The trophic state of North Carolina lakes

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THE

TROPHIC STATE OF NORTH CAROLINA LAKES

C h a r l e s M. Weiss and

Edward J. K u e n z l e r

Department o f E n v i r o n m e n t a l S c i e n c e s and E n g i n e e r i n g S c h o o l o f P u b l i c H e a l t h

U n i v e r s i t y o f N o r t h C a r o l i n a a t Chapel H i l l C h a p e l H i l l , N o r t h C a r o l i n a 27514

The work upon which t h i s p u b l i c a t i o n i s b a s e d was s u p p o r t e d i n p a r t by f u n d s p r o v i d e d by t h e O f f i c e of Water R e s o u r c e s a n d T e c h n o l o g y , U.S. Department of I n t e r i o r , t h r o u g h t h e Water R e s o u r c e s R e s e a r c h I n s t i t u t e of The U n i v e r s i t y of N o r t h C a r o l i n a as a u t h o r i z e d u n d e r t h e Water R e s o u r c e s R e s e a r c h Act o f 1 9 6 4 , a s amended.

P r o j e c t No. A-078-NC

Agreement No. 14-31-0001-5033

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ACKNOWLEDGEMENTS

T h i s i n v e s t i g a t i o n b a s e d on d a t a a s s e m b l e d i n t h e p e r i o d 1971-1975 r e f l e c t s t h e e f f o r t s o f many i n d i v i d u a l s who p a r t i c i p a t e d i n t h e c o l l e c t i o n a n d a s s e s s m e n t of t h e q u a l i t y o f t h e h u n d r e d s o f w a t e r s a m p l e s . T h i s

i n f o r m a t i o n a o n s t i t u t e s t h e d a t a p o o l of t h i s document. R e s p o n s i b i l i t y f o r n e a r l y a l l o f t h e f i e l d work s h o u l d b e i d e n t i f i e d w i t h M r . T e r r y P. Anderson and Mark Mason. M r . A n d e r s o n ' s comments, s u g g e s t i a n s a n d r e v i e w of d r a f t s h a v e b e e n p a r t i c u l a r l y h e l p f u l a n d s h o u l d b e s p e c i f i c a l l y acknowledged. C h r i s t o p h e r F. Knud-Hansen had t h e p r i m a r y r e s p o n s i b i l i t y i n c o l l e c t i n g

s a m p l e s f r o m t h e m i l l ponds and w e s t e r n l a k e s . L a b o r a t o r y a n a l y s e s ,

p a r t i c u l a r l y t h e a l g a l n u t r i e n t s , w e r e c a r r i e d o u t u n d e r t h e s u p e r v i s i o n o f M s . Susan R a p p a p o r t and M s . C a r o l P a r k e r . A l l of t h e p h y t o p l a n k t o n a n a l y s e s w e r e c a r r i e d o u t by D r . P e t e r H. Campbell. Coding and c h e c k i n g of t h e

o b s e r v a t i o n s t o p r e p a r e them f o r computer p r o c e s s i n g was t h e r e s p o n s i b i l i t y o f M s . Ann S c o t t . The t y p i n g of t h e numerous t a b l e s a n d many d r a f t s o f t h e t e x t was a t a s k c a r r i e d o u t w i t h g r e a t p a t i e n c e by M r s . E l i z a b e t h Walker.

Over t h e p e r i o d of t i m e i n which t h e h u n d r e d s o f o b s e r v a t i o n s o f t h i s r e p o r t w e r e g a t h e r e d , t h e r e w e r e s e v e r a l o r g a n i z a t i o n s and t h e i r s p e c i f i c p r o j e c t s which c o n t r i b u t e d d i r e c t l y o r i n d i r e c t l y t o t h e t o t a l d a t a b a s e . Although t h i s r e p o r t i s i d e n t i f i e d and p u b l i s h e d as a p r o j e c t s p o n s o r e d by t h e Water R e s o u r c e s R e s e a r c h I n s t i t u t e , t h e d a t a b a s e b o t h p r e c e d e s and p o s t d a t e s

t h e p e r i o d o f s u p p o r t of t h i s s p e c i f i c p r o j e c t . O t h e r o r g a n i z a t i o n s a n d t h e i r p r o j e c t s t h a t c o n t r i b u t e d by t h e d a t a p o o l s h o u l d b e acknowledged as f o l l o w s :

U . S . Army Corps of E n g i n e e r s , Wilmington D i s t r i c t , The J o h n H . K e r r R e s e r v o i r ; Duke Power Company, t h e Lower Catawba Lakes and Belews Lake; t h e N o r t h C a r o l i n a S c i e n c e and Technology Committee, Taxonomy a n d Ecology o f t h e P h y t o p l a n k t o n of N o r t h C a r o l i n a .

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ABSTRACT

Water q u a l i t y d a t a a s s e m b l e d o v e r t h e p e r i o d 1971-1975 f r o m t h e l a k e s and impoundments of N o r t h C a r o l i n a c o n s t i t u t e d a d a t a p o o l of 8 5 4 o b s e r v a t i o n s t h a t w e r e used t o d e s c r i b e t h e i r t r o p h i c s t a t e .

Each of t h e 8 5 4 o b s e r v a t i o n s was c o n s i d e r e d a microcosm and was d e s c r i b e d i n t e r m s of i t s p h y s i c a l and c h e m i c a l e n v i r o n m e n t and t h e c o n t a i n e d m i c r o f l o r a ( p h y t o p l a n k t o n ) . By means of c o m p u t e r i z e d s o r t i n g p r o c e d u r e s a n d e x a m i n a t i o n of known and i m p l i e d r e l a t i o n s h i p s o f more t h a n 20 v a r i a b l e s f o r e a c h

o b s e r v a t i o n i t was d e t e r m i n e d t h a t t o t a l p h o s p h o r u s , c o n d u c t i v i t y , and t h e p o l l u t i o n i n d e x had t h e most c o n s i s t e n t and s t r o n g e s t c o r r e l a t i o n s w i t h m e a s u r e s of t r o p h i c s t a t e .

U t i l i z i n g t h e s e , p l u s S e c c h i d i s k d e p t h , a s i x - s t e p t r o p h i c s c a l e was d e f i n e d f o r North C a r o l i n a w a t e r s r a n g i n g from o l i g o t r o p h i c t o h y p e r e u t r o p h i c . A t o t a l o f 69 l a k e s , r e s e r v o i r s , o r s u b s e g m e n t s of r e s e r v o i r s w e r e a c c o r d i n g l y c l a s s i f i e d : 8 o l i g o t r o p h i c ; 1 5 o l i g o - m e s o t r o p h i c ; 24 m e s o t r o p h i c ; 1 7

a - e u t r o p h i c ; 3 6 - e u t r o p h i c ; and 2 h y p e r e u t r o p h i c . R e l a t i n g t h i s s i x - s t e p t r o p h i c s c a l e t o t h e mean d e p t h of 4 1 of t h e s e b o d i e s of w a t e r r e v e a l e d a s t r o n g and s i g n i f i c a n t n e g a t i v e c o r r e l a t i o n t h a t i d e n t i f i e d a mean d e p t h of 15-20 f t . a s b e i n g a c r i t i c a l v a l u e f o r w a t e r s of h i g h q u a l i t y , low o n t h e t r o p h i c s c a l e . The i m p l i c a t i o n i s t h a t s h a l l o w l a k e s i n t h e N o r t h C a r o l i n a d r a i n a g e s c a n n o t b e e x p e c t e d t o b e much lower t h a n m e s o t r o p h i c ( 3 i n t h e s i x s t e p s c a l e ) .

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TABLE OF CONTENTS (Continued)

Page

. . .

APPENDICES 111

Appendix A. L o c a t i o n , S i z e and Q u a l i t y C h a r a c t e r i s t i c s of S u r f a c e Waters of North C a r o l i n a and Immediate Adjacent Areas Sampled f o r T r o p h i c A n a l y s i s ,

. . .

1971-1975 111

Appendix B . Trophic S t a t e D e s c r i p t o r s of Lakes and Impoundments

. . .

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LIST OF FIGURES

P a g e

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LIST OF TABLES

P a g e 1. S u r f a c e Waters o f N o r t h C a r o l i n a and Immediate A d j a c e n t A r e a s

. . .

Sampled f o r T r o p h i c S t a t e A n a l y s i s 1971-1975 7

3 . T r o p h i c S t a t e I n d e x (TSI) and A s s o c i a t e d P a r a m e t e r s

. . .

1 7

4.

Mean V a l u e s o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s

of Lake Samples C o l l e c t e d f o r T r o p h i c A n a l y s i s , S e a s o n a l

. . .

C h a n g e s b y M o n t h . . 2 0

5 . Mean V a l u e s o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s

W i t h i n V a l u e Ranges o f I n d i c a t e d P a r a m e t e r , T e m p e r a t u r e O C

. . . .

26 6. Mean V a l u e s o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s

W i t h i n V a l u e Ranges of I n d i c a t e d P a r a m e t e r , S e c c h i Depth

-

. . .

M e t e r s . 2 9

7 . Mean V a l u e s o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s W i t h i n Value Ranges of I n d i c a t e d P a r a m e t e r , NH3-N mg/m3,

. . .

March

-

November 3 1

8. Mean V a l u e s of P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s W i t h i n V a l u e Ranges of I n d i c a t e d P a r a m e t e r , NH3-N mg/m3,

. . .

December

-

F e b r u a r y . 3 2

9 . Mean V a l u e s of P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s W i t h i n V a l u e Ranges of I n d i c a t e d P a r a m e t e r , N02N03-N m g / m 3 ,

. . .

March

-

November 34

1 0 . Mean V a l u e s of P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s W i t h i n V a l u e Ranges o f I n d i c a t e d P a r a m e t e r , N02N03-N m g / m 3 ,

. . .

D e c e m b e r - F e b r u a r y . 3 5

11. Mean V a l u e s of P h y s i c a l , Chemical a n d B i o l o g i c a l P a r a m e t e r s W i t h i n V a l u e Ranges o f I n d i c a t e d P a r a m e t e r , Inorg-N mg/m3,

. . .

March

-

November 36

1 2 . Mean V a l u e s of P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s W i t h i n Value Ranges of I n d i c a t e d P a r a m e t e r , Inorg-N mg/m3,

. . .

December

-

F e b r u a r y 37

1 3 . Mean V a l u e s of P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s W i t h i n V a l u e Ranges of I n d i c a t e d P a r a m e t e r , K j el-N mg/m3,

. . .

M a r c h - N o v e m b e r . - 3 8

1 4 . Mean V a l u e s of P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s W i t h i n V a l u e Ranges of I n d i c a t e d P a r a m e t e r , K j el-N mg/m3,

. . .

D e c e m b e r - F e b r u a r y . 3 9

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LIST OF TABLES ( C o n t i n u e d )

Page

1 5 . Mean V a l u e s o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s

. . .

W i t h i n V a l u e Ranges o f I n d i c a t e d P a r a m e t e r , Org-N rng/m3 4 0 1 6 . Mean V a l u e s o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s

W i t h i n V a l u e Ranges o f I n d i c a t e d P a r a m e t e r , P04-P

mg/m3,

March

-

November

. . .

4 2

1 7 . Mean V a l u e s o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s W i t h i n Value Ranges o f I n d i c a t e d P a r a m e t e r , P04-P rng/m3,

December

-

F e b r u a r y

. . .

4 3

1 8 . Mean V a l u e s o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s W i t h i n V a l u e Ranges of I n d i c a t e d P a r a m e t e r , T o t a l S o l u b l e P

mg/m3,

March

-

November

. . .

4 4

1 9 . Mean V a l u e s o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s W i t h i n V a l u e Ranges of I n d i c a t e d P a r a m e t e r , T o t a l S o l u b l e P

mg/m3, December

-

F e b r u a r y

. . .

4 5 2 0 . Mean V a l u e s o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s

W i t h i n Value Ranges o f I n d i c a t e d P a r a m e t e r , S o l u b l e Org-P

mg/rn3, March

-

November

. . .

W i t h i n V a l u e Ranges of I n d i c a t e d P a r a m e t e r , S o l u b l e Org-P

mg/m3, December

-

F e b r u a r y

. . .

4 7 22. Mean V a l u e s of P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s

W i t h i n V a l u e Ranges of I n d i c a t e d P a r a m e t e r , P a r t i c u l a t e - P m g / m 3 , March

-

November

. . .

W i t h i n Value Ranges of I n d i c a t e d P a r a m e t e r , P a r t i c u l a t e - P m g / m 3 , December

-

F e b r u a r y

. . .

4 9

2 4 . Mean V a l u e s of P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s W i t h i n V a l u e Ranges of I n d i c a t e d P a r a m e t e r , T o t a l - P mg/m3,

. . .

M a r c h - N o v e m b e r 50

25. Mean V a l u e s o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s W i t h i n Value Ranges o f I n d i c a t e d P a r a m e t e r , T o t a l - P mg/m3,

December

-

F e b r u a r y

. . .

5 1 26. C o r r e l a t i o n C o e f f i c i e n t s ( r ) a s c a l c u l a t e d Between P h o s p h o r u s

Components,Soluble N i t r o g e n Components,and C o n d u c t i v i t y and

D i r e c t o r I n d i r e c t Measures of B i o l o g i c a l A c t i v i t y

. . .

5 2 27. Mean V a l u e s o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s

W i t h i n V a l u e Ranges of I n d i c a t e d P a r a m e t e r , TN/TP

March

-

November

. . .

5 4

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Page 28. Mean V a l u e s o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s

W i t h i n V a l u e Ranges of I n d i c a t e d P a r a m e t e r , T N / T P ,

. . .

December

-

F e b r u a r y 55

29. Mean V a l u e s o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s W i t h i n Value Ranges of I n d i c a t e d P a r a m e t e r , I n o r g N/Sol P ,

M a r c h - N o v e m b e r . . . , . . . 5 6 30. Mean V a l u e s o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s

W i t h i n V a l u e Ranges o f I n d i c a t e d P a r a m e t e r , I n o r g N/Sol P ,

. . .

December

-

F e b r u a r y

57

31. Mean V a l u e s o f P h y s i c a l , Chemical a n d B i o l o g i c a l P a r a m e t e r s

W i t h i n V a l u e Ranges of I n d i c a t e d P a r a m e t e r , A l k a l i n i t y m g / l

,

. . .

March

-

November 58

32. Mean V a l u e s o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s

W i t h i n V a l u e Ranges of I n d i c a t e d P a r a m e t e r , A l k a l i n i t y m g / l

,

. . .

December

-

F e b r u a r y 59

33. Mean V a l u e s o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s

W i t h i n V a l u e Ranges o f I n d i c a t e d P a r a m e t e r , C o n d u c t i v i t y umhos/cm

. . .

March

-

November 60

34. Mean Values o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s

W i t h i n Value Ranges of I n d i c a t e d P a r a m e t e r , C o n d u c t i v i t y ~ m h o s / c m December

-

F e b r u a r y

. . .

6 1

35. Mean V a l u e s of P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s

W i t h i n V a l u e Ranges o f I n d i c a t e d P a r a m e t e r , C e l l D e n s i t y n o / m l , M a r c h - N o v e m b e r . . . 6 2 36. Mean V a l u e s o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s

W i t h i n V a l u e Ranges o f I n d i c a t e d P a r a m e t e r , C e l l D e n s i t y n o / m l ,

. . .

December

-

F e b r u a r y 64

37. Mean V a l u e s o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s W i t h i n V a l u e Ranges o f I n d i c a t e d P a r a m e t e r , Biovolume m m 3 / m 3 , M a r c h - N o v e m b e r . . . 6 5 38. Mean V a l u e s of P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s

W i t h i n V a l u e Ranges of I n d i c a t e d P a r a m e t e r , Biovolume m 3 / m 3 ,

December

-

F e b r u a r y

. . .

W i t h i n Value Ranges o f I n d i c a t e d P a r a m e t e r , Ln C e l l D e n s i t y ,

March

-

November

. . .

6 7 40. Mean V a l u e s o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s

W i t h i n V a l u e Ranges o f I n d i c a t e d P a r a m e t e r , Ln C e l l D e n s i t y ,

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P a g e Mean V a l u e s o f P h y s i c a l and B i o l o g i c a l P a r a m e t e r s

W i t h i n Value Ranges o f I n d i c a t e d P a r a m e t e r , Ln Biovolume,

M a r c h - N o v e m b e r .

. . .

Mean V a l u e s of P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s

W i t h i n V a l u e Ranges o f I n d i c a t e d P a r a m e t e r , Ln Biovolume,

December

-

F e b r u a r y

. . .

Mean V a l u e s of P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s

W i t h i n V a l u e Ranges o f I n d i c a t e d P a r a m e t e r , C h l o r o p h y l l

-

a

-

T u r n e r U n i t s , March

-

November

. . .

Mean V a l u e s o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s

W i t h i n Value Ranges o f I n d i c a t e d P a r a m e t e r , C h l o r o p h y l l

-

a

-

. . .

T u r n e r U n i t s , December

-

F e b r u a r y

Mean V a l u e s o f P h y s i c a l , Chemical and B i o l o g i c a l P a r a m e t e r s W i t h i n V a l u e Ranges of I n d i c a t e d P a r a m e t e r , P r o d u c t i v i t y mg

. . .

c / m 3 / h r . , March

-

November

Mean V a l u e s of P h y s i c a l Chemical and B i o l o g i c a l P a r a m e t e r s W i t h i n Value Ranges o f I n d i c a t e d P a r a m e t e r , P r o d u c t i v i t y mg

. . .

c / m 3 / h r . , December

-

F e b r u a r y

A Q u a l i t y P r o f i l e o f N o r t h C a r o l i n a W a t e r s , Mean V a l u e s of Peak Frequency Ranges and P e r c e n t of T o t a l Sample T h a t Account o f

. . .

A p p r o x i m a t e l y 80% of A l l Samples

Mean V a l u e s of T r o p h i c S t a t e I n d i c e s D e r i v e d f r o m Lake Samples C o l l e c t e d f o r T r o p h i c A n a l y s i s Arranged W i t h i n Value Range

o f Given I n d e x , Secchi-Depth-Meters

. . .

Mean V a l u e s o f T r o p h i c S t a t e I n d i c e s D e r i v e d from Lake Samples

C o l l e c t e d f o r T r o p h i c A n a l y s i s Arranged W i t h i n V a l u e Range

. . .

o f Given I n d e x , C h l o r o p h y l l

-

a m g / m 3

Mean V a l u e s of T r o p h i c S t a t e I n d i c e s D e r i v e d f r o m Lake Samples C o l l e c t e d f o r T r o p h i c A n a l y s i s Arranged W i t h i n V a l u e Range

. . .

o f Given I n d e x , C h l o r o p h y l l a T u r n e r U n i t s

Mean V a l u e s o f T r o p h i c S t a t e I n d i c e s D e r i v e d f r o m Lake Samples C o l l e c t e d f o r T r o p h i c A n a l y s i s Arranged W i t h i n V a l u e Range

o f Given I n d e x , TP ( T o t a l P h o s p h o r u s ) mg/m3

. . .

Mean V a l u e s of T r o p h i c S t a t e I n d i c e s D e r i v e d from Lake Samples

C o l l e c t e d f o r T r o p h i c A n a l y s i s Arranged W i t h i n Value Range of Given I n d e x , Cell D e n s i t y n o . / m l

. . .

Mean V a l u e s of T r o p h i c S t a t e I n d i c e s D e r i v e d f r o m Lake Samples

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Page 54. Mean V a l u e s of T r o p h i c S t a t e I n d i c e s D e r i v e d from Lake Samples

C o l l e c t e d f o r T r o p h i c A n a l y s i s A r r a n g e d W i t h i n Value Range o f

. . .

Given I n d e x , P I ( P o l l u t i o n I n d e x ) 82

55. Mean V a l u e s o f T r o p h i c S t a t e I n d i c e s D e r i v e d from Lake Samples C o l l e c t e d f o r T r o p h i c A n a l y s i s Arranged W i t h i n V a l u e Range of

. . .

Given I n d e x , C o n d u c t i v i t y pmho 8 3

56. C o r r e l a t i o n C o e f f i c i e n t s ( r ) As C a l c u l a t e d Between Rank S e r i e s o f T r o p h i c I n d i c e s and Mean V a l u e s o f A s s o c i a t e d I n d i c e s Determined

. . .

on t h e Same Sample 84

57. The C o r r e l a t i o n o f T o t a l P h o s p h o r u s , C o n d u c t i v i t y and P o l l u t i o n I n d e x A s T r o p h i c S t a t e I n d i c e s and Mean V a l u e s of A l g a l Growth

. . .

Measures, C o r r e l a t i o n C o e f f i c i e n t s ( r ) 8 5 58. S u r f a c e W a t e r s of N o r t h C a r o l i n a a n d Immediate A d j a c e n t Areas

Sampled f o r T r o p h i c S t a t e A n a l y s i s 1971-1975, D i s s o l v e d

. . .

Oxygen C o n t e n t of Mid-Summer H y p o l i m n e t i c Samples 87 59. S e l e c t e d T r o p h i c I n d i c e s o f S u r f a c e W a t e r s o f N o r t h C a r o l i n a and

. . .

A d j a c e n t A r e a s 9 1

60. Range of T r o p h i c C l a s s i f i c a t i o n S u g g e s t e d f o r N o r t h C a r o l i n a Lakes

.

95 61. Proposed T r o p h i c S t a t e o f N o r t h C a r o l i n a a n d A d j a c e n t

. . .

Areas 96

62. Summary o f T r o p h i c C l a s s i f i c a t i o n s of N o r t h C a r o l i n a Lakes and Impoundments . . . 9 9

6 3 . R e l a t i o n s h i p o f T r o p h i c S t a t e and Mean D e p t h , 4 1 Lakes o r

. . .

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SUMMARY AND CONCLUSIONS

The t r o p h i c s t a t e of a body of w a t e r i s a c h a r a c t e r i s t i c r e s u l t i n g f r o m t h e i n t e r a c t i o n of many p h y s i c a l , c h e m i c a l and b i o l o g i c a l f a c t o r s . I t i s t h e c o n d i t i o n which d e s c r i b e s t h e r e l a t i v e l e v e l of n u t r i e n t r i c h n e s s and n u t r i e n t u t i l i z a t i o n i n o r g a n i c p r o d u c t i o n . Changes i n t r o p h i c s t a t e as a c o n s e q u e n c e o f n u t r i e n t e n r i c h m e n t g e n e r a l l y i n c r e a s e s p r o d u c t i o n of a l g a e and o t h e r a q u a t i c p l a n t s , s h i f t s t h e q u a l i t y of t h e f i s h e r y f r o m game t o c o u r s e s p e c i e s p l u s o t h e r c h a n g e s i n w a t e r q u a l i t y t h a t may b e o b j e c t i o n a b l e and i m p a i r w a t e r u s e .

Water q u a l i t y i n v e s t i g a t i o n s c a r r i e d o u t p r i n c i p a l l y between 1 9 7 1 and 1975 h a v e p e r m i t t e d t h e t r o p h i c s t a t e c l a s s i f i c a t i o n of 69 b o d i e s of w a t e r i n N o r t h C a r o l i n a and b o r d e r i n g a r e a s . These i n c l u d e a r e p r e s e n t a t i v e s a m p l e of t h e l i m i t e d number of n a t u r a l l a k e s ( e i g h t i n t h i s s t u d y ) as w e l l a s a p p r o p r i a t e examples o f m u n i c i p a l w a t e r s u p p l y r e s e r v o i r s , c o o l i n g w a t e r impoundments f o r s t e a m e l e c t r i c g e n e r a t i o n , hydropower r e s e r v o i r s , f l o o d c o n t r o l impoundments and o t h e r m u l t i p l e - p u r p o s e r e s e r v o i r s , a s w e l l as a s e r i e s of o l d m i l l ponds d a t i n g b a c k t o t h e 1 8 t h c e n t u r y .

The s a m p l i n g program c o l l e c t e d a w i d e s p e c t r u m of w a t e r q u a l i t y p a r a m e t e r s . I t was b a s e d on a monthly s a m p l i n g f r e q u e n c y where p o s s i b l e , i n o r d e r t o d e f i n e s e a s o n a l c h a n g e s , o r a minimum of t w i c e y e a r l y i n l a t e w i n t e r o r e a r l y s p r i n g t o c o i n c i d e w i t h t h e s e a s o n a l m i x i n g and a g a i n i n mid-summer, g e n e r a l l y t h e

p e r i o d o f maximum g r o w t h . These o b s e r v a t i o n s w e r e u s e d t o d e s c r i b e t h e p h y s i c a l , c h e m i c a l and b i o l o g i c a l c h a r a c t e r i s t i c s t h a t w e r e i n t e g r a t e d i n t o a s t a t e m e n t of t r o p h i c q u a l i t y . I n t h e p r o c e s s of e v a l u a t i n g v a r i o u s w a t e r q u a l i t y

d i m e n s i o n s , t h e i r d e g r e e of c o r r e l a t i o n w i t h t r o p h i c c o n d i t i o n s , i t was

found t h a t c l a s s i f i c a t i o n b a s e d on t o t a l p h o s p h o r u s , c o n d u c t i v i t y , and S e c c h i d i s k t r a n s p a r e n c y c o u l d b e used i n d e p e n d e n t l y o r i n a s s o c i a t i o n t o d e s c r i b e a l a k e i n t h e r a n g e of t r o p h i c q u a l i t y e x t e n d i n g f r o m o l i g o t r o p h i c t o h y p e r e u t r o p h i c i n s i x s t e p s . The term o l i g o t r o p h i c i s t h e t r o p h i c s t a t e a s s o c i a t e d w i t h low q u a n t i t i e s o f n u t r i e n t s , c l e a r w a t e r s and p o o r f i s h i n g p o t e n t i a l w h e r e a s t h e h y p e r e u t r o p h i c c o n d i t i o n i s o n e of e x c e s s n u t r i e n t s , h i g h l y t u r b i d w a t e r s and c o a r s e f i s h s p e c i e s .

U t i l i z i n g t h e d e f i n i t i o n s of t r o p h i c s t a t e , a s d e f i n e d by o n e o f t h e s i x c l a s s e s ( o l i g o t r o p h i c , o l i g o - m e s o t r o p h i c , m e s o t r o p h i c , a - e u t r o p h i c , B - e u t r o p h i c , h y p e r e u t r o p h i c ) , t h e c o n d i t i o n of t h e v a r i o u s b o d i e s of w a t e r o r s u b s e g m e n t s

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was a l s o r e l a t e d t o s u r f a c e a r e a and g e o g r a p h i c a l d i s t r i b u t i o n . The

c o n c l u s i o n t h a t may b e drawn i s t h a t t h e l a r g e r t h e l a k e t h e more p r o b a b l e t h a t i t would b e of h i g h e r q u a l i t y , low on t h e t r o p h i c s c a l e , and t h e l a k e s i n t h e m o u n t a i n s w e r e of h i g h e r q u a l i t y t h a n t h o s e of t h e Piedmont o r C o a s t a l P l a i n . R e l a t i n g t h e mean d e p t h o f 4 1 l a k e s t o t h e s i x s t e p t r o p h i c c l a s s i f i c a - t i o n showed a v e r y h i g h d e g r e e of c o r r e l a t i o n w i t h t h e d e e p e r w a t e r s b e i n g l o w e s t on t h e t r o p h i c s c a l e , o f h i g h e s t q u a l i t y . T h i s a n a l y s i s p r e d i c t s t h a t a n y body of w a t e r i n t h e N o r t h C a r o l i n a e n v i r o n m e n t w i t h a mean d e p t h of l e s s

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RECOMMENDATIONS

1. I t i s e s s e n t i a l t h a t w a s t e w a t e r c o n t r o l programs d i r e c t e d a t p o i n t s o u r c e d i s c h a r g e s b e d e s i g n e d w i t h i n t h e c o n t e x t of t h e r e c e i v i n g w a t e r s t o i n s u r e t h a t a n a p p r o p r i a t e s c a l e o f e f f e c t i v e n e s s b e a l l o c a t e d t o t h e c o s t of t h e c o n t r o l e f f o r t .

2 . I n t h e l a k e s and w a t e r q u a l i t y i s o n e s o u r c e d i s c h a r g e s o f t h a t i s s e n s i t i v e t o

impoundments o f N o r t h C a r o l i n a t h e r e l a t i v e l e v e l of g e n e r a l l y r e f l e c t i v e o f n u t r i e n t enhancement f r o m p o i n t m u n i c i p a l w a s t e w a t e r s . An a p p r o p r i a t e m o n i t o r i n g program c h a n g e s i n t h e n e t e f f e c t of n u t r i e n t e n r i c h m e n t s h o u l d r e c e i v e a h i g h p r i o r i t y s o t h a t l e v e l s of e x p e n d i t u r e f o r w a s t e w a t e r c o n t r o l programs may b e more p r e c i s e l y d e f i n e d .

3 . An e f f e c t i v e and r e l a t i v e l y i n e x p e n s i v e t r o p h i c s t a t e m o n i t o r i n g program i n N o r t h C a r o l i n a c a n b e e s t a b l i s h e d u t i l i z i n g t h e h i g h l y c o r r e l a t e d

p a r a m e t e r s o f t o t a l p h o s p h o r u s , c o n d u c t i v i t y , and S e c c h i d i s k d e p t h . One w a t e r s a m p l e on which b o t h t o t a l p h o s p h o r u s a n d c o n d u c t i v i t y can b e d e t e r m i n e d and a s i m p l e f i e l d d e t e r m i n a t i o n , S e c c h i d i s k d e p t h , made a t t h e t i m e a n d p l a c e o f t a k i n g t h e w a t e r s a m p l e s h o u l d p r o v i d e s u f f i c i e n t i n f o r m a t i o n t o m o n i t o r c h a n g e s i n t r o p h i c s t a t e .

4 .

The w a t e r sample s h o u l d b e t a k e n a t t h e S e c c h i d i s k d e p t h ( a p p r o x i m a t e l y 112 t h e d e p t h of t h e e u p h o t i c z o n e ) . Extreme c a r e s h o u l d b e t a k e n i n c l e a n i n g and h a n d l i n g of sample b o t t l e s t o a v o i d p h o s p h o r u s c o n t a m i n a t i o n . The

l a b o r a t o r y a n a l y s i s s h o u l d h a v e t h e c a p a b i l i t y of d e t e r m i n i n g t o t a l p h o s p h o r u s a t a l e v e l of

5

mg/m3 and p r e f e r a b l y 1 mg/m3. S e c c h i d e p t h s s h o u l d b e r e a d t o 0 . 1 meter.

5. Major r e c r e a t i o n a l w a t e r s s h o u l d b e m o n i t o r e d a t l e a s t t w i c e monthly May t h r o u g h September and a t s u f f i c i e n t number of s t a t i o n s a l o n g t h e l o n g a x i s of impoundments t o d e f i n e l o n g i t u d i n a l t r o p h i c g r a d i e n t s .

6 . I f a s t a t e - w i d e m o n i t o r i n g program of t h e i n l a n d l a k e s and r e s e r v o i r s

c a n b e b u d g e t e d t o i n c l u d e t h e r e q u i r e d p r o f e s s i o n a l manpower, t h e d e t e r m i n a t i o n o f t h e P o l l u t i o n I n d e x , t h e p r o p o r t i o n a l number of p h y t o p l a n k t o n t h a t h a v e b e e n d e f i n e d a s b e i n g a s s o c i a t e d w i t h n u t r i e n t r i c h a q u a t i c e n v i r o n m e n t s , w i l l

p r o v i d e a u n i q u e b i o l o g i c a l i n d i c a t o r o f changes i n n u t r i e n t l e v e l s and t r o p h i c s t a t e .

7 .

F u r t h e r r e s e a r c h i n t o t h e f e a s i b i l i t y of u s i n g t h e t h r e e o r f o u r t r o p h i c s t a t e i n d i c a t o r s t o m o n i t o r o r d e f i n e t r o p h i c c o n d i t i o n s would i n c l u d e s a m p l i n g

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INTRODUCTION

The n a t u r a l l a k e s of t h e C o a s t a l P l a i n and t h e many impoundments and r e s e r v o i r s of t h e Piedmont and Mountain p h y s i o g r a p h i c p r o v i n c e s of N o r t h C a r o l i n a r e f l e c t i n t h e i r c h a n g i n g t r o p h i c s t a t e s t h e p a r a l l e l c h a n g e s i n t h e

l i f e and t i m e s of t h e S t a t e of North C a r o l i n a . T h i s i n c l u d e s t h e s h i f t from a l a r g e l y r u r a l f a r m - o r i e n t e d s o c i e t y t o a more h i g h l y u r b a n i z e d i n d u s t r i a l i z e d s t a t e a s w e l l a s i n c r e a s i n g l y mechanized a g r i c u l t u r a l p r a c t i c e s w i t h i n t e n s i v e u s e of c h e m i c a l f e r t i l i z e r s . P a r a l l e l i n g t h e s e s h i f t s h a s b e e n a change i n l i f e s t y l e s , o n e a s p e c t b e i n g a n i n c r e a s i n g demand on w a t e r r e s o u r c e s f o r r e c r e a t i o n a l p u r p o s e s . The r e q u i r e m e n t t h a t w a t e r management a g e n c i e s

e s t a b l i s h contemporary q u a l i t y l e v e l s and p l a n f o r f u t u r e w a t e r u s e s e m p h a s i z e s t h a t c u r r e n t q u a l i t y b e d e f i n e d w i t h i n t h e c o n t e x t of u s e s and t h a t management programs r e c o g n i z e t h e l i m i t s of q u a l i t y improvement t h a t may b e e x p e c t e d w i t h i n t h e contemporary c u l t u r a l e n v i r o n m e n t of North C a r o l i n a .

The t r o p h i c s t a t e o f a l a k e o r impoundment i s a c h a r a c t e r i s t i c r e s u l t i n g from t h e i n t e r a c t i o n a n d r e l a t i o n s h i p of many p h y s i c a l , c h e m i c a l and b i o l o g i c a l f a c t o r s . I t i s t h e c o n d i t i o n of a body of w a t e r w h i c h d e s c r i b e s i t s r e l a t i v e r i c h n e s s w i t h r e s p e c t t o n u t r i e n t s and o r g a n i c p r o d u c t i o n . These h a v e b e e n w e l l i l l u s t r a t e d i n t h e a n a l o g model f i r s t s u g g e s t e d by Rawson ( 1 9 3 9 ) . They h a v e been r e d e f i n e d by o t h e r i n v e s t i g a t o r s i n t o a v a r i e t y of p h y s i c a l , c h e m i c a l a n d b i o l o g i c a l d i m e n s i o n s which may b e u s e d i n a r r i v i n g a t a n i n t e g r a t e d

s t a t e m e n t of t h e t r o p h i c s t a t e of a n i n d i v i d u a l body of w a t e r ( S t e w a r t and R o h l i c h , 1 9 6 7 ) . I t i s n o t o n l y t h e s p e c i f i c q u a l i t y o f t h e e x i s t i n g body of w a t e r t h a t i s of c o n c e r n and i n t e r e s t b u t t h o s e f a c t o r s which when g e n e r a t e d by man's c u l t u r a l a c t i v i t y may c a u s e a change i n w a t e r q u a l i t y i n t h e

d i r e c t i o n of r e d u c e d u s e f u l n e s s .

The c o n c e p t of t r o p h i c s t a t e o r c o n d i t i o n and t h e p r e c i s e meaning of t h e t e r m s g e n e r a l l y used a s d e s c r i p t o r s , o l i o g o t r o p h i c , m e s o t r o p h i c and e u t r o p h i c h a v e a l w a y s been t r o u b l e s o m e . T h i s h a s b e e n d u e t o t h e wide v a r i a t i o n and i n t e r p r e t a t i o n of t h e meaning of t h e s e t e r m s and t h e r e l a t i o n s h i p o f t h e measured q u a l i t y p a r a m e t e r s t h a t a r e a s s o c i a t e d w i t h them.

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d e t e r i o r a t i o n o f f i s h e r i e s , and o t h e r c h a n g e s i n w a t e r q u a l i t y which may b e o b j e c t i o n a b l e and i m p a i r w a t e r u s e . A l t h o u g h i t i s r e c o g n i z e d t h a t n u t r i e n t e n r i c h m e n t Fs a l s o a n a t u r a l p r o c e s s , i t i s a c c e l e r a t e d n u t r i e n t enhancement t h a t h a s r e q u i r e d d e v e l o p m e n t of n u t r i e n t c l a s s i f i c a t i o n s y s t e m s , t h e t r o p h i c s t a t e , f o r l a k e s a n d impoundments i n o r d e r t o e f f e c t a p p r o p r i a t e management p r o c e d u r e s

.

I n a n a t t e m p t t o d e a l w i t h t h e c o m p l e x i t i e s of t h e Rawson model and a r r i v e a t a d i r e c t method f o r d e s c r i b i n g t h e t r o p h i c s t a t e , a t t e m p t s h a v e b e e n made t o i n t e g r a t e t h e s e v e r a l v a r i a b l e s i n t h e model t o p r o d u c e a n u m e r i c a l s c a l e o r i n d e x which c o u l d b e used f o r management p u r p o s e s . These d e v e l o p m e n t s h a v e i n c l u d e d t h e p h o s p h o r u s l o a d i n g c o n c e p t s o f V o l l e n w e i d e r and D i l l o n

( 1 9 7 4 ) , and V o l l e n w e i d e r (1975, 1976) which h a v e been i n s t r u m e n t a l i n t h e development of p r o c e d u r e s f o r p r e d i c t i n g q u a l i t y b a s e d upon r a t e of p h o s p h o r u s i n p u t , l a k e volume and r e t e n t i o n t i m e . Another a p p r o a c h h a s b e e n t h e u s e of m u l t i v a r i a t e a n a l y s i s of w a t e r q u a l i t y p a r a m e t e r s by Shannon and B r e z o n i k

(1972) t o c l a s s i f y t h e l a k e s of F l o r i d a . A c l a s s i f i c a t i o n s y s t e m d e v e l o p e d f o r S o u t h A f r i c a n impoundments by T o e r i e n , e t a l . , (1975) draws h e a v i l y on much of t h e European and N o r t h American e x p e r i e n c e s b u t emphasizes t h e u s e of

a l g a l g r o w t h p o t e n t i a l . A s t a t e w i d e e f f o r t t o c l a s s i f y t h e t r o p h i c

c h a r a c t e r i s t i c s of W i s c o n s i n l a k e s by U t t o r m a r k and W a l l (1975) depended on a p o i n t s y s t e m d e r i v e d from f o u r p a r a m e t e r s ; d i s s o l v e d oxygen, t r a n s p a r e n c y , f i s h k i l l s and u s e i m p a i r m e n t , t o d e r i v e a l a k e c o n d i t i o n i n d e x . The

r e l a t i o n s h i p s d e v e l o p e d by D i l l o n and R i g l e r (1975) s i m p l i f i e s t h e p r o c e d u r e s f o r p r e d i c t i n g t h e c a p a c i t y of a l a k e t o h a n d l e n u t r i e n t s from s u r r o u n d i n g l a n d d e v e l o p m e n t , b a s e d on measurements of S e c c h i d i s k t r a n s p a r e n c y and

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N o r t h C a r o l i n a Lake and R e s e r v o i r S t u d i e s

Over t h e p a s t s e v e r a l d e c a d e s s p e c i a l s t u d i e s and i n v e s t i g a t i o n s h a v e b e e n c a r r i e d o u t on l a k e s and r e s e r v o i r s t h r o u g h o u t N o r t h C a r o l i n a . I n t h e e a r l y s i x t i e s t h e N o r t h C a r o l i n a W i l d l i f e Commission, as a b a s i s f o r

e s t a b l i s h i n g q u a l i t y f o r f i s h e r i e s o f t h e s e impoundments and l a k e s , c a r r i e d o u t l i m i t e d i n v e s t i g a t i o n s o n a s e r i e s o f t h e s e b o d i e s of w a t e r . More r e c e n t i n v e s t i g a t i o n s on s u c h i n d i v i d u a l l a k e s h a v e i n c l u d e d d e s t r a t i f i c a t i o n t o improve w a t e r q u a l i t y (Weiss and B r e e d l o v e , 1 9 7 3 ) , i n v e s t i g a t i o n s c o n c e r n e d w i t h t h e i m p a c t o f e l e c t r i c power g e n e r a t i n g p l a n t s u s i n g c o o l i n g w a t e r from s e l e c t e d l a k e s and impoundments (Weiss, e t a l . , 1975b) s p e c i f i c i n v e s t i g a t i o n s t o a s s e s s t h e c h a n g i n g t r o p h i c s t a t e of a newly impounded body of w a t e r t o u l t i m a t e l y b e used f o r c o o l i n g w a t e r p u r p o s e s ( W e i s s , e t a l . , 1 9 7 1 , 1 9 7 2 , 1 9 7 4 ,

_--

and l 9 7 5 a ) .

I n a d d i t i o n a d e t a i l e d a n a l y s i s o v e r a p e r i o d o f s e v e r a l y e a r s was c a r r i e d o u t on a m a j o r impoundment on t h e Roanoke R i v e r , t h e John H. Kerr R e s e r v o i r , o p e r a t e d by t h e Corps of E n g i n e e r s f o r f l o o d c o n t r o l and hydropower. T h i s body of w a t e r h a s proved t o b e of p a r t i c u l a r s i g n i f i c a n c e i n c h a r a c t e r i z i n g t h e t r o p h i c s t a t e o f l a k e s a n d impoundments of t h i s a r e a d u e t o t h e u n i q u e a r r a n g e m e n t of n u t r i e n t i n p u t from two m a j o r s o u r c e s p l u s v a r i a t i o n s i n r e t e n t i o n t i m e w i t h i n two arms o f t h e l a k e t h a t u l t i m a t e l y c o n v e r t s i n t o d i f f e r e n t l e v e l s of t r o p h i c c o n d i t i o n . T h i s p a r t i c u l a r i n v e s t i g a t i o n h a s b e e n a u n i t o f t h e N o r t h American P r o j e c t , s p o n s o r e d by OECD-EPA, t o examine t h e V o l l e n w e i d e r c o n c e p t s on l o a d i n g a n d r e t e n t i o n t i m e . The John H . K e r r R e s e r v o i r a n a l y s i s was s e l e c t e d t o s e r v e a s t h e t y p e impoundment f o r t h e w a t e r s o f t h e S o u t h e a s t . P r e l i m i n a r y r e p o r t s h a v e c o n s i d e r e d t h e l o a d i n g r a t e s of p h o s p h o r u s and n i t r o g e n and t h e i r r e l a t i o n s h i p t o i t s t r o p h i c s t a t e .

(Weiss and Moore, 1 9 7 5 ) .

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PURPOSE AND OBJECTIVES

A m a j o r i t y of t h e " l a k e s " o f N o r t h C a r o l i n a h a v e b e e n formed by t h e

impounding of r i v e r s a t many s u i t a b l e dam s i t e s i n t h e i r f l o w from t h e w e s t e r n m o u n t a i n s t h r o u g h t h e Piedmont t o t h e C o a s t a l P l a i n . I n many i n s t a n c e s t h e s e r i v e r s and t h e i r impoundments r e c e i v e s u b s t a n t i a l q u a n t i t i e s of w a s t e w a t e r d i s c h a r g e s f r o m m a j o r u r b a n a r e a s . I t i s c u r r e n t l y deemed e s s e n t i a l t h a t t h e e f f e c t of t h e s e d i s c h a r g e s b e q u a n t i f i e d i n t e r m s o f t h e i r n e t e f f e c t on t h e t r o p h i c c o n d i t i o n of t h e impounded w a t e r s i n o r d e r t o e s t a b l i s h t h e e f f e c t i v e - n e s s of p o l l u t i o n a b a t e m e n t e f f o r t s c u r r e n t l y p r o s c r i b e d by w a t e r q u a l i t y management laws. T h i s b a s e l i n e datum o f w a t e r q u a l i t y f o r t h e m a j o r i n l a n d b o d i e s o f w a t e r i n N o r t h C a r o l i n a w i l l p r o v i d e a r e f e r e n c e p o i n t f o r f u t u r e a s s e s s m e n t a s p o l l u t i o n a b a t e m e n t e f f o r t s a r e c a r r i e d f o r w a r d .

The c o n t e m p o r a r y t r o p h i c s t a t e o f N o r t h C a r o l i n a w a t e r s

i s

o f p a r t i c u l a r s i g n i f i c a n c e s i n c e t h e i r c o n d i t i o n may n o t a l w a y s r e f l e c t t h e m a g n i t u d e of t h e n u t r i e n t l o a d s t h a t t h e y a r e c u r r e n t l y r e c e i v i n g . The p a s t s e v e r a l d e c a d e s h a v e s e e n i n t h i s r e g i o n n o t o n l y s i g n i f i c a n t i n c r e a s e s i n a v e r a g e w a t e r u s e w i t h p a r a l l e l i n c r e a s e i n w a s t e w a t e r d i s c h a r g e s b u t a l s o t h e e x p a n s i o n of

u r b a n complexes a n d e x t e n s i o n o f s e w e r l i n e s t o s e r v e l a r g e r p o p u l a t i o n s . But i t i s a l s o a p p a r e n t t h a t t h e r e a r e few i f any l a k e s o r impoundments i n N o r t h C a r o l i n a t h a t h a v e r e a c h e d t h e l e v e l o f n u t r i e n t e n r i c h m e n t t h a t c a n b e c o n s i d e r e d u n d e s i r a b l e i n t e r m s o f t h e i r c u r r e n t w a t e r u s e s . T h i s p r e s e n t i n v e s t i g a t i o n has c a r r i e d o u t a s a m p l i n g program i n t e g r a t e d w i t h o t h e r r e c e n t o b s e r v a t i o n s t o d e s c r i b e c u r r e n t w a t e r q u a l i t y l e v e l s and t o d e f i n e t h e t r o p h i c s t a t e of N o r t h C a r o l i n a l a k e s and impoundments. T h i s s t u d y w i l l a l s o a s s i s t i n e s t a b l i s h i n g t h e l o c a l r e l a t i o n s h i p between n u t r i e n t l e v e l s and e x i s t i n g b i o l o g i c a l r e s p o n s e s , p a r t i c u l a r l y t h e numbers and d i m e n s i o n s of a l g a l

a c t i v i t y and t o p u t i n t o p e r s p e c t i v e t h e c u r r e n t w a t e r q u a l i t y l e v e l s , c u r r e n t w a t e r u s e s , and t h e c u r r e n t n e e d s f o r w a t e r q u a l i t y improvement.

C u r r e n t I n v e s t i g a t i o n s

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t h a t a r e v i e w of t h e l a k e s y s t e m of N o r t h C a r o l i n a s h o u l d b e c a r r i e d o u t t o p r o v i d e a b a s e l i n e d e s c r i b i n g c o n t e m p o r a r y q u a l i t y . The d e s i g n of t h e p r e s e n t i n v e s t i g a t i o n was t o i n s u r e a r e g i o n a l p r e s e n t a t i o n i n t h e t h r e e p r i n c i p a l p h y s i o g r a p h i c p r o v i n c e s o f N o r t h C a r o l i n a , t h e C o a s t a l P l a i n , P i e d m o n t , and Mountain. I n a d d i t i o n i t h a s b e e n p o s s i b l e t o i d e n t i f y a s e r i e s of small m i l l ponds whose o r i g i n s d a t e b a c k , i n one o r two i n s t a n c e s , t o t h e 1 8 t h C e n t u r y . These h a v e b e e n i n c l u d e d i n t h i s s t u d y i n o r d e r t o p l a c e i n p e r s p e c t i v e t h e c o n t e m p o r a r y t r o p h i c s t a t e s of r e c e n t impoundments i n

c o m p a r i s o n t o t h o s e which h a v e b e e n exposed f o r l e n g t h y p e r i o d s t o b o t h t h e i m p a c t s o f man's c u l t u r a l a c t i v i t i e s a s w e l l a s t h e n a t u r a l a g i n g p r o c e s s o f s u r f a c e w a t e r s .

The l a k e s of N o r t h C a r o l i n a sampled i n t h i s s t u d y a r e shown f o r p u r p o s e s of l o c a t i o n a n d i d e n t i f i c a t i o n on a c o u n t y map of t h e s t a t e ( F i g u r e 1 ) . The map code i s i d e n t i f i e d on T a b l e 1, which a l s o l i s t s t h e l a k e s , t h e i r p a r t i c u l a r

o r i g i n o r u s e , l o c a t i o n by c o u n t y , s u r f a c e a r e a and mean d e p t h w h e r e s u c h i n f o r m a t i o n was a v a i l a b l e . The s e l e c t i o n of l a k e s t o p r o v i d e a c r o s s s e c t i o n o f w a t e r c h a r a c t e r i s t i c s was made t o i n c l u d e impoundments i n t h e t h r e e

p h y s i o g r a p h i c p r o v i n c e s , impoundments w i t h i n s e v e r a l d r a i n a g e b a s i n s , and t h e c o m p a r a t i v e l y few n a t u r a l l a k e s m o s t l y i d e n t i f i e d w i t h t h e C o a s t a l P l a i n . The impoundments, due t o t h e i r n a t u r e of o p e r a t i o n , e . g . , hydropower, f l o o d c o n t r o l , o r w a t e r s u p p l y , a r e d e s i g n e d w i t h d i f f e r e n c e s i n f l o w - t h r o u g h r a t e s o r r e t e n t i o n t i m e , a n i m p o r t a n t v a r i a b l e i n e s t a b l i s h i n g t h e i m p a c t of

n u t r i e n t l o a d i n g on t h e body o f w a t e r .

PROCEDURES

Sampling

To i n s u r e d e f i n i t i o n s of t h e t r o p h i c s t a t e n o t e x c e s s i v e l y b i a s e d by anomalous s a m p l e s , a s a m p l i n g f r e q u e n c y was f o l l o w e d t h a t a t t e m p t e d t o

i d e n t i f y p e r i o d s of maximum p h y t o p l a n k t o n growth a s w e l l a s p e r i o d s t h a t d e s c r i b e d maximum l e v e l s of n u t r i e n t c o n c e n t r a t i o n . Monthly s a m p l i n g i s g e n e r a l l y a d e q u a t e t o d e f i n e t h e growing s e a s o n a t t h e s e l a t i t u d e s . However, w h e r e i t was n o t p r a c t i c a l t o s a m p l e f o r 1 2 c o n s e c u t i v e months, a t w i c e y e a r l y s a m p l i n g , a t s p r i n g o r l a t e w i n t e r o v e r t u r n and a g a i n a t midsummer was f o l l o w e d . The f o r m e r c h a r a c t e r i z e d w a t e r q u a l i t y o f n o n - s t r a t i f i e d

(22)

SEE TABLE ( I ) FOR LAKE IDENTIFICATION CODE

(23)

T a b l e 1

S u r f a c e Waters o f N o r t h C a r o l i n a and Immediate A d j a c e n t Areas Sampled f o r T r o p h i c S t a t e A n a l y s i s

1971-1975

S u r f a c e Type and Name

N a t u r a l Lakes B l a c k

J o n e s

Mat tamus k e e t P h e l p s

S a l t e r s S i n g l e t a r y Waccamaw White

Impoundments C o o l i n g Water Belews

Hy co

Codes Area Mean L o c a t i o n

Map

Computer A c r e s Depth-Ft. P r i n c i p a l County

1 BL 1 , 4 2 0

-

Bladen

2 J O 225

-

B l a d e n

3 MA 30,000

-

Hyde

4 PH 1 6 , 0 0 0

-

Washington

5

S A 315

-

_{B l a d e n}

6 SL 570

-

B l a d e n

7 W A 8 , 9 4 0 4 . 9 Columbus

8 WH 1 , 0 7 0

-

Bladen

Water S u p p l y

U n i v e r s i t y 11 UN

M i c h i e 12 MC

High P o i n t 4 6 HP

Wheeler 4 7 WE

Brand t

4

8 BR

B u r l i n g t o n 4 9 BU L e x i n g t o n - T h o m a s v i l l e 50 LT

Towns end 5 1 TO

H y d r o e l e c t r i c and F l o o d Control Roanoke R i v e r

J o h n H. Kerr 2 8

KR

G a s t o n 2 9 G A

Roanoke R a p i d s 30 RR Yadkin R i v e r

W. K e r r S c o t t 2 2 KS

High Rock 2 3 HR

T u c k e r t o n 2 4 TU

Badin 2 5 B A

T i l l e r y 2 6 TL

( e l e v . 300) 22,000 1 8 . 8

4 , 9 0 0 1 5 . 8

B l e w e t t F a l l s 2 7 BW 2 , 5 0 0 3 6 . 0

S t o k e s , Rockingham P e r s o n

Orange Durham G u i l f o r d Wake

G u i l f o r d A1 aman c e Davidson G u i l f o r d

Mecklenberg, Va. Vance, N . C .

Warren H a l i f a x

Wilkes

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T a b l e 1 ( c o n t i n u e d )

S u r f a c e

Codes Area Mean L o c a t i o n

Type and Name Map Computer A c r e s Depth-Ft. P r i n c i p a l County Catawba R i v e r

James 1 3

Rhodhiss 1 4

Hickory 1 5

Lookout S h o a l s 1 6

Norman 1 7

M t . I s l a n d 1 8 Wylie (N.C.-S.C.) 1 9 F i s h i n g Creek (S

.

C

.

) 20 W a t e r e e (S. C . ) 2 1 Broad R i v e r

L u r e

McDowell, Burke C a l d w e l l , Burke A l e x a n d e r , Catawba I r e d e l l , Catawba Catawba, I r e d e l l , L i n c o l n , Mecklenberg M e c k l e n b e r g , G a s t o n M e c k l e n b e r g , Gaston,N.C York, S.C.

C h e s t e r , L a n c a s t e r , S . C . F a i r f i e l d , Kershaw,S.C.

Green R i v e r

Ad g e r 6 2 AD 440 26.7 P o l k

Summit 60 SM 325 40.7 Henderson

Toxaway R i v e r

5 9 TX 650

-

Toxaway T r a n s y l v a n i a

H i w a s s e e R i v e r

Chatuge 56 C T 7,150 3 4 . 5 Clay

Hiwassee 5 5 HW 6 , 2 8 0 6 9 . 7 Cherokee

N a n t a h a l a R i v e r

N a n t a h a l a 5 4 NA 1 , 6 0 5 8 6 . 4 C l a y , Macon Cheoah R i v e r

S a n t e e t l a h 5 3 S N 2,860 5 5 . 2 Graham L i t t l e T e n n e s s e e R i v e r

F o n t a n a 5 2 FO 1 0 , 6 7 0 1 3 5 . 4 Graham, Swaim

H i g h l a n d 5 7 HL 400 e s t . Macon

T u c k a s e i g e e R i v e r

Thorpe 5 8 TH 1 , 4 6 2 48.4 J a c k s o n

R i v e r Segment

44 CH

-

Chowan H e r t f o r d , G a t e s ,

(U.S. 1 3 t o Chowan, B e r t i e

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Table 1 ( c o n t i n u e d )

S u r f a c e

Codes Area Mean L o c a t i o n Type and Name

Map

Computer Acres Depth-Ft. P r i n c i p a l County Old M i l l Ponds ( y e a r c o n s t r u c t e d )

C r y s t a l (1885) 3 1 CL Davies (1850) 3 2 DM F i n c h e s (1875) 33 FH Hodgins (1871) 34 HO Jackson (1885) 35 J K Johns (1840) 36 J H J o n e s (1810) 3 7 J P Lytches (1870) 3 8 LY McKensie (1860) 3 9 MK McNeils (1870) 4 0 MN Monroe (1825) 41 MO Orton (1810) 4 2 OR T u l l (1875) 4 3

TM

S i l v e r (1785) 45 S I

(26)

p e r i o d o f maximum i l l u m i n a t i o n and t e m p e r a t u r e . These d i d n o t n e c e s s a r i l y c o i n c i d e w i t h t h e g r e a t e s t r a n g e of t r o p h i c c o n d i t i o n s . The d a t a c o l l e c t e d on s p e c i f i c s a m p l i n g d a t e s o r a v e r a g e s o f c l o s e l y r e l a t e d d a t e s h a v e b e e n assembled f o r e a c h l a k e i n Appendix A.

T r o p h i c and Q u a l i t y P a r a m e t e r s

I n t h e d e f i n i t i o n of t r o p h i c s t a t e t h e t a s k becomes o n e o f q u a n t i f y i n g t h e m a g n i t u d e of t h e b i o m a s s s u p p o r t e d by t h e n u t r i e n t f l u x . G e n e r a l l y t h i s measurement i s made

a t

t h e p r i m a r y l e v e l e i t h e r by e n u m e r a t i o n of t h e c e l l

d e n s i t y of t h e p l a n k t o n i c a l g a e a n d / o r c e l l volume. S i n c e t h i s d e t e r m i n a t i o n i s i n f l u e n c e d by t h e s a m p l i n g p r o c e d u r e s and q u a n t i f y i n g t e c h n i q u e s i t d o e s n o t n e c e s s a r i l y d e s c r i b e t h e n e t i n t e g r a t e d e f f e c t o f p r i m a r y p r o d u c t i v i t y . O t h e r measures h a v e a l s o b e e n used t o a r r i v e a t a n a s s e s s m e n t of t r o p h i c s t a t e s u c h a s r a t e o f c a r b o n f i x a t i o n ( p r i m a r y p r o d u c t i v i t y ) ; t h e m a j o r components of t h e n u t r i e n t f l u x , n i t r o g e n , p h o s p h o r u s and c a r b o n ; o r t h e r e l a t i v e

t r a n s p a r e n c y of t h e w a t e r ( S e c c h i d i s k d e p t h ) u n d e r t h e a s s u m p t i o n t h a t t h e d e g r e e o f t u r b i d i t y i s a d i r e c t i n d i c a t i o n o f t h e p a r t i c u l a t e m a t e r i a l o f b i o l o g i c a l o r i g i n o b s c u r i n g t h e p a s s a g e of l i g h t .

L i s t e d below a r e d e f i n i t i o n s o r d e s c r i p t i o n s o f t h e measured o r

c a l c u l a t e d w a t e r q u a l i t y p a r a m e t e r s u s e d i n a r r i v i n g a t a s t a t e m e n t o f t r o p h i c c o n d i t i o n f o r t h e more t h a n 60 b o d i e s o f w a t e r sampled. Each w a t e r s a m p l e was c o n s i d e r e d a microcosm, c o n s t i t u t i n g t h e p h y s i c a l and c h e m i c a l e n v i r o n m e n t o f a s p e c i f i c m i c r o f l o r a ( p l a n k t o n i c a l g a e ) . U l t i m a t e l y a set of

854

o b s e r v a t i o n s from a l l b o d i e s of w a t e r w e r e t r e a t e d a s a d a t a p o o l f o r s t a t i s t i c a l a n a l y s i s o f t h e s u r f a c e w a t e r s o f N o r t h C a r o l i n a . The h e a d i n g a b b r e v i a t i o n s a r e t h o s e used i n s u b s e q u e n t t a b l e s o f t h i s r e p o r t .

Temp."C: The t e m p e r a t u r e of t h e w a t e r s a m p l e measured i n d e g r e e s C e l s i u s was u s u a l l y o b t a i n e d w i t h a t h e r m i s t e r p r o b e . A s r e p o r t e d i t i s e i t h e r

r e p r e s e n t a t i v e o f t h e a v e r a g e v a l u e o f t h e e p i l i m n i o n a t t h e t i m e of s a m p l i n g o r t h e s p e c i f i c t e m p e r a t u r e a t t h e d e p t h t h a t a s a m p l e was t a k e n f o r a l g a l a n a l y s i s .

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The S e c c h i d e p t h was g e n e r a l l y e s t i m a t e d t o t h e n e a r e s t h a l f f o o t .

Secchi-M: S e c c h i d e p t h i n m e t e r s a s c a l c u l a t e d f r o m t h e f i e l d measurement o r i n t h e l a t e r s t a g e s o f t h e f i e l d work measured i n t h e f i e l d t o t h e n e a r e s t 0 . 1 M.

NH3-N: Ammonia n i t r o g e n , d e t e r m i n e d by t h e a u t o m a t e d p h e n o l a t e method (U.S. EPA, 1974) on a T e c h n i c o n A u t o a n a l y z e r . The w a t e r s a m p l e was p r e t r e a t e d by

f i l t e r i n g t h r o u g h a washed M i l l i p o r e H A f i l t e r .

N03NOq-N: N i t r i t e a n d n i t r a t e n i t r o g e n , d e t e r m i n e d by r e d u c t i o n w i t h h y d r a z i n e s u l p h a t e (U.S. EPA, 1 9 7 4 ) . The p r o c e d u r e was c a r r i e d o u t on a s a m p l e p r e t r e a t e d by f i l t r a t i o n t h r o u g h a washed M i l l i p o r e HA f i l t e r . The a n a l y s i s was made o n a

T e c h n i c o n A u t o a n a l y z e r w i t h t h e c o l o r b e i n g measured a t 520 m u .

K j e l - N : K j e l d a h l n i t r o g e n a s d e t e r m i n e d on a T e c h n i c o n A u t o a n a l y z e r u s i n g t h e a u t o m a t e d p h e n o l a t e method on a n u n f i l t e r e d s a m p l e . The s a m p l e was d i g e s t e d i n a c o n t i n u o u s d i g e s t o r w i t h s u l f u r i c a c i d c o n t a i n i n g p o t a s s i u m s u l f a t e and m e r c u r i c s u l f a t e a s a c a t a l y s t .

Inorg-N: I n o r g a n i c n i t r o g e n , r e p r e s e n t i n g t h e sum o f NH3-N and N02N03-N i n t h e s a m p l e .

Org-N: O r g a n i c n i t r o g e n , r e p r e s e n t i n g t h e d i f f e r e n c e between K j e l - N and NH3-N and t h u s d e f i n i n g t h e n i t r o g e n i n c l u d i n g 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 n i t r o g e n .

Total-N: The sum of NO2N03-N and Kjel-N.

POL-P: O r t h o p h o s p h a t e p h o s p h o r u s , d e t e r m i n e d on a s a m p l e f i l t e r e d t h r o u g h a washed M i l l i p o r e HA f i l t e r u s i n g t h e a u t o m a t e d s t a n n o u s c h l o r i d e

(U.S.

EPA, 1974) method o n a T e c h n i c o n A u t o a n a l y z e r .

T o t a l Sol-P: T o t a l s o l u b l e p h o s p h o r u s o r d i s s o l v e d p h o s p h o r u s a s d e t e r m i n e d on a s a m p l e a f t e r f i l t r a t i o n t h r o u g h a washed M i l l i p o r e HA f i l t e r . The d i s s o l v e d o r s o l u b l e f r a c t i o n i s a u t o c l a v e d w i t h p o t a s s i u m p e r s u l f a t e and

s u l f u r i c a c i d f o l l o w e d by t h e a u t o m a t e d s t a n n o u s c h l o r i d e method f o r d e t e r m i n a - t i o n o f t h e r e a c t i v e p h o s p h o r u s .

P a r t i c u l a t e - P : The p h o s p h o r u s component a s s o c i a t e d w i t h p a r t i c u l a t e m a t e r i a l s and d e t e r m i n e d by d i f f e r e n c e between t h e T o t a l - P and T o t a l Sol-P.

T o t a l - P : The t o t a l p h o s p h o r u s component d e t e r m i n e d on a n u n f i l t e r e d w a t e r s a m p l e a u t o c l a v e d w i t h p o t a s s i u m p e r s u l f a t e and s u l f u r i c a c i d t o c o n v e r t v a r i o u s forms of p h o s p h o r u s t o t h e o r t h o p h o s p h a t e w i t h f i n a l d e t e r m i n a t i o n a s P04-P u s i n g t h e a u t o m a t e d s t a n n o u s c h l o r i d e method.

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Inorg-N/Sol P: The r a t i o o f i n o r g a n i c n i t r o g e n t o t o t a l s o l u b l e p h o s p h o r u s , Alk: T o t a l a l k a l i n i t y as&1CaC03 a n d d e t e r m i n e d

on

a 1 0 0 m l w a t e r s a m p l e

-

t i t r a t e d w i t h .02N H C 1 . The e q u i v a l e n c e p o i n t of pH 5 . 1 i s d e t e r m i n e d . Cond umhos: C o n d u c t i v i t y i n micromhos p e r c e n t i m e t e r a t 25OC d e t e r m i n e d

e i t h e r on a w a t e r s a m p l e r e t u r n e d t o t h e l a b o r a t o r y u t i l i z i n g a Lab-Line E l e c t r o MKO meter o r i n t h e f i e l d w i t h a Y S I Model 33 f i e l d t e m p e r a t u r e / s a l i n i t y /

c o n d u c t i v i t y m e t e r .

T u r b i d i t y : Determined on Hach Model 2100 t u r b i d i m e t e r c a l i b r a t e d a g a i n s t a Formazin s t a n d a r d and r e p o r t e d as J a c k s o n t u r b i d i t y u n i t s (JTU).

C o l o r : Determined on a raw w a t e r sample by c o m p a r i s o n w i t h p o t a s s i u m c h l o r o p l a t i n a t e s t a n d a r d s .

L i g h t p e n e t r a t i o n : The d e p t h o f l i g h t p e n e t r a t i o n d e t e r m i n e d by u n d e r w a t e r p h o t o m e t r y u s i n g a s e l e n i u m c e l l p h o t o m e t e r .

&I:G e n e r a l l y d e t e r m i n e d i n t h e f i e l d u s i n g a p o r t a b l e g l a s s e l e c t r o d e f i e l d

pH m e t e r .

D i s s o l v e d Oxygen: Y S I , Weston and S t a c k , o r Hydro Lab d i s s o l v e d oxygen p r o b e s

--

c a l i b r a t e d by IJink1e.r t i t r a t i o n . V a l u e s r e p o r t e d g e n e r a l l y r e p r e s e n t a mean o f t h e e p i l i m n i o n o r t h e d e p t h from which t h e b i o l o g i c a l sample was t a k e n . F u l l v e r t i c a l p r o f i l e s w e r e r o u t i n e l y d e t e r m i n e d and a r e r e p o r t e d a t s p e c i f i c d e p t h s

f o r p o i n t s o f d i s c u s s i o n .

Ca, K , Fe, and Mn: These e l e m e n t s w e r e d e t e r m i n e d on a s a m p l e c o n t a i n i n g 1 m l c o n c e n t r a t e d n i t r i c a c i d p e r 100 m l o f w a t e r a n d a s p i r a t e d d i r e c t l y i n t o t h e f l a m e of a P e r k i n Elmer Model 303 a t o m i c a b s o r p t i o n s p e c t r o p h o t o m e t e r u s i n g s p e c i f i c d e t e c t o r lamps. V a l u e s o f C a and Fe a r e p r o b a b l y low due t o

a n a l y t i c a l p r o b l e m s .

B i o l o g i c a l P a r a m e t e r s

C h l o r a : C h l o r o p h y l l

-

a was d e t e r m i n e d on a w a t e r s a m p l e f i l t e r e d o n t o a G e l m a n g l a s s t i b e r f i l t e r and a c e t o n e e x t r a c t e d u s i n g t h e t e c h n i q u e s of S t r i c k l a n d and P a r s o n s (1972) and t h e p h e o p h y t i n c o r r e c t i o n e q u a t i o n s o f L o r e n z e n ( 1 9 6 7 ) . Absorbance o f t h e a c e t o n e e x t r a c t was d e t e r m i n e d a t w a v e l e n g t h s o f 665 mp a n d 700 mp ( t u r b i d i t y c o r r e c t i o n ) u s i n g a Beckman DB s p e c t r o p h o t o m e t e r a n d

4

cm a b s o r p t i o n c e l l s .

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e x c i t a t i o n w i t h u l t r a v i o l e t l i g h t u s i n g a T u r n e r model 110 f l u o r o m e t e r e q u i p p e d w i t h a Mamamatsu R136 p h o t o m u l t i p l i e r , a h i g h s e n s i t i v i t y s a m p l e h o l d e r , b l u e lamp, C o r n i n g 5-60 p r i m a r y f i l t e r and 2-64 s e c o n d a r y f i l t e r . Water s a m p l e s w e r e r e a d d i r e c t l y on t h e f l u o r o m e t e r and r e s u l t s c o n v e r t e d

t o t h e i n s t r u m e n t s l o x s c a l e . The T u r n e r c h l o r o p h y l l v a l u e s are s i g n i f i c a n t l y c o r r e l a t e d w i t h c h l o r o p h y l l

-

a a s d e t e r m i n e d by s t a n d a r d p r o c e d u r e s . A

c o n v e r s i o n o f T u r n e r U n i t s t o c h l o r o p h y l l

5 mg/m3

c a n b e a p p r o x i m a t e d by m u l t i - p l y i n g by a f a c t o r o f .38 i n t h e r a n g e o f 0-100 and

.46

from 100-250 TU.

P r o d

mg

c/m3khr : The p r o d u c t i v i t y o f t h e w a t e r s a m p l e , r e p o r t e d i n m i l l i g r a m s c a r b o n f i x e d p e r m e t e r 3 p e r h o u r , was d e t e r m i n e d on raw s a m p l e s b r o u g h t b a c k t o t h e l a b o r a t o r y , s t o r e d o v e r n i g h t i n t h e d a r k a t room t e m p e r a t u r e and

i n c u b a t e d i n l i g h t / d a r k b o t t l e s u n d e r 400 f t . c a n d l e s o f f l u o r e s c e n t " d a y l i g h t lamps" a t 24OC. Changes i n d i s s o l v e d oxygen o v e r a s i x h o u r i n c u b a t i o n

p e r i o d w e r e d e t e r m i n e d by W i n k l e r t i t r a t i o n a n d c o n v e r t e d t o c a r b o n e q u i v a l e n c e u s i n g a p h o t o s y n t h e t i c q u o t i e n t of 1 . 2 . The s a m p l e s i n c u b a t e d f o r p r o d u c t i v i t y d e t e r m i n a t i o n w e r e a l i q u o t s o f t h e same w a t e r r e t u r n e d f o r a l g a l c e l l d e n s i t y d e t e r m i n a t i o n s .

C e l l s n o . / m l :

-

The number of c e l l s p e r u n i t volume i s a measure of p h y t o p l a n k t o n p o p u l a t i o n d e n s i t y . A l l c e l l d e n s i t y d e t e r m i n a t i o n s w e r e made on l i v e s a m p l e s , b u t i f n e c e s s a r y h e l d o v e r n i g h t i n a r e f r i g e r a t o r . Measured p o r t i o n s

( n o r m a l l y 1 0 ml) from a w e l l s h a k e n s a m p l e w e r e p l a c e d i n a t a p e r z d c e n t r i f u g e t u b e and c e n t r i f u g e d a t maximum s p e e d i n a c l i n i c a l c e n t r i f u g e f o r 15-20 m i n u t e s . The l i q u i d above e a c h c o n c e n t r a t e d s a m p l e was c a r e f u l l y drawn o f f by p i p e t t e u n t i l a b o u t .05 m l w e r e l e f t . The c o n c e n t r a t e d m a t e r i a l was r e s u s p e n d e d and t h o r o u g h l y mixed i n t h e r e m a i n i n g w a t e r . T h e s e d r o p s w e r e t r a n s f e r r e d by p i p e t t e t o a c l e a n m i c r o s c o p e s l i d e f i l l i n g t h e a r e a u n d e r a 22 x 22 mm c o v e r g l a s s . The c o v e r g l a s s was s e a l e d w i t h a p a r a f f i n - p e t r o l e u m j e l l y m i x t u r e t o p r e v e n t r a p i d d r y i n g . The l i v e p r e p a r a t i o n was examined u n d e r a Z e i s s GFL

compound m i c r o s c o p e t o d e t e r m i n e t h e u n i f o r m i t y of c e l l d i s t r i b u t i o n and

a b s e n c e o f a i r b u b b l e s . The p r e p a r a t i o n was t h e n examined a t 500X t o i d e n t i f y and e n u m e r a t e p h y t o p l a n k t o n i n s e l e c t e d t r a n s e c t s o f known w i d t h and l e n g t h u s i n g a n o i l immersion l e n s a t 1250X f o r c a r e f u l i d e n t i f i c a t i o n and measurement o f s m a l l e r s p e c i e s . I n t h e c a s e o f c o l o n i e s and f i l a m e n t s t h e e n t i r e