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Plankton blooms of the British Columbia northern shelf : seasonal distributions and mechanisms influencing… Perry, Richard Ian 1984

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PLANKTON BLOOMS OF THE BRITISH COLUMBIA NORTHERN SHELF: SEASONAL DISTRIBUTIONS AND MECHANISMS INFLUENCING THEIR FORMATION by RICHARD IAN PERRY B.Sc.(Hons.) U n i v e r s i t y of B r i t i s h Columbia, 1977 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES Zoology We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH September 1984 © Richard Ian Perry, COLUMBIA 1 984 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 for an advanced degree at the The U n i v e r s i t y of B r i t i s h Columbia, I agree that 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 r e f e r e n c e and study. I f u r t h e r agree that p ermission fo 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 of my Department or 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 that 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 p e r m i s s i o n . Zoology The U n i v e r s i t y of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date: September 1984 ABSTRACT The f i r s t d e s c r i p t i o n i s presented of s p a t i a l and seasonal d i s t r i b u t i o n s of plankton blooms, and p h y s i c a l oceanographic c o n d i t i o n s u n d e r l y i n g t h e i r formation, on the B r i t i s h Columbia northern s h e l f . T h i s region i n c l u d e s Queen C h a r l o t t e S t r a i t and Sound, Hecate S t r a i t , Dixon Entrance and t h e i r contiguous waters. I t s b i o l o g i c a l oceanographic c h a r a c t e r i s t i c s are v i r t u a l l y unknown, yet i t has v a l u a b l e petroleum and f i s h e r y r e s o u r c e s . Samples were c o l l e c t e d between March 1978 and August 1980 u s i n g a c o a s t a l o i l tanker as a s h i p of o p p o r t u n i t y . Fourteen c r u i s e s were conducted, c o n c e n t r a t e d d u r i n g s p r i n g and summer. Samples for s a l i n i t y , n u t r i e n t s , phytoplankton composition and pigments were c o l l e c t e d from the sea water intake system (depth 3 m) while underway. Zooplankton were c o l l e c t e d with a M i l l e r sampler towed from the s t e r n ; temperature p r o f i l e s were obtained with an XBT system. L i g h t p e n e t r a t i o n and v e r t i c a l mixing c h a r a c t e r i s t i c s were the p r i n c i p a l p h y s i c a l p r o p e r t i e s l e a d i n g to i n i t i a t i o n of phytoplankton blooms i n s p r i n g and summer. The s p r i n g (diatom) bloom was p r e d i c t e d by a c r i t i c a l - mixed depth model c a l c u l a t e d from h i s t o r i c a l data. Summer blooms were p r e d i c t e d by a t i d a l f r o n t model, which compares t i d a l v e l o c i t i e s with water depth. Bathymetry i s the common f e a t u r e of these two mechanisms, l i m i t i n g the mixed depth i n s p r i n g and m a i n t a i n i n g t i d a l mixing i i i n shallow regions d u r i n g summer. The s p r i n g bloom progressed northward with i n c r e a s i n g i r r a d i a n c e , o c c u r r i n g during February - March in the S t r a i t of Georgia and during May i n Dixon Entrance. However, i t was p r e d i c t e d and observed e a r l i e r in Hecate S t r a i t ( A p r i l ) , where a shallow s h e l f l i m i t s the mixed depth, than i n more s o u t h e r l y Queen C h a r l o t t e Sound. The bloom in Queen C h a r l o t t e Sound f i r s t developed along i t s southeastern coast, a p p a r e n t l y due to r u n o f f - r e l a t e d s t r a t i f i c a t i o n . On the s c a l e of sampling, zooplankton blooms in s p r i n g o c c u r r e d i n the same areas as phytoplankton. During summer, o b s e r v a t i o n s confirmed low biomass ( f l a g e l l a t e s ) and well-mixed c o n d i t i o n s i n shallow western Hecate S t r a i t , and high biomass (diatoms) and s t r a t i f i e d c o n d i t i o n s on i t s eastern s i d e . However, mean mixed l a y e r l i g h t i n t e n s i t i e s were s i m i l a r , and n e a r - s u r f a c e n u t r i e n t c o n c e n t r a t i o n s low, on both s i d e s of the s t r a i t . Phytoplankton on the shallow s i d e were probably l i m i t e d by r a t e s of n u t r i e n t resupply, while the e a s t e r n s i d e r e c e i v e d n u t r i e n t s from upwelling or s p o r a d i c mixing by storms. T h i s may d i s t i n g u i s h the e f f e c t of t i d a l mixing in s h e l f seas and s t r a i t s , with advection of n u t r i e n t s to the mixed region of s t r a i t s reduced by the shallow bottom and adjacent land boundaries. Table of Contents ABSTRACT i i LIST OF TABLES v i i i LIST OF FIGURES x PREFACE xv ACKNOWLEDGEMENTS xv i I. GENERAL INTRODUCTION AND OBJECTIVES 1 1 . O b j e c t i v e s 7 2. Chapter Synopses 8 I I . PHYSICAL OCEANOGRAPHY OF THE NORTHERN SHELF: A BRIEF REVIEW 11 1. I n t r o d u c t i o n 11 2. Physiography 11 3. Winds 13 4. T i d e s 14 5. C i r c u l a t i o n 14 6. Temperature and S a l i n i t y 16 7. Subsurface C h a r a c t e r i s t i c s 17 I I I . GENERAL METHODS 18 1. I n t r o d u c t i o n 18 2. Background 21 3. V e s s e l 22 4. L o g i s t i c s 22 5. Sample C o l l e c t i o n 25 6. Temperature 26 7. S a l i n i t y 27 i v 8. N u t r i e n t s 27 9. Phytoplankton 28 10. Zooplankton 30 1 1 . Problems 31 12. Comparison of Surface and Depth Sampling 33 IV. BIOLOGICAL OCEANOGRAPHY OF THE NORTHERN SHELF: SEASONAL PATTERNS 40 A. I n t r o d u c t i o n 40 1. Previous S t u d i e s 42 B. Methods 48 1. C r i t i c a l Depth Model 48 2. C a l c u l a t i o n of C r i t i c a l Depths 50 C. R e s u l t s 56 1. C r i t i c a l Depth Model 56 2. P h y s i c a l P r o p e r t i e s 61 3. C h l o r o p h y l l ..63 4. N u t r i e n t s 69 5. Phytoplankton 70 6. Zooplankton 74 7. A n a l y s i s of Bloom Timing 76 8. Southeastern Queen C h a r l o t t e Sound 79 D. D i s c u s s i o n 89 1. Spring Bloom Timing 91 2. C o a s t a l Queen C h a r l o t t e Sound 95 E. Summary 97 V. SUMMER PLANKTON DISTRIBUTIONS IN HECATE STRAIT 101 v A. I n t r o d u c t i o n ..101 1. L i t e r a t u r e Review 103 B. Methods 108 C. R e s u l t s 110 1. T i d a l Model 110 2. B i o l o g i c a l D i s t r i b u t i o n s 115 D. D i s c u s s i o n 125 E. Summary 133 VI. MECHANISMS OF SEASONAL PLANKTON BLOOMS IN HECATE STRAIT 1 34 A. I n t r o d u c t i o n 134 B. Methods 136 C. R e s u l t s 141 1 . F i e l d Data 141 2. Phytoplankton Taxonomic Composition 143 3. Seasonal Composition P a t t e r n s 147 4. S p a t i a l Scale Estimates 149 5. R e l a t i o n to Bathymetry 153 6. Spring Bloom I n i t i a t i o n 157 D. D i s c u s s i o n 159 E. Summary 166 V I I . GENERAL CONCLUSIONS AND SUMMARY 168 1. Conclusions 168 2. Future Studies 175 3. General Summary 178 LITERATURE CITED 181 v i APPENDIX I 1 99 APPENDIX II 212 APPENDIX III 218 APPENDIX IV 219 v i i LIST OF TABLES TABLE I. MV I m p e r i a l T o f i n o c r u i s e numbers, dates, and number of s t a t i o n s sampled f o r the d u r a t i o n of the s h i p of o p p o r t u n i t y program 25 TABLE I I . Regression equations comparing near s u r f a c e (SHOP, 4 m) and depth sampled c h l o r o p h l y l l a and N0 3+N0 2 c o n c e n t r a t i o n s c o l l e c t e d during Pandora II c r u i s e 80-7 (28 A p r i l - 3 May 1980) to the B.C. northern s h e l f 37 TABLE I I I . Comparison of zooplankton taxonomic groups sampled by Pandora II using M i l l e r (MLR) and v e r t i c a l (VERT) net tows 39 TABLE IV. Monthly mean c h l o r o p h y l l a c o n c e n t r a t i o n s and va r i a n c e s on the B.C. northern s h e l f as measured on Imperial Tofino c r u i s e s 65 TABLE V. Q u a l i t a t i v e s p r i n g bloom a n a l y s i s f o l l o w i n g the technique of Braard and Nygaard (1978) a p p l i e d to B.C. c o a s t a l waters 77 TABLE VI. Normal d a i l y s o l a r r a d i a t i o n values f o r each month (measured as MJ n r 2 d" 1) f o r three s t a t i o n s on the B.C. coast r e p r e s e n t a t i v e of the S t r a i t of Georgia (Nanaimo), Queen C h a r l o t t e Sound (Cape St. James), and Hecate S t r a i t ( S a n d s p i t ) . Data are from the Monthly R a d i a t i o n Summary, Atmospheric Environment S e r v i c e , Ottawa 92 TABLE V I I . C o r r e l a t i o n of bulk s u r f a c e s t r a t i f i c a t i o n (Act from s u r f a c e to 50 m or the bottom) with the t i d a l s t r a t i f i c a t i o n parameter (S) f o r g r i d squares i n which they c o i n c i d e 115 TABLE V I I I . P r o p o r t i o n a l s i m i l a r i t y of s t a t i o n s based on t h e i r c e n t r i c "and pennate diatom compositions using the sample-size independent index of Kohn and Riggs (1982). .118 TABLE IX. Phytoplankton taxonomic groups, r e l a t i v e s i z e c o e f f i c i e n t s and mean abundances f o r C r u i s e s 10 (June 1979), 12 (Feb. 1980) and 13 ( A p r i l 1980) 138 v i i i TABLE X. Estimated s t r u c t u r e f u n c t i o n s f o r parameters measured at d i s c r e t e s t a t i o n s and grouped i n t o d i s t a n c e c a t e g o r i e s . C r u i s e 11, J u l y 1979; C r u i s e 13, A p r i l 1980. Distance c a t e g o r i e s are i n km 1 ix LIST OF FIGURES FIGURE 1. G e n e r a l i z e d map of the B.C. northern s h e l f study area showing l o c a t i o n s of place names r e f e r r e d to i n the text 12 FIGURE. 2. O u t l i n e of the p o s s i b l e routes of the Imperial Tofino on t r i p s to the northern s h e l f . Not a l l routes were followed on every c r u i s e 23 FIGURE 3. C r i t i c a l depth ( s o l i d l i n e ) and mixed depth (dashed l i n e ) 95% confidence i n t e r v a l s of monthly means from 1954 to 1971 i n the S t r a i t of Georgia (A), Queen C h a r l o t t e Sound (B), Hecate S t r a i t (C), and Dixon Entrance (D) 57 FIGURE 4. Near s u r f a c e (3 m) t e m p e r a t u r e / s a l i n i t y p l o t s f o r C r u i s e 12 (February 1980; A) and C r u i s e 11 ( J u l y 1979; B), with s t a t i o n s grouped i n t o geographic areas 62 FIGURE 5. Temporal d i s t r i b u t i o n of 3 m c h l o r o p h y l l as sampled by Imperial Tofino in Queen C h a r l o t t e Sound and S t r a i t , Hecate S t r a i t , and Dixon Entrance. Values are presented as c h l a monthly means ± 1 standard d e v i a t i o n . 64 FIGURE 6. A. C h l o r o p h y l l a (ng L" 1) s p a t i a l d i s t r i b u t i o n on 10-17 A p r i l 1980 (C r u i s e 13). Crosses represent s t a t i o n l o c a t i o n s . B. Histograms of N0 3+N0 2 c o n c e n t r a t i o n s (MM) measured at the same l o c a t i o n s as c h l o r o p h y l l , and grouped i n t o geographic areas 67 FIGURE 7. A. C h l o r o p h y l l a (u9 L" 1) s p a t i a l d i s t r i b u t i o n on 1-7 June 1980 (C r u i s e 14). Crosses represent s t a t i o n l o c a t i o n s . B. Histograms of N0 3+N0 2 c o n c e n t r a t i o n s (ixM) measured at the same l o c a t i o n s as c h l o r o p h y l l , and grouped i n t o geographic areas 68 FIGURE 8. Frequency of s t a t i o n s sampled by Imperial Tofino on the northern s h e l f where the c a l c u l a t e d diatom biomass index (see t e x t ) i s g r e a t e r than the f l a g e l l a t e biomass index 72 x FIGURE 9. L o c a t i o n map showing the route of Imperial Tofino (dashed l i n e ) through southeastern Queen C h a r l o t t e Sound and place names r e f e r r e d to i n the text 80 FIGURE 10. Imperial Tofino t r a n s e c t through c o a s t a l Queen C h a r l o t t e Sound, 1-8 A p r i l 1979 ( C r u i s e 8). Data are from d i s c r e t e s t a t i o n s at 3 m depth, not continuous t r a n s e c t s ; f o r p r e c i s e s t a t i o n l o c a t i o n s see Appendix I. 82 FIGURE 11. Imperial Tofino t r a n s e c t through c o a s t a l Queen C h a r l o t t e Sound, 9-16 May 1979 ( C r u i s e 9). Data are from d i s c r e t e s t a t i o n s at 3 m depth. 83 FIGURE 12. Imperial Tofino t r a n s e c t through c o a s t a l Queen C h a r l o t t e Sound, 16-27 J u l y 1979 ( C r u i s e 11). For s t a t i o n l o c a t i o n s see Appendix I 85 FIGURE 13. Near s u r f a c e (4 m) c h l o r o p h y l l (jug L" 1 ) d i s t r i b u t i o n as measured on 29 A p r i l 1980 by Pandora II (DOUBC c r u i s e 80-7) i n southeastern Queen C h a r l o t t e Sound 86 FIGURE 14. V e r t i c a l p r o f i l e s of c h l o r o p h y l l a (top, S t a t i o n s 7,8,13,22) and temperature and s a l i n i t y (bottom, S t a t i o n s 7 and 8) measured by Pandora II on 29 A p r i l 1980 i n southeastern Queen C h a r l o t t e Sound 88 FIGURE 15. Bathymetric map of Hecate S t r a i t (depths in meters) showing l o c a t i o n s of s t a t i o n s on C r u i s e 10 (squares), 11 ( c i r c l e s ) , and 14 (diamonds). Dashed l i n e i n d i c a t e s route of continuous t r a n s e c t d u r i n g C r u i s e 15. 102 FIGURE 16. Diagram i l l u s t a t i n g the b a s i c s t r u c t u r e of a shallow sea t i d a l f r o n t (p, < p2 < P 3 ) . H i s the t o t a l water depth, h the depth of the s u r f a c e wind mixed l a y e r ; f o r f u r t h e r d e t a i l s , see t e x t . 105 FIGURE 17. T i d a l c u r r e n t e l l i p s e s computed from the o i l s p i l l d r i f t p r e d i c t i o n model f o r Hecate S t r a i t and Dixon Entrance. Redrawn with permission a f t e r Kinney et al. (1976) 111 x i FIGURE 18. C a l c u l a t i o n s of t h e Simpson - H u n t e r s t r a t i f i c a t i o n p a r a m e t e r , w i t h h t h e d e p t h o f t h e wa t e r , U t h e t i d a l c u r r e n t v e l o c i t y a v e r a g e d o v e r one t i d a l c y c l e ( b o t h c g s u n i t s ) , and a d r a g c o e f f i c i e n t (Cd ) of 0 . 0025 112 FIGURE 19. B u l k s t r a t i f i c a t i o n , t h e at d i f f e r e n c e f r o m t h e s u r f a c e t o t h e bottom o r 50 m ( w h i c h e v e r i s l e s s ) n o r m a l i z e d p e r meter, f o r H e c a t e S t r a i t and D i x o n E n t r a n c e . D a t a p r e s e n t e d a r e a c o m p o s i t e o f J u n e , J u l y and A u g u s t c a l c u l a t e d from t e m p e r a t u r e and s a l i n i t y measurements from 1954 t o 1971 ....114 FIGURE 20. D a t a from C r u i s e 10, n o r t h e r n t r a n s e c t from Chatham Sound t o S a n d s p i t , June 27, 1979. A. Near s u r f a c e (3 m) c h l o r o p h y l l a (ng L " 1 ) , N0 3+N0 2 (Mmol L " 1 ) , d i a t o m s ( l o g 1 0 Number L~ 1 ) . B. Near s u r f a c e c o p e p o d s , o t h e r z o o p l a n k t o n (non-copepod z o o p l a n k t o n ) , s a l i n i t y and t e m p e r a t u r e . C. V e r t i c a l d o t s r e p r e s e n t XBT t e m p e r a t u r e p r o f i l e s ; b a t h y m e t r y i s a p p r o x i m a t e d from t h e s e p r o f i l e s . 116 FIGURE 21. C r u i s e 10, c e n t r a l t r a n s e c t from S a n d s p i t t o P r i n c e R u p e r t , 28 June 1979. D e t a i l s of A, B, C as f o r F i g . 20 119 FIGURE 22. C r u i s e 11, 24 J u l y 1979. D e t a i l s o f A, B, C as f o r F i g . 20 121 FIGURE 23. C r u i s e 14, 2-4 June 1980. D e t a i l s o f A, B, C as f o r F i g . 20 1 22 FIGURE 24. C r u i s e 15, 30 A u g u s t 1980. C o n t i n u o u s t r a n s e c t f r o m S a n d s p i t , Queen C h a r l o t t e I s l a n d s , t o K i t k a t l a , i n d i c a t e d on F i g . 15. Top: n e a r s u r f a c e (3 m) t e m p e r a t u r e . M i d d l e : n e a r s u r f a c e r e l a t i v e f l u o r e s c e n c e . Bottom: v e r t i c a l t e m p e r a t u r e s t r u c t u r e (°C) from XBT p r o f i l e s ( v e r t i c a l d o t s ) and t h e a p p r o x i m a t e b a t h y m e t r y 124 FIGURE 25. H e c a t e S t r a i t b a t h y m e t r y ( d e p t h s i n m e t e r s ) and s t a t i o n l o c a t i o n s f o r C r u i s e 12 ( s q u a r e s ) and C r u i s e 13 ( c i r c l e s ) . Dashed box a c r o s s H e c a t e S t r a i t i n d i c a t e s t h e a r e a a v e r a g e d f o r t h e s a t e l l i t e z o n a l IR b r i g h t n e s s x i i sect ion 137 FIGURE 26. D i s c r e t e s t a t i o n data f o r C r u i s e 13 (13-14 A p r i l 1980) a c r o s s Hecate S t r a i t . S t a t i o n l o c a t i o n s as i n F i g . 25. Top: 3 m c h l . a, N0 3+N0 2, diatom abundance; Middle: 3 m temperature and s a l i n i t y ; Bottom: maximum depth at each s t a t i o n 142 FIGURE 27. D i s c r e t e s t a t i o n data f o r C r u i s e 12 (3-5 February 1980) a c r o s s Hecate S t r a i t 144 FIGURE 28. Phytoplankton taxonomic composition histograms for east and west Hecate S t r a i t during winter 1980 (A), s p r i n g 1980 (B) and summer 1979 (C) 145 FIGURE 29. C l u s t e r phenogram of s t a t i o n s sampled i n Hecate S t r a i t d u r i n g summer 1979, winter and s p r i n g 1980 using chord d i s t a n c e s c a l c u l a t e d from phytoplankton taxonomic composition 1 48 FIGURE 30. TIROS-N ( o r b i t number 9882) AVHRR sea su r f a c e i n f r a r e d b r i g h t n e s s values a c r o s s Hecate S t r a i t on 12 Sept. 1980. A. Zonal s e c t i o n of averaged values from the boxed area i n F i g . 25. Li n e i s the l i n e a r l e a s t square f i t to detrend the. data. B. S t r u c t u r e f u n c t i o n estimates from the detrended data in A 150 FIGURE 31. S t r u c t u r e f u n c t i o n estimates of continuous 3 m f l u o r e s c e n c e across Hecate S t r a i t measured on 30 August 1 980 1 52 FIGURE 32. Bathymetric p r o f i l e a cross Hecate S t r a i t from Lawn Po i n t (Queen C h a r l o t t e I s l a n d s ) to Browning Entrance, 30 August 1980 155 FIGURE 33. Hecate S t r a i t c r i t i c a l depth - mixed depth model r e s u l t s c a l c u l a t e d as d e s c r i b e d i n t e x t . H o r i z o n t a l dashed l i n e r e presents mean bottom depth of the set of s t a t i o n s sampled that month. Data are a composite from 1 954 to 1 971 1 58 FIGURE 34. Monthly mean mixed l a y e r l i g h t i n t e n s i t i e s f o r x i i i west ( s o l i d l i n e ) and east (short dashed l i n e ) Hecate S t r a i t . V e r t i c a l bars represent 95% c o n f i d e n c e i n t e r v a l s of the mean. Long dashed l i n e r e presents the l i g h t i n t e n s i t y suggested by Gieskes and Kraay (1975) as the c r i t i c a l i n t e n s i t y f o r phytoplankton blooms 1 x i v PREFACE T h i s t h e s i s presents an a n a l y s i s of data c o l l e c t e d in the U n i v e r s i t y of B r i t i s h Columbia, Dept. of Oceanography s h i p of o p p o r t u n i t y program. These data have been made a v a i l a b l e i n two data r e p o r t s , and so are not i n c l u d e d i n t h i s t h e s i s as appendices. These r e p o r t s a re: D i l k e , B.R., S. M c K i n n e l l and R.I. Perr y . 1979. M.V. Imperial Tofino s h i p of op p o r t u n i t y program. March 1978 to March 1979. U n i v e r s i t y of B.C., Dept. of Oceanography Data Rept. No. 46. 1 1 1p. Perry, R.I., B.R. D i l k e , G.C. L o u t t i t and S. M c K i n n e l l . 1981. M.V. Imperial Tofino s h i p of o p p o r t u n i t y program. May 1979 to June 1980. U n i v e r s i t y of B.C., Dept. of Oceanography Data Rept. No. 49. 159p. They are a v a i l a b l e by w r i t i n g The L i b r a r i a n Dept. of Oceanography U n i v e r s i t y of B.C. Vancouver, B.C. V6T 1W5 Canada xv ACKNOWLEDGEMENTS Many people helped enormously with the completion of t h i s t h e s i s . I thank my s u p e r v i s o r , T. R. Parsons, f o r a l l h i s support and encouragement, and f o r i n i t i a t i n g the s h i p of opp o r t u n i t y p r o j e c t ; and Imperial O i l of Canada, L t d . , f o r the use of, and support onboard, the Imperial Tofino. I thank my f r i e n d s and c o l l e a g e s who worked with the SHOP p r o j e c t and r e l a t e d c r u i s e s , e s p e c i a l l y B. R. D i l k e , S. M c K i n n e l l , and G.C. L o u t t i t , who c o l l e c t e d the m a j o r i t y of samples. C. H. Mungall ( K i n n e t i c Labs, Santa Cruz, CA) provided the t i d a l model; W. J . Emery p r o v i d e d the XBT system and s a t e l l i t e images; P. B. Crean and the Marine Environmental Data S e r v i c e , Ottawa, provided the p h y s i c a l d a t a . I f i n a l l y thank J . S. Parslow f o r i n v a l u a b l e d i s c u s s i o n s , and H. Dovey f o r d r a f t i n g the f i g u r e s . The author was supported d u r i n g t h i s r e s e a r c h by N a t i o n a l Science and Engi n e e r i n g Research C o u n c i l S c h o l a r s h i p s and a U n i v e r s i t y Graduate F e l l o w s h i p . x v i I. GENERAL INTRODUCTION AND OBJECTIVES The c o a s t a l waters of B r i t i s h Columbia cover an ex t e n s i v e area and i n c l u d e f j o r d s , passages, and a narrow c o n t i n e n t a l s h e l f . They can be d i v i d e d i n t o three broad r e g i o n s on the b a s i s of geographic l o c a t i o n , oceanographic c h a r a c t e r i s t i c s , and the i n t e n s i t y of research e f f o r t expended in t h e i r i n v e s t i g a t i o n . T h i s study i s concerned with one of these r e g i o n s , the northern s h e l f , which has resources of great economic p o t e n t i a l yet i s poo r l y known o c e a n o g r a p h i c a l l y . I t i s the f i r s t study to d e s c r i b e the s p a t i a l and temporal d i s t r i b u t i o n s of plankton blooms from winter to summer i n t h i s r egion, a p r e r e q u i s i t e to more d e t a i l e d p r o d u c t i v i t y and f i s h e r i e s i n v e s t i g a t i o n s . P h y s i c a l mechanisms i n i t i a t i n g these blooms are a l s o examined to understand where and how blooms develop and t h e i r p o t e n t i a l impact upon resources of the northern c o a s t . The S t r a i t of Georgia, and oceanic waters to the west of the Queen C h a r l o t t e and Vancouver I s l a n d s , make up the two other broad regions of the B.C. c o a s t . The S t r a i t of Georgia and i t s adjacent i n l e t s can be c o n s i d e r e d as inshore estuarine-dominated due to the F r a s e r River and the v a r i o u s i s l a n d b a r r i e r s to c i r c u l a t i o n and exchange with the open P a c i f i c . Wide s p a t i a l and seasonal v a r i a t i o n s of temperature are apparent (Thomson 1 9 8 1 ) . Studies on the S t r a i t date from plankton records i n 1915 ( B a i l e y and Mackay 1916) and i t has remained the most i n t e n s i v e l y s t u d i e d r egion of the c o a s t . A recent survey of l i t e r a t u r e 1 2 p e r t a i n i n g to or based on these waters l i s t s over 300 r e f e r e n c e s to b i o l o g i c a l and p h y s i c a l r e s e a r c h ( H a r r i s o n et al . i n p r e s s ) . The r e l a t i v e l y benign oceanographic c l i m a t e and i t s p r o x i m i t y to c e n t e r s of p o p u l a t i o n and re s e a r c h are obvious reasons c o n t r i b u t i n g to t h i s e x t e n s i v e study. The second r e g i o n , the o f f s h o r e oceanic r e g i o n , i n c l u d e s waters west of Vancouver I s l a n d and the Queen C h a r l o t t e I s l a n d s . In general there i s a narrow c o n t i n e n t a l s h e l f , l i t t l e d i r e c t freshwater input, and more constant temperature and s a l i n i t y c h a r a c t e r i s t i c s than the S t r a i t of Georgia. The region o f f Vancouver I s l a n d and the mouth of Juan de Fuca S t r a i t has r e c e n t l y r e c e i v e d c o n s i d e r a b l e r e s e a r c h a t t e n t i o n , much of i t r e s u l t i n g from i t s importance i n salmonid m i g r a t i o n s . R e p r e s e n t a t i v e s t u d i e s have been made by Denman et al. (1981) and F r e e l a n d and Denman (1982). The B.C. northern s h e l f and i t s adjacent waters comprise the t h i r d major r e g i o n . T h i s region i n c l u d e s Queen C h a r l o t t e S t r a i t , Queen C h a r l o t t e Sound, Hecate S t r a i t , and Dixon Entrance (Thomson 1981) and i s almost ten times the area of the S t r a i t of Georgia. I t i s intermediate i n i t s oceanographic p r o p e r t i e s , being i n f l u e n c e d d i r e c t l y by r i v e r runoff yet a l s o being open to oceanic waters v i a Dixon Entrance and Queen C h a r l o t t e Sound, and has the most ext e n s i v e c o n t i n e n t a l s h e l f of the B.C. c o a s t . I t i s a l s o intermediate i n the amount of research e f f o r t i t has r e c e i v e d , with e a r l y r e p o r t s of phytoplankton composition from the U n i t e d S t a t e s Navy ( A l l e n 1927), and s e v e r a l major p h y s i c a l 3 oceanographic surveys conducted d u r i n g the 1950's and 1960's. Tabata (1980) l i s t s some 70 p r i m a r i l y p h y s i c a l r e p o r t s and papers concerning t h i s r e g i o n , while i t s b i o l o g i c a l oceanography has been almost e n t i r e l y n e g l e c t e d d u r i n g t h i s p e r i o d . The northern s h e l f of B r i t i s h Columbia i s p o t e n t i a l l y of great economic importance to B.C. and Canada, having e x t e n s i v e l i v i n g and n o n - l i v i n g marine r e s o u r c e s . The p r i n c i p a l n o n - l i v i n g resource c u r r e n t l y c o n s i d e r e d f o r e x p l o i t a t i o n i s petroleum. The f i r s t r e p o rt of hydrocarbons o f f mainland B.C. was a gas f l a r e from a w e l l d r i l l e d in 1913-1915 on the Queen C h a r l o t t e Islands (Haimila and Proct o r 1982). Subsequent d r i l l i n g i n the adjacent o f f s h o r e has occurred as r e c e n t l y as 1967-1971, when a moratorium on e x p l o r a t i o n d r i l l i n g was imposed. Estimates made in 1980 of the n a t u r a l gas and o i l p o t e n t i a l of B.C. o f f s h o r e areas suggest an average e x p e c t a t i o n of 265x10 s m3 of gas and 38.5X10 6 m3 of o i l , with the l a r g e s t area being the northern s h e l f (Haimila and Pr o c t o r 1982). In September 1983, an agreement was reached between p r o v i n c i a l and f e d e r a l governments concerning formation of a j o i n t west coast environmental review panel f o r assessment of o f f s h o r e hydrocarbon e x p l o r a t i o n on the northern s h e l f . I t i s to rep o r t i n l a t e 1984 on c o n d i t i o n s f o r p o s s i b l e removal of the moratorium a g a i n s t e x p l o r a t i o n a c t i v i t i e s . T h i s t h e s i s i s t h e r e f o r e a t i m e l y a d d i t i o n to background knowledge concerning the b i o l o g y of t h i s r e g i o n . Two other s t u d i e s of the environmental and s o c i a l concerns f o r o f f s h o r e hydrocarbon 4 e x p l o r a t i o n and development i n B.C. are McPhee (1982) and Langford (1983). The importance of the northern s h e l f r e gion f o r l i v i n g marine resources i s due both to l o c a l and migratory stocks of f i n f i s h and s h e l l f i s h . W i t h l e r and Wong (1983) reviewed o b s e r v a t i o n s of salmon i n Hecate S t r a i t and adjacent waters and noted that they c o n t r i b u t e s i g n i f i c a n t l y to B.C.'s commercial salmon l a n d i n g s . Hecate S t r a i t i s a l s o an important pathway f o r out m i g r a t i n g j u v e n i l e s and maturing a d u l t s r e t u r n i n g to t h e i r spawning streams. The j u v e n i l e s are produced both l o c a l l y and from streams f u r t h e r south, and appear to feed and grow in the s t r a i t from mid-July to November (Withler and Wong 1983). Another i m p o r t a n t . f i s h e r y resource are h e r r i n g (Clupea harengus pallasi), which spawn i n s p e c i f i c l o c a t i o n s along the coast and then migrate i n t o open waters of the northern s h e l f ( T a y l o r 1964). Langford (1983) r e p o r t s that Dixon Entrance and Hecate S t r a i t accounted f o r 27% of h e r r i n g l a n d i n g s and 77% of the h e r r i n g spawn-on-kelp harvest f o r B.C. from 1978-1980. Groundfish f i s h e r i e s are very important on the northern s h e l f , p r o v i d i n g 63.1% of the annual B.C. g r o u n d f i s h c a t c h du r i n g 1976-1980 (Langford 1983). Observations on s a b l e f i s h (Anoplopoma fimbria), c u r r e n t l y with the hig h e s t landed value of a l l g r o u n d f i s h on Canada's P a c i f i c c oast, suggest j u v e n i l e s may remain i n c o a s t a l waters of the northern s h e l f u n t i l they mature (Mason el al. 1983). P a c i f i c cod (Gadus macrocephal us) and h a l i b u t (Hippogl ossus stenolepis) are a l s o important resources, 5 p a r t i c u l a r i l y i n Hecate S t r a i t . A recent f i s h e r y f o r abalone (Haliotis kamt schat kana) i s l o c a t e d on both s i d e s of Hecate S t r a i t , mostly among kelp beds o f f Moresby I s l a n d and Banks I s l a n d (Breen 1980). A long-term f i s h e r y has a l s o e x i s t e d f o r Dungeness crab on the north coast of Graham I s l a n d in Dixon Entrance. C o n s i d e r a b l e p o p u l a t i o n s of marine mammals, sea b i r d s , and marine p l a n t s a l s o e x i s t on the northern s h e l f , although l i t t l e i s known of t h e i r d i s t r i b u t i o n s . Langford (1983) has compiled a review of the b i o l o g y of B.C. c o a s t a l waters, with s e v e r a l maps i l l u s t r a t i n g p o s s i b l e d i s t r i b u t i o n s of many of the f o r e g o i n g marine p o p u l a t i o n s . While the resources of the northern s h e l f are e x t e n s i v e and the region serves as a probable nursery area f o r l a r v a l and j u v e n i l e f i s h (e.g. Ketchen 1956, W i t h l e r and Wong 1983), no systematic s t u d i e s have been conducted to examine the d i s t r i b u t i o n and r e g u l a t i n g mechanisms of p o t e n t i a l p l a n k t o n i c food items. A c c o r d i n g to the match/mismatch hy p o t h e s i s (Cushing 1974), l a r v a l survival'may be improved i f the onset of feeding i s timed to match pr o d u c t i o n of t h e i r prey. The s t r e n g t h of the subsequent recruitment then depends on the degree of o v e r l a p . P r e d i c t i o n of the temporal and s p a t i a l p a t t e r n of plankton blooms on the northern s h e l f may a i d s t u d i e s of recruitment f l u c t u a t i o n s of north coast f i s h e r i e s , and p r o v i d e a b a s i s f o r timing the r e l e a s e of h a t c h e r y - r e a r e d salmonids. The p a t t e r n of blooms may a l s o e x p l a i n breeding success and p o p u l a t i o n 6 f l u c t u a t i o n s of p l a n k t i v o r o u s sea b i r d s (e.g. Vermeer 1981). P r e d i c t i o n of such blooms can take two approaches. One i s s t r i c t l y o b s e r v a t i o n a l , where the timing and l o c a t i o n of blooms i s observed over s e v e r a l years, while the other i s m e c h a n i s t i c , with p r e d i c t i o n s based on some theory of t h e i r u n d e r l y i n g causes. The best approach i s a combination of these methods, where p r e d i c t i o n s from mechanistic models are compared with o b s e r v a t i o n s . The northern B.C. s h e l f p r o v i d e s an o p p o r t u n i t y f o r the comparison of c u r r e n t p h y s i c a l models of seasonal plankton blooms and new o b s e r v a t i o n s in the f i e l d . Of p a r t i c u l a r importance i s the wide v a r i a t i o n of bathymetry in the area, which may produce d i f f e r e n c e s i n t i d a l v e l o c i t i e s a c r o s s the bottom thus generating mixed and s t r a t i f i e d water masses, with t h e i r c h a r a c t e r i s t i c blooms of plankton (e.g. Pingree 1978). In s p r i n g , such v a r i a t i o n s of bathymetry may a l s o i n f l u e n c e the p a t t e r n of the s p r i n g bloom, which can be d e s c r i b e d by the Sverdrup (1953) c r i t i c a l depth model. The occurrence of adjacent mixed and s t r a t i f i e d r egions suggests that f r o n t s may be common f e a t u r e s of the r e g i o n . S t u d i e s of c i r c u l a t i o n p a t t e r n s about f r o n t s (Pingree et al. 1974) i n d i c a t e they are zones of convergence tending to accumulate buoyant s u r f a c e m a t e r i a l s . Thus f r o n t s on the northern s h e l f are l i k e l y to be c r i t i c a l s i t e s f o r i n t e r a c t i o n of the region's l i v i n g and n o n - l i v i n g r e s o u r c e s . As convergent zones, they may accumulate plankton, i n c l u d i n g f i s h l a r v a e , and so i n c r e a s e the l i k e l i h o o d of a match i n p r o d u c t i o n . However, 7 for the same reason they w i l l a l s o accumulate s u r f a c e p o l l u t a n t s such as hydrocarbons cr t r a c e metals (e.g. Sick et al . 1978). F r o n t a l zones have a l s o been shown to be regions of i n c r e a s e d i n s i t u p r o d u c t i o n r e s u l t i n g from these mixed and s t r a t i f i e d waters (see Chapter 5 for a b r i e f review). Thus, such regions on the northern s h e l f are l i k e l y to be important s i t e s of enhanced b i o l o g i c a l a c t i v i t y . 1. OBJECTIVES The general o b j e c t i v e s of t h i s study are as f o l l o w s : 1. To examine the s p a t i a l and temporal d i s t r i b u t i o n s of plankton blooms in the open waters of the B r i t i s h Columbia northern s h e l f , i n c l u d i n g the seaward p o r t i o n s of the adjacent f j o r d s and i s l a n d passages. Phytoplankton and zooplankton biomass f l u c t u a t i o n s and s p e c i e s composition, and changes i n n u t r i e n t c o n c e n t r a t i o n s , are i n c l u d e d . D i s t r i b u t i o n s and t i m i n g of blooms are compared w i t h i n and between regions of the northern s h e l f such as Queen C h a r l o t t e Sound, Hecate S t r a i t , and Dixon Entrance, as w e l l as with the t i m i n g of the s p r i n g bloom i n the S t r a i t of Georgia. T h i s p r o v i d e s the f i r s t l a r g e s c a l e s p a t i a l and seasonal i n v e s t i g a t i o n of plankton in B.C. c o a s t a l waters north of Vancouver I s l a n d . 2. To i n v e s t i g a t e p o t e n t i a l mechanisms ge n e r a t i n g blooms and r e g u l a t i n g the observed s p a t i a l and temporal p a t t e r n s of plankton on the B.C. northern s h e l f . The p r i n c i p a l mechanisms c o n s i d e r e d are the c r i t i c a l depth - mixed depth 8 model (Sverdrup 1953) f o r i n i t i a t i o n of s p r i n g blooms, and the shallow sea t i d a l f r o n t model (Pingree 1978) f o r the l o c a t i o n and development of plankton blooms d u r i n g summer. Co n f i r m a t i o n that these models apply to areas f o r which d i r e c t o b s e r v a t i o n s e x i s t suggests they may a l s o be used to p r e d i c t bloom dynamics f o r the inadequately sampled areas of the northern s h e l f . Each chapter d e s c r i b e s an independent s u b s e c t i o n of t h i s study, with i t s own s p e c i f i c o b j e c t i v e s and where necessary, i t s methodology. A guide to the contents of each chapter, and an o u t l i n e to the t h e s i s as a whole, i s presented below. 2. CHAPTER SYNOPSES Some in f o r m a t i o n i s a v a i l a b l e from previous s t u d i e s concerning the broad o u t l i n e of the p h y s i c a l oceanography of the northern s h e l f . Such inf o r m a t i o n i s o b v i o u s l y p e r t i n e n t to any c o n s i d e r a t i o n of p h y s i c a l mechanisms i n f l u e n c i n g the plankton dynamics. Chapter 2 presents a b r i e f review of these s t u d i e s i n c l u d i n g the physi o g r a p h i c c h a r a c t e r i s t i c s of the region as background to the r e s u l t s of the present study. To i n c r e a s e the s p a t i a l and temporal extent of sampling over such a vast area as the northern s h e l f , a commercial o i l tanker was used as a s h i p of o p p o r t u n i t y . Chapter 3 d e s c r i b e s t h i s s h i p of op p o r t u n i t y (SHOP) program, o u t l i n i n g i t s o r i g i n , . methods, and problems. I t serves as a c e n t r a l i z e d s e c t i o n summarizing methods used throughout the whole of t h i s study. 9 Methods s p e c i f i c to each chapter are d i s c u s s e d w i t h i n that chapter. Chapter 4 d e s c r i b e s the s p a t i a l and seasonal p a t t e r n s of plankton on the northern s h e l f . I t begins with a review of prev i o u s s t u d i e s of the region's b i o l o g i c a l oceanography, then presents a sy n o p t i c d e s c r i p t i o n of d i s t r i b u t i o n s of c h l o r o p h y l l a, n u t r i e n t s , and phytoplankton and zooplankton as determined by t h i s study. V a r i a b i l i t y w i t h i n and between regions of the northern s h e l f i s emphasized. The second c e n t r a l theme of Chapter 4 i s concerned with the tim i n g of the s p r i n g bloom, and the hypothesis that i t begins f i r s t i n southern waters and sweeps s e q u e n t i a l l y northwards with i n c r e a s i n g s o l a r r a d i a t i o n . The c r i t i c a l depth model i s used to p r e d i c t the bloom timi n g , which i s compared with f i e l d o b s e r v a t i o n s . As an example of the s p a t i a l v a r i a b i l i t y of b i o l o g i c a l c h a r a c t e r i s t i c s that can occur at smaller s c a l e s , the s p r i n g - summer p a t t e r n of blooms i n the c o a s t a l region of Queen C h a r l o t t e S t r a i t and Queen C h a r l o t t e Sound i s presented and i t s r e l a t i o n s h i p to outmigrations of j u v e n i l e salmonids d i s c u s s e d . To continue t h i s theme of c o n s i d e r a b l e s p a t i a l and temporal v a r i a b i l i t y w i t h i n each region of the northern s h e l f , Chapters 5 and 6 focus on Hecate S t r a i t and examine i t s seasonal plankton d i s t r i b u t i o n s and o r g a n i z i n g mechanisms. The hypothesis examined in Chapter 5 i s that d i s t r i b u t i o n s of plankton a c r o s s Hecate S t r a i t i n summer are organized by, and p r e d i c t a b l e from, v a r i a t i o n s i n the i n t e n s i t y of v e r t i c a l mixing. I t i s proposed 10 that such v a r i a t i o n s of v e r t i c a l mixing r e s u l t from the i n t e r a c t i o n of t i d a l streaming and bathymetry. In Chapter 6, mechanisms a f f e c t i n g plankton d i s t r i b u t i o n s and i n f l u e n c i n g taxonomic composition a c r o s s Hecate S t r a i t i n winter and s p r i n g are examined. Such mechanisms i n c l u d e t i d a l mixing and the c r i t i c a l depth model, and the i n f l u e n c e of bathymetry. In both these chapters the s i g n i f i c a n c e of the observed plankton d i s t r i b u t i o n s to f i s h and f i s h e r i e s i s d i s c u s s e d . The f i n a l chapter presents a summary and general c o n c l u s i o n s of t h i s study. I t summarizes the p r i n c i p a l r e s u l t s of each chapter, and p r e d i c t s temporal p a t t e r n s of blooms for areas of the northern s h e l f not sampled by t h i s program. I t a l s o i n c l u d e s a d i s c u s s i o n of the new hypotheses and unanswered q u e s t i o n s generated i n t h i s study that would be f r u i t f u l f o r f u r t h e r r e s e a r c h . I I . PHYSICAL OCEANOGRAPHY OF THE NORTHERN SHELF: A BRIEF REVIEW 1. INTRODUCTION T h i s chapter serves as a b r i e f review of the geography and p h y s i c a l oceanography of the B r i t i s h Columbia northern s h e l f r e g i o n , p r o v i d i n g necessary background fo r subsequent chapters concerned with i t s b i o l o g i c a l oceanography. A program of p h y s i c a l measurements in the region began in 1934 and was most i n t e n s i v e d u r i n g the 1950's and 1960's. These data have been summarized and b r i e f l y i n t e r p r e t e d by Dodimead (1980). Crean (1967) has d e s c r i b e d s t u d i e s i n Dixon Entrance, while the general oceanography of the B.C. coast i n c l u d i n g the northern s h e l f has been reviewed by Thomson (1981). The f o l l o w i n g i s taken from Thomson (1981), except as noted. 2. PHYSIOGRAPHY The physiography and bathymetry of the B.C. northern s h e l f i s shown in F i g . 1. The region i s c h a r a c t e r i z e d by a h i g h l y indented, g l a c i a l l y fashioned s h o r e l i n e of i s l a n d s , shoals and f j o r d s which cont i n u e s below sea l e v e l . The only lowland c o a s t a l p l a i n i s on northeast Graham I s l a n d , which extends i n t o western Hecate S t r a i t to give that region i t s dominant p h y s i c a l c h a r a c t e r i s t i c . With depths l e s s than 20 m, t h i s s i d e of Hecate S t r a i t i s the s h a l l o w e s t , most r e g u l a r channel of the north c o a s t . The e a s t e r n s i d e of Hecate S t r a i t i s much deeper, with the dominant f e a t u r e being a trough running p a r a l l e l to the 1 1 FIG. 1. G e n e r a l i z e d map of the B . C . northern s h e l f study area showing l o c a t i o n s of p l a c e names r e f e r r e d to i n the t e x t . Bathymetric contours are in meters. 1 3 coast from Queen C h a r l o t t e Sound to Dixon Entrance and s h o a l i n g from 300 m at the c o n t i n e n t a l s h e l f to s l i g h t l y <100 m at i t s northern end. Two other troughs of 300-400 m extend from the c o n t i n e n t a l s h e l f edge eastwards. Both are i n c e n t r a l Queen C h a r l o t t e Sound, with the southern trough branching i n t o Queen C h a r l o t t e S t r a i t . Between these two troughs i s a shallow bank c a l l e d the Goose I s l a n d Bank, and between the southern spur and Vancouver I s l a n d i s another shoal c a l l e d Cook Bank. The slopes of both these banks are favoured s i t e s f o r g r o u n d f i s h f i s h e r i e s (Thomson 1981). In the north, a 400 m deep channel runs east-west forming the main b a s i n of Dixon Entrance, with another spur i n t o Clarence S t r a i t w i t h i n the Alaskan a r c h i p e l a g o . 3. WINDS As with the whole of the B.C. coa s t , winds i n the northern s h e l f r e g i o n are dominated by the seasonal pressure systems, the A l e u t i a n low i n winter and the North P a c i f i c high i n summer. Winds g e n e r a l l y blow p a r a l l e l to the coast c h a n n e l l e d by the topography, with an east-west v e l o c i t y g r a d i e n t that i s lower near the mainland shore. In summer, l i g h t winds (5 m s" 1) predominate, g e n e r a l l y from the west in Dixon Entrance and the northwest i n Queen C h a r l o t t e Sound. By October, the A l e u t i a n low dominates, with i n c r e a s e d storm a c t i v i t y and stronger s o u t h e a s t e r l y winds. Gale f o r c e winds (>17 m s" 1) occur over 10% of the time d u r i n g the 1 4 p e r i o d November to February and, combined with the shallow bottom in p a r t s of Queen C h a r l o t t e Sound and Hecate S t r a i t , can produce very l a r g e waves and rough seas. When winter c o n d i t i o n s are such that an i n l a n d high pressure and c o a s t a l low pressure system occur, very strong winds (>25 m s~ 1) can blow through c o a s t a l i n l e t s onto open water. 4. TIDES Tid e s on the northern s h e l f are of the mixed s e m i - d i u r n a l type s i m i l a r to those i n the S t r a i t of Georgia. T i d a l range v a r i e s with l o c a t i o n , with shallower areas having g r e a t e r amplitudes, f o r example 2-3 m i n Hecate S t r a i t . The f l o o d t i d e g e n e r a l l y propagates north along the west coast of Vancouver I s l a n d , then branches i n t o Queen C h a r l o t t e Sound and up Hecate S t r a i t . Another branch flows i n t o Dixon Entrance and south i n t o Hecate S t r a i t . These northward- and southward-propagating t i d e s meet in Hecate S t r a i t where they can cause l a r g e t i d a l ranges (up to 7 m i n Skidegate I n l e t on the Queen C h a r l o t t e I s l a n d s ) . 5. CIRCULATION C i r c u l a t i o n p a t t e r n s on the northern s h e l f are dominated by the s e m i - d i u r n a l t i d a l streams but are o f t e n m o d i f i e d e x t e n s i v e l y by wind, r u n o f f , bathymetry and s h o r e l i n e f e a t u r e s . In Queen C h a r l o t t e Sound, t i d a l streams are c l o c k w i s e r o t a r y with f l o o d to the northeast and ebb to the southwest. In Hecate S t r a i t , t i d a l streams are r e c t i l i n e a r due to the bathymetry, 1 5 with f l o o d to the north and ebb to the south. In Dixon Entrance the f l o o d c u r r e n t i s stronger on the south s i d e and ebb stronger on the n o r t h - s i d e due to the northward moving t i d e i n Hecate S t r a i t . T h i s sets up a cou n t e r c l o c k w i s e gyre i n Dixon Entrance centered northwest of Rose S p i t . N o n - t i d a l c u r r e n t s are predominantly caused by winds and runoff whose maximum e f f e c t s are seen in d i f f e r e n t seasons. In winter a northward s u r f a c e c u r r e n t i s set up i n Queen C h a r l o t t e Sound and Hecate S t r a i t by strong southeast winds and a c o a s t a l pressure g r a d i e n t c r e a t e d by onshore Ekman t r a n s p o r t . It can have speeds up to 3% of the wind speed averaged over the previous s e v e r a l days. In summer the s i t u a t i o n i s reversed, with weak northwest winds c a u s i n g o f f s h o r e Ekman t r a n s p o r t and a weak southward c o a s t a l c u r r e n t . Runoff e f f e c t s dominate in s p r i n g and e a r l y summer. They are most c l e a r l y seen i n Chatham Sound and Dixon Entrance, fed by the s i g n i f i c a n t s p r i n g d i s c h a r g e s of the Nass and Skeena R i v e r s which both peak i n June. The flow i s northwest i n t o Clarence S t r a i t and west along the northern s i d e of Dixon Entrance, c r e a t i n g an e s t u a r i n e - t y p e s i t u a t i o n with b r a c k i s h water moving seaward and a weak compensating r e t u r n flow at depth. In other seas of the northern s h e l f , s i g n i f i c a n t runoff i s l i m i t e d to the v i c i n i t y of the mainland shore. 16 6. TEMPERATURE AND SALINITY Dodimead (1980) has summarized temperature and s a l i n i t y data from the northern s h e l f . He found the seasonal v a r i a t i o n followed the r a d i a t i o n and freshwater input, with an annual range of s a l i n i t y from 28~32% 0 and an east-west g r a d i e n t with higher s a l i n i t i e s at the western seaward edge. Temperature v a r i e d from an A p r i l minimum about 6°C to a summmer maximum about 14°C, with Dixon Entrance c o l d e r than regions to the south. Since the 1940's, s i x l i g h t h o u s e s t a t i o n s i n the region have c o l l e c t e d d a i l y temperature and s a l i n i t y samples. Although these samples were from s u r f a c e near-shore waters, they do i l l u s t r a t e the l o c a l v a r i a b i l i t y on the northern s h e l f . Annual c y c l e s of temperature were s i m i l a r at a l l s t a t i o n s and t y p i c a l of c o a s t a l waters at these l a t i t u d e s . Annual ranges were l e s s at "o u t s i d e " s t a t i o n s (Langara I s l a n d and Cape S t . James) than " i n s i d e " ( T r i p l e I s l a n d , B o n i l l a I s l a n d , Mclnnes I s l a n d , Ivory I s l a n d ) . The p r i n c i p a l d i f f e r e n c e s were i n the annual s a l i n i t y v a r i a t i o n s , and P i c k a r d and McLeod (1953) i d e n t i f i e d three c l i m a t o l o g i c a l regions f o r the B.C. northern s h e l f : - no i n f l u e n c e of r i v e r r u n o f f , i . e . open ocean c o n d i t i o n s with l i t t l e annual v a r i a t i o n (Langara I s l a n d and Cape St. James); - s u r f a c e s a l i n i t y dominated by runoff from snow storage, with a s a l i n i t y minimum i n e a r l y summer ( T r i p l e I s l a n d and Ivory I s l a n d ) ; - s u r f a c e s a l i n i t y dominated from runoff due to l o c a l 1 7 p r e c i p i t a t i o n , with a minimum i n winter (Mclnnes I s l a n d and B o n i l l a I s l a n d ) . 7. SUBSURFACE CHARACTERISTICS Subsurface seasonal c h a r a c t e r i s t i c s are dominated by offshore/onshore Ekman t r a n s p o r t which deepens the h a l o c l i n e in winter and r a i s e s i t in summer (Dodimead 1980). In summer, the surface mixed l a y e r i s r e l a t i v e l y t h i n with strong g r a d i e n t s of temperature, s a l i n i t y , d e n s i t y and oxygen. Oxygen c o n c e n t r a t i o n s reach a minimum i n summer and may a f f e c t the depth m i g r a t i o n s of demersal f i s h (Dodimead 1980). In winter, i n c r e a s e d winds erode the thermocline and deepen the s u r f a c e mixed l a y e r , so that i t may be isothermal to 150 m (Dodimead 1980). I I I . GENERAL METHODS 1. INTRODUCTION T h i s study used a commercial v e s s e l as i t s p r i n c i p a l p l a t f o r m to examine the waters of the northern s h e l f . The background, l o g i s t i c s , sampling methodology, and problems with t h i s s h i p of oppo r t u n i t y (SHOP) program are d i s c u s s e d i n t h i s c hapter. A l l data c o l l e c t e d by t h i s study p l u s a b r i e f review of i t s methods have been p u b l i s h e d i n two r e p o r t s ( D i l k e el al. 1979, Perry et al. 1981) i n order to make them a v a i l a b l e to i n t e r e s t e d users as q u i c k l y as p o s s i b l e . They are t h e r e f o r e not in c l u d e d here as appendices, but are a v a i l a b l e from the Dept. of Oceanography, U n i v e r s i t y of B r i t i s h Columbia, Vancouver, B.C. A comparison of s h i p of o p p o r t u n i t y sampling procedures with those of standard r e s e a r c h v e s s e l s i s a l s o i n c l u d e d i n t h i s chapter. Programs u t i l i z i n g commercial v e s s e l s as ship s of op p o r t u n i t y to inc r e a s e s p a t i a l and temporal sampling over a given area are not new. The Continuous Plankton Recorder Survey (Glover 1967) has used merchant'ships to sample the plankton of the North A t l a n t i c and North Sea s i n c e 1930. V e s s e l s towed an automated sampler through the water, a v o i d i n g the n e c e s s i t y of t r a i n e d t e c h n i c i a n s to conduct the a c t u a l sampling procedure. The v a r i a b l e s measured were t h e r e f o r e taxonomic composition and biomass of zooplankton, with a q u a l i t a t i v e measure of phytoplankton abundance. Recently the towed instrument package has been m o d i f i e d to a l s o r e c o r d p h y s i c a l parameters and in vivo 18 19 f l u o r e s c e n c e i n an u n d u l a t i n g v e r t i c a l p a t t e r n (Aiken 1981). One e a r l y s h i p of o p p o r t u n i t y program using t e c h n i c i a n s to c o l l e c t samples, and t h e r e f o r e to conduct chemical and p r o d u c t i v i t y measurements, was run j o i n t l y by the U n i v e r s i t y of Washington, S e a t t l e , and the Canadian F i s h e r i e s Research Board in Nanaimo (Parsons and Anderson 1970, Anderson and Munson 1972). They used American M a i l L i n e s v e s s e l s o p e r a t i n g between S e a t t l e and Yokohama to examine p r o d u c t i o n processes in the North P a c i f i c and t e s t the v a l i d i t y of models p r e d i c t i n g the timing of s p r i n g plankton blooms. The program continued f o r f i v e years beginning i n 1968. Water samples were c o l l e c t e d from the engine room seawater system near the sea chest f o r c h l o r o p h y l l a, phosphate, s i l i c a t e and n i t r a t e c o n c e n t r a t i o n s , phytoplankton standing stock and s p e c i e s enumeration, and p a r t i c u l a t e n i t r o g e n a n a l y s i s (Anderson and Munson 1972). A d d i t i o n a l measurements in c l u d e d zooplankton composition and abundance, primary p r o d u c t i v i t y , v e r t i c a l temperature p r o f i l e s and i n s o l a t i o n . R e s u l t s from these commercial v e s s e l s were backed up by an i n t e n s i v e i n v e s t i g a t i o n with a res e a r c h s h i p (Parsons and Anderson 1970), and used to show seasonal d i f f e r e n c e s of primary pr o d u c t i o n and type of producer a c r o s s the study area. A long set of b i o l o g i c a l oceanographic time s e r i e s o b s e r v a t i o n s has been produced from the Ocean Weather S t a t i o n Papa (50°N, 145°W) sampling program. I t began i n August 1956 and continued with v a r y i n g degrees of i n t e n s i t y u n t i l the c a n c e l l a t i o n of the S t a t i o n "P" weather program i n 1981. In 20 a d d i t i o n , samples were a l s o taken along the t r a c k of the weathership (Line P) between V i c t o r i a , B.C., and S t a t i o n "P". Parameters measured over d i f f e r e n t p e r i o d s of time i n c l u d e p h y s i c a l data, pigments, n i t r a t e c o n c e n t r a t i o n s , primary p r o d u c t i v i t y , l i g h t a t t e n u a t i o n , zooplankton composition and biomass, and echo sounding o b s e r v a t i o n s . T h i s study d i f f e r e d from those p r e v i o u s l y d e s c r i b e d by having the a b i l i t y to sample c o n d i t i o n s at depth d i r e c t l y r a ther than v i a the s h i p ' s intake system, and so resembled programs of standard research v e s s e l s . The S t a t i o n "P" and AML s t u d i e s complement each other i n terms of o b j e c t i v e s , with S t a t i o n "P" p r o v i d i n g a temporal s e r i e s w i t h i n the s p a t i a l s e r i e s of the AML program. However, a l l these programs have con c e n t r a t e d on open oceanic waters while none have been concerned with r o u t i n e sampling of c o a s t a l r e g i o n s . Recently, other s t u d i e s have been i n i t i a t e d using commercial ships of o p p o r t u n i t y in c o a s t a l waters to measure both p h y s i c a l and b i o l o g i c a l parameters. A program s i m i l a r to that d e s c r i b e d here using an ocean-going tugboat has been conducted by SeaKem Oceanography L t d . (SeaKem Oceanography L t d . 1979) to monitor b i o l o g i c a l c o n d i t i o n s i n the southern S t r a i t of Georgia and o f f the west coast of Vancouver I s l a n d . Another study conducted by the U n i v e r s i t y of B r i t i s h Columbia used p r o v i n c i a l f e r r i e s running between Tsawassen and Swartz Bay to monitor the extent of the F r a s e r River plume (Royer and Emery 1982). On the Canadian east c o a s t , a one year study conducted by Dalhousie U n i v e r s i t y monitored the c e n t r a l 21 Gulf of Maine using f e r r i e s running between Yarmouth, N.S. and P o r t l a n d , Maine (Boyd 1984). However, a l l these s t u d i e s postdate the SHOP program d e s c r i b e d here, with the exception of the SeaKem program which was run s i m u l t a n e o u s l y . The remaining s e c t i o n s of t h i s chapter d e s c r i b e the background and methodology of the MV Imperial Tofino s h i p of o p p o r t u n i t y program. 2. BACKGROUND I n i t i a l p lanning f o r t h i s program began at a workshop he l d at the I n s t i t u t e of Ocean Scienc e s , Pat Bay, B.C. i n February 1977 e n t i t l e d P e l a g i c Ecosystem P r e d i c t i o n P r o j e c t ( B r i n k h u r s t 1977). I t i d e n t i f i e d a need f o r time s e r i e s of p h y s i c a l , chemical and b i o l o g i c a l data i n the c o a s t a l zone of the northeast P a c i f i c and suggested commercial s h i p s of o p p o r t u n i t y might be the only f e a s i b l e method to o b t a i n such data. Two areas were c o n s i d e r e d of p r i n c i p a l i n t e r e s t : the o i l t r a n s p o r t a t i o n c o r r i d o r a c r o s s the s u b a r c t i c P a c i f i c from Alaska to the U.S. west c o a s t ; and the west coast of Vancouver I s l a n d and Hecate Str a i t - Q u e e n C h a r l o t t e Sound. S e v e r a l v e s s e l s were c o n s i d e r e d f o r the p r o j e c t , with the u l t i m a t e choice being the MV Imperial Tofino, operated by Imperial O i l of Canada L t d . Funding fo r the p r o j e c t was awarded by the N a t u r a l Sciences and E n g i n e e r i n g Research C o u n c i l S t r a t e g i c Grant program (Grant No. G-0068) to Dr. T. R. Parsons. Imperial O i l of Canada made v a r i o u s m o d i f i c a t i o n s to t h e i r s h i p to f a c i l i t a t e sampling, and agreed to support the t e c h n i c i a n while on board to c o l l e c t samples. 22 3. VESSEL Owned and operated by Imperial O i l of Canada L t d . and r e g i s t e r e d i n Vancouver, B.C., the MV Imperial Tofino i s of a l l - s t e e l c o n s t r u c t i o n and was b u i l t i n 1973. She has a l e n g t h o v e r a l l of 50 m, a deadweight displacement of 1100 tonnes, and c a r r i e s a crew of 11. In design i t i s a tanker f o r l i q u i d cargoes, with the s u p e r s t r u c t u r e occupying the a f t t h i r d of the v e s s e l . I t operates a l l year d e l i v e r i n g kerosene and other f u e l o i l s to v a r i o u s towns, settl e m e n t s , and f i s h i n g camps along the B.C. c o a s t . S e v e r a l m o d i f i c a t i o n s were made by Imperial O i l to f a c i l i t a t e sampling. These i n c l u d e d access to the engine room seawater intake system to pump water d i r e c t l y f o r sampling, and the mounting of a winch and r o t a t i n g d a v i t on the s t e r n to permit sampling f o r zooplankton. The h y d r a u l i c winch s u p p l i e d up to 115 kg of l i n e p u l l with a drum c a p a c i t y of 350 m of 0.8 cm diameter hydrographic wire. 4. LOGISTICS Choice of the Imperial Tofino as the s h i p of o p p o r t u n i t y n a t u r a l l y c o n s t r a i n e d the study area to the normal o p e r a t i o n of the v e s s e l on i t s d e l i v e r i e s . T y p i c a l c r u i s e t r a c k s are shown i n F i g . 2, while l o c a t i o n s of a l l s t a t i o n s occupied are presented in Appendix I. I t should be noted the usual route north to P r i n c e Rupert followed the s h e l t e r e d waters of the " I n s i d e Passage", i . e . the S t r a i t of Georgia, Queen C h a r l o t t e S t r a i t , 23 F i g . 2. O u t l i n e of the p o s s i b l e routes of the Imperial Tofino on t r i p s to the northern s h e l f . Not a l l routes were followed on every c r u i s e . 24 F i t z Hugh and Milbanke Sounds (see F i g . 9 f o r l o c a t i o n s ) , and P r i n c e s s Royal and G r e n v i l l e Channels, f o l l o w e d by a run across Hecate S t r a i t from P r i n c e Rupert to Sandspit. C r u i s e s were t y p i c a l l y 2-3 weeks long and scheduled approximately monthly, being most i n t e n s i v e d u r i n g s p r i n g and summer. Thus the i n t e n t was to have monthly coverage dur i n g the bloom p e r i o d s over as wide an area of the northern s h e l f as p o s s i b l e . Two t e c h n i c i a n s were h i r e d to c o l l e c t and process the samples from the commercial v e s s e l phase of the p r o j e c t . S t a t i o n e d at the I n s t i t u t e of Ocean S c i e n c e s , Pat Bay, B.C., they would determine from Imperial O i l the schedule f o r each northern t r i p of the Tofino, and arrange to l o a d equipment and board at i t s base in Port Moody, B.C. Sampling was then conducted i n i t i a l l y as f r e q u e n t l y and i n as many d i f f e r e n t l o c a t i o n s as p o s s i b l e . However i t was q u i c k l y r e a l i z e d t h i s produced an enormous number of samples to a n a l y s e , e s p e c i a l l y with the monthly frequency of c r u i s e s . Consequently, upon c o n s i d e r a t i o n of the data from the f i r s t year of the p r o j e c t i t was decided sampling should concentrate on the open waters of the north c o a s t , and waters which were t r a v e r s e d c o n s i s t e n t l y on each northern t r i p of the Tofino. These i n c l u d e d Queen C h a r l o t t e S t r a i t , F i t z Hugh and Milbanke Sounds, Hecate S t r a i t and Dixon Entrance. T h i s p o l i c y was a p p l i e d to a l l c r u i s e s a f t e r C r u i s e 7 (January 1979). Table I l i s t s the dates of a l l the Tofino SHOP c r u i s e s to the northern s h e l f . 25 TABLE I . MV Imperial Tofino c r u i s e numbers, d a t e s , and number of s t a t i o n s s a m p l e d f o r t h e d u r a t i o n of t h e s h i p of o p p o r t u n i t y p r o g r a m . NUMBER DATE NUMBER OF STATIONS 01 13-20 March 1978 7 03 24 J u l y - 3 Au g u s t 1978 22 04 12-27 August 1978 37 05 1 1-27 September 1978 24 06 18-26 O c t o b e r 1978 22 07 2-7 J a n u a r y 1979 9 08 30 March - 8 A p r i l 1979 19 09 8-17 May 1979 21 10 9 June - 1 J u l y 1979 23 1 1 13-19 J u l y 1979 23 1 2 30 J a n u a r y - 9 F e b r u a r y 1980 38 13 10-17 A p r i l 1980 37 1 4 30 May - 7 June 1980 35 1 5 21 A u g u s t - 5 September 1 980 33 5. SAMPLE COLLECTION By d e f i n i t i o n , t h e p r i m a r y c o n c e r n s of a v e s s e l u s e d i n a s h i p of o p p o r t u n i t y program a r e i t s c o m m e r c i a l r e s p o n s i b i l i t i e s and s c h e d u l i n g ; t h e r e f o r e , any s a m p l i n g s h o u l d i n t e r f e r e w i t h r o u t i n e o p e r a t i o n s as l i t t l e as p o s s i b l e . In t h i s p r o g r a m , s a m p l i n g was done w h i l e t h e v e s s e l was underway between c o a s t a l d e l i v e r i e s , a l t h o u g h w i t h t h e c o o p e r a t i o n of t h e crew i t was s l o w e d t o a b o u t 2.5 m s ~ 1 (5 k n o t s ) f o r t h e d u r a t i o n o f t h e sample c o l l e c t i o n . At e a c h s t a t i o n t h e p o s i t i o n a nd t i m e was r e c o r d e d i n t h e b r i d g e l o g by t h e Duty O f f i c e r . Water samples f o r p h y t o p l a n k t o n e n u m e r a t i o n s and p i g m e n t s , s a l i n i t y , and n u t r i e n t s were drawn from t h e Tofino' s e n g i n e room 26 seawater intake system. The intake i s l o c a t e d amidship at a nominal depth of 3 m below the sea sur f a c e depending on b a l l a s t . At each s t a t i o n the sample volume (about 1.5 1) was pumped from the seachest by a Jabsco® i m p e l l e r pump, and was i n t e g r a t e d over the l e n g t h of the zooplankton tow which occurred s i m u l t a n e o u s l y . T y p i c a l sampling was 10 minutes, during which the v e s s e l t r a v e l l e d about 1.5 km. The seachest i s l o c a t e d adjacent to the intake and upstream of any engine room f i l t e r s or i n j e c t i o n s . I t s volume i s 0.34 m3, and with a maximum inflow of 0.091 m3 m i n - 1 the residen c e time of seawater i s about 3-4 minutes. Over the 10 minute sample c o l l e c t i o n p e r i o d there was l i t t l e c ontamination of samples from r e s i d u a l water i n the seachest. Samples were then t r e a t e d as d e s c r i b e d below and returned to the shore-based l a b o r a t o r y f o r a n a l y s i s . Due to lack of space on board the Tofino, the only sample treatments that c o u l d be performed immediately were f i l t r a t i o n and f r e e z i n g , as a p p l i c a b l e . 6. TEMPERATURE To a v o i d any contamination from the engine room environment, temperature was measured i n s u r f a c e c a s t s made from the deck of the v e s s e l i n s t e a d of through the seachest system. A modi f i e d bucket sampler was ca s t from the s h i p then brought on board and the temperature recorded. T h i s sampler was designed by Mr. Bruce D i l k e , and c o n s i s t e d of a 50 cm len g t h of 5 cm I.D. PVC pipe, c l o s e d at the bottom, with two 3 cm wide s l i t s along 27 the s i d e , a t t a c h e d to a l e n g t h of rope. Mounted i n s i d e t h i s tube, with i t s bulb extending i n t o the c l o s e d bottom end of the pipe, was a thermometer accurate to 0.1°C. Two styrofoam r i n g s a t t a c h e d about the o u t s i d e top and bottom of the sampler prevented damage a g a i n s t the sid e of the s h i p . An expendable bathythermograph (XBT) system was used at each s t a t i o n and o c c a s i o n a l l y between s t a t i o n s on c r u i s e s a f t e r C r u i s e 7 to o b t a i n p r o f i l e s of temperature a g a i n s t depth. This system c o n s i s t e d of a S i p p i c a n c h a r t r e c o r d e r , hand-held probe launcher, and type T6 probes (depth range to 460 m, S i p p i c a n Corp. 1971). XBT s u r f a c e temperatures were c a l i b r a t e d a g a i n s t s u r f a c e bucket thermometer readings f o r accuracy. 7. SALINITY From the seachest, 240 mL of sample was c o l l e c t e d i n 250 mL g l a s s b o t t l e s with p o l y e t h y l e n e - s e a l i n g screw caps. C o n d u c t i v i t y was determined ashore with an A u t o s a l salinometer ( G u i l d l i n e Instruments, model 8400), and s a l i n i t y c a l c u l a t e d from the c o n d u c t i v i t y measurements. 8. NUTRIENTS N u t r i e n t s were determined from water samples c o l l e c t e d from the seachest, with 125 mL f i l t e r e d immediately through Gelman type A/E g l a s s f i b e r f i l t e r s to remove p a r t i c u l a t e matter and the f i l t r a t e s t o r e d frozen i n p l a s t i c b o t t l e s . On shore, analyses f o r n i t r a t e p l u s n i t r i t e (N0 3+N0 2), phosphate (PO„) and 28 s i l i c a t e (SiO„) were c a r r i e d out using a Technicon® Auto Analyser as d e s c r i b e d i n S t r i c k l a n d and Parsons (1972) using standard c o l o u r i m e t r i c procedures. Lower l i m i t s of d e t e c t i o n were N0 3+N0 2: 0.10 MM; PO„ : 0.05 MM; SiO„: 0.10 juM. 9. PHYTOPLANKTON Samples fo r both enumeration and pigment a n a l y s i s were c o l l e c t e d from the s h i p ' s seachest. For enumeration, 240 mL was c o l l e c t e d and preserved with 10 drops of Lugol's s o l u t i o n i n a 250 mL screw-cap b o t t l e . On shore, enumeration followed Utermohl's (1958) method, with 10 mL or 100 mL of sample being s e t t l e d depending on the c e l l d e n s i t y . C e l l numbers were i d e n t i f i e d with an i n v e r t e d microscope at 250X for l a r g e r c e l l s and 1000X f o r small c e l l s . To f a c i l i t a t e the counting of l a r g e numbers of samples, c e l l s were i d e n t i f i e d to species where p o s s i b l e ( f o r l a r g e , d i s t i n c t l y i d e n t i f i a b l e c e l l s ) , or to genus and s i z e c a t e g o r y when more d e t a i l e d i d e n t i f i c a t i o n would be c o n s i d e r a b l y more time consuming. Analyses f o r c h l o r o p h y l l a and phaeopigments followed the in vitro f l u o r o m e t r i c method o u t l i n e d i n S t r i c k l a n d and Parsons (1972). Seawater from the seachest was c o l l e c t e d , and 200 mL f i l t e r e d through Whatman GF/C g l a s s f i b e r f i l t e r s (or e q u i v a l e n t ) with a t r a c e of MgC0 3 added. F i l t e r s were then frozen and returned to the l a b o r a t o r y onshore, where they were ground with a t i s s u e g r i n d e r i n 90% acetone, the residue removed by f i l t r a t i o n and the f l u o r e s c e n c e of the f i l t r a t e determined by 29 a Turner model 111 fluorometer. Phaeopigments were determined with the a d d i t i o n of two drops of 10% HCL to the f i l t r a t e and remeasurement of the f l u o r e s c e n c e ( S t r i c k l a n d and Parsons 1972). On C r u i s e 14 (June 1980) and C r u i s e 15 (August 1980) n e a r - s u r f a c e in vivo c h l o r o p h y l l f l u o r e s c e n c e was measured on t r a n s e c t s a c r o s s Hecate S t r a i t . Seawater was pumped c o n t i n u o u s l y from the seachest through a bubble t r a p to a Turner model 111 fluorometer f i t t e d with a flow-through door, with the ouput recorded on a s t r i p - c h a r t recorder (Lorenzen 1966). On C r u i s e 15, temperature was a l s o measured and recorded c o n t i n u o u s l y with a small t h e r m i s t o r set i n t o the flow to the fluorometer. Water samples were c o l l e c t e d at i n t e r v a l s to measure c h l o r o p h y l l a c o n c e n t r a t i o n s , although an i n s u f f i c i e n t number of samples were c o l l e c t e d on C r u i s e 15 to permit c o n v e r s i o n of f l u o r e s c e n c e to c h l o r o p h y l l . The flow r a t e to the fluorometer was about 2 L min" 1. There i s some u n c e r t a i n t y as to the e f f e c t of flow r a t e on measured in vivo f l u o r e s c e n c e , with some authors r e p o r t i n g no r e l a t i o n s h i p at flow r a t e s up to 2 L min" 1 (Setser 1980, quoted in Sweet and Guinasso 1984) while others have found a d i r e c t r e l a t i o n at flows between 0.5 and 1.5 L m i n - 1 (Sweet and Guinasso 1984). The l a t t e r i n v e s t i g a t o r s a l s o note the e f f e c t i s l i k e l y to vary c o n s i d e r a b l y with d i f f e r e n t phytoplankton communities. T h i s problem of f l u o r e s c e n c e response to v a r y i n g flew r a t e s was reduced in the present study by using a constant flow r a t e . 30 Mackas and Owen (1982) have examined continuous h o r i z o n t a l sampling systems and found that a system i n v o l v i n g a seachest can cause s u b s t a n t i a l b l u r r i n g of the input s i g n a l . T h i s means that f e a t u r e s with s p a t i a l s c a l e s l e s s than about 0.5 km, depending on the a c t u a l i n l e t c o n f i g u r a t i o n , cannot be r e s o l v e d . Such b l u r r i n g would not be a problem f o r the d i s c r e t e s t a t i o n s of t h i s study, where water samples were i n t e g r a t e d over the le n g t h of the simultaneous zooplankton tow, but may be a c o n s i d e r a t i o n f o r the continuous t r a n s e c t s . 10. ZOOPLANKTON On C r u i s e 1 (the "shakedown" c r u i s e ) , zooplankton were c o l l e c t e d from the seachest system f o l l o w i n g the water sample, and c o n c e n t r a t e d through a s e r i e s of nets. For a l l subsequent c r u i s e s however, a winch and r o t a t i n g d a v i t were i n s t a l l e d at the s t e r n to tow a high speed plankton sampler ( M i l l e r 1961). The sampler c o n s i s t e d of a 1 m long PVC pipe of 8 cm i n t e r n a l diameter, with 3 PVC f i n s a t t a c h e d to the back of the pipe f o r s t a b i l i t y and a net of 350 /nm mesh attached to the r e a r . A c a l i b r a t e d flow meter was i n s t a l l e d w i t h i n the f i r s t 20 cm of the pipe to measure the volume of water f i l t e r e d . Tows were g e n e r a l l y done at 2.5 m s" 1 (5 knots) f o r 10 minutes, with the depth of the sampler adj u s t e d to approximate that of the ship's seawater i n t a k e (3 m). Upon completion, the net was washed with seawater, the organisms poured i n t o 200 mL p l a s t i c or g l a s s j a r s , and preserved i n a 7% s o l u t i o n of sodium borate - b u f f e r e d 31 f o r m a l i n . Enumerat ion w i t h s t e r e o m i c r o s c o p e s was done on shore , w i t h i d e n t i f i c a t i o n of organisms f o l l o w i n g the same procedure as for p h y t o p l a n k t o n ( i . e . to s p e c i e s , or genus i f d e t a i l e d i d e n t i f i c a t i o n would prove e x c e s s i v e l y time consuming) . However, zoop lankton were not sampled from every s t a t i o n on each c r u i s e because of crew o b j e c t i o n s over the n o i s y o p e r a t i o n of the h y d r a u l i c w i n c h . 11. PROBLEMS Every s h i p of o p p o r t u n i t y program w i l l encounter d i f f i c u l t i e s , some i n h e r e n t i n the nature of such a program and o t h e r s s p e c i f i c to the v e s s e l and r e g i o n s sampled. One major d i f f i c u l t y wi th t h i s program i s i l l u s t r a t e d by F i g . 2. The T o f i n o has r a t h e r f l e x i b l e and widespread d e s t i n a t i o n s , and the a c t u a l route t r a v e l l e d on any t r i p to the n o r t h coas t would depend on the l o c a t i o n s of i t s d e l i v e r i e s . On one t r i p the T o f i no might t r a v e l a c r o s s the open waters of Queen C h a r l o t t e Sound, w h i l e on o t h e r s i t would f o l l o w the " I n s i d e Passage" . At i t s b e s t , s l i g h t v a r i a t i o n s of route meant not a l l s t a t i o n s c o u l d be r e p e t i t i v e l y sampled on c o n s e c u t i v e monthly c r u i s e s , w h i l e at i t s worst whole areas such as Dixon Ent rance or Queen C h a r l o t t e Sound might be m i s s e d . With sampling frequency a p p r o x i m a t e l y monthly there i s a c l o s e c o u p l i n g of temporal s c a l e s of sampl ing and the events under i n v e s t i g a t i o n , such tha t events c o u l d be missed w i t h these v a r i a t i o n s in r o u t e . T h i s problem was reduced somewhat a f t e r C r u i s e 7 ( January 1979) by 32 the change i n sampling p r o c e d u r e , which sampled more i n t e n s i v e l y those areas of i n t e r e s t covered on almost every c r u i s e . A second s p e c i f i c problem i s a l s o i l l u s t r a t e d by F i g . 2. The p r e f e r r e d route n o r t h was amongst the i s l a n d s and f j o r d s of the I n s i d e Passage. These are o b v i o u s l y r e s t r i c t e d c o a s t a l water s , w i t h h i g h l y v a r i a b l e c o n d i t i o n s i n f l u e n c e d by l o c a l or i s o l a t e d e v e n t s . T h i s has been shown by Dodimead (1980) in h i s review of l i g h t h o u s e temperature and s a l i n i t y data c o l l e c t e d at the seaward ends of these passages (reviewed in Chapter 2 ) . Thus , the r a t h e r l i m i t e d s c a l e s of coverage o f f e r e d by the Tofino were not a p p r o p r i a t e for m o n i t o r i n g the much s h o r t e r s p a t i a l and temporal events a l o n g the I n s i d e Passage . The m o d i f i e d sampl ing procedure a f t e r C r u i s e 7 reduced the coverage of these i n s i d e water s . The f requency of c r u i s e s d u r i n g s p r i n g and summer (monthly) was b a r e l y adequate for s t u d y i n g such proce s se s as bloom development , yet at t imes the number of samples and data produced c r e a t e d l a r g e b a c k l o g s . The most t ime-consuming a spec t s were the taxonomic i d e n t i f i c a t i o n s and enumera t ions ; development and implementat ion of automated procedures for t h e i r c o l l e c t i o n would be most u s e f u l . Attempts at automated r e c o r d i n g of biomass are be ing pursued (Mackas and Boyd 1979, Seakem Oceanography L t d . 1979). A f o u r t h d i f f i c u l t y , common to a l l SHOP-type programs, i s tha t most i n f o r m a t i o n ga ined d e a l s w i t h su r f ace or near su r f ace c o n d i t i o n s . Fea ture s important to s t u d i e s of bloom i n i t i a t i o n 33 and p r o d u c t i v i t y o f ten occur at d e p t h , such as the depth of the h a l o c l i n e and deep c h l o r o p h y l l maximum l a y e r s , which may not be adequate ly sampled by sur face s h i p of o p p o r t u n i t y t e c h n o l o g i e s . In the case of the American M a i l L i n e s program, t h i s d i f f i c u l t y was reduced by c o n c u r r e n t i n t e n s i v e s t u d i e s from a r e s e a r c h v e s s e l , which was ab le to sample the subsur face p r o p e r t i e s (Parsons and Anderson 1970). A s i m i l a r comparison was done in the present s t u d y , and i s d i s c u s s e d i n the next s e c t i o n . 12. COMPARISON OF SURFACE AND DEPTH SAMPLING In any r o u t i n e l a r g e - s c a l e survey of ocean ic a r e a s , the measurement of sur f ace p r o p e r t i e s w i l l be c o n t i n u o u s and l e s s t ime-consuming than v e r t i c a l p r o f i l e s at many d i s c r e t e s t a t i o n s . However, the problem of whether or not such near s u r f a c e measurements adequate ly repre sent c o n d i t i o n s at depth must be c o n s i d e r e d , e s p e c i a l l y i n areas where there may be s u b s t a n t i a l v e r t i c a l s t r a t i f i c a t i o n . Lorenzen (1970) examined t h i s q u e s t i o n , and e s t i m a t e d s t a t i s t i c a l r e l a t i o n s h i p s between s u r f a c e c h l o r o p h y l l a c o n c e n t r a t i o n s and the depth of the e u p h o t i c zone, t o t a l euphot i c zone c h l o r o p h y l l a and t o t a l pr imary p r o d u c t i v i t y for three low l a t i t u d e areas of the A t l a n t i c and P a c i f i c Oceans . He found a l l r e l a t i o n s h i p s were s t a t i s t i c a l l y s i g n i f i c a n t and suggested s u r f a c e c h l o r o p h y l l was a u s e f u l index of d e p t h - i n t e g r a t e d c h l o r o p h y l l and pr imary p r o d u c t i o n . R e c e n t l y , c o n s i d e r a b l e i n t e r e s t has focussed on t h i s q u e s t i o n due to i t s 34 r e l e v e n c e to s a t e l l i t e s t u d i e s of h o r i z o n t a l c h l o r o p h y l l d i s t r i b u t i o n s . The q u e s t i o n i s the same: how r e p r e s e n t a t i v e are remote ly- sensed near sur f ace c h l o r o p h y l l c o n c e n t r a t i o n s of d e p t h - i n t e g r a t e d c o n c e n t r a t i o n s ? Such s a t e l l i t e measurements do i n f ac t i n c l u d e some depth i n f o r m a t i o n depending on the a t t e n u a t i o n c o e f f i c i e n t , a l though t h i s o f t en r e p r e s e n t s o n l y 5% or l e s s of the t o t a l phytop l ankton biomass i n the water column ( P i a t t and Herman 1983). D e s p i t e such l i m i t a t i o n s , r emote ly- sensed n e a r - s u r f a c e c h l o r o p h y l l measurements have been shown to be u s e f u l i n d i c e s of the mean water column c h l o r o p h y l l c o n c e n t r a t i o n and even pr imary p r o d u c t i v i t y over wide r e g i o n s of the ocean (Smith 1981, Smith et al. 1982, P i a t t and Herman 1983). However, these s t u d i e s have been c r i t i c i z e d by Hayward and V e n r i c k (1982) on the b a s i s that they aggregated data from a wide v a r i e t y of a r e a s , and t h e r e f o r e r e f l e c t g l o b a l s c a l e o r g a n i z a t i o n (such as u p w e l l i n g c e n t e r s vs. o l i g o t r o p h i c gyres ) r a t h e r than l o c a l v a r i a t i o n s . T h e i r study examined the r e l a t i o n of sur face c h l o r o p h y l l to d e p t h - i n t e g r a t e d c h l o r o p h y l l and pr imary p r o d u c t i v i t y i n the C a l i f o r n i a C u r r e n t and the c e n t r a l Nor th P a c i f i c . In the C a l i f o r n i a C u r r e n t , s u r f a c e c h l o r o p h y l l was 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 both i n t e g r a t e d c h l o r o p h y l l and pr imary p r o d u c t i v i t y , a l t h o u g h there was c o n s i d e r a b l e s c a t t e r in the r e l a t i o n s h i p from s p a t i a l and temporal v a r i a t i o n s . In the c e n t r a l Nor th P a c i f i c , s u r f a c e c h l o r o p h y l l d i d not c o r r e l a t e w i t h i n t e g r a t e d c h l o r o p h y l l or pr imary 35 p r o d u c t i v i t y due to the low s u r f a c e c o n c e n t r a t i o n s and a deep maximum. They suggested s u r f a c e c h l o r o p h y l l would be a u s e f u l i n d i c a t o r of d e p t h - i n t e g r a t e d c o n c e n t r a t i o n s i n areas w i t h s t r o n g h o r i z o n t a l g r a d i e n t s and wide ranges of c o n c e n t r a t i o n s , but l e s s u s e f u l in homogeneous areas wi th marked v e r t i c a l g r a d i e n t s . The r e g i o n of the B . C . n o r t h e r n s h e l f i s l i k e l y to have h o r i z o n t a l g r a d i e n t s r e sembl ing those of the C a l i f o r n i a C u r r e n t , sugge s t ing sur f ace c h l o r o p h y l l shou ld be a u s e f u l index of mean v e r t i c a l c o n c e n t r a t i o n s . To t e s t t h i s , c h e m i c a l p r o p e r t i e s sampled by s h i p of o p p o r t u n i t y and s t andard r e s e a r c h v e s s e l methodolog ie s were compared for r e g i o n s of the n o r t h e r n B . C . s h e l f w i t h MV Pandora II (Dept . of Oceanography, U n i v e r s i t y of B . C . C r u i s e 80-7 , 28 A p r i l to 3 May 1980). Samples were c o l l e c t e d from the l a b o r a t o r y seawater supply ( o r i g i n a l l y drawn from the seachest i n t a k e ) as Pandora steamed acros s each s t a t i o n , to s i m u l a t e the sampl ing procedure f o l l o w e d by the Imperial Tofino. Pandora then r e t u r n e d on s t a t i o n and sampled p r o p e r t i e s at depth u s i n g s t andard h y d r o c a s t s to 2 , 3 , 5 , 1 0 and 20 m, w i t h bucket c a s t s p r o v i d i n g sur f ace water . The SHOP-method samples and those from the h y d r o c a s t s were then a n a l y s e d i n the same manner. Samples c o l l e c t e d u s i n g the s h i p of o p p o r t u n i t y t echn ique were compared w i t h those from the h y d r o c a s t s i n two ways. The seachest i n t a k e of Pandora i s at a depth of 4 m; t h e r e f o r e , these SHOP samples were compared w i t h the mean of the 3 and 5 m hydroca s t samples as a d i r e c t e s t i m a t i o n of the a b i l i t y of the 36 underway sampl ing t echnique to repre sent c o n d i t i o n s at i t s depth of i n t a k e . The SHOP samples were a l s o compared wi th s u r f a c e to 20 m i n t e g r a t e d va lues to t e s t t h e i r use as an index of upper l a y e r water column p r o p e r t i e s . Regre s s ion equa t ions for these two a n a l y s e s for c h l o r o p h y l l a and N0 3 +N0 2 are p re sen ted i n Tab le I I . These equa t ions i n d i c a t e very good agreement between underway samples and those from the h y d r o c a s t s , sugges t ing the t echn ique used by the Tofino r e p r e s e n t s near sur f ace p r o p e r t i e s q u i t e w e l l , and can ac t as an index for 0-20 m i n t e g r a t e d c o n c e n t r a t i o n s . I t should be noted these comparisons i n c l u d e d both s t r a t i f i e d and mixed water columns as i n d i c a t e d by F i g s . 14 and 15, a l t h o u g h in the case of the s t r a t i f i e d s t a t i o n s ( S t a t i o n s 7 and 22) the h i g h c h l o r o p h y l l r e g i o n o c c u r r e d i n near su r f ace waters r a t h e r than as a deep maximum. Two weeks p r i o r to the Pandora c r u i s e the Imperial Tofino had a l s o i n t e n s i v e l y sampled the c o a s t a l southeas t Queen C h a r l o t t e Sound a r e a , and i t i s i n t e r e s t i n g to compare the two r e s u l t s when d i s c u s s i n g the v a l i d i t y of the SHOP methodology. Only g e n e r a l p a t t e r n s w i l l be c o n s i d e r e d h e r e , whi le a more d e t a i l e d comparison of t h i s area i s p r e s e n t e d i n Chapter 4. The northbound l e g of Tofino C r u i s e 13 found low c h l o r o p h y l l and h i g h n u t r i e n t c o n c e n t r a t i o n s t y p i c a l of w i n te r in the Queen C h a r l o t t e Sound - F i t z Hugh Sound a r e a , w h i l e on i t s southbound l e g 5 days l a t e r h igher c h l o r o p h y l l and lower n u t r i e n t c o n c e n t r a t i o n s were recorded (data i n P e r r y et al . 1981). The p a t t e r n sampled by the Pandora i n t h i s area was the same as 37 TABLE I I . Regre s s ion equa t ions comparing near su r f ace (SHOP, 4 m) and depth sampled c h l o r o p h l y l l a and N0 3 +N0 2 c o n c e n t r a t i o n s c o l l e c t e d d u r i n g Pandora II c r u i s e 80-7 (28 A p r i l - 3 May 1980) to the B . C . n o r t h e r n s h e l f . CHLOROPHYLL i ) Y = SHOP c h l . (mg nr 3 ) X = 3-5 m mean c h l . (mg nr 3 ) Y = 0.22 + 0.73 X r 2 =0 .99 n=11 i i ) Y = SHOP c h l . (mg n r 3 ) X = 0-20 m i n t e g r a t e d c h l . (mg n r 2 ) Y = -0 .13 + 0.05 X r 2 = 0 . 9 l n=11 N0 3+N0 2 i ) Y=SHOP N0 3 +N0 2 (mmol n r 3 ) X=3-5 m mean N0 3 +N0 2 (mmol n r 3 ) Y = 0.92 + 0.94 X r 2 =0 .98 n=10 i i ) Y = SHOP N0 3+N0 2 (mmol n r 3 ) X = 0-20 m i n t e g r a t e d N0 3 +N0 2 (mmol n r 2 ) Y = -3 .14 + 0.06 X r 2 =0.88 n=9 Tofino' s southbound l e g , wi th the h i g h e s t n e a r - s u r f a c e c h l o r o p h y l l c o n c e n t r a t i o n s at the mouth of F i t z Hugh Sound. However, a b s o l u t e c o n c e n t r a t i o n s measured w i t h the SHOP-sampling procedure by Pandora were g rea te r than those from Tofino, which i s c o n s i s t e n t w i t h a bloom beg inn ing to deve lop d u r i n g the Tofino c r u i s e and c o n t i n u i n g d u r i n g the Pandora c r u i s e two weeks l a t e r . The n e c e s s i t y of c o l l e c t i n g zoop lankton from h i g h speed n e a r - s u r f a c e tows, and how r e p r e s e n t a t i v e these might be of c o n c e n t r a t i o n s and compos i t i ons at d e p t h , was a l s o examined. At s e l e c t e d s t a t i o n s on Pandora c r u i s e 80-7 a M i l l e r sampler 38 ( d e s c r i b e d above) was towed behind the s h i p i n the same manner as the Tofino sampling p r o c e d u r e . Once the s h i p had r e t u r n e d to the s t a t i o n and the h y d r o c a s t s were comple ted , a v e r t i c a l zoop lankton tow was made from near bottom to s u r f a c e u s i n g a SCOR net w i t h 202 nm mesh. R e s u l t s , wi th organisms i d e n t i f i e d to taxonomic group o n l y , are p r e s e n t e d i n Table III and suggest c o n s i d e r a b l e v a r i a b i l i t y between the two types of tows. In g e n e r a l i t appears the n e a r - s u r f a c e h o r i z o n t a l tows sample d i f f e r e n t d i s t r i b u t i o n s than the v e r t i c a l tows. T h i s r e s u l t s in h i g h e r abundance e s t imate s and lower d i v e r s i t y than v e r t i c a l tows, depending on the a r e a . Such d i f f e r e n c e s are not s u r p r i s i n g c o n s i d e r i n g the depth s t r a t i f i c a t i o n of zoop lankton and the p r e f e r e n c e of many l a r g e r s p e c i e s for deep water . Thus , w h i l e the n e a r - s u r f a c e tows may not be r e p r e s e n t a t i v e of the d e t a i l e d zoop lankton c o m p o s i t i o n and abundance throughout the water column, they may i n d i c a t e the g e n e r a l s t r u c t u r e of the community, for example the r e l a t i v e importance of copepods , decapod l a r v a e , and b a r n a c l e n a u p l i i . 39 TABLE I I I . Comparison of zoop lankton taxonomic groups sampled by Pandora II u s i n g M i l l e r (MLR) and v e r t i c a l (VERT) net tows. Note v e r t i c a l tows used a SCOR net w i t h 202 jim mesh, h o r i z o n t a l tows used a M i l l e r sampler wi th 351 ym mesh. Taxonomic abundances expres sed as number m~ 3 of water f i l t e r e d . S t a t i o n 3 3 18 18 1 6 1 6 1 9 19 Lat ( ° N ) 49.7 53.2 54.2 50.8 Long ( °W) 124.7 1 28.8 1 30.7 1 27.8 Type of Tow VERT MLR VERT MLR VERT MLR VERT MLR Max Depth Cm) 300 3 1 50 3 1 00 3 150 3 Copepods (<2mm) 1 34.5 1417. 1 26.6 35.4 690. 1 63.4 124.3 128 Copepods (>2mm) 1 02.0 402. 3 2.9 - 36.2 0.7 94.6 2.3 Decapod l a r v a e 26.9 7140. 6 0.9 15.4 8.3 - 13.0 1 1 . Decapods 7^4 228. 6 0.1 1 .7 - - 1.9 Crab l a r v a e 26.0 - - - 58.4 2.2 -Chaetognaths 1 .9 27.4 1 .0 - 2.8 - 18.6 2.3 Pteropods 3.7 - - - 55.7 1 .4 -Barnac le n a u p l i i - - - - 39.0 25.9 -I V . BIOLOGICAL OCEANOGRAPHY OF THE NORTHERN SHELF: SEASONAL PATTERNS A . INTRODUCTION The b i o l o g i c a l oceanography of the B r i t i s h Columbia n o r t h e r n s h e l f has been p o o r l y s t u d i e d . E x p l o r a t o r y f i s h e r i e s i n v e s t i g a t i o n s and p o p u l a t i o n s t u d i e s u s i n g commercia l c a t c h s t a t i s t i c s ( e . g . Ketchen 1964, A r c h i b a l d et al. 1983) have been c o n d u c t e d , yet no i n f o r m a t i o n i s a v a i l a b l e c o n c e r n i n g the tempora l d i s t r i b u t i o n s of p l a n k t o n i n the open waters and mechanisms i n f l u e n c i n g t h e i r p r o d u c t i o n . T h i s chapter p r e s e n t s s y n o p t i c d e s c r i p t i o n s of the s p a t i a l and temporal d i s t r i b u t i o n s of the p l a n k t o n as determined from the Imperial Tofino s h i p of o p p o r t u n i t y program. The a b i l i t y of the Sverdrup (1953) c r i t i c a l depth - mixed depth model to p r e d i c t the p h y t o p l a n k t o n growing season i s examined by comparison w i t h the observed d i s t r i b u t i o n s . T h i s chapter has two main purpose s . The f i r s t i s to p re sen t a summary of b i o l o g i c a l data c o l l e c t e d from the s h i p of o p p o r t u n i t y program as the f i r s t g e n e r a l d e s c r i p t i o n for the n o r t h e r n s h e l f . The focus i s on the g e n e r a l s p a t i a l and tempora l p a t t e r n s of c h l o r o p h y l l a, n u t r i e n t s , p h y t o p l a n k t o n and zoop lankton taxonomic c o m p o s i t i o n and abundance, a l though v a r i a b i l i t y w i t h i n r e g i o n s w i l l a l s o be s t r e s s e d . As an example of t h i s w i t h i n - r e g i o n v a r i a b i l i t y , s p a t i a l and temporal 40 41 c h a r a c t e r i s t i c s of the p l a n k t o n of sou thea s te rn Queen C h a r l o t t e Sound and t h e i r p o t e n t i a l importance to s u r v i v a l of m i g r a t i n g salmon f r y w i l l be d i s c u s s e d . The second purpose of t h i s chapter i s to examine the h y p o t h e s i s that i n i t i a t i o n of the s p r i n g p h y t o p l a n k t o n bloom o c c u r s f i r s t in southern waters of the B . C . coas t such as the S t r a i t of G e o r g i a , then sweeps s e q u e n t i a l l y northward w i t h the s ea sona l i n c r e a s e of s o l a r r a d i a t i o n . Such a p a t t e r n shou ld be apparent from the p h y t o p l a n k t o n growing seasons p r e d i c t e d s e p a r a t e l y for each r e g i o n of the coas t by the c r i t i c a l depth model and in the t i m i n g of the onset of the bloom as observed by the f i e l d program. T h i s p r o g r e s s i v e n o r t h e r n p a t t e r n was i m p l i e d by Parsons (1965) from a c r i t i c a l depth model c a l c u l a t e d for southern and n o r t h e r n c o a s t a l waters ; however, no p h y t o p l a n k t o n data were pre sented to s u b s t a n t i a t e the p r e d i c t i o n . In a more d e t a i l e d s tudy of the e a s t e r n s u b a r c t i c P a c i f i c , Parsons et al. (1966) aga in c a l c u l a t e d c r i t i c a l depths and proposed a n o r t h w e s t e r l y advance of the s p r i n g bloom about the c o a s t a l r im of the G u l f of A l a s k a . T h i s p a t t e r n was supported by the d i s t r i b u t i o n of copepods d u r i n g A p r i l , sugge s t ing much of the pr imary p r o d u c t i o n was q u i c k l y t r a n s f e r r e d to secondary p r o d u c t i o n v i a g r a z i n g . S i m i l a r t i m i n g of the s p r i n g bloom ( A p r i l ) was found for Norwegian c o a s t a l waters by Braarud and Nygaard (1978) , a l though there was a l a g of t h r e e weeks between 6 2 ° and 6 9 ° N . 42 1. PREVIOUS STUDIES No b i o l o g i c a l measurements were recorded on the p h y s i c a l oceanographic c r u i s e s to the B . C . n o r t h e r n coas t d u r i n g the 1950's and 1960 ' s . One of the e a r l i e s t c r u i s e s to measure parameters of importance to p h y t o p l a n k t o n p r o d u c t i o n was i n June 1958 ( S t r i c k l a n d 1958a). I t measured n u t r i e n t and l i g h t a t t e n u a t i o n p r o p e r t i e s i n Hecate S t r a i t and the G u l f of A l a s k a , but no biomass measurements were r e p o r t e d . S i l i c a t e , n i t r a t e , and n i t r i t e c o n c e n t r a t i o n s were below d e t e c t i o n i n the r e l a t i v e l y sha l low water of western Hecate S t r a i t , and i t was conc luded p l a n t growth was n e a r l y ze ro or i n c r e a s i n g very s l o w l y f o l l o w i n g the c o l l a p s e of the s p r i n g bloom. A n t i a et al. (1962) r e p o r t on data c o l l e c t e d in Hecate S t r a i t d u r i n g J u l y 1962. They found n i t r a t e c o n c e n t r a t i o n s <2 uM at depths l e s s than 25 m, and about 11 uM at 50 m. C h l o r o p h y l l a c o n c e n t r a t i o n s i n southwestern Hecate S t r a i t were about 4 ug L ~ 1 between 5-30 m, w h i l e i n c e n t r a l Hecate S t r a i t they were <1 uq L " 1 between the sur f ace and 30 m. The Sverdrup (1953) c r i t i c a l depth model was used by Parsons (1965) to p r e d i c t the p h y t o p l a n k t o n growing season for three r e g i o n s of the B . C . c o a s t . T h i s model i s a t h e o r e t i c a l comparison of the depth of the s u r f a c e mixed l a y e r and the depth at which p h y t o p l a n k t o n p r o d u c t i o n and r e s p i r a t i o n for the water column are e q u a l ; i t 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 the next s e c t i o n . Parsons (1965) d e f i n e d the growing season for p h y t o p l a n k t o n i n Queen C h a r l o t t e Sound and Hecate S t r a i t as 43 A p r i l to October (on the b a s i s of c r i t i c a l and mixed depths c a l c u l a t e d for ad jacent ocean ic w a t e r s ) , w h i l e for the S t r a i t of Georg ia i t began in M a r c h - A p r i l , and not u n t i l May at S t a t i o n " P " i n the s u b a r c t i c P a c i f i c . No p h y t o p l a n k t o n biomass data were a v a i l a b l e for Parsons (1965) to v a l i d a t e h i s p r e d i c t i o n for the Queen C h a r l o t t e Sound-Hecate S t r a i t r e g i o n . Ins tead he used n u t r i e n t data to i n f e r the p a t t e r n of p h y t o p l a n k t o n growth. N i t r a t e c o n c e n t r a t i o n s were h i g h i n w i n t e r (20 MM), v a r i a b l e (5-15 MM) i n s p r i n g , p o s s i b l y i n d i c a t i n g l o c a l b i o l o g i c a l d e p l e t i o n , and <5 iM d u r i n g summer. No s p a t i a l a n a l y s e s of these data were a t t empted . In the mid 1970's , the f j o r d s and seaways ad jacent to Hecate S t r a i t were sampled as par t of the K i t i m a t o i l p i p e l i n e and t e r m i n a l p r o p o s a l ( K i t i m a t P ipe L i n e L t d . 1976). Douglas Channel and the i n l e t s l e a d i n g to K i t i m a t were of p r i n c i p a l i n t e r e s t , but samples were a l s o c o l l e c t e d from Browning Ent rance ad jacent to n o r t h e r n Hecate S t r a i t . In September 1976, p h y t o p l a n k t o n biomass i n Browning Ent rance was s l i g h t l y g r e a t e r than 2 mg C h i a m " 3 i n the upper 5 m of the water column, wi th a maximum i n pr imary p r o d u c t i v i t y of 3.47 mg C m" 3 h " 1 at 5 m d e p t h . Subsequent s t u d i e s of the hydrography of t h i s system (Macdonald 1983) suggest there can be c o n s i d e r a b l e exchange of water w i t h Hecate S t r a i t , but few b i o l o g i c a l measurements were t a k e n . Zooplankton on the n o r t h e r n s h e l f have been s t u d i e d i n s l i g h t l y g r e a t e r d e t a i l than p h y t o p l a n k t o n , c h i e f l y as a r e s u l t 44 of t h e i r d i r e c t importance to s a l m o n i d s . Types of zoop lankton o c c u r r i n g i n the reg ion and t h e i r r e l a t i v e importance to f i s h can be de termined from a n a l y s i s of stomach c o n t e n t s . LeBras seur (1966) r e p o r t s on a study of the stomach c o n t e n t s of c o m m e r c i a l l y caught sa lmonids from the nor thea s t P a c i f i c , i n c l u d i n g the nor thern s h e l f in a " c o a s t a l " domain. Amphipods, copepods , e u p h a u s i i d s and the p te ropod Limacina spp. o c c u r r e d most f r e q u e n t l y i n p i n k , sockeye and coho salmon w i t h i n t h i s domain. He suggested prey a v a i l a b i l i t y was more important to f e e d i n g than p r e f e r e n c e s for s p e c i f i c prey i t ems . Manzer (1969) examined stomach c o n t e n t s of j u v e n i l e salmon c o l l e c t e d d u r i n g summer 1955 from Chatham Sound and ad jacent water s . Most common i n the stomachs of j u v e n i l e p i n k s , chum, and sockeye were copepods and l a r v a c e a n s , f o l l o w e d by b a r n a c l e and decapod l a r v a e . Amphipods and e u p h a u s i i d s were a l s o p r e s e n t , but more abundant in the stomach c o n t e n t s of coho salmon. In c o n n e c t i o n wi th t h i s s tudy of j u v e n i l e salmon, p l a n k t o n samples were c o l l e c t e d i n Dixon E n t r a n c e and Chatham Sound i n the summer of 1955 (LeBras seur 1956). Large biomass volumes were recorded from western and southern Dixon E n t r a n c e , s m a l l volumes from n o r t h e r n and e a s t e r n Dixon E n t r a n c e . These d i f f e r e n c e s were a l s o r e f l e c t e d by the c o m p o s i t i o n , w i t h c r u s t a c e a n s (mostly copepods) i n the l a rge volume r e g i o n , and v a r i o u s organisms i n the s m a l l volume waters ( i . e . a n n e l i d s , c l a d o c e r a n s , j e l l y - f i s h e s ) . I t was c o n c l u d e d these v a r i a t i o n s r e f l e c t e d d i f f e r e n t water masses, w i t h the southern waters of ocean ic 45 o r i g i n and the n o r t h e r n waters of b r a c k i s h c o a s t a l o r i g i n . T h i s p a t t e r n agrees wi th the e s t u a r i n e out f low of Skeena R i v e r water toward the ocean ic P a c i f i c d e s c r i b e d in Chapter 2. Another s tudy of zoop lankton i n the Skeena R i v e r e s tuary was conducted i n response to the proposed deep-water por t development near P r i n c e Rupert (Hoos 1975). In August and October 1971, zoop lankton were dominated by c o p e p o d i t e s , w i t h l a r v a c e a n s and copepods such as Pseudocal anus and Acartia a l s o p r e s e n t . F u r t h e r sampling i n summer 1972 i n d i c a t e d c a l a n o i d copepods were most abundant, w i t h a l a r g e p r o p o r t i o n be ing n a u p l i i and c o p e p o d i t e s . A few s t u d i e s have examined s p e c i f i c groups of zoop lankton i n v a r i o u s p a r t s of the r e g i o n . They f i n d d i s t r i b u t i o n s can g e n e r a l l y be r e l a t e d to p h y s i c a l p r o p e r t i e s and water mass exchange. Lea (1955) examined chaetognath d i s t r i b u t i o n s a l o n g the B . C . coas t i n summer 1953 and i d e n t i f i e d four s p e c i e s , of which o n l y two o c c u r r e d w i t h any f r e q u e n c y . Sagitta elegans was most common, i t s presence r e p r e s e n t i n g mixed c o a s t a l water s , w h i l e Eukrohnia hamat a was a l s o f r e q u e n t l y i d e n t i f i e d from waters of the n o r t h e r n s h e l f open to ocean ic i n f l u e n c e . These two s p e c i e s o f t e n o c c u r r e d i n n e a r - s u r f a c e waters of the n o r t h e r n s h e l f , but not where temperatures were r e l a t i v e l y h i g h . In Dixon E n t r a n c e and Hecate S t r a i t no chaetognaths o c c u r r e d at s t a t i o n s where bottom temperatures were > 9 ° C . Cameron (1957) s t u d i e d the d i s t r i b u t i o n of copepods about the Queen C h a r l o t t e I s l a n d s a l s o d u r i n g summer 1953. She 46 i d e n t i f i e d 32 s p e c i e s of copepods in Dixon Ent rance and Hecate S t r a i t , and grouped them i n t o s u r f a c e , s u b s u r f a c e , and deep-water forms. She c o n c l u d e d that c u r r e n t s were p r i m a r i l y r e s p o n s i b l e for t h e i r d i s t r i b u t i o n , and that r e p r o d u c t i o n took p l a c e i n areas w i t h w e l l d e f i n e d temperature and s a l i n i t y c h a r a c t e r i s t i c s . Paracalanus parvus was a s s o c i a t e d wi th temperatures > 1 0 ° C n o r t h of Masset t I n l e t . Acartia clausii was common (>50 L~ 1 ) in Masset t I n l e t and northwest of Graham I s l a n d , w h i l e Centropages mcmurrichi (now Centropages abdomi nal i s; H a r r i s o n et al . 1983) was common i n Hecate S t r a i t . Gardner (1980, 1982a, 1982b) has d e s c r i b e d the occurrence of s e v e r a l groups of zoop lankton on the n o r t h e r n s h e l f and ad j acent waters from a s p r i n g and a f a l l c r u i s e i n 1977. He found d i s t r i b u t i o n s of three s p e c i e s of copepods and two s p e c i e s of chaetognaths supported p r e v i o u s l y d e f i n e d h y d r o g r a p h i c r e g i o n s a long the coas t (Gardner 1982a). A c t u a l p a t t e r n s of d i s t r i b u t i o n depended on p h y s i c a l t r a n s p o r t p roce s se s and v a r i a t i o n s of s p e c i e s t o l e r a n c e . The chaetognaths Sagitta elegans and Eukrohnia hamata were r e l a t i v e l y un i fo rm throughout the whole r e g i o n at d e n s i t i e s of 0 . 5 - 1 . 0 n r 3 . Eucalanus bungi i bungii and Calanus plumchrus (now Neocalanus plumchrus, H a r r i s o n el al. 1983) were l e s s common i n open waters than i n i n l e t s of the n o r t h coas t and both were more common i n a reas w i t h deep maximum d e p t h s , which i s c o n s i s t e n t w i t h t h e i r l i f e c y c l e as d e s c r i b e d fo r the S t r a i t of G e o r g i a by F u l t o n (1973) . Cal anus cristatus (now Neocalanus cristatus; H a r r i s o n et al. 1983) was 47 l e s s common i n the study a r e a , o c c u r r i n g at s t a t i o n s wi th d i r e c t access to open water i n A p r i l , but was r e l a t i v e l y r a r e by November. The pre sence , i n samples c o l l e c t e d from Queen C h a r l o t t e Sound and Hecate S t r a i t , of s e v e r a l n o r m a l l y s u b t r o p i c a l zoop lankton s p e c i e s l e d Gardner (1982b) to conc lude the r e g i o n may exper ience o c c a s i o n a l deep i n t r u s i o n s of P a c i f i c e q u a t o r i a l water . Only two s t u d i e s have c o n s i d e r e d the temporal d i s t r i b u t i o n of zoop lankton on the n o r t h e r n s h e l f . Parsons (1965) r e p o r t s tha t a s e r i e s of tows taken over four months i n s p r i n g and summer produced maximum q u a n t i t i e s of zoop lankton in May and minimum q u a n t i t i e s in March . F u l t o n et al. (1982) r e p o r t on zoop lankton c o l l e c t e d a long the B . C . coa s t on monthly c r u i s e s from January to A p r i l 1980 i n c o n n e c t i o n w i t h an i c h t h y o p l a n k t o n survey program. The whole water column was sampled, w i t h tows taken o b l i q u e l y from near bottom to s u r f a c e . Dur ing w i n t e r (January and F e b r u a r y ) , zoop lankton were abundant o n l y a l o n g the outer c o n t i n e n t a l s h e l f and the deep t rough of Dixon E n t r a n c e . Most common was Neocalanus plumchrus, a l t h o u g h chaetognaths were common at a s t a t i o n i n southern Hecate S t r a i t . In March , zoop lankton biomass had i n c r e a s e d throughout the n o r t h e r n s h e l f , except for s t a t i o n s on the sha l low banks of western Hecate S t r a i t . A g r a d i e n t of d e c r e a s i n g biomass was apparent moving eastward from the c o n t i n e n t a l s h e l f . The dominant organisms were N. plumchrus stage 4 and 5, a l tho ugh l a r g e c o n c e n t r a t i o n s of b a r n a c l e n a u p l i i 48 and Sagitta elegans were noted at v a r i o u s s t a t i o n s . By A p r i l , biomass i n the sha l low waters of Hecate S t r a i t and Queen C h a r l o t t e Sound had dec rea sed , w i t h c l o g g i n g of the nets by p h y t o p l a n k t o n noted at s e v e r a l s t a t i o n s . H i g h e s t biomass s t i l l o c c u r r e d over the edge of the c o n t i n e n t a l s h e l f . I t was apparent N. plumchrus overwin te red i n waters deeper than 500 m, wi th the t i m i n g of r e c r u i t m e n t and appearance i n sur f ace waters s i m i l a r to t h a t d e s c r i b e d for the S t r a i t of Georg i a ( F u l t o n 1973). B. METHODS In a d d i t i o n to the g e n e r a l methods d e s c r i b e d i n Chapter 3, the Sverdrup (1953) c r i t i c a l depth model was used to e s t imate the phytop l ankton growing season for each r e g i o n of the nor thern s h e l f . T h i s s e c t i o n d e s c r i b e s t h i s model , i t s a s sumptions and c a l c u l a t i o n s . 1. CRITICAL DEPTH MODEL The e f f e c t s of mix ing and water column t r a n s p a r e n c y on pr imary p r o d u c t i o n i n the sea were noted by M a r s h a l l and Orr (1930) . In an a n a l y s i s of the s p r i n g bloom i n a S c o t t i s h L o c h , they c o n c l u d e d that s t a b i l i t y of the water column p l a y e d an important r o l e i n the diatom i n c r e a s e . Gran and Braarud (1935) noted o p t i m a l c o n d i t i o n s of pr imary p r o d u c t i o n o c c u r r e d when p h o t o s y n t h e s i s exceeded r e s p i r a t i o n , and the g r e a t e r the p o p u l a t i o n w i t h i n the euphot i c zone , the g r e a t e r was i t s 49 i n c r e a s e . T h i s concept was extended by R i l e y (1942) who found the r e l a t i o n s h i p between p l a n k t o n and s t a b i l i t y ( c a l c u l a t e d as the d e n s i t y d i f f e r e n c e between the sur f ace and 50 m) on Georges Bank to be z e r o i n March , p o s i t i v e in A p r i l and nega t ive in May. He c o n c l u d e d t h a t , for cons tant euphot i c zone d e p t h , r a te 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 , the i n c r e a s e of phytop l ankton was i n v e r s e l y r e l a t e d to the depth of v e r t i c a l m i x i n g . Sverdrup (1953) formula ted these ideas i n t o an a n a l y t i c a l e x p r e s s i o n fo r the c r i t i c a l d e p t h , which was d e f i n e d as the depth at which pr imary p r o d u c t i o n equaled p h y t o p l a n k t o n r e s p i r a t i o n summed over the water column. A net i n c r e a s e i n p r o d u c t i o n w i l l occur i f the depth of mix ing i s l e s s than t h i s d e p t h , m a i n t a i n i n g the m a j o r i t y of the p o p u l a t i o n w i t h i n the net p r o d u c t i v e l a y e r . The e q u a t i o n proposed by Sverdrup (1953) was Z = ° - 2 T ° ( i - e k Z c r ) c r k I u e ' c where Z c r i s the c r i t i c a l depth (m), k the a t t e n u a t i o n c o e f f i c i e n t fo r the water co lumn, I the compensat ion l i g h t i n t e n s i t y (the i n t e n s i t y at which p r o d u c t i o n and r e s p i r a t i o n are equa l for a s i n g l e c e l l ) , and I 0 the incoming s o l a r r a d i a t i o n c o r r e c t e d for su r f ace r e f l e c t i o n (the f a c t o r 0.2 was added to c o r r e c t fo r the r a d i a t i o n absorbed i n the f i r s t meter of w a t e r ) . Parsons et al. (1984) recommend dropp ing the e x p o n e n t i a l term ( i n g e n e r a l i t i s l i t t l e d i f f e r e n t than 1) and u s i n g 0.5 i n 50 p l a c e of 0.2 as the c o r r e c t i o n f a c t o r to i n c l u d e the e f f e c t of the e n t i r e p h o t o s y n t h e t i c a l l y a c t i v e r a d i a t i o n spectrum. S e v e r a l assumptions are i n v o l v e d in t h i s model and are d i s c u s s e d by Sverdrup (1953); - there e x i s t s a w e l l mixed sur f ace l a y e r , - p l a n k t o n are d i s t r i b u t e d even ly w i t h i n t h i s l a y e r , - p r o d u c t i o n i s not n u t r i e n t l i m i t e d , - the a t t e n u a t i o n c o e f f i c i e n t i s cons tant w i t h i n t h i s l a y e r , - the p r o d u c t i o n of o r g a n i c matter i s p r o p o r t i o n a l to the amount of r a d i a t i o n , and - the compensat ion l i g h t i n t e n s i t y i s known for the p o p u l a t i o n under s t u d y . These assumptions are in g e n e r a l most l i k e l y to be met d u r i n g s p r i n g , and t h i s model has been most s u c c e s s f u l at p r e d i c t i n g the t i m i n g of the s p r i n g p h y t o p l a n k t o n bloom (Semina 1960; Parsons et al. 1966; K a i s e r and S c h u l t z 1978; S i n c l a i r el al. 1981). A c c o r d i n g to Legendre and Demers (1984) i t has become the c l a s s i c textbook e x p l a n a t i o n for i t s ou tbreak . 2. CALCULATION OF CRITICAL DEPTHS C r i t i c a l depths were c a l c u l a t e d s e p a r a t e l y for four r e g i o n s of the B . C . c o a s t , d e f i n e d as the S t r a i t of G e o r g i a ( L a t . > 4 9 ° N ) , Queen C h a r l o t t e S t r a i t and Sound ( 5 0 ° T 0 ' N <Lat. < 5 2 ° N ) , Hecate S t r a i t ( 5 2 ° N <Lat. < 5 4 ° 1 0 ' N ) and Dixon Ent rance ( L a t . > 5 4 ° 1 0 ' N ) . A t o t a l of 350 S e c c h i depth r e c o r d s c o l l e c t e d from 1954 to 1965 on the n o r t h e r n s h e l f , and 222 Secch i 51 measurements between 1958 and 1968 i n Georg ia S t r a i t were used to c a l c u l a t e a t t e n u a t i o n c o e f f i c i e n t s . 1 Monthly mean c r i t i c a l depths were e s t imated u s i n g the Sverdrup (1953) equa t ion as m o d i f i e d by Parsons et al . (1984); example c a l c u l a t i o n s are i n Appendix I I . I n c i d e n t s o l a r r a d i a t i o n was taken as the normal d a i l y s o l a r r a d i a t i o n for each month recorded at Sandsp i t ( for Hecate S t r a i t and Dixon E n t r a n c e ) , Cape S t . James (Queen C h a r l o t t e Sound) , and Nanaimo (the S t r a i t of G e o r g i a ) . These data are a v a i l a b l e i n the Monthly R a d i a t i o n Summary (Atmospheric Environment S e r v i c e , Environment Canada, Ot tawa) , and were c o n v e r t e d to J c m " 2 d " 1 , then c o r r e c t e d for sur face r e f l e c t i o n due to monthly sun angle u s i n g v a l u e s p re sen ted in Parsons et al . (1966) for the s u b a r c t i c P a c i f i c . A t t e n u a t i o n c o e f f i c i e n t s for p h o t o s y n t h e t i c a l l y a c t i v e r a d i a t i o n were c a l c u l a t e d from S e c c h i depth ( Z g ) data u s i n g k - l ^ 5 -' Z s (Walker 1980). The compensat ion l i g h t i n t e n s i t y (I ) was taken as 58 J c m " 2 d " 1 from work by Hobson (1981) on p h y t o p l a n k t o n p r o d u c t i o n i n Saanich I n l e t , B . C . T h i s va lue i s at the h i g h end 1 These data are a v a i l a b l e i n F i s h . Res . Board C a n . , MS Rep. S e r . (Oceanographic and L i m n o l o g i c a l ) Nos. 17, 29, 30, 36, 43, 47, 52, 58, 83, 91, 111, 113, 129, 138, 211, 915, 968. 52 of the range of compensation i n t e n s i t i e s de termined by Fa lkowsk i and Owens (1978) for Skeletonema cost atum, a common diatom in the r e g i o n d u r i n g s p r i n g and summer ( H a r r i s o n et at. 1983; t h i s s t u d y ) , but w e l l w i t h i n the f u l l range of i n t e n s i t i e s g iven for the s i x s p e c i e s of marine p h y t o p l a n k t o n examined by Fa lkowsk i and Owens (1978) . C r i t i c a l depths were c a l c u a t e d for each Secch i depth measurement, and monthly means and 95% c o n f i d e n c e l i m i t s c a l c u l a t e d u s i n g S t u d e n t ' s t d i s t r i b u t i o n to c o r r e c t for v a r i a b l e sample s i z e s as d e s c r i b e d by Sokal and R o h l f (1981) 95% Conf idence I n t e r v a l = t n c , , x - 7 ^ — 0 . 5 , (n-1 ) |/n where s i s the s tandard d e v i a t i o n and n the sample s i z e for that area and month. Note that v a r i a t i o n in monthly c r i t i c a l depth e s t imate s i s based on the v a r i a b i l i t y of a t t e n u a t i o n c o e f f i c i e n t s . The o t h e r important f e a t u r e of the c r i t i c a l depth model i s the depth of the sur face mixed l a y e r . V a r i a t i o n s i n the t h i c k n e s s of t h i s l a y e r have s e v e r a l components: a d i e l c y c l e due to dayt ime h e a t i n g and n i g h t t i m e c o o l i n g , a c l i m a t o l o g i c a l c y c l e based on the passage of a tmospher ic d i s t u r b a n c e s , and a s ea sona l c y c l e connected w i t h the annual p a t t e r n of s o l a r r a d i a t i o n . Woods and Onken (1982) have model led the e f f e c t of d i e l v a r i a t i o n s i n mixed l a y e r depth on p h y t o p l a n k t o n d i s t r i b u t i o n s . When the response of i n d i v i d u a l c e l l s s c a t t e r e d 53 throughout the euphot ic l a y e r are taken i n t o a c c o u n t , some p r o p o r t i o n of c e l l s w i l l be e n t r a i n e d i n t o the deepened mixed l a y e r every n i g h t . Dur ing daytime h e a t i n g however, the mixed l a y e r s h o a l s , l e a v i n g some of the c e l l s to s e t t l e deeper i n t o the water co lumn. Repeated s i m u l a t i o n s demonstrated that t h i s r e s u l t s i n a deep c h l o r o p h y l l maximum ju s t below the maximum depth of n i g h t t i m e m i x i n g . T h i s l a y e r , of c o u r s e , can then be mixed back i n t o the sur face l a y e r w i t h the passage of storms on the c l i m a t o l o g i c a l s c a l e . When t h i s model was run w i t h c o n d i t i o n s t y p i c a l of d i f f e r e n t seasons , i t d i d reproduce the g e n e r a l c h a r a c t e r i s t i c s of the s h o a l i n g sea sona l t h e r m o c l i n e o r i g i n a l l y used by Sverdrup (1953) . I have t h e r e f o r e d i s r e g a r d e d any p o t e n t i a l e f f e c t s of d i e l or c l i m a t o l o g i c a l v a r i a t i o n s i n mixed l a y e r d e p t h , p r i m a r i l y due to l a ck of a p p r o p r i a t e data for the n o r t h e r n s h e l f , and have c a l c u l a t e d t h i s l a y e r as monthly (=seasonal) compos i tes for the S t r a i t of G e o r g i a and the three r e g i o n s of the n o r t h e r n s h e l f d e f i n e d p r e v i o u s l y . D e n s i t y ve r su s depth data measured on the p h y s i c a l oceanographic c r u i s e s to the n o r t h e r n s h e l f from 1954 to 1971 ( a v a i l a b l e from the Mar ine E n v i r o n m e n t a l Data S e r v i c e , Dept . of F i s h e r i e s and Oceans , Ottawa; dates and c r u i s e i d e n t i f i c a t i o n s l i s t e d i n Appendix I I I ) and fo r the S t r a i t of Georg i a from a s e r i e s of monthly c r u i s e s from December 1967 to December 1968 (Crean and Ages 1971), were used i n the c a l c u l a t i o n s . For the S t r a i t of G e o r g i a ( L a t . > 4 9 ° N ) , 537 s t a t i o n s were used ( approx imate ly 43 per month) , 485 for Queen 54 C h a r l o t t e Sound, 369 for Hecate S t r a i t , and 562 for Dixon E n t r a n c e . At each s t a t i o n , the depth i n t e r v a l at which the g r a d i e n t (da f c /dZ) was a maximum was d e t e r m i n e d . I f t h i s maximum was g r e a t e r than 0.01 ofc u n i t s irr 1 , the mean of that depth i n t e r v a l was d e f i n e d as the depth of the sur face mixed l a y e r . I f the maximum was l e s s than t h i s v a l u e , then e i t h e r the maximum depth of the water or the depth of the 33.7% 0 i s o h a l i n e ( for the n o r t h e r n s h e l f ; the 30.5% o i s o h a l i n e for the S t r a i t of G e o r g i a ) , whichever was s h a l l o w e r , was d e f i n e d as the mixed d e p t h . The 33.7% 0 i s o h a l i n e has been d e f i n e d as the depth of the permanent h a l o c l i n e on the n o r t h e r n s h e l f (Dodimead and P i c k a r d 1967), and i t was assumed t h i s would repre sent the maximum p o t e n t i a l mixed depth i n the r e g i o n . Waldichuk (1957) has noted waters of the S t r a i t of Georg i a below the depth of the 30.5% o i s o h a l i n e tend to be homogeneous year round . The use of 0.01 o fc u n i t s m~ 1 to d e f i n e the p y c n o c l i n e i s based on a study of su r f ace l a y e r c h a r a c t e r i s t i c s i n the n o r t h P a c i f i c Ocean (Giovando and Robinson 1965). They d e f i n e d a t h e r m o c l i n e as a n e g a t i v e temperature g r a d i e n t g rea te r than 0 . 0 7 ° C m~ 1 . Assuming a cons tant s a l i n i t y , such a g r a d i e n t i s e q u i v a l e n t to a d e n s i t y g r a d i e n t of 0.01 a f c u n i t s m~ 1 ; the more u sua l s i t u a t i o n where s a l i n i t y i n c r e a s e s w i t h depth produces a s t r o n g e r d e n s i t y g r a d i e n t . As w i t h the c r i t i c a l depths , mixed l a y e r depths are p re sen ted as 95% c o n f i d e n c e i n t e r v a l s of monthly means for data p o o l e d over a l l year s u s i n g the above 55 equa t ion from Soka l and R o h l f (1981) . Much of the taxonomic data c o l l e c t e d in t h i s study are i n terms of abundance. In order to reduce the e f f e c t of s m a l l - s i z e d but numerous taxa when abundance e s t imate s are used ( e . g . f l a g e l l a t e s ve r su s d i a t o m s ) , a phytop lankton biomass index was c a l c u l a t e d by w e i g h t i n g abundances wi th a r e l a t i v e s i z e c o e f f i c i e n t (Mackas and Sef ton 1982). An example of the i d e n t i f i e d taxonomic groups , t h e i r r e l a t i v e s i z e c o e f f i c i e n t s , and mean abundances for c r u i s e s a c r o s s Hecate S t r a i t are g iven i n Tab le IX (Chapter 6 ) . Replacement of the r e l a t i v e s i z e c o e f f i c i e n t s w i t h e s t imated carbon per c e l l v a lue s for Saan ich I n l e t p o p u l a t i o n s (unpub l i shed data of the C o n t r o l l e d Ecosystems P o l l u t i o n Exper iment , a l s o C a r r u t h e r s 1981) produced no major changes i n the r e l a t i v e o r d e r i n g of biomass e s t i m a t e s . The r e l a t i v e s t a t e of the phytop l ankton bloom d u r i n g s p r i n g 1979 and 1980 between the major r e g i o n s of the coas t can be e s t imated u s i n g the q u a l i t a t i v e t echn ique of Braarud and Nygaard (1978). I t i n v o l v e s d e f i n i n g a priori m u l t i - p a r a m e t e r c a t e g o r i e s r e p r e s e n t i n g the r e l a t i v e s t a t e of the s p r i n g bloom, then a s s i g n i n g s t a t i o n s w i t h i n each area to the a p p r o p r i a t e c a t e g o r y . The d i f f i c u l t y , however, i s d e f i n i n g l i m i t s to these parameters r e p r e s e n t i n g bloom and non-bloom c o n d i t i o n s that are a p p l i c a b l e to a l l r e g i o n s of the s t u d y . Based on c h a r a c t e r i s t i c s of the w e l l - d e f i n e d s p r i n g bloom i n western Hecate S t r a i t i n A p r i l 1980 ( F i g . 6, and Chapter 6 ) , the f o l l o w i n g c a t e g o r i e s were used : I - p re-b loom : c h l a <1/ig L" 1 ; 56 <106 p h y t o p l a n k t o n c e l l s L - 1 ; N0 3 +N0 2 >8 MM II - e a r l y bloom : c h l a >5 ng L " 1 ; >106 c e l l s L" 1 ; N0 3 +N0 2 * 8 - l 0 MM III - l a t e bloom : c h l a >2 jug L" 1 ; >106 c e l l s L ~ 1 ; N0 3+N0 2 <8 MM IV - pos t -b loom : c h l a <2 ng L " 1 ; <106 c e l l s L ~ 1 ; N0 3+N0 2 <8 iM. I t has been assumed that s p r i n g blooms have i d e n t i c a l c h a r a c t e r i s t i c s throughout a l l r e g i o n s of the n o r t h e r n s h e l f , which can be d e f i n e d by the above c a t e g o r i e s . C. RESULTS 1. CRITICAL DEPTH MODEL The g e n e r a l annual p a t t e r n of c a l c u l a t e d c r i t i c a l depths i s s i m i l a r between the three r e g i o n s of the n o r t h e r n s h e l f , but d i f f e r e n t from that i n the S t r a i t of Georg i a ( F i g . 3 ) . On the n o r t h e r n s h e l f , c r i t i c a l depths i n c r e a s e d u r i n g s p r i n g , r e a c h i n g t h e i r deepest range i n May, then s h o a l to t h e i r minimum range i n December. However, annual mean c r i t i c a l depths d i f f e r e d between r e g i o n s d u r i n g the p e r i o d 1954 to 1971, be ing s h a l l o w e r i n Dixon Entrance (51 m; n=124, s tandard d e v i a t i o n ( s ) = 3 5 m) than i n e i t h e r Hecate S t r a i t (72 m; n=86, s=36 m) or Queen C h a r l o t t e Sound (67 m; n=132, s=34 m). The s p r i n g f r e s h e t from the Skeena R i v e r reaches i t s maximum d u r i n g June , and may add s i l t or o rgan ic m a t e r i a l to Dixon Ent rance d u r i n g the summer months, 57 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 2 0 - 1 I T T X 1 I 4 0 -6 0 -80 -100-JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 2 0 -60-8 0 -100-B FIGURE 3. C r i t i c a l depth ( s o l i d l i n e ) and mixed depth (dashed l i n e ) 95% c o n f i d e n c e i n t e r v a l s of the monthly means from 1954 to 1971 i n the S t r a i t of G e o r g i a (Lat > 4 9 ° N ; A ) , Queen C h a r l o t t e Sound (B) , Hecate S t r a i t ( C ) , and Dixon Ent rance (D) . See t ex t for e x p l a n a t i o n of c a l c u l a t i o n s . JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 20 4 0 60 BO-100-140 J i , I JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 20 4 0 -T X 60 H a. UJ a 8 0 -i i FIGURE 3 ( C o n t i n u e d ) . 59 d e c r e a s i n g the c r i t i c a l d e p t h . F i g . 3 i n d i c a t e s that c r i t i c a l depths i n Dixon Ent rance d u r i n g summer are indeed sha l lower than Hecate S t r a i t or Queen C h a r l o t t e Sound. In the c e n t r a l and n o r t h e r n s e c t i o n s of the S t r a i t of G e o r g i a , c r i t i c a l depths a l s o p r o g r e s s i v e l y deepen d u r i n g s p r i n g , r e a c h i n g a maximum in June , then shoa l to a minimum i n December. The annual mean depth i s 52 m (n=168, s=30 m), which i s s i m i l a r to that i n Dixon E n t r a n c e . The g e n e r a l annual p a t t e r n of mixed l a y e r depths i s a l s o c o n s i s t e n t on the n o r t h e r n s h e l f , but d i f f e r e n t from that of the S t r a i t of G e o r g i a ( F i g . 3 ) . On the n o r t h c o a s t , mixed depths are deepest i n l a t e win te r ( u s u a l l y March) r e f l e c t i n g the i n f l u e n c e of winter storms and c o o l i n g , decrease s h a r p l y i n A p r i l , and are sha l lowes t d u r i n g summer. In a s tudy of the heat budget of Dixon E n t r a n c e , Tabata (1958) noted March was a p e r i o d of no net t r a n s f e r to or from the water , where sea su r f ace temperatures were at t h e i r annual minimum. In the S t r a i t of G e o r g i a , mixed depths are c o n s i d e r a b l y s h a l l o w e r due to s t a b i l i z a t i o n by freshwater r u n o f f . Deepest ranges o c c u r r e d d u r i n g December and J anuary , w h i l e the r e s t of the year had r e l a t i v e l y l i t t l e v a r i a t i o n . There i s a r e d u c t i o n i n the l e n g t h of the p h y t o p l a n k t o n growing season , d e f i n e d as those months when the c r i t i c a l depth i s deeper than the mixed l a y e r d e p t h , w i t h i n c r e a s i n g l a t i t u d e a long the B . C . c o a s t . However, the p r o g r e s s i o n does not occur s e q u e n t i a l l y from the S t r a i t of G e o r g i a to Dixon E n t r a n c e . In 60 the S t r a i t of G e o r g i a , a net i n c r e a s e i s p r e d i c t e d from February to October ( F i g . 3A) , compared w i t h Parsons (1979) who p r e d i c t e d March to O c t o b e r , and the comment by H a r r i s o n el al . (1983) that p r o d u c t i o n may be l i g h t l i m i t e d from October to F e b r u a r y . The d i f f e r e n c e i n the p r e d i c t e d s t a r t of the bloom between that e s t i m a t e d by Parsons (1979) and that shown i n F i g . 3A may be due to ca lm weather c o n d i t i o n s d u r i n g s p r i n g 1968 when the data on which t h i s f i g u r e was based were c o l l e c t e d . However, i n a s ea sona l study of the maximum p h o t o s y n t h e t i c r a te of p h y t o p l a n k t o n in Saan ich I n l e t , Hobson (1981) c o n c l u d e d c r i t i c a l depths were always g r e a t e r than mixed dep ths , p r i n c i p a l l y due to s t a b i l i z a t i o n from f reshwater runof f and p r e c i p i t a t i o n . He suggested the diatom o u t b u r s t r e q u i r e d a t h r e s h o l d i r r a d i a n c e which o c c u r r e d i n March or A p r i l . I t i s apparent that areas wi th d i f f e r e n t h y d r o g r a p h i c c o n d i t i o n s may produce c r i t i c a l : m i x e d depth r a t i o s that d i f f e r from the mean p a t t e r n . In Queen C h a r l o t t e Sound ( F i g . 3B) , the p r e d i c t e d growing season i s May to September, a l t h o u g h i t may beg in i n A p r i l g iven c o n d i t i o n s of calm c l e a r weather . In Hecate S t r a i t , the p h y t o p l a n k t o n growing season i s p r e d i c t e d to occur from A p r i l to September ( F i g . 3C) , and for Dixon Entrance i t i s from May to August ( F i g . 3D). Parsons (1965) p r e d i c t e d f a v o u r a b l e c o n d i t i o n s fo r growth i n the Queen C h a r l o t t e Sound - Hecate S t r a i t r e g i o n from A p r i l or May to September, the same as the more d e t a i l e d a n a l y s i s of the pre sent s tudy . Such comparisons i n v o l v e mean c o n d i t i o n s however, and there i s l i k e l y to be c o n s i d e r a b l e 61 v a r i a b i l i t y of the s t a r t of the s p r i n g bloom w i t h i n each r e g i o n . 2. PHYSICAL PROPERTIES A b r i e f d e s c r i p t i o n of the temperature and s a l i n i t y data c o l l e c t e d on the s h i p of o p p o r t u n i t y c r u i s e s w i l l serve as background for the b i o l o g i c a l d a t a . The b a s i c annua l p a t t e r n was s i m i l a r between 1979 and 1980, and t y p i c a l of o ther temperate c o a s t a l water s . Dur ing w i n t e r , su r f ace temperature - s a l i n i t y p l o t s of n o r t h e r n s h e l f data ( e . g . C r u i s e 12, February 1980, F i g . 4A) i n d i c a t e r e l a t i v e l y homogeneous c o n d i t i o n s , yet each r e g i o n i s d i s t i n g u i s h a b l e . However, by summer ( e . g . C r u i s e 11, J u l y 1979, F i g . 4B) sur face temperatures and s a l i n i t y were much more v a r i a b l e . Stream flow data (Water Resources Branch 1977) show s p r i n g d i s c h a r g e s begin i n A p r i l and peak i n June , w i t h no d i f f e r e n c e i n monthly t i m i n g between r i v e r s emptying i n t o Queen C h a r l o t t e S t r a i t i n the south and Dixon Entrance i n the n o r t h . The magnitude and t i m i n g of the annual c y c l e of temperature was s i m i l a r between the three r e g i o n s of the n o r t h e r n s h e l f , but d i f f e r e n t from the S t r a i t of G e o r g i a where the s ea sona l i n c r e a s e o c c u r r e d e a r l i e r . Data from Hecate S t r a i t (as r e p r e s e n t a t i v e of the n o r t h e r n s h e l f ) and the S t r a i t of Georg i a p o o l e d from August 1978 to J u l y 1979 were compared w i t h a t - t e s t (u s ing the SPSS s t a t i s t i c a l package, Nie et al . 1975). Mean temperature and s a l i n i t y were s i g n i f i c a n t l y d i f f e r e n t between the two r e g i o n s at the 95% p r o b a b i l i t y l e v e l . A more d e t a i l e d a n a l y s i s between l o c a l areas on the n o r t h e r n s h e l f u s i n g T/S diagrams suggested 62 16-15-14-TJ I 3 H iu 12-a 5 II-cc 111 Johnstone Strait S.E. Queen Charlotte Sound W Central Hecate Strait 23 — i — 24 —I T 1 1 1 r 25 26 27 28 29 3 0 Hecate Strait , Cape Caution Fitzhugh Sound. Milbanke Sound. Hecate Strait ixon Entrance * Queen Charlotte Strait ~ T 1 1 1 1 1 1 r 24 25 26 27 26 29 30 31 SALINITY % o FIGURE 4. Near su r f ace (3 m) t e m p e r a t u r e / s a l i n i t y p l o t s for C r u i s e 12 (February 1980; A) and C r u i s e 11 ( J u l y 1979; B ) , wi th s t a t i o n s grouped i n t o geographic a r e a s . 63 t h e r e can be c o n s i d e r a b l e d i f f e r e n c e s i n temperature and s a l i n i t y sea sona l p a t t e r n s . For example, F i t z Hugh Sound had a s t r o n g i n f l u e n c e of low s a l i n i t y water i n l a t e s p r i n g and summer, w h i l e Mi lbanke Sound had l e s s than a 2%0 v a r i a t i o n of s a l i n i t y a l l y e a r , even though both areas are ad j acent to s o u t h e a s t e r n Queen C h a r l o t t e Sound. Such s p a t i a l h e t e r o g e n e i t y i s i n d i c a t i v e of the l o c a l e f f e c t s of r u n o f f , a d v e c t i o n and m i x i n g demonstrated by Dodimead (1980; reviewed in Chapter 2) u s i n g n o r t h coas t l i g h t h o u s e d a t a . 3. CHLOROPHYLL The seasona l p a t t e r n of c h l o r o p h y l l on the n o r t h e r n s h e l f i s t y p i c a l of temperate c o a s t a l water s , i . e . a p h y t o p l a n k t o n bloom i n s p r i n g , r e l a t i v e l y low c o n c e n t r a t i o n s i n summer w i t h a secondary bloom d u r i n g the f a l l . However, as was demonstrated above for p h y s i c a l , p r o p e r t i e s , there can be c o n s i d e r a b l e l o c a l s c a l e v a r i a b i l i t y . F i g . 5 i n d i c a t e s c h l o r o p h y l l tempora l v a r i a b i l i t y for a south - n o r t h g r a d i e n t from Queen C h a r l o t t e Sound to Dixon E n t r a n c e , a l t h o u g h most of the s t a t i o n s i n t h i s l a t t e r r e g i o n were l o c a t e d in the southeas t c o r n e r . The s p a t i a l v a r i a b i l i t y of c h l o r o p h y l l w i t h i n each r e g i o n i s demonstrated by the l a r g e s tandard d e v i a t i o n s . F i g . 5 does , however, suggest r e g i o n a l d i f f e r e n c e s i n t i m i n g of the s p r i n g bloom, from A p r i l i n c o a s t a l Queen C h a r l o t t e Sound and Hecate S t r a i t to June i n Dixon E n t r a n c e . 64 •to ^ 8 | 6 QUEEN CHARLOTTE SOUND/STRAIT A S O J A M J J 12 17 F A J 5 4 w •I 2 4 A S O J A M J J HECATE STRAIT 14 F A J DIXON ENTRANCE/CHATHAM SOUND ~ 6 ^. 4 Ol _ 2 A S O N D J F M A M J J A S O N D J F M A M J 1978 | 1979 | 1980 FIGURE 5. Temporal d i s t r i b u t i o n of 3 m c h l o r o p h y l l as sampled by Imperial Tofino in Queen C h a r l o t t e Sound and S t r a i t , Hecate S t r a i t , and Dixon E n t r a n c e . V a l u e s are p r e s e n t e d as c h l a monthly means ± 1 s tandard d e v i a t i o n . Numbers r e p r e s e n t number of s t a t i o n s sampled that month i n each a r e a . Dots wi thout numbers i n d i c a t e a s i n g l e sample. 65 TABLE IV . Monthly mean c h l o r o p h y l l a c o n c e n t r a t i o n s and v a r i a n c e s on the B . C . n o r t h e r n s h e l f as measured on Imperial Tofino c r u i s e s ; number of s t a t i o n s ( n ) ; s t andard d e v i a t i o n (s) c o e f f i c i e n t of v a r i a t i o n ( C V ) . DATE •MEAN CHL CV(%) Aug "78 Sep 78 Oct 78 Jan 79 Apr 7 9 May 7 9 Jun 79 J u l 79 Feb 80 Apr 80 Jun 80 1 7 1 5 22 7 1 1 18 1 5 18 30 35 28 2, 1 . 1 , 0. 3, 2, 3, 2, 0, 1 , 2, 77 21 1 1 1 7 28 1 3 02 1 1 1 7 29 50 7 5 6 9 4 110, 82, 137 69 141 83.7 65.0 56.0 43.0 115.0 64.3 06 99 53 1 2 64 78 96 18 07 48 61 C h l o r o p h y l l a c o n c e n t r a t i o n s measured on the n o r t h e r n s h e l f ranged from a low of 0.05 Mg L " 1 i n winter (February 1980) to a h i g h i n s p r i n g of 15 Mg L " 1 ( A p r i l 1980). The monthly v a r i a b i l i t y of c h l o r o p h y l l a i n the r e g i o n i s shown in Tab le I V . Lowest mean v a l u e s and c o e f f i c i e n t s of v a r i a t i o n ( s tandard d e v i a t i o n to mean r a t i o expres sed as a percentage) o c c u r r e d i n winter s u g g e s t i n g c o n c e n t r a t i o n s of c h l o r o p h y l l were r e l a t i v e l y homogeneous throughout the r e g i o n . The h i g h e s t mean va lue i n 1979 o c c u r r e d i n s p r i n g ( A p r i l ) , w h i l e i n 1980 i t was i n June . Highes t c o e f f i c i e n t s of v a r i a t i o n o c c u r r e d i n A p r i l of both year s and i n October 1978, each be ing p e r i o d s when blooms would be expected i n l o c a l i z e d areas p r o d u c i n g c o n s i d e r a b l e s p a t i a l 66 h e t e r o g e n e i t y . The h i g h mean c h l o r o p h y l l v a l u e s of June 1979 and 1980 w i t h lower c o e f f i c i e n t s of v a r i a t i o n suggest most areas had e x p e r i e n c e d the s p r i n g i n c r e a s e of phytop l ankton by t h i s t i m e . An i n d i c a t i o n of the s p a t i a l d i s t r i b u t i o n of c h l o r o p h y l l over the n o r t h e r n s h e l f i s g iven by F i g s . 6 and 7. In A p r i l 1980 ( F i g . 6A) h i g h e s t c h l o r o p h y l l c o n c e n t r a t i o n s were observed over the sha l low banks of western Hecate S t r a i t , w i t h su r round ing c o n c e n t r a t i o n s l e s s than 1 /ig L " 1 . C o n c e n t r a t i o n s were a l s o h i g h (1-6 jug L" 1 ) i n c o a s t a l areas of southeas te rn Queen C h a r l o t t e Sound, s p e c i f i c a l l y F i t z Hugh Sound, whi le over the s h e l f break of c e n t r a l Queen C h a r l o t t e Sound c o n c e n t r a t i o n s were aga in <1 ug L~ 1 . In June 1980 ( F i g . 7A) c o n c e n t r a t i o n s in western Hecate S t r a i t had decreased to <1 Mg L " 1 but i n c r e a s e d to 2-5 Mg L " 1 i n e a s t e r n Hecate S t r a i t . C o a s t a l areas of Queen C h a r l o t t e Sound were s t i l l >1.5 Mg L " 1 c h l o r o p h y l l . Such a sea sona l and r e g i o n a l c h l o r o p h y l l p a t t e r n for the n o r t h e r n s h e l f can be compared w i t h that for the S t r a i t of Georg i a as d e s c r i b e d i n the l i t e r a t u r e . Parsons et al. (1970) rev iewed r e s u l t s from a four year study conducted d u r i n g the l a t e 1960 ' s . Mean c h l o r o p h y l l c o n c e n t r a t i o n s (0-20 m averages) from ten s t a t i o n s s c a t t e r e d throughout the s t r a i t were h i g h e s t in June and lowest d u r i n g November, whi le the h i g h e s t c o e f f i c i e n t s of v a r i a t i o n (75%) o c c u r r e d d u r i n g March and June . However, as w i t h the n o r t h e r n s h e l f , Parsons et al. (1970) noted c o n s i d e r a b l e s p a t i a l v a r i a t i o n of c h l o r o p h y l l , p a r t i c u l a r i l y i n the v i c i n i t y of the F r a s e r R i v e r plume. In a l a t e r study 67 FIGURE 6. A . C h l o r o p h y l l a in ng L " 1 (numbers on map) s p a t i a l d i s t r i b u t i o n on 10-17 A p r i l 1980 ( C r u i s e 13). Cros se s r e p r e s e n t s t a t i o n l o c a t i o n s . B. His tograms of N0 3 +N0 2 c o n c e n t r a t i o n s (uM) measured at the same l o c a t i o n s as c h l o r o p h y l l , and grouped i n t o geographic a r e a s . 68 FIGURE 7. A . C h l o r o p h y l l a (jig L" 1 ) s p a t i a l d i s t r i b u t i o n on 1-7 June 1980 ( C r u i s e 14) . Cros se s r epre sent s t a t i o n l o c a t i o n s . B. Hi s tograms of N0 3+N0 2 c o n c e n t r a t i o n s (MM) measured at the same l o c a t i o n s as c h l o r o p h y l l , and grouped i n t o geographic a r e a s . 69 (Parsons et al. 1981), c o n s i d e r a b l e v a r i a b i l i t y of sur face c h l o r o p h y l l c o n c e n t r a t i o n was a l s o noted i n the n o r t h e r n par t of the S t r a i t of Georg ia in c o n n e c t i o n wi th t i d a l m i x i n g among the c o n s t r i c t e d i s l a n d passages . 4. NUTRIENTS Samples for n i t r a t e p l u s n i t r i t e , s i l i c a t e , and phosphate were r o u t i n e l y taken on the Tofino s h i p of o p p o r t u n i t y c r u i s e s . Non-parametr ic Spearman rank c o r r e l a t i o n c o e f f i c i e n t s c a l c u l a t e d for these n u t r i e n t s for the p e r i o d August 1978 to J u l y 1979 i n d i c a t e d a l l were p o s i t i v e l y c o r r e l a t e d (p<0.05) i n each r e g i o n of the n o r t h e r n s h e l f . Non-parametr ic c o r r e l a t i o n s were used because the Kolmogorov-Smirnov g o o d n e s s - o f - f i t t e s t i n d i c a t e d these v a r i a b l e s were not n o r m a l l y d i s t r i b u t e d . C a l c u l a t i o n s were done u s i n g the SPSS s t a t i s t i c a l programs (Nie et al. 1975). As a r e s u l t of t h i s c o r r e l a t i o n , I w i l l present data for n i t r a t e p l u s n i t r i t e as r e p r e s e n t a t i v e of the g e n e r a l s ea sona l p a t t e r n of n u t r i e n t s on the n o r t h e r n s h e l f . N i t r a t e p l u s n i t r i t e c o n c e n t r a t i o n s ranged from 25 uM i n winter to n e g l i g i b l e v a l u e s i n summer, w i t h l a r g e v a r i a b i l i t y d u r i n g s p r i n g . In g e n e r a l , t h i s was the r e v e r s e seasona l t r e n d to c h l o r o p h y l l a, and for the p e r i o d August 1978 to J u l y 1979 c h l o r o p h y l l and n u t r i e n t s were i n v e r s e l y c o r r e l a t e d (p<0.05, Spearman c o r r e l a t i o n c o e f f i c i e n t ) . N i t r a t e p l u s n i t r i t e s p a t i a l d i s t r i b u t i o n s are i l l u s t r a t e d i n F i g s . 6B and 7B for comparison w i t h that of c h l o r o p h y l l a. C e r t a i n areas such as Johnstone 70 S t r a i t - e a s t e r n Queen C h a r l o t t e S t r a i t show h i g h n i t r a t e p l u s n i t r i t e c o n c e n t r a t i o n s (>10 uM.) i n a l l samples , r e f l e c t i n g the s t rong t i d a l mix ing which c h a r a c t e r i z e s t h i s r e g i o n (Thomson 1981). 5. PHYTOPLANKTON D u r i n g w i n t e r , sma l l f l a g e l l a t e s were the n u m e r i c a l l y dominant taxonomic group throughout the n o r t h e r n s h e l f . In s p r i n g , diatoms dominated many s t a t i o n s , w i t h the bloom predomina te ly composed of the genera Chaet oceros, Thai assi osi ra and the s p e c i e s Skeletonema cost at um. T h i s i s comparable wi th the c o m p o s i t i o n of the s p r i n g bloom i n the S t r a i t of G e o r g i a , where the p r i n c i p a l groups are Thalassi osi ra spp. and S. cost al um, w i t h blooms of Chaet ocer os o f t en o c c u r r i n g i n l a t e s p r i n g ( H a r r i s o n et al. 1983). Smal l u n i d e n t i f i e d f l a g e l l a t e s were aga in n u m e r i c a l l y dominant at most s t a t i o n s on the n o r t h e r n s h e l f d u r i n g summer, a l t h o u g h t h e r e was much more v a r i e t y than i n the win te r w i t h d i n o f l a g e l l a t e s ( e . g . Ceratium spp . ) and r e s i d u a l s p r i n g bloom diatoms abundant at some s t a t i o n s . However, when c o n s i d e r e d i n terms of the two major groups , diatoms and f l a g e l l a t e s , i t i s c l e a r that e s t i m a t e s of dominance on the b a s i s of n u m e r i c a l abundance a lone can be m i s l e a d i n g . T h i s problem has been p a r t i a l l y remedied w i t h the use of a biomass index e s t imated for each taxonomic group , as d e s c r i b e d i n the methods s e c t i o n of t h i s c h a p t e r . A s i m i l a r c o n v e r s i o n of abundance to approximate biomass ( H a r r i s o n et al. 1983) shows 71 that n a n o f l a g e l l a t e s were n u m e r i c a l l y important d u r i n g s p r i n g and summer, yet they compr i sed on ly 10% of the observed p h y t o p l a n k t o n carbon i n Saan ich I n l e t . A sea sona l p a t t e r n of the changing dominance of t h i s biomass index between these two groups can be p r e s e n t e d from summer 1978 to s p r i n g 1980 ( F i g . 8 ) . The p a t t e r n c l e a r l y r e p r e s e n t s the peak of d ia tom biomass over the whole of the n o r t h e r n s h e l f by l a t e s p r i n g , s i m i l a r to the p a t t e r n of s ea sona l c h l o r o p h y l l (Table IV) which showed h i g h c o n c e n t r a t i o n s and low v a r i a n c e d u r i n g June . D u r i n g J u l y 1978, diatoms dominated the e s t imated biomass index in a l l a reas sampled except sha l low western Hecate S t r a i t , where they compri sed <25% of the t o t a l biomass i n d e x . From August to October 1978 the f requency of s t a t i o n s at which diatoms dominated the biomass decreased u n t i l i t was <50% at a l l s t a t i o n s sampled d u r i n g January 1979. C o n s i d e r a b l e v a r i a b i l i t y of the major c o n t r i b u t o r to p h y t o p l a n k t o n biomass was aga in apparent by A p r i l 1979, sugges t ing v a r i a b i l i t y i n the o u t b u r s t of the s p r i n g bloom, w h i l e by e a r l y summer diatom biomass was aga in >50% at a l l s t a t i o n s except in western Hecate S t r a i t . The p a t t e r n was s i m i l a r d u r i n g s p r i n g 1980. To emphasize the s p a t i a l v a r i a b i l i t y of dominance by diatoms d u r i n g s p r i n g , data from A p r i l 1980 show they compri sed >50% of the t o t a l number of p h y t o p l a n k t o n (and t h e r e f o r e >50% of the biomass index) at s t a t i o n s i n western Hecate S t r a i t , the Cape C a u t i o n - F i t z Hugh Sound area i n s o u t h e a s t e r n Queen 72 1 . 0 n FIGURE 8. Frequency of s t a t i o n s sampled by Imperial Tofino in Queen C h a r l o t t e Sound, Hecate S t r a i t , and Dixon Entrance where the c a l c u l a t e d diatom biomass index (see t ex t ) i s g r e a t e r than the f l a g e l l a t e biomass index . Numbers bes ide x ' s r epre sent the t o t a l number of s t a t i o n s sampled d u r i n g that c r u i s e . 73 C h a r l o t t e Sound, and Johnstone S t r a i t . T h i s s t a t i o n i n Johnstone S t r a i t was somewhat s u r p r i s i n g , a l t h o u g h the h i g h diatom abundance may not be due to in situ p r o d u c t i o n because of the i n t e n s e t i d a l m i x i n g . I n s t e a d , i t may r e p r e s e n t p o p u l a t i o n s advec ted westward from the n o r t h e r n S t r a i t of G e o r g i a . Data i n Per ry et al. (1981) i n d i c a t e c h l o r o p h y l l c o n c e n t r a t i o n s d u r i n g A p r i l 1980 in waters ad jacent to S t u a r t I s l a n d at the mouth of Bute I n l e t (nor thern S t r a i t of Georg i a ) were >4 Mg L " 1 . The lowest numbers of t o t a l p h y t o p l a n k t o n , and l a ck of a p p r e c i a b l e numbers of d ia toms , o c c u r r e d at s t a t i o n s i n Queen C h a r l o t t e Sound over the c o n t i n e n t a l s h e l f break and i n c e n t r a l Dixon E n t r a n c e . C o r r e l a t i o n s between c h l o r o p h y l l a c o n c e n t r a t i o n s and p h y t o p l a n k t o n c o m p o s i t i o n for s t a t i o n s sampled d u r i n g February and A p r i l 1980 ( C r u i s e s 12 and 13) were c a l c u l a t e d to determine c o n t r i b u t i o n s to the s p r i n g i n c r e a s e of c h l o r o p h y l l . No s i g n i f i c a n t (p>0.05) c o r r e l a t i o n s o c c u r r e d fo r c h l o r o p h y l l a (as Mg L~ 1 ) a g a i n s t e i t h e r l o g 1 0 of t o t a l numbers of phytop lankton or l o g 1 0 of the number of diatoms L ~ 1 from data of C r u i s e 12 ( F e b r u a r y ) . However, for C r u i s e 13 ( A p r i l ) a s i g n i f i c a n t c o r r e l a t i o n (r=0.63, p<0.05) o c c u r r e d between c h l o r o p h y l l and l o g 1 0 number of diatoms L " 1 ( a c c o u n t i n g for 40% of the v a r i a n c e ) . Not s u r p r i s i n g l y t h e n , a s i g n i f i c a n t but weaker c o r r e l a t i o n (r=0.52) o c c u r r e d between c h l o r o p h y l l and the l o g 1 0 of t o t a l numbers of p h y t o p l a n k t o n (27% of the v a r i a n c e e x p l a i n e d ) . E v i d e n t l y the s p r i n g i n c r e a s e of c h l o r o p h y l l was due 74 to the i n c r e a s e in diatom abundance. 6. ZOOPLANKTON A n a l y s i s of zoop lankton c o l l e c t e d on these s h i p of o p p o r t u n i t y c r u i s e s i s c o m p l i c a t e d by two f a c t o r s : zoop lankton were not sampled from every s t a t i o n on each c r u i s e , r e d u c i n g f u r t h e r the s p a t i a l coverage ; and samples were c o l l e c t e d d u r i n g both day and n i g h t , perhaps b i a s i n g n i g h t samples w i t h v e r t i c a l l y m i g r a t i n g t a x a . However, g e n e r a l t r ends can be d e t e r m i n e d , w h i l e d e t a i l e d a n a l y s e s have been conducted p r i m a r i l y on n i g h t samples . Zooplankton abundance was lowest i n w i n t e r , r ang ing from 2 to 38 nr 3 i n January 1979 and 2 to 89 n r 3 i n February 1980. A l though s t a t i o n l o c a t i o n s were not i d e n t i c a l in both y e a r s , h i g h e s t numbers were ' sampled from s o u t h e a s t e r n Queen C h a r l o t t e Sound: the Cook Bank area j u s t n o r t h of Vancouver I s l a n d in 1979 and the mouth of F i t z Hugh Sound in 1980. Copepods were the dominant group , wi th Met ri dia pacifica and Pseudocal anus mi nut us the most common. Ps eudocal anus i s a l s o very common i n the S t r a i t of Georg i a d u r i n g w i n t e r , p a r t i c u l a r i l y in sha l low near - shore waters where i t grazes on sma l l f l a g e l l a t e s ( H a r r i s o n et al. 1983). In s p r i n g the range of zoop lankton d e n s i t i e s was much g r e a t e r than d u r i n g w i n t e r , c o r r e s p o n d i n g w i t h the g r e a t e r v a r i a b i l i t y of c h l o r o p h y l l and p h y t o p l a n k t o n c o n c e n t r a t i o n s at t h i s t i m e . D u r i n g A p r i l 1979 the range was 80-1800 n r 3 , w i t h copepods c o m p r i s i n g >50% of t o t a l zoop lankton numbers a t a l l 75 s t a t i o n s except o f f Sk idegate I n l e t i n western Hecate S t r a i t , where b a r n a c l e n a u p l i i made over 90% of t o t a l zoop lankton numbers. In A p r i l 1980, h i g h e s t c o n c e n t r a t i o n s of copepods were sampled from western Hecate S t r a i t (180 copepods n r 3 ) and the c o a s t a l passages of sou thea s te rn Queen C h a r l o t t e Sound, w h i l e o ther areas had <40 copepods n r 3 . P. mi nut us was a g a i n most common n u m e r i c a l l y d u r i n g s p r i n g , w h i l e Cal anus pacificus was common about Graham I s l a n d i n n o r t h e r n Hecate S t r a i t and Dixon E n t r a n c e . The zoop lankton o ther than copepods were fewer i n number than copepods , but f o l l o w e d a s i m i l a r d i s t r i b u t i o n p a t t e r n , be ing most abundant d u r i n g s p r i n g i n western Hecate S t r a i t and F i t z Hugh Sound (where >90% were b a r n a c l e n a u p l i i i n A p r i l 1980). Most common groups of non-copepod zoop lankton were b a r n a c l e n a u p l i i (o f ten a major component o f f Rose S p i t and i n F i t z Hugh Sound) , e u p h a u s i i d s and brachyuran c r a b zoea ( i n western Hecate S t r a i t , Dixon E n t r a n c e , and Mi lbanke Sound) , and the p te ropod Limacina (about the Queen C h a r l o t t e I s l a n d s ) . L a r v a l s tages of decapods and b a r n a c l e s are o f t en r e p o r t e d from p l a n k t o n surveys i n the S t r a i t of G e o r g i a , but t h e i r importance has not been s t u d i e d (Lev ings et al. 1983). However, such l a r g e p u l s e s of meroplankton are l i k e l y to have s i g n i f i c a n t impacts on p h y t o p l a n k t o n biomass at c e r t a i n t i m e s . D u r i n g s p r i n g 1979 and 1980, h i g h e r zoop lankton abundances appeared to c o i n c i d e w i t h h i g h e r p h y t o p l a n k t o n c o n c e n t r a t i o n s , e s p e c i a l l y i n western Hecate S t r a i t and sou thea s te rn Queen 76 C h a r l o t t e Sound. C o r r e l a t i o n s c a l c u l a t e d for c r u i s e s d u r i n g winter and s p r i n g 1980 ( C r u i s e s 12 and 13) between zooplankton and p h y t o p l a n k t o n , between diatoms and z o o p l a n k t o n , and between diatoms and copepods ( a l l l o g - t r a n s f o r m e d n u m e r i c a l abundances) produced o n l y one s i g n i f i c a n t (p<0.05) c o r r e l a t i o n : diatoms a g a i n s t t o t a l zoop lankton for s p r i n g ( C r u i s e 13, r=0.62 for 40% of the v a r i a n c e e x p l a i n e d ) . 7. ANALYSIS OF BLOOM TIMING An e s t imate of the r e l a t i v e t i m i n g of the s p r i n g p h y t o p l a n k t o n bloom (which i s p r e d o m i n a t e l y due to diatoms) between the S t r a i t of G e o r g i a , Queen C h a r l o t t e Sound, Hecate S t r a i t , and Dixon Entrance u s ing the method of Braarud and Nygaard (1978) i s p re sented in Tab le V . D u r i n g winter (January 1979, February 1980) a l l s t a t i o n s i n a l l r e g i o n s were c l e a r l y i n the low p r o d u c t i v i t y pre-bloom ca tegory w i t h h i g h n u t r i e n t c o n c e n t r a t i o n s . By A p r i l 1979 and 1980, c o n s i d e r a b l e v a r i a b i l i t y in the r e l a t i v e s t a t e of the s p r i n g bloom was e v i d e n t , as a l r e a d y noted i n the p r e v i o u s d i s c u s s i o n s of c h l o r o p h y l l , n u t r i e n t , and p l a n k t o n c h a r a c t e r i s t i c s ( e . g . Tab le I V ) . A l l l o c a t i o n s i n the S t r a i t of G e o r g i a d u r i n g A p r i l 1979 i n d i c a t e d bloom or pos t -b loom c o n d i t i o n s , w h i l e the o n l y s t a t i o n sampled i n 1980 was l o c a t e d among the i s l a n d passages at the n o r t h e r n end of the s t r a i t , an area known for i t s v i g o r o u s t i d a l mix ing (Parsons et al . 1981). T h i s s t a t i o n had low c h l o r o p h y l l and h i g h n u t r i e n t TABLE V. Qual i ta t ive spr ing bloom analys is fo l lowing the technique of Braarud and Nygaard (1978) appl ied to B . C . coasta l waters. Roman numerals re fer to the bloom ca tegor ie s : I - pre-bloom; II - ear ly bloom; III - l a te bloom; IV - post-bloom. Arab ic numerals r e fe r to the number of s ta t ions on each IMPERIAL TOFINO cruise which f e l l in to each bloom category. GEORGIA STRAIT QUEEN CHARLOTTE SOUND HECATE STRAIT DIXON ENTRANCE 1979 1980 JANUARY APRIL MAY JUNE FEBRUARY APRIL 1st week 1st week 2nd-3rd week 4th week 1st week 2nd week Cr . 7 Cr . 8 Cr . 9 C r . 10 Cr . 12 C r . 13 I II III IV II IV I I I IV I I 2 2 2 1 1 2 4 3 7 1 I I II III I I I IV I I I IV I I III IV 2 1 1 3 1 4 3 1 11 2 3 7 I I IV I I I IV I I I IV I I I III IV 2 1 1 2 1 2 2 12 1 2 2 I I I I I IV I I IV 2 2 2 1 2 3 2 78 c o n c e n t r a t i o n s t y p i c a l of w in te r or v e r t i c a l l y w e l l - m i x e d l o c a t i o n s . Queen C h a r l o t t e Sound and Hecate S t r a i t g e n e r a l l y i n d i c a t e d bloom c o n d i t i o n s , w i t h some v a r i a b i l i t y depending on the l o c a t i o n of s t a t i o n s . A l t h o u g h l o c a t i o n s were not i d e n t i c a l between year s the bloom appeared to be more advanced throughout both these r e g i o n s by the second week of A p r i l i n 1980 than the f i r s t week of A p r i l i n 1979. The data as p re sen ted are i n s u f f i c i e n t to d i s t i n g u i s h the t i m i n g of blooms between Queen C h a r l o t t e Sound and Hecate S t r a i t . A l s o d u r i n g A p r i l , s t a t i o n s i n Dixon Ent rance remained in the pre-b loom c a t e g o r y t y p i c a l of w i n t e r , except for two s t a t i o n s i n Chatham Sound i n 1980. These s t a t i o n s may not have been w e l l r e p r e s e n t e d by the d e f i n i t i o n s of the bloom c a t e g o r i e s g iven i n the methods s e c t i o n , as both c h l o r o p h y l l and phytop lankton c o n c e n t r a t i o n s were low yet n i t r a t e was o n l y 5 MM. By May, a l l l o c a t i o n s sampled i n the S t r a i t of G e o r g i a , Queen C h a r l o t t e Sound and Hecate S t r a i t were t y p i c a l of the bloom and pos t -b loom c a t e g o r i e s , w h i l e the two s t a t i o n s in Dixon Ent rance were s t i l l i n pre-b loom c o n d i t i o n s . S t a t i o n s i n Dixon Entrance d i d not show bloom c h a r a c t e r i s t i c s u n t i l June 1979. T h e r e f o r e , based on the r a t h e r coar se monthly sampl ing s e r i e s of J anuary , A p r i l , May, June 1979 and F e b r u a r y , A p r i l 1980, the s p r i n g d ia tom bloom o c c u r r e d by A p r i l in the n o r t h e r n S t r a i t of G e o r g i a , Queen C h a r l o t t e Sound and Hecate S t r a i t , w i t h an i n d i c a t i o n of i t be ing s l i g h t l y more advanced i n the S t r a i t of G e o r g i a i n 1979. Dixon Entrance d i d not g e n e r a l l y show 79 c h a r a c t e r i s t i c s of a bloom u n t i l l a t e r in the s p r i n g (June i n 1979). 8. SOUTHEASTERN QUEEN CHARLOTTE SOUND The q u a l i t a t i v e a n a l y s i s of bloom t i m i n g emphasizes l a r g e s c a l e p a t t e r n s between the four r e g i o n s of the coas t r a t h e r than v a r i a b i l i t y w i t h i n r e g i o n s . However, as much of the f o r e g o i n g d i s c u s s i o n of s h i p of o p p o r t u n i t y data makes c l e a r , there can be c o n s i d e r a b l e v a r i a b i l i t y wi th l o c a t i o n in a g iven a r e a , a problem compounded by the smal l number of s t a t i o n s . To examine the coarse s c a l e w i t h i n - r e g i o n v a r i a b i l i t y , c h a r a c t e r i s t i c s of two areas w i l l be c o n s i d e r e d in some d e t a i l . T h i s s e c t i o n d i s c u s s e s the s o u t h e a s t e r n corner of Queen C h a r l o t t e Sound, w h i l e the f o l l o w i n g two chap te r s focus on seasona l mechanisms i n Hecate S t r a i t . One area of the n o r t h e r n s h e l f c o n s i s t e n t l y sampled by the Tofino was s o u t h e a s t e r n Queen C h a r l o t t e Sound ( F i g . 9 ) , i n c l u d i n g Johnstone S t r a i t , Queen C h a r l o t t e S t r a i t , P ine I s l a n d and Cape C a u t i o n , F i t z Hugh Sound, and Mi lbanke Sound. I t i s c o a s t a l and l i k e l y to be s t r o n g l y i n f l u e n c e d by l o c a l runof f and m i x i n g c o n d i t i o n s as demonstrated for s i m i l a r areas by the n o r t h coas t l i g h t h o u s e data (Dodimead 1980, and Chapter 2 ) . D i s c u s s i o n of t h i s t r a n s e c t w i l l emphasize r e g i o n a l d i f f e r e n c e s between Queen C h a r l o t t e S t r a i t , F i t z Hugh Sound and Mi lbanke Sound r a t h e r than the s m a l l s c a l e v a r i a t i o n s that r e s u l t from l o c a l c o n d i t i o n s . FIGURE 9. L o c a t i o n map showing the route of Imperial Tofino (dashed l i n e ) through southeas te rn Queen C h a r l o t t e Sound and p l a c e names r e f e r r e d to in the t e x t . 81 C o n d i t i o n s d u r i n g winter 1979 were t y p i c a l of those throughout the n o r t h e r n s h e l f , w i t h low diatom and zoop lankton abundances, c h l o r o p h y l l a c o n c e n t r a t i o n s <1 nq L " 1 , and abundant n u t r i e n t s w i t h n i t r a t e p l u s n i t r i t e g e n e r a l l y >20 MM. By s p r i n g ( A p r i l 1979, F i g . 10) d i a tom, copepod and c h l o r o p h y l l a c o n c e n t r a t i o n s were much g r e a t e r i n F i t z Hugh Sound and Mi lbanke Sound than Queen C h a r l o t t e S t r a i t . T h i s d i f f e r e n c e i s most c l e a r l y marked between s t a t i o n s at the mouth of F i t z Hugh Sound and the mouth of Queen C h a r l o t t e S t r a i t . S a l i n i t y was a l s o minimum at the mouth of F i t z Hugh Sound, p r o b a b l y r e l a t e d to i n c r e a s e d runo f f i n t o R i v e r s I n l e t ad j acent to F i t z Hugh Sound which begins i n A p r i l (Water Resources Branch 1977). In May 1979 ( F i g . 11), c o n c e n t r a t i o n s of c h l o r o p h y l l , diatoms and copepods were h i g h e s t at the mouth of F i t z Hugh Sound and i n Queen C h a r l o t t e Sound ad j acent to Cape C a u t i o n . XBT p r o f i l e s suggest r e l a t i v e l y sha l low s t r a t i f i c a t i o n i n t h i s a r e a , which may be runo f f r e l a t e d (note lower s a l i n i t y at S t a t i o n 18) and ac t to decrease the depth of s u r f a c e m i x i n g . C o n d i t i o n s i n Queen C h a r l o t t e S t r a i t were s t i l l s i m i l a r to A p r i l ( F i g . 10), w i t h low biomass , h i g h n u t r i e n t s , and v e r t i c a l l y w e l l - m i x e d c o n d i t i o n s as i n d i c a t e d by the XBT p r o f i l e s . Queen C h a r l o t t e S t r a i t showed some i n d i c a t i o n of a p h y t o p l a n k t o n bloom i n June 1979 w i t h c h l o r o p h y l l c o n c e n t r a t i o n s about 7 jug L" 1 and copepod c o n c e n t r a t i o n s about 1000 m ~ 3 , a l t h o u g h n i t r a t e p l u s n i t r i t e was s t i l l h i g h (11 MM) . The s p a t i a l ex tent of t h i s bloom i s not known as o n l y the one FIGURE 10. Imperial Tofino t r a n s e c t through c o a s t a l Queen C h a r l o t t e Sound, 1-8 A p r i l 1979 ( C r u i s e 8 ) . Data are from d i s c r e t e s t a t i o n s at 3 m d e p t h , not cont inuous t r a n s e c t s ; f p r e c i s e s t a t i o n l o c a t i o n s see Appendix I . 83 FIGURE 11. Imperial Tofino t r a n s e c t through c o a s t a l Queen C h a r l o t t e Sound, 9-16 May 1979 ( C r u i s e 9 ) . Data are from d i s c r e t e s t a t i o n s at 3 m dep th ; for p r e c i s e l o c a t i o n s see Appendix I . Bottom pane l shows the v e r t i c a l temperature s t r u c t u r e and approximate bathymetry from XBT p r o f i l e s ( d o t s ) . 84 s t a t i o n was sampled i n Queen C h a r l o t t e S t r a i t ( C r u i s e 10, S t a t i o n 7 ) . However, by J u l y 1979 ( F i g . 12) t h i s area aga in i n d i c a t e d low biomass , h i g h n u t r i e n t s and r e l a t i v e l y w e l l - m i x e d c o n d i t i o n s , whi le the h i g h e s t biomass o c c u r r e d i n Queen C h a r l o t t e Sound between F i t z Hugh Sound and Queen C h a r l o t t e S t r a i t . The low s a l i n i t y , h i g h temperature sur f ace water had spread throughout the area to the mouth of Queen C h a r l o t t e S t r a i t , r e s u l t i n g i n w e l l - e s t a b l i s h e d v e r t i c a l s t r a t i f i c a t i o n . Two s t a t i o n s , i n Queen C h a r l o t t e Sound and Mi lbanke Sound, had 3000-4000 copepods nr 3 , w i th Centropages abdomi nal i s, Acartia spp. and Pseudocal anus spp. most common, a long wi th l a r g e c o n c e n t r a t i o n s of b a r n a c l e n a u p l i i i n Mi lbanke Sound (70 m ~ 3 ) . Data from c r u i s e s through t h i s a rea i n s p r i n g 1980 show a s i m i l a r p a t t e r n of low biomass " w i n t e r " c o n d i t i o n s i n Queen C h a r l o t t e S t r a i t and h i g h e r biomass " s p r i n g " c o n d i t i o n s i n F i t z Hugh and Mi lbanke Sounds. The s p a t i a l h e t e r o g e n e i t y throughout t h i s r e g i o n and the apparent spread of the bloom from F i t z Hugh Sound i n t o Queen C h a r l o t t e Sound i s demonstrated by data c o l l e c t e d from the MV Pandora 11 (DOUBC C r u i s e 80-7) from 28 A p r i l to 3 May 1980. F i g . 13 maps the n e a r - s u r f a c e (4 m) c h l o r o p h y l l a d i s t r i b u t i o n as measured by c o n t i n u o u s f l u o r e s c e n c e on t r a n s e c t s a c r o s s the r e g i o n . C h l o r o p h y l l was c a l c u l a t e d from f l u o r e s c e n c e u s ing a r e g r e s s i o n equa t ion of e x t r a c t e d c h l o r o p h y l l ver sus i t s f l u o r e s c e n c e l i n e h e i g h t (FLH) l o g 1 0 c h l . a(ug L " 1 ) = -1 .13 + 0.23 * F L H , FIGURE 12. Imperial Tofino t r a n s e c t through c o a s t a l Queen C h a r l o t t e Sound, 16-27 J u l y 1979 ( C r u i s e 11) . For s t a t i o n l o c a t i o n s see Appendix I . Bottom pane l shows the v e r t i c a l temperature s t r u c t u r e and approximate bathymetry from XBT p r o f i l e s ( d o t s ) . 86 I28°W FIGURE 13. Near sur face (4 m) c h l o r o p h y l l (jxg L" 1 ) d i s t r i b u t i o n as measured on 29 A p r i l 1980 by Pandora II (DOUBC c r u i s e 80-7) in s o u t h e a s t e r n Queen C h a r l o t t e Sound. V a l u e s have been c o n v e r t e d from cont inuous in vivo f l u o r e s c e n c e data as measured a long the c r u i s e t r a c k (dashed l i n e ) , and contoured by hand. 87 wi th r 2 =0 .96 for n=9 samples . The extent of the bloom and i t s l e a d i n g edge i n Queen C h a r l o t t e Sound are c l e a r l y i n d i c a t e d . No q u a l i t a t i v e o b s e r v a t i o n s of the appearance of t h i s f r o n t are a v a i l a b l e as i t was c r o s s e d at n i g h t . V e r t i c a l p r o f i l e s of c h l o r o p h y l l , temperature and s a l i n i t y at s t a t i o n s on e i t h e r s i d e of t h i s f r o n t are p re sen ted i n F i g . 14. C h l o r o p h y l l a was low and uni form with depth at S t a t i o n s 13 and 8 o u t s i d e the bloom (see F i g . 13) , wi th l i t t l e v a r i a t i o n of temperature or s a l i n i t y . At S t a t i o n s 7 and 22 i n s i d e F i t z Hugh Sound however, there was c o n s i d e r a b l e v e r t i c a l s t r u c t u r e of c h l o r o p h y l l . Near the f r o n t ( S t a t i o n 7 ) , c h l o r o p h y l l was very h i g h w i t h i n the upper 0-5 m, w i t h decreased s a l i n i t y and h i g h e r temperatures near the s u r f a c e sugge s t ing some v e r t i c a l s t r a t i f i c a t i o n . F u r t h e r i n s i d e F i t z Hugh Sound at S t a t i o n 22, n e a r - s u r f a c e c h l o r o p h y l l c o n c e n t r a t i o n s were lower w i t h a subsur face c h l o r o p h y l l maximum. The p a t t e r n of n u t r i e n t s at these four s t a t i o n s was the i n v e r s e to that for c h l o r o p h y l l . Temperature p r o f i l e s from XBT c a s t s a l s o i n d i c a t e d a sha l low s t r a t i f i e d l a y e r i n s i d e F i t z Hugh Sound. A subsequent c r u i s e to t h i s area onboard CNAV Ende av our (DOUBC C r u i s e 81-10, 6-9 A p r i l 1981) found c o n d i t i o n s t y p i c a l of w i n t e r , w i t h low c h l o r o p h y l l and h i g h n u t r i e n t s . T h i s i s c o n s i s t e n t w i t h the p a t t e r n of i n i t i a t i o n of the bloom i n t h i s area suggested by Tofino C r u i s e 13, where w i n te r c o n d i t i o n s p r e v a i l e d on the northbound l e g on 11 A p r i l 1980, w h i l e on the southbound l e g 5 days l a t e r the bloom had appeared . T h i s bloom 88 FIGURE 14. V e r t i c a l p r o f i l e s of c h l o r o p h y l l a ( t op , S t a t i o n s 7 ,8 ,13 ,22 ) and temperature and s a l i n i t y (bottom, S t a t i o n s 7 and 8) measured by Pandora II on 29 A p r i l 1980 i n southeas te rn Queen C h a r l o t t e Sound. See F i g . 13 for s t a t i o n l o c a t i o n s ; note S t a t i o n s 8 and 13 are o u t s i d e the bloom, S t a t i o n s 7 and 22 i n s i d e . 89 was subsequent ly a n a l y s e d i n more d e t a i l by the Pandora II cruise. D. DISCUSSION As t h i s study i s the f i r s t to examine p h y t o p l a n k t o n d i s t r i b u t i o n s on the n o r t h e r n s h e l f of B . C . i n a sy s t emat i c manner, no p r e v i o u s data are a v a i l a b l e for compar i son . However, zoop lankton data are a v a i l a b l e from p r e v i o u s s t u d i e s , and can be compared w i t h the s h i p of o p p o r t u n i t y r e s u l t s . A n a l y s i s of stomach c o n t e n t s of sa lmonids ( e . g . Manzer 1969) i n d i c a t e copepods , l a r v a c e a n s , b a r n a c l e and decapod l a r v a e , amphipods and e u p h a u s i i d s are p o t e n t i a l p r e y . A l l these have been i d e n t i f i e d from n o r t h c o a s t a l waters by the SHOP program, o f t en w i t h c o n s i d e r a b l e s p a t i a l and tempora l h e t e r o g e n e i t y . For example, decapod l a r v a e and c r a b zoea were ex t remely abundant i n western Hecate S t r a i t and b a r n a c l e l a r v a e were abundant in e a s t e r n Hecate S t r a i t i n June 1979 and 1980 (data i n P e r r y et al . 1981 and Chapter s 5 and 6 of t h i s t h e s i s ) . L e B r a s s e u r ' s (1966) c o n c l u s i o n that prey a v a i l a b i l i t y may be more important to f eed ing than prey p r e f e r e n c e suggests such l a r g e c o n c e n t r a t i o n s may be very important for s u r v i v a l of j u v e n i l e f i s h . The more common copepod s p e c i e s i d e n t i f i e d by Cameron (1957) about the Queen C h a r l o t t e I s l a n d s i n c l u d e d Paracal anus parvus, Acartia clausii, Centropages abdomi nalis, and Tortanus discaudatus. She took v e r t i c a l tows, but i n g e n e r a l found a l l 90 the above except T. dis caudal us d i s t r i b u t e d w i t h i n the upper 14 m. These z o o p l a n k t e r s shou ld t h e r e f o r e have been r e p r e s e n t a t i v e l y sampled by the M i l l e r sampler towed from the Tofino. In Cameron's (1957) s tudy , r e l a t i v e l y r a re forms i n Hecate S t r a i t i n c l u d e d P. parvus, A. clausii, and T. discaudatus, whi le C. abdomi nal i s was r e l a t i v e l y common. In the SHOP c o l l e c t i o n s from June 1979 and 1980, C. abdomi nalis was common at most s t a t i o n s sampled throughout the n o r t h e r n s h e l f , and e s p e c i a l l y abundant in Hecate S t r a i t and F i t z Hugh Sound. Acartia spp. were a l s o common at a l l s t a t i o n s , a l t h o u g h A. longiremis was more t y p i c a l than A. clausii. P. parvus was not p a r t i c u l a r i l y common, a l tho ugh the m o r p h o l o g i c a l l y s i m i l a r s p e c i e s Pseudocal anus mi nut us was the most abundant copepod throughout the n o r t h e r n s h e l f . C o r k e t t and McLaren (1978) i d e n t i f i e d Pseudocal anus as a very important food source for l a r v a l f i s h e s , and i t s abundance d u r i n g s p r i n g and summer may p l a y a c r i t i c a l r o l e i n t h e i r s u r v i v a l . The most complete s p a t i a l sampl ing for zoop lankton has been done by F u l t o n et al. (1982), a l t h o u g h i t covered o n l y the p e r i o d January to A p r i l 1980. These samples are not s t r i c t l y comparable w i t h the s h i p of o p p o r t u n i t y c o l l e c t i o n s , be ing o b l i q u e tows from bottom to sur f ace w i t h s t a t i o n s l o c a t e d i n open water r a t h e r than among the c o a s t a l passages as are many of the SHOP s t a t i o n s . As a r e s u l t , w h i l e F u l t o n et al. (1982) d i d f i n d some s t a t i o n s dominated by b a r n a c l e n a u p l i i as on the Tofino c r u i s e s , the dominant organism throughout the n o r t h e r n 91 s h e l f was Neocal anus plumchrus. In the Tofino samples , N. plumchrus was abundant o n l y from deep water s t a t i o n s l o c a t e d i n F i t z Hugh Sound d u r i n g June 1980; Gardner (1982a) a l s o noted abundant p o p u l a t i o n s of e a r l y stage N. plumchrus at the head of F i t z Hugh Sound i n A p r i l 1977. 1. SPRING BLOOM TIMING The c r i t i c a l depth - mixed depth p a t t e r n of F i g . 3 demonstrates a northward p r o g r e s s i o n of c o n d i t i o n s a p p r o p r i a t e for a s p r i n g d ia tom bloom a l o n g the B . C . c o a s t , but i t i s not e n t i r e l y s e q u e n t i a l between ad jacent a r e a s . The S t r a i t of Georg i a c e r t a i n l y support s the longes t growing season w i t h the e a r l i e s t s p r i n g bloom, w h i l e c o n d i t i o n s in Dixon E n t r a n c e suggest the l a t e s t bloom and the s h o r t e s t season . However, Queen C h a r l o t t e Sound and Hecate S t r a i t appear to have very s i m i l a r growing seasons w i t h s i m i l a r t i m i n g of the s p r i n g bloom d e s p i t e a d i s t a n c e of 300 km between t h e i r extreme b o u n d a r i e s . Normal d a i l y s o l a r r a d i a t i o n summarized by month for t h r e e l o c a t i o n s a l o n g the coas t (Table VI) i n d i c a t e t y p i c a l l y h i g h e r v a l u e s d u r i n g s p r i n g and summer i n the S t r a i t of G e o r g i a (Nanaimo), but r e l a t i v e l y s i m i l a r i n t e n s i t i e s for both Queen C h a r l o t t e Sound (Cape S t . James) and Hecate S t r a i t ( S a n d s p i t ) . However, i t must be noted i r r a d i a n c e and the c r i t i c a l depth - mixed depth a n a l y s e s are based on g e n e r a l f e a t u r e s measured over s e v e r a l y e a r s , w i t h s t a t i o n l o c a t i o n s p redomina te ly i n open water s . Such an a n a l y s i s i s not capab le of d i s t i n g u i s h i n g s m a l l s c a l e 92 TABLE V I . Normal d a i l y s o l a r r a d i a t i o n v a l u e s for each month (measured as MJ m~ 2 d " 1 ) for three s t a t i o n s on the B . C . coas t r e p r e s e n t a t i v e of the S t r a i t of G e o r g i a (Nanaimo), Queen C h a r l o t t e Sound (Cape S t . James) , and Hecate S t r a i t ( S a n d s p i t ) . Data are from the Monthly R a d i a t i o n Summary, Atmospher ic Environment S e r v i c e , Ottawa; normals are c a l c u l a t e d for the p e r i o d 1967--1980 (Sandspi t and Cape S t . James) and 1959-1980 (Nanaimo). MONTH NANAIMO CAPE ST . SANDSPIT HOURS OF JAMES L IGHT January 2.904 2.636 2.415 10 February 6.050 5. 1 74 4.896 1 2 March 10.488 9.009 8.984 1 4 Apr i 1 16.439 13.934 13.578 1 5 May 21.120 19.087 18.159 1 6 June 22.188 19.676 17.773 18 J u l y 23.718 19.092 17. 174 18 August 19.587 16.610 15.049 1 6 September 13.994 12.174 13.576 1 4 October 7.725 6.629 5.874 1 2 November 3. 149 3.243 4. 102 1 0 December 2.333 3.779 1 .804 8 v a r i a t i o n s w i t h i n each r e g i o n , which can be q u i t e important i n d e t e r m i n i n g the p r e c i s e p a t t e r n of bloom i n i t i a t i o n . The v a r i a b i l i t y of c o n d i t i o n s w i t h i n each r e g i o n of the coas t i s w e l l demonstrated by the Tofino s h i p of o p p o r t u n i t y d a t a . Both c h l o r o p h y l l c o n c e n t r a t i o n s and the e s t imated p h y t o p l a n k t o n biomass index showed t h e i r g r e a t e s t v a r i a b i l i t y throughout the nor thern s h e l f d u r i n g A p r i l , sugge s t ing the bloom had begun at some s t a t i o n s . The s p a t i a l d i s t r i b u t i o n of c h l o r o p h y l l and n u t r i e n t s d u r i n g s p r i n g ( F i g . 6A) shows t h i s v a r i a b i l i t y c l e a r l y , w i t h h i g h c o n c e n t r a t i o n s of c h l o r o p h y l l i n c o a s t a l r e g i o n s of s o u t h e a s t e r n Queen C h a r l o t t e Sound and 93 sha l low western Hecate S t r a i t . Lowest c o n c e n t r a t i o n s of c h l o r o p h y l l were in Dixon E n t r a n c e , e a s t e r n Hecate S t r a i t , and over the c o n t i n e n t a l s h e l f edge i n western Queen C h a r l o t t e Sound. Diatom biomass f o l l o w e d the p a t t e r n for c h l o r o p h y l l , s u g g e s t i n g the s p r i n g phytop l ankton i n c r e a s e was p r e d o m i n a t e l y a d ia tom bloom. High zoop lankton abundances c o i n c i d e d w i t h h i g h diatom c o n c e n t r a t i o n s d u r i n g s p r i n g , e s p e c i a l l y i n the areas of western Hecate S t r a i t and southwestern Queen C h a r l o t t e Sound, at l e a s t on the time s c a l e s of s a m p l i n g . Copepods, b a r n a c l e and decapod l a r v a e were major c o n s t i t u e n t s of these blooms, sugges t ing that i n v e r t e b r a t e s i n these areas wi th m e r o p l a n k t o n i c l a r v a e were r e p r o d u c i n g at the same time as the h o l o p l a n k t o n i c fauna and the p h y t o p l a n k t o n . The g e n e r a l p a t t e r n of the b i o l o g i c a l o b s e r v a t i o n s a l o n g the B . C . c o a s t , which tends to i n t e g r a t e t h i s w i t h i n - r e g i o n v a r i a b i l i t y , i s summarized by the q u a l i t a t i v e bloom a n a l y s i s t echn ique and r e p o r t e d i n Tab le V . I t suggests the s p r i n g bloom began e a r l y i n the S t r a i t of G e o r g i a , p r o b a b l y by March i n 1979. The t i m i n g for Queen C h a r l o t t e Sound and Hecate S t r a i t c o u l d not be d i s t i n g u i s h e d , w i t h the bloom i n both areas a p p e a r i n g to d e v e l o p at the b e g i n n i n g of A p r i l . In Dixon E n t r a n c e , the bloom was not apparent u n t i l l a t e May or e a r l y June i n 1979. These o b s e r v a t i o n s of the p r o g r e s s i o n of the s p r i n g bloom a l o n g the coas t i n g e n e r a l match those p r e d i c t e d by the c r i t i c a l depth - mixed depth a n a l y s i s . However, the p r e d i c t e d t i m i n g of 94 the o u t b u r s t d i d not agree wi th the o b s e r v a t i o n s from the S t r a i t of G e o r g i a and Queen C h a r l o t t e Sound. In Queen C h a r l o t t e Sound, the bloom was observed to occur e a r l i e r than p r e d i c t e d by the c r i t i c a l depth model . The s i m p l e s t e x p l a n a t i o n concerns the l o c a t i o n s of s t a t i o n s used for p r e d i c t i o n and o b s e r v a t i o n . C r i t i c a l depth model p r e d i c t i o n s were based on open ocean ic water s , w h i l e Tofino o b s e r v a t i o n s were p redomina te ly i n c o a s t a l a r e a s . As demonstrated by the Pandora II c r u i s e r e s u l t s for Queen C h a r l o t t e Sound in A p r i l 1980, diatom blooms may occur e a r l i e r in waters near shore than o f f s h o r e , e s p e c i a l l y i n the F i t z Hugh Sound a r e a . In the n o r t h e r n S t r a i t of G e o r g i a , the bloom was observed to occur l a t e r than p r e d i c t e d by the c r i t i c a l depth model . However, t h i s r e g i o n a l s o s u f f e r s from a poor d i s t r i b u t i o n of s t a t i o n s i n the SHOP program, so tha t the bloom may have o c c u r r e d i n e i t h e r February (as p r e d i c t e d ) or M a r c h . The p r e d i c t i o n s of t h i s t h e s i s a l s o agree wi th the p r e d i c t i o n s of Parsons (1965) for the Queen C h a r l o t t e Sound and Hecate S t r a i t r e g i o n s , even though he used mixed depth data fo r ad j acent ocean ic water s , and w i t h Parsons et al . (1966), who p r e d i c t e d a bloom for ocean ic waters of the e a s t e r n s u b a r c t i c P a c i f i c by A p r i l . The t i m i n g p r e d i c t e d in t h i s t h e s i s for a bloom in Dixon Ent rance d u r i n g May r a t h e r than A p r i l may i n p a r t be due to the l a ck of adequate measurements of the a t t e n u a t i o n c o e f f i c i e n t , r e s u l t i n g i n a b i a s e d e s t imate of the c r i t i c a l depth (note on ly 5 measurements were a v a i l a b l e for Dixon Entrance i n A p r i l ) . The 95 t i m i n g does , however, agree w i t h s t u d i e s on the s p r i n g p l a n k t o n bloom in the waters of s o u t h e a s t e r n A l a s k a . Near P r i n c e of Wales I s l a n d , j u s t n o r t h of Dixon E n t r a n c e , i t u s u a l l y began i n l a t e A p r i l or May, and was dominated by Chaet ocer os spp. and Skeletonema spp . (Alaska Dept . of F i s h and Game 1979, quoted i n Petro-Canada 1983). Highes t mean biomass of zoop lankton i n t h i s area ( i n 1972) o c c u r r e d in May and June, but dropped s h a r p l y d u r i n g J u l y (Mattson and Wing 1978). Copepods dominated the biomass , f o l l o w e d by chae togna ths , e u p h a u s i i d s , amphipods, amd b a r n a c l e n a u p l i i , which i s s i m i l a r to the c o m p o s i t i o n sampled from Dixon E n t r a n c e and Hecate S t r a i t . 2. COASTAL QUEEN CHARLOTTE SOUND The southwestern corner of Queen C h a r l o t t e Sound, i n c l u d i n g F i t z Hugh Sound and Mi lbanke Sound, has been shown by the s h i p of o p p o r t u n i t y o b s e r v a t i o n s to have an e a r l y s p r i n g bloom, a l o n g wi th western Hecate S t r a i t ( e . g . F i g . 6 A ) . More d e t a i l e d t r a n s e c t s i n d i c a t e d t h i s bloom can be w e l l deve loped by A p r i l , and compared t h i s r e g i o n w i t h Queen C h a r l o t t e S t r a i t , which showed c o n s i d e r a b l e p a t c h i n e s s . The p r e c i s e cause of t h i s bloom i n F i t z Hugh Sound i s unknown, a l t h o u g h a p o t e n t i a l mechanism (untes ted i n t h i s t h e s i s ) i s f re shwater r u n o f f . The seasona l i n c r e a s e of s o l a r r a d i a t i o n p r o g r e s s i n g from south to n o r t h (Table VI) may beg in to melt the snowpack of southern c o a s t a l areas f i r s t . R i v e r s f l o w i n g i n t o the F i t z Hugh and Mi lbanke Sound systems have a 96 l a r g e r percentage i n c r e a s e i n t h e i r flow volumes from March to A p r i l than do r i v e r s f u r t h e r n o r t h , and in f ac t the Dean R i v e r ( f l o w i n g i n t o Dean Channel and the head of F i t z Hugh Sound) reaches i t s peak mean flow d u r i n g May (Water Resources Branch 1977). T h i s f reshwater shou ld i n c r e a s e s t a b i l i t y w i t h i n the i n l e t system, and p o t e n t i a l l y i n c r e a s e the flow towards the open sea as a r e s u l t of the h y r a u l i c p re s sure g r a d i e n t . That s t r a t i f i c a t i o n does i n c r e a s e i s shown by the XBT p r o f i l e s of F i g s . 11 and 12, w h i l e the extent of the flow of lower s a l i n i t y water i n t o open Queen C h a r l o t t e Sound i s c l e a r l y shown by Dodimead (1980, p . 130 and 131). N u t r i e n t - r i c h subsur face water would l i k e l y be e n t r a i n e d i n t o t h i s seaward- f lowing sur f ace l a y e r , c r e a t i n g a r e l a t i v e l y h i g h l i g h t , h i g h n u t r i e n t environment i d e a l f o r p h y t o p l a n k t o n growth. The e a r l y marine phase of the l i f e c y c l e may be c r i t i c a l to f eed ing success and m o r t a l i t y r a t e s of o u t m i g r a t i n g j u v e n i l e s a l m o n i d s , t h e r e f o r e a f f e c t i n g the s i z e of the r e t u r n i n g p o p u l a t i o n (Healey 1980). S e v e r a l s t u d i e s have examined the seaward m i g r a t i o n s of p ink salmon (Oncor hync hus gor bus c ha) through the F i t z Hugh Sound and Mi lbanke Sound system to the open sea , and i t i s i n t e r e s t i n g to compare t h e i r r e s u l t s w i t h the s h i p of o p p o r t u n i t y f i n d i n g s for that a r e a . Parker (1965) s t u d i e d the 1961 p ink f r y brood year and found the ra te of n a t u r a l m o r t a l i t y was c o n s i d e r a b l y h i g h e r d u r i n g the i n i t a l shor t p e r i o d i n c o a s t a l waters compared w i t h the remain ing p e r i o d of sea l i f e . 97 Healey (1967) d e s c r i b e d the seaward m i g r a t i o n of these f r y , which took about one month to swim from the B e l l a Coo la R i v e r down Burke Channel to the open sea (Queen C h a r l o t t e Sound) . In h i s s t u d y , l a r g e numbers of f r y reached the upper waters of F i t z Hugh Sound by the end of May and b e g i n n i n g of June . P l a n k t o n c h a r a c t e r i s t i c s d u r i n g May 1979 ( F i g . 11) showed very h i g h copepod c o n c e n t r a t i o n s i n t h i s a r e a . Pink salmon f r y grow q u i c k l y and r e q u i r e a l a r g e food supply (Healey 1967), which may be p r o v i d e d by c a l a n o i d copepods d u r i n g t h i s m i g r a t i o n . In a s tudy of p ink f r y f eed ing i n an i n l e t of the Ala skan c o a s t , B a i l e y et al. (1976) noted a l l f i s h c o l l e c t e d i n d a y l i g h t c o n t a i n e d f o o d , of which copepods (both c a l a n o i d s and c y c l o p o i d s ) were dominant . B a r n a c l e n a u p l i i were a l s o common in both the i n l e t and the stomach c o n t e n t s , as has been suggested for the F i t z Hugh Sound r e g i o n by the s h i p of o p p o r t u n i t y d a t a . In the Skeena R i v e r a r e a , Manzer and Shepard (1962) suggested the g r e a t e s t number of p ink salmon f r y migra te to the ocean about mid-May and spend time growing i n i n s h o r e water s . T h i s t i m i n g i s a l s o s i m i l a r to that p r e d i c t e d for the s p r i n g bloom in Dixon E n t r a n c e by the c r i t i c a l depth model and observed on the Tofi no c r u i s e s . E . SUMMARY D e s p i t e the importance of the n o r t h e r n s h e l f r e g i o n for f i s h e r y and petro leum r e s o u r c e s of the B r i t i s h Columbia c o a s t , 98 i t s b i o l o g i c a l oceanography has been very p o o r l y s t u d i e d . A review of the l i t e r a t u r e i n d i c a t e s a few s t u d i e s have examined zooplankton at s e l e c t e d s i t e s in the r e g i o n , but phytop l ankton have been a lmost n e g l e c t e d . T h i s chapter has two main purposes : to present the f i r s t g e n e r a l survey of p l a n k t o n on the n o r t h e r n s h e l f by summarizing o b s e r v a t i o n s made from the Imperial Tofino from 1978 to 1980; and to examine the p a t t e r n of i n i t i a t i o n of the s p r i n g d ia tom bloom on the B . C . n o r t h e r n c o a s t . The summary of the o b s e r v a t i o n s focussed on temporal v a r i a b i l i t y between c r u i s e s , and s p a t i a l v a r i a b i l i t y between and w i t h i n the r e g i o n s of the n o r t h e r n s h e l f . C h l o r o p h y l l c o n c e n t r a t i o n s were lowest d u r i n g w i n t e r , h i g h e s t i n summer, and most v a r i a b l e d u r i n g s p r i n g , sugges t ing d i f f e r e n c e s i n t i m i n g of the s p r i n g bloom. S p a t i a l l y , h i g h e s t c h l o r o p h y l l c o n c e n t r a t i o n s d u r i n g s p r i n g ( A p r i l 1980) o c c u r r e d i n western Hecate S t r a i t and southeas te rn Queen C h a r l o t t e Sound. N u t r i e n t d i s t r i b u t i o n s were found to be the i n v e r s e of c h l o r o p h y l l . P h y t o p l a n k t o n biomass has been summarized i n terms of diatoms and f l a g e l l a t e s , u s i n g both abundance and an e s t imated biomass i n d e x . The temporal p a t t e r n was s i m i l a r to c h l o r o p h y l l , w i th the dominant component be ing f l a g e l l a t e s d u r i n g w i n t e r , and diatoms d u r i n g l a t e s p r i n g and e a r l y summer. D u r i n g s p r i n g , diatoms were the major components of the biomass index at s t a t i o n s i n western Hecate S t r a i t and southeas te rn Queen C h a r l o t t e Sound. C o r r e l a t i o n s of d ia tom abundance and c h l o r o p h y l l c o n c e n t r a t i o n s were s i g n i f i c a n t d u r i n g A p r i l 1980 99 sugges t ing tha t the s p r i n g i n c r e a s e of c h l o r o p h y l l was due to a d iatom bloom. Zooplankton a l s o f o l l o w e d t h i s b a s i c seasona l p a t t e r n , appear ing to c o i n c i d e (on the s c a l e of sampling) wi th h i g h e r phytop l ankton c o n c e n t r a t i o n s . Copepods were most abundant g e n e r a l l y , w i t h b a r n a c l e n a u p l i i and decapod l a r v a e abundant at s p e c i f i c l o c a t i o n s . C r i t i c a l depth - mixed depth c a l c u l a t i o n s suggest c o n d i t i o n s are a p p r o p r i a t e for a p h y t o p l a n k t o n s p r i n g bloom by A p r i l - M a y i n Queen C h a r l o t t e Sound, A p r i l i n Hecate S t r a i t , and May i n Dixon E n t r a n c e . O b s e r v a t i o n s of the s p r i n g blooms i n 1979 and 1980 agreed w i t h the p r e d i c t e d t i m i n g for Hecate S t r a i t and Dixon E n t r a n c e , but suggested i t o c c u r r e d e a r l i e r than p r e d i c t e d ( A p r i l ) i n Queen C h a r l o t t e Sound. T h i s l a t t e r may be due i n p a r t to the s t a t i o n l o c a t i o n s , as the o b s e r v a t i o n s were predominant ly i n c o a s t a l s o u t h e a s t e r n Queen C h a r l o t t e Sound, w h i l e the c r i t i c a l depth c a l c u l a t i o n s were from the open waters of Queen C h a r l o t t e Sound. The g e n e r a l p a t t e r n of the s p r i n g bloom t h e r e f o r e f o l l o w e d a northward p r o g r e s s i o n from the S t r a i t of G e o r g i a to Dixon E n t r a n c e , a l t h o u g h Queen C h a r l o t t e Sound and Hecate S t r a i t c o u l d not be d i s t i n g u i s h e d i n t h i s a n a l y s i s . Chapter 6 suggests pa r t of Hecate S t r a i t e x p e r i e n c e s an e a r l y s p r i n g bloom due to i t s sha l low bottom d e p t h . As an example of the s m a l l - s c a l e v a r i a b i l i t y t h a t occur s w i t h i n a r e g i o n , d e t a i l e d p l a n k t o n d i s t r i b u t i o n s and events l e a d i n g to a s p r i n g bloom were examined on s e v e r a l Imperial Tofino t r a n s e c t s through s o u t h e a s t e r n Queen C h a r l o t t e Sound. 100 I m p l i c a t i o n s of t h i s bloom for the s u r v i v a l of o u t m i g r a t i n g j u v e n i l e sa lmonids are d i s c u s s e d u s i n g s t u d i e s i n t h i s r e g i o n from the l i t e r a t u r e . V . SUMMER PLANKTON DISTRIBUTIONS IN HECATE STRAIT A . INTRODUCTION T h i s chapter i s concerned w i t h the s p a t i a l v a r i a b i l i t y of p l a n k t o n and o ther b i o l o g i c a l parameters w i t h i n one area of the n o r t h e r n s h e l f . Where the p r e v i o u s chapter emphasized temporal and s p a t i a l v a r i a b i l i t y between a r e a s , t h i s chapter focuses on the v a r i a b i l i t y a c r o s s nor thern Hecate S t r a i t d u r i n g summer. As noted i n Chapter 2, Hecate S t r a i t i s an area w i t h eas t-west c o n t r a s t s of p h y s i o g r a p h i c and oceanographic f e a t u r e s . Bathymetry i s most d i s t i n c t , w i t h very sha l low banks on the western s ide ad jacent to the Queen C h a r l o t t e I s l a n d s and a deep t rough on the east p a r a l l e l to the mainland shore (Chapter 2, and F i g . 15). C u r r e n t p a t t e r n s a l s o d i f f e r , w i t h flow predomina te ly n o r t h - s o u t h a long the e a s t e r n s i d e , and a sugges t ion of a gyre over the sha l low western banks ( B e l l 1963). R e c e n t l y , c o n s i d e r a b l e i n t e r e s t has focussed ( rev iewed below) on the a b i l i t y of the t i d e to mix sha l low water columns, and the c o n t r a s t i n g b i o l o g i c a l e f f e c t s such mix ing can have when i t occur s ad j acent to a deeper , more s t r a t i f i e d body of water . With i t s eas t-west ba thymetr i c g r a d i e n t , Hecate S t r a i t i s a good area to examine the i n f l u e n c e of t i d a l mix ing on p l a n k t o n d i s t r i b u t i o n s and o ther b i o l o g i c a l parameter s . The h y p o t h e s i s examined i n t h i s chapter i s tha t ba thymet r i c d i f f e r e n c e s a c r o s s Hecate S t r a i t , combined w i t h t i d a l s t r e a m i n g , generate 101 1 02 FIGURE 15. Ba thymetr ic map of Hecate S t r a i t (depths i n meters) showing l o c a t i o n s of s t a t i o n s on C r u i s e 10 ( s q u a r e s ) , 11 ( c i r c l e s ) , and 14 (diamonds) . Dashed l i n e i n d i c a t e s route of cont inuous t r a n s e c t d u r i n g C r u i s e 15. 1 03 v e r t i c a l l y w e l l - m i x e d c o n d i t i o n s i n western Hecate S t r a i t and r e l a t i v e l y more s t r a t i f i e d c o n d i t i o n s in e a s t e r n Hecate S t r a i t . Such v a r i a t i o n s of v e r t i c a l mix ing then i n f l u e n c e the b i o l o g i c a l c h a r a c t e r i s t i c s , wi th low biomass i n w e l l - m i x e d waters and h i g h biomass at the boundary or f r o n t between the c h a r a c t e r i s t i c mix ing zones . The n u l l h y p o t h e s i s , t h e n , suggests no d i f f e r e n c e i n biomass or b i o l o g i c a l p r o p e r t i e s between deep and sha l low areas of the s t r a i t due to t i d a l m i x i n g . C o n d i t i o n s are examined d u r i n g summer to emphasize the mixed and s t r a t i f i e d reg imes . The m a j o r i t y of t h i s chapter has a l r e a d y been p u b l i s h e d (Perry et al. 1983). 1 . LITERATURE REVIEW T h i s s e c t i o n b r i e f l y rev iews the b a s i c theory of sha l low sea t i d a l f r o n t s and t h e i r i n f l u e n c e upon b i o l o g i c a l p r o d u c t i o n and d i s t r i b u t i o n s . For g r e a t e r d e t a i l , c o l l e c t i o n s of s p e c i f i c s t u d i e s of c o a s t a l f r o n t s can be found i n Bowman and E s a i a s ( 1 977) and Swallow et al . (1981) . The sha l low sea t i d a l f r o n t model was i n i t i a l l y deve loped and a p p l i e d to waters about the B r i t i s h I s l e s , e s p e c i a l l y the r e l a t i v e l y sha l low C e l t i c Sea where f reshwater runof f e f f e c t s are m i n i m a l . The model was proposed by Simpson and Hunter (1974) and l a t e r e l a b o r a t e d by Simpson et al. (1978) and P ingree (1978). I t i d e n t i f i e s w e l l - m i x e d and s t r a t i f i e d water masses i n a g iven area separa ted by a r e l a t i v e l y sharp d i s c o n t i n u i t y or f r o n t . The C e l t i c Sea w i l l serve as an example. I n c r e a s i n g s o l a r 1 04 r a d i a t i o n from s p r i n g to summer warms the sur f ace water s , d e c r e a s i n g i t s d e n s i t y and i n c r e a s i n g i t s buoyancy. As wind s t r e n g t h d e c l i n e s , a stage w i l l be reached where the water column can be model led as a t w o - l a y e r system, w i t h a s u r f a c e wind-mixed l a y e r of depth h and d e n s i t y p , , o v e r l y i n g a near-bot tom t i d a l l y mixed l a y e r of denser water ( p 3 ) , s epara ted by a p y c n o c l i n e (or o f t en a t h e r m o c l i n e ) . However, in an ad jacent area which i s s u f f i c i e n t l y s h a l l o w , the a c t i o n of sur f ace winds and bottom t i d a l c u r r e n t s w i l l e v e n t u a l l y o v e r l a p , d i s r u p t i n g the p y c n o c l i n e and c a u s i n g mix ing from sur f ace to bottom w i t h a mean d e n s i t y p 2 . I f such mixed and s t r a t i f i e d r e g i o n s occur in p r o x i m i t y , they must be separa ted by a d i s c o n t i n u i t y , or f r o n t , which can be v i s u a l i z e d as an u p t u r n i n g of the p y c n o c l i n e (or t h e r m o c l i n e ) . The s i t u a t i o n as d e s c r i b e d i s diagrammed i n F i g . 16. < D i s r e g a r d i n g the su r f ace wind s t r e s s and assuming the sur f ace heat f l u x , which i n c r e a s e s the buoyancy, i s c o n s t a n t over the a rea be ing c o n s i d e r e d , combina t ions of t i d a l v e l o c i t y and water depth p r o d u c i n g mixed and s t r a t i f i e d regimes can be i d e n t i f i e d u s i n g a s t r a t i f i c a t i o n parameter (S; P ingree 1978): h S = L o g 1 0 C~j f r r p where h i s the water d e p t h , a bottom drag c o e f f i c i e n t and |0| the magnitude of the t i d a l stream v e l o c i t y averaged over one t i d a l c y c l e . Us ing C , = 0 .0025, the c r i t i c a l va lue of S (u s ing 1 05 H FIGURE 16. Diagram i l l u s t a t i n g the b a s i c s t r u c t u r e of a sha l low sea t i d a l f r o n t (p, < p 2 < p 3 ) . H i s the t o t a l water d e p t h , h the depth of the sur face wind mixed l a y e r ; for f u r t h e r d e t a i l s , see t e x t . cgs u n i t s ) which i n d i c a t e s the presence of a f r o n t i s 1.5, wi th v a l u e s <1.0 r e p r e s e n t i n g w e l l mixed r e g i o n s and S>2.0 w e l l s t r a t i f i e d r e g i o n s . F i e l d s t u d i e s have con f i rmed the p r e d i c t e d l o c a t i o n s of these f r o n t s (P ingree et al . 1978), a l though they may a l t e r p o s i t i o n somewhat wi th the n e a p - s p r i n g t i d a l c y c l e . Such f r o n t a l r e g i o n s a l s o have c h a r a c t e r i s t i c d i s t r i b u t i o n s of p l a n k t o n and n u t r i e n t s d u r i n g summer. P h y t o p l a n k t o n biomass and p r o d u c t i o n w i l l be low on the mixed s i d e of the f r o n t because of low mean l i g h t l e v e l s (due to the g r e a t e r depth of m i x i n g ) , and a l s o low on the s t r a t i f i e d s ide (at l e a s t w i t h i n 1 06 the upper l a y e r s ) due to n u t r i e n t exhaus t ion (P ingree 1978). High p h y t o p l a n k t o n biomass and p r o d u c t i o n i n the t r a n s i t i o n zone between these two r e g i o n s r e s u l t s from a f l u x of n u t r i e n t s a c r o s s the f r o n t and a f avourab le l i g h t regime induced by a sha l low t h e r m o c l i n e . P l a n k t o n c o m p o s i t i o n a l s o d i f f e r s between the three c h a r a c t e r i s t i c r e g i o n s . P ingree et al. (1978) and H o l l i g a n et al . (1984) r e p o r t diatoms c h a r a c t e r i z e the t i d a l l y mixed water s , s m a l l f l a g e l l a t e s are most common i n w e l l s t r a t i f i e d waters (and may form a s u b - s u r f a c e c h l o r o p h y l l maximum), w h i l e the f r o n t a l r e g i o n i s o f t e n composed of m o n o s p e c i f i c blooms of d i n o f l a g e l l a t e s . Zooplankton were noted by H o l l i g a n et al. (1984) to have t h e i r l a r g e s t biomass i n s t r a t i f i e d water s , a l t h o u g h i t i s not c l e a r to what extent t h i s was due to avo idance of the d i n o f l a g e l l a t e bloom in the f r o n t a l r e g i o n . These au thor s f u r t h e r suggest the c h a r a c t e r i s t i c mix ing zones may g ive r i s e to d i f f e r e n t food webs, wi th the l a r g e s t p r o p o r t i o n of carbon r e s i d i n g i n the p h y t o p l a n k t o n i n mixed water s , but i n the z o o p l a n k t o n , supplemented by b a c t e r i a and p r o t o z o a , i n s t r a t i f i e d water s . F loodga te et al. (1981) noted maximum copepod abundance at the f r o n t i t s e l f and suggested z o o p l a n k t o n may i n i t i a l l y be advec ted to the f r o n t by the a s s o c i a t e d convergent c i r c u l a t i o n p a t t e r n s , where they would then grow at an a c c e l e r a t e d r a te by f eed ing on the h i g h e r b iomass . The width of the f r o n t a l t r a n s i t i o n zone can v a r y , be ing sharp and w e l l - d e f i n e d about the B r i t i s h I s l e s (P ingree et 1 07 al. 1978) but r a t h e r e x t e n s i v e among the i s l a n d s of the southern S t r a i t of G e o r g i a , B . C . , depending on such f a c t o r s as l o c a l runof f and l i g h t e x t i n c t i o n p r o p e r t i e s (Parsons et al. 1983). S e v e r a l s t u d i e s have a p p l i e d t h i s sha l low sea f r o n t a l model to areas o ther than the B r i t i s h I s l e s , i n c l u d i n g areas w i t h c o n s i d e r a b l e f reshwater i n f l u e n c e . G a r r e t t et al. (1978) deve loped e s s e n t i a l l y the same model for the Bay of Fundy and G u l f of Maine , w h i l e G r i f f i t h s et al. (1981) a p p l i e d the Simpson and Hunter (1974) model to Hudson Bay. S u c c e s s f u l a p p l i c a t i o n of the model and i t s importance to p l a n k t o n p r o d u c t i o n i n major e s t u a r i e s was r e p o r t e d by Bowman and E s a i a s (1981) and Bowman et al. (1981) for Long I s l a n d Sound, and by Parsons et al. (1981) for the S t r a i t of G e o r g i a , where p r i n c i p a l zones of mix ing were l o c a t e d among the i s l a n d passages at the n o r t h e r n and southern ends . The t i d a l mix ing model has a l s o been a p p l i e d s u c c e s s f u l l y to the s h e l f seas about New Zealand (Bowman et al. 1983). The importance of c o a s t a l f r o n t s to h i g h e r t r o p h i c l e v e l s , e s p e c i a l l y as areas of c o n c e n t r a t e d food s o u r c e s , has a l s o been i n v e s t i g a t e d . An e x t e n s i v e study of p h y s i c a l - b i o l o g i c a l i n t e r a c t i o n s i n the B e r i n g Sea ( Iverson et al. 1979) found a s e r i e s of t h r e e f r o n t s (one a s h e l f break f r o n t ) d i v i d i n g the s h e l f i n t o three zones . The mixed inner s h e l f supported l a r g e s t o c k s of b e n t h i c fauna and demersal f i s h w h i l e the deeper , outer s h e l f r e g i o n supported p r i m a r i l y p e l a g i c f i s h s t o c k s . Large a g g r e g a t i o n s of sea b i r d s a long these f r o n t s have a l s o been noted (Schneider 1982). Feed ing by marine mammals at t i d a l 108 convergences i n e a s t e r n Canada has a l s o been c i t e d by Gask in (1976) . O b s e r v a t i o n s tha t f r o n t s may i n f l u e n c e c i r c u l a t i o n p a t t e r n s l e d l i e s and S i n c l a i r (1982) to suggest tha t they may h y d r o d y n a m i c a l l y " e n c l o s e " bodies of water and reduce d i s p e r s a l of h e r r i n g l a r v a e i n the G u l f of S t . Lawrence, thus m a i n t a i n i n g the i n t e g r i t y of i n d i v i d u a l spawning s t o c k s . B. METHODS Data for t h i s s tudy were o b t a i n e d by the Imperial Tofino on r o u t i n e s h i p of o p p o r t u n i t y c r u i s e s . The area of n o r t h e r n Hecate S t r a i t between P r i n c e Rupert and Sandsp i t was covered c o n s i s t e n t l y on almost every c r u i s e , p r o v i d i n g rea sonab le temporal and s p a t i a l c o v e r a g e . In a d d i t i o n , i t i s an area of open water and not h i g h l y i n f l u e n c e d by l o c a l events such as r u n o f f . Methods for t h i s study are those d e s c r i b e d i n Chapter 3. Due to the c o v a r i a t i o n of n u t r i e n t c o n c e n t r a t i o n s , r e s u l t s are r e p o r t e d for n i t r a t e and n i t r i t e o n l y . Mixed and s t r a t i f i e d r e g i o n s were determined for Hecate S t r a i t and Dixon Entrance u s i n g the Simpson-Hunter s t r a t i f i c a t i o n parameter S ( d e f i n e d above) . T i d a l c u r r e n t v e l o c i t i e s were o b t a i n e d from a t w o - d i m e n s i o n a l , depth averaged n u m e r i c a l t i d a l model c a l c u l a t e d to p r e d i c t o i l s p i l l movements for the K i t i m a t P i p e l i n e P r o j e c t (Kinney et al. 1976). The model i n c l u d e s Hecate S t r a i t and Dixon Entrance between 5 2 ° N and 5 5 ° N , and 128°W and 133°W u s i n g a g r i d network wi th 9.3 km (5 n a u t i c a l 109 m i l e ) s p a c i n g . I n t e r p o l a t i o n s of t i d e t a b l e data were r e q u i r e d a c r o s s the open s i d e s of the model i n Queen C h a r l o t t e Sound, Dixon E n t r a n c e , and C l a r e n c e S t r a i t at the southern end of the Ala skan a r c h i p e l a g o . The t i d a l component c a l c u l a t e d i n the model i s the M 2 t i d e w i t h a p e r i o d of 12.42 h o u r s . The s t r a t i f i c a t i o n parameter was c a l c u l a t e d u s ing h as the mean water depth fo r each of the t i d e mode l ' s 9.3 km g r i d squares (averaged from Canadian Hydrograph ic c h a r t no. 3002). The bottom drag c o e f f i c i e n t was assumed to be 0 .0025, and the mean t i d a l speed ( 0 ) was averaged over the t i d a l c y c l e for each g r i d p o s i t i o n r e g a r d l e s s of d i r e c t i o n . To v e r i f y the e x i s t e n c e of w e l l - m i x e d and s t r a t i f i e d zones p r e d i c t e d by t h i s equa t ion i n d e p e n d e n t l y of t i d a l c u r r e n t and depth measurements, the bulk s t r a t i f i c a t i o n of the sur f ace l a y e r was c a l c u l a t e d for Hecate S t r a i t and Dixon E n t r a n c e . Bulk s u r f a c e s t r a t i f i c a t i o n was d e f i n e d as the d i f f e r e n c e of a f c between the sur f ace and 50 m or the bottom (whichever was l e s s ) , expres sed as Aa f c nr 1 . These data were o b t a i n e d from the Mar ine E n v i r o n m e n t a l Data S e r v i c e of F i s h e r i e s and Oceans Canada, and c o n s i s t e d of v e r t i c a l p r o f i l e s of temperature and s a l i n i t y c o l l e c t e d in Dixon Ent rance and Hecate S t r a i t d u r i n g summer from 1954 to 1971. They are par t of the same data set used i n Chapter 4 for c a l c u l a t i o n of the su r f ace mixed l a y e r d e p t h . 1 10 C . RESULTS 1. TIDAL MODEL T i d a l e l l i p s e s for Hecate S t r a i t and Dixon Entrance computed by the t i d e model are redrawn from Kinney et al . (1976) i n F i g . 17. These e l l i p s e s r epre sent the movement of a p a r c e l of water over one t i d a l c y c l e i n the absence of a r e s i d u a l c u r r e n t . The l i n e a r l y d i r e c t e d t i d a l c u r r e n t s i n e a s t e r n Hecate S t r a i t and the c i r c u l a r l y d i r e c t e d c u r r e n t s i n the west are c l e a r l y i n d i c a t e d . La rge s t e l l i p s e s (computed c u r r e n t s up to 0.75 m s " 1 ) occur o f f the nor thea s t coas t of Graham I s l a n d . I t must be emphasized tha t these are e s t imated averages computed for a 9.3 km g r i d s p a c i n g . Thomson (1981) has noted t h e r e can be c o n s i d e r a b l e d i s t o r t i o n of t i d a l streams near broken s h o r e l i n e s i n the a r e a , which would be too smal l for i n c l u s i o n i n t h i s model . Any sharp , l o c a l i z e d d i s c o n t i n u i t y of bathymetry would s i m i l a r l y not be r e p r e s e n t e d . Comparison of these t i d a l e l l i p s e s w i t h the bathymetry ( F i g . 15) shows the g r e a t e s t t i d a l c u r r e n t v e l o c i t i e s occur over the s h a l l o w e s t banks of Hecate S t r a i t . C a l c u l a t i o n of the s t r a t i f i c a t i o n parameter for Hecate S t r a i t and Dixon Entrance a l s o i n d i c a t e s t h i s to be a r e g i o n of i n t e n s e m i x i n g , surrounded by a t r a n s i t i o n zone (S between 1 and 2) of v a r y i n g w i d t h , whereas the remainder of the s t r a i t i s p o t e n t i a l l y s t r a t i f i e d d u r i n g summer ( F i g . 18) . Sharpest h o r i z o n t a l g r a d i e n t s of v e r t i c a l mix ing c h a r a c t e r i s t i c s shou ld occur between Dixon 111 )C $ « i « I t i « • * I X X X. * . X. K- V-GRAHAM ISLAND \SKEENA RIVER MORESBY ISLAND Q ^ * * • K X FIGURE 17. T i d a l c u r r e n t e l l i p s e s computed from the o i l s p i l l d r i f t p r e d i c t i o n model for Hecate S t r a i t and Dixon E n t r a n c e . Redrawn w i t h p e r m i s s i o n a f t e r Kinney et al . (1976) . 1 12 FIGURE 18. C a l c u l a t i o n s of the Simpson - Hunter s t r a t i f i c a t i o n parameter , w i t h h the depth of the water , 0 the t i d a l c u r r e n t v e l o c i t y averaged over one t i d a l c y c l e (both cgs u n i t s ) , and a drag c o e f f i c i e n t (Cd ) of 0 .0025. V a l u e s for s t r a t i f i e d , t r a n s i t i o n a l , and mixed zones are from Pingree (1978) . Dots repre sent data l o c a t i o n s ; dashed l i n e r e p r e s e n t s the S=1.5 c o n t o u r . 1 1 3 E n t r a n c e and Hecate S t r a i t , and between Graham I s l a n d and Chatham Sound, c o i n c i d i n g c l o s e l y w i t h marked changes of ba thymetry . T h i s l a t t e r g r a d i e n t shou ld a l s o be s t rengthened by the seaward e s t u a r i n e flow induced by the Skeena R i v e r . These are the l o c a t i o n s where f r o n t s are expec ted , be ing the boundary between w e l l - m i x e d and s t r a t i f i e d water masses. For comparison w i t h the Simpson-Hunter s t r a t i f i c a t i o n parameter , bulk sur f ace s t r a t i f i c a t i o n v a l u e s are grouped i n t o the same 9.3 km squares used for the t i d a l c a l c u l a t i o n s ( F i g . 19) . A l t h o u g h the sampl ing d e n s i t y i s much l e s s than that used for the t i d a l s t r a t i f i c a t i o n , there i s a rea sonab le comparison w i t h mixed and s t r a t i f i e d r e g i o n s . Bulk s t r a t i f i c a t i o n va lue s over sha l low western Hecate S t r a i t are l e s s than 0.01 a f c u n i t s nr 1 i n d i c a t i n g w e l l mixed c o n d i t i o n s , whereas e a s t e r n Hecate S t r a i t i s more s t r a t i f i e d w i t h va lue s g r e a t e r than 0.03 a f c u n i t s m " 1 . As w i t h the t i d a l model , the sharpes t g r a d i e n t of su r f ace s t r a t i f i c a t i o n occur s i n n o r t h e r n Hecate S t r a i t . The i n f l u e n c e of the Skeena R i v e r i s a l s o c l e a r , w i t h the s u r f a c e s t r a t i f i c a t i o n of e a s t e r n Dixon Ent rance w e l l over 10 a f c u n i t s m~ 1 and the contour l i n e s i n d i c a t i n g the g e n e r a l northward and westward f low. C o r r e l a t i o n s of the two measures of s t r a t i f i c a t i o n for the g r i d squares i n which they c o i n c i d e are modera te ly l a r g e and s i g n i f i c a n t (p<0.05) except for J u l y , and are shown i n Tab le V I I . 1 1 4 FIGURE 19. Bulk s t r a t i f i c a t i o n , the at d i f f e r e n c e from the sur f ace to the bottom or 50 m (whichever i s l e s s ) n o r m a l i z e d per meter , for Hecate S t r a i t and Dixon E n t r a n c e . Data p re sen ted are a composi te of June, J u l y and August c a l c u l a t e d from temperature and s a l i n i t y measurements from 1954 to 1971. Dots repre sent s t a t i o n l o c a t i o n s . 1 1 5 TABLE V I I . C o r r e l a t i o n of bulk sur f ace s t r a t i f i c a t i o n (Aat from sur f ace to 50 m or the bottom) w i t h the t i d a l s t r a t i f i c a t i o n parameter (S) for g r i d squares i n which they c o i n c i d e . S i g n i f i c a n c e r e p r e s e n t s the p r o b a b i l i t y of the c o r r e l a t i o n c o e f f i c i e n t be ing equa l to z e r o . JUNE TO JUNE JULY AUGUST AUGUST INCLUSIVE C o r r e l a t i o n C o e f f . 0.37 S i g n i f i c a n c e 0.00 Number of O b s e r v a t i o n s 168 2. BIOLOGICAL DISTRIBUTIONS S t a t i o n s o c c u p i e d by the Tofino on t r a n s e c t s a c ro s s Chatham Sound and n o r t h e r n Hecate S t r a i t are shown i n F i g . 15. A s i m i l a r t r a n s e c t was repea ted on a l l three c r u i s e s w i t h o c c a s i o n a l s t a t i o n s i n Dixon Entrance and o f f Banks I s l a n d i n e a s t e r n Hecate S t r a i t . Data from the t r a n s e c t s are p r e s e n t e d i n F i g s . 20 to 23, w i t h s t a t i o n numbers a l i g n e d so tha t d i s t a n c e s are comparable between a l l c r u i s e s . C r u i s e 10 (June 1979) has been d i v i d e d i n t o two t r a n s e c t s , a n o r t h e r n t r a n s e c t from Chatham Sound and Sandsp i t ( F i g . 20) , and a c e n t r a l t r a n s e c t from Sandsp i t back to P r i n c e Rupert at the mouth of the Skeena R i v e r ( F i g . 21 ) . On the nothern t r a n s e c t ( F i g . 20) , c o n c e n t r a t i o n s of c h l o r o p h y l l , d i a toms , n i t r a t e , and copepods were lowest i n the w e l l - m i x e d , sha l low western s t r a i t ( F i g . 20C) , and h i g h e r i n the s t r a t i f i e d e a s t e r n s t r a i t . The sharpes t change o c c u r r e d between S t a t i o n s 17 and 15, where 0.40 0.00 86 0.30 0.08 42 0.49 0.00 40 1 1 6. 16 17 15 14 13 FIGURE 20. Data from C r u i s e 10, n o r t h e r n t r a n s e c t from Chatham Sound to S a n d s p i t , June 27, 1979. A . Near s u r f a c e (3 m) c h l o r o p h y l l a (ng L ~ 1 ) , N0 3 +N0 2 (,umol L " 1 ) , diatoms ( l o g 1 0 Number L " 1 ) . B. Near sur f ace copepods , o ther zoop lankton (non-copepod z o o p l a n k t o n ) , s a l i n i t y and t empera ture . C. V e r t i c a l dots represent XBT temperature p r o f i l e s ; bathymetry i s approximated from these p r o f i l e s . 1 17 v e r t i c a l s t r a t i f i c a t i o n was f i r s t encountered and sur f ace temperature was lowes t . The decrease of s a l i n i t y a t the easternmost s t a t i o n s r e p r e s e n t s the e f f e c t of the Skeena and Nass R i v e r s i n Chatham Sound. C o m p o s i t i o n a l d i f f e r e n c e s of phytop l ankton o c c u r r e d to the east and west of S t a t i o n 15. Diatoms were <10% (as numbers) of the t o t a l phytop lankton on the s h e l f ( S t a t i o n s 16 and 17), whereas i n deeper water at s t a t i o n s 15, 14 and 13 they comprised 31, 57 and 81% r e s p e c t i v e l y . T a b l e V I I I p r e s e n t s p r o p o r t i o n a l s i m i l a r i t y i n d i c e s for C r u i s e s 10 and 11 c a l c u l a t e d a c c o r d i n g to Rohn and Riggs (1982) u s i n g the number L ~ 1 of c e n t r i c and pennate diatoms at each s t a t i o n . The pane l for C r u i s e 10 ( n o r t h e r n t r a n s e c t ) i n d i c a t e s the s t a t i o n s can be separa ted i n t o two groups , S t a t i o n s 16 and 17 i n the western mixed r e g i o n , and 15, 14 and 13 i n the s t r a t i f i e d r e g i o n . The most common diatom at a l l s t a t i o n s i n the t r a n s e c t was Skeletonema cost at um (<10 Mm d i a m e t e r ) . The c e n t r a l t r a n s e c t of C r u i s e 10 ( F i g . 21) resembled the n o r t h e r n t r a n s e c t . Maximum c o n c e n t r a t i o n s of c h l o r o p h y l l and diatoms o c c u r r e d i n the s t r a t i f i e d waters of c e n t r a l Hecate S t r a i t ad j acent to the western mixed r e g i o n . 5. cost at um was aga in the n u m e r i c a l l y dominant p h y t o p l a n k t o n group , a l t h o u g h the c o m p o s i t i o n of diatoms v a r i e d a l o n g the t r a n s e c t (low p r o p o r t i o n a l s i m i l a r i t y between S t a t i o n s 16 and 19, see Tab le V I I I ) . The i n f l u e n c e of the Skeena R i v e r was apparent at the e a s t e r n end of the t r a n s e c t from low s a l i n i t y and h i g h n i t r a t e 1 18 TABLE V I I I . P r o p o r t i o n a l s i m i l a r i t y of s t a t i o n s based on t h e i r c e n t r i c and pennate diatom c o m p o s i t i o n s u s i n g the s ample - s i ze independent index of Kohn and Riggs (1982): PS. = 1-0.5 I s , IP . - P . I i i = 1 ' x, i y t1 where Pxi i s the p r o p o r t i o n of taxonomic group /' i n sample x, s i m i l a r l y w i t h Pyi for sample y, and s i s the t o t a l number of taxonomic c a t e g o r i e s . CRUISE 10 (NORTH) - DIATOMS STN 17 15 14 13 16 0.59 0.46 0.45 0.51 17 0.48 0.54 0.45 15 0.73 0.86 14 0.81 CRUISE 10 (CENTRAL) - DIATOMS STN 17 18 19 16 0.59 0.46 0.23 17 0.56 0.40 18 0.34 CRUISE 11 - DIATOMS STN 16 15 14 13 17 0.38 0.30 0.29 0.09 16 0.47 0.41 0.05 15 0.69 0.34 14 0.34 1 1 9 21 101 ~> 16 17 18 19 STATION NUMBER FIGURE 21. C r u i s e 10, c e n t r a l t r a n s e c t from Sandsp i t to P r i n c e R u p e r t , 28 June 1979. D e t a i l s of A, B, C as for F i g . 20. 120 c o n c e n t r a t i o n s . In J u l y 1979 ( C r u i s e 11, F i g . 22) , d iatom and c h l o r o p h y l l c o n c e n t r a t i o n s were lower than the p r e v i o u s month. N i t r a t e remained low throughout the s u r f a c e waters of Hecate S t r a i t , except i n Chatham Sound near the Skeena R i v e r . A s t r o n g thermal f r o n t a p p a r e n t l y o c c u r r e d at the edge of the western s h e l f ( F i g . 22C) c o n s i d e r i n g the p r e v i o u s month's v e r t i c a l temperature d i s t r i b u t i o n for the western s t r a i t . Diatoms compr i sed 26% of the t o t a l number of p h y t o p l a n k t o n at S t a t i o n 15, 39% i n the Skeena R i v e r out f low ( S t a t i o n 13), and 10% at a l l o ther s t a t i o n s . S t a t i o n s 14 and 15 i n c e n t r a l and east Hecate S t r a i t were most s i m i l a r i n terms of t h e i r d iatom c o m p o s i t i o n , whereas S t a t i o n s 17 and 13, at o p p o s i t e ends of the t r a n s e c t , were l e a s t s i m i l a r (Table V I 1 1 ) . Data from e a r l y June 1980 ( C r u i s e 14, F i g . 23) i n d i c a t e d that c h l o r o p h y l l and copepods were h i g h i n e a s t e r n Hecate S t r a i t , a l t h o u g h peak c o n c e n t r a t i o n s d i d not occur at the same s t a t i o n . The n u m e r i c a l l y dominant copepods in Hecate S t r a i t were the same as d u r i n g C r u i s e 10 i n June 1979. Acartia longiremus and Centropages abdomi nali s compr i sed over 90% of the t o t a l number of copepods i d e n t i f i e d from the s t a t i o n s near the f r o n t a l r e g i o n on these two c r u i s e s (data i n Perry et al . 1981). Non-copepod zooplankton were not abundant except i n June 1979 ( C r u i s e 10) and 1980 ( C r u i s e 14) near the Queen. C h a r l o t t e I s l a n d s . In 1979, decapod l a r v a e dominated w i t h over 1100 i n d i v i d u a l s m~ 3 (97% of the t o t a l noncopepod z o o p l a n k t o n ) , 121 150 I  17 16 15 14 13 STATION NUMBER FIGURE 22. C r u i s e 11, 24 J u l y 1979. D e t a i l s of A , B, C as for F i g . 20. 1 22 150 I 20 21 22 19 18 26 STATION NUMBER FIGURE 23. C r u i s e 14, 2-4 June 1980. D e t a i l s of A , B, C as for F i g . 20. 123 whereas i n 1980 brachyuran zoea were most abundant (98% by number) . Brachyuran zoea were s t i l l a s i g n i f i c a n t component of the non-copepod zoop lankton (35% by number) at S t a t i o n 19 on the edge of the western s h e l f in 1980. F i g u r e 24 p re sent s c o n t i n u o u s measurements of h o r i z o n t a l c h l o r o p h y l l f l u o r e s c e n c e , t empera ture , and approximate bathymetry a c r o s s c e n t r a l Hecate S t r a i t for C r u i s e 15 (August 1980). C h l o r o p h y l l f l u o r e s c e n c e was roughly i n v e r s e l y r e l a t e d to bathymetry and sur face tempera ture , be ing low over the western s h e l f and h i g h e r to the e a s t . The v e r t i c a l temperature d i s t r i b u t i o n shows the i n c r e a s e i n f l u o r e s c e n c e was c o i n c i d e n t w i t h the onset of v e r t i c a l s t r a t i f i c a t i o n . Note the two major peaks of f l u o r e s c e n c e appear to c o r r e s p o n d to s l i g h t l y warmer sur f ace temperatures and i n c r e a s e s i n the water d e p t h . A c o n t i n u o u s t r a n s e c t of c h l o r o p h y l l f l u o r e s c e n c e i n June 1980, f o l l o w i n g the same r o u t e , p re sented s i m i l a r r e s u l t s . F l u o r e s c e n c e was low over the western s h e l f , peaked at the western edge of the deep t r o u g h , then dropped s h a r p l y and remained low to the east of the t r o u g h . The problem of smearing and the i n a b i l i t y to r e s o l v e s m a l l s p a t i a l f e a t u r e s in h o r i z o n t a l t r a n s e c t s u s i n g a seachest i n t a k e system ( d i s c u s s e d i n S e c t i o n I I I . 9 . ) have been avo ided i n the p r e s e n t a t i o n of these t r a n s e c t s . T y p i c a l l y , s h i p ' s speed was 20 km h " 1 (10 k n o t s ) , and w i t h a d i g i t i z i n g i n t e r v a l of 3 min t h i s r e p r e s e n t s a s p a t i a l i n t e r v a l of 0 .9 km (0.5 n a u t i c a l m i l e s ) , w i t h i n the r e s o l u t i o n of such a system. 1 24 131'46 W 131' 35 W 131'18'W 131'09'W 130' 59' W 130' 42 W 130' 36 W Sandspit K.lkatla ' 1 1 1 1 1 1 1 1 1 10 20 30 40 50 60 70 80 90 R A N G E ( K m ) FIGURE 24. C r u i s e 15, 30 August 1980. Cont inuous t r a n s e c t from S a n d s p i t , Queen C h a r l o t t e I s l a n d s , to K i t k a t l a , i n d i c a t e d on F i g . 15. Top : near sur face (3 m) tempera ture . M i d d l e : near su r f ace r e l a t i v e f l u o r e s c e n c e . Bottom: v e r t i c a l temperature s t r u c t u r e ( ° C ) from XBT p r o f i l e s ( v e r t i c a l dots ) and the approximate ba thymetry . 125 D. DISCUSSION O b s e r v a t i o n s in Hecate S t r a i t i n 1979 and 1980 are c o n s i s t e n t w i t h the l o c a t i o n s of mixed and s t r a t i f i e d water masses p r e d i c t e d by the Simpson-Hunter s t r a t i f i c a t i o n parameter ( F i g . 18) . V e r t i c a l temperature p r o f i l e s i n d i c a t e mixed c o n d i t i o n s over the sha l low western s t r a i t and s t r a t i f i e d c o n d i t i o n s to the e a s t . C h l o r o p h y l l c o n c e n t r a t i o n s and diatom numbers are lowest in the mixed r e g i o n , h i g h e r i n the s t r a t i f i e d r e g i o n , but h i g h e s t i n the c e n t r a l s t r a i t w i t h the onset of v e r t i c a l s t r a t i f i c a t i o n . T h i s i s the t r a n s i t i o n zone and i s expected to have the h i g h e s t p h y t o p l a n k t o n biomass a c c o r d i n g to the t i d a l f r o n t model . Cont inuous t r a n s e c t s of n e a r - s u r f a c e f l u o r e s c e n c e i n June and August 1980 show sharp changes of f l u o r e s c e n c e and temperature a c r o s s Hecate S t r a i t which are l i k e l y to i n d i c a t e l o c a t i o n s of f r o n t s w i t h i n t h i s t r a n s i t i o n zone . Zooplankton p a r a l l e l the p a t t e r n for p h y t o p l a n k t o n except for the l a r g e numbers of decapod and crab l a r v a e sampled i n June near the Queen C h a r l o t t e I s l a n d s . These may be remnants of the s p r i n g bloom, which presumably had d i s p e r s e d or s e t t l e d to the bottom by midsummer. In t h i s r e g i o n , c rab l a r v a e are known to become f ree swimming d u r i n g A p r i l , wi th the l a r v a l stage l a s t i n g about four months ( B u t l e r 1956). The correspondence between f i e l d data and p r e d i c t e d mix ing c h a r a c t e r i s t i c s i s found even wi thout c o n s i d e r i n g the e f f e c t s of 1 26 f reshwater i n p u t . The t i d a l f r o n t model assumes the sur f ace buoyancy f l u x i s due s o l e l y to sur f ace h e a t i n g , but f reshwater a l s o i n c r e a s e s the buoyancy of the sur f ace l a y e r and reduces the e f f e c t of bottom m i x i n g . Hecate S t r a i t i s i n f l u e n c e d by f reshwater i n summer, e s p e c i a l l y from the Skeena R i v e r i n the n o r t h and to a l e s s e r extent a long the main land shore to the e a s t . As noted i n the i n t r o d u c t i o n to t h i s c h a p t e r , the t i d a l f r o n t model does app ly to a reas where s a l i n i t y e f f e c t s are i m p o r t a n t , a l t h o u g h i t may s h i f t the c r i t i c a l va lue of S. In t h e i r s tudy i n the G u l f of S t . Lawrence, l i e s and S i n c l a i r (1982) noted the parameter may i n d i c a t e r e l a t i v e degrees of mix ing i n areas wi th c o n s i d e r a b l e f reshwater i n f l u e n c e r a t h e r than p r e c i s e l o c a t i o n s of f r o n t s . Freshwater added to e a s t e r n Hecate S t r a i t would serve to emphasize the e f f e c t of s t r a t i f i c a t i o n , r a t h e r than dampen the t i d a l mix ing e f f e c t which i s dominant over western Hecate S t r a i t . However, there are two important a spec t s of the data which are not c o n s i s t e n t w i t h the sha l low sea t i d a l f r o n t model as p r e s e n t e d i n the l i t e r a t u r e . Near s u r f a c e temperatures were c o n s i s t e n t l y h i g h e r on the w e l l - m i x e d western s h e l f than i n e a s t e r n Hecate S t r a i t , o f t en w i t h a minimum in c e n t r a l Hecate S t r a i t at the s t a t i o n s i n the f r o n t a l zone ; and n i t r a t e p l u s n i t r i t e c o n c e n t r a t i o n s on the western mixed s i d e were u n u s u a l l y low for a t y p i c a l t i d a l f r o n t (see P i n g r e e 1978; P ingree et al . 1978). 1 27 The s imple s t e x p l a n a t i o n for these d i s c r e p a n c i e s i s the very sha l low depth of western Hecate S t r a i t . Most of t h i s r e g i o n i s c o n s i d e r a b l y l e s s than 30 m, and w e l l - m i x e d from s u r f a c e to bottom a c c o r d i n g to the v e r t i c a l temperature p r o f i l e s . Tabata (1958) , in a study of the annual heat budget about T r i p l e I s l a n d in e a s t e r n Dixon E n t r a n c e , has e s t i m a t e d that heat ga ined by the sea i n summer would be s u f f i c i e n t to r a i s e the temperature of a 50 m water column by 0 . 8 ° C per month i f a d v e c t i v e e f f e c t s were n e g l e c t e d . In western Hecate S t r a i t , t h i s amounts to c o n t i n u a l l y h e a t i n g the e n t i r e water column, whereas ea s t e rn Hecate S t r a i t would exper ience mix ing of c o o l e r , deeper water i n t o the s t r a t i f i e d l a y e r w i t h the passage of o c c a s i o n a l s torms . Lower temperatures may a l s o r e s u l t w i t h the a d d i t i o n of runof f from the mainland shore . N u t r i e n t c o n c e n t r a t i o n s in western Hecate S t r a i t are low because e i t h e r the r e g i o n has low n u t r i e n t s a l l y e a r , or becomes d e p l e t e d before summer and remains so u n t i l f a l l . Data i n D i l k e et al . (1979) and P e r r y et al. (1981) r and p r e s e n t e d i n Chapter 4, show that n i t r a t e p l u s n i t r i t e c o n c e n t r a t i o n s i n western Hecate S t r a i t i n w i n t e r (January 1979, February 1980) are between 10 and 20 jtxM N 0 3 , d e c r e a s i n g to l e s s than 3 M M N 0 3 - N d u r i n g the s p r i n g bloom. T h i s r u l e s out the f i r s t p o s s i b i l i t y , and i t i s t h e r e f o r e suggested ambient n i t r a t e c o n c e n t r a t i o n s remain low i n summer due to r a p i d uptake by p h y t o p l a n k t o n . T h i s shou ld r e s u l t i n i n c r e a s e d p h y t o p l a n k t o n (or zoop lankton) b iomass . However, as measured biomass was low i n the western 128 s t r a i t , n u t r i e n t supply to t h i s r e g i o n must be l i m i t e d , p robab ly by the sha l low depth of the s h e l f and the presence of Graham I s l a n d . The u sua l t i d a l mix ing model , however, suggests p h y t o p l a n k t o n biomass w i l l be low on the mixed s ide because of lower mean l i g h t i n t e n s i t i e s r e s u l t i n g from deeper v e r t i c a l m i x i n g . To determine whether p h y t o p l a n k t o n i n western Hecate S t r a i t are l i k e l y to be l i g h t l i m i t e d , the c r i t i c a l depth was c a l c u l a t e d . The e q u a t i o n f o l l o w e d Parsons et al. (1984), wi th I 0 (1784 J c m " 2 d" 1 ) the normal i n c i d e n t s o l a r r a d i a t i o n fo r June at Sandsp i t c o r r e c t e d for su r f ace r e f l e c t i o n due to sun angle (see Appendix I I ) , and the a t t e n u a t i o n c o e f f i c i e n t (k) determined as the mean of 1.45/Z (Walker 1980), where Z was s s the Secch i d i s k depth measured i n western Hecate S t r a i t d u r i n g June (seven measurements: S t r i c k l a n d 1958, P . O . G . 1959, 1962). The compensation l i g h t i n t e n s i t y (I = 58 J c m " 2 d " 1 , Hobson 1981) was the same as used i n Chapter 4. With a mean a t t e n u a t i o n c o e f f i c i e n t of 0.178 m" 1 the c a l c u l a t e d c r i t i c a l depth for western Hecate S t r a i t i n June was 83 m, wi th a s t andard d e v i a t i o n of 34 m based on v a r i a t i o n i n Secch i depth measurements. Data for J u l y i n d i c a t e s i m i l a r d e p t h s . T h i s i s c o n s i d e r a b l y deeper than the depth of the- western s h e l f and suggests phytop l ankton w i l l not be l i g h t l i m i t e d i n t h i s r e g i o n . I t i s a l s o c o n s i s t e n t w i t h the o b s e r v a t i o n tha t i n very sha l low env i ronment s , h i g h mix ing may not l e a d to l i g h t l i m i t a t i o n of p h y t o p l a n k t o n growth (Legendre 1981). 129 T i d a l mix ing t h e r e f o r e appears to be a p l a u s i b l e mechanism for promoting mixed c o n d i t i o n s over the sha l low western r e g i o n of the s t r a i t and s t r a t i f i e d c o n d i t i o n s on the e a s t e r n s i d e . Phytop lankton c o n c e n t r a t i o n s were low in summer i n both these areas as a r e s u l t of n u t r i e n t l i m i t a t i o n . However, n u t r i e n t s may be mixed s p o r a d i c a l l y i n t o the s u r f a c e waters of the s t r a t i f i e d r e g i o n w i t h the passage of l o c a l s torms . For example, the depth of the wind mixed sur face l a y e r can be e s t imated from the equa t ion (Pond and P i c k a r d 1983) D E = 4.3 W ( s i n |0|) where i s the Ekman d e p t h , W the wind speed, and <p the l a t i t u d e . U s i n g a maximum h o u r l y wind speed of 12 m s" 1 r ecorded from o p p o s i t e s i d e s of Hecate S t r a i t (Sandspi t and Mclnnes I s l and) on August 22, 1980 (Atmospheric Environment S e r v i c e 1980), the c a l c u l a t e d wind mixed l a y e r was about 58 m. Such p o t e n t i a l v e r t i c a l mix ing may account for the h i g h e r near- • su r f ace f l u o r e s c e n c e of e a s t e r n Hecate S t r a i t apparent i n F i g . 24. C o n s i d e r i n g the mixed s i d e has low measured n u t r i e n t c o n c e n t r a t i o n s , what s u s t a i n s the h i g h p l a n k t o n biomass i n the f r o n t a l r e g i o n of c e n t r a l Hecate S t r a i t ? One p o s s i b i l i t y i s the e x i s t e n c e of a f r o n t between n o r t h e r n Hecate S t r a i t and Dixon Entrance p a r a l l e l to the r a t h e r s teep bathymetry . Few n u t r i e n t 130 data are a v a i l a b l e from t h i s a r e a , a l t h o u g h t h r e e s t a t i o n s n o r t h of Graham I s l a n d sampled i n J u l y 1979 i n d i c a t e d n i t r a t e p l u s n i t r i t e c o n c e n t r a t i o n s were g r e a t e r than 1-2 M M , whereas c o n c e n t r a t i o n s in Hecate S t r a i t i t s e l f were l e s s than 0.5 yM ( F i g . 22 ) . The t r a n s e c t from Sandsp i t through e a s t e r n Dixon E n t r a n c e to Chatham Sound ( F i g . 20) shows anomalous ly h i g h n i t r a t e at S t a t i o n 15 near Rose S p i t , in the area that f r o n t a l a c t i v i t y might be expec ted . A second p o s s i b l e source of n u t r i e n t s for c e n t r a l Hecate S t r a i t s u r f a c e waters i s e p i s o d i c u p w e l l i n g a l o n g the r a p i d change of bathymetry from the e a s t e r n t rough to the western s h e l f . Such a mechanism has been proposed to account for the h i g h p r o d u c t i v i t y of a f r o n t o f f Nova S c o t i a ( F o u r n i e r et al . 1977), where n u t r i e n t - r i c h s lope water i s advec ted onto the s h e l f at the s h e l f break . Sandstrom and E l l i o t (1984) have e s t i m a t e d that mix ing by s o l i t a r y waves of the i n t e r n a l t i d e at t h i s s h e l f break i s s u f f i c i e n t to supply the r e q u i r e d n u t r i e n t f l u x c a l c u l a t e d by F o u r n i e r et al. (1977). Sandstrom and E l l i o t (1984) f u r t h e r suggest such i n t e r a c t i o n s of the i n t e r n a l t i d e w i t h topography are l i k e l y to occur at o ther s i t e s a long c o n t i n e n t a l she lves and banks . Denman et al. (1981) d e s c r i b e zones of h i g h p h y t o p l a n k t o n biomass and p r o d u c t i v i t y on the c o n t i n e n t a l s h e l f o f f the west coas t of Vancouver I s l a n d . They suggest these zones r e s u l t from a d v e c t i o n of n u t r i e n t - r i c h deep water onto the s h e l f due to the i n t e r a c t i o n of a longshore c u r r e n t s , i n c l u d i n g the C a l i f o r n i a U n d e r c u r r e n t , w i t h the 131 c o m p l i c a t e d bathymetry of the a r e a . Gardner (1981b) i n d i c a t e d that P a c i f i c E q u a t o r i a l Water does occur i n Hecate S t r a i t u s i n g temperature and s a l i n i t y c h a r a c t e r i s t i c s and the o c c u r r e n c e of n o r m a l l y s u b t r o p i c a l zoop lankton s p e c i e s i n 1977. When deep water f lows i n t o the t rough i n e a s t e r n Hecate S t r a i t , i t may be advected onto the western s h e l f by u p w e l l i n g induced by a longshore c u r r e n t , as d e s c r i b e d by Hsueh and O ' B r i e n (1971) and a p p l i e d to the southern Nova S c o t i a n c o a s t l i n e by G a r r e t t and Loucks (1976) . T h i s u p w e l l i n g may be a i d e d by t i d a l mix ing e f f e c t s g e n e r a t i n g a bottom Ekman (wel l -mixed) l a y e r a long the edge of the s h e l f . I t i s i n t e r e s t i n g to s p e c u l a t e on the e f f e c t s a f r o n t a l system i n c e n t r a l Hecate S t r a i t might have on f i s h p r o d u c t i o n . C o n s i d e r i n g the depth of western Hecate S t r a i t , i t i s reasonable to expect s u b s t a n t i a l s ed imenta t ion of upper l a y e r pr imary p r o d u c t i o n to the benthos . The amount of m a t e r i a l tha t w i l l sediment to the bottom depends on the water d e p t h , the depth of s u r f a c e m i x i n g , and the c o n c e n t r a t i o n of b iomass . More m a t e r i a l sediments to the bottom i n sha l low r a t h e r than deep environments ( M i l l s 1980), under sha l low mixed l a y e r depths (Hargrave 1973), and when upper l a y e r pr imary p r o d u c t i o n i s h i g h (Parsons et al. 1977). In western Hecate S t r a i t , c o n s i d e r a b l e biomass c o u l d be expected to sediment to the benthos because of i t s d e p t h . However, d u r i n g summer the p h y t o p l a n k t o n biomass i s e v i d e n t l y low, and mix ing may keep such m a t e r i a l i n suspens ion for some t i m e . 1 32 In the f r o n t a l r e g i o n of the s h e l f break , the above three c r i t e r i a appear to be o p t i m a l . The water depth i s r e l a t i v e l y s h a l l o w , a l tho ugh as the bathymetry changes r a p i d l y i n the eas t -west d i r e c t i o n t h i s depends on l o c a t i o n . Mixed l a y e r depths are sha l lower than over the western s h e l f , r e f l e c t i n g the onset of v e r t i c a l s t r a t i f i c a t i o n , and p h y t o p l a n k t o n biomass i s r e l a t i v e l y h i g h , a l l sugge s t ing the p o s s i b i l i t y of c o n s i d e r a b l e t r a n s f e r of m a t e r i a l to the benthos . Given such a s c e n a r i o , i t i s perhaps not s u r p r i s i n g to f i n d Hecate S t r a i t i s the most p r o d u c t i v e g r o u n d f i s h r e g i o n of the B . C . c o a s t , wi th P a c i f i c cod (Gadus macr oce phal us) the g r e a t e s t p r o p o r t i o n of the c a t c h . Of a l l P a c i f i c cod l anded from Hecate S t r a i t between 1958 and 1978, 83% were caught a long the edge of the western s h e l f at a p p r o x i m a t e l y the 40 m i s o b a t h , and at s i m i l a r depths between Hecate S t r a i t and Dixon E n t r a n c e (S tocker 1981). A p o t e n t i a l energy budget for a system s i m i l a r to that d e s c r i b e d here , i n v o l v i n g sha l low d e p t h s , t i d e and wind m i x i n g , and a deepwater n u t r i e n t s u p p l y , has been o u t l i n e d by Cohen et al. (1982) for Georges Bank. They found that h i g h pr imary p r o d u c t i o n throughout the summer was a b l e to s u s t a i n both h i g h p e l a g i c f i s h p r o d u c t i o n and h i g h demersal f i s h p r o d u c t i o n v i a a pathway through the macro- and m i c r o - b e n t h o s . L i t t l e i s known, however, of the p r o d u c t i v i t y or biomass of b e n t h i c organisms i n Hecate S t r a i t , and whether they might form a l i n k between h i g h p l a n k t o n biomass at the f r o n t and h i g h g r o u n d f i s h p r o d u c t i o n . 1 33 E . SUMMARY D i s t r i b u t i o n s of p l a n k t o n , c h l o r o p h y l l and n u t r i e n t s were examined a c r o s s n o r t h e r n Hecate S t r a i t d u r i n g summer 1979 and 1980 and compared wi th t i d a l mix ing c h a r a c t e r i s t i c s . C a l c u l a t i o n s of the Simpson-Hunter (1974) t i d a l s t r a t i f i c a t i o n parameter (h U " 3 ) i n d i c a t e most of Hecate S t r a i t and Dixon Ent rance are p o t e n t i a l l y s t r a t i f i e d d u r i n g summer i n the absence of e x c e s s i v e wind m i x i n g , w i t h a w e l l - m i x e d r e g i o n over the sha l low s h e l f ad jacent to the Queen C h a r l o t t e I s l a n d s . These mix ing zones were conf i rmed by XBT temperature p r o f i l e s from the Impe r i al Tofino. Plankton d i s t r i b u t i o n s and biomass d i f f e r e d between east and west s i d e s of the s t r a i t , c o n s i s t e n t w i t h p r e d i c t i o n s of the t i d a l mix ing model . Near su r f ace c o n c e n t r a t i o n s of c h l o r o p h y l l a, n u t r i e n t s , d i a toms , and copepods were lower i n the mixed r e g i o n than the s t r a t i f i e d r e g i o n , but h i g h e s t i n the boundary between these two zones . However, c r o s s - s t r a i t n u t r i e n t d i s t r i b u t i o n s and mean l i g h t i n t e n s i t i e s i n the mixed r e g i o n were not c o n s i s t e n t w i t h the t i d a l mix ing mode l . I t i s suggested that low p h y t o p l a n k t o n biomass i n the mixed r e g i o n i s due to n u t r i e n t r a t h e r than l i g h t l i m i t a t i o n , w h i l e s p o r a d i c wind mix ing of the s t r a t i f i e d r e g i o n and p o s s i b l e v e r t i c a l a d v e c t i o n a long the edge of the western s h e l f may support the h i g h e r biomass of the e a s t e r n s ide and at the f r o n t . V I . MECHANISMS OF SEASONAL PLANKTON BLOOMS IN HECATE STRAIT A . INTRODUCTION C o a s t a l r e g i o n s d u r i n g summer are r i c h l y p a t t e r n e d by b i o l o g i c a l , p h y s i c a l , and c h e m i c a l p a t c h i n e s s . Chapter 4 has i n d i c a t e d the B . C . n o r t h e r n s h e l f can have c o n s i d e r a b l e coar se s c a l e b i o l o g i c a l and p h y s i c a l h e t e r o g e n e i t y , e s p e c i a l l y d u r i n g s p r i n g and summer. A consequence of such p a t c h i n e s s i s the presence of b o u n d a r i e s , which may be e i t h e r s t r o n g or weak. R i v e r plumes and t i d a l f r o n t s are examples of s t r o n g boundar ie s which c l e a r l y d i s t i n g u i s h d i f f e r e n t b i o l o g i c a l and p h y s i c a l c h a r a c t e r i s t i c s . Weak boundar ie s can be i d e n t i f i e d wi th u p w e l l i n g zones and the i s l a n d mass e f f e c t ( e . g . Simpson et al. 1982), where the g r a d a t i o n between d i f f e r e n t c h a r a c t e r i s t i c s occur s over l a r g e r s p a t i a l s c a l e s . Coarse s c a l e (10-100 km) p a t t e r n s of p h y s i c a l and b i o l o g i c a l c h a r a c t e r i s t i c s a c r o s s Hecate S t r a i t i n summer were d e s c r i b e d in Chapter 5, w i t h t i d a l mix ing v a r i a t i o n s suggested as the p r i n c i p a l mechanism. T h i s i n t e r a c t i o n of t i d a l m i x i n g and bathymetry must occur in a l l seasons , however, i t s i n f l u e n c e on p l a n k t o n p r o d u c t i o n at t imes o ther than summer has not been wide ly c o n s i d e r e d . In w i n t e r , c o a s t a l seas tend to be w e l l - m i x e d by sea sona l winds and w i t h low p r o d u c t i o n due to inadequate l i g h t i n t e n s i t i e s . D u r i n g s p r i n g , the development of the phytop l ankton bloom depends upon the fo rmat ion of the seasona l t h e r m o c l i n e and e s t a b l i s h m e n t of a 1 34 1 35 sha l low sur f ace mixed l a y e r . P ingree et al . (1976) and Fasham et al . (1983) d e s c r i b e the development of the bloom i n the C e l t i c Sea , which occur s in A p r i l i n areas of weak t i d a l mix ing c o i n c i d e n t w i t h the onset of temperature s t r a t i f i c a t i o n . Throughout the seasona l study by P ingree et al. (1976), no p h y t o p l a n k t o n bloom was observed in t i d a l l y w e l l - m i x e d r e g i o n s , w h i l e Fasham et al. (1983) noted that s i g n i f i c a n t v a r i a t i o n s in the r a t e of development of the bloom c o u l d occur on h o r i z o n t a l s c a l e s of the order of 50 km. However, the q u e s t i o n of whether a bloom w i l l be produced at any time i s not a matter s o l e l y of the i n t e n s i t y of m i x i n g . R a t h e r , i t i s the e f f e c t of such mix ing on the l i g h t and n u t r i e n t s a v a i l a b l e to the p h y t o p l a n k t o n . The t i d a l l y w e l l - m i x e d r e g i o n may e x p e r i e n c e a s p r i n g diatom bloom i f some mechanism e x i s t s which p r o v i d e s h i g h e r l i g h t i n t e n s i t i e s be fore the onset of s ea sona l s t r a t i f i c a t i o n . S i m i l a r i l y , the s t r a t i f i e d r e g i o n may bloom d u r i n g summer i f n u t r i e n t s are added to the sur f ace mixed l a y e r from some e x t e r n a l s o u r c e . In t h i s chap te r I examine the seasona l p a t t e r n s of p h y t o p l a n k t o n biomass , taxonomic c o m p o s i t i o n , and s p a t i a l o r g a n i z a t i o n a c r o s s Hecate S t r a i t , and c o n s i d e r whether the coar se s c a l e d i f f e r e n c e s apparent i n summer (Chapter 5) are m a i n t a i n e d d u r i n g win te r and s p r i n g . P h y s i c a l mechanisms o r g a n i z i n g the observed p a t t e r n s are proposed , and the seasona l importance of t i d a l mix ing v a r i a t i o n s to p l a n k t o n dynamics in Hecate S t r a i t i s d i s c u s s e d . 1 36 B. METHODS Data were c o l l e c t e d as d e s c r i b e d i n Chapter 3, w i t h s t a t i o n l o c a t i o n s for C r u i s e s 12 and 13 i n d i c a t e d on F i g . 25. P h y t o p l a n k t o n abundance e s t imate s have been c o n v e r t e d to a biomass index us ing a r e l a t i v e s i z e c o e f f i c i e n t as d e s c r i b e d in Chapter I V . B . 2 . I d e n t i f i e d taxonomic groups , mean abundances from Hecate S t r a i t samples , and t h e i r r e l a t i v e s i z e c o e f f i c i e n t s for c r u i s e s i n w i n t e r , s p r i n g , and summer are p r e s e n t e d in Tab le IX. His tograms of r e l a t i v e c o m p o s i t i o n of major taxa ( F i g . 28) were c a l c u l a t e d by s e p a r a t i n g s t a t i o n s from each c r u i s e i n t o e a s t e r n and western r e g i o n s based on bathymetry and geographic l o c a t i o n , then c a l c u l a t i n g the weighted biomass percent of tha t taxon in a l l samples from tha t a rea for that c r u i s e . Thus ( a f t e r Mackas and Sef ton 1982) where N i s the number of s t a t i o n s i n that r e g i o n for that c r u i s e , P the number of taxonomic groups , and B.^ the e s t imated biomass index (abundance * s i ze c o e f f i c i e n t ) of taxon / i n sample j . Data for S t a t i o n 24 of C r u i s e 13 ( A p r i l 1979) have been l e f t out of the h i s togram c a l c u l a t i o n s as f l a g e l l a t e counts were i n c o m p l e t e . In o rder to compare taxonomic c o m p o s i t i o n between s t a t i o n s , and to o b t a i n a d i s t a n c e measure of c o m p o s i t i o n fo r use i n the weighted % a l l samples = (L B,. ,- )/ i : ) * 100 FIGURE 25. Hecate S t r a i t bathymetry (depths i n meters) and s t a t i o n l o c a t i o n s for C r u i s e 12 (squares) and C r u i s e 13 ( c i r c l e s ) . Dashed box a c r o s s Hecate S t r a i t i n d i c a t e s the area averaged for the s a t e l l i t e z o n a l IR b r i g h t n e s s s e c t i o n . 1 38 TABLE IX. Phytop lankton taxonomic groups , r e l a t i v e s i z e c o e f f i c i e n t s and mean abundances for C r u i s e s 10 (June 1979), 12 (Feb. 1980) and 13 ( A p r i l 1980). TAXA REL. MEAN ABUNDANCE SIZE per 0 . 1 mL COEF. 1 0 1 2 1 3 Bad er i as I r um delicatula 2.0 0. 1 3 Bi ddul phi a spp. 5.0 - - 0. 06 Cer at aul i na ber goni i 2.5 0. 1 5 -Chaet ocer os spp. (4—15 Mm) 0.9 7. 45 0. 03 40. 30 Chaet ocer os spp. (16-25 um) 2.0 2. 93 - 7. 89 Corethron hystrix 2.5 - - 0. 12 Cos ci nodi s cus spp. 2.5 - 0. 02 0. 68 Cosci nodiscus spp. (>50 Mm) 5.0 - - 0. 12 Di t yl um br i ght we I I i i 4.5 - 0. 01 0. 13 Lauderi a boreal is 3.0 - - 1 . 1 4 Leptocylindrus dani cus 1 .5 - - 0. 09 Melos i r a spp. 3.5 - 0. 07 0. 01 Rhi zos ol eni a delicatula 2.0 0. 85 - 1 . 1 7 R. fragi I i s si ma 3.0 - - 0. 27 R. s e t i ge r a 2.5 0. 25 -R. st ol I erf ot hi i 3.0 0. 04 - 1 . 62 Skeletonema costatum (<10 um) 1.0 12. 26 0. 28 6. 24 S. costatum (>10 um) 3.0 13. 44 - 3. 03 Stephanopyxis palmeriana 5.0 - - 0. 33 Thai assi osi ra spp. (5-20 Mm) 1 .2 0. 1 5 0. 41 1 . 1 1 Thai assi osi ra spp. (21-40 Mm) 3.0 0. 31 0. 17 1 . 38 Thai assi osi ra spp. (41-60 Mm) 5.0 0. 04 - 0. 18 Asterionella japonic a 2.0 0. 04 - 0. 54 Ni t zs chia del i catissima 1 .5 0. 23 0. 04 N. 1 ongi s s ima 2.0 - 0. 09 0. 35 N. pungens 2.0 1. 40 -Thai as sionema ni t zs chi ode s 2.5 0. 1 2 0. 04 0. 59 Ce r at i um l i ne al um 4.5 0. 04 0. 01 Peridi ni um spp . 5.0 - - 0. 38 u n i d . d i n o f l a g e l l a t e s (16-50 Mm) 3.0 0. 1 9 - 0. 25 u n i d . f l a g e l l a t e s (<5 MITO 0.2 55. 25 12. 06 50. 95 u n i d . f l a g e l l a t e s (6-15 um) 1 .0 12. 72 3. 03 13. 21 Dislephanus speculum 2.0 - 0. 01 0. 08 M i c r o z o o p l a n k t o n 3.0 0. 32 0. 04 0. 1 5 1 39 c l u s t e r i n g r o u t i n e . I c a l c u l a t e d a v e r s i o n of the e u c l i d e a n d i s t a n c e d i s s i m i l a r i t y m e t r i c ( O r l o c i 1978, Legendre and Legendre 1979) e(j,k) = [ L. (B.. - B.k )» ]± with B, / , j, k as d e f i n e d be low. However, as d i s c u s s e d by Mackas and Sefton (1982) , to i s o l a t e c o m p o s i t i o n a l p a t c h i n e s s from biomass p a t c h i n e s s i t i s f i r s t necessary to n o r m a l i z e t h i s d i s t a n c e measure to b iomass . T h i s chord d i s t a n c e was c a l c u l a t e d d i r e c t l y by ( O r l o c i 1978) Cij,k) - {2(1-q y J f e / ( q , , ) ± )}* w i t h qJk =Lj B. . Bik , q u =Z. Bj . , and =Z. B ^ where B i s the biomass index , / r e p r e s e n t s each taxon , and j and k r e p r e s e n t the s t a t i o n p a i r s be ing c o n s i d e r e d . In t h i s form, C(j,k) r e p r e s e n t s the n o r m a l i z e d chord d i s t a n c e of taxonomic c o m p o s i t i o n between s t a t i o n s j and k, w i th v a l u e s r a n g i n g from 0 for s t a t i o n p a i r s w i t h i d e n t i c a l p r o p o r t i o n s of biomass i n each t axon , to /2 for complete d i s s i m i l a r i t y . T h i s c h o r d d i s t a n c e measure has the advantage of b e i n g a m u l t i v a r i a t e ana log (Mackas 1984) of the s t r u c t u r e f u n c t i o n for s p a t i a l a u t o c o r r e l a t i o n . Chord d i s t a n c e s were a l s o used to c l u s t e r s t a t i o n s ac ros s time and space on the b a s i s of taxonomic c o m p o s i t i o n . The NT-SYS Numer ica l Taxonomy System of M u l t i v a r i a t e S t a t i s t i c a l Programs 1 40 ( R o h l f , J . F . , J . Ki spaugh and D. K i r k . 1980. Dept . of E c o l o g y and E v o l u t i o n , S ta te U n i v e r s i t y of New Y o r k , Stony Brook, N . Y . ) TAXON r o u t i n e was used for the a n a l y s e s f o l l o w i n g the unweighted p a i r - g r o u p method u s ing a r i t h m e t i c averages (see Sneath and Sokal 1973 for d e t a i l s ) . To e s t imate coar se s c a l e s p a t i a l v a r i a b i l i t y a c r o s s Hecate S t r a i t , I used the s p a t i a l s t r u c t u r e f u n c t i o n c o n c e p t . I t i s a measure of the mean square d i f f e r e n c e of the va lue of a v a r i a b l e at s e v e r a l s p a t i a l s e p a r a t i o n s (see e . g . W y r t k i 1967, Lut jeharms 1981, Deschamps et al . 1981 ) D(h) = 1 Z n [ f(x+h) - f (X) ] 2 where f i s some p r o p e r t y that v a r i e s as a f u n c t i o n of d i s t a n c e X, h i s the s p a t i a l s e p a r a t i o n s c a l e , and n the number of da ta p a i r s at tha t s c a l e . Where the e s t imated s t r u c t u r e f u n c t i o n i s r ea sonab ly f l a t , no s t r o n g s p a t i a l f e a t u r e s would be e x p e c t e d . However, where the s t r u c t u r e f u n c t i o n shows a peak, i t d i s t i n g u i s h e s s p e c i f i c f e a t u r e s or exchanges of energy (Deschamps et al . 1981) at tha t s c a l e . The advantage of u s i n g the s t r u c t u r e f u n c t i o n r a t h e r than s p e c t r a l d e n s i t y curves i s tha t assumptions of s t a t i o n a r i t y and r e g u l a r spac ing of the data are not as r i g o r o u s . Deschamps et al . (1981) recommend d e t r e n d i n g the data before c a l c u l a t i n g s t r u c t u r e f u n c t i o n s i f the f i e l d i s inhomogeneous. The Tofino data show c o n s i s t e n t t rends a c r o s s the s t r a i t which have been removed u s i n g a l e a s t 141 squares l i n e a r f i t . C r i t i c a l d e p t h s , mixed l a y e r d e p t h s , and mean bottom depths were c a l c u l a t e d by month to determine the p h y t o p l a n k t o n growing season s e p a r a t e l y for east and west Hecate S t r a i t . Sur face mixed l a y e r depths were c a l c u l a t e d from o - depth p r o f i l e s c o l l e c t e d on c r u i s e s to the r e g i o n from 1954-1971 f o l l o w i n g the procedure d e s c r i b e d i n Chapter 4. C r i t i c a l depths were a l s o c a l c u l a t e d as d e s c r i b e d i n Chapter 4, u s i n g for I 0 the normal d a i l y s o l a r r a d i a t i o n va lue s for each month as measured at Sandsp i t a i r p o r t . C . RESULTS 1. FIELD DATA Chapter 5 has d e s c r i b e d t y p i c a l p l a n k t o n d i s t r i b u t i o n s a c r o s s Hecate S t r a i t i n summer and t h e i r correspondence w i t h zones of t i d a l mix ing and s t r a t i f i c a t i o n . However, d i s t r i b u t i o n s i n s p r i n g showed q u i t e a d i f f e r e n t p a t t e r n ( A p r i l 13-14 1980; F i g . 26) . C o n c e n t r a t i o n s of c h l o r o p h y l l a and diatoms were h i g h e s t , and n u t r i e n t s lowest (as r e p r e s e n t e d by N0 3 +N0 2 ) , on the western w e l l - m i x e d s i d e of Hecate S t r a i t . A l though low i n c h l o r o p h y l l , S t a t i o n 21 ad jacent to Graham I s l a n d had the h i g h e s t phaeopigment (2.66 Mg L " 1 ) and d ia tom c o n c e n t r a t i o n s of any s t a t i o n on t h i s c r u i s e . Zooplankton were more abundant i n western than c e n t r a l Hecate S t r a i t , w i t h up to 244 zoop lankton m~ 3 at S t a t i o n 22 compared to 80 n r 3 at S t a t i o n 24. Spec i e s c o m p o s i t i o n a l s o v a r i e d , w i t h Neocal anus pacificus, 142 s T (%o) (°c) 33 9 • 9 32 e * ' 31 7 - • T ( ° C ) - • S ( % o ) 1 9 21 22 23 24 25 28 \ 21 22 23 24 25 Station Number 28 FIGURE 26. D i s c r e t e s t a t i o n data for C r u i s e 13 (13-14 A p r i l 1980) a c r o s s Hecate S t r a i t . S t a t i o n l o c a t i o n s as i n F i g . 25. Top : 3 m c h l . a, N0 3 +N0 2 , d iatom abundance; M i d d l e : 3 m temperature and s a l i n i t y ; Bottom: maximum depth at each s t a t i o n 1 43 Pseudocal anus mi nut us, e u p h a u s i i d l a r v a e and brachyuran zoea a l l abundant n u m e r i c a l l y at S t a t i o n 22, w h i l e Met ri dia pacifica was abundant at S t a t i o n 24. I t i s apparent s p r i n g bloom c o n d i t i o n s p r e v a i l e d i n western Hecate S t r a i t at t h i s t i m e . D u r i n g winter (February 3-4 1980, F i g . 27) , b i o l o g i c a l c h a r a c t e r i s t i c s a l s o d i f f e r e d between east and west Hecate S t r a i t . Diatom c o n c e n t r a t i o n s were low ac ro s s the s t r a i t , whi l e c h l o r o p h y l l was s i g n i f i c a n t l y (p<0.05) g r e a t e r i n western (mean 0.23 uq L " 1 ) than e a s t e r n (mean 0.12 uq L~ 1 ) r e g i o n s . Zooplankton were a l s o low wi th <6 n r 3 at S t a t i o n 27 i n m i d - s t r a i t . These c h l o r o p h y l l d i f f e r e n c e s are r a t h e r s u r p r i s i n g c o n s i d e r i n g average wind speeds i n win te r are 7-10 m s~ 1 , which would be expected to ensure rea sonab ly w e l l - m i x e d c o n d i t i o n s . 2. PHYTOPLANKTON TAXONOMIC COMPOSITION P h y t o p l a n k t o n taxonomic c o m p o s i t i o n was a l s o d i f f e r e n t between the e a s t e r n and western s i d e s of the s t r a i t d u r i n g these three seasons . In win te r ( F i g . 28A) , the t o t a l biomass index of p h y t o p l a n k t o n i n the western r e g i o n (norma l i zed per s t a t i o n ) was twice tha t i n the e a s t , wi th a s i g n i f i c a n t c o n t r i b u t i o n by d ia toms , e s p e c i a l l y Thai assi osira. In the e a s t e r n s t r a i t , the r e l a t i v e biomass of t h i s genus was c o n s i d e r a b l y l e s s . In s p r i n g ( F i g . 28B), p h y t o p l a n k t o n c o m p o s i t i o n a c r o s s the s t r a i t showed the same t r e n d as d u r i n g w i n t e r , a l t h o u g h w i t h much g r e a t e r d ia tom biomass which agrees wi th the bloom c o n d i t i o n s suggested by F i g . 26. The n o r m a l i z e d p h y t o p l a n k t o n 1 44 S 4 1 3 '-j 5 2 •I u (%So) (°C) 33 9 32 8 31 7 30 6 1 ' \ A / \ / \ / \ N O , + NO 2 Log^Q Diatoms Chl. a 22 23 24 25 26 21 20 27 19 18 17 16 15 .Sffco) """»Tf)C) 24 22 20 ~ _i 18 | 16 J z 14 + O z 12 10 8 22 23 24 25 26 21 20 27 19 16 17 16 15 0 25 50 1 75 100 125 150 / 'V, \ \ / \ / \/ \ 22 23 24 25 26 21 20 27 19 18 17 16 Station Number 15 FIGURE 27. D i s c r e t e s t a t i o n data fo r C r u i s e 12 (3-5 February 1980) a c r o s s Hecate S t r a i t . S t a t i o n l o c a t i o n s as i n F i g . 25. Top : 3 m c h l . a, N0 3 +N0 2 , d ia tom abundance; M i d d l e : 3 m temperature and s a l i n i t y ; Bottom: maximum depth at each s t a t i o n . 1 45 A CRUISE 12 50 40 30 20 10 0 < UJ 50 <r < X 40 u < 30 z V) 20 UI -1 a 10 s < w _ i 0 < o UI 70 1-X G 60 UI * 50 40 30 20 10 O West NBI = 1.0 — • u • C S T OD SF LF OF B CRUISE 13 West NBI = 24.1 DaU C S T OD SF LF OF C CRUISE 10 West NBI = 4.9 -Winter 50 40 30 20 10 0 -Spring 50 40 30 20 10 0 - Summer 70 60 50 40 30 20 10 O East NBI= 0.6 T OD SF LF OF East NBI= 0.7 East T OD SF LF OF NBI = 15.3 C S T OD SF LF OF T OD SF LF OF FIGURE 28. Phytop lankton taxonomic c o m p o s i t i o n hi s tograms for east and west Hecate S t r a i t d u r i n g winter 1980 ( A ) , s p r i n g 1980 (B) and summer 1979 ( C ) . See text for d i s c u s s i o n of weighted biomass index c a l c u l a t e d from abundance and r e l a t i v e s i z e . NBI: N o r m a l i z e d (per s t a t i o n i n each area) Biomass Index ( x l O 5 ) ; C : Chaeloceros s p p . ; S: Skelelonema costatum; T : Thai as s i os i r a s p p . ; OD: o ther d ia toms ; SF : sma l l f l a g e l l a t e s (<5 um); L F : l a r g e f l a g e l l a t e s (6-15 um); OF: o ther f l a g e l l a t e s ( i n c l u d i n g d i n o f l a g e l l a t e s ) . 1 46 biomass index in the west was over 35 t imes that i n the e a s t e r n s t r a i t . There had been a t w e n t y - f o l d i n c r e a s e of t o t a l biomass in western Hecate S t r a i t between winter and s p r i n g which c o i n c i d e d w i t h a s h i f t from Thai assi osi ra to Chaetoceros. H o l l i b a u g h et al. (1981) have noted s p e c i e s of Chaet oceros can form r e s t i n g spores under adverse c o n d i t i o n s of l i g h t , n u t r i e n t s or g r a z i n g , and that s u c c e s s f u l g e r m i n a t i o n of these spores i s i n i t i a t e d by l i g h t i n t e n s i t i e s > 10 0 M E irr 2 s " 1 ( = 2 X 1 0 - 3 J c m " 2 s" 1 u s ing the c o n v e r s i o n s i n S t r i c k l a n d (1958b) and X=550 nm) at a temperature range of 7 ° C to 2 1 ° C . Such l i g h t and temperature ranges occur i n western Hecate S t r a i t at the s t a r t of the s p r i n g bloom (see F i g . 34) . E a s t e r n Hecate S t r a i t remained dominated by f l a g e l l a t e s and at the same biomass index as that d u r i n g w i n t e r . D u r i n g summer the taxonomic c o m p o s i t i o n p a t t e r n was o p p o s i t e to that d u r i n g winter and s p r i n g . Western Hecate S t r a i t had become the f l a g e l l a t e - d o m i n a t e d r e g i o n w h i l e the s t r a t i f i e d e a s t e r n s i d e was dominated by d i a toms , s p e c i f i c a l l y Skeletonema costatum ( F i g . 28C) . A c c o r d i n g to T u r p i n and H a r r i s o n (1979) the observed spring-summer s w i t c h from Chaet ocer os to Skeletonema i s p r e d i c t a b l e i f n u t r i e n t ( s p e c i f i c a l l y NH„) p a t c h i n e s s i n c r e a s e s , as might occur on the e a s t e r n s i d e w i t h s p o r a d i c storm m i x i n g of deeper water to the s u r f a c e . Between June and J u l y 1979 ( C r u i s e s 10 and 11), the n o r m a l i z e d biomass index for both western and e a s t e r n r e g i o n s approx imate ly d o u b l e d , a p p a r e n t l y due to an i n c r e a s e of s m a l l f l a g e l l a t e s . A b s o l u t e d ia tom biomass i n the western r e g i o n decreased between these two c r u i s e s , w h i l e l i t t l e 147 change o c c u r r e d in the e a s t . 3. SEASONAL COMPOSITION PATTERNS Phytop lankton c o m p o s i t i o n p a t t e r n s between seasons and between r e g i o n s can be examined by c l u s t e r i n g s t a t i o n s u s ing t h e i r taxonomic chord d i s t a n c e s . The r e s u l t i n g c l u s t e r phenogram i s p r e s e n t e d i n F i g . 29. S e v e r a l d i s t i n c t c l u s t e r s form at chord d i s t a n c e s l e s s than 0 .90 . C l u s t e r I groups s t a t i o n s i n western Hecate S t r a i t d u r i n g w i n t e r , but i n c l u d e s the two s p r i n g s t a t i o n s i n e a s t e r n Hecate S t r a i t . T h i s suggests p h y t o p l a n k t o n taxonomic c o m p o s i t i o n d u r i n g s p r i n g i n the e a s t e r n s t r a i t and win te r i n the western s t r a i t were s i m i l a r , p o s s i b l y r e s u l t i n g from comparable mix ing and l i g h t c h a r a c t e r i s t i c s . C l u s t e r II i s composed of s t a t i o n s l o c a t e d i n the e a s t e r n r e g i o n d u r i n g w i n t e r , ma in ly f l a g e l l a t e - d o m i n a t e d wi th l i t t l e c o n t r i b u t i o n of d iatoms to t o t a l b iomass , w h i l e C l u s t e r III i s d i s t i n c t l y the s p r i n g bloom s t a t i o n s of western Hecate S t r a i t . C l u s t e r IV groups s t a t i o n s sampled d u r i n g summer, but d i s t i n g u i s h e s two s u b - c l u s t e r s at chord d i s t a n c e s l e s s than 0 . 6 5 . S u b - c l u s t e r IVa i s formed by three s t a t i o n s i n the boundary or f r o n t a l r e g i o n of Hecate S t r a i t between the s t r a t i f i e d e a s t e r n and mixed western r e g i o n s , as o u t l i n e d i n Chapter 5. C l u s t e r IVb i s formed by s t a t i o n s from Chatham Sound and e a s t e r n Dixon E n t r a n c e . Note the two summer c r u i s e s i n June and J u l y 1979 are not s epara ted on the b a s i s of t h e i r taxonomic c o m p o s i t i o n . S t a t i o n s i n western Hecate S t r a i t do not form a 1 48 1.1 1.0 - J 0.9 _ J CHORD 0.8 DISTANCE 0.7 STN GROUP 0.6 _ L _ 0.5 I 0.4 _ J 1220 1222 1223 1325 1328 1224 1217 1215 1221 1225 1226 1219 1218 1216 1229 1321 1322 1323 1324 1016 1117 1017 1018 1115 1114 1019 1014 1113 1013 1015 1116 IV FIGURE 29. C l u s t e r phenogram of s t a t i o n s sampled i n Hecate S t r a i t d u r i n g summer 1979, winter and s p r i n g 1980 u s ing chord d i s t a n c e s c a l c u l a t e d from phytop lankton taxonomic c o m p o s i t i o n . S t a t i o n s are i d e n t i f i e d by c r u i s e number ( f i r s t two d i g i t s ) then s t a t i o n number. Groups have been a s s i gned from a chord d i s t a n c e of 0 .90 . 1 49 d i s t i n c t c l u s t e r , i n s t e a d j o i n i n g s u b - c l u s t e r s IVa and IVb i n d i v i d u a l l y . 4. SPATIAL SCALE ESTIMATES P h y s i c a l and b i o l o g i c a l parameters a c r o s s Hecate S t r a i t w i l l vary on s c a l e s c o n s i s t e n t w i t h t h e i r u n d e r l y i n g o r g a n i z i n g mechanisms. Any s i m i l a r i t y of s c a l e s between seasons suggests such mechanisms may be r e g u l a r f e a t u r e s of the r e g i o n w i t h p r e d i c t a b l e e f f e c t s . Sea su r f ace i n f r a r e d (AVHRR) data measured a c r o s s Hecate S t r a i t d u r i n g l a t e summer (12 September 1980) by the TIROS-N s a t e l l i t e ( F i g . 30A) show a marked temperature f r o n t 30-40 km from the Queen C h a r l o t t e I s l a n d s , i n d i c a t i n g c o o l e r water i n m i d - s t r a i t . Another f r o n t i s l o c a t e d about 80 km from the western s h o r e . Note that IR b r i g h t n e s s va lue s are i n v e r s e l y r e l a t e d to temperature such tha t warmer water r e g i s t e r s as d a r k e r shades . P i x e l s were averaged m e r i d i o n a l l y a c ro s s an 80x10 km box (see F i g . 25) to produce t h i s z o n a l s e r i e s of b r i g h t n e s s v a l u e s . Near su r f ace temperature and f l u o r e s c e n c e data c o l l e c t e d on a t r a n s e c t a c ro s s Hecate S t r a i t two weeks p r i o r to the image of F i g . 30 are p re sented i n Chapter 5 ( F i g . 24 ) . I t c l e a r l y shows t h i s decrease of temperature and an i n c r e a s e of f l u o r e s c e n c e 30-40 km from the Queen C h a r l o t t e I s l a n d s , c o i n c i d e n t w i t h the t r a n s i t i o n from mixed to s t r a t i f i e d water masses. However, f l u o r e s c e n c e c o n t i n u e d to i n c r e a s e w i t h d i s t a n c e , peak ing i n m i d - s t r a i t 60 km from the western s h o r e . 1 50 136 104 R a n g e ( k m ) CD 140 120 100 80 6 0 -4 0 -20 B —i— 13 — i — 26 39 52 65 78 91 104 S p a t i a l S c a l e ( k m ) FIGURE 30. TIROS-N ( o r b i t number 9882) AVHRR sea s u r f a c e i n f r a r e d b r i g h t n e s s v a l u e s a c ro s s Hecate S t r a i t on 12 Sept . 1980. A . Zonal s e c t i o n of averaged v a l u e s from the boxed area i n F i g . 25. L i n e i s the l i n e a r l e a s t square f i t to d e t r e n d the d a t a . B. S t r u c t u r e f u n c t i o n e s t imate s from the det rended data i n A . 151 D u r i n g s p r i n g , F i g . 26 i n d i c a t e s warmer water o c c u r r e d i n the western s t r a i t , wi th a decrease of temperature between 40 and 70 km c o i n c i d e n t wi th the decrease of p h y t o p l a n k t o n biomass . I n f r a r e d b r i g h t n e s s data c o l l e c t e d by the NOAA-7 s a t e l l i t e d u r i n g s p r i n g (25 March) 1983 i n d i c a t e a p a t t e r n very s i m i l a r to that of F i g . 30A. R e l a t i v e l y warm water o c c u r r e d i n western Hecate S t r a i t , w i t h an abrupt t r a n s i t i o n to c o o l e r water a p p r o x i m a t e l y 50 km from the western edge of the s t r a i t , f o l l o w e d by another f r o n t at 70 km. A l t h o u g h r e c o r d e d three year s l a t e r , the p a t t e r n resembles the t r a n s e c t da ta of F i g . 26. These s c a l e s for temperature and f l u o r e s c e n c e are a l s o i n d i c a t e d by s t r u c t u r e f u n c t i o n s c a l c u l a t e d from the o r i g i n a l d a t a . The s t r u c t u r e f u n c t i o n d e r i v e d from a s ine (or c o s i n e ) wave w i l l have a t rough at X and a peak at X / 2 . D e t r e n d i n g the s a t e l l i t e da ta produces an approximate s i n e wave, s u g g e s t i n g for the TIROS b r i g h t n e s s data ( F i g . 30B) the t rough at 60 km r e p r e s e n t s X, w i t h peak v a r i a b i l i t y at 30 and 70 km d u r i n g summer. C a l c u l a t i o n s of s t r u c t u r e f u n c t i o n s for the c o n t i n u o u s t r a n s e c t temperature data of F i g . 24 and s p r i n g 1983 NOAA-7 b r i g h t n e s s data show wavelengths and peak v a r i a b i l i t y at s c a l e s s i m i l a r to F i g . 30B. The c o n t i n u o u s t r a n s e c t f l u o r e s c e n c e data of F i g . 24 shows d i f f e r e n t s c a l e s of v a r i a b i l i t y however ( F i g . 31) . The wavelength of the de t rended s e r i e s i s e s t i m a t e d to be 100 km, which approximates the d i s t a n c e ac ro s s n o r t h e r n Hecate S t r a i t , w i t h peak v a r i a b i l i t y at a s c a l e of 60 km. 1 52 FIGURE 31. S t r u c t u r e f u n c t i o n e s t imate s of c o n t i n u o u s 3 m f l u o r e s c e n c e ac ro s s Hecate S t r a i t measured on 30 August 1980. O r i g i n a l data shown in F i g . 24. 1 53 Cont inuous data are not a v a i l a b l e for the winter and s p r i n g c r u i s e s , so s t r u c t u r e f u n c t i o n s were e s t imated by grouping s t a t i o n p a i r s i n t o c a t e g o r i e s based on t h e i r s e p a r a t i o n d i s t a n c e s . R e s u l t s are p r e s e n t e d in Table X, where a l a r g e change suggests s p a t i a l v a r i a b i l i t y at that s c a l e . E s t i m a t e s for summer ( C r u i s e 11) g e n e r a l l y agree w i t h the broad s p a t i a l s c a l e s of temperature and c h l o r o p h y l l suggested by the s a t e l l i t e and t r a n s e c t da ta c o l l e c t e d one year l a t e r . E s p e c i a l l y noteworthy i s the apparent s t r u c t u r e of d ia tom biomass at s c a l e s >60 km which does not appear in f l a g e l l a t e b iomass . D i f f e r e n c e s of s p a t i a l o r g a n i z a t i o n between these groups have a l s o been noted by Farmer et al. (1982) for the w i n t e r - s p r i n g phytop l ankton bloom i n Narraganse t t Bay. In s p r i n g ( C r u i s e 13), n e i t h e r c h l o r o p h y l l nor the d ia tom biomass index show any apparent s t r u c t u r e at l a r g e s c a l e s a f t e r the removal of the s t r o n g c r o s s - s t r a i t t r e n d s . T h i s suggests the edge of the s p r i n g bloom i s r a t h e r d i f f u s e , compared w i t h the marked t i d a l f r o n t that occur s d u r i n g summer. 5. RELATION TO BATHYMETRY The ba thymet r i c p r o f i l e for the t r a n s e c t from Lawn P o i n t (Graham I s l a n d ) to Browning E n t r a n c e ( F i g . 24) i s shown in F i g . 32. The sha l low (western) and deep (eas tern) r e g i o n s are c l e a r l y i n d i c a t e d , w i t h the edge of the s h e l f o c c u r r i n g i n m i d - s t r a i t at about 50 km. The p r e c i s e d imens ion of the s h e l f v a r i e s w i t h l o c a t i o n , but 50-60 km from the Queen C h a r l o t t e I s l a n d s i s t y p i c a l . 154 TABLE X . E s t i m a t e d s t r u c t u r e f u n c t i o n s for parameters measured at d i s c r e t e s t a t i o n s and grouped i n t o d i s t a n c e c a t e g o r i e s . C r u i s e 11, J u l y 1979; C r u i s e 13, A p r i l 1980. D i s t a n c e c a t e g o r i e s are i n km. Number of P a i r s Temperature C h l o r o p h y l l L o g 1 0 F l a g e l l a t e Biomass Index Log!o Diatom Biomass Index CRUISE 1 1 20-40 40-60 >60 3 3 4 0.94 0. 16 0. 23 0.70 0. 83 0. 66 0.13 0. 1 1 0. 1 4 0.16 0. 31 0. 63 1 3 20-40 40-60 >60 5 4 5 0.10 0.25 0.10 6.72 9.51 12.03 0 .03f 0 .02* 0.01 0.60 0.51 0.66 f Number of s t a t i o n p a i r s = 3 t Number of s t a t i o n p a i r s = 1 1 55 HECATE STRAIT: BATHYHETRY FIGURE 32. Ba thymetr i c p r o f i l e a c r o s s Hecate S t r a i t from Lawn P o i n t (Queen C h a r l o t t e I s l a n d s ) to Browning E n t r a n c e , 30 August 1980. T h i s i s the same t r a n s e c t on which F i g . 24 data were r e c o r d e d . 1 56 No d i s t i n c t ba thymetr i c f e a t u r e appears to be r e l a t e d to the temperature f ront at a range of 30-40 km d u r i n g summer, a l t h o u g h the 40-50 km range d u r i n g s p r i n g i s l i k e l y r e l a t e d to the edge of the western s h e l f . Data from the d i s c r e t e t r a n s e c t s suggest major v a r i a t i o n s of b i o l o g i c a l and p h y s i c a l p r o p e r t i e s occur at ranges between 40-70 km in s p r i n g ( F i g . 26, between S t a t i o n s 23 and 24) and about 60 km in winter ( F i g . 27, S t a t i o n s 20 and 27) . The range of 60 km at which the c o n t i n u o u s f l u o r e s c e n c e p r o f i l e peaks can be r e l a t e d to the edge of the western s h e l f . The second f r o n t at 80 km occur s c l o s e to the e a s t e r n shore and i s p r o b a b l y a r e s u l t of l o c a l runof f and to a c e r t a i n ex tent the rebound of i s o p y c n a l s depres sed d u r i n g winter onshore t r a n s p o r t , as suggested by Barber (1957) . Such s c a l e s , apparent i n the o r i g i n a l data and conf i rmed by the s t r u c t u r e f u n c t i o n e s t i m a t e s , suggest temperature v a r i a t i o n s may be r e l a t e d to the c r o s s - s h e l f d i m e n s i o n , w h i l e p h y t o p l a n k t o n biomass (as measured by f l u o r e s c e n c e ) may be r e l a t e d to the c r o s s - s t r a i t d i m e n s i o n . The temperature f r o n t occur s at the edge of the s h e l f , but w i l l f l u c t u a t e h o r i z o n t a l l y w i t h the i n t e n s i t y of s t r a t i f i c a t i o n on the e a s t e r n s i d e and the s t r e n g t h of the t i d a l c u r r e n t s over the s h e l f . D u r i n g s p r i n g , the f r o n t w i l l be formed by more in tense h e a t i n g of the sha l low water as d i s c u s s e d i n Chapter 5. The f l u o r e s c e n c e maximum i s a l s o r e l a t e d to the s h e l f d i m e n s i o n : d u r i n g s p r i n g the h i g h e r biomass occur s over the whole of the western s i d e , w h i l e i n summer i t occur s i n m i d - s t r a i t where the bathymetry deepens i n t o the e a s t e r n t r o u g h . 1 57 I t i s here that summer s t r a t i f i c a t i o n i s l i k e l y to be more c o n s t a n t , be ing eastward of the f l u c t u a t i o n s of the thermal f r o n t over the s h e l f . S t u d i e s of p l a n k t o n d i s t r i b u t i o n s about c o n t i n e n t a l s h e l f break r e g i o n s i n summer (Denman et al . 1980, P ingree and M a r d e l l 1981) a l s o f i n d tha t p h y t o p l a n k t o n biomass i s o f t en a s s o c i a t e d wi th the edge of the s l o p e r a t h e r than the s h e l f or deep b a s i n . 6. SPRING BLOOM INITIATION The importance of bathymetry to r e g i o n s of t i d a l mix ing i s c l e a r w i t h i t s i n c l u s i o n i n the h U " 3 model of Simpson and Hunter (1974) . Bathymetry a l s o p l a y s a c r u c i a l r o l e i n the i n i t i a t i o n of the s p r i n g bloom of p h y t o p l a n k t o n by l i m i t i n g the depth of mix ing and subsequent ly i n c r e a s i n g the mean l i g h t i n t e n s i t y to which c e l l s w i l l be .exposed. T h i s can be demonstrated for Hecate S t r a i t by c a l c u l a t i n g sur f ace mixed depths s e p a r a t e l y for the sha l low western and deep ea s t e rn reg ions ( F i g . 33) . The c r i t i c a l depth remains deeper than the bottom (the e f f e c t i v e l i m i t of the mixed l a y e r ) from March to August or September in the western s t r a i t , w h i l e i n the east the bottom i s too deep to d i r e c t l y i n f l u e n c e the s u r f a c e mixed d e p t h . The "growing season" for the e a s t e r n r e g i o n i s t h e r e f o r e p r e d i c t e d to be May to August or September. T h i s p r e d i c t i o n i s s u b s t a n t i a t e d by the data of F i g . 26, which f u r t h e r i n d i c a t e s that the s p r i n g p h y t o p l a n k t o n bloom s h o u l d occur about March or A p r i l i n western Hecate S t r a i t as a r e s u l t of i t s sha l low d e p t h . 1 58 o 20 40 WESTERN HECATE STRAIT g. 60 v D 80 KX) M M EASTERN HECATE STRAIT 20 40 60 T~ 80 a KX) a 120 140 1 1 M A M J J ^ Z c r + 955fc Confidence Interval T I 2-mix + 95% Confidence Interval i Mean monthly bottom depth of stations FIGURE 33. Hecate S t r a i t c r i t i c a l depth - mixed depth model r e s u l t s c a l c u l a t e d as d e s c r i b e d in t e x t . H o r i z o n t a l dashed l i n e r e p r e s e n t s mean bottom depth of the set of s t a t i o n s sampled that month. Data are a composi te from 1954 to 1971. 1 59 These monthly-compos i te mixed l a y e r depths (MLD) can a l s o be used i n the equa t ion T H L D = ^ ° , (Parsons et al. 1984) to e s t imate the mean l i g h t i n t e n s i t y a v a i l a b l e throughout the sur f ace mixed l a y e r . F i g . 34 i n d i c a t e s these v a l u e s for east and west Hecate S t r a i t and compares them w i t h the mean l i g h t i n t e n s i t y proposed by G i e s k e s and Kraay (1975) for a net i n c r e a s e of s p r i n g phytop l ankton p r o d u c t i o n i n Dutch c o a s t a l water s . T h i s f i g u r e suggests the same t i m i n g of the s p r i n g bloom as proposed by the c r i t i c a l depth model , w i t h the bloom i n the western r e g i o n o c c u r r i n g e a r l y i n the s p r i n g . However, d u r i n g summer the d i f f e r e n c e of mean l i g h t i n t e n s i t i e s expected by the t i d a l mix ing h y p o t h e s i s , which suggests that p h y t o p l a n k t o n on the mixed s i d e are l i g h t - l i m i t e d , does not o c c u r . The sha l low depth of the mixed r e g i o n , p l u s weak s t r a t i f i c a t i o n at i t s e a s t e rn edge, produce l i g h t c o n d i t i o n s s u f f i c i e n t to support net p h y t o p l a n k t o n growth. T h i s c o n c l u s i o n was a l s o noted i n Chapter 5, where i t was suggested n u t r i e n t s r a t h e r than l i g h t were the l i m i t i n g r e s o u r c e . D. DISCUSSION A sea sona l p r o g r e s s i o n of phytop l ankton p r o d u c t i o n and the importance of t i d a l mix ing can now be proposed for Hecate 1 60 FIGURE 34. Monthly mean mixed l a y e r l i g h t i n t e n s i t i e s f o r west ( s o l i d l i n e ) and east (short dashed l i n e ) Hecate S t r a i t . V e r t i c a l bars represent 95% confidence i n t e r v a l s of the mean. Long dashed l i n e r epresents the l i g h t i n t e n s i t y suggested by Gieskes and Kraay (1975) as the c r i t i c a l i n t e n s i t y f o r phytoplankton blooms. 161 S t r a i t . D u r i n g w i n t e r , the l a r g e r p r o p o r t i o n of diatoms on the western s i d e of the s t r a i t r e s u l t s from adequate n u t r i e n t c o n c e n t r a t i o n s and h i g h e r mean l i g h t i n t e n s i t i e s due to the sha l low depth of m i x i n g . Examples of such i n c r e a s e s d u r i n g winter due to s h o a l i n g of the mixed l a y e r have been shown for c h l o r o p h y l l ( F o u r n i e r et al. 1979) and diatoms (Re id et al. 1983). In Long I s l a n d Sound, S c h n i t z e r (1979, quoted i n Farmer et al. 1982) observed t h a t i n w e l l mixed waters the r a t i o of 1% l i g h t depth to maximum depth can be used to p r e d i c t the dominant p h y t o p l a n k t o n group, i . e . m i c r o f l a g e l l a t e s i f t h i s r a t i o i s <0.5, and diatoms i f >0.5. In the mixed waters of western Hecate S t r a i t t h i s r a t i o i s l i k e l y to be g r e a t e r than 0.5 i n w i n t e r , r e s u l t i n g i n d i a t o m - f a v o u r a b l e c o n d i t i o n s . With i n c r e a s i n g s o l a r r a d i a t i o n i n s p r i n g , the p h y t o p l a n k t o n outbur s t o c c u r s f i r s t on the western s i d e . T i d a l mix ing does not p l a y a r o l e i n i n i t i a t i n g t h i s bloom, as the whole s t r a i t w i l l tend to be w e l l - m i x e d by average winds of 8-10 m s" 1 (Environment Canada 1975). Moreover , there w i l l be i n s u f f i c i e n t s o l a r r a d i a t i o n for s t r a t i f i c a t i o n (Tabata 1958). The d i f f e r e n c e i n t i m i n g between e a s t e r n and western s i d e s i s a r e s u l t of the d i f f e r e n t bathymetry and i t s e f f e c t on l i m i t i n g the mixed depth and i n c r e a s i n g mean l i g h t i n t e n s i t i e s above c r i t i c a l l e v e l s . The presence on the western s i d e of g r e a t e r d ia tom biomass over win te r may a l s o ac t as a source of seed s t o c k . 1 62 Such a p r e d i c t a b l e mechanism i n f l u e n c i n g the development of the s p r i n g bloom i n western Hecate S t r a i t may have important consequences for the d i s t r i b u t i o n and s u r v i v a l of l a r v a l f i s h . Mason el al . (1981) sampled a c r o s s Hecate S t r a i t , i n A p r i l 1980 l e s s than one week a f t e r the data of F i g . 26 were c o l l e c t e d , and found g r e a t e r d i v e r s i t y and over ten t imes g r e a t e r abundance of f i s h l a r v a e on the western s i d e than the e a s t e r n s i d e of the s t r a i t . Ketchen (1956) has suggested tha t E n g l i s h s o l e (Parophyrs vetulus) l a r v a e d r i f t northwards to s e t t l e on these sha l low banks about A p r i l . Such a mechanism may i n c r e a s e l a r v a l s u r v i v a l by matching t h e i r a r r i v a l in western Hecate S t r a i t wi th a bloom of p o t e n t i a l food i t ems . In summer, mean mixed l a y e r l i g h t i n t e n s i t i e s a c r o s s the s t r a i t are s i m i l a r a c c o r d i n g to the l i m i t e d data on mixed depths and a t t e n u a t i o n c o e f f i c i e n t s summarized i n F i g . 34. The western r e g i o n appears to be s u f f i c i e n t l y s h a l l o w , w i t h depths comparable to the s u r f a c e mixed l a y e r of the s t r a t i f i e d s i d e , to e l i m i n a t e growth d i f f e r e n c e s due to l i g h t l i m i t a t i o n . . A s suggested i n Chapter 5, the low biomass of the mixed s i d e d u r i n g summer p r o b a b l y r e s u l t s from n u t r i e n t l i m i t a t i o n and l a ck of a deep re se rve p o o l , w h i l e h i g h e r biomass on the e a s t e r n s ide may occur from n u t r i e n t input v i a u p w e l l i n g a l o n g the s h e l f edge i n the c e n t r a l s t r a i t ( e . g . due to the longshore c u r r e n t , Hsueh and O ' B r i e n 1 9 7 1 ) , . o r s p o r a d i c storm mix ing as d i s c u s s e d for the New York B i g h t by Walsh et al. (1978) . Data p r e s e n t e d in F i g . 28C, showing dominance of f l a g e l l a t e biomass on the western s i d e 163 r e l a t i v e to d ia tom biomass i n the e a s t , are c o n s i s t e n t w i t h t h i s i n t e r p r e t a t i o n . Dur ing w i n t e r , s p r i n g and summer, the c r o s s - s t r a i t f e a t u r e that c o n s i s t e n t l y i n f l u e n c e s p h y t o p l a n k t o n s p a t i a l o r g a n i z a t i o n and c o m p o s i t i o n i s ba thymetry . I t i n f l u e n c e s the water column mean l i g h t i n t e n s i t y d u r i n g winter and s p r i n g , and the degree of t i d a l mix ing and p o t e n t i a l for n u t r i e n t r e s u p p l y to s u r f a c e waters d u r i n g summer. T i d a l mix ing v a r i a t i o n s a c ro s s Hecate S t r a i t appear to be important to p l a n k t o n o r g a n i z a t i o n o n l y i n summer, however, i n such sha l low water the i n f l u e n c e of wind mix ing must a l s o be c o n s i d e r e d . I f we p o s t u l a t e c o n d i t i o n s of no t i d a l m i x i n g , then t y p i c a l wind v e l o c i t i e s d u r i n g summer of 4-6 m s" 1 (Thomson 1981) suggest mixed l a y e r depths of about 20 m, s i m i l a r to a c t u a l mixed depths for the e a s t e r n s t r a i t i n summer and maximum depths of much of the western s h e l f . The a c t i o n s of t i d a l mix ing and wind mix ing may e s s e n t i a l l y o v e r l a p i n the western r e g i o n w i t h the mix ing e f f e c t of the t i d e s e q u i v a l e n t to that of winds b lowing about 5 m s " 1 . T h i s i s a l s o shown from t h e o r e t i c a l c o n s i d e r a t i o n s , where the a c t i o n s of t i d a l mix ing and wind mix ing are e q u i v a l e n t i f they have e q u i v a l e n t energy d i s s i p a t i o n r a t e s per u n i t mass ( K u l l e n b e r g 1983) c u3 Pa C s k W?0 P h 'w 164 Bottom and sur face drag c o e f f i c i e n t s are C , and C (2 .5X10~ 3 and a s 2X10" 3 r e s p e c t i v e l y ) , h i s the water d e p t h , p g and p w are a i r and water d e n s i t i e s , U the v e r t i c a l l y - a v e r a g e d t i d a l v e l o c i t y , k the wind f a c t o r (3X10~ 2 ) and W 1 0 the wind v e l o c i t y 10 m above the s u r f a c e . U s i n g c o n v e n t i o n a l va lue s as i n d i c a t e d (from K u l l e n b e r g 1983), i t can be shown that average wind v e l o c i t i e s of 5-7 m s" 1 c o r r e s p o n d to average t i d a l c u r r e n t s of 0 . 2 -0 .3 m s " 1 , s i m i l a r to those d e r i v e d from the t i d a l model of Chapter 5 for waters of western Hecate S t r a i t sha l lower than 20 m. T h e r r i a u l t et al . (1978), s t u d y i n g a sha l low c o a s t a l embayment, conc luded that p h y t o p l a n k t o n s p a t i a l v a r i a b i l i t y was dominated by p h y s i c a l proces se s when wind speeds were >5 m s " 1 . T i d a l mix ing was not c o n s i d e r e d i n t h e i r s tudy . The e f f e c t s of wind and t i d a l a c t i o n i n mix ing a sha l low water column w i l l d i f f e r on both temporal and s p a t i a l s c a l e s , however. In g e n e r a l , mix ing by t i d e s d u r i n g summer w i l l be more important at s h o r t e r s c a l e s . I t s i n t e n s i t y w i l l vary wi th the s e m i - d i u r n a l or d i u r n a l c y c l e , and w i l l vary a l s o w i t h the f o r t n i g h t l y n e a p - s p r i n g c y c l e . In c o n t r a s t , the i n t e n s i t y of wind mix ing w i l l decrease from winter to summer wi th the decrease i n frequency of e x t r a - t r o p i c a l c y c l o n e s i n the n o r t h e a s t P a c i f i c . F i s s e l (1975), i n a study of wind data from Ocean S t a t i o n 'Papa ' ( 5 0 ° N , 1 4 5 ° W ) , found p e r i o d s between maximal winds d u r i n g winter of 2.5 days , and 4.5 days d u r i n g summer. S p e c t r a l a n a l y s i s of ocean ic wind data measured d u r i n g summer 1979 and 1980 o f f the west coas t of Vancouver I s l a n d 165 suggest s i m i l a r p e r i o d s (Thomson 1983). S p a t i a l s c a l e s of wind and t i d e a c t i o n a l s o d i f f e r , w i t h s i g n i f i c a n t t i d a l mix ing c o n f i n e d to the sha l low western r e g i o n and v a r y i n g w i t h the bathymetry , w h i l e wind mix ing w i l l vary w i t h topography, showing much l e s s sma l l s c a l e v a r i a t i o n over the open s t r a i t . There i s , however, an i n c r e a s i n g g r a d i e n t of wind speed from west to ea s t , w i t h winds at B o n i l l a I s l a n d i n the e a s t e r n s t r a i t about twice as s t r o n g as those at Sandsp i t (Environment Canada 1975). L i t t l e i s known about b e n t h i c communit ies i n Hecate S t r a i t . E s p e c i a l l y in western Hecate S t r a i t , w i t h the sha l low depth and probab le s e d i m e n t a t i o n of the s p r i n g bloom, the b e n t h i c community may be q u i t e e x t e n s i v e , a l t h o u g h i t i s l i k e l y to vary w i t h bottom t i d a l s t r e s s (see e . g . Warwick and U n c l e s 1980). Pomroy et al. (1983) e s t imated that n u t r i e n t e f f l u x from sand sediments i n a bay ad jacent to the B r i s t o l Channel shou ld s a t i s f y the n i t r o g e n demand of the p h y t o p l a n k t o n when p r o d u c t i v i t y i s low, but meet o n l y 16% of the demand d u r i n g peak p r o d u c t i v i t y i n June . If n u t r i e n t s are r e l e a s e d from the sediments i n western Hecate S t r a i t , then t i d a l mix ing w i l l have a g r e a t e r impact on t h e i r v e r t i c a l and h o r i z o n t a l d i s t r i b u t i o n s than wind m i x i n g . The maximum a c t i o n of t i d a l mix ing i s at the bottom, w h i l e for wind mix ing the maximum s t r e s s o c c u r s at the s u r f a c e . However, i f n u t r i e n t r e l e a s e from the sediment was s low, i t may not meet the p h y t o p l a n k t o n demand on the western s ide compared w i t h the f requency of storm mix ing and i n j e c t i o n of n u t r i e n t s i n the e a s t . 1 66 E . SUMMARY P h y t o p l a n k t o n s p a t i a l o r g a n i z a t i o n and taxonomic c o m p o s i t i o n a c r o s s Hecate S t r a i t , B . C . were examined s e a s o n a l l y . The p a t t e r n was s i m i l a r i n winter and s p r i n g w i t h the h i g h e s t biomass and a g r e a t e r c o n t r i b u t i o n by diatoms on the sha l low western s h e l f . The s p r i n g bloom o c c u r r e d by A p r i l in the west, but l a t e r on the e a s t e r n s i d e . Bathymetry i s the key d i f f e r e n c e , l i m i t i n g the mixed depth of the western s ide and i n c r e a s i n g mean l i g h t i n t e n s i t i e s . A c r i t i c a l depth model which i n c l u d e s these b a t h y m e t r i c v a r i a t i o n s c o r r e c t l y p r e d i c t s t h i s p a t t e r n . The biomass and c o m p o s i t i o n p a t t e r n d u r i n g summer was o p p o s i t e to tha t i n win te r and s p r i n g . Chapter 5 has suggested p l a n k t o n d i s t r i b u t i o n s i n summer are d r i v e n by t i d a l mix ing and n u t r i e n t , not l i g h t , l i m i t a t i o n . Taxonomic c o m p o s i t i o n p a t t e r n s agree wi th t h i s i n t e r p r e t a t i o n , a l t h o u g h wind mix ing of sha l low (<30 m) water columns must a l s o be c o n s i d e r e d . The p r e d i c t a b i l i t y and s m a l l s c a l e s of t i d a l mix ing suggest that i t may be more important in d i s t r i b u t i n g n u t r i e n t s v e r t i c a l l y , e s p e c i a l l y i f b e n t h i c r e g e n e r a t i o n o c c u r s . S c a l e s of v a r i a t i o n of temperature and f l u o r e s c e n c e appear to be r e l a t e d to d imens ions of the sha l low s h e l f . I conc lude bathymetry i s the major f ea ture ac ro s s Hecate S t r a i t i n f l u e n c i n g p l a n k t o n o r g a n i z a t i o n and c o m p o s i t i o n s e a s o n a l l y by r e d u c i n g the mixed l a y e r i n w i n t e r , and m a i n t a i n i n g the mixed l a y e r and p r e v e n t i n g n u t r i e n t accumula t ions i n summer. A l t h o u g h present in 1 67 a l l seasons , t i d a l mix ing does not appear to determine p l a n k t o n blooms in win te r or s p r i n g . V I I . GENERAL CONCLUSIONS AND SUMMARY 1. CONCLUSIONS The B r i t i s h Columbia n o r t h e r n s h e l f i n c l u d e s Queen C h a r l o t t e S t r a i t and Sound, Hecate S t r a i t , Dixon E n t r a n c e , and t h e i r c o n t i g u o u s waters . I t i s the l a r g e s t r e g i o n of the B . C . c o a s t , wi th oceanographic p r o p e r t i e s that r e f l e c t both c o a s t a l and ocean ic c h a r a c t e r i s t i c s . I t i s a l s o a r e g i o n that has been p o o r l y s t u d i e d o c e a n o g r a p h i c a l l y , yet has p o t e n t i a l l y v a l u a b l e l i v i n g and n o n - l i v i n g r e s o u r c e s . One such r e s o u r c e , p e t r o l e u m , i s expected to occur i n c o m m e r c i a l l y e x p l o i t a b l e q u a n t i t i e s . Ten years ago a moratorium was imposed on petro leum e x p l o r a t i o n a c t i v i t i e s i n t h i s r e g i o n , p r i n c i p a l l y to a l l ow time for c o l l e c t i o n of e n v i r o n m e n t a l data and assessment of i t s s e n s i t i v i t y to such a c t i v i t i e s . However, d u r i n g t h i s t ime very few oceanographic data were a c t u a l l y c o l l e c t e d . The s h i p of o p p o r t u n i t y p r o j e c t on which t h i s t h e s i s i s based was t h e r e f o r e i n i t i a t e d to p r o v i d e such i n f o r m a t i o n , which has s i n c e proven u s e f u l i n the I n i t i a l E n v i r o n m e n t a l E v a l u a t i o n s fo r the reg ion ( e . g . Petro-Canada 1983). The scope of t h i s t h e s i s was expanded, however, to become the f i r s t r o u t i n e i n v e s t i g a t i o n of the b i o l o g i c a l oceanography of the B . C . n o r t h e r n s h e l f . In a d d i t i o n to p r o v i d i n g b a s e l i n e i n f o r m a t i o n on p l ankton and a reas p o t e n t i a l l y s e n s i t i v e to pet ro leum e x p l o r a t i o n , i t s f i n d i n g s w i l l a l s o be of use i n m u l t i - s p e c i e s f i s h e r i e s management models , and i n examining 168 169 b a s i c b i o l o g i c a l responses to p h y s i c a l oceanographic p r o c e s s e s . The g e n e r a l p h y s i c a l oceanography of the n o r t h e r n s h e l f was not examined d i r e c t l y i n t h i s s tudy . I n s t e a d , r e s u l t s from p r e v i o u s s t u d i e s were used (reviewed in Chapter 2 ) , a l t h o u g h they are by no means comple te . The most s e r i o u s l a c k i s of d e t a i l e d knowledge of the c i r c u l a t i o n p a t t e r n s . For example, a weak gyre over the sha l low banks of western Hecate S t r a i t was i m p l i e d by the model s t u d i e s of B e l l (1963), a l t h o u g h i t has not been s u b s t a n t i a t e d yet by d i r e c t measurements. The subsur face c u r r e n t p a t t e r n s are a l s o almost c o m p l e t e l y unknown. C u r r e n t meters have been i n s t a l l e d at v a r i o u s l o c a t i o n s on the n o r t h e r n s h e l f to r e s o l v e these q u e s t i o n s , and r e s u l t s s h o u l d be a v a i l a b l e i n the near fu ture (Dr . B i l l C r a w f o r d , I n s t i t u t e of Ocean S c i e n c e s , S i d n e y , B . C . , p e r s o n a l communica t ion ) . Such d e t a i l e d i n f o r m a t i o n w i l l be very u s e f u l i n p r e d i c t i n g proces se s l i k e c u r r e n t - d r i v e n u p w e l l i n g and d i s p e r s a l of p l a n k t o n p a t c h e s . The t h e o r e t i c a l p a t t e r n of i n i t i a t i o n of the s p r i n g p h y t o p l a n k t o n bloom for the B . C . coas t was c a l c u l a t e d i n t h i s t h e s i s u s i n g a c r i t i c a l depth - mixed depth model (Sverdrup 1953) which i n c l u d e d ba thymetry . I t p r e d i c t e d a g e n e r a l northward p r o g r e s s i o n i n the t ime of the o u t b u r s t f o l l o w i n g the s ea sona l i n c r e a s e of s o l a r r a d i a t i o n . However, t h i s p r o g r e s s i o n was not e n t i r e l y s e q u e n t i a l between ad jacent r e g i o n s , p a r t i c u l a r i l y Queen C h a r l o t t e Sound and Hecate S t r a i t . C o n d i t i o n s i n the n o r t h e r n S t r a i t of G e o r g i a were p r e d i c t e d to be a p p r o p r i a t e for a bloom d u r i n g February - M a r c h , i n Queen 170 C h a r l o t t e Sound by May or l a t e A p r i l , Hecate S t r a i t i n A p r i l , and Dixon Entrance in May. O b s e r v a t i o n s of the a c t u a l s p r i n g i n c r e a s e of p l a n k t o n by the s h i p of o p p o r t u n i t y program c o n f i r m e d t h i s p r e d i c t e d p a t t e r n , a l t h o u g h found there was l i t t l e d i f f e r e n c e in t i m i n g between Queen C h a r l o t t e Sound and Hecate S t r a i t , both of which had blooms d u r i n g A p r i l i n 1979 and 1 980. Diatoms were the major p h y t o p l a n k t o n component c o n t r i b u t i n g to the s p r i n g bloom, w i t h taxonomic c o m p o s i t i o n on the nor thern s h e l f s i m i l a r to that in the S t r a i t of Georg i a ( i . e . Skelet onema costatum, Thal assiosira spp. and Chaet oceros s p p . ) . Zooplankton were more abundant i n areas of p h y t o p l a n k t o n blooms, w i t h o c c a s i o n a l l o c a l o u t b u r s t s of b a r n a c l e n a u p l i i and decapod l a r v a e near shore i n s p e c i f i c a r e a s . The s i m i l a r t i m i n g of the d ia tom s p r i n g i n c r e a s e i n Queen C h a r l o t t e Sound and Hecate S t r a i t was not what was expec ted , c o n s i d e r i n g the d i s t a n c e they span a long the c o a s t . However, s p a t i a l v a r i a t i o n of p l a n k t o n biomass w i t h i n any one r e g i o n was c o n s i d e r a b l e , which made p r e c i s e d e f i n i t i o n of the t i m i n g of the bloom r a t h e r d i f f i c u l t . The e a r l i e s t s p r i n g blooms on the n o r t h e r n s h e l f d u r i n g the two year s of study o c c u r r e d i n western Hecate S t r a i t and sou thea s te rn Queen C h a r l o t t e Sound. In t h i s l a t t e r r e g i o n , the s p r i n g diatom i n c r e a s e o c c u r r e d by A p r i l in F i t z Hugh and Mi lbanke Sounds, then advanced towards Cape C a u t i o n and open Queen C h a r l o t t e Sound as s p r i n g p r o g r e s s e d . T h i s l e a d to a zone of i n c r e a s e d p l a n k t o n biomass a t the mouth 171 of F i t z Hugh Sound d u r i n g s p r i n g and summer, w h i l e Queen C h a r l o t t e S t r a i t r a r e l y showed ev idence of a phytop l ankton bloom i n t h i s s t u d y . V e r t i c a l temperature p r o f i l e s and r i v e r d i s c h a r g e s t a t i s t i c s suggest t h i s bloom may be i n i t i a t e d by f reshwater runof f and s t r a t i f i c a t i o n , and m a i n t a i n e d by n u t r i e n t s s u p p l i e d through entra inment of deeper water i n t o the su r f ace l a y e r , a l t h o u g h t h i s mechanism was not t e s t e d in t h i s t h e s i s . The development of t h i s bloom and zone of h i g h biomass may be important for the s u r v i v a l of j u v e n i l e sa lmonids i n t h i s a r e a . As t h i s bloom o c c u r r e d e a r l i e r than at most s t a t i o n s i n ocean ic Queen C h a r l o t t e Sound, i t may account for the d i s c r e p a n c y between the observed t i m i n g of the s p r i n g bloom and that p r e d i c t e d for Queen C h a r l o t t e Sound by the c r i t i c a l depth model . Nor thern Hecate S t r a i t was the o ther r e g i o n of the n o r t h e r n s h e l f i n which the s p r i n g diatom i n c r e a s e was f i r s t observed to o c c u r . S p e c i f i c a l l y , i t was the western par t of the s t r a i t where the p h y t o p l a n k t o n o u t b u r s t o c c u r r e d as e a r l y as the second week of A p r i l i n 1980. D u r i n g summer however, the area of h i g h p l a n k t o n biomass swi tched to the c e n t r a l and e a s t e r n s e c t i o n s of the s t r a i t . The p r i n c i p a l c h a r a c t e r i s t i c d i s t i n g u i s h i n g Hecate S t r a i t i s ba thymetry , wi th a sha l low bank (depths <30 m) on the western s i d e , w h i l e a deep t rough occur s on the e a s t e r n s i d e . I t i s t h i s c r o s s - s t r a i t v a r i a t i o n of bathymetry which i s r e s p o n s i b l e fo r the d i f f e r e n t b i o l o g i c a l c h a r a c t e r i s t i c s of east and west Hecate S t r a i t . 1 72 A c r i t i c a l depth model c a l c u l a t e d s e p a r a t e l y for e a s t e r n and western Hecate S t r a i t c o r r e c t l y p r e d i c t e d the observed development of the s p r i n g p h y t o p l a n k t o n bloom i n A p r i l on the western s i d e . T h i s e a r l y bloom o c c u r r e d because the sha l low water depth l i m i t e d the depth of the mixed l a y e r , and so i n c r e a s e d the mean l i g h t i n t e n s i t i e s to which c e l l s were exposed r e l a t i v e to the more deep ly mixed ea s te rn s i d e . T h i s e x t e n s i v e s h e l f i s the reason why the r e g i o n a l c r i t i c a l depth c a l c u l a t i o n s p r e d i c t e d a s p r i n g bloom i n Hecate S t r a i t e a r l i e r than Queen C h a r l o t t e Sound, and why the bloom was observed to occur i n A p r i l i n Hecate S t r a i t a l o n g w i t h the bloom i n s o u t h e a s t e r n Queen C h a r l o t t e Sound. The s w i t c h between s p r i n g and summer, from h i g h p l a n k t o n biomass and a taxonomic c o m p o s i t i o n dominated by diatoms on the western s i d e to the e a s t e r n s i d e of Hecate S t r a i t , can a l s o be a t t r i b u t e d to the e f f e c t of ba thymetry . Whi le d u r i n g s p r i n g the sha l low depths promoted c o n d i t i o n s f avourab le for p h y t o p l a n k t o n growth, once seasonal winds decrea sed and the e a s t e r n s i d e became s t r a t i f i e d d u r i n g summer, these same sha l low depths c r e a t e d l e s s f avourab le growth c o n d i t i o n s . C a l c u l a t i o n of the Simpson - Hunter (1974) s t r a t i f i c a t i o n parameter , based on water depth and mean t i d a l v e l o c i t i e s , p r e d i c t e d the deep e a s t e r n s i d e was l i k e l y to be s t r a t i f i e d and the sha l low western s i d e w e l l -mixed or t r a n s i t i o n a l d u r i n g summer. V e r t i c a l temperature p r o f i l e s r ecorded by the Imperial Tofino and c a l c u l a t i o n of a bulk s t r a t i f i c a t i o n parameter , conf i rmed these c h a r a c t e r i s t i c 1 73 mix ing zones . T h i s i m p l i e s a f r o n t shou ld occur between these zones , p a r t i c u l a r i l y in nor thwestern Hecate S t r a i t where the mix ing - s t r a t i f i c a t i o n g r a d i e n t i s s h a r p e s t . P l ankton biomass d i s t r i b u t i o n s conformed to the t y p i c a l p a t t e r n about f r o n t s i n the C e l t i c Sea ( e . g . P ingree 1978), and were low i n the w e l l - m i x e d r e g i o n , h igher in the s t r a t i f i e d r e g i o n , and h i g h e s t i n m i d - s t r a i t at the edge of the western s h e l f . I t i s a l s o i n t e r e s t i n g to note that the r i c h e s t g r o u n d f i s h f i s h i n g areas of Hecate S t r a i t occur on the s l o p e s of the western s h e l f , somewhat r e l a t e d to the zone of h ighes t b iomass . C o n s i d e r a t i o n of the c r o s s - s t r a i t d imens ions of the sha l low s h e l f , and the d imens ions of both s p r i n g and summer p l a n k t o n blooms, con f i rmed the importance of bathymetry in the development and l o c a t i o n of these blooms, a l t h o u g h by d i f f e r e n t mechanisms. It was a l s o c l e a r t h a t , a l t h o u g h present throughout the y e a r , t i d a l mix ing was an important mechanism i n i t i a t i n g p l a n k t o n blooms o n l y d u r i n g summer. Hecate S t r a i t can t h e r e f o r e be i n c l u d e d as another example of the a b i l i t y of the sha l low sea t i d a l f r o n t model to p r e d i c t mixed and s t r a t i f i e d water masses d u r i n g summer, even when there i s some degree of f reshwater i n f l u e n c e . Other such areas s t u d i e d to date i n c l u d e Long I s l a n d Sound (Bowman and E s a i a s 1981, Bowman et al. 1981), Hudson Bay ( G r i f f i t h s et al. 1981), and the G u l f of S t . Lawrence ( l i e s and S i n c l a i r 1982). However, there are two a s p e c t s of the system i n Hecate S t r a i t which are not c h a r a c t e r i s t i c of the usua l t i d a l f r o n t model : the near su r f ace 174 waters of Hecate S t r a i t were c o n s i s t e n t l y low i n n u t r i e n t s d u r i n g summer, and i t was the s t r a t i f i e d s ide which had the h i g h e r d ia tom biomass r a t h e r than the mixed s i d e , as d e s c r i b e d by H o l l i g a n et al. (1984) . C a l c u l a t i o n s of c r i t i c a l depths and mean l i g h t i n t e n s i t i e s d u r i n g summer for western Hecate S t r a i t i n d i c a t e t h e r e appears to be adequate l i g h t for net p h y t o p l a n k t o n growth, and i t i s t h e r e f o r e suggested p h y t o p l a n k t o n i n t h i s w e l l - m i x e d r e g i o n are l i m i t e d by the supply of n u t r i e n t s onto the s h e l f . The g r e a t e r biomass of diatoms on the e a s t e r n s i d e are l i k e l y s u p p l i e d w i t h n u t r i e n t s by s p o r a d i c mix ing of deeper water i n t o sur f ace l a y e r s due to the passage of s torms, w h i l e the western s ide i s p revented from a c c u m u l a t i n g a deep n u t r i e n t p o o l by i t s more v i g o r o u s t i d a l m i x i n g . T h i s may be an important d i s t i n c t i o n between the t i d a l mix ing model as a p p l i e d to s t r a i t s and to c o n t i n e n t a l s h e l f seas . In a reas where the water depth i s sha l low enough to prevent l i g h t l i m i t a t i o n , l i m i t a t i o n of p h y t o p l a n k t o n growth by n u t r i e n t s may become i m p o r t a n t . However, where t h i s sha l low mixed r e g i o n occur s w i t h i n an open sea or as a narrow s t r i p ad jacent to the shore , n u t r i e n t s may be s u p p l i e d from the s u r r o u n d i n g deep water by a d v e c t i o n onto the bank as suggested for Georges Bank by Cohen et al. (1982) . In the case of the s t r a i t , e s p e c i a l l y where the sha l low bank i s e x t e n s i v e and bounded on one or more s i d e s by l a n d , such a d v e c t i o n of deep, n u t r i e n t - r i c h water w i l l be r e s t r i c t e d and may not be s u f f i c i e n t 175 to r e s u p p l y the whole of the s h e l f . P lankton biomass in the mixed r e g i o n d u r i n g summer would then become l i m i t e d by the r a t e of n u t r i e n t r e s u p p l y , e i t h e r by a d v e c t i o n , or by b e n t h i c or in situ r e g e n e r a t i o n . 2. FUTURE STUDIES T h i s study i s the f i r s t to examine s p a t i a l and temporal d i s t r i b u t i o n s of p l a n k t o n on the B . C . n o r t h e r n s h e l f , and p o t e n t i a l p h y s i c a l mechanisms r e g u l a t i n g these d i s t r i b u t i o n s . I t has begun to answer such q u e s t i o n s as the k inds of organisms that occur and how they v a r y . These answers are i n c o m p l e t e , however, as the s h i p of o p p o r t u n i t y program sampled o n l y c e r t a i n a reas of the n o r t h e r n s h e l f w i t h any c o n s i s t e n c y , and even then w i t h a tempora l r e s o l u t i o n that was monthly at b e s t . They do form a b a s i s on which to make p r e d i c t i o n s about areas of the r e g i o n tha t were p o o r l y sampled, both i n terms of t h e i r p l a n k t o n d i s t r i b u t i o n s and u n d e r l y i n g p h y s i c a l p r o c e s s e s . C e n t r a l Queen C h a r l o t t e Sound i s an area w i t h important f i s h i n g s i t e s , for example Goose I s l a n d Bank and Cook Bank n o r t h of Vancouver I s l a n d , and w i t h c o n s i d e r a b l e b a t h y m e t r i c v a r i a t i o n , yet was p o o r l y sampled i n t h i s s t u d y . In these c h a c t e r i s t i c s i t i s s i m i l a r to Hecate S t r a i t , a l t h o u g h without the p r o t e c t i o n from d i r e c t ocean ic i n f l u e n c e p r o v i d e d by the Queen C h a r l o t t e I s l a n d s . S i m i l a r proces se s may t h e r e f o r e be o p e r a t i n g i n both a r e a s , w i t h tempora l p l a n k t o n d i s t r i b u t i o n s i n Queen C h a r l o t t e Sound p r e d i c t a b l e from study of Hecate S t r a i t . 1 76 The Goose I s l a n d Bank area may a l s o resemble Georges Bank, where a d v e c t i v e e f f e c t s , both onto and o f f the bank, can become very important ( e . g . Cohen et al . 1982). Future s t u d i e s i n the n o r t h e r n s h e l f r e g i o n would do w e l l to examine t h i s area i n d e t a i l w i t h these p r e d i c t i o n s as background. A l though s t u d i e d f a i r l y i n t e n s i v e l y in t h i s program, p l a n k t o n dynamics i n n o r t h e r n and c e n t r a l Hecate S t r a i t are s t i l l not c o m p l e t e l y known. Much b e t t e r temporal r e s o l u t i o n over a longer p e r i o d i s r e q u i r e d to c l e a r l y i d e n t i f y f a c t o r s i n i t i a t i n g the s p r i n g bloom, as w e l l as i t s i n t e r a n n u a l v a r i a b i l i t y and s p a t i a l e x t e n t . D u r i n g summer, when t i d a l mix ing i s the dominant p h y s i c a l p r o c e s s , b e t t e r s p a t i a l r e s o l u t i o n i s r e q u i r e d to e s t a b l i s h the p r e c i s e l o c a t i o n s of f r o n t a l and t r a n s i t i o n zones , the extent of t h e i r f l u c t u a t i o n s , and t h e i r i n f l u e n c e upon p l a n k t o n p r o d u c t i v i t y and d i s t r i b u t i o n s . A sugges t ion fo r such a study would be to use the B . C . f e r r i e s which t r a v e l between P r i n c e Rupert and Sandsp i t s e v e r a l t imes per week as s h i p s of o p p o r t u n i t y . The SHOP techniques of Royer and Emery (1982) and Boyd (1984), as w e l l as the present s tudy , would be most a p p r o p r i a t e . Other areas of the n o r t h e r n s h e l f p o o r l y s t u d i e d i n t h i s program, yet of i n t e r e s t for f u r t h e r s tudy , are Dixon E n t r a n c e and southern Hecate S t r a i t . Dixon Entrance i s of c o n s i d e r a b l e importance as a prime m i g r a t i o n route for salmon between the Skeena R i v e r and n o r t h e a s t P a c i f i c Ocean, yet has marked oceanographic and b i o l o g i c a l d i f f e r e n c e s between both n o r t h e r n 177 and s o u t h e r n , and e a s t e r n and western areas ( e . g . LeBrasseur 1956) which have been p o o r l y s t u d i e d . Southern Hecate S t r a i t i s a s i m i l a r a r e a . In a d d i t i o n to such r e g i o n a l q u e s t i o n s and hypotheses , t h i s s tudy a l s o i n t r o d u c e s s e v e r a l t h e o r e t i c a l q u e s t i o n s c o n c e r n i n g p r e c i s e mechanisms of i n c r e a s e d b i o l o g i c a l p r o d u c t i v i t y about f r o n t a l zones . No p r o d u c t i v i t y va lue s were e s t imated d u r i n g t h i s s tudy , an important o m i s s i o n which needs to be c o r r e c t e d i n fu ture work. E s p e c i a l l y neces sary are pr imary p r o d u c t i v i t y e s t imate s w i t h i n the f r o n t a l and h i g h biomass r e g i o n s of Hecate S t r a i t and s o u t h e a s t e r n Queen C h a r l o t t e Sound. T h i s would h e l p deve lop a more d e t a i l e d d e s c r i p t i o n of the proces se s by which f r o n t a l zones produce h i g h e r biomass by a d v e c t i o n or in situ p r o d u c t i o n . The r e s u l t s of t h i s study a l s o q u e s t i o n the c l a s s i c d e s c r i p t i o n of low biomass on the w e l l - m i x e d s ide of a t i d a l f r o n t due to l i g h t l i m i t a t i o n . In western Hecate S t r a i t , the water depth appears to be s u f f i c i e n t l y sha l low to prevent l i g h t l i m i t a t i o n compared w i t h the s t r a t i f i e d s i d e . What are needed are measurements of the a c t u a l r a t e s of v e r t i c a l mix ing i n both mixed and s t r a t i f i e d wate r s , and of the r e s u l t a n t mean l i g h t i n t e n s i t i e s e x p e r i e n c e d by p h y t o p l a n k t o n . Denman and Garge t t (1983) have made a s t a r t on such s t u d i e s , a l t h o u g h measurements i n s p e c i f i c f r o n t a l systems are s t i l l needed. N u t r i e n t uptake and r e g e n e r a t i o n r a t e s by phytop l ankton are o ther r a t e p roce s s t h a t need to be measured i n f r o n t a l systems. 1 78 Measurements of ambient n u t r i e n t c o n c e n t r a t i o n s are not e n t i r e l y s a t i s f a c t o r y for d e t e r m i n i n g b i o l o g i c a l p r o c e s s e s . For example, n u t r i e n t s are low i n near sur f ace waters d u r i n g summer ac ros s Hecate S t r a i t , yet there i s c o n s i d e r a b l e v a r i a t i o n of biomass . Such biomass i s presumably suppor ted by r a p i d uptake of n u t r i e n t s as they become a v a i l a b l e , wi th the l i m i t i n g proces s the r a t e at which such n u t r i e n t s are i n j e c t e d i n t o , or r egenera ted w i t h i n , the sur f ace l a y e r s (or a p p r o p r i a t e l i g h t r e g i m e ) . In the case of Hecate S t r a i t such n u t r i e n t s appear to be i n j e c t e d more f r e q u e n t l y on the e a s t e r n than western s i d e s . In t h e i r s tudy of f r o n t a l zones i n the E n g l i s h C h a n n e l , H o l l i g a n et al. (1984) a l s o noted low ambient n u t r i e n t c o n c e n t r a t i o n s (<1 MM N0 3 -N) throughout the mixed r e g i o n , which s t i l l supported h i g h e r p h y t o p l a n k t o n biomass than the s t r a t i f i e d s i d e . 3. GENERAL SUMMARY T h i s s tudy i s the f i r s t to examine the s p a t i a l and temporal b i o l o g i c a l oceanographic c h a r a c t e r i s t i c s of the B r i t i s h Columbia n o r t h e r n s h e l f . C o n s e q u e n t l y , i t s o b j e c t i v e s were r a t h e r b r o a d , concerned more wi th a . f i r s t overview of the r e g i o n and the g e n e r a l p h y s i c a l p roces se s i n i t i a t i n g p l a n k t o n blooms in s p r i n g and summer than w i t h s p e c i f i c d e t a i l s of l o c a l s p a t i a l or tempora l i n t e r e s t . I t s f i n d i n g s are in tended to serve as background to f i s h e r y management models and e n v i r o n m e n t a l s e n s i t i v i t y a n a l y s e s , and suggest f u r t h e r q u e s t i o n s and r e s e a r c h o p p o r t u n i t i e s for more d e t a i l e d s t u d i e s . 1 79 The two g e n e r a l o b j e c t i v e s were: 1. To examine the s p a t i a l and tempora l d i s t r i b u t i o n s of p l a n k t o n blooms on the B . C . n o r t h e r n s h e l f , i n c l u d i n g t h e i r p h y s i c a l and chemica l p r o p e r t i e s , p h y t o p l a n k t o n and zoop lankton biomass f l u c t u a t i o n s and taxonomic c o m p o s i t i o n ; and 2. To i n v e s t i g a t e p o t e n t i a l p h y s i c a l mechanisms i n i t i a t i n g p l a n k t o n blooms and r e g u l a t i n g t h e i r observed s p a t i a l and temporal d i s t r i b u t i o n s on the B . C . n o r t h e r n s h e l f . The c o n c l u s i o n s of t h i s s tudy have been summarized i n t h i s c h a p t e r , and i n the summaries at the end of each s p e c i f i c c h a p t e r . The p r i n c i p a l c o n c l u s i o n s are as f o l l o w s : - temporal p a t t e r n s of p l a n k t o n are t y p i c a l of o ther temperate l a t i t u d e c o a s t a l areas (Chapter 4 ) . - s p a t i a l p a t t e r n s of bloom i n i t i a t i o n are h i g h l y v a r i a b l e w i t h i n any one r e g i o n due to l o c a l oceanographic and ba thymetr i c c h a r a c t e r i s t i c s . T h i s i n tu rn c o m p l i c a t e s the temporal p a t t e r n of bloom outbreak w i t h i n each area (Chapter 4) . - the g e n e r a l p a t t e r n of i n i t i a t i o n of the s p r i n g bloom i s the S t r a i t of G e o r g i a , Queen C h a r l o t t e Sound and Hecate S t r a i t , Dixon E n t r a n c e . T h i s was both observed and p r e d i c t e d w i t h a c r i t i c a l depth model , a l t h o u g h a d i s c r e p a n c y o c c u r r e d w i t h Queen C h a r l o t t e Sound perhaps due to the incomplete sample o b s e r v a t i o n s i n t h i s r e g i o n (Chapter 4 ) . - t i d a l mix ing i s an important p h y s i c a l mechanism r e g u l a t i n g biomass d i s t r i b u t i o n s and blooms ac ro s s Hecate S t r a i t i n 180 summer. The sha l low western r e g i o n i s t i d a l l y the most e n e r g e t i c , and consequent ly had the lowest biomass . Phytop lankton p r o d u c t i o n i s suggested to be n u t r i e n t r a t h e r than l i g h t l i m i t e d . The f ront o c c u r r e d i n the c e n t r a l s t r a i t , w i th h i g h biomass a l s o on the e a s t e r n s ide (Chapter 5 ) . - t i d a l mix ing i s not an important mechanism i n f l u e n c i n g p l a n k t o n d i s t r i b u t i o n s i n winter or s p r i n g i n Hecate S t r a i t . I n s t e a d , bathymetry was conc luded to be the major f e a t u r e i n f l u e n c i n g seasona l p l a n k t o n c o m p o s i t i o n by d e c r e a s i n g the mixed l a y e r i n w i n t e r , and m a i n t a i n i n g i t d u r i n g summer (Chapter 6 ) . LITERATURE CITED A l a s k a , Dept . of F i s h and Game. 1979. C o a s t a l s ea sona l p r o c e s s e s , southwest summer c o n d i t i o n s , A p r i l - September, P r i n c e of Wales I s l a n d . A l a s k a Dept . of F i s h and Game, M a r . / C o a s t . H a b i t a t Manage. Anchorage , AK. A l l e n , W . E . 1927. Sur face ca t ches of marine diatoms and d i n o f l a g e l l a t e s made by the U . S . S . Pioneer i n A la skan waters i n 1923. B u l l . S c r i p p s I n s t . Oceanogr . T e c h . S e r . 1: 39-48. A i k e n , J . 1981. The u n d u l a t i n g oceanographic r e c o r d e r Mark 2. J . P l ankton Res . 3: 551-560. Ander son , G . C . and R . E . Munson. 1972. 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R. Soc . L o n d . A302(1472) : 511-693. Sweet, S . T . and N . L . G u i n a s s o , J r . 1984. E f f e c t s of flow r a t e on f l u o r e s c e n c e i n v i v o d u r i n g c o n t i n u o u s measurements on G u l f of Mexico sur f ace water . L i m n o l . Oceanogr . 29: 397-401. T a b a t a , S. 1958. Heat budget of the water i n the v i c i n i t y of T r i p l e I s l a n d , B r i t i s h C o l u m b i a . J . F i s h . Res . Board Can. 15: 429-451. T a b a t a , S. 1980. An i n v e n t o r y of p h y s i c a l oceanographic i n f o r m a t i o n for the waters of Queen C h a r l o t t e Sound, Hecate S t r a i t , Dixon Ent rance and t h e i r v i c i n i t y . P a c i f i c Marine S c i e n c e Rept . 80-7 . I n s t i t u t e of Ocean S c i e n c e s , S i d n e y , B . C . T a y l o r , F . H . C . 1964. L i f e h i s t o r y and present s t a t u s of B r i t i s h Columbia h e r r i n g s t o c k s . F i s h . Res . Board Can . B u l l . 143: 8 l p . T h e r r i a u l t , J . - C , D . L . Lawrence and T . P i a t t . 1978. S p a t i a l v a r i a b i l i t y of p h y t o p l a n k t o n t u r n o v e r i n r e l a t i o n to p h y s i c a l p roce s se s i n a c o a s t a l env i ronment . L i m n o l . Oceanogr . 23: 900-911. 197 Thomson, R . E . 1981. Oceanography of the B r i t i s h Columbia c o a s t . Can . Spec. P u b l . F i s h . Aquat . S c i . 56: 2 9 l p . Thomson, R . E . 1983. A comparison between computed and measured ocean ic winds near the B r i t i s h Columbia c o a s t . J . Geophys. Res . 88 (C4) : 2675-2683. T u r p i n , D . H . and P . J . H a r r i s o n . 1979. L i m i t i n g n u t r i e n t p a t c h i n e s s and i t s r o l e i n p h y t o p l a n k t o n e c o l o g y . J . Exp. Mar. B i o l . E c o l . 39: 151-166. U t e r m o h l , H . 1958. Zur vervolkommnung der q u a n t i t a t i v e n p h y t o p l a n k t o n methodik . I n t . V e r . T h e o r . Angew. M i t t . I n t . V e r . L i m n o l . 9: 38p. Vermeer , K. 1981. The importance of p l a n k t o n to C a s s i n ' s a u k l e t s d u r i n g b r e e d i n g . J . P lankton Res . 3: 315-329. Wald i chuk , M. 1957. P h y s i c a l oceanography of the S t r a i t of G e o r g i a , B r i t i s h C o l u m b i a . J . F i s h . Res . Board Can . 14: 321-486. Walker , T . A . 1980. A c o r r e c t i o n to the Poole and A t k i n s s e c c h i d i s k / l i g h t a t t e n u a t i o n f o r m u l a . J . Mar . B i o l . A s s o c . U . K . 60: 769-771. Wal sh , J . J . , T . E . W h i t l e d g e , F .W. B a r v e n i k , C D . W i r i c k and S . O . Howe. 1978. Wind events and food c h a i n dynamics w i t h i n the New York B i g h t . L i m n o l . Oceanogr . 23: 659-683. Warwick, R . M . and R . J . U n c l e s . 1980. D i s t r i b u t i o n of b e n t h i c macrofauna a s s o c i a t i o n s i n the B r i s t o l Channel i n r e l a t i o n to t i d a l s t r e s s . Mar . E c o l . P r o g . S e r . 3: 97-103. Water Resources B r a n c h . 1977. H i s t o r i c a l s treamflow summary, B r i t i s h Columbia 1976. Dept . of F i s h e r i e s and the Env i ronment . Ottawa. W i t h l e r , F . C . and F . Y . C . Wong. 1983. C a t c h , o r i g i n , d i s t r i b u t i o n 198 and growth of P a c i f i c salmon i n Hecate S t r a i t . Can . T e c h . Rept . F i s h . Aquat . S c i . No. 1173: 38p. Woods, J . D . and R. Onken. 1982. D i u r n a l v a r i a t i o n and pr imary p r o d u c t i o n i n the ocean - p r e l i m i n a r y r e s u l t s of a Lagrang ian ensemble model . J . P l ankton Res . 4: 735-756. W y r t k i , K. 1967. The spectrum of ocean t u r b u l e n c e over d i s t a n c e s between 40 and 1000 k i l o m e t e r s . Deutsche Hydrograph i s che Z e i t s c h r i f t 20: 176-187. APPENDIX I S t a t i o n l o c a t i o n s for each c r u i s e of the Imperial Tofino s h i p of o p p o r t u n i t y program. O r i g i n a l data are a v a i l a b l e i n D i l k e et at. (1979) for C r u i s e s 1 to 8, and Per ry et al. (1981) for C r u i s e s 9 to 14. CRUISE 1 13 -- 20 March 1 978 STATION DAY/MO/YR TIME POSITION 01 13/03/78 1 600 5 4 ° 2 9 ' N 1 3 1 ° 1 7 ' W 02 14/03/78 0200 5 3 ° 3 9 ' N 1 3 3 ° 1 1 ' W 03 14/03/78 1 500 5 3 ° 4 6 ' N 1 3 3 ° 1 2 ' W 04 16/03/78 0300 5 3 ° 5 9 ' N 1 3 0 ° 1 3 ' W 05 18/03/78 1 400 5 0 ° 4 2 ' N 1 2 6 ° 4 9 ' W 06 19/03/78 21 00 5 0 ° 4 2 ' N 1 2 6 ° 3 3 ' W 07 20/03/78 1 020 4 9 ° 2 5 ' N 1 2 3 ° 5 0 ' W 199 200 APPENDIX I (Cont inued) CRUISE 3 24 J u l y - 3 August 1978 STATION DAY/MO/YR TIME POSITION 01 24/07/78 1 830 5 0 ° 2 1 ' N 1 2 5 ° 0 8 ' W 02 24/07/78 2300 5 0 ° 2 2 ' N 1 2 4 ° 2 2 ' W 03 25/07/78 1 000 5 1 0 1 7 'N 1 2 7 ° 4 3 ' W 04 25/07/78 1 900 5 1 ° 2 3 ' N 1 2 7 ° 4 9 ' W 05 26/07/78 0800 5 1 ° 4 6 ' N 1 2 7 ° 5 5 ' W 06 26/07/78 1250 5 2 ° 1 5 ' N 1 2 8 ° 1 7 ' W 07 26/07/78 1 630 5 2 ° 3 4 ' N 1 2 8 ° 2 9 ' W 08 26/07/78 1900 5 2 ° 5 8 ' N 1 2 8 ° 3 1 ' W 09 26/07/78 2245 5 3 ° 1 9 ' N 1 2 8 ° 5 6 ' W 10 27/07/78 071 5 5 4 ° 0 9 ' N 1 3 0 ° 2 0 ' W 1 1 27/07/78 2300 5 3 ° 5 6 ' N 1 3 0 ° 5 4 ' W 1 2 28/07/78 0030 5 3 ° 4 5 ' N 1 3 1 ° 1 4 ' W 1 3 28/07/78 1 500 5 3 ° 2 9 ' N 1 3 1 ° 3 0 ' W 1 4 28/07/78 2400 5 3 ° 4 0 ' N 1 3 0 ° 2 5 ' W 1 5 29/07/78 1 900 5 4 ° 1 8 ' N 1 3 0 ° 3 4 ' W 1 6 30/07/78 0600 5 4 ° 5 1 ' N 1 3 0 ° 1 3 ' W 1 7 31/07/78 2355 5 3 ° 2 2 ' N 1 2 9 ° 1 9 ' W 18 02/08/78 0615 5 2 ° 2 0 ' N 1 2 7 ° 0 5 ' W 1 9 02/08/78 1810 5 1 ° 3 7 ' N 1 2 7 ° 5 3 ' W 20 03/08/78 0630 5 1 ° 0 0 ' N 1 2 8 ° 0 0 ' W 21 03/08/78 1810 5 0 ° 4 0 ' N 1 2 7 ° 1 3 ' W 22 03/08/78 2345 5 0 ° 2 9 ' N 1 2 6 ° 1 1 ' W 201 APPENDIX I (Cont inued) CRUISE 4 1 2 - 2 7 August 1978 STATION DAY/MO/YR TIME POSITION 01 12/08/78 0840 5 0 ° 0 0 ' N 1 2 4 ° 5 1 ' W 02 12/08/78 1 530 5 0 ° 2 5 ' N 1 2 4 ° 3 0 ' W 03 12/08/78 1 840 50 ° 1 1 ' N 1 2 4 ° 3 5 ' W 04 12/08/78 2335 4 9 ° 3 2 ' N 1 2 4 ° 0 6 ' W 05 13/08/78 1 1 35 4 8 ° 2 5 ' N 1 2 4 ° 1 0 ' W 06 13/08/78 1 735 4 8 ° 5 0 ' N 1 2 5 ° 1 0 ' W 07 14/08/78 1 235 4 9 ° 4 0 ' N 1 2 6 ° 1 2 ' W 08 14/08/78 1 635 4 9 ° 4 6 * N 1 2 6 ° 2 8 ' W 09 15/08/78 0635 4 9 ° 5 0 ' N 1 2 7 ° 0 2 ' W 10 15/08/78 1 240 5 0 ° 0 0 ' N 1 2 7 ° 3 2 ' W 1 1 15/08/78 1 646 5 0 ° 3 0 ' N 1 2 8 ° 2 0 ' W 12 16/08/78 0006 5 0 ° 4 7 ' N 1 2 7 ° 3 0 ' W 1 3 16/08/78 0930 5 1 ° 0 6 ' N 1 2 7 ° 4 8 ' W 1 4 16/08/78 1 252 5 1 ° 1 7 ' N 1 2 7 ° 2 0 ' W 1 5 16/08/78 1800 5 1 ° 1 8 ' N 1 2 7 ° 4 1 'W 1 6 16/08/78 2321 5 1 ° 3 4 ' N 1 2 7 ° 3 4 ' W 1 7 17/08/78 1 530 5 1 ° 5 5 ' N 1 2 7 ° 5 4 ' W 18 17/08/78 1 730 5 2 ° 1 0 ' N 1 2 8 ° 0 8 ' W 1 9 18/08/78 0620 5 3 ° 1 3 ' N 1 2 8 ° 4 6 ' W 20 18/08/78 1 240 5 3 ° 2 3 ' N 1 2 9 ° 1 7 ' W 21 19/08/78 1 1 23 5 4 ° 1 7 ' N 1 3 1 ° 2 2 ' W 22 19/08/78 1400 5 4 ° 0 6 ' N 1 3 1 ° 4 8 ' W 23 19/08/78 1830 5 4 ° 1 0 ' N 1 3 2 ° 2 8 ' W 24 19/08/78 2340 5 3 ° 4 6 ' N 1 3 3 ° 1 2 ' W 25 20/08/78 1 600 54 ° 1 1 ' N 1 3 2 ° 4 5 ' W 26 21/08/78 0630 5 3 ° 1 7 ' N 1 3 1 ° 5 3 ' W 27 21/08/78 1 930 5 3 ° 2 6 ' N 1 3 1 ° 4 6 ' W 28 22/08/78 061 5 5 3 ° 5 5 ' N 1 3 0 ° 1 4 ' W 29 22/08/78 1840 5 4 ° 1 3 ' N 1 3 0 ° 2 4 ' W 30 22/08/78 2340 5 4 ° 3 7 ' N 1 3 0 ° 4 1 ' W 31 24/08/78 1 930 5 2 ° 3 4 ' N 1 2 8 ° 3 0 ' W 32 25/08/78 0930 5 2 ° 2 3 ' N 1 2 7 ° 2 7 ' W 33 25/08/78 1 700 5 2 ° 1 6 ' N 1 2 7 ° 1 7 ' W 34 26/08/78 21 30 5 0 ° 3 6 ' N 1 2 7 ° 0 1 ' W 35 27/08/78 0700 5 0 ° 0 8 ' N 1 2 5 ° 2 0 ' W 36 27/08/78 1 200 4 9 ° 3 5 ' N 1 2 4 ° 2 3 ' W 37 27/08/78 1 500 4 9 ° 2 5 ' N 1 2 3 ° 4 5 ' W 202 APPENDIX I (Cont inued) CRUISE 5 1 1 - 2 7 September 1978 STATION DAY/MO/YR TIME POSITION 01 11/09/78 2200 4 8 ° 5 7 ' N 1 2 3 ° 2 0 ' W 02 12/09/78 0600 4 8 ° 2 5 ' N 1 2 4 ° 2 2 ' W 03 12/09/78 1 300 4 9 ° 0 6 ' N 1 2 5 ° 5 5 ' W 04 14/09/78 071 5 4 9 ° 5 1 ' N 1 2 7 ° 1 3 ' W 05 14/09/78 221 0 4 9 ° 1 8 ' N 1 2 6 ° 3 0 ' W 06 15/09/78 0330 4 8 ° 3 9 * N 1 2 5 ° 0 9 ' W 07 15/09/78 1 050 4 8 ° 1 8 ' N 1 2 3 ° 2 8 ' W 08 16/09/78 2305 4 9 ° 4 9 ' N 1 2 4 ° 3 4 ' W 09 17/09/78 1 600 5 0 ° 2 0 ' N 1 2 5 ° 0 9 * W 10 17/09/78 2330 5 0 ° 3 3 ' N 1 2 6 ° 4 5 ' W 1 1 18/09/78 1 600 5 1 ° 2 7 ' N 1 2 7 ° 5 0 ' W 1 2 19/09/78 1 400 5 3 ° 1 8 ' N 1 2 9 ° 0 4 ' W 13 20/09/78 1 1 45 5 4 ° 3 2 ' N 1 3 0 ° 3 2 ' W 1 4 21/09/78 1 1 45 5 3 ° 2 4 ' N 1 3 2 ° 3 6 ' W 1 5 22/09/78 0900 5 3 ° 3 3 ' N 1 3 1 ° 4 5 ' W 16 22/09/78 2340 5 3 ° 3 2 ' N 1 3 1 ° 2 2 ' W 17 24/09/78 1 230 5 3 ° 4 9 ' N 1 3 0 ° 1 9 ' W 18 24/09/78 1 505 5 3 ° 4 1 ' N 1 2 9 ° 4 7 ' W 1 9 25/09/78 0930 5 2 ° 5 3 ' N 1 2 8 ° 3 2 ' W 20 25/09/78 1830 5 2 ° 1 6 ' N 1 2 7 ° 4 3 ' W 21 26/09/78 1205 5 2 ° 0 5 ' N 1 2 8 ° 0 6 ' W 22 27/09/78 0600 5 0 ° 4 1 ' N 1 2 7 ° 1 5 ' W 23 27/09/78 1 245 5 0 ° 2 6 ' N 1 2 5 ° 5 6 ' W 24 27/09/78 1 730 4 9 ° 5 7 ' N 1 2 5 ° 0 7 ' W 203 APPENDIX I (Cont inued) CRUISE 6 1 8 - 2 6 October 1978 STATION DAY/MO/YR TIME POSITION 01 18/10/78 21 00 5 4 ° 0 7 ' N 1 3 1 ° 4 9 ' W 02 18/10/78 2345 5 4 ° 1 1 ' N 1 3 2 ° 2 5 ' W 03 19/10/78 0300 5 4 ° 0 9 ' N 1 3 3 ° 1 0 ' W 04 19/10/78 0600 5 3 ° 4 1 ' N 1 3 3 ° 0 9 ' W 05 19/10/78 1815 5 3 ° 4 6 * N 1 3 3 ° 1 2 ' W 06 20/10/78 0630 5 3 ° 5 4 ' N 1 3 1 ° 3 4 ' W 07 20/10/78 0900 5 3 ° 3 2 * N 1 3 1 ° 4 5 ' W 08 20/10/78 2315 5 3 ° 3 2 ' N 1 3 1 ° 1 8 ' W 09 21/10/78 1 320 5 4 ° 1 3 ' N 1 3 0 ° 2 4 ' W 1 0 21/10/78 2110 5 4 ° 3 2 ' N 1 3 0 ° 3 2 ' W 1 1 22/10/78 2135 5 3 ° 5 2 ' N 1 3 0 ° 0 3 ' W 1 2 22/10/78 231 0 5 3 ° 4 1 ' N 1 2 9 ° 4 7 ' W 1 3 23/10/78 1 500 5 3 ° 2 0 ' N 1 2 9 ° 0 0 ' W 14 23/10/78 1 645 5 3 ° 1 2 ' N 1 2 8 ° 4 0 ' W 1 5 23/10/78 2330 5 2 ° 1 8 ' N 1 2 8 ° 3 0 ' W 16 24/10/78 1 430 5 1 ° 4 6 ' N 1 2 7 ° 5 6 ' W 1 7 24/10/78 1 545 5 1 ° 2 3 ' N 1 2 7 ° 5 0 ' W 18 24/10/78 1845 5 0 ° 5 8 ' N 1 2 7 ° 3 2 ' W 1 9 24/10/78 201 5 5 0 ° 4 4 ' N 1 2 7 ° 1 7 ' W 20 25/10/78 1 1 30 5 0 ° 2 9 ' N 1 2 6 ° 1 3 ' W 21 25/10/78 221 0 5 0 ° 2 1 ' N 1 2 5 ° 0 7 ' W 22 26/10/78 0330 4 9 ° 3 9 ' N 1 2 4 ° 1 4 ' W 204 APPENDIX I (Cont inued) CRUISE 7 2 - 7 January 1979 STATION DAY/MO/YR TIME POSITION 01 02/01/79 1815 4 9 ° 4 3 ' N 1 2 4 ° 4 3 ' W 02 02/01/79 2330 5 0 ° 2 2 ' N 1 2 5 ° 4 4 ' W 03 03/01/79 0622 5 0 ° 4 7 ' N 1 2 7 ° 2 7 ' W 04 03/01/79 1 1 36 5 1 ° 0 8 ' N 1 2 8 ° 4 7 ' W 05 03/01/79 2345 5 2 ° 0 9 ' N 1 3 1 ° 2 8 ' W 06 04/01/79 1810 5 3 ° 2 9 ' N 1 3 2 ° 5 9 ' W 07 05/01/79 0635 5 3 ° 5 6 ' N 1 3 1 ° 3 4 ' W 08 05/01/79 2400 5 3 ° 1 6 ' N 1 3 1 ° 1 3 ' W 09 07/01/79 1 708 5 0 ° 2 1 ' N 1 2 5 ° 0 7 ' W 205 APPENDIX I (Cont inued) CRUISE 8 30 March - 8 A p r i l 1979 STATION DAY/MO/YR TIME POSITION 01 30/03/79 2300 5 0 ° 2 1 ' N 1 2 5 ° 0 7 ' W 02 01/04/79 0330 5 0 ° 4 5 ' N 1 2 7 ° 0 8 ' W 03 01/04/79 1 1 30 5 0 ° 4 8 ' N 1 2 7 ° 0 6 ' W 04 01/04/79 2100 5 1 ° 0 9 ' N 1 2 7 ° 4 8 ' W 05 02/04/79 01 00 5 1 ° 5 3 ' N 1 2 7 ° 5 7 ' W 06 02/04/79 0830 5 2 ° 1 8 ' N 1 2 9 ° 0 6 ' W 07 02/04/79 1415 5 2 ° 4 8 ' N 1 3 0 ° 3 3 ' W 08 02/04/79 1910 5 3 ° 2 2 ' N 1 3 1 ° 4 2 ' W 09 03/04/79 1 245 5 4 ° 1 0 ' N 1 3 0 ° 2 4 ' W 10 04/04/79 0830 5 4 ° 1 8 ' N 1 3 0 ° 3 6 ' W 1 1 05/04/79 2230 5 3 ° 1 8 ' N 1 2 8 ° 5 4 ' W 1 2 06/04/79 1 000 5 2 ° 1 8 * N 1 2 8 ° 2 9 ' W 1 3 07/04/79 01 00 5 1 ° 2 7 ' N 1 2 7 ° 4 6 ' W 1 4 08/04/79 0330 5 0 ° 3 2 ' N 1 2 6 ° 4 0 ' W 1 5 08/04/79 0700 5 0 ° 2 4 ' N 1 2 5 ° 5 3 ' W 16 08/04/79 1 1 00 4 9 ° 5 8 ' N 1 2 5 ° 0 9 ' W 1 7 08/04/79 1 230 4 9 ° 4 6 ' N 1 2 4 ° 4 7 ' W 18 08/04/79 1 500 4 9 ° 3 3 ' N 1 2 4 ° 1 8 ' W 19 08/04/79 1 700 4 9 ° 2 3 ' N 1 2 3 ° 4 4 ' W 206 APPENDIX I (Cont inued) CRUISE 9 8 - 1 7 May 1979 STATION DAY/MO/YR TIME POSITION 01 08/05/79 2230 4 9 ° 3 8 ' N 1 2 4 ° 1 2 ' W 02 09/05/79 1 225 5 0 ° 2 0 ' N 1 2 5 ° 0 6 ' W 03 09/05/79 1815 5 0 ° 3 0 ' N 1 2 6 ° 2 3 ' W 04 10/05/79 1 630 5 0 ° 5 6 ' N 1 2 7 ° 4 2 ' W 05 10/05/79 201 5 5 1 ° 4 7 ' N 1 2 7 ° 5 5 ' W 06 11/05/79 0440 5 2 ° 2 0 ' N 1 2 8 ° 3 0 ' W 07 11/05/79 1015 5 3 ° 1 1 'N 1 2 8 ° 4 8 ' W 08 11/05/79 1 900 5 3 ° 0 5 ' N 1 3 0 ° 0 2 ' W 09 12/05/79 0035 5 3 ° 2 4 ' N 1 3 1 ° 3 3 ' W 1 0 12/05/79 201 5 5 4 ° 0 0 ' N 1 3 0 ° 4 6 ' W 1 1 12/05/79 221 5 54 ° 1 1 ' N 1 3 0 ° 2 1 ' W 1 2 13/05/79 1720 5 4 ° 5 1 'N 1 3 0 ° 1 3 ' W 1 3 13/05/79 2355 5 4 ° 3 4 ' N 1 3 0 ° 3 0 ' W 1 4 14/05/79 2030 5 3 ° 4 2 ' N 1 2 9 ° 4 7 ' W 1 5 15/05/79 0330 5 3 ° 2 4 * N 1 2 9 ° 1 3 ' W 1 6 15/05/79 1 420 5 3 ° 1 1'N 1 2 9 ° 4 8 ' W 1 7 15/05/79 2130 5 2 ° 2 1 ' N 1 2 8 ° 3 1 ' W 18 16/05/79 0700 5 1 ° 2 4 ' N 1 2 7 ° 5 0 ' W 1 9 16/05/79 1 545 5 1 ° 0 9 ' N 1 2 7 ° 4 8 ' W 20 17/05/79 0030 5 0 ° 2 2 ' N 1 2 5 ° 4 1 ' W 21 17/05/79 1010 4 9 ° 3 5 ' N 1 2 4 ° 0 5 ' W 207 APPENDIX I (Cont inued) CRUISE 10 19 June - 1 J u l y 1979 STATION DAY/MO/YR TIME POSITION 01 19/06/79 2200 4 9 ° 4 3 ' N 1 2 4 ° 2 0 ' W 02 20/06/79 0020 4 9 ° 2 3 ' N 1 2 4 ° 0 0 ' W 03 20/06/79 0620 4 9 ° 1 4 ' N 1 2 3 ° 4 4 ' W 04 20/06/79 0705 4 9 ° 1 7 ' N 1 2 3 ° 3 2 ' W 05 21/06/79 1900 5 0 ° 2 1 ' N 1 2 5 ° 0 7 ' W 06 21/06/79 2400 5 0 ° 2 1 'N 1 2 5 ° 3 2 ' W 07 23/06/79 0530 5 0 ° 4 2 ' N 1 2 7 ° 1 6 ' W 08 23/06/79 2015 5 1 ° 1 0 ' N 1 2 7 ° 5 0 ' W 09 24/06/79 0730 5 1 ° 2 3 ' N 1 2 7 ° 4 9 ' W 10 24/06/79 2030 5 1 ° 4 7 ' N 1 2 7 ° 5 5 ' W 1 1 25/06/79 1415 5 3 ° 1 1 ' N 1 2 8 ° 4 3 ' W 1 2 26/06/79 0315 5 3 ° 2 2 ' N 1 2 9 ° 1 3 ' W 1 3 27/06/79 0730 5 4 ° 3 6 ' N 1 3 0 ° 3 2 ' W 1 4 27/06/79 1 030 5 4 ° 3 0 ' N 1 3 1 ° 0 5 ' W 1 5 27/06/79 1210 5 4 ° 1 4 ' N 1 3 1 ° 1 6 ' W 1 6 27/06/79 1805 5 3 ° 1 8 ' N 1 3 1 ° 5 6 ' W 17 28/06/79 0845 5 3 ° 4 2 ' N 131 017'W 18 28/06/79 1 035 5 3 ° 5 3 ' N 1 3 0 ° 5 9 ' W 1 9 28/06/79 1 300 5 4 ° 0 9 ' N 1 3 0 ° 2 4 ' W 20 30/06/79 0800 5 2 ° 1 7 ' N 1 2 8 ° 2 9 ' W 21 01/07/79 0800 5 0 ° 2 5 ' N 1 2 5 ° 5 3 ' W 22 01/07/79 1215 4 9 ° 5 5 ' N 1 2 5 ° 0 3 *W 23 01/07/79 1 730 4 9 ° 2 5 ' N 1 2 3 ° 5 2 ' W 208 APPENDIX I (Continued) CRUISE 11 13 - 29 J u l y 1979 STATION DAY/MO/YR TIME POSITION 01 13/07/79 21 20 4 9 ° 4 0 ' N 1 2 4 ° 1 7 ' W 02 14/07/79 1 430 5 0 ° 2 1 ' N 1 2 5 ° 0 8 ' W 03 16/07/79 0200 5 0 ° 4 5 ' N 1 2 7 ° 1 0 ' W 04 17/07/79 0300 5 1 ° 1 5 ' N 1 2 7 ° 4 9 ' W 05 17/07/79 1000 5 1 ° 4 7 ' N 1 2 7 ° 5 5 ' W 06 18/07/79 1225 • 5 2 ° 2 5 ' N 1 2 8 ° 3 0 ' W 07 21/07/79 0955 5 4 ° 1 5 ' N 1 3 1 ° 4 7 ' W 08 21/07/79 1 1 45 5 4 ° 1 3 ' N 1 3 2 ° 2 6 ' W 09 21/07/79 1 745 5 3 ° 4 6 ' N 1 3 3 ° 1 2 ' W 1 0 22/07/79 0355 5 3 ° 2 5 ' N 1 3 2 ° 4 0 ' W 1 1 22/07/79 1 530 5 4 ° 1 8 ' N 1 3 1 ° 1 6 ' W 1 2 23/07/79 21 45 5 4 ° 5 1 ' N 1 3 0 ° 1 3 ' W 1 3 24/07/79 1 750 5 4 ° 0 9 ' N 1 3 0 ° 2 3 ' W 1 4 24/07/79 1 930 5 4 ° 0 0 ' N 1 3 0 ° 4 6 ' W 1 5 24/07/79 2040 5 3 ° 5 2 ' N 1 3 1 ° 0 0 ' W 1 6 24/07/79 2200 5 3 ° 4 1 ' N •131 ° 2 1 ' W 17 24/07/79 2400 5 3 ° 2 5 ' N 1 3 1 ° 5 2 ' W 18 26/07/79 1210 5 3 ° 1 0 ' N 1 2 9 ° 0 6 ' W 1 9 26/07/79 1 520 5 3 ° 1 0 ' N 1 2 8 ° 3 9 ' W 20 27/07/79 2400 5 1 ° 1 0 ' N 1 2 7 ° 5 2 ' W 21 28/07/79 1 630 5 0 ° 2 0 ' N 1 2 5 ° 2 5 ' W 22 28/07/79 1850 4 9 ° 5 5 ' N 1 2 5 ° 0 3 ' W 23 29/07/79 0010 4 9 ° 2 5 * N 1 2 3 ° 5 2 ' W 209 APPENDIX I (Cont inued) CRUISE 12 30 January - 9 February 1980 STATION DAY/MO/YR TIME POSITION 01 30/01/80 1 1 30 4 9 ° 2 9 ' N 1 2 4 ° 0 8 ' W 02 30/01/80 1 220 4 9 ° 3 5 ' N 1 2 4 ° 2 4 ' W 03 30/01/80 1 400 4 9 ° 4 6 ' N 1 2 4 ° 4 5 ' W 04 30/01/80 1 500 4 9 ° 5 7 ' N 1 2 4 ° 5 8 ' W 05 30/01/80 1 550 4 9 ° 5 8 ' N 1 2 5 ° 1 0 ' W 06 30/01/80 2400 5 0 ° 2 8 ' N 1 2 6 ° 1 0 ' W 07 31/01/80 0200 5 0 ° 2 9 ' N 1 2 6 ° 2 0 ' W 08 31/01/80 1 500 5 1 ° 0 2 ' N 1 2 7 ° 4 8 ' W 09 31/01/80 1 530 5 1 ° 0 7 ' N 1 2 7 ° 4 9 ' W 10 31/01/80 1 600 51 ° 1 1 *N 1 2 7 ° 4 9 ' W 1 1 01/02/80 01 30 5 1 ° 3 2 ' N 1 2 7 ° 5 2 ' W 1 2 01/02/80 0330 5 1 ° 4 7 ' N 1 2 7 ° 5 5 ' W 1 3 01/02/80 2000 5 2 ° 1 6 ' N 1 2 8 ° 2 5 ' W 1 4 01/02/80 2030 5 2 ° 2 1 ' N 1 2 8 ° 3 1 ' W 1 5 02/02/80 1 1 30 5 4 ° 0 8 ' N 1 3 0 ° 1 9 ' W 1 6 03/02/80 0315 5 3 ° 4 3 ' N 1 3 0 ° 2 5 ' W 17 03/02/80 0345 5 3 ° 4 1 ' N 1 3 0 ° 3 4 ' W 18 03/02/80 041 5 5 3 ° 3 9 ' N 1 3 0 ° 4 2 ' W 1 9 03/02/80 • 0445 5 3 ° 3 7 ' N 1 3 0 ° 5 1 ' W 20 03/02/80 051 5 5 3 ° 3 6 ' N 1 3 0 ° 5 9 ' W 21 03/02/80 061 5 5 3 ° 3 2 ' N 1 3 1 ° 1 4 ' W 22 04/02/80 0100 5 3 ° 1 7 ' N 1 3 1 ° 5 4 ' W 23 04/02/80 0200 5 3 ° 2 5 ' N 1 3 1 ° 5 0 ' W 24 04/02/80 0230 5 3 ° 2 7 ' N 1 3 1 ° 4 1 'W 25 04/02/80 0300 5 3 ° 2 9 ' N 1 3 1 ° 3 7 'W 26 04/02/80 0400 5 3 ° 3 3 ' N 1 3 1 ° 2 1 *W 27 04/02/80 0500 5 3 ° 3 7 ' N 1 3 1 ° 0 7 ' W 28 05/02/80 1 1 00 5 4 ° 2 5 ' N 1 3 0 ° 3 4 ' W 29 05/02/80 1 225 5 4 ° 1 2 ' N 1 3 0 ° 2 8 ' W 30 05/02/80 1 640 5 3 ° 4 1 ' N 1 2 9 ° 4 9 ' W 31 05/02/80 1 920 5 3 ° 2 1 1 N 1 2 9 ° 1 4 ' W 32 06/02/80 0820 5 3 ° 3 8 ' N 1 2 8 ° 3 5 ' W 33 06/02/80 1 500 5 2 ° 1 8 ' N 1 2 8 ° 2 8 ' W 34 06/02/80 2230 5 1 ° 3 0 ' N 1 2 8 ° 1 5 ' W 35 06/02/80 2345 5 1 ° 1 7 ' N 1 2 8 ° 1 8 ' W 36 07/02/80 2050 5 0 ° 5 2 ' N 1 2 8 ° 1 3 ' W 37 09/02/80 071 5 5 0 ° 2 1 ' N 1 2 5 ° 0 8 ' W 38 09/02/80 1210 4 9 ° 3 9 ' N 1 2 4 ° 1 3 ' W 210 APPENDIX I (Cont inued) CRUISE 13 1 0 - 1 6 A p r i l 1980 STATION DAY/MO/YR TIME POSITION 01 10/04/80 1 1 40 5 0 ° 2 1 ' N 1 2 5 ° 0 7 ' W 02 10/04/80 1 300 5 0 ° 2 8 ' N 1 2 5 ° 2 1 'W 03 10/04/80 1 500 5 0 ° 2 8 ' N 1 2 6 ° 0 0 ' W 04 10/04/80 1 600 5 0 ° 3 0 ' N 1 2 6 ° 1 8 ' W 05 10/04/80 1800 5 0 ° 3 4 ' N 1 2 6 ° 5 1 ' W 06 11/04/80 01 20 5 0 ° 5 3 ' N 1 2 7 ° 3 6 ' W 07 11/04/80 0230 5 1 ° 0 0 ' N 1 2 7 ° 5 1 * W 08 11/04/80 0330 5 1 ° 0 5 ' N 1 2 8 ° 0 7 ' W 09 11/04/80 0430 5 1 ° 0 9 ' N 1 2 8 ° 1 9 ' W 10 11/04/80 0530 5 1 ° 1 3 ' N 1 2 8 ° 3 4 ' W 1 1 11/04/80 1 1 30 5 1 ° 3 9 ' N 1 3 0 ° 0 3 ' W 1 2 11/04/80 1 300 5 1 ° 4 5 ' N 1 3 0 ° 2 2 ' W 13 11/04/80 1400 5 1 ° 4 6 ' N 1 3 0 ° 2 5 ' W 1 4 11/04/80 2200 5 2 ° 4 4 ' N 1 3 2 ° 1 5 ' W 15 11/04/80 2300 5 2 ° 5 2 ' N 1 3 2 ° 2 5 ' W 16 12/04/80 1 700 5 3 ° 4 5 ' N 1 3 3 ° 1 2 ' W 17 12/04/80 1915 5 4 ° 0 8 ' N 1 3 3 ° 1 1 ' W 18 12/04/80 2200 5 4 ° 1 3 ' N 1 3 2 ° 2 6 ' W 19 12/04/80 2300 5 4 ° 1 4 ' N 1 3 2 ° 0 9 ' W 20 13/04/80 01 00 5 4 ° 1 6 ' N 1 3 1 ° 3 0 ' W 21 13/04/80 21 00 5 3 ° 3 0 ' N 1 3 1 ° 4 0 ' W 22 13/04/80 2200 5 3 ° 3 6 ' N 1 3 1 ° 3 0 ' W 23 13/04/80 2300 5 3 ° 4 4 ' N 1 3 1 ° 1 8 ' W 24 14/04/80 0000 5 3 ° 5 1 ' N 1 3 1 ° 0 2 ' W 25 14/04/80 01 00 5 3 ° 5 9 ' N 1 3 0 ° 4 7 ' W 26 14/04/80 1815 5 4 ° 3 1 ' N 1 3 0 ° 3 1 ' W 27 14/04/80 1900 5 4 ° 2 4 ' N 1 3 0 ° 3 4 ' W 28 14/04/80 2045 5 4 ° 0 6 ' N 1 3 0 ° 2 2 ' W 29 15/04/80 1 445 5 3 ° 0 7 ' N 1 2 8 ° 3 5 ' W 30 15/04/80 21 45 5 2 ° 2 0 ' N 1 2 8 ° 3 0 ' W 31 16/04/80 1 600 5 1 ° 5 2 ' N 1 2 7 ° 5 5 ' W 32 16/04/80 1 745 5 1 ° 2 2 ' N 1 2 7 ° 5 0 ' W 33 16/04/80 2045 5 1 ° 1 1 'N 1 2 7 ° 5 8 ' W 34 16/04/80 21 25 5 1 ° 0 5 ' N 1 2 8 ° 0 5 ' W 35 16/04/80 21 55 5 1 ° 0 0 ' N 1 2 8 ° 1 0 ' W 36 16/04/80 2235 5 0 ° 5 4 ' N 1 2 8 ° 1 7 ' W 37 16/04/80 2255 5 0 ° 5 1 ' N 1 2 8 ° 2 2 ' W 21 1 APPENDIX I (Continued) CRUISE 14 30 May - 7 June 1980 STATION DAY/MO/YR TIME POSITION 01 30/05/80 1 1 55 4 9 ° 3 0 ' N 1 2 3 ° 5 7 ' W 02 30/05/80 1 432 4 9 ° 4 7 ' N 1 2 4 ° 3 0 ' W 03 30/05/80 2031 5 0 ° 1 1 'N 1 2 4 ° 3 8 ' W 04 31/05/80 0920 5 0 ° 2 7 ' N 1 2 5 ° 1 6 ' W 05 31/05/80 0950 5 0 ° 2 7 ' N 1 2 5 ° 2 5 ' W 06 31/05/80 1 201 5 0 ° 2 8 ' N 1 2 6 ° 0 0 ' W 07 31/05/80 1 245 5 0 ° 2 9 ' N 1 2 6 ° 0 9 ' W 08 31/05/80 1416 5 0 ° 3 2 ' N 1 2 6 ° 4 1 ' W 09 31/05/80 1910 5 0 ° 4 0 ' N 1 2 7 ° 1 4 ' W 1 0 31/05/80 2354 5 0 ° 5 4 ' N 1 2 7 ° 3 7 ' W 1 1 01/06/80 0451 5 1 ° 3 9 ' N 1 2 7 ° 5 4 ' W 1 2 01/06/80 0546 5 1 ° 4 7 ' N 1 2 7 ° 5 5 ' W 1 3 01/06/80 1 1 20 5 2 ° 1 3 ' N 1 2 8 ° 0 9 ' W 1 4 01/06/80 1 305 5 2 ° 2 3 ' N 1 2 8 ° 3 0 ' W 1 5 01/06/80 1 932 5 3 ° 1 0 ' N 1 2 8 ° 3 8 ' W 16 01/06/80 21 39 5 3 ° 1 9 ' N 1 2 9 ° 0 8 ' W 1 7 02/06/80 0630 5 4 ° 0 7 ' N 1 3 0 ° 1 8 ' W 1 8 02/06/80 1 600 5 3 ° 5 9 ' N 1 3 0 ° 4 8 ' W 19 02/06/80 1800 5 3 ° 4 6 ' N 1 3 1 ° 1 5 ' W 20 02/06/80 2030 5 3 ° 2 9 ' N 1 3 1 ° 4 7 ' W 21 03/06/80 1 1 55 5 3 ° 2 8 ' N 1 3 1 ° 3 3 ' W 22 03/06/80 1 400 5 3 ° 3 3 ' N 1 3 1 ° 0 2 ' W 23 03/06/80 1935 5 3 ° 5 0 ' N 1 3 0 ° 1 9 ' W 24 04/06/80 0838 5 4 ° 3 7 ' N 1 3 0 ° 4 2 ' W 25 04/06/80 1 535 5 4 ° 2 0 ' N 1 3 0 ° 3 4 ' W 26 04/06/80 1 730 5 4 ° 1 0 ' N 1 3 0 ° 2 3 ' W 27 04/06/80 21 45 5 3 ° 3 5 ' N 1 2 9 ° 4 0 ' W 28 05/06/80 1 345 5 2 ° 1 7 ' N 1 2 8 ° 2 7 ' W 29 06/06/80 0101 5 1 ° 2 6 ' N 1 2 7 ° 4 9 ' W 30 06/06/80 0239 5 1 ° 0 7 ' N 1 2 8 ° 0 0 ' W 31 06/06/80 0515 5 0 ° 4 6 ' N 1 2 8 ° 2 6 ' W 32 06/06/80 2000 5 0 ° 4 0 ' N 1 2 8 ° 2 3 ' W 33 07/06/80 01 20 5 0 ° 5 1 ' N 1 2 7 ° 4 4 ' W 34 07/06/80 1 935 5 0 ° 2 2 ' N 1 2 7 ° 3 2 ' W 35 07/06/80 21 50 4 9 ° 5 8 ' N 1 2 5 ° 0 9 ' W APPENDIX II C a l c u l a t i o n of r e g i o n a l c r i t i c a l depths and mixed depths for B . C . c o a s t a l water s . Regions are d e f i n e d as the S t r a i t of G e o r g i a (Lat > 4 9 ° N ) , Queen C h a r l o t t e Sound ( 5 0 ° 1 0 ' N < Lat < 5 2 ° N ) , Hecate S t r a i t ( 5 2 ° N < Lat < 5 4 ° 1 0 ' N and Long < 1 3 2 ° W ) , and Dixon Entrance (Lat > 5 4 ° 1 0 ' N ) . Each page r e p r e s e n t s a s u c c e s s i v e s tep i n the c a l c u l a t i o n s ; r e s u l t s a re p r e s e n t e d i n F i g . 3 (Chapter 4 ) . These va lue s repre sent the normal d a i l y t o t a l r a d i a t i o n for each month, I 0 i n J c m " 2 d " 1 , r e c o r d e d for Sandsp i t (Dixon Entrance and Hecate S t r a i t ) , Cape S t . James (Queen C h a r l o t t e Sound) , and Nanaimo (the S t r a i t of G e o r g i a ) , and a v a i l a b l e i n the Monthly R a d i a t i o n Summary, Atmospher ic Environment S e r v i c e , Ottawa. The P r o p o r t i o n T r a n s m i t t e d through Sea Sur face i s from Parsons et al. (1966) and i s based on the sea sona l sun a n g l e . Normal D a i l y R a d i a t i o n Va lue s SANDSPIT CAPE ST. JAMES NANAIMO Propor t ion Transmi t t e d through Sea Sur face Jan Feb Mar Apr May Jun J u l Aug Sep Oct Nov Dec 242.4 491 .4 901 .6 1362.7 1822.4 1783.7 1723.6 1510.3 1362.5 589.5 411.7 181.1 264.5 519.3 904. 1 1398.4 1915.6 1974.7 1916.1 1667.0 1221 .8 665.3 325.5 379.3 291 .4 612.7 1 048.6 1649.8 2119.6 2226.8 2380.3 1965.7 1404. 4 775.3 316.0 234. 1 .80 .87 .92 .95 .96 .96 .96 .95 .93 .90 .85 .78 212 213 APPENDIX II (Continued) C r i t i c a l Depths C r i t i c a l depths were c a l c u l a t e d u s ing the equa t ion from Parsons et al. (1984): _ 0.5 I 0 c r " k I c w i t h I 0 the normal d a i l y r a d i a t i o n by month fo r each a r e a , Ic the compensat ion l i g h t i n t e n s i t y (58 J c m " 2 d " 1 from Hobson 1981), and k the a t t e n u a t i o n c o e f f i c i e n t as c a l c u l a t e d from S e c c h i depths measured in the r e g i o n (see S e c t i o n I V . B . 2 . ) . A c r i t i c a l depth was c a l c u l a t e d for each a v a i l a b l e measurement of k, then the means ( 2 c r ) and s t andard d e v i a t i o n s (s) were determined fo r each month and area (depths in m e t e r s ) . Dixon E n t r a n c e Hecate S t r a i t Queen G e o r g i a S t r a i t C h a r l o t t e Sound n 2c r s n 2c r s n 2c r s n 2c r s Jan 1 1 15.2 3. 9 4 17.8 2.5 5 22.0 5.6 3 14.9 2. 1 Feb 3 27.6 9. 7 4 52. 1 15.4 8 35.2 7.4 1 2 27.2 7.7 Mar 23 69.3 12. 3 5 67.0 8.5 17 74.3 13.2 18 52.3 21 .6 Apr 5 68.8 33. 1 5 92.9 13.2 1 2 67.7 25.7 20 66.0 17.8 May 16 91 .8 56. 0 18 96.5 46.2 1 7 99.9 34.3 18 47.3 19. 1 Jun 12 65.5 25. 0 13 80.6 29.2 1 2 82.2 26.5 21 74.7 42. 1 J u l 17 56.3 27. 7 21 82.0 27.9 26 84. 1 25.5 18 74.8 24.4 Aug 17 46.8 14. 7 7 59. 1 20.4 1 1 65.6 25.7 1 7 62.8 14.8 Sep - - 2 54.4 0.0 9 71 .4 30.3 Oct 8 28.3 7. 0 6 34.8 10.5 1 1 35.1 14.7 1 7 37.4 10.3 Nov 9 24.5 8. 1 2 31 .8 2.4 6 20.5 0.9 1 4 15.4 3.3 Dec 8 9.8 2. 7 4 7.9 4. 1 4 19 . 3 2.2 4 10.2 5.5 214 APPENDIX II (Continued) C r i t i c a l Depth 95% Conf idence I n t e r v a l s Conf idence i n t e r v a l s of c r i t i c a l depths fo r B . C . coas t r e g i o n s were p l a c e d on monthly mean c r i t i c a l depths u s i n g the e q u a t i o n from Sokal and Rohl f (1981): 95% Conf idence I n t e r v a l = 2 ± t A c / , \ -r^— ' c r 0 . 5 , (n-1 ) vn The f o l l o w i n g t a b l e p r e s e n t s the monthly ranges i n meter s . Dixon Hecate S t r a i t Queen Georg i a Ent rance C h a r l o t t e S t r a i t Sound Jan 12.6 - 17.8 13.8 - 2 1 . 8 15.0 - 29.0 9.7 - 20. 1 Feb 3.5 - 51.7 27.6 - 76.6 29.0 - 4 i .4 22.3 - 32. 1 Mar 64.0 - 74.6 56.4 - 77.6 67.5 - 81.1 41 .6 - 63.0 Apr 27.7 - 82.2 76.5 -109.3 5 1 . 5 - 83 .9 57.7 - 74.3 May 62. 1 -121.6 73.5 -119.5 84.0 - 119.2 37.8 - 56.8 Jun 49.8 - 81.2 63.0 - 98.9 65.5 - 98.9 55.6 - 93.8 J u l 42. 1 - 70.5 69.3 - 94.7 73.8 - 94.4 62.7 - 86.9 Aug 39.3 - 54.3 40.2 - 78.0 48.3 - 82.9 55.2 - 70.4 Sep - - 54 .4 48. 1 - 94.7 Oct 22.6 - 34.2 23.8 - 45.8 25.3 - 45.0 32. 1 - 42.7 Nov 18.3 - 30.7 10.2 - 53.4 19.6 - 21.4 13.5 - 17.3 Dec 7.5 - 12.1 1 .4 - 14.4 15.8 - 22.8 1 .8 - 19.0 215 APPENDIX II (Continued) Mixed Depth Summary S t a t i s t i c s Summary s t a t i s t i c s f o r s u r f a c e mixed depths c a l c u l a t e d as d e s c r i b e d i n S e c t i o n IV.B.2. using data c o l l e c t e d d u r i n g the 1950's and 1960's f o r the northern s h e l f ( c r u i s e numbers l i s t e d in Appendix I I I ) , and during 1968 i n the S t r a i t of Georgia (Crean and Ages 1971). The 95% confidence i n t e r v a l s on mean mixed depths (2mix) were c a l c u l a t e d as (Sokal and Rohlf 1981): 95% Confidence I n t e r v a l = 2 . ± t f t c , 4\ -A- ' mix 0.5,(n-1) /n with n the number of s t a t i o n s f o r that region and month, and s the standard d e v i a t i o n . A l l depths are in meters. DIXON ENTRANCE n 2m ix s 95% C. I . (m) Jan 24 79.6 61 . 5 53.5 - 1 05.7 Feb 27 104.7 60.6 80.6 - 128.8 Mar 43 102.8 75.7 79.6 - 1 26.0 Apr 38 56.9 70.7 33.6 - 80.2 May 1 9 23.0 31.2 8.1 - 37.9 Jun 45 17.4 20.9 1 1 . 2 - 23.6 J u l 25 17.4 25.8 6.7 - 28. 1 Aug 36 34.8 55.5 16.2 - 53.4 Sep 1 07 24.8 27.8 19.5 - 30.0 Oct 1 1 1 42.8 28.5 37.5 - 48. 1 Nov 23 36.6 43.7 17.7 - 55.5 Dec 22 67.0 52.4 43.7 - 90.3 216 APPENDIX II (Cont inued) HECATE STRAIT n Mm ix s 95% C. I . (m) Jan 8 96. 5 40.5 62.7 - 1 30. 3 Feb 26 114.6 54.9 92.4 - 1 36.8 Mar 23 116.7 47.2 96.4 - 137.0 Apr 61 50.5 45.8 38.7 - 62.3 May 32 33.6 35.2 20.9 - 46.3 Jun 64 15.9 21 . 1 10.7 - 21.1 J u l 27 23.9 25.2 14.0 - 33.8 Aug 26 15.5 16.8 8.7 - 22.3 Sep 28 25.9 16.9 19.3 - 32.5 Oct 51 50.9 25.0 43.9 - 57.9 Nov 6 64.8 59.0 2.8 - 1 26.8 Dec 1 7 61.6 67.9 26.6 - 96.6 217 APPENDIX II (Cont inued) QUEEN CHARLOTTE SOUND n 2m i x s 95% C . I . (m) Jan 19 74.2 40. 5 54.7 - 93.7 Feb 47 76.3 42.3 63.8 - 88.8 Mar 60 93.3 50.0 80.5 - 106.1 Apr 75 67.9 41.7 58.3 - 77.5 May 20 33.3 42.8 13.2 - 53.4 Jun 42 15.6 16.9 10.4 - 20.8 J u l 43 21.8 28.0 13.1 - 30.5 Aug 24 17.4 32.3 3.7 - 31.1 Sep 25 28.6 22.3 19.3 - 37.9 Oct 96 44.3 25.8 39. 1 - 49.5 Nov 1 1 72.5 52.6 37. 1 - 107.9 Dec 23 72.2 49.2 5 1 . 0 - 93.4 STRAIT OF GEORGIA n Mm i x s 95% C . I . (m) Jan 43 38.8 24.6 3 1 . 2 - 46.4 Feb 43 13.1 16.4 8.1 - 18.1 Mar 43 9.0 5.8 7.2 - 10.8 Apr 46 15.4 9.9 12.5 - 18.3 May 46 7.2 4. 1 6.0 - 8.4 Jun J u l 92 7.4 ' 4.5 6.5 - 8.3 Aug 47 9.9 6.5 8.0 - 11.8 Sep Oct 45 12.1 7.2 9 .9 - 14.3 Nov 46 12.1 8.4 9.6 - 14.6 Dec 86 34.2 32.7 27.2 - 41 .2 APPENDIX III O r i g i n a l c r u i s e i d e n t i f i c a t i o n s and t h e i r c o r r e s p o n d i n g Mar ine E n v i r o n m e n t a l Data S e r v i c e (MEDS) c r u i s e numbers for B . C . n o r t h e r n s h e l f c r u i s e s whose data were used to e s t imate mixed l a y e r depths and bulk su r f ace s t r a t i f i c a t i o n v a l u e s . A r c h i v e d data are a v a i l a b l e from the Mar ine E n v i r o n m e n t a l Data S e r v i c e , Dept . of F i s h e r i e s and Oceans, 240 Sparks S t . , Ottawa, Ont . MEDS ORIGINAL ID CRUISE NUMBER H-54-1 180254688 H-54-2 180254689 H-54-3 180254690 H-54-4 180254691 H-55-1 180255694 H-55-2 180255695 H-55-3 180255699 C-57-4 180257716 CS-58-1 180258730 CS-59-1 180259733 CS-59-2 180259735 CS-59-3 180259740 SW-60-1 180260754 SW-61-1 180261759 MR-61-2 180261769 MR-61-3 180261774 MR-61-4 180261775 MR-62-1 180262778 MR-62-2 180262781 MR-62-3 180262790 : - 5 October 1967 180267008 • 27 A p r i l 1968 180268006 ; - 16 October 1968 180268008 16 October 1969 180269021 • 15 March 1970 180270012 • • 21 March 1971 180271015 218 APPENDIX IV Complete taxonomic i d e n t i f i c a t i o n s for those s p e c i e s d i s c u s s e d i n the t ex t are as f o l l o w s : PHYTOPLANKTON C e n t r i c Diatoms Bad er i as t r um delicatula C leve 1897 Ceratulina bergonii P e r a g a l l o 1892 Corethron hystrix Hensen 1886 Di t yl um brightwellii Grunow 1885 Lauderi a boreal is Gran 1900 Leptocyli ndrus dani cus C l e v e 1894 Skeletonema costatum C leve 1878 St ephanopyxi s palmeriana Grunow 1884 Pennate Diatoms Asterionella japonica C leve 1878 Thai assi onema nit zs chi odes Grunow 1885 F l a g e l l a t e s Ceratium lineatum C leve 1899 Distephanus speculum Haecke l 1899 219 220 ZOOPLANKTON Copepoda Acartia cf. clausii G i e s b r e c h t 1889 Acartia longiremis L i l l j e b o r g 1853 Calanus pacificus s . l . Brodsky 1948 Centropages abdomi nali s Sato 1913 Eucal anus bungi i G i e s b r e c h t 1892 Met ri dia pacifica Brodsky 1950 Neocalanus cristatus Kroyer 1848 Neocalanus plumchrus Marukawa 1921 Paracalanus parvus C l a u s 1863 Ps eudocal anus cf. mi nut us Kroyer 1845 Tort anus discaudatus Thompson and Scot t 1897 Chaetognatha Eukrohnia hamal a Mobius 1875 Sagilta elegans V e r r i l l 1873 F I S H Anopl opoma fimbria P a l l a s 1811 Gadus macrocephal us T i l e s i u s 1810 Hi ppogl ossus stenolepis Schmidt 1904 Onchorhynchus gor bus cha Walbaum 1792 PUBLICATIONS Perry, R.I. and B.R. Dilke. Seasonal mechanisms of phytoplankton s p a t i a l organization i n Hecate S t r a i t , B.C. , and the importance of t i d a l mixing. Submitted to: M.J. Bowman, W.T. Peterson and C.S. Yentsch (eds.). T i d a l Mixing and Plankton Dynamics. Springer-Verlag. N.Y. Parsons, T.R., H.M. Dovey, W.P. Cochlan, R.I. Perry and P.B. Crean. In Press. Fr o n t a l zone analysis at the mouth of a f j o r d - J e r v i s I n l e t , B r i t i s h Columbia. Sa r s i a . Perry, R.I., B.R. Dilke and T.R. Parsons. 1983. T i d a l mixing and summer plankt d i s t r i b u t i o n s i n Hecate S t r a i t , B r i t i s h Columbia. Can. J . F i s h . Aquat. S c i . 40: 871-887. Parsons, T.R. , R.I. Perry, E.D. Nutbrown, W. Hseih and CM. L a l l i . 1983. Fro n t a l zone analysis at the mouth of Saanich I n l e t , B r i t i s h Columbia. Mar. B i o l . 73: 1-5. Parsons, T.R., J. Stronach, G.A. Borstad, G. L o u t t i t and R.I. Perry. 1981. B i o l o g i c a l fronts i n the S t r a i t of Georgia, B r i t i s h Columbia, and t h e i r r e l a t i o n s to recent measurements of primary p r o d u c t i v i t y . Mar. E c o l . Prog. Ser. 6: 237-242. Aranuvachapun, S. and R.I. Perry. 1981. Spectral v a r i a t i o n s of coastal water irradiance as a measure of phytoplankton pigments. Int. J . Remote Sensing 2: 299-312. PUBLICATIONS 1. Flavonol Glycosides o f Hyginea abysinica. G.K. P i l l a i and Mulatu D'jote, J . Health S c i . , 11:140 (1976). 2. Some Practical Aspects o f Test Construction. G.K. P i l l a i , Indian J . Pharm. Eduo, 10:9 (1976). 3. Distribution o f Isoniazide Inactivation Status in Ethiopian Tuberculo-sis Patients. G.K. P i l l a i , R.K. Raina and G. Fereke, IRCS Med. J . , 6:318 (1978). 4. Outpatient Medication Prescribing Pattersn in a Tropical Teaching Hos-p i t a l . R.K. Raina and G.K. P i l l a i , Ind. J . Med. Assoc., 74:62 (1980). 5. Some aspects o f Drug Use in Ethiopia. C. Chandrasekhar, R.K. Raina and G.K. P i l l a i , Tropical Doctor, 11:116 (1981). 6. Resolution o f Equine Estrogens Using Glass Capillary Columns. G.K. P i l l a i and K.M. McEralne, J . High Resol. Chromatogr. Comm., 4:70 (1981). 7. Quantitative Determination of Conjugated Estrogens in Formulations by Capillary Gas Chromatography. G.K. P i l l a i and K.M. McErlane, J . Pharm. S c i . , 70:1072 (1981). 8. Quantitative Analysis of Conjugated Estrogens in a Vaginal Cream Formulation by Capillary Gas Chromatography. G.K. P i l l a i and K.M. McErlane, J . Pharm. S c i . , 71:583 (1982). 9. Analysis of Indomethacin and its Impurities in Formulations by High Performance Liquid jChromatography. E. Kwong, G.K. P i l l a i and K.M. McErlane, J . Pharm. S c i . , 71:828 (1982). 10. Electron Capture GLC Determination of Tocainide in Biological Fluids Using Fused S i l i ca Capillary Columns. G.K. P i l l a i , J .E . Axelson and K.M. McErlane, J . Chromatogr., 229:103 (1982). 11. Gas Liquid Chromatographic Resolution and Assay of Tocainide Enantio-mers Using Chiral Capillary Column and Study o f Their Selective Dispos-ition in Man. K.M. McErlane and G.K. P i l l a i , J. Chromatogr., 274:129 (1983). 12. Stereospecific Salivary Excretion of Tocainide Enantiomers in Man. G.K. P i l l a i , J .E . Axelson and K.M. McErlane, Res. Commun. Chemical Pathol, and Pharmacol., 43:209 (1984). 13. Pharmacokinetics o f tocainide enantiomers in healthy volunteers and in patients with renal dysfunction. G.K. P i l l a i , J . E . Axelson and K.M. McErlane. Manuscript in preparation. 

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