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The fate of aquatic macrophyte production : the decomposition, mineralization and nutrient recycling… Kistritz, Ron Udo 1975

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THE FATE OF AQUATIC MACROPHYTE PRODUCTION: THE DECOMPOSITION, MINERALIZATION AND NUTRIENT RECYCLING OF A SUBMERGED AQUATIC VASCULAR PLANT (MYRIOPHYLLUM SPP.) by RON UDO KISTRITZ B . S c , U n i v e r s i t y of Toronto, 1973 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of Zoology We accept t h i s t h e s i s as conforming t o the re q u i r e d standard TTlE UNIVERSITY OF BRITISH COLUMBIA June, 1975 In present ing th is thesis i n - p a r t i a l fu l f i lment o f the requirements for an advanced degree at the Un ivers i ty of B r i t i s h Columbia, I agree that the L ibrary sha l l make i t f r ee ly ava i l ab le for reference and study. I fur ther agree that permission for extensive copying o f th is thes is for s c h o l a r l y purposes may be granted by the Head of my Department or by his representa t ives . It is understood that copying or pub Ii cat i • of th is thes is for f i n a n c i a l gain sha l l not be allowed without my writ ten pe rm i ss i on . i o n Department of The Univers i ty of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date l y t u t a 7*1 r V i i ABSTRACT Decomposition, mineralization and phosphorus (P) and nitrogen CN). regeneration of a submerged aquatic macrophyte, water~mili;oil (Myriophyllum spp.), were investigated both i n laboratory and f i e l d experiments. Ex i s t i n g chemical methods of plant analysis were modified to provide a procedure which simultaneously measured N and P i n one small sample of l i v e or dead plant material. A laboratory experiment was designed to investigate the e f f e c t of nutrient r i c h reservoir water and nutrient poor pond water on the process of aerobic decomposition and nutrient regeneration i n w a t e r - m i l f o i l . Measurements were also made of dry weight, and nutrient content of dying macrophyte mater-i a l and three size catagories of macrophyte d e t r i t u s . In the laboratory, higher amounts of N i n reservoir water s i g n i f i c a n t l y increased decomposition and N and P regeneration of macrophyte material. Dying macrophytes and detritus showed 25-40 percent increases i n t o t a l protein due to colonizing decomposer microorganisms. An " i n s i t u " f i e l d study was designed to investigate the regeneration and mineralization of N and P compounds of aqua-t i c macrophytes CMyriophyHum spicatum L.) decomposing under p e r i o d i c a l l y anaerobic condition i n nutrient r i c h reservoir water. Measurements were related to levels of N and P compounds libe r a t e d by sediment and decaying algae (almost e n t i r e l y Anabaena spirula) and to N and P represented by t o t a l suspended bacteria. I t was estimated that suspended b a c t e r i a contained up to 31 and 21 percent of the water's t o t a l organic P and N, respectively. Both laboratory and f i e l d results showed that P was regen-erated rapi d l y and almost e n t i r e l y as orthophosphate. Nitrogen was released predominately as ammonia, appreciable amounts of which were also l i b e r a t e d by sediment and phytoplankton. i v TABLE OF CONTENTS Page ABSTRACT i i L I S T OF TABLES v i L I S T OF FIGURES v i i i L I S T OF ABBREVIATIONS . . x i ACKNOWLEDGMENTS . . . . x i i I INTRODUCTION 1 I I STUDY S I T E S 10 I I I METHODS AND MATERIALS 1. L a b o r a t o r y E x p e r i m e n t „ . 22 1.1 P r e p a r a t i o n o f m a t e r i a l a n d e x p e r i m e n t a l d e s i g n .... 22 1.2 S a m p l i n g p r o c e d u r e 23 1.3 C h e m i c a l a n a l y s i s o f p l a n t m a t e r i a l 27 1.4 C h e m i c a l a n a l y s i s o f w a t e r ....... 28 2. F i e l d E x p e r i m e n t 29 2.1 E x p e r i m e n t a l d e s i g n 29 2.2 C o n c e p t s , h y p o t h e s e s a n d a s s u m p t i o n s 3 2 2.3 S a m p l i n g p r o c e d u r e 36, 2.4 B a c t e r i a l a n a l y s i s 39 2.5 S e d i m e n t c h e m i s t r y . 41 I V RESULTS AND DISCUSSION 1. L a b o r a t o r y E x p e r i m e n t 42 1.1 I n i t i a l n u t r i e n t c o n t e n t o f a q u a t i c p l a n t s and w a t e r 4 2 1.2 D e g r a d a t i o n o f a q u a t i c p l a n t m a t e r i a l 4 7 1.3 C h e m i c a l c h a r a c t e r i s t i c s a n d amount o f d e t r i t a l f r a c t i o n s 54 1.4 R e g e n e r a t i o n a n d m i n e r a l i z a t i o n o f p l a n t n i t r o g e n a n d p h o s p h o r u s 63 2. F i e l d E x p e r i m e n t 7 2 2.1 I n i t i a l n u t r i e n t c o n t e n t a n d c h a r a c t e r i s t i c s 72 2.1.1 M y r i o p h y l l u m s p i c a t u m . . . 72 2.1.2 R e s e r v o i r w a t e r a n d b i o t a 7 6 2.1.3 R e s e r v o i r s e d i m e n t 81 2.2 T e m p e r a t u r e , pH a n d d i s s o l v e d O2 2.3 T o t a l a l k a l i n i t y 83 85 V 2.4 Regenerated n i t r o g e n . . . . . 9 0 . 2 . 4 . 1 Ammonia 90 2.4.2 T o t a l K j e l d a h l and o r g a n i c n i t r o g e n . .. 97 2.5 Regenerated phosphorus.. 104 2.5.1 Orthophosphate •'. 104 2.5.2 T o t a l and o r g a n i c phosphorus 110 2. 6 B a c t e r i a . .". 115 2.6.1 General c h a r a c t e r i s t i c s . . . . 115 2.6.2 N i t r o g e n and phosphorus removed by suspended b a c t e r i a . 120 V SUMMARY AND CONCLUSION 125 VI LITERATURE CITED 130 VII APPENDIX 1 3 7 A. Simultaneous A n a l y s i s o f T o t a l N i t r o g e n and Phosphorus i n A q u a t i c Macrophyte T i s s u e 138 v i LIST OF TABLES Ta b l e Page I , V a r i a b i l i t y i n N and P t i s s u e c o n t e n t s o f v M y r i o p h y l l u m t i s s u e i n t r o d u c e d t o system o f c o n t a i n e r s , .. . . . 43 I I , . C h a r a c t e r i s t i c , p e r d r y w e i g h t , o f My riophy11urn a t i n i t i a l e x p e r i m e n t a l c o n d i t i o n s , (August 1974) 45 I I I , Range o f N and P t i s s u e c o n t e n t s o f M y r i o p h y H u m spp. r e p o r t e d i n t h e l i t e r a t u r e . . 46 IV. R e l a t i v e d i s t r i b u t i o n o f v a r i o u s d c t r i t a l f r a c t i o n s i n system o f c o n t a i n e r s d u r i n g c o u r s e o f experiment... 55 V. Changes i n n u t r i e n t q u a l i t y o f d e t r i t a l f r a c t i o n s g r e a t e r than 1 mm i n : (a) Cedar V a l l e y system and (b) Iona R e s e r v o i r system 57 2 V I . R e p l i c a t e samples o f h m s t a n d i n g c r o p o f M y r i o p h y l l u m h a r v e s t e d a d j a c e n t t o e x p e r i m e n t a l e n c l o s u r e s . .... 7 3 V I I . Average n u t r i e n t c o n t e n t o f M y r i o p h y l l u m e n c l o s e d i n e x p e r i m e n t a l c y l i n d e r s 75 V I I I . Q u a l i t y o f r e s e r v o i r w a t e r e n c l o s e d by e x p e r i -m e n t a l c y l i n d e r s on October 1, 1974, compared t o d a t a o f August 6, 1974,... 7 7 IX. T o t a l amount of N and P t i e d up i n v a r i o u s components w i t h i n water column of e n c l o s u r e s a t s t a r t i n g c o n d i t i o n 7 9 X. C h e m i c a l c o m p o s i t i o n o f r e s e r v o i r s u r f a c e sediment a d j a c e n t t o s t u d y s i t e . . 82 X I . Changes i n t e m p e r a t u r e , pH, and d i s s o l v e d oxygen i n s i d e and o u t s i d e o f e n c l o s u r e s d u r i n g c o u r s e o f experiment.. 84 X I I . Changes i n t o t a l a l k a l i n i t y c o n t e n t of water i n s i d e and o u t s i d e o f e n c l o s u r e s d u r i n g c o u r s e o f e x p e r i m e n t , 8 6 V l l T a b l e Page X I I I , Changes i n N i t r a t e and N i t r i t e c o n t e n t o f wa t e r i n s i d e and o u t s i d e o f e n c l o s u r e s during c o u r s e o f e x p e r i m e n t , . . . . 92 XIV, Average p r o d u c t i o n r a t e s o f r e g e n e r a t e d ammonia from m a j o r s o u r c e s i n the e n c l o s u r e s . 95 XV, Average p r o d u c t i o n r a t e s o f r e g e n e r a t e d phos^ phate from m ajor s o u r c e s i n the e n c l o s u r e s . . . 107 XVI, Range of r e s u l t s o f t o t a l b a c t e r i a c o u n t s i n t h i s s t u d y compared t o r e s u l t s found i n the l i t e r a t u r e where f l u o r e s c e n t , d i r e c t c o u n t i n g t e c h n i q u e s were used 117 XVTI. Average t o t a l suspended b a c t e r i a c o u n t s j>n number o f ' c e l l s / m l X 10 ±10 p e r c e n t , i n s i d e and o u t s i d e o f e n c l o s u r e s d u r i n g c o u r s e o f experiment 121 X V I I I . T o t a l amount o f N and P t i e d up i n suspended b a c t e r i a ; a l s o e x p r e s s e d as a p e r c e n t a g e r e l a t i v e t o t o t a l o r g a n i c N and P i n water o f e n c l o s u r e s 123 XIX. Comparison o f P t i s s u e c o n c e n t r a t i o n s i n M y r i o p h y l l u m u s i n g : (a) S t a n d a r d wet a s h i n g o r (b) K j e l d a h l d i g e s t i o n 140 v i i i LIST OF FIGURES F i g u r e Page 1. The f a t e o f macrophyte n e t p r i m a r y p r o d u c t i o n and the pathways a l o n g w h i c h m a t t e r and energy i s t r a n s p o r t e d 3 2. Maps showing l o c a t i o n o f Iona r e s e r v o i r and Cedar V a l l e y pond ( i n s e r t map). .... 11 3. A e r i a l v i e w o f Iona I s l a n d w i t h arrow i n d i c a t i n g r e s e r v o i r . T i d a l f l a t s a r e i n f o r e g r o u n d and N o r t h Arm o f F r a s e r R i v e r i s seen from m i d d l e l e f t t o t o p r i g h t 13 4a. Iona r e s e r v o i r : s t i p p l e d appearance o f w a t e r s u r f a c e i s caused by emerging t i p s o f M. s p i c a t u m (water m i l f o i l 14 4b, C l o s e up o f w a t e r m i l f o i l g rowing i n Iona r e s e r v o i r . . . . . 14 5a. Sampling from e x p e r i m e n t a l f i e l d e n c l o s u r e s , Iona r e s e r v o i r . . . . 16 5b, Appearance o f f o u r e x p e r i m e n t a l f i e l d e n c l o s u r e s i n t h e Iona r e s e r v o i r 16 6a.. Cedar V a l l e y Pond showing submerged a q u a t i c m i l f o i l . . . . . 18 6b. Submerged a q u a t i c m i l f o i l i n Cedar V a l l e y Pond..... 18 7. C l o s e up o f M. h i p p u r o i d e s ( a q u a t i c m i l f o i l ) l y i n g i n s h a l l o w w a t e r o f Cedar V a l l e y Pond 19 8a. Mounted voucher specimen o f M y r i o p h y l l u m s p i c a t u m L. from Iona R e s e r v o i r . . , 2 0 8b. Voucher specimen of M y r i o p h y l l u m h i p p u r o i d e s N u t t . from Cedar V a l l e y Pond.. 21 9. E x p e r i m e n t a l d e s i g n o f l a b o r a t o r y c o n t a i n e r s showing s a m p l i n g d e s i g n and d e t a i l s o f c o n t a i n e r s 24 10. Flow c h a r t showing p r o c e d u r e used a f t e r a l a b o r a t o r y c o n t a i n e r was emptied 26 11. Example o f e x p e r i m e n t a l f i e l d e n c l o s u r e w i t h s o l i d bottom 30 ix F i g u r e Page 12. E x p e r i m e n t a l d e s i g n o f e n c l o s u r e s showing com-b i n a t i o n s o f a q u a t i c macrophytes and r e s e r v o i r sediment.. 31 13. Concept of N and P r e g e n e r a t i o n , c y c l i n g and ad-s o r p t i o n , (shown by arrows), o f v a r i o u s s o u r c e s and components w i t h i n t h e e x p e r i m e n t a l f i e l d e n c l o s u r e . . . . . . 33 14. E x p e c t e d and h y p o t h e s i z e d r e s u l t s o f e n c l o s u r e s combined i n f o u r d i f f e r e n t ways t o show r e g e n e r a t i o n o f n u t r i e n t s (N and P) due t o p l a n t , a l g a e and s e d i m e n t . . . . 3 7 15. View i n s i d e l a b o r a t o r y c o n t a i n e r showing appearance o f macrophyte a f t e r 13 days i n d a r k n e s s . These p l a n t s were o n l y 28% o f t h e i r o r i g i n a l d r y w e i g h t . . 48 16. Mass b a l a n c e d i s t r i b u t i o n o f v a r i o u s d e t r i t a l f r a c t i o n s i n t h e two systems of c o n t a i n e r s d u r i n g c o u r s e o f e x p e r i m e n t . The n e t b a l a n c e i s shown as DOM t o a ccount f o r t h e t o t a l p l a n t m a t t e r o r i g i n a l l y i n t r o -duced i n t o t h e system 50 17. P e r c e n t change i n n u t r i e n t c o n t e n t o f decomposing p l a n t m a t e r i a l g r e a t e r t h a n 1 mm r e l a t i v e t o l e v e l s o f o r i g i n a l l i v e p l a n t s . . . . . 59 18. Changes i n phosphorus c o n t e n t o f water d u r i n g , c o u r s e o f e x p e r i m e n t . , 64 19. Changes i n n i t r o g e n c o n t e n t o f water d u r i n g c o u r s e o f e x p e r i m e n t 68 20. P r o p o r t i o n o f N and P t i e d up i n v a r i o u s components w i t h i n w a t e r column o f e n c l o s u r e s a t s t a r t i n g c o n d i t i o n s 80 21. T o t a l a l k a l i n i t y (CaC0 3) i n w a t e r o f e x p e r i m e n t a l f i e l d e n c l o s u r e s . P l o t t e d d a t a a r e combined t o show e f f e c t o f a q u a t i c macrophytes and-or sediment i n c h a n g i n g w a t e r c h e m i s t r y . . . . . . . . . 8 7 22. Ammonia i n w a t e r of e x p e r i m e n t a l f i e l d e n c l o s u r e s . P l o t t e d d a t a are combined t o show e f f e c t of a q u a t i c macrophytes and-or sediment i n c h a n g i n g water c h e m i s t r y 9 3 23. T o t a l K j e l d a h l N i t r o g e n i n w a t e r of e x p e r i m e n t a l f i e l d e n c l o s u r e s . P l o t t e d d a t a a r e combined"to show e f f e c t o f a q u a t i c macrophytes and-or sediment i n c h a n g i n g w a t e r c h e m i s t r y .. 98 X Figure Page 24. Total Organic Nitrogen i n water of experimental f i e l d enclosures. Plotted data are combined to show e f f e c t of aquatic macrophytes and-or sediment i n changing water chemistry 102 25. Orthophosphate i n water of experimental f i e l d enclosures. Plotted data are combined to show e f f e c t of aquatic macrophytes and-or sediment i n changing water chemistry.. > # 105 26. Total Phosphorus i n water of experimental f i e l d enclosures. Plotted data are combined to show ef f e c t of aquatic macrophytes and-or sediment i n changing water chemistry I l l 27. Total Organic Phosphorus i n water of experimental f i e l d enclosures. Plotted data are combined to show e f f e c t of aquatic macrophytes and-or sediment i n changing water chemistry. 113 28. Total counts of suspended bacteria i n enclosure A ( © ) , B ( A ) , C C O ) and D (A) 119 x i LIST OF. ABBREVIATIONS BOD B i o c h e m i c a l Oxygen Demand; the amount o f oxygen r e -q u i r e d by b a c t e r i a w h i l e energy i s d e r i v e d from t h e o x i d a t i o n of o r g a n i c m a t t e r . DO D i s s o l v e d Oxygen DOM D i s s o l v e d O r g a n i c M a t t e r N N i t r o g e n ; a l l forms. OP Orthophosphate; P0 4~P P .Phosphorus.' a i i forms. POM P a r t i c u l a t e O r g a n i c M a t t e r TKN T o t a l K j e l d h a l N i t r o g e n ; i . e . t o t a l o r g a n i c n i t r o g e n p l u s ammonia TON T o t a l O r g a n i c N i t r o g e n TOP T o t a l O r g a n i c Phosphorus TP T o t a l Phosphorus x i i ACKNOWLEDGMENTS I would J i k e t o e x p r e s s my s i n c e r e a p p r e c i a t i o n t o a l l o f my s u p e r v i s o r y committee, Dr. T, G. N o r t h c o t e , Dr. J . G. S t o c k n e r , Dr. K. J . H a l l and Dr, T. R. P a r s o n s , f o r t h e i r a t t e n -t i o n and h e l p f u l c r i t i c i s m s d u r i n g the cour s e of- the i n v e s t i -g a t i o n and p r e p a r a t i o n o f the t h e s i s . S p e c i a l thanks goes t o my major s u p e r v i s o r , Dr. T. G. N o r t h c o t e , f o r much v a l u a b l e c r i t i c i s m and c o n t i n u e d s u p p o r t o f t h i s work. Dr. K. J . H a l l o f f e r e d many good s u g g e s t i o n s f o r wh i c h I am v e r y g r a t e f u l . I would a l s o e s p e c i a l l y l i k e t o thank Dr. J . G. S t o c k n e r , f o r h i s h e l p f u l g uidance and f o r the e n j o y a b l e and m e a n i n g f u l d i s c u s s i o n s we had t o g e t h e r . I am v e r y g r a t e f u l t o Mr. I l m a r s D e r i c s , P l a n t S c i e n c e L a b o r a t o r y , U.B.C., and Mrs. E l i z a b e t h McDonald, P o l l u t i o n C o n t r o l L a b o r a t o r y , C i v i l E n g i n e e r i n g , U.B.C., who were most h e l p f u l i n p r o v i d i n g a d v i c e , a s s i s t a n c e and l a b o r a t o r y f a c i l i -t i e s , n e c e s s a r y f o r numerous c h e m i c a l a n a l y s e s r e q u i r e d f o r t h i s r e s e a r c h . Dr. R. J . D a l e y , C.C.I.W., P a c i f i c Environment I n s t i t u t e , p e r m i t t e d f r e e use o f h i s e p i - f l u o r e c e n c e m i c r o s c o p e and l a b o r -a t o r y space. F o r t h i s and h i s h e l p f u l i n s t r u c t i o n s , . I am v e r y g r a t e f u l . Mr. Stephen S t e a r n s , I n s t . A n i m a l Res. Eco., U.B.C., was most h e l p f u l and p a t i e n t when approached w i t h a problem. X l l l T h i s s t u d y was s u p p o r t e d by an N.R.C., 1967 S c i e n c e Scho-l a r s h i p 67-2311. F i n a , l l y , my w i f e , C h r i s t e l , d e s e r v e s s p e c i a l thanks f o r many hours o f t y p i n g and work r e q u i r e d f o r the f i n a l d r a f t o f t h i s t h e s i s . 1 INTRODUCTION A s t r i k i n g f e a t u r e o f most s h a l l o w f r e s h w a t e r l a k e s and-o f the l i t t o r a l a r e a o f many deep l a k e s i s t h e p r e s e n c e of a l u x u r i e n t growth o f a q u a t i c macrophytes. S i n c e most o f our Canadian l a k e s are s m a l l and o f the r e q u i s i t e morphometry t o s u p p o r t an e x t e n s i v e l i t t o r a l r e g i o n , t h e p r o d u c t i o n r a t e s o f the macrophytes, b o t h emergent and submergent, and t h e e p i p h y t i c and e p i p e l i c a l g a e c o n s t i t u t e major p o r t i o n s of t h e t o t a l a u t o t r o p h i c carbon f i x a t i o n . T h i s i s shown q u i t e c l e a r l y by s t u d i e s o f A l l e n (1971), P i e c z y n s k a (1972) , R i c h e t a l . (1971) and W e t z e l (1964,1969). Other r e c e n t s t u d i e s o f the r o l e o f a q u a t i c macrophytes have shown some v e r y r e l e v a n t r e s u l t s . A q u a t i c macrophytes can form the major i n p u t i n t o the a n n u a l b e n t h i c carbon bud-g e t o f a l a k e ( R i c h , 19 70). I n t h i s r e s p e c t , macrophytes are i m p o r t a n t i n d e t r i t u s f o r m a t i o n and b e n t h i c m e tabolism. Very s i g n i f i c a n t , r e c e n t d i s c o v e r i e s about th e r o l e o f t h e l i t t o r a l . f l o r a have been r e v e a l e d i n the d e t a i l e d s t u d i e s by W e t z e l (1969,1972) and A l l e n (1971a,1971b) who demonstrated t h a t . m a c r o p h y t e s e x c r e t e s i g n i f i c a n t amounts of d i s s o l v e d o r g a n i c m a t t e r (DOM). F u r t h e r m o r e , t h e s e a u t h o r s m a i n t a i n t h a t the m a c r o p h y t e - e p i p h y t e community can impose major d i r e c t and i n d i r e c t r e g u l a t o r y mechanisms on t h e m e t a b o l i s m o f an e n t i r e l a k e . That i s , t h e l i t t o r a l r e g i o n can e f f e c t i v e l y s i e v e o r 2 t r a p c e r t a i n d i s s o l v e d o r g a n i c compounds and i n o r g a n i c n u t r i -e n t s from e x t e r n a l o r l i t t o r a l s o u r c e s b e f o r e t h e y r e a c h the p e l a g i c zone a n d , on the o t h e r hand, the l i t t o r a l zone can a l s o f u n c t i o n as a s o u r c e o f such o r g a n i c and i n o r g a n i c chem-i c a l s . Other s t u d i e s have d e a l t w i t h the uptake of n u t r i e n t s by a q u a t i c p l a n t s showing t h a t macrophytes w i l l absorb n u t r i e n t s ( e s p e c i a l l y N and P) f a r i n e x c e s s o f t h e i r normal m e t a b o l i c r e q u i r e m e n t s ( G e r l o f f and Krombholz 1966, W i l s o n 1972), t h e r e -f o r e c o l l e c t i v e l y a c t i n g as a v a s t r e s e r v o i r o f s t o r e d n u t r i e n t s . V e r y l i t t l e n e t p r i m a r y macrophyte p r o d u c t i o n i s l o s t t o g r a z i n g , t h u s i t appears t h a t two major pathways e x i s t f o r the t r a n s f e r o f m a t t e r and energy from th e l i t t o r a l f l o r a . In l i v i n g a q u a t i c p l a n t s , the major t r a n s f e r o f m a t t e r and e n e r -gy o c c u r s as e x c r e t e d d i s s o l v e d o r g a n i c compounds, becoming e s -p e c i a l l y pronounced i n s e n e s c e n t p l a n t s ( O t s u k i and W e t z e l 1974). Subsequent t o the d e a t h o f macrophytes, a l l m a t t e r and energy i s s h u n t e d i n t o t h e a q u a t i c d e t r i t u s p o o l where i t i s u l t i m a t e l y m i n e r a l i z e d and r e c y c l e d . I t i s the p r o c e s s o f m i n e r a l i z a t i o n and d e g r a d a t i o n o f a q u a t i c p l a n t m a t e r i a l , e s p e c i a l l y t h e r e g e n e r a t i o n o f N and P, w h i c h i s the f o c u s o f t h i s s t u d y . F i g u r e 1 i l l u s t r a t e s the pathways a l o n g w h i c h a q u a t i c p l a n t m a t t e r and energy can be t r a n s f e r r e d , e m p h a s i z i n g t h a t t h e b u l k o f t h e n e t , s t o r e d p l a n t m a t t e r and energy i s t r a n s -f e r r e d a l o n g the d e t r i t a l pathway. F i g u r e 1 , The f a t e o f macrophyte net p r i m a r y p r o d u c t i o n and t h e pathways a l o n g whi-i m a t t e r and energy i s t r a n s p o r t e d . a. L i t t l e i n f o r m a t i o n a v a i l a b l e about th£s. b. C o n s i d e r e d most i m p o r t a n t , ( c f . Wetzel.& A l l e n 1972). c. C o n s i d e r e d i n s i g n i f i c a n t i n most c a s e s . d. P o s s i b l e d e s t r u c t i o n due t o wave a c t i o n , a c t i v i t i e s o f a q u a t i c f a u n a , e t c . 4 N E T , S T O R E D , P L A N T M A T T E R A N D E N E R G Y processing & recycling losses r A U T O L Y S I S M I N E R A L I Z A T I O N U T I L I Z A T I O N P L A N T D E T R I T U S S E D I M E N T A T I O N E X P O R T 5 U l t i m a t e l y one wish.es t o know what i s the f a t e o f t h i s macrophyte d e t r i t a l m a t t e r A c e r t a i n p r o p o r t i o n i s , o f .' c o u r s e , e n t i r e l y l o s t t o the a q u a t i c system e i t h e r by b e i n g ex-p o r t e d out o f i t o r by b e i n g b u r i e d i n the sediment. The r e -mainder o f the d e t r i t i c m a t t e r and energy i s p r o c e s s e d and r e c y c l e d by m i c r o b e s and s m a l l i n v e r t e b r a t e s . Moreover, some a q u a t i c d e t r i t i v o r e s w i l l u t i l i z e t h i s m a t e r i a l as a s o u r c e o f energy. U l t i m a t e l y however, the o r i g -i n a l n e t , s t o r e d p l a n t m a t t e r w i l l be r e c y c l e d t h r o u g h the d e t r i t a l pathway, u n d e r g o i n g an i n i t i a l p e r i o d o f a u t o l y s i s ( l e a c h i n g ) , f o l l o w e d by a p r o g r e s s i v e breakdown and m i n e r a l -i z a t i o n by a q u a t i c m i c r o o r g a n i s m s . One o f the l a r g e s t gaps i n t h e s t u d y o f a q u a t i c macro-p h y t e s i s t h a t of d e c o m p o s i t i o n and c y c l i n g o f n u t r i e n t s (Wetzel.and U l e h l o v a 1971, P i e c z y n s k a 1973). The l i t t l e i n f o r m a t i o n t h a t i s a v a i l a b l e i n the l i t e r a t u r e can be s o r t e d i n t o t h r e e main c a t e g o r i e s : 1 ) S t u d i e s d e a l i n g w i t h t h e d e c o m p o s i t i o n and n u t r i e n t c y c l i n g of emergent vege-t a t i o n , e s p e c i a l l y p l a n t s a s s o c i a t e d w i t h e s t u a r i n e ecosystems, such as S p a r t i n a spp. (Heald 1969, De l a Cruz 1965, D o w g i a l l o 1966, von S c h r o d e r 1973, B u r k h o l d e r 1957, Odum and De l a Cruz 1967, L a t t e r and Cragg 1967); 2) S t u d i e s d e a l i n g w i t h t h e de-c o m p o s i t i o n , n u t r i e n t r e g e n e r a t i o n and u t i l i z a t i o n o f l e a f l i t t e r i n f r e s h w a t e r , e s p e c i a l l y i n l o t i c ecosystems (Kaushik and Hynes 1968,1971, B a r l o c h e r and K e n d r i c k 1974, I y e r s e n 1972, 6 Cummins et a l . 1972, Wetzel and Manny 1972). 3) Studies d e a l -ing w i t h the ..decay and n u t r i e n t regeneration of a q u a t i c vas-c u l a r p l a n t s , mostly i n simulated or l a b o r a t o r y systems (Simsiman e t a l . 1972, Brooker and Edwards 1973, 1974, N i c h o l s and Keeney 1973, J e w e l l 1971). Some of the more important g e n e r a l i z a t i o n s coming out of r e s u l t s of these s t u d i e s are: (i) Dead p l a n t m a t e r i a l r a p i d l y and immediately loses l a b i l e organic compounds i n t o the water during an i n i t i a l p e r i o d of a u t o l y s i s or l e a c h i n g . ( i i ) This i s immediately followed by r a p i d decomposition of l a b i l e organic p l a n t m a t e r i a l and subsequent r a p i d r e l e a s e of n u t r i e n t s ( e s p e c i a l l y N and P) and an immediate r i s e i n BOD. ( i i i ) The decomposing p l a n t matter i s q u i c k l y enriched w i t h n u t r i e n t s ( e s p e c i a l l y N; i . e . p r o t e i n ) by c o l o n i z i n g microbes and concomitant exogenous m i c r o b i a l uptake. Both aquatic b a c t e r i a and f u n g i are important i n t h i s respect. (iv) The r a t e of decay of p l a n t m a t e r i a l most o f t e n f o l l o w s a hyperbolic, f u n c t i o n w i t h an i n i t i a l r a p i d decay r a t e f o l l o w e d by a slower but f a i r l y constant r a t e . There are always some re-f r a c t o r y residues which p e r s i s t over longer periods of time. (v) Major f a c t o r s which tend to s i g n i f i c a n t l y i n f l u e n c e the o v e r a l l process of decomposition and m i n e r a l i z a t i o n of aquatic macrovegetation are s p e c i f i c a l l y the N and P content of p l a n t m a t e r i a l and e s p e c i a l l y the temperature and n u t r i e n t q u a l i t y of the water. 7 The p r e s e n t s t u d y was t h e r e f o r e c o n c e i v e d t o answer a few q u e s t i o n s about t h e f a t e o£ macrophyte p r o d u c t i o n i n t h e l i t -t o r a l zone a t the end o f the growing season. In p a r t i c u l a r , a l a b o r a t o r y e x p e r i m e n t was d e s i g n e d t o answer the f o l l o w i n g q u e s t i o n s : 1 ) How and a t what r a t e does a q u a t i c p l a n t m a t e r i a l decompose ? 2) Does the d e c o m p o s i t i o n v a r y w i t h the n u t r i e n t c o n t e n t o f t h e w a t e r ? . 3) Are t h e r e any measureable changes i n t h e q u a l i t y o f the p l a n t d e t r i t u s b o t h w i t h r e s p e c t t o i t s p h y s i c a l f r a c t i o n a t i o n and i t s c h e m i c a l c o n t e n t ? . 4) And f i n a l l y t o what degree and r a t e are N and P r e -g e n e r a t e d ? I n o r d e r t o answer th e s e q u e s t i o n s , a submersed a q u a t i c v a s c u l a r p l a n t , a q u a t i c m i l f o i l ( M y r i o p h y l l u m s p p . ) , was chosen as p l a n t m a t e r i a l f o r t h e l a b o r a t o r y e x p e r i m e n t . A q u a t i c m i l f o i l due t o i t s f i n e s t r u c t u r e would n o t r e q u i r e an e x c e s s i v e l y l o n g time t o decompose. Moreover, t h i s p l a n t i s w i d e l y d i s t r i b u t e d and abundant i n a v a r i e t y o f l a k e s and ponds. The second q u e s t i o n p e r t a i n i n g t o whether d e c o m p o s i t i o n v a r i e s w i t h . n u t r i e n t c o n t e n t of w a t e r was r e s o l v e d by O b t a i -n i n g a q u a t i c m i l f o i l and w a t e r from two s i t e s o f d i f f e r e n t n u t r i e n t s t a t u s and b r i n g i n g i t back t o the l a b o r a t o r y . 8 The l a b o r a t o r y approach was chosen f o r t h i s aspect of the study s i n c e e s p e c i a l l y questions one and three could be d e a l t w i t h most a c c u r a t e l y under a'well c o n t r o l l e d s i t u a t i o n . F i n a l l y , p l a n t decomposition s t u d i e d i n the l a b o r a t o r y can be r e a d i l y maintained under, aerobic c o n d i t i o n s t h e r e f o r e o f f e r -in g i n f o r m a t i o n about N and P regeneration from decomposing aquatic p l a n t m a t e r i a l Where oxygen i s abundant (re: q u e s t i o n ' number f o u r ) . However, i n order to view the process of macrophyte de-gradation and m i n e r a l i z a t i o n w i t h i n a r e a l i s t i c framework, an " i n s i t u " experiment was designed. A l l of the dynamic func-t i o n s which are thought to i n f l u e n c e the process of. decomp-o s i t i o n and m i n e r a l i z a t i o n (eg. temperature, m i c r o b i a l suc-c e s s i o n , i n v e r t e b r a t e a c t i v i t y and the r e l a t i o n s h i p of the sediment) remained undisturbed. In t h i s way, the q u a n t i t y of N and P compounds regenerated by the decomposing aquatic macrophytes could a l s o be compared to amounts of N and P taken up or l i b e r a t e d by other components of the l i t t o r a l zone such as phytoplankton, b a c t e r i a and sediment. Again, s e v e r a l b a s i c questions were posed i n order to shed some l i g h t on the f a t e of macrophyte production at the end of the growing season. 1) How are N and P and some of t h e i r s p e c i f i c chemical compounds regenerated .? . 2) What i s the r e l a t i v e c o n t r i b u t i o n of the N and P r e -leased by the decaying p l a n t s to the l i t t o r a l water ? 9 3) I n t h i s r e s p e c t , what i s t h e r e l a t i o n s h i p o f the s e d i -ment t o t h e breakdown o f the a q u a t i c p l a n t s and t h e i r sub-sequent N and P r e l e a s e ? 4) And f i n a l l y , how much N and P i s removed from the w a t e r by suspended b a c t e r i a ? I t was r e a l i z e d from the o u t s e t o f t h e s t u d y t h a t due t o the extreme c o m p l e x i t y o f t h e s e d i m e n t - d e t r i t u s - m a c r o p h y t e system, the f i n a l r e s u l t s o f t h e s t u d y c o u l d n o t f u l l y r e s o l v e a l l o f t h e q u e s t i o n s posed, b u t m e r e l y b e g i n t o e l u c i d a t e some of the more o b v i o u s p r o c e s s e s and r e l a t i o n s h i p s e v i d e n t i n t h e systems s t u d i e d . r 10 STUDY SITES The f i e l d experimental p a r t of t h i s study was conducted on the west shore of a sm a l l r e s e r v o i r l o c a t e d on the extreme o o seaward side of Iona I s l a n d (49 25'N, 123 13'W). This i s l a n d , which i s p a r t of the Fraser estuary foreshore, i s s i t u a t e d be-tween the North Arm of the Fraser River and Sea I s l a n d j u s t south of Vancouver, B r i t i s h Columbia (Figures 2 and 3). Although i t i s c l o s e to the b r a c k i s h water of the Fraser estuary, the r e s e r v o i r contains f r e s h water, the p r i n c i p l e source of which i s rainwater. However, ground sources con-t r i b u t e s u f f i c i e n t n u t r i e n t s and other d i s s o l v e d s o l i d s to make the r e s e r v o i r water eutrophic ( s p e c i f i c conductance 2 86--1 325 Mmhos-cm ). The r e s e r v o i r i s e s s e n t i a l l y a shallow b a s i n of captured rainwater approximately 0.06 ha. i n area w i t h an average depth of l e s s than 2 to 3 m. One of the most prominent features of the r e s e r v o i r i s a profuse growth of aquatic p l a n t s from e a r l y summer (ca. June) to l a t e f a l l (ca. November). This p l a n t community i s repre-sented by only one species Myriophyllum spicatum L. (Eurasian w a t e r - m i l f o i l ) which dominates the e n t i r e r e s e r v o i r (Figure 4). The aquatic p l a n t s d i e o f f completely i n l a t e f a l l and s e t t l e to the bottom of the r e s e r v o i r or are washed along the shore-l i n e where they r a p i d l y decompose. Highest values f o r the n u t r i e n t chemistry of the r e s e r -11 F i g u r e 2 . Maps showing l o c a t i o n o f Iona r e s e r v o i r and Cedar V a l l e y pond ( i n s e r t map). 13 F i g u r e 3. A e r i a l v i e w o f Iona I s l a n d w i t h a rrow i n d i c a t i n g r e s e r v o i r . T i d a l f l a t s a r e i n f o r e g r o u n d and N o r t h Arm o f F r a s e r R i v e r i s seen from m i d d l e l e f t t o t o p r i g h t , j Figure 4a. Iona r e s e r v o i r : s t i p p l e d appearance of w a t e r s u r f a c e i s caused by emerging t i p s o f M. s p i c a t u m (water m i l f o i l ) . F i g u r e 4b. C l o s e up of water m i l f o i l g r o wing i n Iona r e s e r v o i r . 15 v o i r w ater were measured i n O c t o b e r , 197 4. A t t h a t time T o t a l K j e l d a h l N i t r o g e n (TKN) was 13.5 mg/1, N O 3 - N was 0.02 mg/1, T o t a l Phosphorus (TP.) was 0.549 mg/1 and o r t h o p h o s p h a t e (OP) was 0.012 mg/1. The w a t e r q u a l i t y and n u t r i e n t c h e m i s t r y o f t h e r e s e r v o i r w ater i n d i c a t e s t h a t i t i s a e u t r o p h i c s i t e . Sawyer (19 47) s u g g e s t s 0.3 mg/1 i n o r g a n i c N and 0.015 mg/1 s o l u b l e i n o r g a n i c P as c r i t i c a l l e v e l s above which e x c e s s i v e a l g a l growth o c c u r s . The e x c e s s i v e growth o f a l g a e n o t i c e d i n the r e s e r v o i r was good e v i d e n c e t o i n d i c a t e i t s e u t r o p h i c n a t u r e . Due t o t h e g r e a t abundance of a q u a t i c p l a n t s g r owing i n t h e r e s e r v o i r , i t s n u t r i e n t r i c h water and i t s p r o x i m i t y t o l a b o r a t o r y f a c i l i t i e s , t h e r e s e r v o i r on Iona I s l a n d p r o v i d e d a s u i t a b l e s i t e f o r an " i n s i t u " e x p e r i m e n t t o s t u d y t h e r e -l e a s e o f N and P compounds from th e l i t t o r a l f l o r a decomposing w i t h i n e x p e r i m e n t a l e n c l o s u r e s ( F i g u r e 5 ) . I n o r d e r t o answer the q u e s t i o n posed p r e v i o u s l y , "Does d e c o m p o s i t i o n v a r y w i t h the n u t r i e n t c o n t e n t of t h e w a t e r ? " , a q u a t i c p l a n t s were s e l e c t e d from t h e e u t r o p h i c Iona s i t e as w e l l as from a s m a l l pond c a . 6 km n o r t h (49° 1.2'N, 122°20'W) of M i s s i o n C i t y , B r i t i s h Columbia ( F i g u r e 2, i n s e r t map). The pond l i e s i n the Cedar V a l l e y and w i l l be r e f e r r e d t o as Cedar V a l l e y Pond. The pond, r o u g h l y h a l f t h e s i z e o f t h e Iona r e s e r v o i r i s formed by t h e damming of S i l v e r d a l e Creek w h i c h c o n t i n u a l l y 16 F i g u r e 5a. Sampling from e x p e r i m e n t a l f i e l d e n c l o s u r e s , Iona r e s e r v o i r . F i g u r e 5b. Appearance o f f o u r e x p e r i m e n t a l f i e l d e n c l o s u r e s i n the Iona r e s e r v o i r . 17 f l u s h e s t h e pond w i t h c l e a n ^ l o w n u t r i e n t w a t e r . T h e r e f o r e , t h e c o n c e n t r a t i o n o f n u t r i e n t s i n t h e pond water i s s u b s t a n -t i a l l y lower t h a n i n the Iona r e s e r v o i r . Midsummer measure-ments of n u t r i e n t c h e m i s t r y a t b o t h s i t e s showed TKN and n i t r a t e c o n c e n t r a t i o n s 3 and 10 t i m e s g r e a t e r , r e s p e c t i v e l y , i n t h e r e s e r v o i r w a t e r . An a q u a t i c m i l f o i l , M y r i o p h y l l u m h i p p u r o i d e s N u t t . dominates th e pond ( F i g u r e s 6 and 7 ) . A l t h o u g h d i f f e r e n t from the s p e c i e s growing i n the r e s e r v o i r , i t i s v e r y s i m i l a r i n s t r u c t u r e and appearance ( F i g u r e 8 ) . These two s i t e s p r o v i d e d t h e m a t e r i a l f o r t h e l a b o r a t o r y p a r t of t h i s s tudy w h i c h was c o n c e i v e d t o i n v e s t i g a t e t h e d e g r a d a t i o n o f ' a n a q u a t i c macrophyte and t h e subsequent r e l e a s e o f N and P compounds i n water o f d i f f e r e n t n u t r i e n t s t a t u s . F i g u r e 6a. Cedar V a l l e y Pond showing submerged a q u a t i c m i l f o i l . F i g u r e 6b. Submerged a q u a t i c m i l f o i l i n Cedar V a l l e y Pond. F i g u r e 7. C l o s e up o f M. h i p p u r o i d e s ( a q u a t i c m i l f o i l ) l y i n g i n s h a l l o w w a t e r o f Cedar V a l l e y Pond. — s , H o u n t e d v o u c h e r s p e c i m e n Q f m £ i 2 £ h x ^ ££ica±um L. from i o n a r e s e r v o i r . 21 F i g u r e 8b', Voucher specimen of Myriophyllum h i p p u r o i d e s Nutt. from Cedar V a l l e y pond. 22 METHODS AND MATERIALS • .1. L a b o r a t o r y E x p e r i m e n t 1.1 P r e p a r a t i o n o f m a t e r i a l and e x p e r i m e n t a l d e s i g n Pond water was c o l l e c t e d i n l a r g e g l a s s c a r b o y s from t h e pond and r e s e r v o i r and a l l o w e d t o e q u i l i b r i a t e . u n d e r a e r a t i o n f o r a p p r o x i m a t e l y two days. I n August 1974, t h e a q u a t i c p l a n t s were c o l l e c t e d from th e s h a l l o w water of b o t h s i t e s . Some samples were c a r e f u l l y p r e p a r e d as voucher specimens f o r l a t e r i d e n t i f i c a t i o n i n t h e l a b o r a t o r y . A c c o r d i n g t o H i t c h c o c k and C r o n q u i s t (1973) , t h e specimens were i d e n t i f i e d as M y r i o p h y l l u m s p i c a t u m L. (Iona r e s e r v o i r ) and M. h i p p u r o i d e s N u t t . (Cedar V a l l e y Pond). I d e n t i f i c a t i o n o f t h e specimens was g r e a t l y enhanced s i n c e many p l a n t s showed an i n f l o r e s c e n c e (see voucher specimens F i g u r e 8 ) . F r e s h , l i v e v e g e t a t i v e s h o o t s were sampled, d r i p d r i e d on paper t o w e l s and t r a n s p o r t e d i m m e d i a t e l y t o t h e l a b o r a t o r y . I n t h e l a b o r a t o r y , t h e s h o o t s were c a r e f u l l y washed s e v e r a l t i m e s w i t h t a p water making s u r e t o remove as much a t t a c h e d m a t e r i a l ( e p i p h y t i c a l g a e , s n a i l eggs) and v i s i b l e i n v e r t e -b r a t e s ( i n s e c t l a r v a e , s n a i l s ) as p o s s i b l e . Shoots were c u t i n t o 10 cm l e n g t h s and t e n o f each were p l a c e d i n t o e x p e r i m e n t a l l a b o r a t o r y c o n t a i n e r s . S e v e r a l amounts of b o t h M y r i o p h y l l u m h i p p u r o i d e s and M. s p i c a t u m were oven d r i e d t o d e t e r m i n e t h e a p p r o ximate d r y w e i g h t t o t e n s h o o t s . Ten s h o o t s o f M. h i p p u r o i d e s (Cedar V a l l e y Pond) 23 had an average d ry w e i g h t o f 1.0 ±.08 g and the same amount of s h o o t s weighed 1.3 ±.08 d r y wt i n M. s p i c a t u m (Iona r e s e r v o i r ) (average w e i g h t ±1 s t a n d a r d e r r o r ) . A l a b o r a t o r y e x p e r i m e n t was s e t up t o measure the de-g r a d a t i o n o f t h e a q u a t i c p l a n t s and t h e i r subsequent r e l e a s e of N and P ( F i g u r e 9 ) . 'One g a l l o n , c o v e r e d p l a s t i c c o n t a i n e r s used t o h o l d p l a n t s and w a t e r , were p l a c e d i n complete d a r k n e s s a t room t e m p e r a t u r e (2 2 C ±3) f o r the d u r a t i o n o f t h e ex-p e r i m e n t . P l a n t s h o o t s were p l a c e d i n t o 1 l i t r e o f t h e i r own pond (or r e s e r v o i r ) w a t e r . With e v e r y c o n t a i n e r h o l d i n g p l a n t s , a c o n t a i n e r w i t h j u s t 1 l i t r e o f t h e pond w a t e r was s e t up t o a c t as a c o n t r o l t o m o n i t o r background n u t r i e n t l e v e l s . F i n a l l y , the e n t i r e system was c o n s t a n t l y a e r a t e d ; t h e f l o w b e i n g i n -d i v i d u a l l y c o n t r o l l e d by a m a n i f o l d system o f p l a s t i c t u b i n g and v a l v e s . The f l o w was such t h a t a s t e a d y , slow s t r e a m o f bu b b l e s p a s s e d o u t o f t h e 4 mm d i a m e t e r t u b i n g . B e f o r e the a i r e n t e r e d t h e system, i t was p a s s e d t h r o u g h a 10 cm c h a r c o a l f i l t e r t o m i n i m i z e any c o n t a m i n a t i o n . No c o n t a i n e r went an-a e r o b i c d u r i n g any p a r t o f the e x p e r i m e n t . 1.2 Sa m p l i n g p r o c e d u r e The e x p e r i m e n t s t a r t e d as soon as the c o n t a i n e r s were p l a c e d i n t o t o t a l d a r k n e s s on August 6, 1974. A t i n t e r v a l s (3,7,13,24,41,63, and 100 days) a f t e r i n i t i a t i o n o f t h e ex-p e r i m e n t , a p l a n t and c o n t r o l c o n t a i n e r from b o t h systems (Cedar V a l l e y Pond and Iona r e s e r v o i r ) were em p t i e d f o r SYSTEM OF LABORATORY CONTAINERS C e d a r V a l l e y P o n d S y s t e m (a,a-, - h,h-j_) S a m p l i n g a x r s u p p l y 1 ° o b i o " T -7 —i— 1 3 2 4 Days I o n a R e s e r v o i r S y s t e m (A, A^ - H,^) C o n t r o l C o n t a i n e r ( e . g . a-^ ) 1 l i t r e w a t e r . T r e a t m e n t C o n t a i n e r ( e . g . a) A q u a t i c m a c r o p h y t e s p l u s 1 l i t r e w a t e r . F i g u r e 9. E x p e r i m e n t a l d e s i g n o f l a b o r a t o r y c o n t a i n e r s s h o w i n g s a m p l i n g d e s i g n a n d d e t a i l s N J o f c o n t a i n e r s . 25 a n a l y s i s . B o th the c o n t e n t s o f the p l a n t and c o n t r o l c o n t a i n e r were poured t h r o u g h a s e t o f s c r e e n s (1 mm and 0.2 mm)- and i n t o an Imhoff cone ( F i g u r e 10) . The s c r e e n s a l l o w e d the p a r t i c u l a t e p o r t i o n o f t h e t o -t a l sample t o be f r a c t i o n e d i n t o v a r i o u s p a r t i c l e s i z e s . Thus, the v a r i o u s d e t r i t a l f r a c t i o n s g e n e r a t e d i n t h e c o n t a i n e r s were p a r t i t i o n e d i n t o g r e a t e r t h a n 1 mm, 1 mm t o 0.2 mm and l e s s t h a n 0.2 mm s i z e c l a s s e s . The p a r t i c l e s o f l e s s t h a n 0.2 mm s i z e were the f l o c -c u l e n t o r g a n i c m a t t e r w h i c h s e t t l e d t o the bottom of the Im-h o f f cones d u r i n g a 6 h r . p e r i o d a l l o w e d f o r s e t t l i n g . T h i s p r o c e d u r e was used so t h a t most o f t h e suspended o r g a n i c m a t t e r c o u l d be s e p a r a t e d from the samples used t o d e t e r m i n e w a t e r c h e m i s t r y . The r e m a i n i n g h i g h l y c o l o u r e d s u p e r n a t a n t c o n s i s t e d m a i n l y o f d i s s o l v e d o r g a n i c m a t t e r and a v e r y s m a l l p r o p o r t i o n o f p a r t i c u l a t e m a t t e r . No attempt was made t o a c t i v e l y wash out t h e s i d e s and bottom o f t h e c o n t a i n e r s , o t h e r than a l i g h t r i n s e w i t h d i s -t i l l e d w a t e r . P l a n t r e s i d u e r e m a i n i n g on the 1 mm s c r e e n was r i n s e d l i g h t l y w i t h d i s t i l l e d w a t e r and oven d r i e d @ 60 C f o r 24 h o u r s . The d r i e d p l a n t m a t e r i a l was weighed, ground w i t h a m o r t a r and p e s t l e t o a f i n e powder and s t o r e d i n g l a s s v i a l s f o r l a t e r a n a l y s i s . The r e s i d u e on t h e 0.2 mm s c r e e n was r i n s e d w i t h d i s -26 ANALYSES OF  PLANT MATERIAL Total K j e l d a h l N T o t a l Phosphorus T o t a l Carbon Organic Content Dry Weight T o t a l contents of la b o r a t o r y containers WATER CHEMISTRY T o t a l K j e l d a h l N T o t a l Phosphorus N i t r a t e GF/C Glass. F i b r e F i l t e r ( 0 . 4 5 /<) F i l t r a b l e D i s s o l v e d Ortho Phosphate < 0. 20 mm Figure XQ. Flow chart showing procedure used a f t e r a la b o r a t o r y container was emptied. 27 t i l l e d w a t e r i n t o preweighed aluminum t r a y s , oven d r i e d @ 60 C f o r 2 4 hours and weighed. The r e m a i n i n g c o n t e n t s t h a t p a s s e d i n t o the Imhoff cones was topped o f f t o 1 l i t r e w i t h d i s t i l l e d w a t e r and a l l o w e d t o s e t t l e f o r 6 hours a f t e r w h i c h the s u p e r n a t a n t was c a r e f u l l y s i p h o n e d o f f . The u n d i s t u r b e d , s e t t l e d f l o e was r i n s e d i n t o preweighed aluminum t r a y s , d r i e d @ 60 C f o r 24 hours and weighed. 1.3 C h e m i c a l a n a l y s i s o f p l a n t m a t e r i a l T o t a l N and P was measured i n t h e ground p l a n t r e s i d u e a c c o r d i n g t o the p r o c e d u r e o u t l i n e d i n Appendix 1. The t o t a l o r g a n i c c o n t e n t o f the p l a n t samples was d e t e r -mined by i g n i t i n g the m a t e r i a l i n a m u f f l e f u r n a c e @ 550 C f o r 2 h o u r s . O r g a n i c c o n t e n t was thus t h e a s h - f r e e d r y w e i g h t . D e t e r m i n a t i o n o f t o t a l carbon i n the p l a n t m a t e r i a l was performed on an i n d u c t i o n - f u r n a c e , t o t a l carbon a n a l y s e r (LECO). Samples w e i g h i n g 50 mg were i g n i t e d a t h i g h t e m p e r a t u r e 2000-3000 C ) i n t h e a n a l y s e r and t h e t o t a l e v o l v e d C O 2 was t h e n v o l u m e t r i c a l l y measured. T o t a l carbon c o u l d t h e n be c a l c u l a t e d from t h e s e measurements f o r each sample t o w i t h i n +1% a c c u r a c y . Crude p r o t e i n was c a l c u l a t e d from t o t a l K j e l d a h l n i t r o g e n w i t h a 6.25 c o n v e r s i o n f a c t o r . 28 1.4 Che m i c a l a n a l y s i s o f water T o t a l N.was d e t e r m i n e d i n the s u p e r n a t a n t by the K j e l d a h l method (S t a n d a r d Methods 1971). To d e t e r m i n e t o t a l P, samples were t r e a t e d w i t h a p e r -s u l f a t e d i g e s t i o n , a u t o c l a v e d @ 15-20 p s i f o r c a . 30 m i n u t e s , n e u t r a l i z e d w i t h NaOH and f i n a l l y measured c o l o r i m e t r i c a l l y by the stannous c h l o r i d e p r o c e d u r e ( c f . S t a n d a r d Methods 19 7.1)'. Ortho P was measured a f t e r samples were f i l t e r e d t h r o u g h a Whatman 0.45// GF/C g l a s s f i b r e f i l t e r and t h e stannous c h l o r i d e p r o c e d u r e was used on the f i l t r a t e . The measure-ment th e n a c t u a l l y d e t e r m i n e d f i l t e r a b l e d i s s o l v e d o r t h o P ( c f . S t a n d a r d Methods 1971). R e a c t i v e n i t r a t e was measured d i r e c t l y and i m m e d i a t e l y on each sample u s i n g the cadmium r e d u c t i o n p r o c e d u r e as o u t -l i n e d i n S t r i c k l a n d and Parsons (196 8 ) . 29 2. F i e l d E x p e r i m e n t 2.1 E x p e r i m e n t a l d e s i g n F o u r a l u m i n u m c y l i n d e r s w e r e d e s i g n e d t o f a c i l i t a t e an " i n s i t u " s t u d y o f a c o l u m n o f t h e l i t t o r a l M y r i o p h y 1 1 u m  s p i c a t u m c o m m u n i t y i n t h e I o n a r e s e r v o i r . A l l c y l i n d e r s w e r e c a . 1 m h i g h w i t h an i n s i d e a r e a o f 0.5 m2 ( F i g u r e l l ) e n -c l o s i n g a v o l u m e o f c a . 300 l i t r e s o f l i t t o r a l z o n e . E a c h c y l i n d e r was c o v e r e d by a l i d t o p r e v e n t l i g h t and p r e -c i p i t a t i o n f r o m e n t e r i n g . Two c y l i n d e r s h a d o pen b o t t o m s and two w e r e s e a l e d . The two o p e n - e n d e d c y l i n d e r s w e r e p u s h e d i n t o t h e s e d i m e n t a b o u t 15 cm t o f o r m a s e d i m e n t - w a t e r s e a l . ' F i g u r e 12 shows t h e f i n a l a r r a n g e m e n t o f t h e f i e l d e n -c l o s u r e s . One o p e n - e n d e d c y l i n d e r e n c l o s e d an u n d i s t u r b e d c o l u m n o f t h e l i t t o r a l z one ( A ) . A n o t h e r c y l i n d e r c o n t a i n e d o n l y r e s e r v o i r w a t e r ( B ) . A n o t h e r c y l i n d e r e n c l o s e d a p o r t i o n o f s e d i m e n t and r e s e r v o i r w a t e r o n l y ( C ) . F i n a l l y , a 0.5 m^ a r e a o f l i t t o r a l z o n e was t o t a l l y h a r v e s t e d o f a q u a t i c p l a n t s a n d t h e s e w e r e p l a c e d i n t o a c y l i n d e r w i t h 300 l i t r e s o f r e s e r v o i r w a t e r ( D ) . T h u s , t h e m a j o r d i f f e r e n c e b e t w e e n t h e f o u r e x p e r i m e n t a l e n c l o s u r e s was i n t h e p r e s e n c e o r a b s e n c e o f e i t h e r a q u a t i c m a c r o p h y t e s o r s e d i m e n t . I n o r d e r t o d e t e r m i n e t h e v a r i a b i l i t y o f t h e s t a n d i n g c r o p o f M y r i o p h y l l u m c a p t u r e d i n t h o s e c y l i n d e r s w i t h p l a n t s , 7 r e p l i c a t e s a m p l e s w e r e t a k e n i n t h e a d j a c e n t a r e a w i t h one gure 1 1 . Example of experimental f i e l d enclosure w i t h s o l i d bottom. A L G A E P L A N T S S E D I M E N T A L G A E A L G A E A L G A E PLANTS miiiim Figure 1 2 . Experimental design of enclosures showing combinations of aquatic macrophytes and r e s e r v o i r sediment. CO 32 of the open c y l i n d e r s . The p l a n t s were harvested from the sampling c y l i n d e r , removing w i t h a rake as many of the p l a n t s as p o s s i b l e . The harvested p l a n t s were oven d r i e d f o r 24 hours @ 60 C and weighed to determine t h e i r standing crop i n dry weight. Subsamples of each r e p l i c a t e were ground to a f i n e t e x t u r e and s t o r e d i n screw-cap gla s s v i a l s f o r l a t e r chemical a n a l y s i s . D u p licate analyses were made f o r t o t a l phosphorus, t o t a l K j e l d a h l N, t o t a l carbon, organic content and. t o t a l crude p r o t e i n (TKN X 6.25) according to the procedures o u t l i n e d i n s e c t i o n 1.3 of METHODS AND MATERIALS. 2.2 Concepts,-Hypotheses and Assumptions The experimental design of the f i e l d enclosures (Figure 12) was i n accordance w i t h c e r t a i n concepts known about the n u t r i e n t c y c l i n g among various organic and i n o r g a n i c com-ponents w i t h i n the l i t t o r a l zone of aquatic ecosystems.. Figure 13 i l l u s t r a t e s the concept of various N and P sources, p o o l s , pathways and s i n k s w i t h i n the experimental c y l i n d e r . No attempt i s made to i l l u s t r a t e the extremely v a r i a b l e f l u x r a t e s , turn-over times or magnitude of various n u t r i e n t pathways. F i r s t , any source of n u t r i e n t s other than from the r e -s e r v o i r sediment, or from components w i t h i n the c y l i n d e r , i s excluded. The main components w i t h i n the c y l i n d e r thought to 33 F i g u r e 13, Concept o f N and P r e g e n e r a t i o n , c y c l i n g and a d s o r p t i o n (shown by arrows) of v a r i o u s s o u r c e s and components w i t h -i n the e x p e r i m e n t a l f i e l d e n c l o s u r e . . 35 play a major r o l e i n N and P c y c l i n g are: 1) the sediment, both as a n u t r i e n t source and s i n k 2) the aquatic p l a n t s , mainly as a n u t r i e n t source as they decompose and 3) the algae again, mainly as a n u t r i e n t source as they break down. Another important component are the b a c t e r i a which, i n the absence of primary producers, would immobilize as w e l l as r e l e a s e s u b s t a n t i a l amounts of DOM as t h e i r populations begin t o grow r a p i d l y . Moreover, c e r t a i n assumptions had to be made due to the d i f f i c u l t y of measuring some components. D e n i t r i f y i n g bac-t e r i a , e s p e c i a l l y under anaerobic c o n d i t i o n s might act as a N sink i n the c y l i n d e r , causing N to escape i n i t s gaseous form. Gaseous N was not measured and t h e r e f o r e t h i s N sink could not be i n c o r p o r a t e d i n t o any subsequent c a l c u l a t i o n s . Adsorption of N and P compounds could occur on the w a l l s of the c o n t a i n e r . Again, t h i s was not measured but assumed to be small i n p r o p o r t i o n to the l e v e l s of N and P regenerated i n the water. F i n a l l y , enclosed s m a l l i n v e r t e b r a t e s w i l l c o n t r i b u t e N and P upon t h e i r death. However, d i r e c t observations i n -d i c a t e d that the t o t a l i n v e r t e b r a t e biomass was l e s s than one tenth of the t o t a l biomass of p l a n t s and algae w i t h i n the enclosures. The f i e l d experiment was designed i n such a way as to provide a s u i t a b l e t e s t f o r i n v e s t i g a t i n g the r e l a t i v e r o l e s of aquatic p l a n t s and and sediment i n regenerating N and P 36 i n t o the l i t t o r a l water column. Moreover, any other major b i o t i c component i n the water c o n t a i n i n g N and P, such as phytoplankton, would manifest i t s e l f by r e l e a s i n g appreciable amounts of N and P compounds as i t decomposed. Measurements from each c y l i n d e r could be compared i n four d i f f e r e n t ways thereby r e v e a l i n g the c o n t r i b u t i o n of e i t h e r the p l a n t s , the sediment, or both to N and P l e v e l s i n the water. The expected r e s u l t s are i l l u s t r a t e d (Figure 1 4 ) f o r the hypotheses t h a t : 1 ) The aquatic p l a n t s c o n t r i b u t e s i g n i f i -c a n t l y t o N and P l e v e l s i n the water a f t e r t h e i r breakdown (cf. B and D i n 2 ) . 2) Aquatic p l a n t s c o n t r i b u t e s i g n i f i c a n t l y to N and P l e v e l s but t h e i r e f f e c t may be m i t i g a t e d or enhanced by the presence of the sediment i n which they are rooted (cf. A and C i n 1 ) . 3) The sediment w i l l e i t h e r c o n t r i b u t e t o or remove from the water a c e r t a i n amount of N and P ( c f . C and B i n 4 ) . And f i n a l l y : 4) The sediment w i l l remove or c o n t r i -bute N and P but t h i s may be a f f e c t e d by the presence of the rooted p l a n t s ( cf. A and D i n 3 ) . Curves r e s u l t i n g from the experimental data can be i n t e -grated over time, and t h e i r d i f f e r e n c e w i l l account f o r the e f f e c t of the major components i l l u s t r a t e d i n F i g u r e 1 3 (rooted p l a n t s , algae and sediment). 2 . 3 Sampling procedure The f i e l d experiment was s t a r t e d on October 1 , 1 9 7 4 and from t h a t date, a l l four c y l i n d e r s and the r e s e r v o i r water 37 F i g u r e 14. E x p e c t e d and h y p o t h e s i z e d r e s u l t s o f e n c l o s u r e s combined i n f o u r d i f f e r e n t ways t o show r e g e n e r a t i o n o f n u t r i e n t s (N and P) due t o p l a n t , a l g a e and sediment. O CO O CD D I + 39 o u t s i d e the c y l i n d e r s , were sampled a f t e r 5, 10, 15, 22, 36,,0 50 and 70 days. A t t h i s t i me a l s o , t h e a q u a t i c p l a n t s were s t i l l g reen and l i v i n g and no o b v i o u s i n d i c a t i o n o f senescence or d e a t h was e v i d e n t . In the f i e l d , t e m p e r a t u r e , pH and d i s s o l v e d oxygen measurements were t a k e n i m m e d i a t e l y . A t f i r s t , d i s s o l v e d O2 measurements were made by a m i c r o - W i n k l e r p r o c e d u r e u s i n g 5 cc g l a s s s y r i n g e s ( c f . H a l l and K l e i b e r 1973). L a t e r measure-ments were more e a s i l y and r e l i a b l y o b t a i n e d u s i n g a YSI oxygen probe meter. Samples f o r d e t e r m i n i n g w a t e r c h e m i s t r y were c o l l e c t e d i n p l a s t i c s a m p l i n g b o t t l e s about 10-2 0 cm under t h e s u r f a c e of t h e w a t e r . These samples were a n a l y s e d by t h e c h e m i s t r y l a b o r a t o r y o f t h e Water Resources S e r v i c e a t The U n i v e r s i t y o f B r i t i s h C olumbia f o r the t o t a l a l k a l i n i t y (as mg/1 C a C 0 3 ) , ammonia-N, n i t r a t e - N , n i t r i t e - N , t o t a l k j e l d a h l - N , o r t h o - P , and t o t a l - P . A d e t a i l e d d e s c r i p t i o n o f the v a r i o u s a n a l y t i c a l p r o -cedures used can be found i n McQuaker (19 73) . 2.4 B a c t e r i a l a n a l y s i s I t i s w e l l know t h a t e n r i c h m e n t media t e c h n i q u e s ( p l a t e c o unts) g i v e o n l y a s m a l l f r a c t i o n o f t h e t o t a l number o f b a c t e r i a i n w a t e r and s o i l (Overbeck 1974). D i r e c t m i c r o -s c o p i c counts a r e f a r s u p e r i o r f o r any e c o l o g i c a l work. Recent 40 m o d i f i c a t i o n s o f the d i r e c t c o u n t i n g t e c h n i q u e u s i n g f i l t e r e d samples and f l u o r e s c e n t s t a i n s have p r o v e d s u c c e s s f u l i n o f f e r i n g a s i m p l e and a c c u r a t e method f o r o b t a i n i n g t o t a l b a c t e r i a counts i n w a t e r (Daley 1975, F r a n c i s c o e t a l . 1973, HObbie e t a l . 1972, Jones 1974). The e x a c t p r o c e d u r e used i n t h i s s t u d y was as f o l l o w s : samples were c o l l e c t e d i n s m a l l 125 ml p l a s t i c b o t t l e s w h i c h were k e p t on i c e u n t i l samples were e x t r a c t e d some 3-4 hours l a t e r . Samples were d i l u t e d w i t h a 5% s o l u t i o n o f a c r i d i n e orange f l u o r e s c e n t s t a i n i n the r a t i o o f 1:9, 9:1, o r 5:5 depending on t h e c o n c e n t r a t i o n o f b a c t e r i a i n t h e sample. Samples were a l l o w e d about 3 min c o n t a c t time w i t h the s t a i n , i m m e d i a t e l y a f t e r w h i c h an a l i q u o t o f 1 ml was t a k e n and f i l t e r e d t h r o u g h a .45^ S a r t o r i u s b l a c k background f i l t e r u s i n g no more th a n c a . 8.0 cm Hg vacuum on a M i l l i p o r e f i l -t r a t i o n a p p a r a t u s . The f i l t e r was then r i n s e d w i t h 5 ml d i s t i l l e d , p r e - f i l t e r e d (0. 2ju) w a t e r and t r a n f e r r e d t o a m i c r o -scope s l i d e . N o n - f l u o r e s c e n t immersion o i l was used on b o t h s i d e s o f the f i l t e r b e f o r e a c o v e r s l i p was p l a c e d onto i t . The b a c t e r i a were then ready t o be counted on a L e i t z O r t h o p l a n m i c r o s c o p e , f i t t e d w i t h 10 X o c u l a r s , an NPL 100 X o i l immersion o b j e c t i v e and a Ploem v e r t i c a l i l l u m i n a t i o n . A comprehensive a c c o u n t and e v a l u a t i o n o f t h i s p r o c e d u r e i s o u t l i n e d by Daley (1975). . The average d i s t r i b u t i o n o f b a c t e r i a counted p e r e y e p i e c e g r a t i c u l a t e was about 20, and 20 o f t h e s e f i e l d s were counted 41 on each f i l t e r ; t h e r e f o r e , about 400 b a c t e r i a were counted per sample. The p r e c i s i o n o f t h i s t y p e o f e s t i m a t e can be c a l c u l a t e d ( C a s s e l l 1965). Data f o r t o t a l b a c t e r i a counts i n t h i s s t u d y have a 95% c o n f i d e n c e i n t e r v a l of ± 10% of the mean. 2,5 Sediment c h e m i s t r y S e v e r a l r e p l i c a t e c o r e samples o f the r e s e r v o i r s u r f a c e mud were o b t a i n e d w i t h a Kaj a k c o r e r . Samples o f mud r a n g i n g from 80 t o 160 ml and from 8 t o 10 cm c o r e - l e n g t h were s t o r e d i n p l a s t i c cups and homogenized p r i o r t o c h e m i c a l a n a l y s i s . P e r c e n t t o t a l v o l a t i l e was o b t a i n e d by i g n i t i n g mud samples i n a m u f f l e f u r n a c e @ 550 C f o r c_a. 2 hours and c a l c u l a t i n g a s h - f r e e d r y w e i g h t . T o t a l n i t r o g e n i n t h e sediment was d e t e r m i n e d by t h e K j e l d a h l p r o c e d u r e . D e t e r m i n a t i o n s o f t o t a l phosphorus and o r g a n i c c a r b o n i n the sediment was c a r r i e d out by the C h e m i s t r y L a b o r a t o r y o f the Water Resources S e r v i c e , a t t h e U n i v e r s i t y o f B r i t i s h Columbia. F u s i o n p l u s c o l o r i m e t r i c : a s c o r b i c a c i d r e d u c t i o n was. used t o deter m i n e t o t a l P and the Dorhman DC-50 T o t a l O r g a n i c Carbon A n a l y z e r was used f o r o r g a n i c carbon a n a l y s i s . 42 RESULTS AND DISCUSSION 1 . L a b o r a t o r y E x p e r i m e n t 1 . 1 I n i t i a l n u t r i e n t c o n t e n t o f a q u a t i c p l a n t s and w a t e r In o r d e r t o o b t a i n p r e c i s e and m e a n i n g f u l r e s u l t s from the l a b o r a t o r y e x p e r i m e n t , the v a r i a b i l i t y w i t h i n and among b o t h systems o f e x p e r i m e n t a l c o n t a i n e r s had t o be a t an a c c e p t a b l e l e v e l . S i n c e t e m p e r a t u r e and w a t e r c h e m i s t r y were v i r t u a l l y i d e n t i c a l w i t h i n each system, th e main e r r o r t h a t c o u l d p o t e n t i a l l y have been i n t r o d u c e d i n t o the e x p e r i m e n t , would have been due t o t h e p l a n t m a t e r i a l . The v a r i a b i l i t y o f t h e N and P c o n t e n t o f the p l a n t m a t e r i a l i n t r o d u c e d i n t o each system was measured i n d u p l i c a t e on 5 r e p l i c a t e samples. The r e s u l t s o f t h e s e a n a l y s e s (Table I ) p r o v i d e s an e s t i -mate o f the p o t e n t i a l e r r o r i n t r o d u c e d i n t o t h e e x p e r i m e n t . The n u t r i e n t t i s s u e c o n c e n t r a t i o n s i n t h e p l a n t m a t e r i a l show an a c c e p t a b l e l e v e l o f v a r i a b i l i t y w i t h i n b o t h systems ( s t a n d a r d e r r o r r a n g i n g from . 0 1 t o . 1 ) . F u r t h e r m o r e , th e c o e f f i c i e n t s o f v a r i a t i o n between b o t h systems were q u i t e comparable. On t h e b a s i s o f t h i s p r e l i m i n a r y i n v e s t i g a t i o n , i t was c o n c l u d e d t h a t w i t h r e s p e c t t o o r g a n i c p l a n t N and P, t h e r e would be no s i g n i f i c a n t e r r o r i n t r o d u c e d i n t o the e x p e r i m e n t . A l l c o n t a i n e r s w i t h i n each system were a c c e p t e d as b e i n g good r e p l i c a t e s . 4 3 Table I. V a r i a b i l i t y in N and P tissue contents of Myriophyllum tissue introduced to system of containers. Iona Reservoir System . Duplicate Samples Average Percent N Mean S.D. C.V. S.E, Average Percent Phosphate a Mean S.D. C.V. S.E. 1. 2.49 2.62 .211 8.0 .094 .453 . 501 .032 6.5 . 014 2. 2.46 . 498 3. 2.81 .543 4. 2. 85 • 5 1 3 5. 2.40 .498 Cedar Valley Pond System . Duplicate Samples Average Percent N Mean S.D. C.V. S.E. Average Percent Phosphate b Mean S.D.' C.V. S.E. 1. 3.24. 3.04 .239 7.8 - .106 .560 . 605 .030 4.9 . 013 2. 3.22 . 600 3. 2. 75 . 645 4. 2.81 . 608 5. 3. 18 .612 S.D. = Standard Deviation, C . V . C o e f f i c i e n t of Variat ion, S.E. = Standard Error a Average Total P = .206 b Average Total .P = .249 44 I n i t i a l c h a r a c t e r i s t i c s o f t h e M y r i o p h y l l u m sampled i n b o t h s i t e s on August 197 4 t o s t a r t the l a b o r a t o r y e x p e r i -ment a r e shown i n T a b l e I I . I t became i m m e d i a t e l y o b v i o u s t h a t t h e N and P t i s s u e c o n c e n t r a t i o n s o f Iona p l a n t s had changed s i g n i f i c a n t l y s i n c e a p r e v i o u s s a m p l i n g d a t e i n June 1974. T h i s i s not s u r p r i s i n g s i n c e marked s e a s o n a l d i f f e r e n c e s i n t h e N and P t i s s u e c o n t e n t of a q u a t i c p l a n t s have been r e p o r t e d i n t h e l i t e r a t u r e (Caines 1965, G o u l d e r and Boatman 1971 and S t a k e 1967, 1968) Another i n t e r e s t i n g q u a l i t y o f t h e a q u a t i c p l a n t samples i s t h e i r h i g h t o t a l p r o t e i n c o n t e n t , r a n g i n g from 16-26% on a d r y w e i g h t b a s i s . The h i g h n u t r i t i v e q u a l i t y o f t h e M y r i o p h y l l u m i s f u r t h e r e x e m p l i f i e d by i t s C:N r a t i o r a n g i n g from 14:1 t o 16:1 w h i c h s u r p a s s e s t h e average r e q u i r e m e n t s f o r a n i m a l f o o d i n t a k e ; the C:N r a t i o o f which i s about 17:1 ( R u s s e l - H u n t e r 1970). B o t h N and P t i s s u e l e v e l s o f M y r i o p h y l l u m sampled i n t h i s s t u d y f i t w e l l i n t o t h e range o f v a l u e s r e p o r t e d i n t h e l i t e r a t u r e (Table I I I ) . The range of P p l a n t t i s s u e con-c e n t r a t i o n s i n t h i s s t u d y a r e quoted b o t h as t o t a l P and as P O 4 - P , per g d r y wt. I n s e v e r a l i n s t a n c e s i t was u n c e r t a i n whether P t i s s u e c o n c e n t r a t i o n s c i t e d i n t h e l i t e r a t u r e were a c t u a l l y t o t a l P o r P O 4 - P . Perhaps t h i s f a c t m ight a c c o u n t f o r t h e l a r g e range of P v a l u e s e v i d e n t i n t h e s e d a t a (Table I I I ) . T a b l e I I . C h a r a c t e r i s t i c , p e r d r y w e i g h t , o f M y r i o p h y l l u m a t i n i t i a l e x p e r i m e n t a l c o n d i t i o n s , ( A u g u s t 1 9 7 4 ) . F i g u r e s i n b r a c k e t s r e p r e s e n t r e s u l t s o f J u n e 1974 s a m p l i n g . P e r c e n t T o t a l P e r c e n t P e r c e n t S p e c i e s S a m p l i n g S i t e P e r c e n t D r y wt O r g a n i c C o n t e n t N u t r i e n t T i s s u e C o n c e n t r a t i o n C:N R a t i o T o t a l . P r o t e i n C N P 0 4 _ p M. h i pp u r o i d'e s C e d a r V a l l e y P ond 86.7 43.9 3.04 . .605 . 14. 4:1 19. 0 M. ' s p i c a t u m I o n a R e s e r v o i r 11. 2 86.6 43.6 2.62 .501 (4. 19) (.378) 16. 6:1 16.3 (26.1) 46 Table I I I . Range of N and P t i s s u e contents of Myriophyllum spp. reported i n the l i t e r a t u r e . Range, N % dry wt P Myriophyllum Species Reference L o c a t i o n - Notes 1. 2. 6-4.2 (.38-.61) .16-.25 M. M. spicatum hippuroides THIS STUDY a e u t r o p h i c r e s e r -v o i r and a meso-•trophic pond i n S.W. B r i t i s h Columbia. 2. 1. 48 0.3 M. exalbescens . Nichols and Keeney (1973) at 4 m depth i n L. Mendota. 3. 2. 35 - M. heterophyllum P o l i s i n i and Boyd (1972) Par Pond, S. C a r o l i n a . 4. .43-.45 M. M. B r a s i l i e u s e F a r w e l l i i Adams (1973) v a r i o u s lakes i n N. E. , U.S.A.. 5. 1. 8-2.3 .120-.27 M. pinnatum Harper et a l . (1934) Oklahoma lakes and ponds. 6. - . 16 M. heterophyllum Boyd (1970) Par Pond, S. C a r o l i n a . 7. 2. 7-4.4 • 5-1.8 M. spicatum Ryan (1972) water of three d i f -f e r e n t f e r t i l i z a t i o n treatments. 8. - .06-1. 38. M. exalbescens Wilson (1972) water of low (0.1 M) to high (100 M) phosphate cone. 9, 2. 1-2.9 0.3-0.4 M. spicatum Mulligan (1969) i n o r g a n i c N and P enrichment e x p e r i -ments; 10. 2. 4-2.7 0.3-0.4 M. spp. G e r l o f f et a l . (1966) h i g h l y f e r t i l e L. Mendota. 11. - .09-.26 M. a l t e r n i f l o r urn .Caines (1965) a f e r t i l i z e d and u n f e r t i l i z e d Loch i n Scotland. 1.4 8-4.4 .06-1.8 Total Range Reported * (P0 4-P) 47 Most i m p o r t a n t o f a l l , t he Iona r e s e r v o i r w a t e r used i n t h e c o n t a i n e r s was f o u r t i m e s g r e a t e r i n TKN (2.80 mg/1) t h a n the Cedar V a l l e y pond water (TKN = 0.7 mg/1). L e v e l s of NO3-N were a l s o much h i g h e r i n t h e Iona water ( 0.2 v s . 0.03 mg/1); t h e r e i s a l m o s t a 10 f o l d d i f f e r e n c e h e r e . Thus t h e r e was a s i g n i f i c a n t l y l a r g e r t o t a l N p o o l a v a i l a b l e i n the Iona c o n t a i n e r s t h a n i n t h e Cedar V a l l e y c o n t a i n e r s . T o t a l and d i s s o l v e d P l e v e l s were q u i t e s i m i l a r i n b o t h systems, b e i n g o n l y s l i g h t l y h i g h e r i n Iona water (23 v s . 20 yg/1)..'. Ortho-P l e v e l s , as can be e x p e c t e d i n mid-summer, were e x t r e m e l y low, b e i n g below l e v e l s o f d e t e c t i o n ( l e s s t h a n 3 ug/1) i n b o t h systems. 1.2 D e g r a d a t i o n o f a q u a t i c p l a n t m a t e r i a l Soon a f t e r t h e M y r i o p h y l l u m was p l a c e d i n t o t o t a l d a r k -n e s s , t h e shOots became n o t i c e a b l y p a l e , s u g g e s t i n g t h a t d e a t h ensued s h o r t l y a f t e r l i g h t was no l o n g e r a v a i l a b l e . The s t r u c t u r e o f t h e p l a n t however, was r e t a i n e d f o r a' s u r p r i s i n g l y l o n g t i m e c o n s i d e r i n g how much biomass had been l o s t . Note t h a n i n F i g u r e 15, t h e p l a n t s a f t e r 13 days a r e o n l y 28% of t h e i r o r i g i n a l d r y w e i g h t , y e t they remain r e l a t i v e l y un-changed i n appearance. Other r e s u l t s o f t h i s e x p e r i m e n t d e s -c r i b e d l a t e r w i l l b e g i n t o e x p l a i n t h i s phenomenon. D u r i n g 48 V F i g u r e 15. View i n s i d e l a b o r a t o r y c o n t a i n e r showing appearance o f macrophyte a f t e r 13 days i n d a r k n e s s . These p l a n t s were o n l y 28% o f t h e i r o r i g i n a l d r y w e i g h t . 49 subsequent s a m p l i n g s (24 and 41 days) however, the p l a n t s began t o n o t i c e a b l y d i s a p p e a r u n t i l o n l y stem fragments and o t h e r s m a l l amorphous r e f r a c t o r y p a r t i c l e s remained; D e c o m p o s i t i o n r a t e s i n t h e e x p e r i m e n t were i n i t i a l l y q u i t e h i g h . In the Iona r e s e r v o i r system, o n l y 50% o f the d r y w e i g h t of p l a n t m a t e r i a l remained a f t e r 7-13 days and v i r t u a l l y e v e r y t h i n g i n t h e g r e a t e r t h a n 1 mm s i z e c l a s s d i s a p p e a r e d between 24 and 41 days ( F i g u r e 1 6 ) . S i m i l a r i l y , i n the Cedar V a l l e y system 50% remained s h o r t l y a f t e r two weeks and l e s s t h a n 5% remained a f t e r 63 days. Comparable i n i t i a l h i g h r a t e s o f d e c o m p o s i t i o n have been r e p o r t e d i n a l m o s t e v e r y s t u d y d e a l i n g w i t h the d e g r a d a t i o n o f p l a n t m a t t e r i n f r e s h w a t e r ( D o w g i a l l o 1966, Kormondy 1968, K a u s h i k and Hynes 1971, I v e r s e n 1973, Lush and Hynes 1974, J e w e l l 1971, N i c h o l s and Keeney 1973, Laube and Wohler 1973). A few of t h e s e s t u d i e s have atte m p t e d t o demonstrate and e x p l a i n f a c t o r s w h i c h might a c c o u n t f o r d i f f e r e n c e s i n de-c o m p o s i t i o n r a t e s between d i f f e r e n t p l a n t m a t e r i a l s o r a q u a t i c h a b i t a t s . I n t h i s r e g a r d , t h e g e n e r a l consensus seems t o be t h a t the n u t r i e n t c o n t e n t o f t h e w a t e r and p l a n t s , e s p e c i a l l y N and/or P, seems t o c o n t r o l o v e r a l l r a t e s o f d e c o m p o s i t i o n and m i n e r a l i z a t i o n ( J e w e l l 1971, D o w g i a l l o 19 66, N i c h o l s and Keeney 1973 and W i l l i a m s e t a l . 1968, K a u s h i k and Hynes 1971). The major d i f f e r e n c e between t h e two e x p e r i m e n t a l l a b o r a t o r y systems was i n t h e n u t r i e n t c o n c e n t r a t i o n o f t h e i r w a t e r ; th e r e s e r v o i r w a t e r h a v i n g much h i g h e r l e v e l s o f N 50 F i g u r e 16. Mass b a l a n c e d i s t r i b u t i o n o f v a r i o u s d e t r i t a l f r a c t i o n s i n t h e two systems o f c o n t a i n e r s d u r i n g c o u r s e o f e x p e r i m e n t . The n e t b a l a n c e i s shown as DOM t o acc o u n t f o r t h e t o t a l p l a n t m a t t e r o r i g i n a l l y i n t r o d u c e d i n t o t h e systems. 51 IONA RESERVOIR SYSTEM Time (days) 3 7 13 24 41 63 100 3 7 13 24 41 63 100 Time (Days) 52 CEDAR VALLEY POND SYSTEM Time (days) Time (days) 53 and P t h a n t h e pond w a t e r . There i s no doubt t h a t t h e d i f -f e r e n c e i n n u t r i e n t c o n c e n t r a t i o n i n the w a t e r o f the e x p e r i -m e n t a l l a b o r a t o r y systems was t h e p r i n c i p l e f a c t o r c o n t r i b u t i n g t o t h e d i f f e r e n c e i n the d e c o m p o s i t i o n r a t e o f p l a n t m a t t e r g r e a t e r t h a n 1 mm. In l i g h t o f e v i d e n c e from the l i t e r a t u r e d i s c u s s e d p r e v i o u s l y and r e s u l t s o f t h e l a b o r a t o r y e x p e r i m e n t , t h e above i n t e r p r e t a t i o n seems r e a s o n a b l e . 54 1.3 C h e m i c a l c h a r a c t e r i s t i c s and amount o f d e t r i t a l f r a c t i o n s As t h e l a r g e r p i e c e s o f p l a n t m a t e r i a l ( g r e a t e r t h a n 1 mm) d i s a p p e a r e d a l m o s t e n t i r e l y i n b o t h systems ( F i g u r e 1 6 ) , a measurable p o r t i o n of p l a n t m a t e r i a l remained as minute de-t r i t a l f r a c t i o n s , c o l l e c t i n g i n t h e bottom of t h e c o n t a i n e r s as f i n e amorphous p a r t i c l e s of o r g a n i c m a t e r i a l . A l t h o u g h n o t l a r g e i n q u a n t i t y , t h i s f i n e d e t r i t u s i s n e v e r t h e l e s s i m p o r t a n t due t o i t s l a r g e s u r f a c e : volume r a t i o ( G o s s e l i n k and K i r b y , 1974), p r o v i d i n g a good s u b s t r a t e f o r b a c t e r i a . Moreover s m a l l e r p a r t i c l e s i z e may i n c r e a s e t h e amount of d i s s o l v e d o r g a n i c m a t t e r w h i c h i s adsorbed (Lenz 1972). The r e l a t i v e d i s t r i b u t i o n o f v a r i o u s d e t r i t a l f r a c t i o n s , based on a mass b a l a n c e c a l c u l a t i o n , i s r e p r e s e n t e d i n T a b l e IV. A l l s i z e c l a s s e s are e x p r e s s e d i n p r o p o r t i o n t o t h e t o t a l o r i g i n a l p l a n t mass i n t r o d u c e d i n t o each system. The d i f f e r e n c e i n w e i g h t between the o r i g i n a l t o t a l p l a n t biomass and t h e t o t a l s e t t l e d d e t r i t u s p o o l a t any g i v e n t ime makes up t h e b a l a n c e ( i . e . w e i g h t unaccounted f o r ) . I n t h i s s t u d y , t h e b a l a n c e c o n s i s t e d a l m o s t e n t i r e l y o f d i s s o l v e d , o r g a n i c m a t t e r (DOM) s i n c e suspended m a t t e r i n t h e w ater was n e g l i g i b l e ( 1 - 3 0 yg/1). As d i s c u s s e d e a r l i e r , t h e l a r g e p i e c e s of p l a n t m a t t e r ( g r e a t e r t h a n 1 mm) d i s a p p e a r e d q u i t e r a p i d l y . Table IV. R e l a t i v e d i s t r i b u t i o n of v a r i o u s d e t r i t a l f r a c t i o n s i n system of c o n t a i n e r s during course of experiment. R e s u l t s , except "Balance", i n g dry wt. Iona R e s e r v o i r System D e t r i t u s Time i n days from beginning of experiment Catagory S i z e 3 13 | 24 | 41 -• 63 100 Large 1 mm p b 1.3 a (100) 1.14 (88) .91 (70) . 35 (28) .04 (3) 0 0 .0 F i n e 1-0.2 mm 0 0 0 .012 (.9) .11 (8) .02 (2) .16 (12) .05 (4) S e t t l e d F l o e 0. 2 mm 0 0 .02 (2) . 03 (2) .05 (4) .09 (7) .03 (2) .12 (9) S e t t l e d T o t a l 1. 3 1. 14 .93 . 39 . 20 • 11 . 19 . 17 DOM • Balance 0 ( 0 ) c .16 (12) .37 (28) .91 (70) 1.10 (85) 1.19 (92) 1.11 (85) 1.13. (87) Cedar V a l l e y Pond System D e t r i t u s Time i n days from beginning of experiment Catagory S i z e o 3 ? 13 24 41 63 100 Large 1 mm 1.0 a .93 •95 . 60 . 20 - . 03 .03 F i n e 1-0.2 mm 0 0 0 . 05 . 04 - .11 • . 11 ' S e t t l e d • Floe 0. 2 mm 0 0 . 01 . 02 . 06 - . 11 . 12 S e t t l e d T o t a l 1.0.; . 93 .96 . 67 .30 - .25 .26 DOM Balance 0 .07 . 04 .33 . 70 .75 .. 74 a. b. c. T o t a l average amount of Myriophyllum introduced i n t o system of c o n t a i n e r s Number i n b r a c k e t i s percent p l a n t r e s i d u e , i . e . percentage of a. Number i n b r a c k e t i s percent p l a n t r esidue unaccounted f o r . 56 F i n e d e t r i t u s p a r t i c l e s however, began to appear a f t e r o n l y s e v e r a l days (Figure 16) and then p e r s i s t i n r e l a t i v e l y u n i -form p r o p o r t i o n s throughout the remainder of the experiment. T h i s would suggest t h a t these f i n e d e t r i t a l fragments are of a r e f r a c t o r y nature. Moreover, i t seems t h a t i n the system s t u d i e d , the t r a n s f o r m a t i o n from p a r t i c u l a t e o r g a n i c matter (POM) to d i s s o l v e d o r g a n i c matter (DOM) i s r a t h e r immediate. That i s to say, there i s no s u b s t a n t i a l i n t e r m e d i a r y accumu-l a t i o n of l a b i l e POM Which i s then f u r t h e r processed t o DOM. Almost a l l of the l a b i l e POM i n t r o d u c e d i n t o the system as p l a n t m a t e r i a l becomes immediately a v a i l a b l e as DOM. T h i s proceeds a b i o t i c a l l y a t f i r s t by a u t o l y s i s or l e a c h i n g and l a t e r by m i c r o b i a l a c t i v i t y . Recent s t u d i e s d e a l i n g w i t h l e a f l i t t e r l e a c h i n g i n l o t i c ecosystems have shown very r a p i d i n c r e a s e s i n l a b i l e and r e -f r a c t o r y DOM immediately a f t e r dead p l a n t m a t e r i a l ( u s u a l l y d r i e d l e a f l i t t e r ) i s p l a c e d i n t o water (Wetzel and Manny 1972a Cummins e t a l . 1972, Lush and Hynes 1974). These experiments, designed t o simulate n a t u r a l autumnal l e a f - f a l l and performed i n experimental stream environments, showed n e a r l y 10 f o l d i n c e a s e s i n DOM l e v e l s w i t h i n about 2 4 hours a f t e r d r i e d l e a f l i t t e r was i n t r o d u c e d i n t o the system. P l a n t r e s i d u e g r e a t e r than 1 mm was analysed f o r t o t a l K j e l d a h l N, t o t a l P, t o t a l C, o r g a n i c content and crude p r o t e i n content (Table V). t o determine i f there were any n o t i c e a b l e T a b l e V. Changes i n n u t r i e n t q u a l i t y o f d e t r i t a l f r a c t i o n s g r e a t e r t h a n 1 mm i n : (a) Cedar V a l l e y system and (b) Iona R e s e r v o i r system. R e s u l t s shown as p e r c e n t a g e of dry w e i g h t . Days K j e l d a h l N Ortho P T o t a l C T o t a l Crude C:N R a t i o O r g a n i c P r o t e i n a . b a b a b a b a b a b 0* 3. 04 2.62 . 605 . 501 43.9 43.6 86. 7 86. 6 19. 0 16. 3 14. 4 16. 6 3 2.94 2.87 . 419 . 523 41. 3 43. 7 88. 1 85.9 18. 3 17. q 14. 0 15. 2 7 3.15 3.21 . 449 .558 44. 1 44.1 86. 3 87. 4 19. 6 20. 0 14. 0 13. 7 13 3. 34 3. 64 . 555 . 825 44.3 44.2 85. 1 - 20. 8 22. 7 13. 3 12. 1 24 3. 83 - . 385 - 46.7 - - - 23. 9 - 12. 2 -S t a n d a r d d e v i a t i o n 0. 35 . 44 1.5 1.4 1.9 . 29 1. 2 .75 - - - -C o e f f i c i e n t V a r i a t i o n 3.7 6.3 368 324 8.3 . 18 1. 7 . 64 - - -* n u t r i e n t c o n c e n t r a t i o n o f p l a n t m a t e r i a l o r i g i n a l l y i n t r o d u c e d i n t o system. en 58 changes i n t h e s e parameters w h i l e t h i s m a t e r i a l was' a v a i l a b l e . (ca. 13-24 d a y s ) . The measured v a l u e s n o t o n l y r e f l e c t t h e q u a l i t y o f the p l a n t m a t e r i a l b u t are a l s o a d i r e c t r e s u l t o f the a t t e n d a n t m i c r o o r g a n i s m s . The p l a n t r e s i d u e showed the • g r e a t e s t v a r i a t i o n s i n i t s n i t r o g e n , phosphorus and p r o t e i n c o n t e n t ; t o t a l carbon and s u r p r i s i n g l y t h e o r g a n i c c o n t e n t remained r e l a t i v e l y c o n s t a n t w i t h r e s p e c t t o o r i g i n a l l e v e l s found i n the p l a n t t i s s u e . N i t r o g e n and p r o t e i n e n r i c h m e n t o f decomposing p l a n t m a t e r i a l has been r e p o r t e d by many a u t h o r s (Odum and de l a Cruz 1967, K a u s h i k and Hynes 1971, de l a Cruz and G a b r i e l 1974 and I v e r s e n 1972) most o f whom a t t r i b u t e t h i s i n c r e a s e t o m i c r o b i a l e n r i c h m e n t . S i m i l a r i l y , p r o t e i n e n r i c h m e n t o f the l a r g e d e t r i t a l p a r t i c l e s i s q u i t e n o t i c e a b l e i n b o t h systems s t u d i e d ( F i g u r e 1,7). Crude p r o t e i n i n c r e a s e s l i n e a r l y up t o 26 and 39% above i n i t i a l l e v e l s measured i n the p l a n t t i s s u e f o r t h e Cedar V a l l e y and Iona systems, r e s p e c t i v e l y . C e r t a i n l y t h i s marked i n c r e a s e i n p r o t e i n v a l u e i s due t o t h e m i c r o b i a l e n r i c h m e n t o f t h e d e t r i t u s . In a r e c e n t s t u d y o f amino a c i d s (AA) and crude p r o t e i n CP) c o n t e n t s o f d y i n g and decomposing s a l t - m a r s h p l a n t s , de l a Cruz (19 75) found a d e c l i n e i n AA and CP on d e a t h o f marsh p l a n t s b u t an i n c r e a s e a g a i n a l m o s t t o the l e v e l o f t h e l i v i n g p l a n t s d u r i n g i n s i t u d e c o m p o s i t i o n . T h i s r e c o n s t i t u t i o n o f n u t r i t i o n a l q u a l i t y i n marsh p l a n t d e t r i t u s was a t t r i b u t e d t o 5 9 Figure 17. Percent change i n n u t r i e n t content of decomposing p l a n t m a t e r i a l greater than 1 mm r e l a t i v e to l e v e l s of o r i g i n a l l i v e p l a n t s . Iona Reservoir System .Q Cedar V a l l e y Pond System • i 9 0 3 7 13 1 J J L_ LU O < X o 10 0 I- -10 J 10 o-i 10 L U o DC LU Q. 40i 20J I T~ 0 3 r 7 24 13 24 TOTAL KJELDAHL NITROGEN TOTAL PHOSPHORUS TOTAL CARBON TOTAL ORGANIC CRUDE PROTEIN T I M E IN D A Y S 61 t h e p r e s e n c e o f s o u r c e s o f N i n t h e m a r s h . A s i m i l a r t r e n d i s s e e n i n r e s u l t s Of t h i s s t u d y w i t h t h e C e d a r V a l l e y p l a n t m a t e r i a l ( F i g u r e 1 7 ) . . The s o u r c e o f N i n t h e p o n d and r e s e r v o i r w a t e r i s t h o u g h t t o i n f l u e n c e t h e n u t r i t i o n a l e n r i c h m e n t o f t h e Myr i o p h y 1 l u m d e t r i t u s as c o l o n i z i n g m i c r o o r g a n i s m s t a k e up N e x o g e n o u s l y . The t o t a l P v a l u e o f t h e d e t r i t u s shows a r a p i d i n c r e a s e up t o 65% i n t h e I o n a s y s t e m . I n t h e C e d a r V a l l e y s y s t e m h o w e v e r , t h e p l a n t m a t e r i a l u n d e r g o e s an i n i t i a l 3 0 % d e c r e a s e i n t o t a l P f o l l o w e d b y a 16% r e c o v e r y a n d f i n a l l y b y a 2 1 % d e c l i n e a g a i n . E s s e n t i a l l y t h e r e i s a n e t l o s s o f P i n t h e l a r g e d e t r i t a l p a r t i c l e s o f t h e C e d a r V a l l e y s y s t e m . S i n c e m i c r o b i a l e n r i c h m e n t o f d e t r i t i c m a t e r i a l m a n i -f e s t s i t s e l f b y an i n c r e a s e i n t h e n u t r i e n t q u a l i t y o f t h e d e t r i t u s , i t a p p e a r s t h a t t h e l a r g e d e t r i t u s i n t h e C e d a r V a l l e y s y s t e m h a s a more d e p a u p e r a t e m i c r o f a u n a t h a n d o e s t h e I o n a d e t r i t u s . I n d e e d , t h e C e d a r V a l l e y p l a n t s l o s e 30% o f t h e i r P t h r o u g h l e a c h i n g o v e r t h e f i r s t 3 d a y s b e f o r e s u b s t a n t i a l c o l o n i z a t i o n b y m i c r o b e s t a k e s p l a c e t o p r o d u c e e n r i c h e d d e a d p l a n t m a t e r i a l . H o wever, s u b s e q u e n t t o t h e i n -i t i a l a u t o l y s i s o f t h e p l a n t m a t e r i a l , t h e m i c r o b i a l e n r i c h -ment i s n o t s u f f i c i e n t t o make up f o r t h e i n i t i a l l o s s e s due t o l e a c h i n g . T o t a l o r g a n i c a n d c a r b o n c o n t e n t m e a s u r e d i n t h e d e t r i t a l m a t e r i a l c h a n g e d v e r y l i t t l e i n e i t h e r s y s t e m ( F i g u r e 17) 62 d u r i n g t h e time the m a t e r i a l was a v a i l a b l e f o r measurement. Other s t u d i e s d e a l i n g w i t h p l a n t m a t e r i a l decomposing i n a q u a t i c e n v i r o n m e n t s , e s p e c i a l l y the work o f K a u s h i k and Hynes (1971), shows t h a t w h i l e m i c r o o r g a n i s m s i n c r e a s e t h e N and p r o t e i n c o n t e n t s In p l a n t m a t t e r , o r r e t a i n a l l the o r i g i n a l n i t r o g e n i f no e x t r a amounts are p r e s e n t i n t h e w a t e r , t h e y do not s u b s t a n t i a l l y change the t o t a l c a l o r i f i c v a l u e o f t h e p l a n t m a t e r i a l . The r e s u l t s o f t h i s s t u d y conform t o t h e g e n e r a l i t i e s d e s c r i b e d above s i n c e the g r e a t e s t v a r i a t i o n s o b s e r v e d i n the l a r g e d e t r i t a l f r a c t i o n s o c c u r r e d i n t h e t o t a l o r g a n i c P, N and crude p r o t e i n measurements, w h i l e t o t a l carbon and o r g a n i c c o n t e n t changed v e r y l i t t l e . 63 1.4 R e g e n e r a t i o n a n d m i n e r a l i z a t i o n o f p l a n t N and P Soon a f t e r t h e r a p i d d i s a p p e a r a n c e o f p l a n t m a t e r i a l g r e a t e r t h a n 1 mm, a m a r k e d i n c r e a s e o f N and P was n o t i c e d i n t h e w a t e r o f t h e c o n t a i n e r s . I n t h e I o n a s y s t e m , P ( a l m o s t e n t i r e l y o r t h o p h o s p h a t e ) r a p i d l y r e a c h e d maximum c o n c e n t r a t i o n o f c a . 6 mg/1 ( F i g u r e 1.8) i n a b o u t 40 d a y s , w h i c h a c c o u n t s f o r a p p r o x i m a t e l y 92% o f t h e t o t a l P ( m a i n l y p l a n t P) o r i g i n a l l y i n t h e s y s t e m . S u b s e q u e n t t o t h i s p e a k , amounts d e c l i n e d a b r u p t l y l e v e l l i n g o f f a t c a . 5 mg/1 u n t i l t h e e n d o f t h e e x p e r i m e n t . I n t h e C e d a r V a l l e y s y s t e m , m i n e r a l i z a t i o n r a t e s w e r e n o t as d r a m a t i c as. i n t h e o t h e r s y s t e m a n d a l t h o u g h t h e i n i t i a l t o t a l P p o o l was t h e same as i n t h e I o n a s y s t e m (6.5 mg), o n l y a b o u t 46% o f t h i s was r e g e n e r a t e d as o r t h o -p h o s p h a t e when t h e maximum was r e a l i z e d b e t w e e n c a . 40 and 60 d a y s a f t e r b e g i n n i n g o f t h e e x p e r i m e n t ( F i g u r e 1 8 ) . I n t h e C e d a r V a l l e y s y s t e m , t h e d e c l i n e i n P was o n l y m o d e r a t e a f t e r maximum c o n c e n t r a t i o n s h a d b e e n r e a c h e d . The d e c l i n e o f t h e P c o n t e n t i n t h e w a t e r e s p e c i a l l y e v i d e n t i n t h e I o n a s y s t e m c a n be a c c o u n t e d f o r e i t h e r b y a d i r e c t e x o g e n o u s u p t a k e o f d i s s o l v e d P compounds b y b a c t e r i a a s s o c i a t e d w i t h t h e f i n e d e t r i t a l m a t t e r o r by t h e a d s o r p t i o n o f P compounds t o t h e s e f i n e o r g a n i c f r a c t i o n s . E i t h e r way, P r e m o v e d f r o m t h e s u p e r n a t a n t w o u l d s e t t l e o u t w i t h t h e f l o c c u l a n t o r g a n i c m a t t e r t o t h e b o t t o m o f t h e I m h o f f c o n e s . 6 4 F i g u r e 18. Changes i n phosphorus c o n t e n t of water d u r i n g c o u r s e of e x p e r i m e n t . T o t a l Phosphorus Orthophosphate o 65 C E D A R V A L L E Y P O N D S Y S T E M I O N A R E S E R V O I R S Y S T E M 0 20 40 60 80 100 T I M E I N D A Y S 66 One o f the i n t e r e s t i n g r e s u l t e v i d e n t from t h e s e d a t a i s t h a t almost a l l o f the r e g e n e r a t e d P i s i n the form o f or t h o p h o s p h a t e ( d i s s o l v e d i n o r g a n i c P ) . Much o f t h e p a r t i -c u l a t e P s e t t l e d out d u r i n g the 6 hour s e t t l i n g p e r i o d a l l o w e d b e f o r e t h e s u p e r n a t a n t was sampled. However, r a p i d m i n e r a l i -z a t i o n r a t e s and h i g h b a c t e r i a l a c t i v i t y would c e r t a i n l y a l s o c o n t r i b u t e t o the e f f i c i e n t breakdown o f suspended 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 P. compounds t o t h e i r s t a b l e i n o r g a n i c form. A l t h o u g h the g e n e r a l p r o c e s s o f P r e g e n e r a t e d from m i l -f o i l i s v e r y s i m i l a r i n b o t h systems s t u d i e d , i n t h a t 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 P i s e f f i c i e n t l y and r a p i d l y m i n e r a l i z e d t o d i s s o l v e d i n o r g a n i c form, one major d i f f e r e n c e i s e v i d e n t . B oth t h e r a t e , and e s p e c i a l l y t h e magnitude, of r e g e n e r a t e d P i s much g r e a t e r i n t h e Iona system. Here, about t w i c e as much p l a n t P i s m i n e r a l i z e d t h a n i n t h e Cedar V a l l e y system. . The major f a c t o r a c c o u n t i n g f o r t h i s d i f f e r e n c e e v i d e n t i n t he r e s u l t s ( F i g u r e 18) i s t h e much g r e a t e r p o o l o f N a v a i l a b l e i n the w a t e r from the Iona r e s e r v o i r . T h i s ex-p l a n a t i o n i s c e r t a i n l y c o m p a t i b l e w i t h t h e g e n e r a l i t i e s e v i d e n t i n much o f t h e work done on p l a n t d e g r a d a t i o n i n a q u a t i c ecosystems d i s c u s s e d e a r l i e r . T o t a l K j e l d a h l N r e g e n e r a t e d from t h e p l a n t m a t e r i a l r a p i d l y reached maximum l e v e l s o f 15.9 mg/1 a f t e r 24 days i n t h e Iona system and 11.0 mg/1 a f t e r 41 days i n the Cedar 67 V a l l e y system (Figure 19). Maximum regenerated TKN accounts f o r about 43% and 35% of the o r i g i n a l t o t a l N pool of the Iona and Cedar V a l l e y system r e s p e c t i v e l y . P l a n t m a t e r i a l makes up 92% of t h i s t o t a l N pool i n the former and 9 8% i n the l a t t e r system. That i s , most of the N evident i n the water i s regenerated p l a n t N. Furthermore, the magnitude of and d i f f e r e n c e between the two systems w i t h respect to t h e i r N regeneration i s not as great as f o r P regeneration. Although regenerated N appears somewhat sooner i n the water than does regenerated P, the o v e r a l l m i n e r a l i z a t i o n of organic N compounds i s not as great as t h a t of organic P compounds. N i t r i f i c a t i o n of ammonia i s not s i g n i f i c a n t u n t i l immediately a f t e r maximum TKN l e v e l s have been a t t a i n e d . I t i s then t h a t NO^-N increases r a p i d l y , reaching maximum l e v e l s at the end of the experiment of 10.7 mg/1 and 17.4 mg/1 i n the Cedar V a l l e y and Iona systems , r e s p e c t i v e l y . The d e c l i n e i n TKN a f t e r maximum concentrations have been reached i s mainly due to an increase i n the m i n e r a l i z a t i o n of suspended p a r t i c u l a t e and d i s s o l v e d organic N and ammonia, most of which i s transformed to NO2"" and to NO3-. The t r a n s f o r m a t i o n of p a r t i c u l a t e and d i s s o l v e d organic compounds to t h e i r o x i d i z e d d i s s o l v e d i n o r g a n i c form, appears to occur immediately w i t h organic P compounds; however, t h i s process r e q u i r e s a much longer time f o r organic N compounds as i s evident from the r e s u l t s of t h i s study. 68 F i g u r e 19. Changes i n n i t r o g e n c o n t e n t o f w a t e r d u r i n g c o u r s e o f e x p e r i m e n t . T o t a l K j e l d a h l N i t r o g e n N i t r a t e o CEDAR VALLEY POND SYSTEM IONA RESERVOIR SYSTEM T I M E I N D A Y S 70 One o f t h e major re a s o n s f o r t h i s l a g p e r i o d b e f o r e N O 3 -b e g i n s t o appear i s t h a t s p e c i a l i z e d c h e m o l i t h o t r o p h i c b a c t e r i a p o p u l a t i o n s , (eg. N i t r o s o m a s ) have t o become e s t a b l i s h e d b e f o r e n i t r i f i c a t i o n t a k e s p l a c e . Moreover, o r g a n i c N compounds (eg. p r o t e i n s ) have t o be deaminated u n t i l a s u f f i c i e n t s t o r e o f ammonia i s a v a i l a b l e f o r t h e n i t r i f i c a t i o n p r o c e s s t o t a k e p l a c e . S i m i l a r s t u d i e s d e a l i n g w i t h t h e N and P r e g e n e r a t i o n from d e c a y i n g a q u a t i c p l a n t s under l a b o r a t o r y c o n d i t i o n s are t h o s e o f J e w e l l (1971) and N i c h o l s and Keeney (1973). The former work showed t h a t decomposing C a l l i t r i c h e sp. (water s t a r w o r t ) r a p i d l y r e g e n e r a t e d s o l u b l e P wh i c h r e a c h e d maximum l e v e l s between 20 and 40 days a f t e r p l a n t s were p l a c e d i n complete d a r k n e s s under a e r o b i c c o n d i t i o n s . S o l u b l e N was r e g e n e r a t e d a t a somewhat s l o w e r r a t e r e a c h i n g maximum l e v e l s around 40 days. The r e s u l t s o f N i c h o l s and Keeney (1973) show a r a p i d r e l e a s e o f P from decomposing M y r i o p h y l l u m e x a l b e s c e n s ( a q u a t i c m i l f o i l ) , where t o t a l P reaches a maximum a f t e r about 56 days i n a darkened a e r o b i c system. O r g a n i c N rea c h e s a peak a f t e r about 14 days f o l l o w e d by a s h a r p d e c l i n e and N O 3 - N b e g i n s t o i n c r e a s e a f t e r about 80 days r e a c h i n g maxi-mum l e v e l s o n l y a f t e r c a . 120 days. B a s i c a l l y , r e s u l t s and t r e n d s o f N and P r e g e n e r a t i o n from decomposing M y r i o p h y l l u m i n t h i s s t u d y a re c o m p a t i b l e t o the l i t e r a t u r e r e s u l t s d e s c r i b e d above. 71 The c l o s e s i m i l a r i t y between p l o t t e d r e s u l t s o f N and P r e g e n e r a t i o n o f the Iona and Cedar V a l l e y systems demonstrates t h a t t h e o v e r a l l v a r i a b i l i t y o f the e x p e r i m e n t a l r e s u l t s was low and t h a t r e s u l t s o f b o t h systems can be compared w i t h a good degree o f c o n f i d e n c e . 72 2. F i e l d E x p e r i m e n t 2.1 I n i t i a l n u t r i e n t c o n t e n t and c h a r a c t e r i s t i c s 2.1.1 M y r i o p h y l l u m s p i c a t u m As i n t h e p r e v i o u s l a b o r a t o r y e x p e r i m e n t , a f u l l i n v e s t i -g a t i o n o f t h e m i l f o i l p l a n t t i s s u e was f i r s t u n d e r t a k e n . T h i s i n c l u d e d an e s t i m a t e "of s t a n d i n g c r o p t o d e t e r m i n e t h e amount o f p l a n t m a t e r i a l i n t h e d e s i g n a t e d e n c l o s u r e s . On t h e b a s i s o f 7 s a m p l i n g s o f 0.5 m.2 i n t h e l i t t o r a l z o n e , t h e mean s t a n d i n g c r o p ( d r y w t ) e n c l o s e d by a c y l i n d e r was 50.5 g/m 2 ±1.44 (±1 s t a n d a r d e r r o r ) ; s e e T a b l e V I . S t a n d i n g c r o p d a t a r e p o r t e d i n t h e l i t e r a t u r e r a n g e s f r o m a b o u t 11 t o 680 g/m2, d r y w e i g h t ( W e s t l a k e 1 9 6 3 , R i c h e t a l . 1 9 7 1 , K u l l b e r g 1974, E d w a r d s a n d Owen 19 6 0 , Chapman e t a l . 1974 and L a t h w e l l e t a l . 1 9 7 3 ) . T h e s e d a t a a r e b a s e d on v a r i o u s m i x e d as w e l l as s i n g l e s p e c i e s o f s u b m e r g e d a q u a t i c m a c r o p h y t e s s t u d i e d i n a d i v e r s i t y o f a q u a t i c h a b i -t a t s . A l t h o u g h t h e s t a n d i n g c r o p o f M y r i o p h y l l u m m e a s u r e d i n t h i s s t u d y i s l e s s t h a n v a l u e s o b t a i n e d by o t h e r s f o r some v e r y p r o d u c t i v e a q u a t i c p l a n t s , M y r i o p h y l l u m s p i c a t u m c a n n e v e r t h e l e s s p r o d u c e a l a r g e b i o m a s s p e r u n i t a r e a . R e c e n t i n v e s t i g a t i o n s by N e w r o t h ( p e r s o n a l c o m m u n i c a t i o n ) h a v e shown t h a t M y r i o p h y l l u m s p i c a t u m g r o w i n g t o n u i s a n c e l e v e l s i n p a r t s o f t h e Okanagan l a k e s i n s o u t h c e n t r a l B r i t i s h C o l u m b i a c a n r e a c h s t a n d i n g c r o p l e v e l s more t h a n t e n t i m e s T a b l e V I , R e p l i c a t e - samples o f % m s t a n d i n g crop o f M y r i o p h y l l u m h a r v e s t e d a d j a c e n t t o e x p e r i m e n t a l e n c l o s u r e s . S t a n d i n g c r o p g d r y wt/0.5 m S t a n d a r d C o e f f i c i e n t S t a n d a r d Mean D e v i a t i o n o f V a r i a t i o n E r r o r 1. 29.10 2. 20. 65 3. 21.55 4. 23.55 5. 24.65 6. 26.20 7. 31. 05 25.25*. 3.81 15 1.44 * Average s t a n d i n g crop o M y r i o p h y l l u m = 50.5 g/m 74 g r e a t e r t h a n t h o s e found i n t h i s s t u d y . Subsamples from t h e 7 r e p l i c a t e p l a n t samples were a n a l y s e d i n d u p l i c a t e t o o b t a i n i n f o r m a t i o n about t h e macro-n u t r i e n t c o n t e n t o f t h e M y r i o p h y l l u m i n t h e e x p e r i m e n t a l e n c l o s u r e s . The r e s u l t s show (Table V I I ) t h a t b o t h N and P had i n c r e a s e d s i n c e the p l a n t s were l a s t i n v e s t i g a t e d i n June 1974 (Table I ) . A f u r t h e r comparison shows a d e c r e a s e i n carbon and o r g a n i c c o n t e n t . These d i f f e r e n c e s range from about 10-40 p e r c e n t . I t s h o u l d be n o t e d however t h a t l a r g e r amounts o f p l a n t m a t t e r were sampled i n October (50.5 g) t h a n i n June (ca.1 g ) , 1974, w h i c h i s r e f l e c t e d by t h e s m a l l e r v a r i a b i l i t y i n the former d a t a . I n any c a s e , t h e i n f o r m a t i o n from T a b l e V I I p r o v i d e s t h e b a s i s f o r c a l c u l a t i n g t h e t o t a l N and P p o o l s t i e d up i n t h e M y r i o p h y l l u m g r o w i n g i n t h e Iona r e s e r v o i r . Other t h a n the a n a l y s e s o f the October samples, w h i c h r e p r e s e n t t h e q u a l i t y o f a q u a t i c p l a n t s w i t h i n the e n c l o s u r e s a t t h e s t a r t o f the e x p e r i m e n t , no f u r t h e r measurements were made on the e n c l o s e d p l a n t s o v e r t h e 7 0 day d u r a t i o n o f the e x p e r i m e n t . However, o b s e r v a t i o n s on the M y r i o p h y l l u m growing i n t h e l i t t o r a l a r e a o u t s i d e t h e e x p e r i m e n t a l e n c l o s u r e s r e v e a l e d an e x t e n s i v e d i e - o f f o f the a q u a t i c p l a n t community toward t h e end o f November,1974. T h i s o c c u r r e d about 50 days a f t e r the f i e l d e x p e r i m e n t was s t a r t e d . . T a b l e V I I . Average n u t r i e n t c o n t e n t o f M y r i o p h y l l u m e n c l o s e d i n e x p e r i m e n t a l c y l i n d e r s . R e s u l t s based on 7 r e p l i c a t e measures. Average N u t r i e n t . C o n t e n t S t a n d a r d C o e f f i c i e n t N u t r i e n t P e r c e n t d r y wt •Range D e v i a t i o n V a r i a t i o n Carbon . 38.4 ±0.3 37.8 - 39.3 .803 2.1 N i t r o g e n 3.75 ±0. 06 2.96 - 3.47 . 180 4.8 Phosphate* . 544 ±0.01 .514 - .573 .027 4.9 T o t a l O r g a n i c s 78. 3 ±0.6 76. 0 - 80.3 1. 50 1.9 P r o t e i n 24. 0 ±0.4 - 1. 12 4.8 * P e r c e n t T o t a l P = 0.225 ±1 s t a n d a r d e r r o r 76 2.1.2 R e s e r v o i r w a t e r a n d b i o t a R e s u l t s o f c h e m i c a l a n a l y s e s o f t h e r e s e r v o i r w a t e r i n O c t o b e r , 197 4 show t h a t t h e n u t r i e n t l e v e l s h a d i n c r e a s e d s u b -s t a n t i a l l y d u r i n g t h e p r e v i o u s two months ( T a b l e V I I I ) . TKN a n d t o t a l P c o n c e n t r a t i o n s w e re 5 and 2 4 t i m e s g r e a t e r r e s p e c t i v e l y . The l a r g e i n c r e a s e i n n u t r i e n t s r e s u l t e d i n a v e r y d e n s e a l g a e b l o o m w h i c h c o n s i s t e d a l m o s t e n t i r e l y o f t h e b l u e g r e e n a l g a e A n a b a e n a s p i r u l a . The f a c t t h a t b o t h p l a n t s a n d a l g a e w e r e 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 i s r e f l e c t e d by t h e h i g h pH l e v e l s a n d s u p e r -s a t u r a t e d d i s s o l v e d o x y g e n c o n c e n t r a t i o n s ( T a b l e V I I I ) . The l o w c o n c e n t r a t i o n s o f ammonia, NO~3/NO~2~ N a n & o r t h o P i n d i c a t e t h a t l i t t l e b r e a k d o w n a nd m i n e r a l i z a t i o n o f o r g a n i c m a t t e r h a d o c c u r r e d i n t h e w a t e r o f t h e r e s e r v o i r up t o t h e t i m e o f m e a s u r e m e n t i n O c t o b e r , 1974. I t seems t h e n t h a t t h e r e s e r v o i r was u n d e r g o i n g one l a s t p u l s e o f a u t u m n a l p r i m a r y p r o d u c t i o n . A t t h e same, t i m e , s a m p l e s c o l l e c t e d f o r b a c t e r i a r e v e a l e d a t o t a l a v e r a g e c e l l c o u n t o f 1.85 X IO** c e l l s / m l ±10% (±95% c o n f i d e n c e i n t e r v a l ) . M o s t b a c t e r i a w e r e o f l a r g e r o d - s h a p e d c e l l s w i t h l e s s t h a n h a l f as many c o c c o i d f o r m s , some o f w h i c h w e r e b a r e l y v i s i b l e ( p r o b a b l y l e s s t h a n 1 urn i n s i z e ) . D u r i n g t h e p e r i o d i c s a m p l i n g , s m a l l i n v e r t e b r a t e s , p a r t o f t h e l i t t o r a l r e s e r v o i r c o m m u n i t y , w e r e o b s e r v e d w i t h i n t h e 77 T a b l e V I I I . . Q u a l i t y o f r e s e r v o i r .water e n c l o s e d by e x p e r i m e n t a l c y l i n d e r s on October 1,1974, compared t o d a t a o f August 6, 1974. Temperature, C 14.0 pH 9.8 D i s s o l v e d O2, mg/1 16.1 N u t r i e n t s O ctober 1 mg/1 August 6 mg/1 * A l k a l i n i t y 60.7 Ammonia .069 N i t r a t e . 02 • .20 N i t r i t e .006 K j e l d a h l N 13. 5 2.8 0 T o t a l P .549 . 023 Ortho P . 012 < . 003 * as mg/1 CaC0 3 78 e x p e r i m e n t a l e n c l o s u r e s . S m a l l l i m n a e i d s n a i l s a ppeared, a t t a c h e d t o t h e i n s i d e o f t h e e n c l o s u r e s a t the water s u r f a c e , p r o b a b l y because of t h e low d i s s o l v e d oxygen l e v e l s under the w a t e r . Other i n v e r t e b r a t e s n o t i c e d i n s i d e t h e c y l i n d e r s were t h e common backswimmer ( N o t o n e c t i d a e ) and t h e t h r e e s p i n e s t i c k l e b a c k ( G a s t e r o s t e u s a c u l e a t u s ) . F i n a l l y , t h e i n i t i a l amount of v a r i o u s N and P n u t r i e n t p o o l s i n t h e c y l i n d e r s ' w a t e r column c o n t a i n i n g p l a n t s were c a l c u l a t e d (Table I X ) . T o t a l p l a n t N and P were c a l c u l a t e d by m u l t i p y l i n g t h e N and P c o n t e n t (3.75 and 0.225%) by t h e t o t a l average s t a n d i n g c r o p 50.5 g d r y wt. C a l c u l a t i o n s o f b a c t e r i a l n u t r i e n t s were based on l i t e r a t u r e v a l u e s f o r average b a c t e r i a d r y w e i g h t s (2 X 1 0 - - ^ g) and N and P con-t e n t s (15 and 1%) (Doetsch and Cook 1973) w h i c h was m u l t i -p l i e d by t h e t o t a l c e l l c ount (1.85 X 1 0 6 c e l l s . m l ) . T o t a l o r g a n i c n i t r o g e n (TON = 13.5 mg/1) and T o t a l o r g a n i c phos-phorus (TOP - .537 mg/1) of t h e w a t e r , minus the c a l c u l a t e d suspended b a c t e r i a l N and P was used as a v a l u e f o r t o t a l suspended p a r t i c u l a t e m a t t e r . S i n c e a l g a e were i n such g r e a t abundance a t t h e t i m e , by f a r t h e g r e a t e s t amount of TON and TOP i n t h e water would be due t o a l g a e ( l a r g e l y Anabaena  s p i r u l a ) . The d i s s o l v e d i n o r g a n i c P p o o l i s s i m p l y t h e phosphate measure c o n v e r t e d t o P. The t o t a l d i s s o l v e d i n -o r g a n i c N p o o l i s t h e sum of NH-j as N =16.9 mg, NO3 as N= 1.4 mg and NO2 as N = 0.5 mg. . The v a s t amount of n i t r o g e n t i e d up i n t h e Anabaena i s Table IX, T o t a l amount of N and P t i e d up i n various components w i t h i n water column of enclosures at s t a r t i n g c o n d i t i o n . N u t r i e n t Pool T o t a l mg Nitrogen T o t a l mg Phosphorus Aquatic P l a n t s 1893 114 Suspended B a c t e r i a 17 1 T o t a l Suspended P a r t i -c u l a t e (Mainly Algae) 4033 160 D i s s o l v e d i n o r g a n i c 19 1 T o t a l i n water column 596 2 mg 27 6 mg 80 D I S S O L V E D D I S S O L V E D N I T R O G E N P H O S P H O R U S 5 9 6 2 mg 2 7 6 mg F i g u r e 20. P r o p o r t i o n o f N and P t i e d up i n v a r i o u s components w i t h i n w a t e r column o f e n c l o s u r e s a t s t a r t i n g c o n d i t i o n s . 81 q u i t e e v i d e n t f r o m F i g u r e 20. N o t o n l y t h e l a r g e b i o m a s s o f t h e a l g a e , b u t a l s o t h e a b i l i t y o f t h i s b l u e - g r e e n a l g a e t o f i x a t m o s p h e r i c N s h o u l d e x p l a i n t h e l a r g e (67%) p r o p o r t i o n o f N t i e d up. W i t h P h o w e v e r , t h e s i t u a t i o n was somewhat d i f -f e r e n t . H e r e , i n s p i t e o f t h e l a r g e amount o f a l g a e , t o t a l P t i e d up i n m a c r o p h y t e s a p p r o a c h e d t h a t f o u n d i n a l g a e . D i s s o l v e d N a n d P was v e r y l o w w h i c h r e - e m p h a s i z e s t h e f a c t t h a t t h i s a v a i l a b l e n u t r i e n t was i m m o b i l i z e d by p l a n t a n d a l g a e t i s s u e d u r i n g t h e h i g h r a t e o f p h o t o s y n t h e s i s o c c u r r i n g i n t h e r e s e r v o i r a t t h e t i m e o f m e a s u r e m e n t . 2.1.3 R e s e r v o i r s e d i m e n t R e a l i z i n g t h e i m p o r t a n c e o f t h e r e s e r v o i r s e d i m e n t a s b o t h a s o u r c e a n d s i n k f o r n u t r i e n t s , r e p l i c a t e c o r e - s a m p l e s w e r e o b t a i n e d c l o s e t o t h e a r e a o f t h e e n c l o s u r e s . F i v e s a m p l e s o f c a . 8-10 cm s e d i m e n t d e p t h a n d 80-160 m l s e d i m e n t v o l u m e were t a k e n f r o m a s m a l l a r e a o f t h e r e s e r v o i r b o t t o m . O t h e r c o r e s a m p l e s r e v e a l e d t h a t t h e r e s e r v o i r b o t t o m o f t h e s t u d y s i t e c o n s i s t e d o f a r i c h , b l a c k , o r g a n i c l a y e r o f mud c a . 25-30 cm d e e p , o v e r l y i n g a l m o s t p u r e s a n d . C h e m i c a l a n a l y s e s o f t h e s e d i m e n t s a m p l e s c o n f i r m e d t h a t t h e s u r f a c e l a y e r o f mud was h i g h l y o r g a n i c a n d r i c h i n n u t -r i e n t s ( T a b l e X ) . The a v e r a g e t o t a l v o l a t i l e c o n s t i t u e n t o f t h e mud was 94.5%. A v e r a g e v a l u e s f o r o r g a n i c c a r b o n , TKN and TP w e r e 19.8, 2.62 a n d 0.768 mg/1, r e s p e c t i v e l y . T h e s e r e s u l t s w e r e somewhat h i g h e r t h a n n u t r i e n t v a l u e s o f s e v e r a l s e d i m e n t s a m p l e s i n a T e x a s r e s e r v o i r ( H e n d r i c k s a n d S i l v e r y 1973). T a b l e X. C h e m i c a l c o m p o s i t i o n o f r e s e r v o i r s u r f a c e sediment a d j a c e n t t o s t u d y s i t e . R e p l i c a t e Sample P e r c e n t O r g a n i c T o t a l T o t a l Samples Volume T o t a l Carbon K j e l d a h l Phosphorus V o l a t i l e N i t r o g e n ml mg/g mg/g mg/g 1. 160 93.6 25. 4 3.26 0.858 2. 140 9 4.9 18. 3- 2.50 0.755 3. 80 95.4 17. 3 2. 21 0. 716 4. 160 93. 8 21.8 2. 89 0.793 5. 160 95.1 16. 2 2.26 0.720 Mean V a l u e s 94.5 19.8 2. 62 0.768 83 2.2 Temperature, pH and d i s s o l v e d oxygen I n most c a s e s , t h e t e m p e r a t u r e measured b o t h i n s i d e and o u t s i d e the e n c l o s u r e s was v e r y s i m i l a r (Table X I ) . However, wa t e r i n s i d e the c o n t a i n e r s d i d r e q u i r e a n o t i c e a b l y l o n g e r p e r i o d t o warm and c o o l t h a n d i d t h e s u r r o u n d i n g s u r f a c e w a t e r . The l o n g - t e r m e f f e c t o f s m a l l t e m p e r a t u r e changes p r o b a b l y was n e g l i g i b l e . I n i t i a l l y t h e h i g h pH v a l u e s (9.8) o f the w a t e r were enhanced by the h i g h r a t e s o f p h o t o s y n t h e s i s o f p l a n t s and a l g a e . These r e l a t i v e l y h i g h pH v a l u e s (8.6 - 10.8) i n t h e r e s e r v o i r w a t e r o u t s i d e the c y l i n d e r s were m a i n t a i n e d t h r o u g h -out t h e 70 d a y - p e r i o d t h a t t h e w a t e r was m o n i t o r e d (Table X I ) . U n doubtedly, the pH o f the r e s e r v o i r w a t e r was a l s o governed by t h e h i g h t o t a l a l k a l i n i t y (60.7 mg/1). I n s i d e t h e c y l i n d e r s , the pH d e c l i n e d s h a r p l y soon a f t e r t h e e x p e r i m e n t was s t a r t e d . P h o t o s y n t h e s i s ceased and de-c o m p o s i t i o n w i t h i t s a c i d i c b y p r o d u c t s began w h i c h s t a r t e d t o consume some o f t h e a v a i l a b l e bases i n the w a t e r . However, because the r e s e r v o i r w a t e r was so h i g h l y b u f f e r e d , c o n d i t i o n s i n s i d e the c y l i n d e r s n e v e r became v e r y a c i d i c . The p e c u l i a r i n c r e a s e i n pH a f t e r 50 days b o t h i n s i d e and o u t s i d e o f the e n c l o s u r e s was c o i n c i d e n t a l t o the h i g h e s t v a l u e s i n a l -k a l i n i t y . D i s s o l v e d oxygen o u t s i d e t h e c y l i n d e r s was a t s a t u r a t e d l e v e l s up t o about 36 days a f t e r t h e b e g i n n i n g o f the e x p e r i -84 Table XI. Changes i n temperature, pH, and d i s s o l v e d oxygen i n s i d e and outside of enclosures during course of experiment. Time i n days a f t e r beginning of experiment 5 1 0 - 1 5 22 36 50 70 S i t e : TEMPERATURE C Outside 14 . 0 11 . 0 12. 5 12. 5 9.0 9.5 6.0 7. 0 A,B,C, and D 14. . 0 12, . 5 12. 0 12. 5 9.0 9.5 6.0 7. 0 S i t e PH Outside 9, , 8 9. , 9 8.7 9.3 . 8 . 6 - 10. 8 8. 0 A 9. , 8 6. ,9 7.6 6. 4 6.2 - 10. 7 7. 3 B 9. , 8 6. 9 7.6 6.5 6.6 - 10. 0 7. 5 C 9. ,8 • 6. 9 7.6 6.5 6.6 7.9 7. 5 D 9. ..8 6. 9 7.8 6.5 6. 5 -' 8.2 7. 5 S i t e DISSOLVED OXYGEN (ppm) (* saturated l e v e l s ) Outside 16. 1* 18. 3* 10 .7* 12. 0* • 11 .9* 12. 4* 10.0 10. 6 A 16. 1* 1. 8 0. 8 <0. 5 <0. 5 0.5 1.5 0. 7 E 16. 1* 3. 6 0.8 <0. 5 <0.5 0.8 2.5 4. 3 C .16. 1* 2. 4 0.8 <0. 5 <0. 5 1.8 1. 5 2. 8 D 16. 1* 2. 8 0.8 <0.5 <0. 5 0.2 1.1 5. 2 85 ment (October, 1974). At the 50^day sampling time, extensive d i e - o f f of the aquatic p l a n t s was n o t i c e d i n the r e s e r v o i r . This obvious decrease i n photosynthesis was evident i n the d i s s o l v e d oxygen ( DO ) l e v e l s which were below s a t u r a t i o n during and a f t e r the 50 day sampling time. DO l e v e l s i n -s i d e the c y l i n d e r s r a p i d l y d e c l i n e d to below 1 ppm a f t e r about 10 days. Although DO l e v e l s were not reduced to zero, the c y l i n d e r s were considered e s s e n t i a l l y anaerobic from between day 10 t o day 36. A f t e r about 36 to 5.0 days, DO l e v e l s s t a r t e d to r i s e again suggesting t h a t most of the o x i d i z a b l e organic matter had been m i n e r a l i z e d and t h a t the BOD was s u b s t a n t i a l l y decreasing. The d i f f e r e n c e s i n DO l e v e l s between the various enclosures showed t h a t DO. l e v e l s were lov/est i n those c y l i n d e r s which had e i t h e r or both sediment and p l a n t s i n them. Obviously the l a r g e r amount of organic matter imposed a greater BOD on the system. 2.3 T o t a l a l k a l i n i t y By f a r the g r e a t e s t increase i n a l k a l i n i t y was due mainly to the sediment w i t h i n the experimental enclosures (Table XII and Figure 21). There was a n o t i c e a b l e increase i n a l k a l i n i t y due to the breakdown of p l a n t s and algae, although the p l a n t s themselves d i d not contribute' s i g n i f i c a n t l y . H o w e v e r , W i t h i n the T a b l e X I I . Changes i n t o t a l a l k a l i n i t y c o n t e n t o f water i n s i d e arid o u t s i d e o f e n c l o s u r e s d u r i n g c o u r s e o f experiment. TOTAL ALKALINITY (as mg/1 CaCOv) Time i n days a f t e r b e g i n n i n g o f experiment S i t e 0 5 10 15 22 36 50 70 O u t s i d e 60. 7 60. 0 59. 5 61. 4 62.5 65. 5 66.8 65.5 A 60. 7 67.9 71. 6 84.5 101 122 133 148 B 60. 7 62.8 65. 2 72.6 80.8 86.5 89. 7 86. 3 C 60. 7 62.0 63. 4 73.3 84.5 90. 5 94.3 95.3 D 60. 7 68.7 75 78.9 88. 4 175 130 155 87 F i g u r e 21. T o t a l a l k a l i n i t y (CaC0 3) i n wa t e r o f e x p e r i m e n t a l f i e l d e n c l o s u r e s . P l o t t e d d a t a a r e combined t o show e f f e c t o f a q u a t i c macrophytes and-or sediment i n . c h a n g i n g w a t e r c h e m i s t r y . A A 88 89 c y l i n d e r s , the c o n t r i b u t i o n of the pediment to t o t a l a l k a l i n i t y was p r o p o r t i o n a t e l y much greater. E v i d e n t l y , i n anaerobic water, s a l t s of weak acids such as a c e t i c , p r o p i o n i c and h y d r o s u l f u r i c may be produced and would a l s o c o n t r i b u t e t o a l k a l i n i t y (Sawyer and McCarty 1967). Moreover, not only a l k a l i n e e a r t h but ferrous and manganous bicarbonates a l s o may d i f f u s e from the sediments r a i s i n g a l k a l i n i t y (Hutchinson 1957). I t seems tha t under c o n d i t i o n s where an oxygen d e f i c i t occurs, the sediment w i l l c o n t r i b u t e by f a r a greater amount of a l k a l i n i t y than w i l l the decompos-ing organic matter i n the water column above i t . Notice that the a l k a l i n i t y of the surface water of the r e s e r v o i r outside of the c y l i n d e r increased only s l i g h t l y (Table X I I ) , where of course DO l e v e l s were always high (greater than 10 mg /1). The increase i n t o t a l a l k a l i n i t y evident i n the c y l i n d e r s not exposed to the sediment was probably due mainly t o the l a r g e amounts of f r e e CO2 that entered the water as a r e s u l t of the high r e s p i r a t o r y a c t i v i t y of decomposer microorganisms. This added amount of CO2, along w i t h the o v e r a l l d e c l i n e i n pH, would have d i s s o l v e d more a l k a l i n e p r e c i p i t a t e s present i n the water (such as CaCO-j) thereby i n c r e a s i n g t o t a l a l k a l i n i t y . In any case, the o v e r a l l c o n c l u s i o n from the t o t a l a l -k a l i n i t y r e s u l t s of the experimental enclosures i s t h a t the aquatic p l a n t s had a very n e g l i g i b l e e f f e c t . The sediment on the other hand was most important i n c o n t r i b u t i n g to the t o t a l 90 a l k a l i n i t y o f the system.. 2.4 Regenerated n i t r o g e n W i t h the a i d o f a computer, r e s u l t s o f n u t r i e n t regener a c -t i o n were i n t e g r a t e d o v e r the time o f the e x p e r i m e n t (70 days) and d i v i d e d by 7 0 t o g i v e an average r a t e o f p r o d u c t i o n o f r e g e n e r a t e d n u t r i e n t s i n yUg o r mg/l/day. By t a k i n g t h e d i f f e r e n c e o f t h e t o t a l i n t e g r a t i o n s o f t h e v a r i o u s c u r v e s , as t h e y a r e p l o t t e d i n F i g u r e s 22 and 25, r e s u l t s show the c o n t r i b u t i o n o f t o t a l n u t r i e n t s i n the e x p e r i m e n t a l systems due t o : 1) the p l a n t s o n l y , 2) t h e sediment o n l y 3) the sediment and p l a n t s and 4) the wa t e r o n l y (presumably due t o the Anabaena). 2.4.1 Ammonia I n i t i a l l y , n e a r l y a l l o f t h e n i t r o g e n (99%) i n t h e w a t e r o f t h e c y l i n d e r s was i n p a r t i c u l a t e o r d i s s o l v e d o r g a n i c form. A f t e r t h e e x p e r i m e n t was s t a r t e d , ammonia N i n c r e a s e d r a p i d l y i n each c y l i n d e r d u r i n g the f i r s t 10 days from an i n i t i a l c o n c e n t r a t i o n o f 60 jx g/1.Ammonia t h e n i n c r e a s e d a t a de-c r e a s i n g r a t e d u r i n g the n e x t e i g h t weeks and r e a c h e d m a x i -91 mum con c e n t r a t i o n s , about 130 to 200 times the o r i g i n a l l e v e l , a f t e r 70 days., (Figure 22) . Almost a l l of the d i s s o l v e d and p a r t i c u l a t e organic N that was m i n e r a l i z e d , appeared as ammonia N since l e v e l s of NC>3/NO~-N remain low and unchanged during the 7 0 days i n a l l enclosures (Table X I I I ) . At the end of the experiment, 18% of the N i n the water was p a r t i c u l a t e and d i s s o l v e d organic N and 82% was i n o r g a n i c N (NH3-N) f o r the c y l i n d e r s exposed to the sediment. In the remaining two c y l i n d e r s closed to the sediment TKN and NH3-N a f t e r 70 days were ca. 32% and 68% r e s p e c t i v e l y of the t o t a l N i n the water. The g r e a t e s t source of t h i s ammonia was from the water i t s e l f ; from the deamination of organic N i n the algae. Over the study p e r i o d of 70 days, ammonia was regenerated by the algae at an average r a t e of 5.6 mg/l/day (Table XIV). . Regeneration r a t e s of ammonia f o r the aquatic p l a n t s were ten times l e s s (0.3 and 0.5 mg/l/day) than the average r a t e s f o r algae. Moreover, regeneration rates due to the sediment was a l s o considerably greater (1.82 and 2.08 mg/l/day) than the p l a n t regeneration r a t e s . S l i g h t l y higher values of regenerated ammonia were observed i n the plant-sediment c y l i n d e r s than i n those c y l i n d e r s where p l a n t s and sediment occurred alone (Table XIV). P l a n t s rooted i n the sediment showed s l i g h t l y higher r a t e s of NH^-N regeneration probably because of t h e i r p r o x i m i t y to T a b l e X I I I . C h a n g e s i n N i t r a t e and N i t r i t e (shown i n b r a c k e t s ) c o n t e n t o f w a t e r i n s i d e and o u t s i d e o f e n c l o s u r e s d u r i n g c o u r s e o f experiment. .'NO-.-N- and (NC 2~N) i n Mg/1 Time i n days a f t e r b e g i n n i n g o f experiment S i t e 0 5 10 15 22 36 50 70 O u t s i d e 20 (6) 20 (5) 20 (5) 20 (5) 20 (5) 40 (5) 40 (11) A 20 (6). 2 0 (5) 20 (5) 20 (5) 20 (5) 20 (5) 20 (5) B 20 (6) 20 (12) 20 (5) 20 (5) 20 (5) 20 (5) 20 (11) C 20 (6) 20 (7) 20 (5) 20 (5) 20 (6) 20 (5) 20 (9) D 20 (6) 20 (6) 20 (5) 20 (5) 20 (5) • 20 (5) 20 (5). 93 F i g u r e 22. Ammonia i n w a t e r o f e x p e r i m e n t a l f i e l d e n c l o s u r e s . P l o t t e d d a t a a r e combined t o show e f f e c t o f a q u a t i c macrophytes and-or sediment i n changing w a t e r c h e m i s t r y . P L A N T S S E D I M E N T A A L G A E •A-B A L G A E | S E D T M c N T \ l A L G A E P L A N T S • A . D 94 95 Table XIV. Average production r a t e s of regenerated ammonia from major sources i n the enclosures. Source Average Production Rate mg/l/day Enclosure • B D-B A-C C-B A-D Algae 5 . 6 1 Macrophytes 0.30 0.55 Sediment 1 . 8 2 2 . 0 8 96 the r i c h and a c t i v e m i c r o b i a l community as s o c i a t e d w i t h s e d i -ment surfaces. S i m i l a r i l y , the sediment i n the enclosure c o n t a i n i n g rooted p l a n t s showed higher regeneration r a t e s than that i n the c y l i n d e r without p l a n t s . Again, e i t h e r more b a c t e r i a are a s s o c i a t e d w i t h a.plant-sediment i n t e r f a c e or the p l a n t roots are producing a more "pervious" sediment surface thereby enhancing ammonia le a c h i n g from the sediment. I n any case, the f a c t that the algae and sediment e n t i r e l y dominated the experimental system w i t h respect to ammonia regeneration i s not s u r p r i s i n g . That there are large accumulations of ammonia i n the deep l a y e r s of the t r o p h o l y t i c zone has been w e l l documented (Hutchinson 1 9 5 7 ) . As w e l l , the c l a s s i c works of Mortimer ( 1 9 4 1 - 4 2 ) and more recent i n v e s t i -gations by A u s t i n and Lee ( 1 9 7 3 ) a l l demonstrate t h a t ammonia i s f r e e l y l i b e r a t e d from the sediment p r i m a r i l y when the o x i d i z e d microzone on the sediment surface i s reduced. This being the case under anaerobic c o n d i t i o n s , would e x p l a i n the a c t i v e r o l e Of the sediment i n ammonia regeneration i n s i d e the experimental c y l i n d e r s of t h i s study. Furthermore, the c o n t r i b u t i o n of ammonia from algae i n the experimental system i s due mostly t o the lar g e n i t r o g e n and p r o t e i n content a s s o c i a t e d w i t h blue-green algae. In a study of the amino a c i d composition of freshwater 97 a l g a e , Boyd (1973) found the h i g h e s t p r o t e i n and n i t r o g e n v a l u e s i n Anabaena c i r c i n a l i s tea. 46% t o t a l p r o t e i n and ca. 9% N) . N i t r o g e n r e g e n e r a t i o n o f mixed and pure c u l t u r e s o f decomposing a l g a e s t u d i e d by Foree e t a l , (1970) was v e r y h i g h f o r pure c u l t u r e s o f Anabaena. From t h e r e s u l t s o f t h i s s t u d y and from e v i d e n c e e l s e -where, sediment and a l g a e ( e s p e c i a l l y b l u e - g r e e n s ) w i l l r e -ge n e r a t e p r o p o r t i o n a t e l y much g r e a t e r amounts o f ammonia t h a n w i l l r o o t e d a q u a t i c p l a n t s . T h i s i s p r o b a b l y p a r t i c u l a r l y t r u e o f many e u t r o p h i c s i t e s w h i c h are s i m i l a r t o the r e s e r v o i r s t u d i e d ; i n terms o f h a v i n g an abundance of a q u a t i c macrophytes, some l a r g e a l g a e blooms and p e r i o d i c a n a e r o b i c c o n d i t i o n s . 2.4.2 T o t a l K j e l d a h l and O r g a n i c N i t r o g e n TKN a t : t h e s t a r t o f the ex p e r i m e n t was h i g h (13.5 mg/1) m a i n l y due t o the l a r g e bloom o f Anabaena p r e s e n t i n the wat e r a t t h a t t i m e . F u r t h e r m o r e , almost a l l o f t h i s TKN was d i s s o l v e d and p a r t i c u l a t e o r g a n i c N because ammonia N (.069 mg/1) and NO^/NO^-N (.026 mg/1) were b o t h v e r y l o w i n c o n c e n t r a t i o n . There was an immediate d e c l i n e i n TKN i n each c o n t a i n e r o v e r the f i r s t 5 t o 10 days ( F i g u r e 23). O b s e r v a t i o n s a t the same time showed t h a t t h e a l g a e r a p i d l y d i e d d u r i n g t h i s p e r i o d e i t h e r f l o a t i n g t o t h e s u r f a c e o r s e t t l i n g t o t h e bottom o f 98 F i g u r e 23. T o t a l K j e l d a h l N i t r o g e n i n w a t e r o f e x p e r i m e n t a l f i e l d e n c l o s u r e s . P l o t t e d d a t a are combined t o show e f f e c t o f a q u a t i c macrophytes and-or sediment i n c h anging w a t e r c h e m i s t r y . P L A N T S S E D I M E N T A A L G A E B •A-A L G A E D 99 100 the e n c l o s u r e s . S i n c e t h e s e s u r f a c e scums o f f l o a t i n g dead a l g a e were c a r e f u l l y e x c l u d e d when wa t e r samples were t a k e n , the TKN v a l u e s o f the w a t e r r e f l e c t the absence of a l g a l c e l l s w h i c h were i n i t i a l l y abundant. Moreover, t h i s r a p i d drop i n TKN s u g g e s t e d t h a t t h e i n i t i a l t o t a l N o f the w a t e r c o n s i s t e d s u b s t a n t i a l l y o f p a r t i c u l a t e o r g a n i c N. A f t e r 10 t o 15 d a y s , TKN l e v e l s i n the c y l i n d e r s r e c o v e r e d and g r a d u a l l y i n c r e a s e d u n t i l t h ey l e v e l e d o f f i n 36 t o 50 days above and below i n i t i a l l e v e l s depending on the c y l i n d e r . The most o b v i o u s d i f f e r e n c e between the TKN r e s u l t s o f the c y l i n d e r s was i n : 1) the i n i t i a l d e c l i n e d u r i n g t h e f i r s t 10-15 days and 2) t h e subsequent r e c o v e r y , as e v i d e n t i n F i g u r e 23. TKN appeared t o d e c r e a s e much more i n t h o s e c y l i n d e r s c o n t a i n i n g p l a n t s (both w i t h and w i t h o u t sediment) t h a n i n c y l i n d e r s not c o n t a i n i n g p l a n t s . The a q u a t i c macrophytes may d i r e c t l y o r i n d i r e c t l y a c c o u n t f o r t h i s phenomenon. The v e r y l a r g e s u r f a c e a r e a p r o v i d e d by the p l a n t s f o r t h e growth of b a c t e r i a would u n d o u b t e d l y i n c r e a s e b a c t e r i a l uptake o f l a b i l e d i s s o l v e d N compounds as they were l i b e r a t e d by t h e decomposing Anabaena. A q u a t i c macrophytes can a l s o d i r e c t l y t a k e up d i s s o l v e d o r g a n i c N compounds ( A l l e n 1971) or d i s s o l v e d i n o r g a n i c N ( F i t z g e r a l d 1968, T o e t z 1973) i n the d ark. In t h i s way, the M y r i o p h y l l u m c o u l d have caused the sudden d e c l i n e o f TKN, 101 n o t i c e a b l e i n s i d e the enclosures immediately a f t e r the s t a r t of the experiment. The recovery of TKN evident a f t e r about 10 to 15 days (Figure 23) i s p r i m a r i l y due to the r a p i d , simultaneous i n -crease of ammonia i n each c y l i n d e r . This p o i n t i s more c l e a r l y i l l u s t r a t e d i f these data are p l o t t e d as t o t a l organic N, i . e . TKN minus ammonia (Figure 24) Now the data c l e a r l y show that organic N decreased r a p i d l y at f i r s t and more g r a d u a l l y a f t e r ca. 15 days (very t y p i c a l decay curves). In the c y l i n d e r s c o n t a i n i n g aquatic p l a n t s however, there was a s l i g h t recovery of organic N a f t e r about 15 days followed by a d e c l i n e which was much more gradual than that shown by the other two c y l i n d e r s (water and sediment o n l y ) . I t appears then t h a t the aquatic p l a n t s are regenerating some organic N as w e l l as ammonia. Although the sediment was found to c o n t r i b u t e s i g n i f i -cant amounts of ammonia, no organic N was c o n t r i b u t e d . A c t u a l l y , the l o s s of organic N was s l i g h t l y g r eater and more r a p i d i n those c y l i n d e r s exposed to sediment. The r i c h e r microfauna i n the sediment-water c y l i n d e r s would e x p l a i n the greater decomposition r a t e s of p a r t i c u l a t e organic N. (algae) i n the water. Moreover, some adsorption of organic N compound to the sediment surface could a l s o have been i n v o l v e d . The TKN r e s u l t s s u b s t a n t i a t e that by f a r the l a r g e s t p r o p o r t i o n of regenerated N appeared as ammonia. Some of 102 F i g u r e 24. T o t a l O r g a n i c N i t r o g e n i n w a t e r o f e x p e r i m e n t a l f i e l d e n c l o s u r e s . P l o t t e d d a t a a r e combined t o show e f f e c t o f a q u a t i c macrophytes and-or sediment i n c hanging w a t e r c h e m i s t r y . ALGAE ., PLANTS SEDIMENT A ALGAE B ALGAE S^5TMENTN - o ALGAE PLANTS C D 103 104 t h i s ammonia a l o n g w i t h o t h e r d i s s o l v e d o r g a n i c N compounds was t a k e n up by the a q u a t i c macrophytes i m m e d i a t e l y a f t e r t h e y were p l a c e d i n t o d a r k n e s s . F i n a l l y , s m a l l amounts o f o r g a n i c N were l i b e r a t e d by t h e p l a n t s as t h e y decomposed a f t e r about 15 days ( F i g u r e 2 4 ) . 2.5 Regenerated phosphorus 2.5.1 Orthophosphate A t t h e s t a r t o f the exp e r i m e n t o n l y about 2% o f the t o t a l P p o o l i n the water o f each c y l i n d e r was o r t h o p h o s p h a t e (OP). In each c y l i n d e r however, OP i n c r e a s e d r a p i d l y a f t e r 10 days r e a c h i n g a maximum a f t e r about 3 weeks i n the c y l i n d e r con-t a i n i n g p l a n t s r o o t e d i n sediment and a f t e r about 50 days i n the r e m a i n i n g c y l i n d e r s ( F i g u r e 25). A f t e r maximum c o n c e n t r a t i o n was r e a c h e d , a l l c y l i n d e r s showed a d e c l i n e i n OP f o r the remainder o f the ex p e r i m e n t . T h i s OP whi c h d i s a p p e a r e d from the w a t e r o f the c y l i n d e r a f t e r about 30 t o 50 days was l o s t e i t h e r by t r a n s f o r m a t i o n t o d i s -s o l v e d o r p a r t i c u l a t e o r g a n i c P o r by a d s o r p t i o n . S i n c e t o t a l P measurements a l s o showed a d e c l i n e s i m i l a r t o the OP ( F i g u r e 2 6 ) , t h e n o n l y the second e x p l a n a t i o n o f l o s s by ad-s o r p t i o n seems f e a s i b l e . M i n e r a l i z a t i o n r a t e s o f P t i e d up i n a l g a l t i s s u e were q u i t e s u b s t a n t i a l a f t e r about 15 days. The a l g a e r e g e n e r a t e d OP a t an average r a t e of 129.2 ^ g / l / d a y (Table XV), Orthophosphate i n w a t e r o f e x p e r i m e n t a l f i e l d e n c l o s u r e s . P l o t t e d d a t a a r e combined t o show e f f e c t o f a q u a t i c macrophytes and-or sediment c h a n g i n g w a t e r c h e m i s t r y . D 1 0 6 600-1 107 Table XV. Average production r a t e s of regenerated phosphate from major sources i n the enclosures. Source Average Production Rate Mg/l/day Enclosure B D-B A-C C-B A-D Algae 12 9.21 Macrophytes 143.74 156.09 Sediment 59.22 71.57 108 The a q u a t i c p l a n t s r e g e n e r a t e d OP a t an average r a t e o f 143.7 and 156.0 ju.g/1/day. As w i t h N, the r e g e n e r a t i o n o f p l a n t P was g r e a t e r where the p l a n t s were r o o t e d i n the s e d i -ment w h i c h u n d o u b t e d l y c o n t r i b u t e d a r i c h p o p u l a t i o n o f decomposer m i c r o o r g a n i s m s . OP l e a c h e d out o f the sediment a t an average r a t e o f 59.2 and 71.5 / j g / l / d a y . A g a i n the l i b e r a t i o n o f P from the sediment was s i m i l a r t o N i n t h a t the sediment w i t h r o o t e d a q u a t i c p l a n t s r e g e n e r a t e d more OP t h a n t h e sediment w i t h o u t p l a n t s . R e g e n e r a t i o n o f OP from the sediment was enhanced by the r a p i d d e c l i n e i n D.O. t o l e v e l s below 1 ppm. The works o f M o r t i m e r (1941 and 1942) Stumm and L e c k i e (1970) and o t h e r s t u d i e s d e a l i n g w i t h t h e c h e m i c a l exchanges between sediment and w a t e r have a l l shown t h a t under a n a e r o b i c c o n d i t i o n s , sediments m o b i l i z e and t r a n s f e r i n t o the w a t e r , phosphate, p r e v i o u s l y h e l d i n complex form. The m i n e r a l c y c l e s o f aluminum and e s p e c i a l l y i r o n a re i n t i m a t e l y i n v o l v e d i n t h e a d s o r p t i o n and r e l e a s e o f P from t h e sediment s i n c e h y d r o x i d e s and o x i d e s of b o t h o f t h e s e elements s t r o n g l y a dsorb P (Kramer e t a l . 1972). The pH o f t h e w a t e r a l s o seems t o i n f l u e n c e the r e l e a s e o f P from the sediment s u r f a c e . MacPherson (1958) demonstrated t h a t pH changes below, but e s p e c i a l l y above 5.5 t o 6.5 /caused i n c r e a s e s i n the r e l e a s e o f P from t h e sediment. The pH l e v e l s were h i g h b e f o r e and a f t e r about 50 days o f t h e e x p e r i m e n t ; d u r i n g the e x t e n s i v e a n a e r o b i c p e r i o d o f the 109 e x p e r i m e n t pH l e v e l s averaged around 6.5. The somewhat p e r p l e x i n g problem o f the d e c l i n e o f OP i n the w a t e r o f the c y l i n d e r a f t e r about 50 days was p r e v i o u s l y r e p o r t e d t o be due t o a l o s s by a d s o r p t i o n . I n l i g h t o f the above d i s c u s s i o n on t h e r o l e o f the sediment, a l o s s o f P from the w a t e r t o the sediment might have o c c u r r e d i f the s l i g h t i n c r e a s e i n D.O. e v i d e n t a f t e r 50 days (Table XI) was s u f f i c i e n t t o a l l o w f o r the p r e c i p i t a t i o n and s e t t l i n g o f p h o s p h a t e - m i n e r a l complexes. However, the a l u m i n i u m s u r f a c e o f the c y l i n d e r s c o u l d a l s o have p r o v i d e d a s i t e f o r P s o r p t i o n . S i n c e aluminium o x i d e s adsorb P (Kramer e t a l . 1972), the s u r f a c e a r e a i n s i d e each c y l i n d e r c o u l d have been r e s p o n s i b l e f o r t h e removal o f P w h i c h would have m a n i f e s t e d i t s e l f e s p e c i a l l y toward the end o f the e x p e r i m e n t , where r e g e n e r a t i o n r a t e s o f p l a n t and a l g a e P d e c l i n e d . A q u a t i c macrophytes c o n t r i b u t e d most s i g n i f i c a n t l y t o the r e g e n e r a t i o n o f P i n the e x p e r i m e n t a l e n c l o s u r e s . P l a n t s had a much more i m p o r t a n t r o l e i n the r e g e n e r a t i o n o f P t h a n i n the r e g e n e r a t i o n o f N. More P was r e l e a s e d by the macrophytes p r o p o r t i o n a l t o o r i g i n a l l e v e l s p r e s e n t i n the w a t e r t h a n was N. The r e s u l t o f t h i s was r e f l e c t e d by the N:P r a t i o i n the w a t e r w h i c h d e c l i n e d from an i n i t i a l 25:1 t o a f i n a l maximum of 17:1. 110 2.5,2 T o t a l and o r g a n i c phosphorus S i m i l a r t o the i n i t i a l TKN v a l u e s measured i n t h e r e -s e r v o i r w a t e r , i n i t i a l t o t a l phosphorus (TP) v a l u e s were h i g h ( 5 4 9 ^ g / 1 ) due t o the Anabaena bloom p r e s e n t i n the w a t e r . Almost a l l o f t h i s P (9 8%) was d i s s o l v e d and m a i n l y p a r t i c u l a t e o r g a n i c P. The sudden drop i n TP a f t e r about 5 t o 10 days f o l l o w s the same p a t t e r n t h a t was apparent i n the TKN r e s u l t s . That i s , the abundant a l g a e c e l l s w h i c h accounted f o r most o f the i n i t i a l TP i n the w a t e r , d i s a p p e a r e d r a p i d l y a f t e r the e x p e r i m e n t was s t a r t e d . Moreover, as i n the TKN r e s u l t s , somewhat more t o t a l P was removed from the w a t e r i n c y l i n d e r s c o n t a i n i n g a q u a t i c p l a n t s than from the o t h e r two e n c l o s u r e s . A g a i n , t h e uptake of d i s s o l v e d P compounds by the macrophytes and a s s o c i a t e d e p i p h y t e s might have ac c o u n t e d f o r t h i s d i f f e r e n c e . However, a f t e r t h e i n i t i a l d e c l i n e i n TP, r e s u l t s o f TKN and TP are somewhat d i s s i m i l a r . TP showed a r a p i d r e c o v e r y f a r e x c e e d i n g i n i t i a l l e v e l s i n the c y l i n d e r s c o n t a i n i n g p l a n t s , f o l l o w e d by a s u b s t a n t i a l d e c r e a s e between the time maximum l e v e l s were r e a c h e d (ca. 36 days) and t h e end o f the e x p e r i m e n t ( F i g u r e 26). I n the o t h e r two c y l i n d e r s , w i t h o u t p l a n t s , r e c o v e r y o f TP was much l e s s pronounced and somewhat more v a r i a b l e t h r o u g h t o t h e end o f the e x p e r i m e n t ( F i g u r e 26). I n s p i t e o f f l u c -t u a t i o n s and i r r e g u l a r i t i e s o f t h e p l o t t e d TP d a t a , t h e r i s e <. i n TP a f t e r about 10 days, n o t i c e a b l e T o t a l Phosphorus i n w a t e r o f e x p e r i m e n t a l f i e l d e n c l o s u r e s . P l o t t e d d a t a a r e combined t o show e f f e c t o f a q u a t i c macrophytes and-or sediment i n ch a n g i n g water c h e m i s t r y . D 112 113 F i g u r e 27. T o t a l O r g a n i c Phosphorus i n w a t e r o f e x p e r i -m e n t a l f i e l d e n c l o s u r e s . P l o t t e d d a t a a r e combined t o show e f f e c t o f a q u a t i c macrophytes and-or sediment i n changing w a t e r c h e m i s t r y . 114 115 e s p e c i a l l y i n t h o s e c y l i n d e r s w i t h p l a n t s , was a c c o u n t e d f o r m a i n l y by the c o n c o m i t a n t i n c r e a s e i n OP. Thus, when OP i s s u b t r a c t e d from TP, t h e r e s u l t i n g c u r v e s ( F i g u r e 27) show i n s p i t e o f some f l u c t u a t i o n s , a g e n e r a l l y c o n s t a n t l e v e l of t o t a l i n o r g a n i c P. I n o t h e r words, a f t e r an i n i t i a l d e c l i n e o f m a i n l y p a r t i c u l a t e o r g a n i c P, f o l l o w e d by a s m a l l , b r i e f p u l s e o f i n c r e a s e , l e v e l s e i t h e r remained s t a b l e o r f l u c t u a t e d up and down f o r the r emainder of t h e e x p e r i m e n t . Due t o t h e l a r g e v a r i a b i l i t y i n t h e t o t a l o r g a n i c P r e s u l t s o v e r t i m e , no m e a n i n g f u l comparisons can be made b e t -ween t h e v a r i o u s e x p e r i m e n t a l c y l i n d e r s . I n g e n e r a l t h e n , t h e major t r e n d i n t h e TP r e s u l t s i s m a i n l y due t o t h e appearance of OP i n the e x p e r i m e n t a l c y l i n d e r s . Other t h a n f o r t h e major d e c l i n e i n t o t a l o r g a n i c P, common w i t h i n each c y l i n d e r , t h e r e s u l t s show a l a r g e v a r i a b i l i t y around a c o n s t a n t and perhaps d e c r e a s i n g t o t a l o r g a n i c P l e v e l . 2.6 B a c t e r i a 2.6.1 G e n e r a l c h a r a c t e r i s t i c s B a c t e r i a showed up d i s t i n c t l y i n a l l samples as g r een f l u o r e s c i n g o b j e c t s . Most b a c t e r i a c o n s i s t e d o f l a r g e r o d -shaped c e l l s , and l e s s t h a n h a l f o f t h e r e s t were s m a l l c o c c o i d forms, some o f w h i c h showed a r e d f l u o r e s c e n c e . D e t r i t a l p a r t i c l e s f l u o r e s c e d as b r i g h t y e l l o w or r e d 116 o b j e c t s and any a t t a c h e d b a c t e r i a were i n c l u d e d i n the count. The o n l y o t h e r o b j e c t s w h i c h appeared f r e q u e n t l y were v e r y l o n g , t h i n , s t r a i g h t , f i l a m e n t s y h i c h showed a g r e e n f l u o r e s -cence. These o b j e c t s were n o t counted as i t was s u s p e c t e d t h a t t hey were a type o f a q u a t i c Hyphomycete ( a q u a t i c f u n g i ) , r a t h e r t h a n b a c t e r i a . Mean t o t a l c o u n t s o f b a c t e r i a ranged from 1.85 X 10 t o 2.48 X 10^ c e l l s / m l ±10% o f t h e mean. To g a i n a g r e a t e r a p p r e c i a t i o n o f the r e l a t i v e magnitude o f the b a c t e r i a counts i n t h i s s t u d y , t h e range o f v a l u e s a re compared t o r e s u l t s o b t a i n e d e l s e w h e r e i n the l i t e r a t u r e where d i r e c t counts u s i n g e p i f l u o r e s c e n c e had been employed on samples from n a t u r a l a q u a t i c ecosystems (Table X V I ) . I n t h e l i t e r a t u r e t h e t o t a l b a c t e r i a counts range from 2 X 1 0 2 t o 8 X 10^ c e l l s / m l i n a v a r i e t y o f a q u a t i c h a b i t a t s . As would be': e x p e c t e d , the range o f v a l u e s found i n t h i s s t u d y exceed most r e s u l t s found i n t h e l i t e r a t u r e , s i n c e s h o r t l y a f t e r t h e d e a t h o f a q u a t i c p l a n t s and a l g a e , c o n d i t i o n s i n the r e -s e r v o i r became v e r y c o n d u c i v e f o r t h e growth o f b a c t e r i a . S i n c e t e m p o r a l v a r i a t i o n s o f b a c t e r i a l p o p u l a t i o n dynamics are e x t r e m e l y r a p i d , the measurements o f t o t a l c e l l c o u n t s from t h i s s t u d y m e r e l y r e p r e s e n t a summation o f a l a r g e number o f e v e n t s o c c u r r i n g i n a mixed n a t u r a l p o p u l a t i o n o f suspended b a c t e r i a . T h e r e f o r e , the c u r v e s and r e s u l t i n g s l o p e s o f the p l o t t e d d a t a ( F i g u r e 28) by no means r e p r e s e n t any r e a l 117 Table XVI. Range o f r e s u l t s o f t o t a l b a c t e r i a c o u n t s i n t h i s s t u d y compared t o r e s u l t s found i n the l i t e r a t u r e where f l u o r e s c e n t , d i r e c t c o u n t i n g t e c h n i q u e s were used. Range of R e s u l t s Sample Type No. of c e l l s / m l Reference © Sea water 2 X 10 2 - 6 X 10 6 Zimmermann (1974) © Sea water 4 X 10 4 - 2 X 10 5 Robbie e t a l . (1972) © F r e s h water 9 X 10 5 - 1 X 10 6 Daley (197 5) 0 R e s e r v o i r water 2 X 10 6 - 3 X 10 7 THIS STUDY (1974/75) © Lake water 3 X 10 4 - 8 X 10 6 Jones (1974) 2 3 1 0 I O 4 I O 5 1 0 6 I O 7 8 1 0 I O 1 I—— —© 1 h - d > H I —<D- 1 Range of r e s u l t s shown s c h e m a t i c a l l y ; (no. c e l l s per ml) 118 p o p u l a t i o n parameter such as s t a t i o n a r y phases, i n c r e a s i n g r a t e s o f m u l t i p i c a t i o n , o r l a g phases, e t c . , o f the b a c t e r i a l p o p u l a t i o n s . R e s u l t i n g d a t a m e r e l y e x p r e s s the t o t a l s t o c k . of b a c t e r i a a c c o u n t a b l e w i t h the t e c h n i q u e employed. No f u r t h e r assumptions were made about the . a c t i v i t y o r v i a b i l i t y o f the measured b a c t e r i a l c e l l s o t h e r t h a n t o assume t h a t t h e b a c t e r i a had N and P c o n t e n t s r e p r e s e n t a t i v e o f the "average" v a l u e s s u g g e s t e d i n the l i t e r a t u r e . Under normal c u l t u r e c o n d i t i o n s , b a c t e r i a l p o p u l a t i o n s e x h i b i t an i n i t i a l l o g phase o f r a p i d growth f o l l o w e d by a r e l a t i v e l y s t a b l e p o p u l a t i o n s i z e . S i n c e t h e measurements of t o t a l b a c t e r i a numbers i n t h i s s t u d y c o v e r e d a time span o f 70 days, no m e a n i n g f u l c o n c l u s i o n s about t h e b a c t e r i a l popu-l a t i o n dynamics can be made. However, the c u r v e s o f the p l o t t e d r e s u l t s ( F i g u r e 28) do demonstrate t h a t b a c t e r i a l biomass i n c r e a s e d r a p i d l y by an o r d e r o f magnitude, p r o b a b l y i n much l e s s t h a n 5 days from the b e g i n n i n g o f the e x p e r i m e n t . T o t a l numbers o f b a c t e r i a t h e n f l u c t u a t e d between ca. 6 7 7 X 10° and 2 X 10 c e l l s / m l f o r the remainder o f the e x p e r i -ment, i n the e n c l o s u r e s exposed t o the sediment. I n the en-c l o s u r e s n o t exposed t o the sediment, b a c t e r i a l numbers ranged between 2 X 1 0 6 and 2 X 1 0 7 c e l l s / m l . I t i s i n t e r e s t i n g t h a t the major d e c l i n e s i n t o t a l b a c t e r i a l numbers o c c u r r e d between 5 and 15 days and a g a i n a f t e r 36 days from t h e s t a r t o f the e x p e r i m e n t - ( F i g u r e 28). I t i s a t 5 t o 15 days t h a t DO l e v e l s w i t h i n each c y l i n d e r dropped below 119 6^3 -T- r — i i 1 i : : 1 5 10 15 22 36 50 70 T I M E I N D A Y S F i g u r e 28. T o t a l c o u n t s o f suspended b a c t e r i a " i n e n c l o s u r e A ( • ) , B ( A )', C ( o ) and D ( A ) . 120 1 ppm and a f t e r 36 days i n c r e a s e d above 1 ppm a g a i n . These major s h i f t s i n t o t a l b a c t e r i a l numbers were co-i n c i d e n t a l w i t h changes t o and from a n a e r o b i c c o n d i t i o n s w i t h i n the e x p e r i m e n t a l e n c l o s u r e s . Thus, i t appears t h a t t h e s e major s h i f t s i n b a c t e r i a l numbers r e f l e c t e d changes o f b a c t e r i a s p e c i e s c o m p o s i t i o n . In the r e s e r v o i r w a t e r i t s e l f (Table X V I I ) . t h e number of b a c t e r i a s t a r t e d t o i n c r e a s e more r a p i d l y s h o r t l y a f t e r maximum d i e - o f f o f t h e a q u a t i c p l a n t s growing i n the r e -s e r v o i r was n o t i c e d ('ca. 50 days a f t e r s t a r t o f e x p e r i m e n t ) . 2.6.2 N and P removed by suspended b a c t e r i a S i n c e t o t a l c o u n t s o f b a c t e r i a are s u f f i c i e n t t o show t o t a l s t a n d i n g s t o c k o r biomass o f c e l l s ' suspended i n t h e w a t e r o f t h e e x p e r i m e n t a l e n c l o s u r e s , a rough e s t i m a t e can be d e r i v e d t o i l l u s t r a t e the amount o f N and P t h a t was removed from t h e w a t e r by t h e b a c t e r i a . D oetsch and Cook (1973) p r o v i d e e s t i m a t e s o f biomass and N and P c o n t e n t s o f the "average" b a c t e r i a l c e l l w h i c h are as f o l l o w s : I f t h e s p e c i f i c g r a v i t y o f common b a c t e r i a l forms i s around 1.07, and t h e i r average volume i s 1 /jm , t h e n the "wet w e i g h t " o f a s i n g l e o r g a n i s m would be about IO--*-2 g. F u r t h e r m o r e , b a c t e r i a l c e l l s are about 70 t o 90% w a t e r and t h e r e f o r e t h e d r y w e i g h t i s 10 t o 30% o f the "wet w e i g h t " (20% was used i n t h e c a l c u l a t i o n s o f t h i s s t u d y ) . T a b l e X V I I . Average t o t a l suspended b a c t e r i a counts i n number of c e l l s / m l X 1 0 7 ±10 p e r c e n t , i n s i d e and o u t s i d e o f e n c l o s u r e s d u r i n g c o u r s e o f experiment. Time i n days a f t e r b e g i n n i n g o f experiment S i t e 0 5 10 15 22 36 50 70 O u t s i d e . 185 . 27 .240 . 190 .20 .216 . 292 1. 02 A . 185 1.99 1.68 1. 33 1.5 2. 17 .718 .693 B . 185 2.02 . 939 1.73 1. 7 1. 82 . 372 .966 D . 185 1.74 1.11 1.13 1. 3 1. 84 . 217 . 623 C . 185 1. 6 2 1.12 . 606 .72 1. 12 2.48 .7 07 122 The dry weight of b a c t e r i a has an approximate ni t r o g e n and phosphorus content of 1 5 and 1% r e s p e c t i v e l y . The estimate of average dry weight of b a c t e r i a l c e l l s used i n t h i s study a l s o corresponds c l o s e l y to that used by Daley (personal communication) who uses an estimate of 3.7 X 10 jaq f o r the average dry wt of a b a c t e r i a l c e l l . To c a l c u l a t e N and P (mg/1) represented by t o t a l suspended b a c t e r i a i n each c y l i n d e r , t o t a l c e l l counts ( c e l l s / m l ) were m u l t i p l i e d by the average dry weight of a b a c t e r i a l c e l l — ] 3 (2.0 X 10 g) which was m u l t i p l i e d by average b a c t e r i a l N (15%) and P (1%) content which was m u l t i p l i e d by 1 X 10 3 ml to produce a f i n a l estimate i n ,ug/l of b a c t e r i a l P and mg/1 of b a c t e r i a l N. Results of these c a l c u l a t i o n s (Table XVIir) o f f e r a rough estimate of the amount of n u t r i e n t t h a t was t i e d up i n b a c t e r i -a l biomass at given time i n t e r v a l s during the experiment. The amount of N and P represented by the standing stock of suspended b a c t e r i a i s a l s o expressed as a precentage of the t o -t a l organic n u t r i e n t pool i n the water of each enclosure at given times of measurement. In t h i s r e s p e c t , a maximum amount of 31%, wi t h an average value of 9% of the t o t a l organic P pool was accounted f o r by suspended b a c t e r i a . The balance of the t o t a l organic P pool probably c o n s i s t e d of d i s s o l v e d organic P, p a r t i c u l a t e organic P (as t r i p t o n ) and h e t e r o t r o p h i c microorganisms other than 123 Table XVIII. T o t a l amount of N and P t i e d up i n suspended b a c t e r i a ; a l s o expressed as a percentage r e l a t i v e to t o t a l organic N and P i n water of enclosures. tr> io a a W EH u 3 i!) O rH O c w T o t a l Amountl yg/1 N Percent W >i <U rfl iH C Q P •rH •—• w H 0 O. e cl •rH c EH w T o t a l Amount ug/1 • N. Percent A .3 . 7 5 0 . 4 0 . 6 'l A 30 . 0 ' 450 7 . 8 12 . 7 0 B 3 7 , 5 0 . 4 . 0 . 6 1 B 34 . 0 510. 10 8 21 . 2 22 C 3 7 5 0 4 0 6 C 26 . 0 • 390 7 2 13 . 4 D 3 7 5 0 4 0 6 D 34 . 0 510 10 8 12 . 9 A 32 4 486 9 5 A 43 4 651 13 5 15 7 B 39 8 597 16 8 B 36 4 546 12 6 17 3 5 36 C 40 4 606 14 0 C 36 8 5.52 9 2 9 1 D 34 8 522 13 4 D . 22 4 336 10 1 8 2 A 33. 6 504 10. 7 15. 4 • A 14. 3 . 215 5. 5 . 4. 2 10 B 18. 7 281 2. 9 4. 8 B . 7. 4 111 3. 8 5. 5 50 C 22. 2 333 5. 2 9. 4 C 4. 3 - 3. 3 D 22. 4 336 4. 6 6. 9 D 49. 6 744 31. 0 19. 4 A 26. 6 399 8. 6 7. 8 A 13. 8 207 4 . 7 ' 8. 6 15 B 34. 6 519 9. 6 11. 1 B 19. 3 289 6. 0 8. 0 70 C 22. 6 339 6. 1 7. 1 C 12. 4 . 186 12. 4 5. 0 D 12. 1 181 3. 1 3. 0 D 14. 1 212 7. 2 9. 2 Average .26. 3 . 405 8. 8 10. 4 Maximum 49. 6 . 744 31. 0 21. 2 124 b a c t e r i a such as p r o t o z o a n s and a q u a t i c f u n g i . ' S i m i l a r i t y , a maximum of 21% and an average o f 10% o f the t o t a l o r g a n i c N p o o l can be a c c o u n t e d f o r by the suspended b a c t e r i a . The above v a l u e s do not i n c l u d e the r e s u l t s o b t a i n e d a t t h e b e g i n n i n g o f the e x p e r i m e n t s i n c e t h e s e v a l u e s changed v e r y q u i c k l y and t h e r e f o r e are n o t r e p r e s e n t a t i v e o f the b u l k o f t h e d a t a . Thus, i t i s a p p a r e n t from r e s u l t s o f measurements o f suspended b a c t e r i a t h a t s i g n i f i c a n t amounts o f r e g e n e r a t e d N and P were removed from t h e w a t e r by suspended b a c t e r i a . A t the same time however, i t i s r e a l i z e d t h a t the s t a n d -i n g s t o c k o f n u t r i e n t s measured i n t h e form o f b a c t e r i a l biomass m e r e l y shows an i n s t a n t a n e o u s and s t a t i c r e p r e s e n t a t -i o n o f a v e r y complex and dynamic p r o c e s s . The e x t r e m e l y r a p i d t u r n o v e r o f P, and the complex i n t e r a c t i o n s between b a c t e r i a and p r o t o z o a (Bardate and P r e n t k i 1974) a r e some examples d e m o n s t r a t i n g the c o m p l e x i t y o f the m i n e r a l c y c l e s o f s e d i m e n t - d e t r i t u s - m a c r o p h y t e systems. N o n e t h e l e s s , r e s u l t s o f t h i s s t u d y have demonstrated t h e i m p o r t a n t r o l e o f suspended b a c t e r i a l p o p u l a t i o n s i n r e -moving s u b s t a n t i a l amounts of m o b i l e r e g e n e r a t e d n u t r i e n t s r e l e a s e d by the decomposing l i t t o r a l f l o r a . I n t h i s r e s p e c t , more d e t a i l e d s t u d y o f the suspended b a c t e r i a i n l i t t o r a l w a t e r s would prove t o be most r e w a r d i n g . 125 SU^LMARY AND CONCLUSION D u r i n g t h e f o l l o w i n g d i s c u s s i o n o f and comparison b e t -ween the l a b o r a t o r y and f i e l d e x p e r i m e n t o f t h i s s t u d y , i t i s r e a l i z e d t h a t the f o r m e r e x p e r i m e n t was conducted under a e r o b i c c o n d i t i o n s and t h e l a t t e r under e s s e n t i a l l y a n a e r o b i c c o n d i t i o n s . Thus, f o r example, t h e a n a e r o b i o s i s o f the s e d i m e n t - d e t r i t u s - p l a n t s ystem c a r r i e s a c h a i n o f p a r a l l e l c h e m i c a l consequences, a l l o f w h i c h p r o b a b l y e f f e c t the p a t t e r n o f m i c r o b i a l d e g r a d a t i o n . However, t h i s s h o u l d n o t d e t r a c t from t h e v a l u e o f the o v e r a l l s t u d y w i t h r e s p e c t t o g a i n i n g some i n s i g h t i n t o the f a t e o f macrophyte p r o d u c t i o n and t h e g e n e r a l p r o c e s s e s o f p l a n t d e c o m p o s i t i o n and n u t r i e n t r e g e n e r a t i o n . S e v e r a l c o n c l u s i o n s and g e n e r a l i z a t i o n s a re e v i d e n t i n the o v e r a l l r e s u l t s o f t h i s s t u d y . From r e s u l t s o f the l a b o r a t o r y s t u d y , we can c o n c l u d e t h a t the o v e r a l l decomposit-i o n o f a q u a t i c - m i l f o i l i s q u i t e r a p i d and a l a r g e p r o p o r t i o n o f the t o t a l o r g a n i c p l a n t m a t t e r i s i m m e d i a t e l y t r a n s f o r m e d t o DOM. A l t h o u g h t h e b u l k o f the p l a n t m a t e r i a l d i s a p p e a r s w i t h -i n weeks, a s m a l l p r o p o r t i o n o f f i n e r e f r a c t o r y d e t r i t i c m a t t e r remains f o r a much l o n g e r p e r i o d o f t i m e . Soon a f t e r d e a t h o c c u r s , p l a n t m a t e r i a l i s q u i c k l y c o l o n i z e d by m i c r o b e s w h i c h i s e v i d e n t by a n u t r i e n t e n r i c h -ment o f t h e p l a n t d e t r i t u s e s p e c i a l l y w i t h r e s p e c t t o i t s 126 crude p r o t e i n c o n t e n t . I t i s t h e r e f o r e n o t u n r e a s o n a b l e t o suppose t h a t numerous a q u a t i c comsumers c o u l d u t i l i z e t h i s macrophyte d e t r i t u s as a f o o d s o u r c e . R e s u l t s of. t h i s study a l s o c l e a r l y demonstrate t h a t b o t h under a e r o b i c ( l a b o r a t o r y e x p e r i m e n t ) and a n a e r o b i c ( f i e l d e x p e r i m e n t ) c o n d i t i o n s , t h e r e i s a v e r y r a p i d r e g e n e r a t i o n o f d i s s o l v e d N and P compounds from the decomposing a q u a t i c p l a n t m a t e r i a l . However, s i n c e the n i t r o g e n c o n t e n t o f p h y t o p l a n k t o n , e s p e c i a l l y b l u e - g r e e n a l g a e , i s g e n e r a l l y much h i g h e r t h a n t h a t o f macrophytes (Boyd 1973), a l u x u r i -ant g r o w t h o f p h y t o p l a n k t o n w i l l r e l e a s e , p e r u n i t w e i g h t , much more d i s s o l v e d N compounds t h a n th e l i t t o r a l f l o r a . T h i s p o i n t was s u b s t a n t i a t e d by the " i n s i t u " e x p e r i m e n t conducted i n the f i e l d s i n c e a bloom o f Anabaena e x i s t e d a t the s t a r t o f t h e e x p e r i m e n t . Sediment a l s o r e l e a s e s s i g n i f i c a n t amounts o f d i s s o l v e d N (mostly ammonia), a l t h o u g h t h i s was m a i n l y due t o the l o w e r e d DO l e v e l s on the sediment s u r f a c e w i t h i n the ex-p e r i m e n t a l e n c l o s u r e s . Under a e r o b i c c o n d i t i o n s , s t u d i e s have shown t h a t t h e r e l e a s e o f d i s s o l v e d N compounds from the sediment i s n e g l i g i b l e (Mortimer 19 41,1942, and A u s t i n and Lee 1973). R e s u l t s from t h e l a b o r a t o r y e x p e r i m e n t show q u i t e c l e a r l y t h a t p l a n t P i s m o b i l i z e d much more r a p i d l y as s o l u b l e i n o r g a n i c - P (P0 4~P) , t h a n i s p l a n t ^ N (as NO-,-N) . 127 Maximum l e v e l s o f r e g e n e r a t e d P were much g r e a t e r r e l a t i v e t o i n i t i a l l e v e l s p r e s e n t i n the w a t e r t h a n t h o s e of r e -g e n e r a t e d N. T h i s phenomenon i s l a r g e l y e x p l a i n e d by t h e f a c t t h a t p l a n t P i s found i n compounds and groups of s u b s t a n c e s such as n u c l e i c a c i d s , n u c l e o p r o t e i n s , p h o s p h o r y l a t e d s u g a r s , p h o s p h o l i p i d s , coenzymes and ATP a l l o f w h i c h are v e r y r a p i d l y b r o k e n down by m i c r o o r g a n i s m s . Moreover, th e P i n t h e s e compounds e x i s t s as phosphate w h i c h a c c o u n t s f o r t h e immediate m o b i l i z a t i o n o f the p l a n t P compounds e v i d e n t i n t h e l a b o r a t o r y e x p e r i m e n t a l r e s u l t s . Thus, because o f the reduced n a t u r e of p l a n t N com-, pounds, and s i n c e the b u l k o f N i s found i n p l a n t p r o t e i n , N i s m o b i l i z e d much more s l o w l y than p l a n t P. T h e r e f o r e , w i t h t h e d e c o m p o s i t i o n of a q u a t i c p l a n t m a t e r i a l , s o l u b l e P becomes a v a i l a b l e sooner and more a b u n d a n t l y t h a n does s o l u b l e N. R e s u l t s o f the " i n s i t u " , f i e l d e x p e r i m e n t a l s o show t h a t as macrophytes decompose, more P i s r e l e a s e d p r o p o r t i o n a l t o o r i g i n a l l e v e l s p r e s e n t i n the w ater than N. T h i s r e s u l t e d i n a s i g n i f i c a n t change i n t h e N:P r a t i o o f t h e w ater from i n i t i a l maximum l e v e l s . I n any c a s e , th e o v e r a l l dynamic p r o c e s s o f m i n e r a l i z a t i o n and r e g e n e r a t i o n o f N and P compounds i s s i g n i f i c a n t l y a c c e l e r a t e d by a g r e a t e r n u t r i e n t c o n t e n t i n the w a t e r , e s p e c i a l l y w i t h r e s p e c t t o N. T h i s was v e r i f i e d by the l a b o r a t o r y e x p e r i m e n t o f t h i s 128 s t u d y . Moreover, t h i s i s a l s o c o n f i r m e d by i n f o r m a t i o n a v a i l a b l e i n t h e l i t e r a t u r e w h i c h shows t h a t i n many i n -s t a n c e s , the d e c o m p o s i t i o n p r o c e s s i s enhanced by g r e a t e r N l e v e l s i n the water (Kaushik and Hynes 1968,1971, N i c h o l s and Keeney 197 3 ) , F i n a l l y , r e s u l t s o f the f i e l d s t u d y demonstrate t h a t t h e d r a m a t i c i n c r e a s e o f suspended b a c t e r i a c o n c o m i t a n t w i t h t h e d e c o m p o s i t i o n o f a q u a t i c p l a n t m a t t e r can remove sub-s t a n i a l amounts o f N and P from the w a t e r . The o v e r a l l i m p l i c a t i o n s o f t h i s s t u d y are a p t l y summarized by Boyd (1974) who w r o t e , " s i n c e the a v a i l a b i l i t y o f i n o r g a n i c n i t r o g e n (and c e r t a i n l y a l s o P) i s an i m p o r t a n t f a c t o r r e g u l a t i n g a q u a t i c p r o d u c t i v i t y and N (and. p) i s o f t e n a s s o c i a t e d w i t h e u t r o p h i c a t i o n , i n f o r m a t i o n on t h e r e g e n e r a t i o n o f i n o r g a n i c N (a'nd p) from -decaying o r g a n i c m a t t e r i s v a l u a b l e i n b o t h t h e o r e t i c a l and p r a c t i c a l c o n s i d e r a t i o n s o f a q u a t i c r e s o u r c e s . " Comments added i n p a r e n t h e s e s are my own. The f i n d i n g s o f t h i s s t u d y a l s o s u p p o r t th e c o n c l u s i o n t h a t much o f t h e l a b i l e o r g a n i c N and P o f a q u a t i c p l a n t s i s m i n e r a l i z e d o r r e l e a s e d i n t o t h e w a t e r as s o l u b l e o r g a n i c and i n o r g a n i c compounds b e f o r e the d e t r i t a l r e s i d u e s , w h i c h a r e m a i n l y o f a r e f r a c t o r y n a t u r e , a r e i n c o r p o r a t e d i n t o the sediment. A q u a t i c macrophytes are a v e r y i m p o r t a n t component i n t h e l i t t o r a l r e c y c l i n g o f N and P, as t h i s s t u d y has shown 129 and t h u s deserve much more a t t e n t i o n i n f u t u r e a q u a t i c r e s e a r c h . 130 •LITERATURE CITED Adams, F. 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Lakes Res. S t a k e , E. 1967. H i g h e r v e g e t a t i o n and n i t r o g e n i n a r i v u l e t i n c e n t r a l Sweden. Schweiz. Z e i t . Hydro. 29: 107-124. . 1968. H i g h e r v e g e t a t i o n and phosphorus i n a s m a l l s t r e a m i n c e n t r a l Sweden. Schweiz. Z e i t . Hydro. 30: 353-373. S t a n d a r d Methods f o r t h e E x a m i n a t i o n o f Water and Wastewater. 1971. Am. P u b l . H e a l t h A s s o c . S t r i c k l a n d , J . D. H., and T. R. P a r s o n s . 1968. A p r a c t i c a l handbook f o r seawater a n a l y s i s . F i s h e r i e s R e s e a r c h Board Canada. B u l l . 167, 136 Stumm, W. , and J . 0. L e c k i e . 1 9 7 0 . Phosphate exchange w i t h s e d i m e n t s ; i t s r o l e i n the p r o d u c t i v i t y o f s u r f a c e w a t e r s . Adv. Wat. P o l l . Res. 3: 26/1-26/16. T o e t z , D. W. 1973. The k i n e t i c s o f NH, uptake by C e r a t o -p h y l l u m , H y d r o b i o l o g i a 41: 275-290. W e s t l a k e , D. F, 1963. Comparisons o f p l a n t p r o d u c t i v i t y . B i o l . Rev. 38: 385-425. W e t z e l , R. G. 1964. A c o m p a r a t i v e s t u d y o f the p r i m a r y p r o d u c t i v i t y o f h i g h e r a q u a t i c p l a n t s , p e r i p h y t o n and p h y t o p l a n k t o n i n a l a r g e , s h a l l o w l a k e . I n t . Revue ges. H y d r o b i o l . 49: 1-61. . 1969. F a c t o r s i n f l u e n c i n g p h o t o s y n t h e s i s and e x c r e t i o n o f d i s s o l v e d o r g a n i c m a t t e r by a q u a t i c macro-p h y t e s i n h a r d - w a t e r l a k e s . V e r h . I n t e r n a t . V e r e i n . L i m n o l . 17: 72-85. - . t a n d B. U l e h l o v a . 1971. D e c o m p o s i t i o n and m i n e r a l c y c l i n g . H i d r o b i o l o g i a 12: 391-392. . , and B. A. Manny. 1972. S e c r e t i o n o f d i s s o l v e d o r g a n i c carbon and n i t r i g e n by a q u a t i c macrophytes. V e r h . I n t e r n a t . V e r e i n . L i m n o l . 18: 162-170. ., and B. A. Manny. 1972a. D e c o m p o s i t i o n o f d i s s o l v e d o r g a n i c carbon and n i t r o g e n compounds from l e a v e s i n an e x p e r i m e n t a l h a r d - w a t e r stream. L i m n o l . Oceanogr. 17: 927-931. . ., and H. L. A l l e n . 1972. F u n c t i o n s and i n t e r -a c t i o n s o f d i s s o l v e d o r g a n i c m a t t e r and the l i t t o r a l zone i n l a k e m e t a b o l i s m and e u t r o p h i c a t i o n . I n : Z. Kaj a k and A. H i l l b r i c h t - I l k o w s k a ( e d s . ) . P r o d u c t i v i t y Problems o f F r e s h w a t e r s . p. 333-347. W i l l i a m s , W. A., D. S. M i k k e l s e n , K. E. M u e l l e r , and J . E. Ruckman. 1968. N i t r o g e n i m m o b i l i z a t i o n by r i c e s t r a w i n c o r p o r a t e d i n l o w l a n d r i c e p r o d u c t i o n . P l a n t S o i l 28: 49-60. W i l s o n , D. 0. 1972. Phosphate n u t r i t i o n o f the a q u a t i c angiosperm, M y r i o p h y l l u m e x a l b e s c e n s F e r n . L i m n o l . Oceanogr. 17: 612-616. Zimmerman, R.:, and L. M e y e r - R e i l . 1974. A new method f o r f l u o r e s c e n c e s t a i n i n g o f b a c t e r i a l p o p u l a t i o n s on membrane, f i l t e r s . K i e l . M e e r e s f o r . 30: 24-27. APPENDIX A Simultaneous A n a l y s i s of T o t a l Nitrogen and Phosphorus i n MyriophyHum Tissue. 138 APPENDIX A S i m u l t a n e o u s A n a l y s i s o f T o t a l N i t r o g e n and Phosphorus i n  M y r i o p h y l l u m Tissue.. The n u t r i e n t t i s s u e a n a l y s e s o f M y r i o p h y l l u m r e q u i r e d a s u i t a b l e p r o c e d u r e w h i c h would p r o v i d e a c c u r a t e r e s u l t s o f t o t a l P and t o t a l N t i s s u e c o n t e n t s and most i m p o r t a n t o f a l l would r e q u i r e o n l y s m a l l samples.. T h i s l a t t e r c o n s i d e r a t i o n was e s p e c i a l l y i m p o r t a n t i n the l a b o r a t o r y e x p e r i m e n t , s i n c e o n l y l i m i t e d amounts o f p l a n t m a t t e r were a v a i l a b l e f o r a l l o f the r e q u i r e d c h e m i c a l a n a l y s e s . The problem o f f i n d i n g a s u i t a b l e a n a l y t i c a l t e c h n i q u e was r e s o l v e d by a s e r i e s o f p r e l i m i n a r y e x p e r i m e n t s w h i c h i n v e s t i g a t e d the f e a s i b i l i t y o f combining a s t a n d a r d t o t a l N and t o t a l P p l a n t t i s s u e a n a l y s i s i n t o a s i n g l e a n a l y t i c a l p r o c e d u r e . F o r t o t a l N t i s s u e a n a l y s i s o f p l a n t m a t e r i a l , semi-m i c r o m o d i f i c a t i o n s o f the K j e l d a h l p r o c e d u r e are o f t e n p r e -f e r r e d because they are more e f f i c i e n t , use l e s s r e a g e n t and r e q u i r e l e s s sample. A r e c e n t d e s c r i p t i o n of a s e m i - m i c r o K j e l d a h l p r o c e d u r e i s o u t l i n e d by N e l s o n and Sommers (1973), and t h i s method was used i n t h e s i m u l t a n e o u s p r o c e d u r e d e v e l o p e d i n t h i s s t u d y . E i t h e r wet o r d r y a s h i n g o f p l a n t t i s s u e samples can be used i n p r e p a r a t i o n f o r t o t a l P a n a l y s i s . A wet a s h i n g method as o u t l i n e d by Chapman and P r a t t (1961) was used. F o r t h e f i n a l d e t e r m i n a t i o n o f P i n the d i g e s t e d p l a n t m a t e r i a l , t h e 139 stannous c h l o r i d e r e d u c t i o n method f o r phosphate d e t e r m i n a t i o n as o u t l i n e d i n S t a n d a r d Methods (1971) was used. The f o l l o w i n g r a t i o n a l e was used i n d e c i d i n g t o combine the two p r o c e d u r e s , d e s c r i b e d above,, i n t o one. S i n c e b o t h a n a l y s e s f o r t o t a l N and P r e q u i r e the sample t o be i n i t i a l l y wet ashed, i t was d e c i d e d t o i n v e s t i g a t e the s u i t a b i l i t y o f i n c o r p o r a t i n g P d e t e r m i n a t i o n s i n t o t h e K j e l d a h l p r o c e d u r e . That i s , a subsample t a k e n from K j e l d a h l d i g e s t s h o u l d be s u i t a b l e f o r P d e t e r m i n a t i o n . I n t h i s way, a K j e l d a h l d i g e s t i o n i s used i n l i e u o f c o n v e n t i o n a l wet a s h i n g r e q u i r e d f o r P d e t e r m i n a t i o n , t h e r e b y i n c o r p o r a t i n g two a n a l y s e s (N and P) i n t o one. I n o r d e r t o t e s t t h i s i d e a , r e s u l t s o b t a i n e d from the P a n a l y s i s d e s c r i b e d p r e v i o u s l y were compared t o P d e t e r -m i n a t i o n s o f K j e l d a h l d i g e s t u s i n g M y r i o p h y l l u m t i s s u e as samples. I f l i t t l e s i g n i f i c a n t d i f f e r e n c e e x i s t e d between the d a t a , t h e n u s i n g K j e l d a h l d i g e s t f o r P d e t e r m i n a t i o n would be a c c e p t a b l e . R e s u l t s o f d u p l i c a t e a n a l y s e s u s i n g M y r i o p h y l l u m from b o t h s t u d y s i t e s (Cedar V a l l e y Pond and Iona R e s e r v o i r ) -showed v e r y good agreement between P d e t e r m i n a t i o n s o f K j e l d a h l d i g e s t and t h e s t a n d a r d P method (Table X I X ) . Thus, d i g e s t from the s e m i - m i c r o K j e l d a h l method a c c u r a t e l y accommodated an a d d i t i o n a l P d e t e r m i n a t i o n . F u r t h e r m o r e , d u p l i c a t e a n a l y s e s o f t o t a l P and N t i s s u e c o n t e n t s c o u l d be a c c u r a t e l y p e r f ormed on a s i n g l e sample o f M y r i o p h y l l u m T a b l e XIX.Comparison o f P t i s s u e c o n c e n t r a t i o n s i n M y r i o p h y l l u m u s i n g : (a) S t a n d a r d wet a s h i n g o r (L~) K j e l d a h l d i g e s t i o n . Sample Weight mg P e r c e n t PO.-P d r y wt a b. a b M. h i p p u r o i d e s 1 104. 2 227. 0 0. 12 0. 12 Cedar V a l l e y Pond 2 96. 3 204. 7 0. 12 0. 12 M. spicatum: 1 ' 231. 2 221. 4 0. 32 0. 32 Iona R e s e r v o i r 2 230. 2 230. 2 0. 32 0. 29 141 t i s s u e as s m a l l a,s 100 mg. F u r t h e r s t a t i s t i c a l i n v e s t i g a t i o n s - , u s i n g 5 r e p l i c a t e samples o f m i l f o i l measured i n d u p l i c a t e , showed t h a t the s i m u l t a n e o u s p r o c e d u r e d e v e l o p e d i n t h i s s t u d y measures t o t a l N ( p e r c e n t dry wt) t o ±0.08 and t o t a l P ( p e r c e n t d r y wt) t o ±0.01 ( ± s t a n d a r d e r r o r ) . The f o l l o w i n g i s a d e t a i l e d d e s c r i p t i o n o f the p r o c e d u r e used t o s i m u l t a n e o u s l y d e t e r m i n e N and P t i s s u e c o n t e n t s i n M y r i o p h y l l u m . To p r e p a r e a q u a t i c macrophytes f o r the N and P a n a l y s i s , f r e s h p l a n t m a t e r i a l was c a r e f u l l y r i n s e d w i t h t a p w a t e r t o remove most a d h e r i n g m a t t e r , d r i e d f o r 24 hours a t 60 C, ground i n a W i l e y m i l l o r m o r t a r and p e s t l e t o pass a 40-mesh s c r e e n ( 0,7 mm ) and s t o r e d i n g l a s s v i a l s . A 100 mg p l a n t sample was p l a c e d i n t o a c l e a n , d r y F o l i n - W u d i g e s t i o n tube and 1.1 g o f s a l t - c a t a l y s t m i x t u r e (100 g K 2 S 0 4 : 10 g CuS0 4 . 5 H 20 : 1 g Se) and 4 ml o f c o n c e n t r a t e d H 2 S 0 4 were added. The tube was s w i r l e d t o mix t h e sample and d i g e s t i o n r e a g e n t s and t h e n p l a c e d i n t o an aluminum h e a t i n g b l o c k p r e h e a t e d t o 300 C. A s m a l l g l a s s f u n n e l (25 mm d i a m e t e r ) was p l a c e d i n . the mouth of the tubes t o ensure e f f i c i e n t r e f l u x i n g o f the d i g e s t i o n m i x t u r e and p r e v e n t l o s s o f I-^SO^. The sample, was d i g e s t e d a t t h e b o i l i n g p o i n t o f the m i x t u r e f o r 6 0 minutes p a s t the time o f c l e a r i n g , removed from the h e a t i n g b l o c k , and a l l o w e d t o c o o l a t room 142 temperature. The d i g e s t was d i l u t e d to the 50 ml mark i n -s c r i b e d on the d i g e s t i o n tube, stoppered, and mixed .by i n -v e r t i n g s e v e r a l times. Ammonium i n the d i g e s t was then determined by making an a l i q u o t (e.g., 10 ml) a l k a l i n e w i t h 10 N'NaOH and performing a steam d i s t i l l a t i o n , c o l l e c t -i n g the d i s t i l l a t e i n b o r i c a c i d and t i t r a t i n g w i t h a standard a c i d . . The s o l u t i o n remaining i n the d i g e s t i o n tube was f i l t e r e d through Whatman number 41 ashless f i l t e r s and s u i t a b l e a l i q u o t s ( u s u a l l y 1 - 5 ml) were c a r e f u l l y p i p e t t e d i n t o a c i d washed 50 ml volumetric f l a s k s . A l l samples were brought to a standard pH l e v e l by n e u t r a l i z i n g w i t h NaOH to a phenophthalein end p o i n t (pH 8.3). Samples were now ready f o r c o l o u r development using the stannous c h l o r i d e r e d u c t i o n procedure f o r phosphate determination (Standard Methods 1971). 

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