983). 1.0- C o r a l l i n a 0.6-0.2-—r— 400 —I 1 1 1000 1600 —I— 200 600 800 PFD (^Einm-'-s-') Figure 33 Photosynthesis-irradiance curves for Leathesia d i f f o r m i s . • = 21 June 1983/Incubation 1 • = 21 June 1983/Incubations 2 + 3 O = 29 July 1983/Incubations 1 + 2 • = 29 J u l y 1983/Incubation 3 3.0H Leathes ia 2.4H .O _ . ' _ 1.6-1 • oa . - / * * -I O o • o o • „ ° ° o •• _ _ _ _ _ O _ _ o o.8H ° 0 ; - 0 u - -• O a 1 1 1 1 1 1 1 200 400 600 800 1000 1600 PFD ( / rEin-nr*-*- 1 ) 320 Figure 34 Photosynthesis-irradiance curve for Ulva fenestrata. (7 A p r i l 1983) 4.0H Ulva 3.OH > ? 2.0-o 01 E V) a. 1.0-T 1 1 — T — 200 —I 1— 400 600 PFD(*/E —r— 800 in m - 2 s"' 1000 1600 322 T a b l e 3 9 . C a l c u l a t e d a n d e s t i m a t e d p a r a m e t e r s o f t h e P S v s I r e l a t i o n s h i p o f s e 1 e c t e d i n t e r t i d a l m a c r o a 1 g a e . S P E C I E S / D A T E P F D S A T 1 1 ) P S S A T 1 2 1 a t 3 1 i n • C o r a l l m a V a n c o u v e r l e n s i s 2 9 A p r 11 1 9 8 3 3 6 0 " 0 . 6 4 ± 0 . 1 6 1 . 0 0 * 1 0 ' 1 7 3 F u c u s d 1 s t i c h u s H e l b y - Z o n e I 2 9 S e p t e m b e r 1 9 8 2 5 0 0 . 9 6 1 0 . 1 6 1 1 A p r i l 1 9 8 3 4 3 0 ' 1 . 1 5 ± 0 . 1 0 9 . 5 5 * 1 0 ' 7 3 5 J u l y 1 9 8 3 1 7 5 0 . 7 9 ± 0 . 1 6 H e l b y - Z o n e I I 2 4 M a y 1 9 8 3 1 7 5 0 . 9 0 * 0 . 2 7 8 J u l y 1 9 8 3 4 5 0 1 . 1 1 1 0 . 1 4 N u d i b r a n c h - Z o n e I 2 3 S e p t e m b e r 1 9 8 2 7 5 0 8 2 * 0 . 2 0 4 A u g u s t 1 9 8 3 1 5 0 0 . 8 3 * 0 . 2 1 H e d o p h y l l u m s e s s i l e 2 1 M a y 1 9 8 3 4 2 0 " 0 . 9 8 1 0 1 0 9 . 2 7 x 1 0 • 1 13 L e a t h e s i a d i f f o r m i s 2 1 J u n e 1 9 8 3 I n c u b a t i o n s 1 & 2 1 5 0 0 . 8 7 1 0 . 2 5 I n c u b a t i o n 3 1 0 0 1 . 6 3 * 0 . 3 2 2 9 J u l y 1 9 8 3 I n c u b a t i o n 1 1 5 0 0 . 9 4 * 0 . 3 9 I n c u b a t i o n s 2 6 3 2 0 0 1 . 7 4 1 0 . 9 9 U l v a f e n e s t r a t a 7 A p r i 1 1 9 8 3 1 2 5 2 . 8 8 1 0 . 5 5 N o t e s : ( 1 ) u E i n r r r ' s 1 ( 2 ) m g C g d r y w t - 1 h 1 ( 3 ) m g C g d r y w t ' h 1 P F D * c a l c u l a t e d u s i n g r e g r e s s ' i o n e q u a t i o n a n d P S S S A T I s e e M e t h o d s 1 323 r a t e o b s e r v e d i n t h e d i u r n a l p h o t o s y n t h e s i s e x p e r i m e n t s f o r t h i s p l a n t . T h e r e was l i t t l e e v i d e n c e of p h o t o i n h i b i t i o n i n any o f t h e s p e c i e s s t u d i e d . E x c e p t i n d i f f o r m i s , t h e r e were no a p p a r e n t d i u r n a l d i f f e r e n c e s i n t h e PS vs I r e l a t i o n s h i p s . Where PFDSAT was c a l c u l a t e d , v a l u e s r a n g e d between 360 and 430 pE n r 2 s ~ 1 ; v i s u a l l y e s t i m a t e d v a l u e s were g e n e r a l l y l o w e r (50-200 uE n r 2 s ' 1 ) . A r n o l d and M u r r a y (1980), however, r e p o r t e d t h a t v i s u a l e s t i m a t e s of PFDSAT g e n e r a l l y e x c e e d e d t h e c a l c u l a t e d v a l u e s o f IK i n f i v e g r e e n m a c r o a l g a e . The low PFDSAT v a l u e s o b s e r v e d s u g g e s t t h a t t h e p l a n t s s h o u l d be p h o t o s y n t h e s i z i n g a t maximum r a t e s d u r i n g most of t h e day ( s e e a l s o K a n w i s h e r , 1966). H e d o p h y l l u m  s e s s i l e and C o r a l l i n a V a n c o u v e r i e n s i s may have p h o t o s y n t h e s i s l i m i t e d by t h e a v a i l a b i l i t y o f l i g h t when t h e t i d e s a r e h i g h ( t h e s e p l a n t s were most abundant i n Zones I I and I I I a t N u d i b r a n c h ; see C h a p t e r 3). F u c u s d i s t i c h u s , L e a t h e s i a d i f f o r m i s and U l v a f e n e s t r a t a a r e p r o b a b l y a f f e c t e d o n l y s l i g h t l y by l i g h t a t t e n u a t i o n due t o t h e water c o l u m n . S e l f - s h a d i n g may r e d u c e p h o t o s y n t h e s i s i n F. d i s t i c h u s . However, Niemeck and M a t h i e s o n (1978) r e p o r t e d s a t u r a t i o n of p h o t o s y n t h e s i s a t 200-250 uE n r 2 s " 1 f o r t h r e e s p e c i e s of F u c u s (PFDSAT f o r F\_ d i s t i c h u s i n t h i s s t u d y was e s t i m a t e d a t < 175 pE n r 2 s _ 1 i n 5 of 7 e x p e r i m e n t s ) and s u g g e s t e d t h a t , as t h i s PFD was r e l a t i v e l y low, t h e p o s s i b l e e f f e c t s of s e l f - s h a d i n g s h o u l d be l i m i t e d . 324 L i t t l e s e a s o n a l v a r i a t i o n was o b s e r v e d i n t h e PSSAT f o r F u c u s d i s t i c h u s , a l t h o u g h t h e r e a p p e a r e d t o be some d i f f e r e n c e s i n t h e PFDSAT. The l a c k o f d a t a p o i n t s a t low PFD v a l u e s d i d not p e r m i t t h e c o n s t r u c t i o n of any f i r m c o n c l u s i o n s . D i u r n a l c h a n g e s i n PSSAT were o b s e r v e d i n L e a t h e s i a d i f f o r m i s , but t h e r e was a p p a r e n t l y l i t t l e change i n t h e PFDSAT d u r i n g t h e day. The r e s u l t s of t h e s e e x p e r i m e n t s show t h a t p h o t o s y n t h e s i s i n t h e i n t e r t i d a l m a c r o a l g a e s t u d i e d i s g e n e r a l l y s a t u r a t e d a t low l i g h t l e v e l s ; f u t u r e s t u d i e s s h o u l d c o n c e n t r a t e on a r a n g e of p h o t o n f l u x d e n s i t i e s between 0 and 600 pE i r r 2 s " 1 t o e n s u r e o b t a i n i n g s a t u r a t e d r a t e s as w e l l as a s u i t a b l e number o f d a t a p o i n t s on t h e a s c e n d i n g l i n e a r p o r t i o n of t h e c u r v e . T h e r e i s l i t t l e e v i d e n c e of p h o t o i n h i b i t i o n , even a t p h o t o n f l u x d e n s i t i e s g r e a t e r t h a n 1500 pE nr 2 s - 1 . The i n t e r t i d a l m a c r o a l g a e s t u d i e d s h o u l d t h u s be p h o t o s y n t h e s i z i n g a t maximum r a t e s most o f t h e t i m e on a l l b u t o v e r c a s t d a y s . 

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