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Enriching effects of Salmon farms in British Columbian coastal waters and the influence of flushing and… Korman, Joshua 1989

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ENRICHING EFFECTS OF SALMON FARMS IN BRITISH COLUMBIAN COASTAL WATERS AND THE INFLUENCE OF FLUSHING AND SEASONALITY. By Joshua Korman B. S c , McGill University, 1984 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES (Department of Oceanography) We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA May 1989 © Joshua Korman, 1989 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of O 65tHNj^vcy-i The University of British Columbia Vancouver, Canada Date ^ o c ^ t V J S , Y^fr DE-6 (2/88) ABSTRACT Water samples at two salmon farms of d i a m e t r i c a l l y opposed f l u s h i n g c h a r a c t e r i s t i c s i n the D i s c o v e r y Passage area were c o l l e c t e d d u r i n g the summer of 1988 a t i n c r e a s i n g d i s t a n c e s downstream from the c u l t u r e o p e r a t i o n s . The main o b j e c t i v e s were t o determine i f salmon farms i n t h i s r e g i o n are l e a d i n g t o e l e v a t e d c o n c e n t r a t i o n s of t o t a l ammonia and d i s s o l v e d o r g a n i c carbon i n the v i c i n i t i e s o f the farms, r e s u l t i n g i n h i g h e r c o n c e n t r a t i o n s of phytoplankton and b a c t e r i a . E l e v a t e d s u r f a c e t o t a l ammonia l e v e l s were observed i n the immediate areas of the s i t e s ( i . e . < 10 m) at both l o c a t i o n s , although the frequency of occurrence and the magnitude of the enrichment were g r e a t e r a t the area e x p e r i e n c i n g a weaker f l u s h i n g regime. 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 w i t h i n the pens a l s o appeared s l i g h t l y h i g h e r compared t o downstream l e v e l s d u r i n g p a r t s of the summer. The c u l t u r e o p e r a t i o n s d i d not appear t o have any e f f e c t on d i s s o l v e d o r g a n i c carbon and b a c t e r i a l c o n c e n t r a t i o n s i n the s u r r o u n d i n g waters. i i i The a b i l i t y t o d e t e c t e l e v a t e d l e v e l s of ammonium i n the v i c i n i t y of f i s h farms was shown t o be i n f l u e n c e d by ambient l e v e l s of n u t r i e n t s and phytoplankton biomass. The r a p i d r e d u c t i o n of ammonium c o n c e n t r a t i o n s w i t h i n 25 m downstream of the c u l t u r e f a c i l i t i e s suggests t h a t d e c l i n e s i n water q u a l i t y r e s u l t i n g from f i s h farming a c t i v i t y i n t h i s a r e a seems u n l i k e l y . The f i n d i n g s of t h i s study should be viewed as p r e l i m i n a r y i n nature g i v e n the l i m i t e d s i z e of the sampling program employed. i v TABLE OF CONTENTS ABSTRACT i i TABLE OF CONTENTS i v LIST OF TABLES v LIST OF FIGURES v i ACKNOWLEDGEMENTS v i i I. INTRODUCTION 1 A. N u t r i e n t Loading 3 B. Changes i n Phytoplankton Biomass, P r o d u c t i o n and . . . . Spec i e s Composition 10 C. Organic Carbon 14 D. B a c t e r i a and A n t i b i o t i c s 16 E. Water C i r c u l a t i o n 21 II. OBJECTIVES 24 III. MATERIALS AND METHODS 25 A. Sampling L o c a t i o n s 25 B. P h y s i c a l Measurements ..29 C. T o t a l Ammonia and N i t r a t e 31 D. C h l o r o p h y l l a 32 E . Primary P r o d u c t i o n 33 F. Phytoplankton S p e c i e s Composition 34 G. D i s s o l v e d Organic Carbon 35 H. B a c t e r i a 35 I. Data A n a l y s i s 36 IV. RESULTS 39 A. P h y s i c a l S t u d i e s 39 B. T o t a l Ammonia and N i t r a t e 44 C. Phytoplankton Standing Stock 53 D. Primary P r o d u c t i v i t y 54 E . Phytoplankton Species Composition 60 F . D i s s o l v e d Organic Carbon Absorbance 63 V. DISCUSSION 7 3 VI. REFERENCES 85 VII. APPENDICES 89 Appendix I 89 Appendix II 92 V L I S T OF TABLES T a b l e 1. Summary of sampling frequency and cor r e s p o n d i n g t i d a l p o s i t i o n 29 Table 2. Sample s i z e s used i n s t a t i s t i c a l t e s t s t o determine d i f f e r e n c e s between s t a t i o n s . . . . 37 Ta b l e 3. Summary of p h y s i c a l d a t a f o r Yellow I s l a n d , summer, 1988 41 Table 4. Summary of p h y s i c a l data f o r Quartz Bay, summer, 1988 42 Table 5. Summary of water q u a l i t y data f o r Yellow I s l a n d , summer, 1988 45 Table 6. Summary of water q u a l i t y data f o r Quartz Bay, summer, 1988 46 Table 7. Summary of r e s u l t s of K r u s k a l - W a l l i s One-way A n a l y s i s of V a r i a n c e 56 Table 8. Summary of r e s u l t s of Mann-Whitney U-Test. . . . 57 Ta b l e 9. Spearman nonparametric c o r r e l a t i o n m a t r i x of the Yellow I s l a n d water q u a l i t y d a t a 70 Ta b l e 10. Spearman nonparametric c o r r e l a t i o n m a t r i x f o r the Quartz Bay water q u a l i t y d a t a 71 Table 11. Summary of changes i n p h y s i c a l and b i o l o g i c a l water q u a l i t y parameters a t Yellow I s l a n d and Quartz Bay 72 Table 12. Organisms observed at Yellow I s l a n d and Quartz Bay 93 v i L I S T OF F I G U R E S F i g u r e 1. L o c a t i o n s of Yellow I s l a n d A q u a c u l t u r e and Quartz Bay Sea Farms i n the D i s c o v e r y Passage area 26 F i g u r e 2. D e t a i l of s i t e l o c a t i o n s f o r Yellow I s l a n d Aquaculture and Quartz Bay Sea Farms. 27 F i g u r e 3. Sigma-t p r o f i l e s at Yellow I s l a n d and Quartz Bay 40 F i g u r e 4. T o t a l ammonia 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 a t Yellow I s l a n d , l a t e June, 1988 47 F i g u r e 5. T o t a l ammonia 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 a t Yellow I s l a n d , mid-August, 1988 48 F i g u r e 6. T o t a l ammonia 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 a t Yellow I s l a n d , l a t e September, 1988 50 F i g u r e 7. T o t a l ammonia 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 a t Quartz Bay, summer, 1988 51 F i g u r e 8. 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 a t Yellow I s l a n d and Quartz Bay, l a t e June/ e a r l y J u l y , 1988 52 F i g u r e 9. Hourly and d a i l y p h o t o s y n t h e t i c r a t e s a t Yellow I s l a n d and Quartz Bay, summer, 1988. . 58 F i g u r e 10. P r o d u c t i v i t y i n d i c e s a t Yellow I s l a n d and Quartz Bay, summer, 1988 59 F i g u r e 11. Phytoplankton s p e c i e s composition a t Ye l l o w I s l a n d and Quartz Bay, summer, 1988 62 F i g u r e 12. DOC absorbance (280 nm) and b a c t e r i a l numbers at Yellow I s l a n d , l a t e June, 1988. .. 64 F i g u r e 13. DOC absorbance (280 nm) and b a c t e r i a l numbers a t Yellow I s l a n d , mid-August, 1988. . 65 F i g u r e 14. DOC absorbance (280 nm) and b a c t e r i a l numbers a t Yellow I s l a n d , l a t e September, 1988 67 F i g u r e 15. DOC absorbance (280 nm) and b a c t e r i a l numbers at Quartz Bay, summer, 1988 68 F i g u r e 16. The e f f e c t s of f r e e z i n g on ammonium det e r m i n a t i o n s 91 v i i ACKNOWLEDGEMENTS I would l i k e t o thank my s u p e r v i s o r Dr. Timothy R. Parsons f o r h i s a d v i c e and support throughout t h i s p r o j e c t . I a l s o wish t o thank the oth e r members of my r e s e a r c h committee, Dr. F.J.R. "Max" T a y l o r and Dr. C o l i n D. L e v i n g s . I wish t o acknowledge W.C. Cochlan f o r the a n a l y s i s of n u t r i e n t samples and e s p e c i a l l y f o r the many u s e f u l c o n v e r s a t i o n s c o n c e r n i n g phytoplankton ecology and n i t r o g e n l i m i t a t i o n . I thank Rowan Haigh f o r perfor m i n g the phytoplankton s p e c i e s i d e n t i f i c a t i o n . In the f i e l d , Dan Heath was ver y h e l p f u l i n overcoming some of the l o g i s t i c a l problems encountered. S p e c i a l thanks t o D r s . Anne and John Heath of Yellow I s l a n d A q u a c u l t u r e and Barb and Derek Sharp of Quartz Bay Sea Farms f o r p e r m i t t i n g me t o sample at t h e i r salmon farms. Support f o r t h i s p r o j e c t and myself was p r o v i d e d by an o p e r a t i n g grant from the M i n i s t r y of A g r i c u l t u r e and F i s h e r i e s through Ed B l a c k and an NSERC postgraduate f e l l o w s h i p . 1 I . I N T R O D U C T I O N Salmon farming i n B.C. i s growing a t an almost e x p l o s i v e r a t e . In 1985 t h e r e were e i g h t o p e r a t i n g farms pr o d u c i n g 107 tonnes of Chinook and Coho salmon. By 1988, the number of o p e r a t i n g s i t e s had i n c r e a s e d over 15 f o l d t o 125, w h i l e annual p r o d u c t i o n grew t o 6500 tonnes. P r o j e c t i o n s f o r 1990 i n d i c a t e a f u r t h e r i n c r e a s e i n the number of s i t e s t o over 150, w i t h p r o d u c t i o n d o u b l i n g t o 14000 tonnes per year (Fred C a r p e n t e r , Department of F i s h e r i e s and Oceans, p e r s . comm.). The D i s c o v e r y Passage are a l o c a t e d at the northern end of the S t r a i t of Georgia i s a r e g i o n which e x e m p l i f i e s t h i s tremendous growth of the salmon farming i n d u s t r y on the B.C. c o a s t . P r e s e n t l y , 60 farms are i n o p e r a t i o n i n t h i s a r e a , w i t h 175 l i c e n s e s f o r f u t u r e s i t e s c u r r e n t l y a w a i t i n g a p p r o v a l (Rosenthal et al., 1988). Salmon farming unavoidably impacts t o some degree on i t s immediate environment and the p u b l i c g e n e r a l l y views the i n c r e a s i n g number of o p e r a t i n g farms as a p o t e n t i a l t h r e a t t o marine water q u a l i t y . Indeed, evidence f o r m a r i c u l t u r e - i n d u c e d water q u a l i t y problems e x i s t i n n a t i o n s such as Norway and Japan. E l e v a t e d l e v e l s of ammonium and decreases i n d i s s o l v e d oxygen c o n c e n t r a t i o n s i n waters surrounding c u l t u r e f a c i l i t i e s have been noted i n these c o u n t r i e s a l o n g w i t h the growth of t h e i r a q u a c u l t u r e i n d u s t r i e s ( A r i z o n o , 1978; E r v i k et al., 1985; Kadowaki and 2 H i r a t a , 1984.). The impact of salmon farms on marine waters i s a l s o of g r e a t importance t o the farmers themselves, as both s t r e s s l e v e l s and d i s e a s e i n c i d e n c e s of c u l t u r e d f i s h are enhanced by hi g h l e v e l s of u n i o n i z e d ammonia and low d i s s o l v e d oxygen c o n c e n t r a t i o n s . The presence of salmon net-pens i n marine waters can a f f e c t the surrounding p h y s i c a l , chemical and b i o l o g i c a l marine environment i n a v a r i e t y o f ways. The p o t e n t i a l environmental e f f e c t s of salmon farms have been reviewed by Weston (1986), and i n c l u d e : 1) Changes i n water c i r c u l a t i o n ; 2) Sedimentation and accumulation of faec e s and excess fee d beneath the c u l t u r e o p e r a t i o n ; 3) Changes i n water chemistry; 4) A l t e r a t i o n of phytoplankton biomass and p r o d u c t i v i t y ; 5) E f f e c t s on abundance and s p e c i e s c o m p o s i t i o n of b e n t h i c macrofauna; 6) P r o l i f e r a t i o n of b a c t e r i a pathogenic t o humans and the e f f e c t of a n t i b i o t i c s on the surrounding b i o t a ; 7) Changes i n s p e c i e s composition and abundance of f i s h and megafauna; 8) Disease t r a n s m i s s i o n from c u l t u r e d t o w i l d s t o c k s ; 9) I n t r o d u c t i o n of e x o t i c s p e c i e s and subsequent changes i n the g e n e t i c f i t n e s s of w i l d s t o c k s . The o v e r a l l g o a l of t h i s study was t o determine i f the by-products a s s o c i a t e d w i t h salmon farms i n the D i s c o v e r y Passage r e g i o n are c a u s i n g changes i n the l e v e l s o f primary and b a c t e r i a l p r o d u c t i o n i n the immediate v i c i n i t y of the farms. The f o l l o w i n g i n t r o d u c t i o n w i l l t h e r e f o r e o n ly review the p o r t i o n s of the l i t e r a t u r e which are p e r t i n e n t t o the i n f l u e n c e of salmon farms on marine p r o d u c t i v i t y . I n f o r m a t i o n r e g a r d i n g the e f f e c t s o f f i s h c u l t u r e f a c i l i t i e s 3 on water c i r c u l a t i o n , nutrient l e v e l s , phytoplankton productivity and b a c t e r i a l numbers w i l l be presented. For a broader review of the environmental impacts of mariculture, the reader should r e f e r to Rosenthal et al. (1988) and Weston (1986). A . N u t r i e n t L o a d i n g There are 3 p r i n c i p a l sources of nutrient loading relat e d to salmon culture operations. The primary source i s associated with the dispersion of the soluble end-products of salmonid protein metabolism which include t o t a l ammonia ( N H 3 and NH4+), urea and phosphate. Ammonium forms the bulk of excretory nitrogen, although proportions of ammonium and urea can be variable (Gowen and Bradbury, 1987). Secondary nitrogenous end-products of salmonid metabolism such as n i t r a t e and n i t r i t e are produced through mi c r o b i a l l y mediated oxidation of ammonia and urea (Liao and Mayo, 1974). Although a small amount of phosphate i s excreted i n soluble form, the majority of phosphate waste i s bound i n the faeces and deposited on the sediments (Ennell and Lof, 1983). Excretory products released from the fo u l i n g organisms bound to the r a f t s and net-pens of a culture operation constitute an important source of nutrient loading rela t e d to f i s h c u l t u r e . The excretory products of mussels and other f o u l i n g organisms consist of t o t a l ammonia, amino-nitrogen, urea, and phosphate (Weston, 1986). The 4 substantial contribution of these invertebrates to nitrogen loading associated with f i s h farms was f i r s t documented by the presence of elevated t o t a l ammonia l e v e l s ( N H 3 and NH^ "*") at i n a c t i v e farm s i t e s i n Sechelt I n l e t (Black and Carswell, 1986). The amount of loading from fo u l i n g organisms located on the supporting structures and nets of mariculture f a c i l i t i e s i s a function of the densities and growth rates of the organisms. The t h i r d and least noteworthy source of nutrient loading from salmon farms r e s u l t s from the decomposition of excess feed and faeces deposited beneath the pens and the subsequent release of nutrients -to the water column. Ammonium and phosphate are the p r i n c i p a l breakdown products of feed and faeces and are found i n high concentrations i n the sediments and pore waters beneath mariculture f a c i l i t i e s (Hall and Holby, 1986). The quantity of nutrients entering the water column from the sediment wastes i s a complex function dependent on the area of waste d i s p e r s a l , the reducing p o t e n t i a l of the sediment and the fl u x rate at the sediment-water i n t e r f a c e . The high s e t t l i n g v e l o c i t i e s of uneaten food and faeces (0.06 to 0.15 m*s~^) preclude any substantial nutrient loss associated with microbial a c t i v i t y during s e t t l i n g (Gowen and Bradbury, 1987). 5 D i s s o l v e d i n o r g a n i c n i t r o g e n has long been h e l d as the most important g r o w t h - l i m i t i n g n u t r i e n t f o r phytoplankton i n c o a s t a l marine waters (Dugdale, 1967) and i n c r e a s e s i n i t s c o n c e n t r a t i o n surrounding m a r i c u l t u r e f a c i l i t i e s c o u l d enhance phytoplankton and b a c t e r i a l growth r a t e s . Because phosphorus and s i l i c a i n c o a s t a l environments are r a r e l y found i n g r o w t h - l i m i t i n g c o n c e n t r a t i o n s , these n u t r i e n t s can be c o n s i d e r e d i n c o n s e q u e n t i a l waste products of aq u a c u l t u r e f a c i l i t i e s i n most marine waters (Gowen and Bradbury, 1987). The remainder of t h i s s e c t i o n on n u t r i e n t l o a d i n g w i l l t h e r e f o r e focus on the magnitude of n i t r o g e n l o a d i n g from marine salmon farms t o the surrounding c o a s t a l w a t e r s . There have been a few r e p o r t e d cases o f i n c r e a s e d ammonium l e v e l s i n the v i c i n i t y of marine salmon farms. Ammonium c o n c e n t r a t i o n s surrounding net-pens i n Norway were found t o be 8-9 times h i g h e r than ambient l e v e l s ( E r v i k et al., 1985). C o n s i s t e n t l y h i g h e r l e v e l s of ammonium i n the v i c i n i t y of an experimental m a r i c u l t u r e f a c i l i t y i n Hendersen I n l e t , Washington were noted d u r i n g a p e r i o d of l i m i t e d m i x i n g . Increased ammonium l e v e l s near the m a r i c u l t u r e f a c i l i t y were observed at the s u r f a c e but not at the near-bottom sampling depth i n d i c a t i n g a n e g l i g i b l e f l u x of regenerated ammonium from the sediment t o the water column. D e s t r a t i f i c a t i o n of the water column a f t e r September and the r e s u l t i n g mixing prevented ammonium accumulation and d e p r e s s i o n s i n d i s s o l v e d oxygen l e v e l s near the salmon pens d u r i n g f a l l , w i n t e r and s p r i n g 6 (Pease, 1977). C o n c e n t r a t i o n s of t o t a l ammonia as hig h as 4 uM have been recorded a t the s u r f a c e w i t h i n salmon pens at S e c h e l t I n l e t , B.C., with maximal c o n c e n t r a t i o n s of 10 uM o c c u r r i n g a t 6 m depth. Highest c o n c e n t r a t i o n s of t o t a l ammonia a t 6 m were observed at mid-afternoon w h i l e s u r f a c e maxima o c c u r r e d d u r i n g the e a r l y morning (S. Gormican, U n i v e r s i t y of B r i t i s h Columbia, p e r s . comm.). T h i s d i f f e r e n c e i n the d a i l y p a t t e r n s of t o t a l ammonia c o n c e n t r a t i o n s a t the s u r f a c e and a t 6 m suggests t h a t ammonia l e v e l s a r e , i n p a r t , i n f l u e n c e d by the n u t r i t i o n a l requirements of the surrounding p h y t o p l a n k t o n . Subsurface (3 m) l e v e l s of t o t a l ammonia w i t h i n salmon pens l o c a t e d i n a d i f f e r e n t area of S e c h e l t I n l e t ranged from 0.2 t o 0.9 uM hi g h e r than v a l u e s recorded a t a d i s t a n c e 27 m downcurrent from the e n c l o s u r e s (Black and C a r s w e l l , 1986). A l a c k of any i n c r e a s e i n ammonium l e v e l s taken j u s t above the bottom d i r e c t l y beneath the farms compared t o ambient bottom water l e v e l s suggests v e r y low r a t e s of ammonium l o a d i n g a s s o c i a t e d w i t h decomposing waste fee d and faeces i n the sediment. Es t i m a t e s of the amount of n i t r o g e n l o a d i n g from salmon farms have been made by Gowen and Bradbury (1987). T h e i r c a l c u l a t i o n s are based on the assumption t h a t 68 t o 86% of the consumed n i t r o g e n i s v o i d e d from the f i s h as s o l u b l e ammonium and u r e a . Knowing the p r o t e i n content of the f e e d , the d i g e s t i b i l i t y of p r o t e i n and the r e t e n t i o n of n i t r o g e n by the f i s h , the authors have est i m a t e d t h a t 32 kg of 7 soluble ammonium are produced per tonne of food fed. A medium sized salmon farm (ca. biomass of 50 tonnes) feeding at a rate of 1% biomass/day would l i b e r a t e 16 kg of soluble ammonium per day. Liao and Mayo (1974) have empirically derived ammonium production rates for pond-reared trout and estimated that these production rates follow the equation: N A = 0.0289*F, where N A i s the ammonium production rate at temperatures of 50-58 F, i n pounds of NH4-N per 100 l b f i s h per day and F i s the feeding rate i n pounds of food per 100 l b f i s h per day. This empirical estimation (28.9 kg of ammonium per tonne of food fed) i s quite s i m i l a r to that derived t h e o r e t i c a l l y by Gowen and Bradbury (1987). Both estimates demonstrate that f i s h farms can provide substantial d a i l y inputs of ammonium to the marine environment. A considerable amount of nitrogen from the feed ends up i n the sediment beneath the net-pens through the accumulation of waste feed and faeces. Approximately 20% of the feed used i n marine salmon culture ends up on the bottom u n u t i l i z e d . Roughly 26% of the food eaten i s excreted as faeces, 4% of which i s comprised of nitrogen. Adding these numbers up, close to 30% of the nitrogen i n the feed w i l l end up on the bottom i n p a r t i c u l a t e form (Gowen and Bradbury, 1987). A salmon farm with 50 tonnes of f i s h i n the water uses roughly 500 kg of feed per day containing 40 kg of nitrogen. Thus, 12 kg of nitrogen per day are 8 d e p o s i t e d i n the sediment below a l a r g e farm. C o n s i d e r i n g t h i s p a r t i c u l a t e n i t r o g e n i s not d i l u t e d t o anywhere near the same extent as i t s s o l u b l e c o u n t e r p a r t s , t h i s r e p r e s e n t s a p o t e n t i a l l y s i g n i f i c a n t source of n i t r o g e n t o the water column i f the sediment-water exchange r a t e i s h i g h . E l e v a t e d n i t r o g e n l e v e l s i n the sediments beneath salmon farms have been recorded a t a number of d i f f e r e n t l o c a t i o n s . The t o t a l n i t r o g e n content of sediments beneath a m a r i c u l t u r e f a c i l i t y i n Henderson I n l e t , Washington was approximately twice t h a t of the r e f e r e n c e area (Pease, 1977). Increased l e v e l s of ammonia n i t r o g e n i n i n t e r s t i t i a l and near-bottom water beneath salmon pens have a l s o been noted i n the S t r a i t of Juan de Fuca (Weston, 1986) and i n Sweden ( H a l l and Holby, 1986). The Swedish study r e v e a l e d t h a t ammonium c o n c e n t r a t i o n s i n the f i r s t 5 cm of the pore water were over 1000 times g r e a t e r than l e v e l s i n pore water a t the r e f e r e n c e s t a t i o n s . In situ n i t r i f i c a t i o n and d e n i t r i f i c a t i o n of the t o t a l ammonia i n the pore water and sediment c o u l d p o t e n t i a l l y a c t as a s i n k f o r the d e p o s i t e d p a r t i c u l a t e n i t r o g e n . I t has been c l e a r l y shown, however, t h a t the o x i d a t i o n of ammonia t o n i t r i t e and n i t r a t e and the subsequent r e d u c t i o n of these compounds t o n i t r o g e n gas i s v i r t u a l l y n o n e x i s t e n t i n the anaerobic sediments commonly found below f i s h farms (Kaspar et al., 1988). I t i s not s u r p r i s i n g t h a t l e v e l s of 9 nitrogen and ammonia i n the sediments and pore waters beneath salmon farms have been found to be many times higher than background l e v e l s . The quantity of nitrogen entering the water column from the enriched sediments below mariculture f a c i l i t i e s can be determined through in situ d i r e c t measurements of solute fluxes across the sediment-water i n t e r f a c e . H a l l and Holby (1986) found ammonium fluxes i n the sediments beneath salmon farms (0.0018 to 0.0198 g NH4-N*m"2"day"1) to be 10-100 times higher than ammonium fluxes i n ambient sediments. The enhancement of ammonium solute fluxes below f i s h farms r e s u l t s from the combination of increased l e v e l s of nitrogen i n the sediments and lower rates of d e n i t r i f i c a t i o n found i n anaerobic sediments commonly seen beneath the culture operations (Ennell and Lof, 1983). A t h e o r e t i c a l estimation of ammonium loading from the sediments beneath salmon farms to the water column can be made knowing the ammonium solute f l u x and the area of enriched sediment. The area of sea bed over which waste feed and faeces w i l l be dispersed i s a function defined by the following r e l a t i o n s h i p ; D = d'V/v, where D represents horizontal distance dispersed, d i s water depth, V i s current speed and v i s s e t t l i n g v e l o c i t y of the waste (Gowen and Bradbury, 1987). Thus a 50 tonne farm with 10 pens located 10 m above the bottom, using dry p e l l e t s s e t t l i n g at roughly 0.09 m*s~*, with p r e v a i l i n g currents of 0.1 m*s x and havxng an area of 3000 m* w i l l disperse wastes over 5500 m . Using t h i s affected area beneath a mariculture f a c i l i t y , the ammonium fluxes reported by Ha l l and Holby (1986) would d e l i v e r approximately 110 g NH^-N*day~^ from the sediments to the water column. The amount of ammonium entering the water column from the sediments i s almost 150 f o l d smaller than the 16 kg of soluble ammonium excreted d a i l y by 50 tonnes of cultured f i s h . The most s i g n i f i c a n t input of nutrients from marine salmon farms r e s u l t s through the excretion of ammonium by the cultured f i s h . Although the size of the f i s h farm regulates the amount of ammonium entering the environment, the flushing capacity of the loc a t i o n w i l l ultimately determine the rate of ammonium d i l u t i o n and i t s . f i n a l concentrations i n the surrounding water. B . Changes i n P h y t o p l a n k t o n Biomass , P r o d u c t i o n and S p e c i e s C o m p o s i t i o n . Because inshore primary production i s , f o r the most part, based on nitrogen i n reduced forms such as ammonium and urea (Paasche, 1988), i t i s not unreasonable to assume that nitrogen loading from salmon farms could lead to increases i n phytoplankton biomass and productivity. Furthermore, increased concentrations of nitrogen surrounding the farms could r e s u l t i n species composition 11 s h i f t s through s e l e c t i o n f o r a l g a l groups w i t h h i g h e r ammonium uptake r a t e s and/or l a r g e r c e l l volumes b e t t e r adapted f o r s u r v i v i n g i n waters of h i g h e r t r o p h i c s t a t e ( H a r r i s , 1988). There are a number of documented cases of freshwater f i s h farm e f f l u e n t s c a u s i n g changes i n ambient phytoplankton p r o d u c t i v i t y . The e f f e c t s of two l a r g e f i s h farms on primary p r o d u c t i o n i n a moderately s i z e d (190 kirr) o l i g o t r o p h i c l a k e i n F i n l a n d were i n v e s t i g a t e d by E l o r a n t a and Palomaki (1986). The authors d i s c o v e r e d t h a t areas 2 km downstream from the farms had c h l o r o p h y l l a and primary p r o d u c t i o n v a l u e s two f o l d h i g h e r than s t a t i o n s l o c a t e d immediately upstream of the farms. A 50-100% i n c r e a s e i n the number of phytoplankton s p e c i e s found i n the more e u t r o p h i c waters i n the area of the f i s h farms was a l s o observed and a t t r i b u t e d t o the i n c r e a s e d n u t r i e n t l o a d from the farms. Higher l e v e l s of phytoplankton biomass and i n c r e a s e d dominance of blue-green a l g a l s p e c i e s were observed i n the v i c i n i t y of a l a r g e t r o u t c u l t u r e o p e r a t i o n i n a s m a l l (48 ha) P o l i s h e u t r o p h i c l a k e , and a g a i n , a t t r i b u t e d t o n u t r i e n t l o a d i n g from the f i s h farm. Because the f l u s h i n g c a p a c i t y and c i r c u l a t i o n of these l a k e s i s c o n s i d e r a b l y l e s s than t h a t of most m a r i c u l t u r e l o c a t i o n s , i t i s d i f f i c u l t t o i n t e r p r e t t h i s i n f o r m a t i o n i n r e l a t i o n t o the enhancement of p r o d u c t i v i t y around marine f i s h farms. 12 There i s very l i t t l e evidence t o suggest t h a t m a r i c u l t u r e o p e r a t i o n s can cause changes i n phytoplankton p r o d u c t i v i t y i n areas w i t h even moderate f l u s h i n g c a p a c i t i e s . Increased c o n c e n t r a t i o n s of ammonium i n waters surrounding salmon farms i n Henderson (Pease, 1977) and S e c h e l t (Black and C a r s w e l l , 1986) I n l e t s were not accompanied by h i g h e r l e v e l s of c h l o r o p h y l l a . A few documented cases of m a r i c u l t u r e - i n d u c e d enhancement of primary p r o d u c t i v i t y do, however, e x i s t . Arakawa (1973) c o r r e l a t e d the h i g h e r frequency of phytoplankton blooms i n Hiroshima Bay w i t h i n c r e a s e d l e v e l s of o y s t e r p r o d u c t i o n . Increases i n the biomass and c h l o r o p h y l l a content of the green a l g a , Cladophora glomerata were observed i n areas immediately adjacent t o f i s h farms l o c a t e d i n the B a l t i c Sea ( R u o k o l a h t i , 1988). I t should be noted, however, t h a t because both the Sea of Japan and the B a l t i c Sea have r e l a t i v e l y weaker f l u s h i n g regimes and lower ambient n i t r o g e n l e v e l s compared t o the c o a s t a l areas and i n l e t s of B r i t i s h Columbia, the e f f e c t s of n u t r i e n t l o a d i n g on primary p r o d u c t i o n w i l l be a m p l i f i e d i n the former a r e a s . In l a b o r a t o r y experiments, Nishimura (1982) demonstrated t h a t e x t r a c t s from the faeces of c u l t u r e d y e l l o w t a i l tuna and mackerel meat used f o r f e e d caused s i g n i f i c a n t i n c r e a s e s i n the growth r a t e of the r e d - t i d e forming d i n o f l a g e l l a t e , Gymnodinium nagasakiense. In experiments designed t o s i m u l a t e c o n d i t i o n s of seawater f l o w i n g over f i s h food and salmon f a e c e s , 13 Parsons et al. (1989) found c e l l numbers of the h e t e r o t r o p h i c d i n o f l a g e l l a t e , Oxyrrhis marina t o i n c r e a s e by a f a c t o r of 10 i n the t r e a t e d tanks compared t o c o n t r o l s . No d i f f e r e n c e s i n diatom biomass or t o t a l primary p r o d u c t i o n were noted between t r e a t e d and c o n t r o l t a n k s . The experimental approaches of Nishimura (1982) and Parsons et al. (1989) both e s t a b l i s h the p o s s i b i l i t y of phytoplankton s p e c i e s composition s h i f t s i n communities immediately above the d e p o s i t e d f e e d and f a e c e s of a salmon farm. The e f f e c t s of the s o l u b l e waste products of c u l t u r e d f i s h on marine phytoplankton under c o n t r o l l e d e x perimental c o n d i t i o n has y e t t o be examined. In summary, t h e r e i s a l i m i t e d amount of evidence t o suggest t h a t n u t r i e n t l o a d i n g from the farms r e s u l t s i n enhancement of primary p r o d u c t i v i t y and changes i n community s t r u c t u r e . The magnitude of any p o t e n t i a l changes w i l l be a f u n c t i o n of the n u t r i t i o n a l s t a t e of the phytoplankton community, the ambient n u t r i e n t and l i g h t l e v e l s , n a t u r a l p a t t e r n s of a l g a l s u c c e s s i o n , and most i m p o r t a n t l y , the f l u s h i n g c a p a c i t y of the l o c a t i o n . 14 C. Organic Carbon Marine f i s h farms have a great p o t e n t i a l t o i n c r e a s e the l e v e l s of p a r t i c u l a t e and d i s s o l v e d o r g a n i c carbon i n the surrounding water. The p o s s i b l e sources of carbon i n p u t from a c u l t u r e o p e r a t i o n t o the water column i n c l u d e : 1) B a c t e r i a l decomposition of feed and fae c e s below the net pens r e s u l t i n g i n the r e l e a s e of o r g a n i c carbon from the sediment t o the water column; 2) L e a c h i n g of carbon from feed and fae c e s as i t s i n k s t o the bottom; 3) Exudate r e l e a s e from phytoplankton and b e n t h i c algae a s s o c i a t e d w i t h the f o u l i n g of nets and f l o a t s ; 4) B a c t e r i a l decomposition of f o u l i n g organisms. One of the most obvious e f f e c t s of salmon farms on the marine environment i s the accumulation of o r g a n i c matter beneath the c u l t u r e o p e r a t i o n . T o t a l carbon c o n c e n t r a t i o n s were found t o be t w o - f o l d h i g h e r i n sediments below salmon pens i n Henderson I n l e t (Pease, 1977), and a number of examples of t o t a l o r g a n i c carbon enrichment have been reviewed by Weston (1986). While i n c r e a s e s i n the o r g a n i c f r a c t i o n of t o t a l carbon beneath salmon pens i n S e c h e l t I n l e t were noted, no changes i n the percentage of v o l a t i l e o r g a n i c carbon i n the same sediments were observed (Black and C a r s w e l l , 1986). The l a t t e r measurement can be used as an i n d i c a t i o n of the amount of o r g a n i c m a t e r i a l which remains t o be leached from the sediments t o the water column. B l a c k and C a r s w e l l ' s (1986) i n v e s t i g a t i o n demonstrated t h a t i n c r e a s e s i n the o r g a n i c c o n t e n t of the sediment below f i s h farms do not n e c e s s a r i l y l e a d t o i n c r e a s e s i n the f l u x of carbon from the sediment t o the 15 water column. In f a c t , although the presence of o r g a n i c a l l y e n r i c h e d sediments below c u l t u r e o p e r a t i o n s i s w e l l documented and seems a l i k e l y source of o r g a n i c carbon t o the o v e r l y i n g water, t h e r e i s no evidence t o suggest an i n c r e a s e d e f f l u x of d i s s o l v e d o r g a n i c carbon from such d e p o s i t s . The l e a c h i n g of carbon from s i n k i n g waste fe e d and faeces would seem a sm a l l i f not n e g l i g i b l e source of o r g a n i c carbon t o the surrounding water. The r e l e a s e of t r a c e q u a n t i t i e s of growth promoting substances such as v i t a m i n from the fee d c o u l d , however, have important e f f e c t s on b a c t e r i a l and a l g a l growth. The n e g l i g i b l e l o s s of carbon from f e e d through s o l u t i o n and m i c r o b i a l a c t i v i t y has been documented by Gowen and Bradbury (1987). Seawater tanks e n r i c h e d w i t h salmon feed and f a e c e s , however, were shown t o c o n t a i n s i g n i f i c a n t l y h i g h e r l e v e l s of DOC (T.R. Pars o n s , p e r s . comm.). The r e l e a s e of e x t r a c e l l u l a r d i s s o l v e d o r g a n i c carbon from a c t i v e l y p h o t o s y n t h e s i z i n g phytoplankton i s supported by a l a r g e body of l i t e r a t u r e ( S t o r c h and Saunders, 1978). In the event t h a t i n c r e a s e d r a t e s o f primary p r o d u c t i o n e x i s t i n the immediate v i c i n i t y of c u l t u r e o p e r a t i o n s , one would expect t o see hi g h e r r e s u l t i n g l e v e l s of DOC. The l a r g e amounts of b e n t h i c a l g a e r e s i d i n g on the nets and r a f t s of the f i s h farms would a l s o be expected t o p r o v i d e an a d d i t i o n a l source of DOC t o the surrounding water. 16 Decomposition of b e n t h i c algae and o t h e r f o u l i n g organisms c o u l d p r o v i d e a f i n a l source of DOC and p a r t i c u l a t e c a r b o n . Evidence t o support the r o l e of e x t r a c e l l u l a r r e l e a s e of DOC and the decomposition of f o u l i n g organisms as important sources of o r g a n i c carbon from f i s h farms i s l a c k i n g . D. Bacteria and Antibiotics There i s a g e n e r a l t r e n d of i n c r e a s i n g b a c t e r i a l numbers and biomass w i t h i n c r e a s i n g l e v e l s of o r g a n i c matter and primary p r o d u c t i v i t y (Azam et al., 1983). There have been many examples of e l e v a t e d b a c t e r i o p l a n k t o n c o n c e n t r a t i o n s i n the v i c i n i t y of sources of o r g a n i c carbon (Parsons et al., 1988) and n u t r i e n t s (Larsson and Hagstrom, 1982). Thus, the i n p u t of o r g a n i c matter and n u t r i e n t s a s s o c i a t e d w i t h m a r i c u l t u r e c o u l d r e a s o n a b l y be expected t o l e a d t o an i n c r e a s e d number of b a c t e r i a produced i n the v i c i n i t y o f the c u l t u r e s i t e s (Rosenthal et al., 1988). The v a s t m a j o r i t y of s t u d i e s r e g a r d i n g the i n f l u e n c e of f i s h c u l t u r e on b a c t e r i a l biomass have measured the e f f e c t s of c u l t u r e a c t i v i t i e s on c o l i f o r m and s p e c i f i c a l l y , f e c a l c o l i f o r m b a c t e r i a . The l i t e r a t u r e t h a t documents i n c r e a s e d l e v e l s of c o l i f o r m and/or f e c a l c o l i f o r m b a c t e r i a i n the e f f l u e n t s of freshwater f i s h h a t c h e r i e s and t r o u t c u l t u r e o p e r a t i o n s i s accompanied by an equal number of cases where no e f f e c t s of the c u l t u r e o p e r a t i o n s are observed (Bergheim and Selmer-Olsen, 1978; Rosenthal et a l . , 1988). In the marine environment, c o l i f o r m l e v e l s i n the v i c i n i t y of 17 salmon c u l t u r e o p e r a t i o n s at S e c h e l t I n l e t were found t o be e l e v a t e d compared t o background c o n c e n t r a t i o n s . The f a c t t h a t the enrichment was observed o n l y at the n e a r - s u r f a c e sampling depth (3 m) suggests t h a t the source of c o n t a m i n a t i o n was not a s s o c i a t e d w i t h the unconsumed fee d on the bottom (Black and C a r s w e l l , 1986). In terms of b a c t e r i o p l a n k t o n p r o d u c t i v i t y , a c t u a l counts of b a c t e r i a l numbers or t o t a l c o l o n y - f o r m i n g u n i t s should g i v e a more r e p r e s e n t a t i v e account of the b a c t e r i a l consequences of o r g a n i c enrichment a s s o c i a t e d w i t h f i s h farms. A u s t i n (1985) has conducted a number of surveys on freshwater f i s h c u l t u r e o p e r a t i o n s and concluded t h a t t h e r e was l i t t l e e f f e c t of c u l t u r e on b a c t e r i a l numbers and c o m p o s i t i o n . I n v e s t i g a t i o n of the e f f l u e n t s of a c o a s t a l t u r b o t - r e a r i n g f a c i l i t y , however, r e v e a l e d an i n c r e a s e i n b a c t e r i a l numbers ran g i n g from 3 t o 5 0 - f o l d . The l a r g e i n c r e a s e s i n b a c t e r i a l biomass a s s o c i a t e d w i t h the e f f l u e n t of t h i s marine c u l t u r e o p e r a t i o n were a t t r i b u t e d t o poor and u n h y g i e n i c husbandry p r a c t i c e s which r e s u l t e d i n i n c r e a s e d l e v e l s of o r g a n i c m a t e r i a l and n u t r i e n t s . Furthermore, d i r e c t comparisons co n c e r n i n g b a c t e r i a l enrichment between net-pen c u l t u r e and land-based r e a r i n g o p e r a t i o n s are s u s p e c t , as h i g h e r s t o c k i n g d e n s i t i e s and lower d i l u t i o n c a p a b i l i t i e s a s s o c i a t e d w i t h the l a t t e r form, w i l l a m p l i f y the o p e r a t i o n s i n f l u e n c e on b a c t e r i a l p r o d u c t i o n . 18 Experimental evidence suggests t h a t s o l i d f i s h farm waste can i n c r e a s e c o n c e n t r a t i o n s of b a c t e r i o p l a n k t o n i n the water d i r e c t l y above the sediment. A d d i t i o n of salmonid feed and faeces t o seawater tanks r e s u l t e d i n i n c r e a s e s of b a c t e r i a l numbers and h e t e r o t r o p h i c uptake r a t e s (Parsons et a l . , 1989). Reduced l e v e l s of m i c r o f l a g e l l a t e s i n the t r e a t e d tanks and the subsequent r e d u c t i o n i n g r a z i n g p r e s s u r e on the b a c t e r i o p l a n k t o n were i m p l i c a t e d as the causes of the e l e v a t e d c o n c e n t r a t i o n s i n the l a t t e r group. C u l t u r e o p e r a t i o n s c o u l d a l s o produce a poor environment f o r b a c t e r i a l p r o d u c t i o n i n the surrounding waters through the employment of a n t i b i o t i c s and chemotherapeutics used i n the treatment of f i s h d i s e a s e . The amount of a n t i b i o t i c r e l e a s e d t o the environment w i l l be a f u n c t i o n of the frequency and d u r a t i o n of tr e a t m e n t , the amount of a n t i b i o t i c l e a c h i n g from the f e e d , and f i n a l l y , the p e r s i s t e n c e of the a n t i b i o t i c i n the sediment. O x y t e t r a c y c l i n e (OTC) i s the most commonly used a n t i b i o t i c and i s a d m i n i s t e r e d as a feed a d d i t i v e approximately 2-3 times over the summer months f o r the treatment of v i b r i o s i s and a host of other common f i s h d i s e a s e s ( A u s t i n , 1985; Weston, 1986). The i n c i d e n c e of d i s e a s e , and hence, the frequency of a n t i b i o t i c usage, i s dependent on p r e v a i l i n g water q u a l i t y c o n d i t i o n s and husbandry p r a c t i c e s . Under poor c o n d i t i o n s , the p o s s i b i l i t y of an almost c o n t i n u a l a d m i n i s t r a t i o n of medicated feed d u r i n g the warm months does e x i s t . 19 The amount of OTC l e a c h i n g from medicated fe e d has been found t o be a p o s i t i v e f u n c t i o n of water temperature, hydrogen i o n c o n c e n t r a t i o n and surface/volume r a t i o of the p e l l e t s . Under c o n d i t i o n s l i k e l y t o be encountered i n pond-r e a r i n g s i t u a t i o n s , up t o 20% of the OTC i n medicated feed i s l o s t t o the surrounding water w i t h i n 15 minutes ( F r i b o u r g h et al., 1969). Drug l e a c h i n g i n marine s i t u a t i o n s would be expected t o be s l i g h t l y l e s s than 20% due t o lower water temperatures and h i g h e r pH v a l u e s . Marine b a c t e r i a r e s p o n s i b l e f o r sulphur and ammonium o x i d a t i o n are u n a f f e c t e d by c o n c e n t r a t i o n s of OTC of up t o 10 m g * l ~ l , however, a complete l o s s of a c t i v i t y o ccurs at c o n c e n t r a t i o n s of 100 mg'l-^ (Weston, 1986). Assuming an OTC l e a c h i n g v a l u e of 20%, a c u l t u r e o p e r a t i o n w i t h 50 tonnes of d i s e a s e d f i s h , u s i n g 50-75 mg OTC'kg-^ body weight"day"^, would i n c r e a s e the OTC c o n c e n t r a t i o n i n the immediate v i c i n i t y of the farm by 0.06 m g * l- 1 "day-* i f no water c i r c u l a t i o n e x i s t e d around the farm. Given the l a r g e volumes of water t h a t d i l u t e marine f i s h farm e f f l u e n t s , i t would seem very u n l i k e l y t h a t the development of i n h i b i t o r y OTC c o n c e n t r a t i o n s i n the water column c o u l d occur through l e a c h i n g a l o n e . 20 The remainder of the OTC t h a t does not l e a c h from the waste fee d w i l l , of c o u r s e , end up on the sediment below the net-pens. OTC has been found t o be a r e l a t i v e l y p e r s i s t e n t drug i n anoxic sediments commonly found below f i s h farms. The h a l f - l i f e of t h i s agent has been determined through l a b o r a t o r y i n v e s t i g a t i o n s t o be approximately 10 weeks. The c o n c e n t r a t i o n of OTC measured i n the sediments below a number of marine f i s h farms i n Norway ranged from 0.1-4.9 mg*kg~* dry ma t t e r . A n t i m i c r o b i a l e f f e c t s w i t h i n the sediments were estimated t o occur f o r a p e r i o d o f up t o 12 weeks a f t e r a d m i n i s t r a t i o n (Jacobsen and B e r g l i n d , 1988). The e x t e n t t o which h i g h l e v e l s of OTC and o t h e r a n t i b i o t i c s i n the sediments c o n t r i b u t e t o water column c o n c e n t r a t i o n s has y e t t o be determined. D i r e c t evidence f o r the i n h i b i t i o n of b a c t e r i a l p r o d u c t i o n through the r e l e a s e of a n t i b i o t i c s from freshwater f i s h farms has been accumulated by A u s t i n (1985). During p e r i o d s of chemotherapy, b a c t e r i a l numbers i n the e f f l u e n t s were shown t o be c o n s i d e r a b l y l e s s than w i t h i n i n f l o w w a t e r s . Dramatic i n c r e a s e s i n b a c t e r i a l c o n c e n t r a t i o n s of the e f f l u e n t waters were observed w i t h i n a few days of the c o n c l u s i o n of chemotherapy. Reductions i n b a c t e r i a l numbers found i n the e f f l u e n t s of f i s h farms undergoing d i s e a s e treatments may a l s o , i n p a r t , be a f u n c t i o n of lower c o n c e n t r a t i o n s of o r g a n i c matter r e l a t e d t o reduced f e e d i n g regimes. 21 The increased l e v e l s of organic carbon and a n t i b i o t i c s associated with marine f i s h farms w i l l have antagonistic e f f e c t s on ambient b a c t e r i a l l e v e l s . Coupled with the fact that bacteria compete with phytoplankton f o r growth-limiting nutrients such as ammonium (Harris, 1988), pr e d i c t i o n of the influence of salmon farms on b a c t e r i a l numbers becomes very complex. Direct measurements of b a c t e r i a l concentrations i n the v i c i n i t y of culture operations would therefore seem the most r e a l i s t i c and l o g i c a l way of determining the consequences of f i s h culture on marine b a c t e r i a l production. E . W a t e r C i r c u l a t i o n A recurrent theme throughout t h i s discussion concerns the degree to which f i s h farm by-products are d i l u t e d by the surrounding water. The current regime at any s i t e i s c r i t i c a l i n minimizing sedimentation and promoting the removal of by-products from the culture operation. A discussion of the extent to which the net-pens and r a f t structures of f i s h farms reduce current v e l o c i t y i n the culture structure and the surrounding area i s therefore merited. The a l t e r a t i o n of current flow induced by a net-pen i s dependent on such variables as mesh s i z e , extent of fouling, stocking density, and the size and movement of f i s h within the pen. Studies on the e f f e c t s of net-pens on current v e l o c i t i e s by Inoue (1972) revealed that v e l o c i t i e s within the pens were reduced to 35-81% of upstream values. Further 22 reductions i n v e l o c i t y occur for a series of nets aligned p a r a l l e l to the current. A f t e r passage through 3 consecutive empty net-pens, current speeds ranging from 10-25% of the o r i g i n a l upstream values can be expected. Because many B.C. salmon farms a l i g n up to 12 net-pens i n a d i r e c t i o n p a r a l l e l to the p r e v a i l i n g currents, great reductions i n flow at the downstream net-pens would be very l i k e l y . F l u i d dynamics p r i n c i p l e s have been used to estimate the e f f e c t s of mariculture operations on water flow i n the surrounding area (Weston, 1986). The distances to which a structure w i l l e f f e c t the f l u i d flow surrounding i t can be measured i n diameters (dimension of a structure perpendicular to the d i r e c t i o n of flow). For a porous structure such as a net-pen, current v e l o c i t i e s should return to 95% of the o r i g i n a l upstream v e l o c i t i e s within one and two diameters from the structure at the upstream and sidestream areas, respectively. Downstream current v e l o c i t i e s w i l l be affected ( i . e . < 95% of o r i g i n a l current speed) fo r a distance of 20 diameters from the net-pens. Thus, two net-pens aligned perpendicular to the p r e v a i l i n g currents would a f f e c t downstream current v e l o c i t i e s for at le a s t 500 m. These values should be regarded as very rough approximations as the complex c i r c u l a t i o n patterns t y p i c a l of coastal and estuarine environments confound attempts to estimate the influence of mariculture f a c i l i t i e s on surrounding water c i r c u l a t i o n . 23 T h e f a t e a n d i n f l u e n c e o f s a l m o n f a r m b y - p r o d u c t s s u c h a s a m m o n i u m a n d o r g a n i c c a r b o n o n t h e m a r i n e e n v i r o n m e n t i s d e p e n d e n t o n a n u m b e r o f b i o l o g i c a l a n d p h y s i c a l p r o c e s s e s . T h e a n t a g o n i s t i c n a t u r e o f m a n y o f t h e s e p r o c e s s e s w a r r a n t s a c i r c u m s p e c t a t t i t u d e w i t h r e s p e c t t o t h e o r e t i c a l e s t i m a t i o n s o f t h e e f f e c t s o f m a r i c u l t u r e o p e r a t i o n s o n m a r i n e w a t e r s . D i r e c t m e a s u r e m e n t s o f t h e c o n c e n t r a t i o n s o f s a l m o n f a r m b y - p r o d u c t s a n d t h e i r e f f e c t s o n s u r r o u n d i n g m a r i n e p r o d u c t i v i t y i n t h e i m m e d i a t e a r e a o f c u l t u r e o p e r a t i o n s a r e j u s t i f i e d . 24 I I . OBJECTIVES The primary o b j e c t i v e of t h i s study was t o determine i f salmon farms i n the D i s c o v e r y Passage r e g i o n are producing e l e v a t e d c o n c e n t r a t i o n s of t o t a l ammonia and d i s s o l v e d o r g a n i c carbon i n the immediate areas of the farms r e s u l t i n g i n h i g h e r c o n c e n t r a t i o n s of b a c t e r i a and p h y t o p l a n k t o n . By sampling a t i n c r e a s i n g d i s t a n c e from the farms, an estimate of the area of water showing any e n r i c h e d c h a r a c t e r i s t i c s c o u l d be r e a l i z e d . To e v a l u a t e the i n f l u e n c e of water c i r c u l a t i o n on the p o s s i b l e e n r i c h i n g e f f e c t s of the c u l t u r e o p e r a t i o n s , two s i t e s of d i a m e t r i c f l u s h i n g c h a r a c t e r i s t i c s were sampled. One would expect t o see s t r o n g e r evidence f o r e u t r o p h i c a t i o n o r enrichment and a g r e a t e r a f f e c t e d area a t the s i t e w i t h poorer water exhange. F i n a l l y , by sampling over a p e r i o d of 3 months d u r i n g the summer and e a r l y f a l l , the seasonal v a r i a b i l i t y i n any e u t r o p h i c e f f e c t s produced by the farms c o u l d be e s t i m a t e d . Temperature, water column s t r a t i f i c a t i o n and n u t r i e n t a v a i l a b i l i t y are important determinants f o r marine p r o d u c t i o n and seasonal changes i n these parameters w i l l g r e a t l y i n f l u e n c e any e n r i c h i n g e f f e c t s of the c u l t u r e o p e r a t i o n s . Changes i n water q u a l i t y and enhanced l e v e l s of p r o d u c t i o n would most l i k e l y occur d u r i n g p e r i o d s when the p h o t i c zone i s s t r o n g l y s t r a t i f i e d and d e p l e t e d of n i t r o g e n . 25 III . MATERIALS AND METHODS A. Sampling Locations The two farm s i t e s chosen f o r t h i s study are l o c a t e d on the i s l a n d s of Quadra and C o r t e s . T h i s area i s bound t o the north by Johnstone S t r a i t and t o the south by the S t r a i t of Georgia ( F i g . 1 ) . Yellow I s l a n d Aquaculture i s found on the western s i d e of Quadra I s l a n d adjacent t o Seymour Narrows ( F i g . 2A). T h i s passage i s renowned f o r i t s s t r o n g t i d a l f l o o d c u r r e n t s which can reach speeds of up t o 3 m*s~^ and r e s u l t i n i n t e n s e mixing (Thompson, 1981). Mean t i d a l ranges from the Seymour Narrows r e f e r e n c e s t a t i o n l i e between 1.13 and 3.02 m (Anon., 1988). The salmon farm i s l o c a t e d i n a sm a l l bay of maximum depth of 48 m wit h the net-pen e n c l o s u r e s approximately 15 m above the bottom at low t i d e . Yellow I s l a n d A q u a c u l t u r e produces 52 m e t r i c tonnes of Chinook, Coho and St e e l h e a d a n n u a l l y . Quartz Bay Sea Farms i s l o c a t e d on the n o r t h e r n end of Corte s I s l a n d i n a s m a l l , semi-enclosed bay bordered by S u t i l Channel ( F i g . 2B). Mean t i d a l ranges from the S u t i l Channel r e f e r e n c e s t a t i o n are between 1.22 and 3.44 m (Anon., 1988). Quartz Bay has a maximum depth of approximately 60 m with the c u l t u r e f a c i l i t y l o c a t e d at the southern end of the bay 25 m above the bottom a t low t i d e . 26 Figure 1. Locations of Yellow Island Aquaculture (Yellow Island) and Quartz Bay Sea Farms (Quartz Bay) i n the Discovery Passage area. 27 Figure 2 . Deta i l of s i te locations for Yellow Island Aquaculture (A) and Quartz Bay Sea Farms (B) showing direct ions of ebb and f lood currents . 28 Quartz Bay Sea Farms has an annual production of ca. 65 tonnes of Chinook and Coho. Seawater samples from both farms were taken just below the surface (0.5 m) with a p l a s t i c bucket within the net-pens and at 3, 10 and 25 m from the pens corresponding to stations 0, 1, 2 and 3, respectively. In order to maintain a constant distance between the stations and the culture f a c i l i t y during a l l sampling periods, a polypropylene l i n e was fi x e d from the r a f t s to the surrounding boom structure and marked at the appropriate distances. Samples were taken from the downcurrent side of the enclosures along the transect l i n e which was strung p a r a l l e l to the ebb current d i r e c t i o n . Concentrations of t o t a l ammonia (NH3 and NH 4 +), n i t r a t e and n i t r i t e (N0 3~ and NC>2~), chlorophyll a and bacteria were determined as well as primary productivity, phytoplankton species composition and dissolved organic carbon (DOC) absorbance at each s t a t i o n . The Yellow Island Aquaculture s i t e was sampled four days over the summer between l a t e June and September. In order to evaluate the influence of t i d a l displacement on the d i l u t i o n and concentrations of the various water q u a l i t y parameters examined, the Yellow Island s i t e was sampled two times per day as close to low and high tides as possible (Table 1). 29 The d i f f i c u l t y and expense of a c c e s s i n g Quartz Bay Sea Farms r e s t r i c t e d the sampling frequency t o t h r e e p e r i o d s over the summer between e a r l y J u l y and September. In order t o minimize the time from sample c o l l e c t i o n t o the i n i t i a l p r o c e s s i n g and f r e e z i n g which o c c u r r e d at Yellow I s l a n d , o n l y one d a i l y s et of samples was taken a t Quartz Bay. The time of sampling ranged from 10:00 t o 12:00 c o r r e s p o n d i n g t o low and midwater t i d a l h e i g h t s (Table 1 ) . T a b l e 1. Sampling frequency and c o r r e s p o n d i n g t i d a l p o s i t i o n . SAMPLING LOCATION SAMPLING DATE SAMPLING TIME TIDAL POSITION Yellow I s l a n d 30/06/88 11:00 16:00 Low T i d e High T i d e 06/08/88 10:00 14:30 Midwater High T i d e 07/08/88 10:00 14:30 Midwater High T i d e 21/09/88 9:00 13:00 Low T i d e High T i d e Quartz Bay 01/07/88 12:00 Low T i d e 08/08/88 11:00 Midwater 20/09/88 10:00 Midwater B. Physical Measurements T e m p e r a t u r e / s a l i n i t y (T/S) p r o f i l e s were taken at both s i t e s ( S t a t i o n 1) f o l l o w i n g the f i r s t sample c o l l e c t i o n w i t h an A U T O L A B ™ model 602 p o r t a b l e t e m p e r a t u r e / s a l i n i t y probe. The water column was sampled a t i n t e r v a l depths of 2 m. The 30 instrument was c a l i b r a t e d p r i o r t o the f i e l d season a c c o r d i n g t o the methods d e s c r i b e d i n the A U T O L A B ™ user handbook. The temperature and s a l i n i t y p r e c i s i o n s of the instrument correspond t o + 0.1 C and + 0.03 °/0 0« In order t o c o r r e c t f o r d r i f t of the T/S probe over the summer, the temperature of a s u r f a c e sample was determined w i t h a g l a s s thermometer and a s a l i n i t y sample was c o l l e c t e d f o r a n a l y s i s w i t h a l a b o r a t o r y s a l i n o m e t e r f o l l o w i n g each p r o f i l e . D i f f e r e n c e s between the s u r f a c e T/S v a l u e s determined with the probe and those measured manually o r i n the l a b o r a t o r y were used t o c a l c u l a t e c o r r e c t i o n f a c t o r s . The o r i g i n a l T/S v a l u e s were then a d j u s t e d through m u l t i p l i c a t i o n w i t h the co r r e s p o n d i n g c o r r e c t i o n f a c t o r s . Sigma-t v a l u e s were c a l c u l a t e d from the raw dat a a c c o r d i n g t o the I n t e r n a t i o n a l E q u a t i o n o f S t a t e o f Seawater, 1980 at one atmosphere p r e s s u r e (Pond and P i c k a r d , 1982). S u r f a c e c u r r e n t speeds and d i r e c t i o n s were determined u s i n g a 1 X 1.5 m window-blind drogue o f s i m i l a r c o n s t r u c t i o n t o those d e s c r i b e d by Buckley and Pond (1976). The drogue was deployed from the r a f t s s u r rounding the pens and was a t t a c h e d t o the marked t r a n s e c t l i n e w i t h a s h o r t l e a s h and b r a s s c l i p . C urrent speed was c a l c u l a t e d from the mean of two 25 m t r i a l s . S u r f a c e c u r r e n t speeds and d i r e c t i o n s were measured immediately p r i o r t o the c o l l e c t i o n of seawater samples. 31 Water c l a r i t y was estimated u s i n g a 30 cm white metal S e c c h i d i s c lowered i n the shade of the r a f t s as c l o s e t o mid-day as p o s s i b l e . E x t i n c t i o n c o e f f i c i e n t s were c a l c u l a t e d based on the e q u a t i o n , K' = 1.7/DS, where K' i s the e x t i n c t i o n c o e f f i c i e n t of the water and Ds i s the S e c c h i d i s c depth i n meters (Parsons et al., 1977). C. Total Ammonia and Nitrate Seawater samples f o r n u t r i e n t d e t e r m i n a t i o n s were c o l l e c t e d from the sampling bucket i n 500 ml Nalgene b o t t l e s . The samples were f i l t e r e d under a 0.5 atmospheric p r e s s u r e vacuum through 47 mm AA M i l l i p o r e membrane f i l t e r s . The f i l t r a t e was c o l l e c t e d i n 50 ml g l a s s t e s t tubes suspended i n the f i l t r a t i o n f l a s k s w i t h s t r i n g and a 30 ml subsample was then f r o z e n (-20 C ) . In o r d e r t o e s t i m a t e the amount of v a r i a b i l i t y induced i n the t o t a l ammonia samples due t o the e f f e c t s of f r e e z i n g , 30 ml of a 1.5 uM NH4Cl s o l u t i o n prepared i n 3% NaCl was f r o z e n a l o n g w i t h every s e t of n u t r i e n t samples. The maximum l e n g t h of time from c o l l e c t i o n t o f r e e z i n g over the course of the summer ranged from one t o t h r e e hours f o r Yellow I s l a n d and Quartz Bay, r e s p e c t i v e l y . A l l Nalgene b o t t l e s and glassware used i n the c o l l e c t i o n and f i l t r a t i o n o f n u t r i e n t samples were a c i d washed i n 10% HCl and r i n s e d t h r e e times i n d i s t i l l e d / d e i o n i z e d water. 32 N i t r a t e (NC<3~ and NO^-) and t o t a l ammonia (NH3 and NH^ "*") c o n c e n t r a t i o n s were determined f o l l o w i n g the procedures o f Wood et al. (1967) and Slawyk and Maclsaac (1972), r e s p e c t i v e l y . A l l n u t r i e n t s were measured u s i n g a Technicon A u t o a n a l y z e r ™ I I . The p r e c i s i o n of the n i t r a t e a n a l y s i s a t the 20 uM l e v e l has been determined by Parsons et al. (1984) as + 0.5 uM. The p r e c i s i o n of the t o t a l ammonia technique was determined e x p e r i m e n t a l l y by a n a l y z i n g the same 20 samples i n two d i f f e r e n t r u n s . P r e c i s i o n a t the 2 uM l e v e l was c a l c u l a t e d as + 0.02 uM. D. C h l o r o p h y l l a A l l seawater samples f o r c h l o r o p h y l l a d e t e r m i n a t i o n s were c o l l e c t e d i n 1 1 Nalgene b o t t l e s . Seawater volumes r a n g i n g from 0.75 t o 1 1 were f i l t e r e d through 47 mm AA M i l l i p o r e membrane f i l t e r s under a 0.5 atmospheric p r e s s u r e vacuum w i t h the a d d i t i o n o f 3-5 drops o f MgCC<3 s o l u t i o n . The samples r e t a i n e d on the f i l t e r paper were wrapped i n wax and aluminum paper, p l a c e d i n a dark p l a s t i c c o n t a i n e r w i t h D n e r i t ex w and f r o z e n a t -20 C. The experimental procedures and spe c t r o p h o t o m e t r i c equations used f o r the c h l o r o p h y l l a an a l y s e s are d e s c r i b e d by Parsons et al. (1984). A S p e c t r o n i c 2 1 ™ spectrophotometer w i t h 50 mm pa t h - l e n g t h c u v e t t e s was used t o determine the a b s o r p t i o n s at the s p e c i f i e d wavelengths. •s P r e c i s i o n a t the 5 mg/mJ l e v e l has been determined as + 0.21 •s mg/m-5 c h l o r o p h y l l a. 33 E. Primary Production Primary productivity was calculated by measuring the uptake of radioactive carbon with in situ incubations. Precision at the 30 mg C*m~J*hr A l e v e l f o r a 3 hr incubation using 5 uCi has been determined as + 3 mg Cm hr (Parsons et al., 1984). Seawater samples were c o l l e c t e d from the sampling bucket i n 500 ml Nalgene bottle s and divided into one opaque and two c l e a r 125 ml BOD bo t t l e s . The samples were then innoculated with 5 uCi of radioactive carbonate. The bottles were placed i n a large mesh goodie bag containing 12 small compartments and submerged to a depth of 0.5 m at Station 1. The incubations ranged from 2 to 2.5 hrs i n length and occurred during mid-day following the morning sampling period. While Yellow Island seawater samples were innoculated almost immediately a f t e r c o l l e c t i o n , the samples from Quartz Bay had to be transported back to Yellow Island p r i o r to innoculation and incubation. Quartz Bay samples were innoculated approximately 2 hours a f t e r c o l l e c t i o n and incubated at Yellow Island, Station 1. Following incubation the samples were f i l t e r e d at a 1/3 atmospheric pressure vacuum through 47 mm AA M i l l i p o r e membrane f i l t e r s . The f i l t e r s were placed i n v i a l s containing 10 ml of Aquasol s c i n t i l l a t i o n c o c k t a i l and stored i n the dark u n t i l the r a d i o a c t i v i t y of the samples could be determined using an Isocap/SOO*1,1* l i q u i d s c i n t i l l a t i o n counter. The standard error of the primary 34 production values was calculated based on the standard deviation of the mean of the two c l e a r b o t t l e r e p l i c a t e s . Primary production rates were divided by the corresponding chlorophyll a values to produce production/biomass (P/B) r a t i o s . This primary productivity index has been established as a more accurate measure of comparing various photosynthetic rates (Lorenzen, 1963). F. Phytoplankton Species Composition For determining phytoplankton species composition, 150 ml samples were taken from the sampling bucket and preserved i n 250 ml glass bottles with 10-15 drops of Lugol's sol u t i o n . The samples were s e t t l e d i n 10 ml plankton chambers for at least 4 hrs p r i o r to counting. The phytoplankton was scanned at a magnification of 94.5 X (low power) on a Zeiss inverted microscope. The e n t i r e chamber bottom was viewed and the percent species dominance was estimated based on v i s u a l observation rather than c e l l counts. In addition, the ten most abundant species were ranked, from v i s u a l estimates of r e l a t i v e biomass. 35 6 . Dissolved Organic Carbon R e l a t i v e d i s s o l v e d o r g a n i c carbon c o n c e n t r a t i o n s were esti m a t e d from the a b s o r p t i o n of f i l t e r e d seawater samples a t 280 nm. Both Parsons et al. (1984) and Krom and S h o l k o v i t z (1977) have shown t h a t DOC absorbance a t 280 nm i s p r o p o r t i o n a l t o estimates of i t s c o n c e n t r a t i o n o b t a i n e d by dry combustion methods. Although no c o n c e n t r a t i o n s of DOC were determined i n t h i s s t u d y , absorbance was used t o get a r e l a t i v e measure of DOC c o n c e n t r a t i o n s . During the f i l t r a t i o n of the c h l o r o p h y l l a seawater samples, 50 ml of f i l t r a t e was c o l l e c t e d i n a t e s t tube suspended i n the f i l t r a t i o n f l a s k . The f i l t r a t e was f r o z e n (-20 C) i n 100 ml g l a s s b o t t l e s . In the l a b o r a t o r y , the samples were thawed and a b s o r p t i o n at 280 nm was measured u s i n g a C o l e m a n ™ 124D double beam spectrophotometer w i t h 100 mm p a t h - l e n g t h c u v e t t e s . H. Bacteria D i r e c t c o u n t i n g by f l u o r e s c e n c e microscopy was used t o determine b a c t e r i a l numbers w i t h a p r e c i s i o n a t the 10 x 105 c e l l s ' m l "1 l e v e l of + 2 x 105 c e l l s ' m l "1 (Parsons et a l . , 1984). To c o l l e c t b a c t e r i a l samples, 10 ml of seawater was withdrawn from the sampling bucket and i n j e c t e d i n t o a s c i n t i l l a t i o n v i a l c o n t a i n i n g 1 ml of f i l t e r e d 40% formaldehyde. The samples were r e f r i g e r a t e d a t 5 C i n the dark p r i o r t o c o u n t i n g . To determine b a c t e r i a l c o n c e n t r a t i o n s , one ml subsamples were dyed w i t h a c r i d i n e 36 orange and f i l t e r e d through a previously stained Nuclepore f i l t e r . B a c t e r i a l numbers were estimated from the mean of 10 f i e l d s counted at 400 X using a Zeiss standard 18 microscope. Standard errors were calculated based on the standard deviation of the mean of 10 f i e l d s . I . Data A n a l y s i s A l l c a l c u l a t i o n s used for the determinations of sigma-t values, chlorophyll a concentrations and primary prod u c t i v i t y rates were performed using the LOTUS™ 1-2-3 spreadsheet program. The SYSTAT™ data package was used for a l l the s t a t i s t i c a l t e sts and correlations needed i n t h i s study. In order to tes t for s t a t i s t i c a l differences i n the various water q u a l i t y and production parameters between stations at each location, data from the en t i r e summer for each parameter needed to be combined to increase sample s i z e . Sample sizes used i n the nonparametric t e s t f or determining differences between sta t i o n f o r various parameters are summarized i n Table 2. 37 T a b l e 2. A summary of the sampling f r e q u e n c i e s and s i z e s used i n the s t a t i s t i c a l t e s t s t o determine d i f f e r e n c e s between s t a t i o n s f o r t h e ^ v a r i o u s water q u a l i t y parameters s t u d i e d . ( ) r e f e r s t o primary p r o d u c t i v i t y v a l u e s determined only once per day. L O C A T I O N S A M P L I N G S / D A Y S A M P L I N G D A Y S S A M P L E O V E R S U M M E R S I Z E <n) Yellow I s l a n d 2 (1)* 4 n=32 (8)* Quartz Bay 1 3 n=12 The s m a l l sample s i z e s (8<n<32) made i t i m p o s s i b l e t o determine i f the s t a t i s t i c a l d i s t r i b u t i o n s f o r each parameter were normal and homoscedastic. In l i g h t of t h i s , the nonparametric K r u s k a l - W a l l i s s i n g l e f a c t o r a n a l y s i s of v a r i a n c e t e s t (Sokal and R o h l f , 1981) was used t o determine i f t h e r e were any s i g n i f i c a n t d i f f e r e n c e s between s t a t i o n s a t each l o c a t i o n f o r c o n c e n t r a t i o n s of t o t a l ammonia, c h l o r o p h y l l a, DOC and b a c t e r i a as w e l l as p r imary p r o d u c t i o n r a t e s and p r o d u c t i v i t y i n d i c e s . In o r d e r t o determine i f the l e v e l s of the examined parameters were s i g n i f i c a n t l y d i f f e r e n t i n the immediate v i c i n i t y of the pens compared t o ambient l e v e l s , the data were d i v i d e d i n t o i n n e r (mean v a l u e s of S t a t i o n s 0 and 1) and o u t e r (mean v a l u e s of S t a t i o n s 2 and 3) groups. T h i s a n a l y s i s was performed because s i m i l a r i t i e s i n the c o n c e n t r a t i o n s of v a r i o u s parameters w i t h i n the o u t e r and i n n e r s t a t i o n groupings would s t a t i s t i c a l l y mask any d i f f e r e n c e s between a l l s t a t i o n s i f they were compared 38 i n d i v i d u a l l y . The Mann-Whitney nonparametric two-sample rank sum t e s t (Sokl and R o l f , 1981) was employed t o t e s t f o r d i f f e r e n c e s between these two gr o u p i n g s . Two m a t r i c e s of Spearman c o r r e l a t i o n c o e f f i c i e n t s were c o n s t r u c t e d t o determine the r e l a t i o n s h i p s among the p h y s i c a l and b i o l o g i c a l parameters at Yellow I s l a n d and Quartz Bay. To do t h i s , data c o l l e c t e d over the e n t i r e summer from a l l s t a t i o n s were lumped t o g e t h e r at each l o c a t i o n . The r e s u l t i n g c o r r e l a t i o n s t h e r e f o r e r e f l e c t the e f f e c t of s e a s o n a l l y i n f l u e n c e d p h y s i c a l v a r i a b l e s such as s u r f a c e s a l i n i t y and water column s t r a t i f i c a t i o n on the b i o l o g i c a l v a r i a b l e s of i n t e r e s t . 39 IV. RESULTS A. P h y s i c a l S t u d i e s A comparison of the sigma-t p r o f i l e s of Yellow I s l a n d and Quartz Bay r e v e a l s a marked d i f f e r e n c e i n the water column s t a b i l i t y at the two l o c a t i o n s ( F i g . ' s 3A and 3B). Yellow I s l a n d appears t o be a w e l l mixed s i t e as no p y c n o c l i n e developed over the course of the summer. The Quartz Bay p r o f i l e c l e a r l y demonstrates the presence of a s t r o n g p y c n o c l i n e at 4 m depth d u r i n g the middle and l a t e summer. In order t o q u a n t i f y the magnitudes of s t r a t i f i c a t i o n at the two l o c a t i o n s , the d i f f e r e n c e s i n sigma-t v a l u e s at the s u r f a c e and 10 m depth were c a l c u l a t e d t o produce a s t r a t i f i c a t i o n parameter as f o l l o w s , S t r a t i f i c a t i o n = (sigma-t^g - sigma-tg)/ 10 m, where sigma-t^Q and sigma-tg are the r e s p e c t i v e 10 m depth and s u r f a c e v a l u e s . The h i g h e r the s t r a t i f i c a t i o n v a l u e , the g r e a t e r the degree of s t a b i l i t y i n the water column. The s t r a t i f i c a t i o n v a l u e s f o r Yellow I s l a n d and Quartz Bay are p r e s e n t e d i n Tables 3 and 4 , r e s p e c t i v e l y . 40 Figure 3. Sigma-t prof i les at Yellow Island (A) and Quartz Bay (B), summer, 1988. Yellow Island 0 2-\ ^ 4 IT I CL LU ° 8 10 12 22.0 22.2 22.4 22.6 22.8 23.0 e—J • — A — ' 1 i o \ \ o / / • o I I o • o • o A x O O 30/06 A I • • 07/08 \ A A 21/09 A A A A B. 16.0 0 4-8 -12-S 16-20 24 A i— Quartz Bay 18.0 20.0 22.0 24.0 — A -O » o o « o o o « o o o O O 01/07 • — • 08/08 ^ A A 2 0 / 0 9 • A i i « A i i < A i i i i « A « A 41 Table 3. Summary of p h y s i c a l data f o r Yellow I s l a n d between June and September, 1988. S t r a t i f i c a t i o n was determined as the average change i n sigma-t i n the top 10 m. PARAMETER TIDAL POSITION 30/06 SAMPLING DATES 06/08 07/08 21/09 S f c . Temp. ( c ) Mid 10.6 10.8 11.6 10.7 S f c . S a l i n i t y i 'oo ' Mid 29.18 29.24 29.33 29.69 S t r a t i f i c a t i o n (sigma-t u n i t s Mid .005 -.005 -.107 .022 S e c c h i Depth ( m ) Mid 11.0 7.5 7.0 10.0 E x t i n c t i o n C o e f f i c i e n t (m - 1 ) 0.15 0.23 0.24 0.17 Compensation Depth ( m ) 30 20 19 27 S f c . C u r r e n t . Speed ( em's Low ) High 17.5 6.5 4.8 37.5 5.6 20.6 7.1 18.2 42 Table 4. Summary of p h y s i c a l data f o r Quartz Bay between J u l y and September, 1988. S t r a t i f i c a t i o n was determined as the average change i n sigma-t i n the top 10 m. PARAMETER TIDAL POSITION SAMPLING 01/07 DATES 08/08 20/09 S f c . Temp. Mid ( c ) 15.8 14.3 10.9 S f c . S a l i n i t y Mid < °/oo ) 24.13 22.87 25.54 S t r a t i f i c a t i o n Mid (sigma-t u n i t s * m- 1) .161 .583 .272 S e c c h i Depth Mid ( m ) 9.0 5.0 5.5 E x t i n c t i o n C o e f f i c i e n t (m- 1) 0.19 0.34 0.31 Compensation Depth ( m ) 24 13 15 S f c . C u r r e n t Mid Speed ( em's" ) 7.5 4.0 11.0 43 Yellow I s l a n d had summertime s u r f a c e temperature and s a l i n i t y averages of 10.9 C and 29.36 ° /0 0 compared t o 13.7 C and 24.18 ° /0 0 summertime averages at Quartz Bay. The Quartz Bay l o c a t i o n experienced h i g h e r v a r i a b i l i t y i n both s u r f a c e temperature and s a l i n i t y v a l u e s over the course of the summer ( Tables 3 and 4 ) . Speeds from the c u r r e n t drogue s t u d i e s ranged from 6.5 t o 37.5 cm'sec"! at Yellow I s l a n d and 4.0 t o 11.0 cra'sec"^ at Quartz Bay. The drogues g e n e r a l l y t r a v e l l e d p a r a l l e l t o the expected ebb t i d e d i r e c t i o n s which were sou t h w e s t e r l y at Yellow I s l a n d and n o r t h w e s t e r l y at Quartz Bay. The S e c c h i d i s c depths and c o r r e s p o n d i n g e x t i n c t i o n c o e f f i c i e n t s f o r Yellow I s l a n d and Quartz Bay are summarized i n T a b l e s 3 and 4, r e s p e c t i v e l y . I t appears t h a t at both l o c a t i o n s , e x t i n c t i o n c o e f f i c i e n t s reach a maximum i n August w i t h the Yellow I s l a n d summertime average (k'= .20 m-"'") bein g c o n s i d e r a b l y lower than t h a t of Quartz Bay (k'= .28 m-"'"). In order t o get an estimate of the compensation depth at each l o c a t i o n , the e x t i n c t i o n c o e f f i c i e n t s were used i n the f o l l o w i n g e q u a t i o n , Id = I0'e-k.d , where 1^ and IQ are the r e s p e c t i v e l i g h t i n t e n s i t i e s at depth d and the s u r f a c e , and k i s the e x t i n c t i o n c o e f f i c i e n t of the water (Parsons et al., 1977). At the compensation depth ( Dc) , the r a t i o of I ^ / I0 can be approximated as .01 44 and the p r e c e d i n g equation reduces t o , Dc = - l n ( . 0 1 / k ) . C a l c u l a t e d compensation depths f o r Yellow I s l a n d and Quartz Bay are g i v e n i n Ta b l e s 3 and 4. B. T o t a l Ammonia and N i t r a t e The s u r f a c e c o n c e n t r a t i o n o f t o t a l ammonia a t Yellow I s l a n d w i t h i n the net-pens ( S t n . 0) ranged from 1.15 t o 3.03 uM between l a t e June and August. S u r f a c e c o n c e n t r a t i o n s at the o u t e r s t a t i o n ( S t n . 3) over the same time p e r i o d had a l a r g e r range of 1.02 t o 4.50 uM (Table 5 ) . The s p a t i a l d i s t r i b u t i o n s of t o t a l ammonia c o n c e n t r a t i o n s a t Yellow I s l a n d d u r i n g the f o u r sampling p e r i o d s are shown i n F i g u r e s 4A, 5A and 6A. The o n l y evidence of e l e v a t e d t o t a l ammonia c o n c e n t r a t i o n s i n the immediate v i c i n i t y of the net-pens was seen d u r i n g the low t i d e sampling p e r i o d on June 3 0t n ( F i g . 4 A ) . T o t a l ammonia a t Quartz Bay w i t h i n the net-pens and at the o u t e r s t a t i o n ranged from 2.00 t o 5.59 uM and 1.14 t o 3.40 uM, r e s p e c t i v e l y (Table 6 ) . T o t a l ammonia v a l u e s f o r the i n n e r two s t a t i o n at Quartz Bay are n o t i c e a b l y h i g h e r than the e q u i v a l e n t Yellow I s l a n d v a l u e s . A c l e a r p a t t e r n of e l e v a t e d t o t a l ammonia c o n c e n t r a t i o n s i n the immediate v i c i n i t y o f the net-pens i s seen i n e a r l y J u l y and l a t e September ( F i g . 7A). 45 T a b l e 5. Summary of water q u a l i t y d a t a f o r Ye l l o w I s l a n d , summer, 1988. (-) denotes m i s s i n g v a l u e s . PARAMETER STATION SAMPLING DATES 30/06 06/08 07/08 21/09 TOTAL AMMONIA 0 3.03 2.40 2.54 ( "M ) 1 2.48 2.45 — 2.08 2 1.79 1.98 — 3.71 Low T i d e 3 1.02 2.89 - 4.50 0 2.40 1.15 1.80 1.75 High T i d e 1 2.08 2.98 2.35 1.94 2 2.05 2.49 2.64 3.16 3 1.27 1.60 2.22 2.27 CHLOROPHYLL A 0 4.36 4.53 4.53 3.02 ( mg C h i a*m"3) 1 1.34 3.75 4.08 2.89 2 2.02 4.73 4.17 3.98 Low T i d e 3 1.74 5.06 4.19 3.39 0 3.28 4.73 2.35 2.92 High T i d e 1 1.98 3.67 3.06 3.01 2 1.66 3.98 3.93 3.28 3 1.63 3.86 3.86 2.73 P/B 0 0.80 1.84 0.59 1.33 (mg C'mg'Chl a- 1. 1 2.19 0.80 1.02 2.87 h r "1) 2 1.14 1.61 0.80 0.54 Low T i d e 3 1.27 0.92 1.00 0.26 BACTERIA 0 5.42 6.04 7.50 " 3.70 ( c e l l s * m l "1x l 05) 1 6.34 3.48 8.44 2.46 2 5.96 6.78 9.92 3.36 Low T i d e 3 6.64 5.10 7.26 4.12 0 5.04 4.44 5.42 3.86 High T i d e 1 5.38 6.34 5.52 3.56 2 5.58 6.98 6.32 3.60 3 4.90 6.40 7.52 4.02 DOC ABSORBANCE 0 .090 .146 .132 .153 ( 280 nm ) 1 .116 .158 .132 .188 2 .253 .253 .161 .216 Low T i d e 3 .187 .253 .234 .106 0 .211 .172 .111 .106 High T i d e 1 .151 .166 .204 .077 2 .209 .129 .167 .138 3 .195 .192 .168 .140 46 Table 6. Summary of water q u a l i t y data f o r Quartz Bay, summer '88. A l l samples were taken between low and mid t i d e . PARAMETER STATION SAMPLING DATES 01/07 08/08 20/09 TOTAL AMMONIA 0 5.59 2.00 5.17 ( ) 1 5.34 2.63 4.57 2 2.74 1.63 1.90 3 3.40 1.14 2.15 CHLOROPHYLL A 0 5.06 8.47 3.58 ( mg C h i a'm"3 ) 1 3.76 7.21 3.37 2 2.39 6.51 4.89 3 3.00 6.77 5.21 P/B 0 1.57 1.67 2.10 (mg C'mg C h i a "1 . 1 1.05 1.66 1.62 h r- 1) 2 1.31 1.26 2.33 3 1.46 1.57 1.97 BACTERIA . 0 9.20 13.22 7.42 ( c e l l s * m l "1x l 05) 1 14.84 17.38 5.20 2 18.40 14.98 6.50 3 17.60 15.28 5.24 DOC ABSORBANCE 0 .224 .150 .178 ( 280 nm ) 1 .252 .166 .161 2 .239 .105 .111 3 .206 .134 .131 47 F i g u r e 4. T o t a l ammonia (A) and c h l o r o p h y l l a (B) c o n c e n t r a t i o n s a t Y e l l o w I s l a n d , l a t e June, 1988. c O c o <_> 4 .00 c £ 'c o E E < 2.00-1.00 0 TOTAL AMMONIA Yellow Island LZ3 30 /06 /11 :00 WM 30 /06 /16 :00 STATION B. PHYTOPLANKTON BIOMASS Yellow Island 1 6.00-I (mg/ 5.00-ltration 4 .00-Concer 3.00-o -ophyll 2.00-Chloi 1.00-C D 30 /06 /11 :00 • I 30 /06 /16 :00 l_Qi 1 2 STATION F i g u r e 5. T o t a l ammonia (A) and c h l o r o p h y l l a (B) c o n c e n t r a t i o n s a t Y e l l o w I s l a n d , mid-August, 1988. c V u c o o 4.00 c I 3.00 £ 'c o E E < 2.00 1.00 TOTAL AMMONIA Yellow Island [ZD 06/08/10:00 WM 06/08/14:30 1 STATION B. E, c o c a> o c o o sz CL O O 7.00 6.00 5.00 4.00-1 3.00 2.00 PHYTOPLANKTON BIOMASS Yellow Island • 06/08/10:00 • i 06/08/16:00 STATION Figure 5 . Con't. A. 4.00 TOTAL AMMONIA Yellow Island B. cn E, c o c a> u c o o CL e o x: o 7.00-6 .00-5 .00 -4 . 0 0 -3 .00 -2 .00 -PHYTOPLANKTON BIOMASS Yellow Island CZJ 0 7 / 0 8 / 1 0 : 0 0 • • 0 7 / 0 8 / 1 4 : 0 0 1 STATION F i g u r e 6. T o t a l ammonia (A) and c h l o r o p h y l l a (B) c o n c e n t r a t i o n s a t Y e l l o w I s l a n d , l a t e September, 1988. 6.00-^ 5.00--b 4.00 • 3.00-2.00-1 . 0 0 -TOTAL AMMONIA Yellow Island 1_NI • 21/09/9:00 • i 21/09/13:00 1 STATION B. 6.00-5.00-PHYTOPLANKTON BIOMASS Yellow Islond CD 21/09/9:00 • i 21/09/13:00 4.00-3.00-2.00 I I 111 Ii I STATION 51 F i g u r e 7 T o t a l ammonia (A) and c h l o r o p h y l l a (B) c o n c e n t r a t i o n s a t Quartz Bay, summer, 1988. A. c o 6.00 ^ 5.00-c 0> o c o o E 'c o E E < 4.00 3.00-2.00 1.00 TOTAL AMMONIA Quartz Bay STATION B. cn E_ c o E -«-» c a> o c o o D 3^  D-e _o J : o 10.00 9.00 8.00 7.00 6.00 5.00 4.00 3.00 2.00 PHYTOPLANKTON BIOMASS Quartz Bay CD 01 /07 /12 :00 H 08 /08 /11 :00 20 /09 /10 :00 J 1 2 STATION 52 F i g u r e 8. 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 a t Y e l l o w I s l a n d and Quartz Bay, l a t e J u n e / e a r l y J u l y , 1988* NITRATE AND NITRITE CONCENTRATION 2 2 5 . 0 0 -j c o o-> 2 0 . 0 0 -o i _ c OJ o 1 5 . 0 0 -c o o OJ 1 0 . 0 0 -Z2L X> c o 5 . 0 0 -OJ "o iz 0 . 0 0 - -Yellow Island 3 0 / 0 6 / 1 6 : 0 0 Quar tz Bay 0 1 / 0 7 / 1 2 : 0 0 0 1 2 STATION 53 When data from a l l sampling p e r i o d s were combined f o r each s t a t i o n , no s i g n i f i c a n t d i f f e r e n c e s (p<.05) were observed between a l l f o u r s t a t i o n s f o r t o t a l ammonia c o n c e n t r a t i o n s at e i t h e r Quartz Bay or Yellow I s l a n d (Table 7 ) . I f the i n n e r and outer two s t a t i o n s are lumped t o g e t h e r , however, a s i g n i f i c a n t l y h i g h e r t o t a l ammonia l e v e l (p<.05) i n the immediate v i c i n i t y of the pens i s seen a t Quartz Bay (Table 8 ) . The e f f e c t s of f r e e z i n g on the v a r i a b i l i t y of the t o t a l ammonia d e t e r m i n a t i o n s made i n t h i s study are d i s c u s s e d i n appendix 1. A c i d i c contamination r e s u l t e d i n the l o s s of a l l n i t r a t e samples w i t h the e x c e p t i o n of those taken at the f i r s t sampling p e r i o d at both Yellow I s l a n d and Quartz Bay. N i t r a t e v a l u e s at both l o c a t i o n s appeared v e r y c o n s t a n t between s t a t i o n s ( F i g . 8 ) , w i t h the mean v a l u e at Yellow I s l a n d (15.0 uM) c o n s i d e r a b l y h i g h e r than the mean a t Quartz Bay (2.5 uH). C. Phytoplankton Standing Stock S u r f a c e 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 at S t a t i o n s 0 and 3 at Yellow I s l a n d ranged from 2.35 t o 4.73 mg Chi a*m and 1.63 t o 5.06 mg Chi a'm""3, r e s p e c t i v e l y (Table 5 ) . The only evidence of h i g h e r c h l o r o p h y l l a l e v e l s i n the immediate v i c i n i t y of the net-pens i s seen i n l a t e June ( F i g . 4B). A l l other sampling p e r i o d s show no obvious p a t t e r n s of c h l o r o p h y l l a d i s t r i b u t i o n between s t a t i o n s ( F i g . ' s 5B, and 6B). 54 Quartz Bay summer c h l o r o p h y l l a s u r f a c e c o n c e n t r a t i o n s • a , ranged from 3.58 t o 8.47 mg C h i a'm a t S t a t i o n 0 and 3.00 t o 6.77 mg C h i a'm-3 at S t a t i o n 3 (Table 6 ) . N o t i c e a b l y h i g h e r 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 i n the immediate v i c i n i t y of the net-pens were observed i n e a r l y J u l y and mid-August ( F i g . 7B). 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 a t both Yellow I s l a n d and Quartz Bay showed no s i g n i f i c a n t d i f f e r e n c e s (p<.05) between a l l s t a t i o n s ( t a b l e 7) and between the i n n e r and outer s t a t i o n groupings ( t a b l e 8 ) . D. Primary P r o d u c t i v i t y I n s p e c t i o n of f i g u r e 9A r e v e a l s t h a t t h e r e was a high amount of v a r i a b i l i t y i n the r a t e s of primary p r o d u c t i o n at Y e llow I s l a n d a t a l l s t a t i o n s over the course of the summer. The range of p h o t o s y n t h e t i c r a t e s were l a r g e r a t S t a t i o n 0 (2.67 t o 8.23 mg C'm"3 ,hr~1) compared t o those a t S t a t i o n 3 (0.88 t o 4.66 mg C 'm~3'hr- 1). The ranges of production/biomass (P/B) r a t i o s seen a t S t a t i o n s 0 and 3 (Table 5) do not show any marked d i f f e r e n c e . Although r a t e s of primary p r o d u c t i o n appear t o be enhanced i n the v i c i n i t y of the net-pens i n June and August ( F i g . 9A), t h i s e f f e c t i s not r e f l e c t e d i n the c o r r e s p o n d i n g p r o d u c t i v i t y i n d i c e s ( F i g . 10A). Primary p r o d u c t i v i t y e s t i m a t e s a t Quartz Bay a l s o e x h i b i t e d a l a r g e amount of v a r i a b i l i t y over the course of the summer ( F i g . 9B). P h o t o s y n t h e t i c r a t e s a t S t a t i o n 0 o i ranged from 5.16 t o 14.12 mg C m hr w h i l e those at Station 3 varied from 4.33 to 10.61 mg C*m~ J*hr~. These production values are considerably higher than those observed at Yellow Island. Although the production/biomass r a t i o s at Quartz Bay (Table 6) are on the whole higher than those for Yellow Island, the difference between the two locations P/B r a t i o s i s smaller than the difference i n primary production values. Increased rates of primary production i n the v i c i n i t y of the net-pens at Quartz Bay were observed only i n August (Fig. 9B), however t h i s e f f e c t was not seen i n the pattern of productivity indices between stations at any point i n the summer (Fig. 10B). No s i g n i f i c a n t differences (p<.05) i n photosynthetic rates or P/B r a t i o s at Quartz Bay or Yellow Island were detected between a l l stations (Table 7) or between the inner and outer s t a t i o n groupings (Table 8). 56 Table 7. Summary of r e s u l t s of K r u s k a l - W a l l i s (K-W) One-way A n a l y s i s of V a r i a n c e t o determine s i g n i f i c a n t d i f f e r e n c e s between a l l s t a t i o n s at Yellow I s l a n d and Quartz Bay. (-) denotes an acceptance (PROB > .05) of the n u l l h y p o t h e s i s ( HQ) , demonstrating no s i g n i f i c a n t d i f f e r e n c e s between s t a t i o n s . WATER QUALITY PARAMETER LOCATION SAMPLE SIZE K-W TEST STATISTIC PROB. ( p > Ho • TOTAL AMMONIA Yellow 28 0.771 .856 Quartz 12 4.385 .223 -CHLOROPHYLL A Yellow 32 2.830 .419 _ Quartz 12 0.641 .887 -PRIMARY Yellow 16 1.346 .718 _ PRODUCTION Quartz 12 0.282 .963 -P/B Yellow 16 1.994 .574 Quartz 12 1.564 .658 -BACTERIA Yellow 32 1.645 .649 _ Quartz 12 1.051 .789 -DOC ABSORBANCE Yellow 32 6.108 .106 _ Quartz 12 2.179 .536 -57 Table 8. Summary of r e s u l t s of the Mann-Whitney (M-W) U-Test t o determine s i g n i f i c a n t d i f f e r e n c e s between the means of the i n n e r ( s t n . 0 and 1) and outer ( s t n . 2 and 3) s t a t i o n s f o r Yellow I s l a n d and Quartz Bay. (-) denotes an acceptance (PROB > .05) of the n u l l h y p o t h e s i s ( HQ) , demonstrating no s i g n i f i c a n t d i f f e r e n c e s between the i n n e r and oute r s t a t i o n s . (+) denotes r e j e c t i o n of the n u l l h y p o t h e s i s (PROB < .05). WATER QUALITY PARAMETER LOCATION SAMPLE SIZE M-W TEST STATISTIC PROB. < P ) Ho • TOTAL AMMONIA Yellow 28 100.0 .927 Quartz 12 31.0 .037 + CHLOROPHYLL A Yellow 32 120.0 .763 _ Quartz 12 21.0 .631 -PRIMARY Yellow 16 43.0 .248 _ PRODUCTION Quartz 12 19.0 .873 -P/B Yellow 16 43.5 .227 _ Quartz 12 21.0 .631 -BACTERIA Yellow 32 94.0 .200 _ Quartz 12 12.0 .337 -DOC ABSORBANCE Yellow 32 63.5 .015 + Quartz 12 27.0 . 150 -58 Figure 9. Hourly Yellow 1988. mean. and dai ly photosynthetic rates at Island (A) and Quartz Bay (B), summer, Bars indicate 1 standard error of the PRIMARY PRODUCTION Yellow Island 12.0 E 10.0 o |> 8.0 "5 6.0 or o '» 4.0 sz I 2.0 o CL. 0.0 1 i CD 30/06 WM 06/08 E S 07/08 EZ2 21/09 i 150 o T J O 100 CT) —^* O or u 50 ~ c to o STATION B. 16.0 12.0 o E •S 8.0 ce f 4.0 > s CO o o x: CL 0.0 PRIMARY PRODUCTION Quartz Bay I CZI 01/07 WM 08/08 E S 20/09 1 2 STATION O E 150 ^ C P 100 | or 50 f o o o or 59 Figure 10. Productivity indices (production/biomass) at Yellow Island (A) and Quartz Bay (B), summer, 1988. A. o E c o It** u TJ O PRODUCTMTY INDEX Yellow Island 4.0 3.0-o CT E ~ 2.0 + V) if> o E o ba L O -CO J M 0 I 1=1 30/06 H 06/08 07/08 2Z2 21/09 li I 1 STATION B. o o> E \ o J . <o 0) o E o m \ c o ~o o PRODUCTIVrTY INDEX Quartz Boy 4.0 3.0 •-2 . 0 - -1.0--0.0 H3 01/07 • i 08/08 20/09 111 1 2 STATION 60 E. Phytoplankton Species Composition Diatoms were the dominant c l a s s of phytoplankton observed at Yellow I s l a n d throughout the course of the summer. A number of b e n t h i c diatoms i n c l u d i n g , Melosira moniliformis, Fragilaria spp., n a v i c u l o i d s and Odontella aurita as w e l l as the p e l a g i c s p e c i e s Skeletonema costatum were the dominant organisms observed i n l a t e June and comprised 7 0 t o 95% of the t o t a l phytoplankton biomass ( F i g . 11A). Low l e v e l s of d i n o f l a g e l l a t e s and cryptomonads were o n l y seen i n l a t e June at which time the p h o t o s y n t h e t i c c i l i a t e Mesodinium rubrum reached dominance l e v e l s of up t o 25% a t the outer two s t a t i o n s ( F i g . 11A) . By the second sampling p e r i o d (August 6 ) , the p l a n k t o n i c diatoms Skeletonema costatum, Nitzschia pungens, Chaetoceros debile and Thalassiosira rotula comprised 95 t o 98% of the biomass of phytoplankton and t h i s p a t t e r n c o n t i n u e d i n t o the f i n a l sampling p e r i o d i n September. The s p e c i e s composition at Quartz Bay d u r i n g the f i r s t sampling p e r i o d ( J u l y 1) e x h i b i t e d a much more v a r i e d c o mposition than t h a t of Yellow I s l a n d . Maximum diatom dominance i n e a r l y J u l y was observed at S t a t i o n 0 (20%) and dropped t o v a l u e s as low as 5% at the o u t e r s t a t i o n s . T h i s diatom biomass was made up mainly of Odontella aurita, Melosira moniliformis and Eucampia zoodiacus. A much l a r g e r p r o p o r t i o n of the Quartz Bay biomass was comprised of h e t e r o t r o p h i c d i n o f l a g e l l a t e s ( 2 0 % ) , cryptomonads (30%) and 6 1 e u g l e n o i d s ( 4 0 % ) . Mesodinium rubrum reached maximum abundance l e v e l s of 50% of the t o t a l at the o u t e r s t a t i o n s ( F i g . 11B). By the second sampling p e r i o d (August 8 ) , the d i v e r s e s p e c i e s composition had been r e p l a c e d by one c o n s i s t i n g of 95% diatoms. The diatoms Skeletonema costatum, Nitzschia pungens, Thalassiosira aestivalis and Thalassiosira rotula remained dominant u n t i l the f i n a l sampling p e r i o d i n l a t e September. A complete l i s t of the phytoplankton s p e c i e s observed at Yellow I s l a n d and Quartz Bay over the course of the summer i s g i v e n i n Table 12, Appendix I I . Phytoplankton s p e c i e s c o m p o s i t i o n a t Yellow I s l a n d (A) and Quartz Bay ( B ) , l a t e June/ e a r l y J u l y , 1988. PHYTOPLANKTON SPECIES COMPOSITION Yellow Island (30/06) L"ZD DIATOMS WM DINOFLAGELLATES CRYPT0M0NADS EZ3 CILIATES J STATION PHYTOPLANKTON SPECIES COMPOSITION Quartz Boy (01/07) CZ3 100-80-V7A DIATOMS DINOFLAGELLATES CRYPT0M0NADS CILIATES EUGLENOIDS 60-40-20-i 0 R X X K K X X X » 1 x I! i l l J \ v \ V \ V v \ v \ v \ \ v t v. La STATION 63 F . Dissolved Organic Carbon Absorbance and Bacterial Numbers Dissolved organic carbon absorbance (i.e. 280 nm absorbance) at Yellow Island and Quartz Bay ranged from .090 to .253 units and .105 to .252 units, respectively (Tables 5 and 6). Figures 12A through 15A do not demonstrate any DOC enrichment in the vicinity of the net-pens. No significant differences (p<.05) in DOC absorbance between a l l stations (Table 7) were found for either Yellow Island or Quartz Bay. Significantly higher DOC absorbances (p<.05) were observed at the outer stations at Yellow Island but not at Quartz Bay (Table 8). Bacterial concentrations at Yellow Island ranged from 3.36 to 9.92 x 105 cells'ml- 1 (Table 5). Bacterial numbers at Quartz Bay were on average two-fold higher with concentrations ranging from 5.20 to 18.40 x 10^ cells"ml-* (Table 6). Inspection of Figures 12B through 15B reveals no obvious patterns in the spatial distributions of bacteria at both locations. Bacterial concentrations do appear to drop off during the last sampling periods at both Yellow Island and Quartz Bay. No significant differences (p<.05) in bacterial numbers between a l l stations (Table 7) and between the inner and outer station groupings (Table 8) were found for either Yellow Island or Quartz Bay. Figure 12. DOC absorbance (A) and bacter ia l numbers at Yellow Island, late June, 1988. Bars indicate 1 standard error of the mean. DOC ABSORBANCE Yellow Island E c o CO CM v ' CD O C o •e o < 0.500 0.400 0.300 0.200 0.100 0.000 CD 30 /06 /11 :00 • • 30 /06 /16 :00 STATION B. 1.0E6 £ 8.0E5 © O o o ca O 6.0E5-4.0E5 BACTERIAL NUMBERS Yellow Island i CZJ 30 /06 /11 :00 M 30 /06 /16 :00 i STATION Figure 13. DOC absorbance (A) and bacter ia l numbers ( at Yellow Island, mid-August, 1988. Bars indicate 1 standard error of the mean. DOC ABSORBANCE Yellow Island E c O CD CN 0) O c o Xi k_ o 10 Xi < 0.500 0.400 0.300 0.200 0.100 0.000 C D 0 6 / 0 8 / 1 0 : 0 0 WM 0 6 / 0 8 / 1 4 : 3 0 •MM STATION B. 1.0E6 8.0E5 4> O -2 6.0E5 "o o m ^ 4-.0E5 o 2.0E5 BACTERIAL NUMBERS Yellow Island LZD 0 6 / 0 8 / 1 0 : 0 0 • • 06 /08 /14 :30 1 STATION Figure 13. Con't. E c o CO CM CD O c o •e o m Xi < o o D m o 0.500 0.400 0.300 0.200 0.100 0.000 B. 2.0E6 1.5E6 5 1.0E6 • "S 5.0E5 0.0 DOC ABSORBANCE Yellow Island CD 07/08/10:00 WM 07/08/14:00 1 STATION BACTERIAL NUMBERS Yellow Island CD 07/08/10:00 •• 07/08/14:00 STATION 67 Figure 14. DOC absorbance (A) and bacter ia l numbers (B) at Yellow Island, late September, 1988. Bars indicate 1 standard error of the mean. DOC ABSORBANCE Yellow Island E c o 00 CM •—s © U c o X I L_ o m 0.500 0.400 0.300 0.200 0.100 0.000 1 CZ) 2 1 / 0 9 / 9 : 0 0 WM 21 /09 /13 :00 I II nl STATION B. BACTERIAL NUMBERS Yellow Island 5.0E5 = 4.0E5 o o V & 3.0E5 o 2.0E5 CZI 21 /09 /9 :00 WM 21 /09 /13 :00 1 2 3 STATION Figure 15. DOC absorbance (A) and bacter ia l numbers (B) at Quartz Bay, summer, 1988. Bars indicate 1 standard error of the mean. E c O CO CM © O c o x> o m -O < 0.500 0.400 0.300 0.200 0.100 0.000 DOC ABSORBANCE Quartz Bay 111 LZ3 01 /07 /12 :00 • I 08 /08 /11 :00 ES3 20 /09 /10 :00 1 2 STATION B. 3.0E6 ~ 2.5E6 £ = 2.0E6 © o 5 1.5E6 © S 1-0E6 o * 5.0E5 0.0 BACTERIAL NUMBERS Quartz Bay C D 01 /07 /12 :00 Mm 08 /08 /11 :00 E 3 20 /09 /10 :00 J , I 1 I STATION 69 6 . H a t e r Q u a l i t y P a r a m e t e r I n t e r a c t i o n s Summaries of the r e s u l t s of the Spearman c o r r e l a t i o n m a t r i c e s f o r the Yellow I s l a n d and Quartz Bay water q u a l i t y d a t a are g i v e n i n Tables 9 and 10, r e s p e c t i v e l y . To c o n s t r u c t these m a t r i c e s , data c o l l e c t e d over the e n t i r e summer a t each s t a t i o n were lumped t o g e t h e r f o r both Quartz Bay and Yellow I s l a n d . The c o r r e l a t i o n s a re t h e r e f o r e u s e f u l i n determining the e f f e c t s of seaso n a l changes i n p h y s i c a l parameters on the v a r i o u s water q u a l i t y parameters i n v e s t i g a t e d . The c o r r e l a t i o n between c h l o r o p h y l l a and r a t e s of p h o t o s y n t h e s i s at Quartz Bay demonstrates the l a r g e degree of i n f l u e n c e t h a t phytoplankton s t a n d i n g s t o c k has on est i m a t e s o f primary p r o d u c t i v i t y and warrants the use of P/B r a t i o s t o es t i m a t e t r u e changes i n carbon uptake r a t e s . Many of the b i o l o g i c a l parameters a t Quartz Bay are c o r r e l a t e d w i t h seasonal changes i n p h y s i c a l v a r i a b l e s such as water column s t r a t i f i c a t i o n and s u r f a c e temperature. C h l o r o p h y l l a and primary p r o d u c t i v i t y are p o s i t i v e l y c o r r e l a t e d w i t h s u r f a c e temperature a t Yellow I s l a n d and water column s t r a t i f i c a t i o n a t Quartz Bay. A summary of the e f f e c t of the salmon farms on the water q u a l i t y measures i n v e s t i g a t e d i n t h i s study i s g i v e n i n Tabl e 11. 70 T a b l e 9. Spearman nonparametric c o r r e l a t i o n m a t r i x of the Yellow I s l a n d water q u a l i t y d a t a Sample s i z e f o r each c o e f f i c i e n t i s 12. AMM. CHL A. C14. PB. BAC. DOC. AMM. CHL A. C14. + PB. -BAC. DOC. STRAT. -TEMP. ++ + SALINITY -SECCHI. — -+ = S i g n i f i c a n t p o s i t i v e c o r r e l a t i o n ( p < .05 ) ++ = S i g n i f i c a n t p o s i t i v e c o r r e l a t i o n ( p < .01 ) = S i g n i f i c a n t n e g a t i v e c o r r e l a t i o n ( p < .05 ) — = S i g n i f i c a n t n e g a t i v e c o r r e l a t i o n ( p < .01 ) AMM. = T o t a l Ammonia c o n c e n t r a t i o n CHL A. = 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 C14. = Primary P r o d u c t i v i t y PB. = Production/Biomass r a t i o DOC. = D i s s o l v e d Organic Carbon absorbance BAC. = B a c t e r i a l numbers STRAT. = S t r a t i f i c a t i o n TEMP. = S u r f a c e Temperature SALINITY= S u r f a c e S a l i n i t y SECCHI = S e c c h i D i s c Depth 71 Table 10. Spearman nonparametric correlation matrix for the Quartz Bay water quality data. Sample size for each coefficient i s 12. AMM. CHL A. C14. PB. BAC. DOC. AMM. CHL A. -C14. - ++ + PB. BAC. -DOC. ++ - — STRAT. — ++ ++ — TEMP. - — ++ + SALINITY - -SECCHI. -+ = Significant positive correlation ( p < .05 ). ++ = Significant positive correlation ( p < .01 ). - = Significant negative correlation ( p < .05 ). — = Significant negative correlation ( p < .01 ). AMM. = Total Ammonia concentration CHL A. = Chlorophyll a concentration C14. = Primary Productivity PB. = Production/Biomass rat io BAC. *= Bacterial numbers DOC. = Dissolved Organic Carbon absorbance STRAT. = Strat i f icat ion TEMP. = Surface Temperature SALINITY= Surface Sal ini ty SECCHI = Secchi Disc Depth 72 Table 11. Summary of changes i n physical and b i o l o g i c a l water q u a l i t y parameters at Yellow Island and Quartz Bay over the course of the summer, 1988. (++) denotes the presence of a pos i t i v e gradient i n t o t a l ammonia or production measures from Station 0 or 1 to Station 3. PARAMETER JULY AUGUST SEPTEMBER YELLOW ISLAND QUARTZ BAY YELLOW ISLAND QUARTZ BAY YELLOW ISLAND QUARTZ BAY . TOTAL AMMONIA ++ ++ ++ CHLOROPHYLL A ++ ++ ++ PHOTOSYNTHETIC RATE ++ ++ ++ PRODUCTIVITY INDEX DISSOLVED ORGANIC CARBON BACTERIAL NUMBERS STRATIFICATION none weak none strong none weak SECCHI DISC DEPTH (m) 11.0 9.0 7.2 5.0 10.0 5.5 SURFACE WATER TEMPERATURE C 10.6 15.8 11.2 14.3 10.7 10.9 SURFACE SALINITY ° / Q O 29.2 24.1 29.3 22.9 29.7 24.9 V. DISCUSSION The physical measurements taken i n t h i s study indicate some marked differences i n the flushing c h a r a c t e r i s t i c s of the Yellow Island and Quartz Bay locations. Yellow Island experiences greater mixing as witnessed by the lack of any appreciable pycnocline compared to the strong s t r a t i f i c a t i o n seen at Quartz Bay (Fig. 3). Maximum current speeds at Quartz Bay were considerably less than those measured at Yellow Island (Tables 3 and 4). Given the narrower width of the mouth of Quartz Bay and the more protected p o s i t i o n of the farm within the embayment (Fig. 2), there i s no doubt that the Yellow Island salmon farm undergoes a stronger fl u s h i n g regime. The timing and extent of t o t a l ammonia enrichment at the two locations vary considerably. The only strong evidence f o r higher ammonium l e v e l s i n the immediate area of the farm at Yellow Island i s seen i n l a t e June during the low t i d e sampling period (Fig. 4A). An understanding of the seasonal changes i n ammonium concentrations i n the Discovery Passage area may explain the timing of the Yellow Island enrichment. From work done on the Campbell River estuary, Seki et al. (1987 and 1984) demonstrated an increase i n near-shore surface ammonium concentrations (ca. 10 km south of Yellow Island on western shore of Quadra Island) of 1.6 uM to 6.3 uM between May and August, 1983. This summertime increase followed a large r i s e i n surface 74 s a l i n i t y which r e f l e c t s the i n t r u s i o n of n u t r i e n t - r i c h c o a s t a l water and replacement of the l e s s s a l i n e , n u t r i e n t -impoverished water a s s o c i a t e d w i t h the s p r i n g f r e s h e t . I f the r i s e i n s u r f a c e s a l i n i t y and t o t a l ammonia l e v e l s i n the out e r two s t a t i o n s seen a t Yellow I s l a n d over the course of the summer (Tables 3 and 5) are any i n d i c a t i o n o f the t r e n d i n ambient ammonium l e v e l s , then one would expect t o see the most n o t i c e a b l e t o t a l ammonia enrichment i n the v i c i n i t y of the farm a t the beginning of the summer when ambient c o n c e n t r a t i o n s were l o w e s t . R i s i n g background l e v e l s of ammonium over the course of the summer would swamp any enhancement i n t o t a l ammonia c o n c e n t r a t i o n s r e s u l t i n g from the c u l t u r e a c t i v i t i e s . The l o s s of the s t r i k i n g t o t a l ammonia g r a d i e n t d u r i n g the hig h t i d e sampling p e r i o d i n l a t e J u n e ( F i g . 4A) c o u l d have been caused by the d i l u t i o n o f d i s s o l v e d ammonium around the farm by the r e l a t i v e l y ammonium-poor waters r i s i n g d u r i n g the development o f the n e a r - s p r i n g h i g h t i d e . Increases i n ammonium uptake r a t e s of phytoplankton d u r i n g the l a t t e r p a r t of the day r e s u l t i n g from exposure t o hi g h e r l i g h t l e v e l s c o u l d a l s o have c o n t r i b u t e d t o decreases i n t o t a l ammonia l e v e l s observed at the i n n e r s t a t i o n s d u r i n g the a f t e r n o o n sampling p e r i o d . The s p a t i a l d i s t r i b u t i o n of s u r f a c e ammonium c o n c e n t r a t i o n s a t Quartz Bay shows s i g n i f i c a n t v a r i a t i o n over the course of the summer ( F i g . 7A). Conspicuous ammonium g r a d i e n t s between S t a t i o n s 0 and 3 are seen i n 75 e a r l y J u l y and l a t e September. During the August sampling p e r i o d , however, t o t a l ammonia l e v e l s were c o n s i d e r a b l y lower (Table 6) and no enrichment from the farm was a p p arent. During t h i s time p e r i o d , 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 roughly t w o - f o l d h i g h e r than l e v e l s measured i n e a r l y J u l y and l a t e September (Table 6 ) . The l a c k of any ammonia enrichment may be r e l a t e d t o the s t r o n g s t r a t i f i c a t i o n observed i n August ( F i g . 3B) and i t s subsequent i n f l u e n c e on phytoplankton biomass. S t r a t i f i c a t i o n i n the top 10 m i n August a t Quartz Bay was over t h r e e f o l d g r e a t e r than i n e a r l y J u l y and two f o l d g r e a t e r compared t o l a t e September (Table 4 ) . The s t r o n g c o r r e l a t i o n (P<.01) between s t r a t i f i c a t i o n and c h l o r o p h y l l a (Table 10) suggests t h a t i n c r e a s i n g s t a b i l i t y of the water column a t Quartz Bay l e a d s t o h i g h e r l e v e l s of phytoplankton biomass. E l e v a t i o n s i n a l g a l ammonium uptake and u t i l i z a t i o n per volume of water, would of c o u r s e , accompany t h i s r i s e i n biomass. Thus i t i s not s u r p r i s i n g t h a t t o t a l ammonia l e v e l s a t Quartz Bay are s e v e r e l y depressed d u r i n g p e r i o d s when c h l o r o p h y l l a l e v e l s are v e r y h i g h ( F i g . ' s 7A and 7B). The s t r o n g n e g a t i v e c o r r e l a t i o n (p<.01) between c h l o r o p h y l l a and t o t a l ammonia confirms t h i s o b s e r v a t i o n (Table 10). The l a c k of any enhancement of t o t a l ammonia l e v e l s i n the v i c i n i t y of the farm d u r i n g the August sampling p e r i o d i s s u r e l y the r e s u l t of i n c r e a s e s i n a l g a l ammonium uptake per volume of water d u r i n g t h i s time p e r i o d . 76 The t o t a l ammonia data presented here also give some in d i c a t i o n of the importance of ammonium loading caused by the excretion of fouling organisms. Total ammonia l e v e l s within the net-pens at Yellow Island and Quartz Bay during periods of maximum enrichment were respectively 2.0 and 2.5 f o l d higher than ambient l e v e l s measured at Station 3. As outlined i n the introduction, the salmon farms that were investigated i n t h i s study would produce roughly 20 kg'NH^-N'day-^ through salmonid excretion alone. Under stagnant flushing conditions, t h i s loading would produce an increase of ca. 100 uM NH4-N*day""A within the pens assuming a t o t a l pen volume of 12000 m (12 stocked pens with volumes of 1000 m ). From the current speeds measured immediately downcurrent of the net-pens (Tables 3 and 4), the minimum flushing time for any pen based on the lowest current speed observed (4.0 cm*s""A) would be just over 4 minutes (ca. 350 volumes*day~ A). Considering t h i s flushing rate, the maximum increase i n t o t a l ammonia l e v e l s inside the pens should be no greater than 0.30 uM NH4-N at any time (100 uM NH4-N*day"1/350 f l u s h i n g s ' d a y - 1 ) . The elevated t o t a l ammonia l e v e l s seen within the pens at Quartz Bay and Yellow Island must therefore be a r e s u l t of more than ammonium loading from salmonid excretion alone. The only other s i g n i f i c a n t source of ammonium i n the pens would come from the excretion of fouling organisms on the nets and r a f t structures. 77 The effect of the elevated ammonium levels on the photosynthetic rates and densities of phytoplankton surrounding the culture f a c i l i t i e s w i l l depend on the ambient l i ght , temperature and nutrient conditions to which the algal ce l l s are exposed. The compensation depths calculated for Yellow Island and Quartz Bay ranged from 13-30 m (Tables 3 and 4). Given the high l ight levels and long days characterist ic of the summer months, the deep compensation depths observed at Yellow Island and the strong s trat i f i ca t ion seen at Quartz Bay, i t seems unlikely that phytoplankton found at the surface would be l ight l imited at either location during the summer. Temperature and ambient nitrogen levels at the two locations were markedly different and require separate discussion. The positive correlation (p<.05) between temperature and primary production at Yellow Island (Table 9) suggests that phytoplankton production may have been temperature-limited in this area. Low surface temperatures never exceeding 11.6 C over the course of the summer reinforce this hypothesis (Table 3). If this information i s coupled with the high nitrate concentrations (15 uM) measured in late June at Yellow Island (Fig. 8) during a time when they should be at a seasonal low (Seki et al., 1987 and 1984), i t would seem unlikely that any ammonium enrichment associated with the farm would result in higher levels of primary production. The increased photosynthetic rates observed during late June and mid-August (Fig. 9A) in the v i c i n i t y of 78 the pens do not support this hypothesis. When the true carbon uptake i s derived by dividing photosynthetic rates by chlorophyll a levels , however, no spatial trends in primary production ( i . e . productivity indices) are observed (Fig. 10A). As we shall see later , the lack of any enhancement in carbon uptake rates in the v i c i n i t y of the farms may also have been related to methodological time scale errors. Temperature and nitrate conditions were considerably different at Quartz Bay compared to Yellow Island. Surface temperatures at Quartz Bay over the course of the summer (Table 4) were much higher than those observed at Yellow Island. No positive correlations between temperature and photosynthetic rates or productivity indices were noted (Table 10) suggesting that temperature was not a growth-l imit ing factor at Quartz Bay. Coupled with the low nitrate levels at a l l stations (2.0-3.0 uM) observed in early July (Fig. 8), an enhancement of primary production in the v i c i n i t y of the farm at Quartz Bay would be possible. A noticeable increase in photosynthetic rates at a l l stations and higher rates at the inner stations were observed during the August sampling period (Fig. 9B) . The higher photosynthetic rates undoubtedly resulted from elevated chlorophyll a levels during this period as proven by the strong correlation (p<.01) between these two variables at Quartz Bay (Table 10). The productivity indices which are a more accurate reflection of true ce l lu lar carbon uptake 79 rates showed no spatial trends between stations during this time period (Fig 10B). Increased chlorophyll a concentrations at the inner two stations were observed in late June at Yellow Island (Fig. 4B) and early July and mid-August at Quartz Bay (Fig. 7B). Oddly, no increases in the primary productivity indices at these stations were noted during these sampling periods (Fig. 10). The explanation for this paradox l i es in the d i f f i cu l ty of interpreting in s i tu measurements of carbon uptake with regard to enhanced community growth rates or elevated phytoplankton biomass. According to Harris (1988), the lack of any increase in carbon uptake following the exposure of phytoplankton to pulses of dissolved inorganic nitrogen (DIN) simply reflects the present state of the internal storage pool of DIN. Following exposure to high levels of ammonium, ce l l s with depleted internal DIN pools would not be expected to show increases in carbon uptake u n t i l many hours after the exposure because the time scale for nutrient uptake and metabolism ( i . e . carbon uptake) i s in the order of hours. The time scale for ce l l s to be transported from Station 0 to Station 3 i s , however, in the order of minutes. It would be unreasonable, therefore, to expect to see a decrease in carbon uptake at Station 3 compared to the rate measured at Station 0 within minutes after the ce l l s had been exposed to high levels of tota l ammonia. The replete internal storage pools of DIN within the ce l l s would be sufficient to maintain high levels 80 of carbon uptake for many hours (Harris, 1988). In order to detect enhanced photosynthetic rates resulting from fish farm ammonium loading, one would have to measure in situ carbon uptake before and after the exposure of phytoplankton to the elevated ammonium levels associated with the culture f a c i l i t y . The paradox between the enhanced levels of chlorophyll a and constant P/B ratios i s a result of employing too short a time scale to measure changes in metabolic processes which ultimately lead to changes in phytoplankton biomass. Because the degree of correlation between nitrogen l imitat ion and P/B ratios in natural systems i s often poor (Turpin, 1983), i t would be very d i f f i c u l t to determine i f elevated phytoplankton biomass levels in the v i c i n i t y of a culture operation are resulting from high ammonium concentrations, no matter what sampling stategy was employed. The small increases in chlorophyll a levels observed at the inner two stations at both locations during specific sampling periods could have resulted as a consequence of three possible mechanisms, including: 1) Increases in growth rates of nitrogen-limited phytoplankton entering waters containing high ammonium levels as a result of f ish farming act iv i ty ; 2) Retention of phytoplankton in the immediate v i c i n i t y of the farms through the formation of eddies and gyres created as currents flow through the pens and rafts of the culture f a c i l i t i e s ; 3) Disengagement of benthic algae growing on the nets and floats of the f ish farm. 81 The elevated chlorophyll a concentration observed at Station ,0 at Yellow Island during the late June sampling period was at least par t ia l ly caused by mechanism 3. This i s supported by the large proportion of benthic diatom species observed during this time period. The percentage of benthic diatoms at Quartz Bay was also highest during the f i r s t sampling period; however, this group made up a much smaller proportion of the tota l biomass. Thus disengagement of fouling algae at Quartz Bay did not contribute s ignif icantly to the elevated chlorophyll a levels observed at Station 0 during early July and mid-August. If the tota l ammonia levels measured at Stations 2 and 3 during periods when minor chlorophyll a enrichment was observed are representative of background levels in Quartz Bay ( i . e . 1-3 uM NH^-N) during this time, i t seems unlikely that higher levels of ammonium in the near v i c i n i t y of the farm would result in elevated chlorophyll a c o n c e n t r a t i o n s B y elimination of the f i r s t and th ird hypotheses, the minor increases in phytoplankton biomass in the v ic inty of the pens at Quartz Bay probably resulted from the formation of retentive gyres produced by currents flowing past the culture f a c i l i t y . 82 The length of time for a change in phytoplankton community structure to occur due to changes in nutrient levels i s many times greater than the time scale of algal metabolic processes. Thus i t i s not surprising that no spatial patterns of species dominance emerge between the inner and outer stations (Fig. 11) due to any existing gradients in tota l ammonia levels . The species composition data do shed some l ight on the importance of seasonal changes occurring in the water column. At both Yellow Island and Quartz Bay, the percentage of f lagellates and c i l i a t e s was highest during the f i r s t sampling periods in late June/early July. The community shift at Yellow Island from 85 to almost 100% diatom dominance in the August and September sampling periods may ref lect increasing ambient nutrient levels favoring larger ce l l s with higher nitrogen uptake rates (Parsons et al., 1977). At Quartz Bay, the increase in .diatom abundance was more dramatic, with abundances changing from 9% in early July to roughly 95% in the last two sampling periods. The higher productivity indices seen in the lat ter two sampling periods at Quartz Bay (Fig. 10B) may, in part, have resulted from this marked composition shi f t . Dissolved organic carbon absorbances ( i . e . 280 nm absorbances) were quite low at both locations. The absorbance values observed over the course of the summer at both locations are approximately equivalent to 0.5 mg C*1~A 83 (T.R. Parsons, Pers. comm.). DOC absorbance at the outer two stations of Yellow Island (Table 8) was s ignif icantly higher (p<.05) than at the inner stations. Because the absorbance levels were so low i t must be realized that the spatial trend seen at Yellow Island i s occurring over a very small range of values. It i s d i f f i c u l t , therefore, to determine i f this pattern i s a reflection of a significant negative influence of the farm on DOC levels in the immediate v i c i n i t y , or simply a measure of small scale patchiness. Bacterial numbers in the surface waters at Yellow Island and Quartz Bay did not vary with respect to distance from the farms. If the low absorbance values (280 nm) are representative of the amount of available protein, i t i s not surprising that no elevation in bacterial numbers was observed in the v i c in i ty of the farms. Bacterial concentrations did not decline in any of the pens in which ant ibiot ic treatments were being administered suggesting an adequate di lut ion of any antibiot ic leaching from the feed during set t l ing . The larger numbers of bacteria at Quartz Bay compared to Yellow Island are probably the result of higher water temperatures as suggested by the positive correlation between bacteria and surface temperature (p<.01) seen at Quartz Bay (Table 10). Bacterial levels at both locations appear to be controlled by seasonal changes in the water column and not by f ish farm by-products. 84 The main objective of this study was to determine i f salmon farms in the Discovery Passage area are increasing levels of phyto- and bacterioplankton due to ammonium and/or carbon loading. This investigation has shown that salmon farms in this area can elevate levels of phytoplankton biomass in the immediate v i c i n i t y of the farms but only to a very l imited extent. In terms of the production measures investigated, any influence of the farms appears to be lost within a very short distance (ca. 10 m) from the pens. If the sites examined in this study are at a l l representative of the majority of culture f a c i l i t i e s in this region, a decline in water quality through elevations in phytoplankton levels resulting from fish farming act iv i t i e s seems highly unlikely in the Discovery Passage area. The magnitude and v a r i a b i l i t y of any increases in tota l ammonia levels have been shown to be closely related to the flushing characteristics of the location as well as seasonal changes in the s tab i l i ty and nutrient ava i lab i l i ty of the surrounding water. Given the limited size of the sampling program employed, these conclusions should be viewed as preliminary in nature. The v a r i a b i l i t y in any enriching effects of culture operations on marine water quality should nonetheless be an important consideration in the design and implementation of any upcoming monitoring requirements. 85 VI. REFERENCES Anonymous. 1988. Canadian Tide and Current Tables. Vo l . 6. Barkley Sound and Discovery Passage to Dixon Entrance. Department of Fisheries and Oceans, information and publications branch. Arakawa, K.Y. 1973. Aspects of eutrophication in Hiroshima Bay viewed from transit ion of cultured oyster production and succession of marine b iot ic communities. Nihon Kaiyo Gakkai-Shi 11: 43-48. Arizono, M. 1979. Disease control in mariculture, with special reference to yel lowtail culture. In G. Yamomoto (ed.), Proc. Seventh Japan-Soviet Joint Symposium on Aquaculture, September, 1978, Tokyo and Tsuruga, Japan., Tokai University. pp. 79-88. Austin, B. 1975. Antibiot ic pollution from f ish farms: effects on aquatic microflora. Microbiol. Sci. 2: 113-117. Azam, F . , T. Fenchel, J . G . F i e l d , J . S . Gray, L . A . Meyer-Reil and F . Thingstad. 1983. The ecological role of water-column microbes in the sea. Mar. Ecol. Prog. Ser. 10: 257-263. Bergheim, A. and A.R. Selmer-Olsen. 1978. River pollution from a large trout farm in Norway. Aquaculture 14: 267-270. Black, E .A . and B . L . Carswell. 1986. The impact of salmon farming on marine water quality. Fisheries Development Paper No. 11 (draft). Buckley, J .R. and S. Pond. 1976. Wind and the surface c irculat ion of a fjord. J". Fish. Res. Bd. Canada. 33: 2265-2271. Cochlan, W.P., P . J . Harrison, P.A. Thompson and T.R. Parsons. 1986. Preliminary observations of the summer production of three Br i t i sh Columbia coastal in le ts . Sarsia 71: 161-168. Eloranta, P. and A. Palomaki. 1986. Phytoplankton in Lake Konnevesi with special reference to eutrophication of the lake by f ish farming. Agua Fenn. 16: 37-45. Ennel l , M. and J . Lof. 1983. Environmental impact of aquaculture-sedimentation and nutrient loading from f ish cage culture farming. Vatten 39: 364-375. 86 Ervik, A . , P. Johannessen and J . Aure. 1985. Environmental effects of marine Norwegian Fish Farms: International Council for the Exploration of the Sea C M . 1985/F:37. 13 p. Fribourgh, J . H . , F .P . Meyer and J . A . Robinson. 1969. Oxytetracycline leaching from medicated f ish feed. U.S. Bur. Sport Fish Tech. Pap. 40. 7 pp. Gowen, R . J . , and N.B. Bradbury. 1987. The ecological impact of salmonid farming in coastal waters: A review. Oceanogr. Mar. Biol. Ann. Rev. 3: 563-575. H a l l , P. and 0. Holby. 1986. Environmental impact of marine f ish cage culture. International Council for the Exploration of the Sea C M . 1986/F:46. 19 p. Harris , G.P. 1988. Phytoplankton Ecology: Structure, Function and Fluctuation. Chapman and H a l l , New York. 384 p. Inoue, H. 1972. On water exchange in a net cage stocked with the f i sh , Hamachi. Bull. Japanese Soc. Sci. Fish. 38: 167-176. Jacobsen, P. and L . Berglind. 1988. Persistence of oxytetracycline in sediments from f ish farms. Aquaculture 70: 365-370. Kadowaki, S. , T. Kasedo and T. Nakazano. 1978. Continuous records of DO contents by cruising in the coastal culture f ish farms. I . Relation between DO content and f ish density in cages. Mem. Fac. Fish., Kagoshima University 27: 273-280. Kaspar, H . F . , G.H. Hall and A . J . Holland. 1988. Effects of sea cage salmon farming on sediment n i t r i f i c a t i o n and dissimilatory nitrate reductions. Aquaculture 70: 333-344. Krom, M.D. and E.R. Sholkovitz. 1977. Nature and reactions of dissolved organic matter in the i n t e r s t i t i a l waters of marine sediments. Geochim. Cosmochim. Acta. 41: 1565-1573. Larsson, U. and A. Hagstrom. 1982. Fractionated phytoplankton primary production, exudate release and bacterial production in a Balt ic eutrophication gradient. Mar. Biol. 67:57-70. Liao, P.B. and R.D. Mayo. 1974. Intensified f ish culture combining water reconditioning with pollution abatement. Aquaculture 3: 61-85. 87 Lorenzen, C . J . 1963. Diurnal variation in photosynthetic act iv i ty of natural phytoplankton populations. Limno. Oceanogr. 8: 56-62. Marvin, K . T . and R.R. Proctor. 1965. Stabi l iz ing the ammonia-nitrogen content of estuarine and coastal waters by freezing. Limno. and Oceanogr. 10: 288-289. Newell, B.S. 1967. The determination of ammonium in sea water. J. Mar. Biol. Ass. U.K. 47: 271-280. Nishimura, A. 1982. Effects of organic matter produced in f ish farms on the growth of redtide algae. Bull Plankton. Soc. Japan. 29: 1-7. Paasche. E . 1988. Pelagic primary production in nearshore waters. In: T .H. Blackburn and J . Sorensen (eds.) Nitrogen Cycling in Coastal Marine Environments. John Wiley & Sons, New York. pp. 33-57. Parsons, T . R . , B . E . Rokeby, C.M. L a l l i , and C D . Levings 1989. Experiments on the effect of salmon farm wastes on plankton ecology (draft). Parsons, T . R . , D.G. Webb, H. Dovey, R. Haigh, M. Lawrence and G.E. Hopky. 1988. Production studies in the Mackenzie River-Beaufort Sea Estuary. Polar Biol.B: 235-239. Parsons, T . R . , Y. Maita and C.M. L a l l i . 1984. A manual of chemical and biological methods for seawater analysis. Pergamon Press, Oxford, 173 p. Parsons, T . R . , M. Takahashi and B. Hargrave. 1977. Biological oceanographic processes. 2 edit ion. Pergamon Press, Oxford, 332 p. Pease, B .C. 1977. The effect of organic enrichment from a salmon mariculture f a c i l i t y on the water quality and benthic community of Henderson Inlet, Washington. Ph.D. thesis, University of Washington, Seattle, Washington. Pond, S. and G.L . PicJcard. 1983. Introductory dynamical oceanography. 2 n d edit ion. Pergamon Press, Oxford, 329 p. Rosenthal, H . , D. Weston, R. Gowen and E . Black. 1988. Report of the ad hoc study group on "Environmental Impact of Mariculture". International Council for the Exploration of the Sea. Cooperative Research Report No. 154. 83 p. 88 Ruokolahti, C. 1988. Effects of f ish farming on growth and chlorophyll a content of Cladophera. Mar. Poll. Bull. 19: 166-169. Seki, H . , A. Otsuki, Y. Hara, K.V. Stephens, C D . Levings and C D . McAll ister . 1987. Dynamics of organic materials in the Campbell River estuary at the time of the spring bloom of phytoplankton. Arch. Hydrobiol. I l l : 209-216. Seki, H . , A. Otsuki, S. Daigobo, C D . Levings and C D . McAll i s ter . 1984. Microbial contribution to the mesotrophic ecosystem of the Campbell River estuary during summer. Arch. Hydrobiol. 102: 215-228. Slawyk, G. and J . J . Maclsaac. 1972. Comparison of two automated ammonium methods in a region of coastal upwelling. Deep Sea Res. 19: 521-524. Sokal, R.R. and F . J . Rohlf. 1981. Biometry. 2 n d edit ion. Freeman Press, New York, 859 p. Storch, T .A . and G.W. Saunders. 1978. Phytoplankton extracellular release and i t s relat ion to the seasonal cycle in a eutrophic lake. Limnol. Oceanogr. 23: 112-119. Thompson, R .E . 1981. Oceanography of the Br i t i sh Columbia coast. Can. Spec. Publ. Fish. Aquat. Sci. 56. 291 p. Tucker, C . S . , S.W. Lloyd and R . L . Busch. 1984. Relationships between phytoplankton periodicity and the concentration of tota l and unionized ammonia in channel catf ish ponds. Hydrobiologia III: 75-79. Turpin, D.H. 1983. Ammonium induced photosynthetic suppression in ammonium limited Dunaliella tertiolecta (Chlorophyta). J. Phycol. 19: 70-76. Weston, D.P. 1986. The environmental effects of floating mariculture in Puget Sound. Wash. Dept. F ish , and Wash. Dept. Eco l . 148 p. Wood, E . D . , F . A . J . Armstrong and F .A . Richards. 1967. Determination of nitrate in seawater by cadmium-copper reduction to n i t r i t e . J". Mar. Biol. Ass. U.K. 47: 23-31. 89 VII. APPENDICES. APPENDIX I THE EFFECT OF FREEZING ON THE VARIABILITY OF TOTAL AMMONIA DETERMINATIONS. The magnitude of the effects of freezing on ammonium determinations i s dependent on the concentration of tota l ammonia in the sample. At low concentrations typical of oceanic conditions (0.005-0.05 uM), freezing has been shown to cause substantial increases in the v a r i a b i l i t y of determinations beyond that expected from measurement errors (Newell, 1967). At higher ammonium levels typical of coastal and estuarine environments (0.1-1.0 uM), freezing does not appear to cause significant changes in the v a r i a b i l i t y of determinations (Marvin and Proctor, 1965). The high tota l ammonia concentrations measured in this study warrant the use of freezing as an adequate preservation technique. To evaluate the effects of freezing on ammonium determinations made in this study, one 30 ml sample containing 1.5 uM NH4C1 prepared in 3% NaCl was frozen along with every dai ly set of nutrient samples. The results shown in Figure 16 suggest that freezing led to a 7% increase in tota l ammonia concentrations. The v a r i a b i l i t y in the standard frozen determinations (coefficient of variation = 21%) also appears to be elevated beyond that expected from measurement error (coefficient of variation = 1.5%). The magnitude of the v a r i a b i l i t y 90 attributed to freezing i s not, however, great enough to result in the very large differences in tota l ammonia levels seen between the inner and outer station groupings during some of the sampling periods. The ammonium data therefore reflects real differences in concentrations at various distances from the pens, although the absolute ammonium values may be somewhat elevated due to the effects of freezing. 91 Figure 16. The effects of freezing on ammonium determinations. The dashed l ine represents the concentration of the standard solution ( N H 4 C I ) before freezing. c o c <1> o c o o E _5 "c o E E < 5.00 4 .00 3 . 0 0 -2 .00 1.00-0 .00 THE EFFECT OF FREEZING ON THE VARIABILITY OF AMMONIUM DETERMINATIONS USING A 1.5 LiM AMMONIUM CHLORIDE STANDARD. Mean value: 1.60 jM Standard dev iat ion: 0 .33 [M : pre—freeze concen t ra t i on (1.5/uM) O O O O O 0 O O JULY AUGUST _j —1. . 1 1 SEPTEMBER i i i t 1 2 3 4 5 6 7 8 FREEZING DATE AND SAMPLE NUMBER A P P E N D I X I I PHYTOPLANKTON SPECIES OBSERVED AT YELLOW ISLAND AND QUARTZ BAY. Table 12 on the following pages contains a l l of the species observed in this study. Their presence at Yellow Island or Quartz Bay are denoted by the symbols Y and Q, respectively. Class: Baci = Bacillariophyceae C i l i = Ciliophora (Phylum) Cryp = Cryptomonads Dino = Dinophyceae Eugl = Euglenophyceae Raph = Raphidophyceae S i l i = Silicophyceae P/H = photosynthetic or heterotrophic. 93 Table 12. Organisms observed at Yellow Island and Quartz Bay, summer '88. ORGANISM OBSERVED LOCATION CLASS P/H Actinoptychus undulatus Qr Y Baci P Alexandrium ostenfeldii Qr Y Dino P Amphidinium sphenoides Q, Y Dino H Asterionella g lac ia l i s Qr Y Baci P Ceratium fusus Q, Y Dino P Ceratium longipes Y Dino P Cerataulina pelagica Qr Y Baci P Chaetoceros affine Qr Y Baci P Chaetoceros convolutum Qr Y Baci P Chaetoceros compressum Qr Y Baci P Chaetoceros constrictum Qr Y Baci P Chaetoceros danicum Qr Y Baci P Chaetoceros debile Qr Y Baci P Chaetoceros decipiens Qr Y Baci P Chaetoceros spp. Qr Y Baci P Chaetoceros laciniosum Qr Y Baci P Chaetoceros pseudocrinitum Y Baci P Chaetoceros radicans Qr Y Baci P Chaetoceros sociale Q, Y Baci P Corethron criophilum Q Baci P Coscinodiscus spp. Qr Y Baci P Coscinodiscus grani i Y Baci P Coscinodiscus radiatus Qr Y Baci P Coscinodiscus t h o r i i Q Baci P Cryptomonads Qr Y Cryp P Cylindrotheca closterium Qr Y Baci P Detonula pumila Qr Y Baci P Dictyocha speculum Qr Y S i l i P Dinophysis infundibulum Q Dino P Dinophysis lachmannii Y Dino P Dinophysis norvegica Q, Y Dino P Dinophysis ovum Qr Y Dino P Dinophysis rotundata Q, Y Dino H Diplopsaloids Q, Y Dino H Ditylum brightwel l i i Qr Y Baci P Ebria t r i p a r t i t a Y S i l i H Eucampia zoodiacus Q, Y Baci P Eutrept ie l la sp. Q, Y Eugl P Frag i lar ia spp. Q, Y Baci P Gonyaulax spinifera Q, Y Dino P Grammatophora marina Y Baci P Gymnodinium sanguineum Qr Y Dino P Gyrodinium glaucum Qr Y Dino H Gyrodinium spirale Q, Y Dino H Heterosigma akashiwo Qr Y Raph P Heterocapsa triquetra Qr Y Dino P Leptocylindrus danicus Qr Y Baci P 94 Table 12 con't. ORGANISM OBSERVED LOCATION CLASS P/H Leptocylindrus minimus Qr Y Baci P Licmophora spp. Qr Y Baci P Melosira moniliformis Qr Y Baci P Mesodinium rubrum Qr Y C i l i P Navicula spp. Qr Y Baci P Nitzschia delicatissima Qr Y Baci P Nitzschia pungens Qr Y Baci P Nitzschia seriata Y Baci P Nitzschia spp. Qr Y Baci P Noctiluca sc int i l lans Qr Y Dino H Odontella aurita Qr Y Baci P Odontella longicruris Y Baci P Oxyphysis oxytoxoides Y Dino P Paralia sulcata Qr Y Baci P Pleurosigma/Gyrosigma Qr Y Baci P Polykrikos kofo id i i Qr Y Dino H Protoperidinium acutum Y Dino H Protoperidinium bipes Y Dino H Protogonyaulax catenella Qr Y Dino H Protoperidinium conicum Qr Y Dino H Protoperidinium denticulatum Q Dino H Protoperidinium depressum Qr Y Dino H Protoperidinium excentricum Qr Y Dino H Protoperidinium furcatum Qr Y Dino H Prorocentrum gracile Qr Y Dino H Protoperidinium grani i Y Dino H Protoperidinium pallidum Qr Y Dino H Protoperidinium pellucidum Qr Y Dino H Protoperidinium pentagonum Qr Y Dino H Protoperidinium subcurvipes Q Dino H Protoperidinium subinerme Qr Y Dino H Protoperidinium spp. Qr Y Dino H Rhizosolenia fragil issima Qr Y Baci P Rhizosolenia setigera Qr Y Baci P Scrippsie l la trochoidea Qr Y Dino P Skeletonema costatum Qr Y Baci P Stephanopyxis turr i s Q Baci P Thalassiosira aest ival is Qr Y Baci P Thalassiosira angsti i Qr Y Baci P Thalassiosira anguste-lineata Qr Y Baci P Thalassiosira eccentricus Qr Y Baci P Thalassiothrix frauenfeldii Qr Y Baci P Thalassionema nitzschioides Qr Y Baci P Thalassiosira rotula Qr Y Baci P Tropidoneis lepidoptera Y Baci P 

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