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Autumnal and over-winter limnology of three small eutrophic lakes with particular reference to experimental… Halsey, Thomas Gordon 1965

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AUTUMNAL AND OVER-WINTER LIMNOLOGY OF THREE SMALL EUTROPHIC LAKES WITH PARTICULAR REFERENCE TO EXPERIMENTAL CIRCULATION AND TROUT MORTALITY by THOMAS GORDON HALSEY B.A., University of B r i t i s h Columbia, 1961 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in the Department of Zoology We accept th i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1965 I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e 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 C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r a g r e e t h a t p e r -m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e Head o f my D e p a r t m e n t o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t , c o p y i n g o r p u b l i -c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n permission„ D e p a r t m e n t o f / ^ r r T ^ y ^ - ($^&U~6 ^/^jC^o^'^i) The U n i v e r s i t y o f B r i t i s h C o l u m b i a , V a n c o u v e r 8, C a n a d a D a t e £( f&u£ ///  i i A B S T R A C T A u t u m n a l a n d o v e r - w i n t e r l i m n o l o g i c a l c o n d i t i o n s i n M a r q u e t t e , C o r b e t t a n d C o u r t n e y L a k e s i n B r i t i s h C o l u m b i a w e r e f o l l o w e d m o n t h l y f r o m a u t u m n , 1 9 6 1 , t o s p r i n g , 1 9 6 4 , a n d s ome a d d i t i o n a l d a t a w e r e c o l l e c t e d i n w i n t e r , 1 9 6 5 . I n d i c e s o f p r o d u c t i v i t y f o r summer a n d w i n t e r c o n d i t i o n s s u g -g e s t t h a t C o u r t n e y L a k e i s m o s t p r o d u c t i v e , M a r q u e t t e L a k e l e a s t p r o d u c t i v e a n d C o r b e t t L a k e i n t e r m e d i a t e . A l t h o u g h o v e r - w i n t e r m o r t a l i t y o f f i s h e s w o u l d be, e x p e c t e d t o o c c u r i n C o u r t n e y L a k e i t h a s n o t b e e n o b s e r v e d t h e r e w h e r e a s i n M a r q u e t t e a n d C o r b e t t L a k e s i t f r e q u e n t l y o c c u r s . M a r q u e t t e a n d C o r b e t t L a k e s w e r e s h a r p l y s t r a t i f i e d i n s ummer b e c a u s e l o c a l t o p o g r a p h y p r o v i d e d p r o t e c t i o n f r o m w i n d a c t i o n w h e r e a s s t r a t i f i c a t i o n i n t h e m o r e e x p o s e d C o u r t n e y L a k e w a s i l l - d e f i n e d . A v e r a g e w i n d v e l o c i t i e s o n C o u r t n e y L a k e w e r e 4.3 t i m e s g r e a t e r a n d m o r e u n i d i r e c t i o n a l t h a n t h o s e o n C o r b e t t L a k e . M a r q u e t t e L a k e w a s s u b j e c t t o w i n d a c t i o n s i m i l a r t o t h a t o f C o r b e t t L a k e . To t e s t t h e h y p o t h e s i s t h a t w i n t e r l i m n o l o g i c a l d i f f e r e n c e s b e t w e e n C o u r t n e y a n d C o r b e t t L a k e s w e r e d u e t o i n s u f f i c i e n t a u t u m n a l c i r c u l a t i o n , C o r b e t t L a k e w a s e x p e r i m e n t a l l y c i r c u l a t e d . A u t u m n a l c i r c u l a t i o n i n C o u r t n e y L a k e w a s c o m p l e t e a n d r e s u l t e d i n o v e r - w i n t e r s u r v i v a l o f S a l m o g a i r d n e r i a n d R i c h a r d s o n i u s b a l t e a t u s . I n c o m p l e t e a u t u m n a l c i r c u l a t i o n a n d o x y g e n a t i o n i n C o r b e t t a n d M a r q u e t t e L a k e s r e s u l t e d i n i i i o v e r - w i n t e r - m o r t a l i t y o f S a l m o g a i r d n e r i a n d S a l v e l i n u s f o n -t i n a l i s . I n o r d e r t o e x p e r i m e n t a l l y e x a m i n e c a u s e s f o r t h e l i m n o l o g i c a l d i f f e r e n c e s b e t w e e n t h e l a k e s , C o r b e t t L a k e w a s a r t i f i c i a l l y c i r c u l a t e d . A c o m p r e s s e d a i r " b u b b l e r s y s t e m " c o m p r i s e d o f a s u b m e r g e d c i r c l e s ( c i r c u m f e r e n c e • = 7 2 6 m) o f p l a s t i c p i p e a n d a n a i r c o m p r e s s o r w a s u s e d t o c i r c u l a t e C o r b e t t L a k e i n t h e a u t u m n o f 1 9 6 2 a n d 1 9 6 3 . T h e r e s u l t s o f t h e e x p e r i m e n t a l c i r c u l a t i o n o f C o r b e t t L a k e c o m p a r e d t o t h e l i m n o l o g i c a l c o n d i t i o n s i n t h e " c o n t r o l " l a k e s , c o n f i r m e d t h e o r i g i n a l h y p o t h e s i s . B e l o w a v e r a g e s n o w f a l l i n 1 9 6 2 - 6 3 r e s u l t e d i n d i -r e c t l y i n a n o m a l o u s d i s s o l v e d o x y g e n v a l u e s ( s u p e r s a t u r -a t i o n ) . C o n s e q u e n t l y t h e e x p e c t e d o v e r - w i n t e r m o r t a l i t i e s o f f i s h e s i n M a r q u e t t e L a k e d i d n o t o c c u r w h e r e a s t h e e x p e c -t e d w i n t e r m o r t a l i t i e s d i d o c c u r i n 1 9 6 1 - 6 2 a n d 1 9 6 3 - 6 4 . W i n t e r l i g h t p e n e t r a t i o n a n d i n t e n s i t y i n C o r b e t t L a k e w a s c o r r e l a t e d w i t h d i f f e r e n c e s i n s n o w f a l l b e t w e e n y e a r s . L i g h t p e n e t r a t i o n a n d i n t e n s i t y d i f f e r e d c o n s i d e r -a b l y b e t w e e n l a k e s w h e n s n o w a n d i c e c o n d i t i o n s w e r e a b o u t e q u a l ( 1 9 6 5 ) b e c a u s e o f d i f f e r e n c e s i n w a t e r q u a l i t y . iv TABLE OF CONTENTS Page INTRODUCTION 1 DESCRIPTION OF THE STUDY AREA 2 BIOLOGICAL CHARACTERISTICS OF THE LAKES 6 METHODS AND MATERIALS 8 GENERAL LIMNOLOGY 8 EXPERIMENTAL CIRCULATION 10 RESULTS 13 COMPARATIVE MORPHOMETRY 13 METEOROLOGY 15 OVER WINTER FISH MORTALITY. 19 PHYSICAL CHARACTERISTICS. . 23 Transparency. . . 23 Temperature 23 (1) Summer Stagnation 27 (2) Autumnal C i r c u l a t i o n . 28 (3) Winter Stagnation 29 (4) Vernal C i r c u l a t i o n . 30 S t a b i l i t y . . 30 CHEMICAL CHARACTERISTICS. . 31 Oxygen. . . . . . . 31 (1) Summer Stagnation 31 (2) Autumnal C i r c u l a t i o n 35 (3) Winter Stagnation 36 (4) Vernal C i r c u l a t i o n 37 Hydrogen Sulfide 37 pH 39 A l k a l i n i t y 39 Total Dissolved Solids 42 Conductivity. 42 INDICES OF PRODUCTIVITY 44 Physical. 44 Chemical 44 V Page EXPERIMENTAL CIRCULATION 47 DISCUSSION 51 RELATIVE PRODUCTIVITY 51 TOPOGRAPHY AND WIND ACTION. 55 SNOW COVER AND WINTER LIMNOLOGY . . . . . . . . 58 WINTER OXYGEN DEMAND 61 EXPERIMENTAL CIRCULATION 63 SUMMARY 68 LITERATURE CITED 70 v i LIST OF TABLES Table Page I. Morphometric parameters of Marquette, Corbett and Court-ney Lakes. 14 II . Monthly snowfall as recorded by the Department of Transport Recording Station near the study area . 20 I I I . Fish mortality (during study period) for Marquette, Corbett and Courtney Lakes 22 IV. Mean Secchi disk readings (m); calculated from data c o l l e c t e d i n a l l seasons except winter . . . . . . . 23 V. Maximum and minimum bicarbonate and carbonate a l k a l i n i t y (mg/1) recorded during the study period (August 28, 1961 - May 24, 1964) . . . . 41 VI. Mean concentration of t o t a l d i s -solved s o l i d s (mg/1). Calculated from data c o l l e c t e d i n August, October and December, 1961 and May, 1962, for Corbett and Court-ney Lakes—June, 1962 for Mar-quette Lake 42 V i l a . Morphometric indices of produc-t i v i t y (ranked) 45 b. Chemical indices of productivity . . . . 45 VIII. Summary of indices of produc-t i v i t y 55 I v i i LIST OF FIGURES F i g u r e Page 1. L o c a t i o n at the study lakes w i t h r e s p e c t to r e l a t i v e p r o x i m i t y of surrounding topography (contours i n meters) 3 2. Hydrographic maps of the study l a k e s showing l o c a t i o n of limnology S t a t i o n I and wind r e c o r d i n g s t a t i o n s (con-tour s i n meters). Limnology S t a t i o n I i s shown f o r Cor b e t t Lake i n F i g . 3. . . . . 4 3. Layout of C o r b e t t Lake experimental c i r c u l a t i o n system and sampling s t a t i o n s . . 11 4. Average v e l o c i t y of wind on immediate lake s u r f a c e (June -November, 1962). The dotted l i n e f o r Marquette Lake rep-r e s e n t s an estimate of average wind v e l o c i t y 16 5. Average wind d i r e c t i o n on the immediate lake s u r f a c e s of Co r b e t t and Courtney Lakes. See t e x t f o r e x p l a n a t i o n of weekly average 18 6. Average t h i c k n e s s of i c e and snow depth f o r each winter of study (3 r e c o r d i n g s 1962 and 1963; 4 r e c o r d i n g s 1964) 21 7. L i g h t i n t e n s i t y and p e n e t r a t i o n through i c e and snow cover (January 30, 1965 and January 31, 1965) 24 8. L i g h t i n t e n s i t y and p e n e t r a t i o n through i c e and snow cover (January 25, 1964 and January 27, 1963) 25 9. Seasonal isotherms (°C) f o r Marquette, C o r b e t t and Courtney Lakes f o r the dur-a t i o n of the study p e r i o d 1961-64. Note d u r a t i o n of i c e cover and p e r i o d s o f a r t i f i c i a l c i r c u l a t i o n . . 26 10. Seasonal d i f f e r e n c e s i n Schmidt's thermal s t a b i l i t y 32 11. D i s s o l v e d oxygen i s o p l e t h s (mg/1) f o r the d u r a t i o n of the study p e r i o d (1961-64) . . . 34 v i i i F i g u r e P a g e 1 2 . H y d r o g e n s u l f i d e ( J a n . 3 0 , 1 9 6 5 ) . v e r t i c a l s e r i e s 3 8 1 3 . V e r t i c a l pH s e r i e s ( 1 9 6 1 a n d 1 9 6 5 ) 4 0 1 4 . Summer a n d w i n t e r v e r t i c a l s p e c i f i c c o n d u c t i v i t y v a l u e s . M e a s u r e m e n t s t a k e n i n s i t u 4 3 1 5 . D a i l y c h a n g e s i n m e a n o x y g e n c o n c e n -t r a t i o n a n d t h e v e r t i c a l e x t e n t o f d i s s o l v e d o x y g e n e f f e c t e d b y t h e e x p e r i m e n t a l c i r c u l a t i o n o f C o r b e t t L a k e , 1 9 6 3 a n d 1 9 6 2 . ( N o t e h o u r s o f e x p e r i m e n t a l c i r c u l a t i o n a n d s u r f a c e w a t e r t e m p e r a t u r e ) 4 8 i x ACKNOWLEDGEMENTS T h i s s t u d y w a s s u p p o r t e d b y t h e B r i t i s h C o l u m b i a F i s h a n d Game B r a n c h a n d t h e I n s t i t u t e o f F i s h e r i e s , U n i -v e r s i t y o f B r i t i s h C o l u m b i a . T h e p r o b l e m w a s s u g g e s t e d b y D r . T.G. N o r t h c o t e w h o s e d i r e c t i o n a n d a d v i c e b o t h d u r i n g t h e i n v e s t i g a t i o n a n d t h e p r e p a r a t i o n o f t h e m a n u s c r i p t , i s h e r e b y g r a t e f u l l y a c k n o w l e d g e d . T h a n k s a r e a l s o d u e t o D r . G. F. H a r t m a n f o r g u i d a n c e d u r i n g t h e p r e p a r a t i o n o f f i g u r e s a n d t e x t . P a r t i c u l a r t h a n k s a r e e x t e n d e d t o M. T e r a g u c h i , C A . G i l l , t h e l a t e G. S h a l e r a n d D.C. S i n c l a i r f o r v a l u a b l e a s s i s t a n c e i n t h e f i e l d . F i e l d a s s i s t a n c e w a s a l s o r e n d e r e d b y M e s s r s . E.R. Z y b l u t , M.W. R e h e i s a n d A. G i l l . T h e a u t h o r i s i n d e b t e d t o M r . D. F i l l i o n a n d D r . N o r t h c o t e ' s g r a d u a t e l i m n o l o g y c l a s s o f 1 9 6 5 - 6 6 f o r C ^ d a t a . M a n u s c r i p t p r e p -a r a t i o n h a s b e e n g r e a t l y f a c i l i t a t e d b y t h e h e l p f u l a s s i s t -a n c e o f M i s s M. A n d r u n y k . T h e a c c o m m o d a t i o n s u p p l i e d b y t h e l a t e M r . G i b S h a l e r a n d M r s . E v e S h a l e r w a s m o s t a p p r e c i a t e d . T h e c r i t i c a l r e a d i n g o f t h e m a n u s c r i p t b y D r . H. D. F i s h e r , D r . C C . L i n d s e y a n d D r . N . J . W i l i m o v s k y h a s b e e n o f g r e a t a s s i s t a n c e . A b o v e a l l t h e a u t h o r i s h u m b l y g r a t e f u l f o r t h e c e a s e l e s s s u p p o r t a n d e n c o u r a g e m e n t f r o m h i s w i f e , P h y l l i s H a l s e y . 1 INTRODUCTION Over-winter mortality of fishes most often occurs in shallow eutrophic lakes that have three to four months of ice and snow cover (Greenbank, 1945; Welch, 1952; Hutchinson, 1957; Reid, 1961). This phenomenon is attributed mainly to oxidative demands of high productivity which results in severe oxygen depletion during the period that the ice cover effectively seals off the lake from atmospheric oxygen. Most eutrophic lakes are completely circulated in the autumn and are fully or nearly saturated with dissolved oxygen prior to ice formation. The typical pattern wherein high productivity causes a severe reduction of an ample autumn oxygen supply i s not applicable to at least two lakes, Marquette and Corbett, in the southwest interior of British Columbia. In Corbett Lake, over-winter mortality of fishes occurred six out of ten recorded years and in Marquette Lake, two out of three recorded years. Courtney Lake, a shallower nearby lake, has no recorded cases of over-winter fish mortalities. In the autumn of 1961 studies were started to investigate the differences between Corbett and Courtney Lakes with respect to general autumn and winter limnology. In 1962 data from an ancillary investigation showed the value of Marquette Lake as an additional comparison. Data collec-ted in 1961 and 1962 indicated that the principal reason for 2 d i f f e r e n t limnological conditions was due to incomplete autumnal c i r c u l a t i o n . To test the hypothesis that differences between the lakes were due to lack of autumnal c i r c u l a t i o n i n Mar-quette and Corbett Lakes, an experimental c i r c u l a t i o n of Corbett Lake was conducted f i r s t i n the autumn of 1962 and was repeated i n the f a l l of 1963. DESCRIPTION OF THE STUDY AREA Marquette, Corbett and Courtney Lakes are situated between lat i t u d e 50° and 53° N and longitude 120° 39' 45" W and 120° 35' 20" W. The topography of the area surrounding the study lakes affords varying degrees of protection from wind action (Fig. 1). Marquette and Corbett Lakes (elevation 1036 metres) are closely surrounded by protective h i l l s whereas Courtney Lake (elevation 975 metres) i s more exposed to wind action. The orientation of the lake basins and the detailed hydrography are shown i n Fig. 2. Generally considered, the southwest i n t e r i o r of B r i t i s h Columbia has a mild, continental climate. Winters are cold and snow i s present for most of December and Janu-ary. Most of the annual p r e c i p i t a t i o n i s snow in December, January and February. Summer i s generally bright and cloud-3 F i g . 1. L o c a t i o n o f t h e s t u d y l a k e s w i t h r e s p e c t t o r e l a t i v e p r o x i m i t y o f s u r r o u n d i n g t o p o g r a p h y ( c o n t o u r s i n m e t e r s ) . 4a F i g . 2. H y d r o g r a p h i c maps o f t h e s t u d y l a k e s s h o w i n g l o c a t i o n o f l i m n o l o g y S t a t i o n I and w i n d r e c o r d i n g s t a t i o n s ( c o n t o u r s i n m e t e r s ) . L i m n o l o g y S t a t i o n I i s shown f o r C o r b e t t L a k e i n F i g . 3. 4 M A R Q U E T T E L A K E 5 l e s s i n c o n t r a s t w i t h c l o u d y w i n t e r s . T h e u p l a n d s a r e c o o l i n s u m m e r , c o l d i n w i n t e r a n d h a v e m o r e p r e c i p i t a t i o n t h a n t h e v a l l e y s . "Air m o v e m e n t s a t t h e s t a t i o n s w i t h r e c o r d s d i f f e r s o m u c h t h a t l i t t l e g e n e r a l i z a t i o n i s p o s s i b l e . I n t h e v a l l e y s t h e w i n d a l m o s t a l w a y s b l o w s a l o n g t h e v a l l e y , t h a t i s i n m o s t c a s e s f r o m n o r t h o r s o u t h . " ( K e n d r e w a n d K e r r , 1 9 5 5 ) . T h e n e a r e s t o f f i c i a l m e t e o r o l o g i c a l o b s e r v a t i o n s t a t i o n , P r i n c e t o n , a b o u t 6 2 . 5 km s o u t h o f t h e s t u d y a r e a i s s u b j e c t t o l o c a l v a r i a t i o n i n w i n d d i r e c t i o n a n d v e l o c i t y b e c a u s e o f l o c a l t o p o g r a p h y . C o n s e q u e n t l y , t h e w i n d d i r e c -t i o n a n d / o r v e l o c i t y a t P r i n c e t o n i s p r o b a b l y n o t i n d i c a t i v e o f m e t e o r o l o g i c a l e v e n t s a t t h e i m m e d i a t e s t u d y a r e a . W i n d d i r e c t i o n a n d v e l o c i t y w a s m e a s u r e d f o r C o r b e t t a n d C o u r t n e y L a k e s . F r e q u e n t v i s u a l o b s e r v a t i o n s o f w i n d o n M a r q u e t t e L a k e i n d i c a t e d a m a r k e d s i m i l a r i t y t o t h e r e c o r d s f o r C o r -b e t t L a k e b u t M a r q u e t t e L a k e i s p r o b a b l y s u b j e c t t o e v e n l e s s w i n d a c t i o n . T h e m e a n a n n u a l s n o w f a l l f o r t h e s o u t h w e s t i n t e r -i o r o f B r i t i s h C o l u m b i a i s 1 0 1 . 6 cm ( K e n d r e w a n d K e r r , 1 9 5 5 ) . A m a r k e d d i f f e r e n c e i n s n o w f a l l b e t w e e n y e a r s , w i t h i n t h e s t u d y p e r i o d w a s r e c o r d e d . 6 B I O L O G I C A L C H A R A C T E R I S T I C S OF THE L A K E S P h y t o p l a n k t o n s a m p l e s t a k e n i n M a y , 1 9 5 2 , s h o w r e p r e s e n t a t i v e s o f C h r y s o p h y t a , P y r r o p h y t a , a n d C y a n o p h y t a ( M a r c h , 1 9 6 3 ) i n M a r q u e t t e L a k e , w h e r e a s C o r b e t t L a k e h a s r e p r e s e n t a t i v e s o f C h l o r o p h y t a a n d C h r y s o p h y t a . C o u r t n e y L a k e h a s r e p r e s e n t a t i v e s o f C h l o r o p h y t a , C h r y s o p h y t a , P y r r o p h y t a a n d C y a n o p h y t a . No m a r k e d b l o o m s o f p h y t o p l a n k -t o n w e r e o b s e r v e d i n t h e s t u d y l a k e s d u r i n g s p r i n g , summer o r a u t u m n . Common z o o p l a n k t o n o f M a r q u e t t e L a k e i n c l u d e t h e C l a d o c e r a n s D a p h n i a a n d B o s m i n a a n d a m p h i p o d s H y a l e l l a a n d G a m m e r u s . C y c l o p o i d a n d C a l a n o i d c o p e p o d s a n d r o t i f e r s a r e a l s o r e c o r d e d . C o m m o n l y o c c u r r i n g z o o p l a n k t o n o f C o r b e t t L a k e a r e n o t e d b y T e r a g u c h i ( 1 9 6 4 ) a s D a p h n i a p u l e x a n d D a p h n i a r o s e a ( d o m i n a n t C l a d o c e r a n s ) . T h e common c o p e p o d i s D i a p t o m u s l e p t o p u s w h e r e a s D i a p t o m u s n u d u s a n d D i a p t o m u s  s i c i l u s o c c u r r a r e l y . T h e m o s t common s p e c i e s o f C h a o b o r u s l a r v a i s C. f l a v i c a n s . C. n y b l a e i a n d C. a m e r i c a n u s a l s o o c c u r . R o t i f e r s a r e e v i d e n t i n p l a n k t o n s a m p l e s a s w e l l . C l a d o c e r a n s , a m p h i p o d s , c o p e p o d s a n d r o t i f e r s a r e r e c o r d e d f o r C o u r t n e y L a k e p l a n k t o n . T h e l i t t o r a l z o n e o f M a r q u e t t e L a k e , l i k e t h a t o f C o r b e t t a n d C o u r t n e y i s c h a r a c t e r i z e d b y t h i c k m a t s o f C h a r a . P l a n o r b i s , P h y s a , T r i c h o p t e r a n l a r v a e a n d n u m e r o u s H y a l e l l a a n d G a m m a r u s a r e f o u n d i n t h e l i t t o r a l r e g i o n . T h e 7 l i t t o r a l z o n e o f C o r b e t t L a k e h a r b o u r s c o m p a r a t i v e l y l a r g e n u m b e r s o f a q u a t i c i n s e c t s a n d G y r a u l u s , a p u l m o n a t e s n a i l o f t h e f a m i l y P l a n o r b i d a e ( H u m p h r e y s , 1 9 6 4 ) . H u m p h r e y s ( 1 9 6 4 ) a l s o f o u n d a b u n d a n t H y a l e l l a a z t e c a a n d c h i r o n o m i d l a r v a e . T h e C h a r a o r l i t t o r a l z o n e o f C o u r t n e y L a k e i s c h a r a c t e r i z e d b y l a r g e n u m b e r s o f H y a l e l l a a z t e c a , H u m p h r e y s ( 1 9 6 4 ) . F i s h e s f o u n d i n M a r q u e t t e L a k e a r e r a i n b o w t r o u t ( S a l m o g a i r d n e r i ) a n d b r o o k t r o u t ( S a l v e l i n u s f o n t i n a l i s ) . C o r b e t t L a k e h a s t h e s a m e s p e c i e s a n d i n b o t h l a k e s t h e y o c c u r i n a b o u t e q u a l n u m b e r s . R a i n b o w t r o u t ( S a l m o g a i r d -n e r i ) o c c u r i n C o u r t n e y L a k e a n d l a r g e n u m b e r s o f r e d s i d e s h i n e r s ( R i c h a r d s o n i u s b a l t e a t u s ) a r e a l s o p r e s e n t . T h e t h r e e l a k e s h a v e n o n a t u r a l s p a w n i n g h a b i t a t f o r s a l m o n i d s a n d c o n s e q u e n t l y a r e r e g u l a r l y s t o c k e d b y t h e B.C. F i s h a n d Game B r a n c h . M a r q u e t t e L a k e w a s s t o c k e d w i t h 5 , 0 0 0 S a l v e l i -n u s f o n t i n a l i s a n d 5 , 0 0 0 S a l m o g a i r d n e r i i n t h e s u m m e r s o f 1 9 6 2 , 1 9 6 3 a n d 1 9 6 4 . C o r b e t t L a k e w a s s t o c k e d i n 1 9 6 2 w i t h 7 , 0 0 0 S a l m o g a i r d n e r i a n d 5 , 0 0 0 S a l v e l i n u s f o n t i n a l i s ; i n 1 9 6 3 a n d 1 9 6 4 w i t h 5 , 0 0 0 e a c h o f S a l v e l i n u s f o n t i n a l i s a n d S a l m o g a i r d n e r i . C o u r t n e y L a k e w a s s t o c k e d o n l y w i t h S a l m o  g a i r d n e r i ; 5 , 4 0 0 i n 1 9 6 2 , 3 , 4 0 0 i n 1 9 6 3 a n d 1 0 , 0 0 0 i n 1 9 6 4 . 8 METHODS AND M A T E R I A L S G E N E R A L L I M N O L O G Y C o n t o u r m a p s f o r e a c h l a k e w e r e d r a w n f r o m s o u n d -i n g s t a k e n w i t h a F u r u n o 2 0 0 K c . , m o d e l F - 7 0 ' l , r e c o r d i n g e c h o s o u n d e r . I m p r o v e d a c c u r a c y o f o u t l i n e m a p s w a s o b t a i n e d b y a d j u s t i n g a i r i n t e r i m s e r i e s ( B . C . D e p a r t m e n t o f L a n d s a n d F o r e s t s ) t h r o u g h t h e u s e o f e n l a r g e d a i r p h o t o s o f e a c h l a k e . A l l m o r p h o m e t r i c d a t a w e r e t h e n c a l c u l a t e d f r o m t h e m a p s . M e t e o r o l o g i c a l d a t a w e r e c o l l e c t e d f r o m t w o t o t a l -i z i n g a n e m o m e t e r s ( M u n r o , L o n d o n ) a n d t w o w i n d d i r e c t i o n r e c o r d e r s ( S c h m i d t a n d M a r s h a l l , 1 9 6 0 ) . T h e s e i n s t r u m e n t s w e r e m o u n t e d o n r a f t s o n C o r b e t t a n d C o u r t n e y L a k e s a t a b o u t 0.5 m e t r e a b o v e t h e l a k e s u r f a c e ( F i g . 2 ) . A s a m p l i n g s t a t i o n w a s s e t u p o n e a c h l a k e a n d p e r m a n e n t l y m a r k e d i n 1 9 6 2 . S a m p l i n g w a s c o n d u c t e d m o r e o r l e s s m o n t h l y . T r a n s p a r e n c y w a s m e a s u r e d w i t h a s t a n d a r d ( 2 0 cm d i a m . ) S e c c h i d i s k u s i n g a g l a s s v i e w i n g b o x . No S e c c h i d i s k r e a d i n g s w e r e t a k e n d u r i n g i c e c o v e r . Some t r a n s p a r -e n c y m e a s u r e m e n t s w e r e made w i t h a s u b m a r i n e p h o t o m e t e r ( M o d e l 15-M-02/1-GM M a n u f a c t u r i n g C o m p a n y ) e q u i p p e d w i t h W e s t o n P h o t r o n i c P h o t o - e l e c t r i c " d e c k " a n d " s e a " c e l l s . 9 V e r t i c a l t e m p e r a t u r e s e r i e s w e r e t a k e n w i t h a T e l e - t h e r m o m e t e r u s i n g a r a p i d r e s p o n d i n g t h e r m i s t o r ( Y e l l o w S p r i n g s I n s t r u m e n t C o m p a n y , I n c . , M o d e l 4 4 T B ) . D i s s o l v e d o x y g e n d e t e r m i n a t i o n s w e r e m a d e u s i n g t h e u n m o d i f i e d W i n k l e r m e t h o d . W a t e r s a m p l e s w e r e t a k e n w i t h a s t a n d a r d K e m m e r e r b o t t l e a n d w a t e r s a m p l e s f o r o x y g e n d e t e r m i n a t i o n w e r e " f i x e d " i n 3 0 0 m. B.O.D. b o t t l e s . I n m o s t c a s e s t h e s a m p l e s w e r e t i t r a t e d w i t h i n 24 h o u r s . D u r -i n g t h e e x p e r i m e n t a l c i r c u l a t i o n o f C o r b e t t L a k e , s a m p l e s w e r e t i t r a t e d t w o t o f o u r h o u r s a f t e r h a v i n g b e e n t a k e n . H y d r o g e n s u l p h i d e d e t e r m i n a t i o n s w e r e m a d e u s i n g a c o l o u r c o m p a r a t o r s e t ( H a c h e C h e m i c a l C o m p a n y , A m e s , I o w a , T e s t P a p e r N o . 3 9 3 ) . M e a s u r e m e n t s o f pH w e r e t a k e n a t t h e i m m e d i a t e t i m e o f s a m p l i n g w i t h a p o r t a b l e b a t t e r y o p e r a t e d pH m e t e r ( A n a l y t i c a l M e a s u r e m e n t s I n c . , N . J . ) — p r o b a b l y a c c u r a t e t o a b o u t 0.3 p H u n i t s . Some a d d i t i o n a l p H r e a d i n g s w e r e t a k e n i n 1 9 6 5 w i t h a B e c k m a n N p o r t a b l e pH m e t e r . T o t a l d i s s o l v e d s o l i d s w e r e d e t e r m i n e d b y t h e e v a p o r a t i o n m e t h o d o u t l i n e d i n S t a n d a r d M e t h o d s ( A m e r i c a n P u b l i c H e a l t h A s s o c i a t i o n I n c . , 1 9 6 0 ) a n d m o d i f i c a t i o n s s u g -g e s t e d b y t h e B.C. R e s e a r c h C o u n c i l ( s t r e a m e v a p o r a t i n g f o r o n e h o u r a n d d e s s i c a t i n g f o r o n e h o u r ) a n d b y R a w s o n ( d r y -i n g a t 110°C. T o t a l d i s s o l v e d s o l i d s d e t e r m i n e d i n 1 9 5 2 10 w e r e d o n e b y t h e B.C. R e s e a r c h C o u n c i l . P h e n o l p h t h a l e i n a n d M e t h y l O r a n g e a l k a l i n i t y w e r e d e t e r m i n e d b y t h e m e t h o d o u t l i n e d i n S t a n d a r d M e t h o d s ( A m e r i -c a n P u b l i c H e a l t h A s s o c i a t i o n I n c . , 1 9 6 0 ) w i t h t h e e x c e p t i o n t h a t t h e t i t r e w a s 0 . 1 0 N, H2SO4. I n s i t u c o n d u c t i v i t y r e a d i n g s w e r e t a k e n w i t h a m o d e l R B 2 - 3 3 4 1 S o l u B r i d g e ( I n d u s t r i a l I n s t r u m e n t s , U . S . A . ) . P l a n k t o n s a m p l i n g w a s c o n d u c t e d w i t h a s t a n d a r d ( 2 2 . 9 cm d i a m . ) W i s c o n s i n c l o s i n g n e t w i t h a n e t m e s h s i z e o f 0 . 1 5 8 mm ( 1 0 9 m e s h e s p e r i n c h ) . B o t t o m s a m p l e s w e r e t a k e n u s i n g a 1 5 . 2 4 cm (6 i n c h s q u a r e E k m a n d r e d g e ) . M o n o f i l a m e n t n y l o n g i l l n e t s w e r e u s e d f o r f i s h s a m p l i n g . I n t h e w i n t e r n e t s w e r e s e t u n d e r t h e i c e b y m e a n s o f a p r a i r i e i c e j i g g e r . O b s e r v a t i o n s o n f i s h p o p u -l a t i o n s d u r i n g t h e w i n t e r w e r e a l s o made t h r o u g h t h e u s e o f SCUBA. E X P E R I M E N T A L C I R C U L A T I O N E x p e r i m e n t a l c i r c u l a t i o n o f C o r b e t t L a k e w a s e f f e c t e d t h r o u g h t h e u s e o f a 7 2 6 m ( c i r c u m f e r e n c e ) p l a s t i c p i p e ( i n s i d e d i a m . 2.5 cm) w i t h 0 . 0 8 cm h o l e s d r i l l e d e v e r y 3.7 m e t e r s ( F i g . 3 ) . A n a t t e m p t w a s made t o s u s p e n d t h e w e i g h t e d p i p e f r o m s u r f a c e r a f t s a t a d e p t h o f a b o u t 1 2 -F i g . 3. L a y o u t o f C o r b e t t L a k e e x p e r i m e n t a l COMPRESSOR • A - G = STAT IONS «A IOO l 0 0 M ,8 12 13 meters. Compressed a i r was supplied to the system by an Atlas Copco V.T. 4, 160 c.f.m. a i r compressor which was operated at 90 - 100 lbs/sq i n . In 1962 the compressor was powered by a gasoline engine and i n 1963 a d i e s e l driven machine was u t i l i z e d . In addition to limnology Station I on Corbett Lake, seven other stations were established. Records of oxygen, temperature, and some readings of transparency, a l k a l i n i t y and conductivity were taken da i l y at Station I. At Stations B and C oxygen and temperature were recorded d a i l y . At Stations A and C to G da i l y v e r t i c a l temperature records were taken. Measurements were not taken da i l y during the 1963 experiment. Oxygen and temperature samples were taken at the extreme "ends" of Corbett Lake, i n 1962, on October 24 and 28, November 7, 9, 20 and 22. On November 23 and 25, 1962, v e r t i c a l oxygen series were taken at Stations A and G. V e r t i c a l temperature recordings at Stations A to G and additional oxygen determinations for Stations A and G and the extreme ends of the lake were taken to e s t a b l i s h the extent of l a t e r a l e f f e c t of a r t i f i c i a l c i r c u l a t i o n . 13 RESULTS COMPARATIVE MORPHOMETRY Courtney Lake i s large and shallow whereas Mar-quette and Corbett Lakes are r e l a t i v e l y small and deep (Table I ) . Consequently Courtney Lake has the smallest mean depth (4.9 m)> Corbett Lake the greatest (7.0 m) and that of Marquette Lake i s intermediate at 5.9 meters. The maximum ef f e c t i v e length i s defined by Welch (1948) as the axis along which the preva i l i n g wind blows. Courtney Lake has the longest maximum e f f e c t i v e length; those of Corbett and Marquette Lakes are considerably smaller. In each case the maximum e f f e c t i v e length d i f f e r s considerably from the maxi-mum length of the lakes. The shore l i n e development of Corbett and Courtney Lakes does not d i f f e r s i g n i f i c a n t l y whereas that of Mar-quette Lake i s somewhat lower. The basin of Corbett Lake has a mean depth to maximum depth r a t i o of 0.36 and thus departs very l i t t l e from that of a true cone (0.33). Marquette Lake basin (0.64) departs markedly from the con i c a l shape and i s more U-shaped whereas Courtney Lake basin i s r e l a t i v e l y saucer-shaped as i s indicated by a small maximum to mean depth ration of 0.29. Another in d i c a t i o n of basin shape i s given by r e l a t i v e depth (Hutchinson, 1957). Relative depth values 14 show the same general trend between lakes with regard to basin shape as the maximum depth to mean depth r a t i o (Fig. 2). (Marquette Lake and Corbett Lake basins are r e l a t i v e l y U-shaped compared to the saucer-shaped basin of Courtney Lake.) Table I. Morphometric parameters of Marquette, Corbett and Courtney Lakes. Marquette Corbett Courtney Lake Lake Lake Area (hectares) 5.3 24.2 71.6 Maximum Depth (m) 9.2 19.5 17.0 Mean Depth (m) 5.9 7.0 4.9 Maximum E f f e c t i v e Length (m) 141.7* 244.3* 946.0 Maximum Length (m) 372.9 990.0 1637.4 Volume (xl0 4m 3) 31.1 168.9 351.2 Shore Line Development 1.2 1.6 1.5 Ratio Mean Depth to Maximum Depth 0.6 0.4 0.3 Relative Depth (%) 3.5 3.5 1.8 Mean Slope of Basin (Degrees) 7°55' 6°9' 3°13' L i t t o r a l Development (%) 8.5 46.4 60.3 * Maximum e f f e c t i v e length i s equal to mean width because winds on Marquette and Corbett Lakes are prevailingly/tvari-able in di r e c t i o n . The mean slope of the basin of Marquette Lake, 7°55*, indicates a r e l a t i v e l y steep-sided basin si m i l a r to 15 that of Corbett Lake which i s 6°9'. The mean slope of the basin of Courtney Lake has the least grade (3°13') of the three lakes. L i t t o r a l development i s defined by Rawson (1939) as the area of the l i t t o r a l zone expressed as a percentage of the t o t a l area. The l i t t o r a l zone, for purposes of th i s study, i s determined by the extent of the Chara growth. SCUBA observations and enlarged a e r i a l photographs show the offshore boundary of Chara to be very d i s t i n c t . The Chara zone of Marquette Lake extends to a depth of 2 meters with a consequent small " l i t t o r a l development" of 8.5% but the l i t -t o r a l zone of Corbett Lake extends to a depth of 4 meters which r e s u l t s i n a larger " l i t t o r a l development" (46.4%). The largest " l i t t o r a l development" i s 60.3% (Courtney Lake) and the l i t t o r a l zone extends to a depth of 4.5 meters. METEOROLOGY The average wind v e l o c i t y on Courtney Lake (199 cm/ sec) i s , on the average, 4.3 times greater than the average wind v e l o c i t y on Corbett Lake - 46.2 cm/sec (Fig. 4). Fre-quent v i s u a l observations and some spot measurements of wind v e l o c i t y on Marquette Lake show i t to be most l i k e that of Corbett Lake but to a lesser degree. Wind di r e c t i o n , l i k e wind v e l o c i t y , was recorded on the immediate lake surface. The wind d i r e c t i o n recorders F i g . 4. A v e r a g e v e l o c i t y o f w i n d o n N o v e m b e r , 1 9 6 2 ) . T h e d o t t e d r e p r e s e n t s a n e s t i m a t e o f a v S3 i m m e d i a t e l a k e s u r f a c e ( J u n e -l i n e f o r M a r q u e t t e L a k e e r a g e w i n d v e l o c i t y . 1 A V E R A G E WIND V E L O C I T Y C M . / S E C . oi O O O O O O "I 1 1 1 91 17 used on Corbett and Courtney Lakes were designed to record the four cardinal compass points (N.S.E.W.) plus the four p r i n c i p a l intermediate compass points. In addition, periods of calm and periods that show wind to be highly variable i n d i r e c t i o n are e a s i l y d i scernible on the recording charts. If the wind were e n t i r e l y random i n d i r e c t i o n the expected average number of hours per week (Fig. 5) i n any d i r e c t i o n would be equal to the t o t a l average number of recorded hours per week divided by the number of recorded directions and/or quadrants. D i f f i c u l t y was encountered i n mounting the wind di r e c t i o n recorders on r a f t s and during the period of recording the r a f t s were subject to some movement (about 10 - 30°). Consequently, the directions that were readable on the recording charts were only those shown i n F i g . 5. For the study period the average number of hours per week of recordable time i n Corbett Lake was 165.1 and the mean num-ber of hours per week that was actually readable from the recording charts was 107.3 while the respective averages for Courtney and Corbett Lakes were 166.2 hours and 103.1 hours. This amounts to the wind d i r e c t i o n on Corbett Lake being measured for 64.9% of the recorded study period and that of Courtney Lake, 62.1%. A pre v a i l i n g wind d i r e c t i o n does not e x i s t for Corbett Lake (predominant d i r e c t i o n i s variable) whereas on Courtney Lake a p r e v a i l i n g wind i s very evident and blows along a 180 - 225° (S.S.W.) axis (Fig. 5). In a l l 1 8 a F i g . 5. A v e r a g e w i n d d i r e c t i o n o n t h e i m m e d i a t e l a k e s u r f a c e s o f C o r b e t t a n d C o u r t n e y L a k e s . S e e t e x t f o r e x p l a n a t i o n o f e x p e c t e d w e e k l y a v e r a g e . 45 225 315 WIND D I R E C T I O N (DEGREES) — — — — EXPECTED WEEKLY AVERAGE 19 p r o b a b i l i t y t h e p r e v a i l i n g w i n d d i r e c t i o n o n M a r q u e t t e L a k e i s a l s o v a r i a b l e . I t i s a l s o p e r t i n e n t t o n o t e t h a t t h e p r e v a i l i n g w i n d d i r e c t i o n o n C o u r t n e y L a k e i s t h e s a m e a s t h e l o n g a x i s o f t h e v a l l e y t o t h e s o u t h o f t h e l a k e ( F i g . 1) . S n o w f a l l i s r e c o r d e d b y a n o f f i c i a l r e c o r d i n g s t a -t i o n n e a r t o t h e s t u d y a r e a a n d i s s u m m a r i z e d i n T a b l e I I . S t r i k i n g d i f f e r e n c e s b e t w e e n t h e m o n t h l y s n o w f a l l f o r t h e w i n t e r o f 1 9 6 2 - 6 3 a n d t h a t f o r t h e w i n t e r s o f 1 9 6 1 - 6 2 a n d 1 9 6 3 - 6 4 a r e e v i d e n t . F i g . 6 s h o w s t h a t s n o w f a l l o n t h e i m m e d i a t e i c e s u r f a c e o f t h e r e s p e c t i v e l a k e s w a s v i r t u a l l y n i l i n 1 9 6 2 - 6 3 a n d c o n s i d e r a b l y g r e a t e r i n 1 9 6 1 - 6 2 a n d 1 9 6 3 - 6 4 . O VER-WINTER F I S H M O R T A L I T Y I n t h e w i n t e r o f 1 9 6 1 - 6 2 a c o m p l e t e o v e r - w i n t e r m o r t a l i t y o f f i s h e s o c c u r r e d i n C o r b e t t L a k e ( T a b l e I I I ) w h e r e a s n o s u c h p h e n o m e n o n w a s r e c o r d e d o r o b s e r v e d i n C o u r t n e y L a k e . I n t h e w i n t e r o f 1 9 6 2 - 6 3 o v e r - w i n t e r m o r -t a l i t y o f f i s h e s d i d n o t o c c u r i n a n y o f t h e s t u d y l a k e s b u t i n 1 9 6 3 - 6 4 a c o m p l e t e m o r t a l i t y o f t r o u t o c c u r r e d i n M a r q u e t t e L a k e . I n a l l p r o b a b i l i t y t h i s w o u l d h a v e o c c u r r e d i n C o r b e t t L a k e a s w e l l i f t h e o x y g e n c o n c e n t r a t i o n h a d n o t b e e n i n c r e a s e d b y e x p e r i m e n t a l c i r c u l a t i o n . Table I I . Monthly snowfall (cm) at the o f f i c i a l recording station nearest the study area (Craigmont Mines, M e r r i t t ) . Snowfall i n cm No. of Days With Measurable Snow Snow on Ground at End of Month 1961 Nov. 29. 21 10 12.70 1961 Dec. 65.79 20 30.48 1962 Jan. N o R e c o r d 1962 Feb. N'./O R e c o r d 1962 Mar. 7.62 3 0 1962 Apr. 0 0 Total 95.00 33 43.18 1962 Nov. 2.79 3 1962 Dec. 12.19 4 1963 Jan. 1.27 2 0 1963 Feb. 4.57 1 0 1963 Mar. 5.08 2 0 1963 Apr. 0 0 0 Total 25.9 12 0 1963 Nov. 12.70 5 0 1963 Dec. 40,89 11 1.62 1964 Jan. 86.61 18 33.0 1964 Feb. 2.54 2 0 1964 Mar. 14.73 5 0 1964 Apr. 5.08 1 0 Total 162.55 42 34.62 Mean annual snowfall for study area = 101.6 cm (Kendrew and Kerr, 1955). to o to F i g . 6. A v e r a g e t h i c k n e s s o f i c e a n d s n o w d e p t h f o r e a c h w i n t e r o f s t u d y ( 3 r e c o r d i n g s 1 9 6 2 a n d 1 9 6 3 ; 4 r e c o r d i n g s 1 9 6 4 ) . 6 0 5 0 co 4 0 3 0 2 0 I O • » • • • • • • • • • • ' 6 2 - 6 3 6 3 - 6 4 M A R Q U E T T E L A K E S N O W ' 6 1 - 6 2 "6 2 - 6 3 ' 6 3 - 6 4 C O R B E T T L A K E C L O U D Y I C E ' 6 1 - 5 2 6 2 - 6 3 ' 6 3 - 6 4 C O U R T N E Y L A K E C L E A R ICE to Table I I I . Record of over-winter f i s h mortality i n Marquette, Corbett and Courtney Lakes (1961 - 1964) - ( A r t i f i c i a l aeration i n Corbett Lake during the autumn of 1962 and 1963.) Date of Sampling Marquette Lake Corbett Lake Courtney Lake 1961 Sep. 30 + N + N 1961 Oct. 28,29 + N + N 1962 Jan. 30 -*D,N + N 1962 Mar. 14 + N 1962 May 3 + N, A 1962 Jun. 28 - N 1962 Aug. + N + N 1962 Nov. 22-26 + N 1962 Dec. 21 + N 1963 Jan. 26 + N 1963 Mar. 4- 8 + D,N + N + N 1963 May + N .+ A + A 1963 Oct. 29 + N 1964 May 2- 3 - N + A,N + N D - Dead f i s h retrieved through use of SCUBA. + - Presence of l i v e f i s h . A - Presence of l i v e f i s h indicated by angling. - - Absence of l i v e f i s h . N - Presence of l i v e f i s h indicated by g i l l net. * - Dead f i s h retrieved from under the Fish were stocked i n Corbett and Marquette i c e . Lakes i n the summer of 1962 and 1963. 23 PHYSICAL CHARACTERISTICS Transparency , Secchi disk readings averaged for a l l seasons except winter show that l i g h t transmission i s greatest i n Corbett Lake (5.48 m) intermediate i n Courtney Lake (5.0 m) and least i n Marquette Lake (3.0 m) (Table IV). Table IV. Mean Secchi disk readings (m); calculated from data c o l l e c t e d i n a l l seasons except winter. Marquette Lake Corbett Lake Courtney Lake 3.0 5.48 5.0 (4 recordings) (12 recordings) (10 recordings) Light i n t e n s i t y and penetration through ice and snow shows the same r e l a t i v e r e l a t i o n s h i p as that for Secchi disk readings (Fig. 7). In Corbett Lake l i g h t penetration and i n t e n s i t y i s considerably greater i n 1963 than i n 1964 (Fig. 8). In 1963 recordable l i g h t penetrates to 19 meters at an i n t e n s i t y of 2.9 lux whereas i n 1964 an in t e n s i t y of 2.9 lux reaches only the 6 meter depth, even though the mean incident l i g h t (6568 lux) i s considerably higher than i n 1963 (4320 lux). Temperature The thermal record of Marquette, Corbett and Court-ney Lakes i s shown for the study period 1961-64 i n Fig. 9. to F i g . 7. L i g h t i n t e n s i t y and p e n e t r a t i o n t h r o u g h i c e and snow c o v e r ( J a n u a r y 30, 1965, and J a n u a r y 31, 1965). LUX 10 T I O O O — I — 2 H 6 H to 8 UJ cC £ I O I I 2 r-Q. UJ I 4 I 6 I 8 2 O M A RQUETTE LAKE (JAN 31/65) COURTNEY LAKE ^ (JAN.31/65) 6 O 5 O 4 O 2 3 0 U 2 O S NOW MARQUETTE CORBETT COURTNEY (JAN. 31/6 5) (JAN.30/6S) (jAN.3</65,) CLOUDY ICE CLEAR ICE I N C I D E N T L I G H T (LUX) M A R Q U E T T E 9700—10800 C O R B E T T C O U R T N E Y 5940 - 8 30 0 6800 -1 I 3 0 0 to to P F i g . 8. L i g h t i n t e n s i t y a n d p e n e t r a t i o n t h r o u g h i c e and' s n o w c o v e r ( J a n u a r y 2 5 , 1 9 6 4 a n d J a n u a r y 2 7 , 1 9 6 3 ) . sr-2 o 7 0 6 0 S O 4 0 3 0 2 O IO Q SNOW T 1964 ( J A N 25) . * LUX IO IOO T IOOO 1 1963 ( JAN 2 7 ^ 1964 ( J A N 25) I * C L O U D Y I C E I 963 ( JAN 2 7) C L E A R I C E I N C I D E N T L I G H T ( A V E R A G E LU %) 19 64 6 5 6 8 1 9 6 3 4 3 2 0 to F i g . 9. S e a s o n a l i s o t h e r m s (°C) f o r M a r q u e t t e , C o r b e t t a n d C o u r t n e y L a k e s f o r t h e d u r a t i o n o f t h e s t u d y p e r i o d 1 9 6 1 - 6 4 . N o t e d u r a t i o n o f i c e c o v e r a n d p e r i o d s o f a r t i f i c i a l c i r c u l a t i o n . 1962 I M J J A S O N D J F ICE COVER •^i EXPERIMENTAL CIRCULATION - - - - - 1 8 - - ' 7.2 I * '• ! -ILO ! * &4 ! " 3. ! • ftB f '{ It""""1 ' /HI""" ' 1 ' ' • ' I ' " ' >l>\ i - ^ t ^ . • — , r&s * ~ - - '• * o '_ .35 MARQUETTE LAKE .57 • 3 : 1961 I 1962 f A S O N D J F M A M J J A S O N D - J F M A 1963 I '964 J J A S O N D . J F M A M A S O N D J F M A M J J A S O N D J F M A M J J O N D J F M A 2 7 G r o s s c h a r a c t e r i s t i c s o f t h e s e a s o n a l t h e r m a l c y c l e a r e o b v i o u s a n d o n l y s a l i e n t f e a t u r e s w i l l b e d i s c u s s e d i n d e t a i l . ( 1 ) Summer S t a g n a t i o n On A u g u s t 3 1 , 1 9 6 2 , t h e m a r k e d s t r a t i f i c a t i o n o f C o r b e t t L a k e i s e v i d e n t f r o m t h e c l o s e n e s s o f t h e i s o t h e r m s i n t h e 4 - 5 m e t e r s t r a t u m . C o u r t n e y L a k e , h o w e v e r , i s n o t a s s h a r p l y s t r a t i f i e d ( t h e i s o t h e r m s a r e m o r e w i d e l y s p a c e d ) a n d h a s a n i l l - d e f i n e d t h e r m o c l i n e b e t w e e n 6 - 8 m e t e r s . T h e d i f f e r e n c e b e t w e e n l a k e s w i t h r e s p e c t t o summer t h e r m a l s t r a t i f i c a t i o n i s b e s t s h o w n i n F i g . 9 b y d a t a f o r t h e sum-m e r o f 1 9 6 2 . C o r b e t t a n d M a r q u e t t e L a k e i s o t h e r m s a r e p a r -a l l e l a n d v e r y c l o s e t o g e t h e r c o m p a r e d t o t h o s e o f C o u r t n e y L a k e w h i c h a r e n o t p a r a l l e l a n d a r e w e l l s p a c e d . T h i s i s a r e f l e c t i o n o f s h a r p t h e r m a l s t r a t i f i c a t i o n i n M a r q u e t t e a n d C o r b e t t L a k e s ( l i t t l e o r n o c i r c u l a t i o n ) w h e r e a s C o u r t n e y L a k e i s v i r t u a l l y u n s t r a t i f i e d a n d w e l l c i r c u l a t e d . T h e d i f f e r e n c e i n s u r f a c e t o b o t t o m t e m p e r a t u r e ( A u g u s t 7 - 9 , 1 9 6 2 ) f o r M a r q u e t t e L a k e i s 1 3 ° C a n d i s s i m i -l a r t o t h e d i f f e r e n c e i n C o r b e t t L a k e (13.6°C) b u t i n C o u r t -n e y L a k e t h e d i f f e r e n c e i s m u c h l e s s ( 5 . 6 ° C ) . C o n s e q u e n t l y C o u r t n e y L a k e i s m u c h w a r m e r t h a n e i t h e r M a r q u e t t e o r C o r -b e t t L a k e . T h e s h a r p d e p r e s s i o n i n i s o t h e r m s b e t w e e n A u g u s t 9 t o 3 1 , 1 9 6 2 , i n C o u r t n e y L a k e a n d t o a l e s s e r d e g r e e b e t w e e n A u g u s t 19 t o 3 1 , 1 9 6 2 , i n C o r b e t t L a k e s h o u l d 28 be noted. Attendant with the depression i n isotherms i s a reduction i n the difference between surface and bottom tem-peratures, p a r t i c u l a r l y i n Courtney Lake (2.8°C); Corbett Lake - 13.4°C. The thermal s t r a t i f i c a t i o n of Corbett Lake during the summer of 1963 i s almost i d e n t i c a l to that of 1962. The c h a r a c t e r i s t i c feature of summer stagnation i n Marquette and Corbett Lakes i s that of well defined s t r a t i -f i c a t i o n and s t a b i l i t y whereas Courtney Lake i s characterized by i l l - d e f i n e d s t r a t i f i c a t i o n and i n s t a b i l i t y as a r e s u l t of mixing. (2) Autumnal C i r c u l a t i o n Natural autumn c i r c u l a t i o n occurs i n a l l three study lakes during the study period only i n the f a l l of 1961 (Fig. 9). Homothermal conditions e x i s t at about the same time and temperature (5.6°C) i n both Corbett and Courtney Lakes as shown by data for October 28, 1961. On October 28 and 29 of 1962 homothermy i s recorded for Courtney Lake at 8.9°C and Marquette Lake i s almost homothermal at 7.2°C—a r e f l e c t i o n of c i r c u l a t i o n from top to bottom i n both lakes. Corbett Lake at t h i s time i s very nearly homothermal at 7.2°C but th i s condition i s a r e s u l t largely of experimental c i r c u l a t i o n . Data for 1963 show Courtney Lake to be i s o -thermal on October 20 whereas Marquette Lake i s well s t r a t i -f i e d and Corbett Lake, even after some experimental c i r c u l a -tion, i s s t i l l sharply s t r a t i f i e d . 29 Autumn c i r c u l a t i o n as r e f l e c t e d i n isotherms of Fig. 9, generally show that Marquette and Corbett Lakes become isothermal at a la t e r date than does Courtney Lake. This i s a r e f l e c t i o n of greater autumnal c i r c u l a t i o n i n Courtney Lake than i n Marquette and Corbett Lakes. (3) Winter Stagnation Typical, winter inverse temperature s t r a t i f i c a t i o n i s shown by under-ice isotherms for the three study lakes (Fig. 9). In addition, differences i n temperature e x i s t . Courtney Lake i s somewhat warmer—5°C i s recorded for Court-ney Lake but not for Corbett Lake (1961-62). Some cooling does occur immediately under the i c e i n both Corbett and Courtney Lakes (1961-62). The depth of 1°C i s depressed from about 0.1 meter to 1.5 meters i n Corbett Lake and to 1 meter i n Courtney Lake. Concurrent with t h i s cooling, the 4° isotherm i n Courtney Lake r i s e s to 3 meters thus r e f l e c -ting an increase i n temperature of the bottom waters. Simi-l a r heating i s recorded by Okland (1964). Under-ice thermal features are sim i l a r i n 1962-63 to those of 1961-62 except that anomolous warming occurs i n a well-defined stratum i n each lake (Fig. 9, March 7 - 8, 1963). Both Corbett and Courtney Lakes are colder i n 1962-63 and Marquette Lake i s si m i l a r to Corbett Lake i n th i s respect. 30 The winter thermal s t r a t i f i c a t i o n of 1963-64 i s almost i d e n t i c a l to that of 1962-63. No anomalous warming occurs i n 1963-64. (4) Vernal C i r c u l a t i o n Complete vernal c i r c u l a t i o n does not occur i n Cor-bett Lake whereas Courtney Lake i s f u l l y c i r c u l a t e d i n the spring (Fig. 9, May 3, 1962). S i m i l a r l y , for May 13, 1964, temperature data shows that Marquette and Corbett Lakes are not completely c i r c u l a t e d but Courtney Lake i s well mixed. Vernal c i r c u l a t i o n occurs about two weeks l a t e r i n 1964 because of an extended period of i c e cover. The same phen-omenon of respective incomplete and complete mixing for Marquette, Corbett and Courtney Lakes occurs i n the spring of 1964 (Fig. 9). S t a b i l i t y S t a b i l i t y i s the amount of work needed to mix the enti r e body of water to uniform temperature without changing i t s mean temperature (Eckel, 1950 quotes Schmidt, 1928). Formulae for the calculated s t a b i l i t y (Eckel, 1950) show that the computations take into account both the density changes imparted by thermal s t r a t i f i c a t i o n and the morphom-e t r i c features of the lake basin. In the study lakes, density changes r e s u l t i n g from chemical s t r a t i f i c a t i o n are probably minimal. Thus, a quantitative statement of the amount of work necessary for f u l l c i r c u l a t i o n of each lake 31 can be made. Corbett Lake i s much more stable than i s Courtney Lake (Fig. 10). The s t a b i l i t y of Marquette Lake i s i n t e r -mediate to the other two lakes. Based on thermal s t r a t i f i -cation alone, one would expect Marquette Lake to be as stable as Corbett Lake. I t can be safely assumed, consider-ing the second factor that contributes to s t a b i l i t y — morphometry--that the difference i s due largely to basin size and shape. The r e l a t i v e l y low s t a b i l i t y values for Courtney Lake are primarily the r e s u l t of i l l - d e f i n e d s t r a -t i f i c a t i o n which i n turn i s the r e s u l t of greater wind action on the lake. CHEMICAL CHARACTERISTICS Oxygen (1) Summer Stagnation Corbett Lake i s much more stagnant than i s Court-ney Lake (Fig. 11, August 28, 1961). Dissolved oxygen isopleths of Fig. 9 show that the epilimnion of Corbett Lake extends to a depth of 3 meters whereas that of Courtney Lake reaches a depth of 9 meters. With respect to oxygen then, Corbett Lake (1961) i s sharply s t r a t i f i e d and the concentra-tion per unit volume i s r e l a t i v e l y low compared to a higher mean concentration i n Courtney Lake and a less well defined s t r a t i f i c a t i o n . A complete summer stagnation period i s F i g . 1 0 . S e a s o n a l d i f f e r e n c e s i n S c h m i d t ' s ' o O r t h e r m a l s t a b i l i t y . I 60 140 CM 2 2 0 2 " u 5 IOO > CD < I— 00 8 0 6 O 4 0 2 O / '>» A / \ \ \ * \ \ \ N • X V 3 2 M A Y J U N E ' J U L Y 1 A U G U S T ' S E P T E M B E R 1 O C T O B E R 1962 — A M A R Q U E T T E L A K E • C O R B E T T L A K E P~ • C O U R T N E Y L A K E 33 recorded i n F i g . 11 for 1962. Absolute oxygen concentration i s generally higher i n Courtney Lake, lower i n Corbett Lake and lower s t i l l i n Marquette Lake. The zero mg/1 isopleth oxygen value i s recorded for the duration of the summer i n Corbett Lake and probably also i n Marquette Lake. In Court-ney Lake, however, the zero mg/1 oxygen value i s recorded only for the l a t t e r part of the summer. Consequently, a r e l a t i v e l y large portion (or the whole) of the hypolimnion of Corbett Lake i s deoxygenated but the hypolimnion of Courtney Lake i s r e l a t i v e l y well oxygenated. The cl o s e l y spaced and p a r a l l e l isopleths of Corbett Lake r e f l e c t the sharp s t r a t i -f i c a t i o n and r e l a t i v e s t a b i l i t y opposed to the widely separated isopleths of Courtney Lake which are d i s s i m i l a r i n aspect and therefore r e f l e c t a greater amount of mixing. Data available for Marquette Lake suggests a condition simi-l a r to that of Corbett Lake. The very sudden depression of 0 - 8 mg/1 oxygen concentrations i n Courtney Lake on August 25, 1962, are the re s u l t of a very strong wind. Courtney Lake was subject to an unseasonable, complete mixing on August 25, 1962, (Fig. 11) but Corbett Lake and probably Marquette Lake remain sharply s t r a t i f i e d . The e f f e c t s of experimental c i r c u l a t i o n on oxygen concentration and d i s t r i b u t i o n within the lake w i l l be d i s -cussed i n a l a t e r section. 35 The s t r a t i f i c a t i o n of oxygen i n Corbett Lake for 1963 (Fig. 11) i s almost i d e n t i c a l to that for 1962. Sum-mer data are lacking for Marquette and Courtney Lakes but i f Corbett Lake data are so similar to the preceding summer, i t i s l i k e l y that the oxygen features of Courtney and Mar-quette Lakes would be the same as those of the preceding summer. (2) Autumnal C i r c u l a t i o n Natural c i r c u l a t i o n i s recorded for both Corbett and Courtney Lakes only i n the autumn of 1961 (Fig. 11). Corbett Lake i s incompletely oxygenated and/or c i r c u l a t e d and surface oxygen concentration i s very low compared to the complete c i r c u l a t i o n and rela t i v e l y high surface concentra-tion of Courtney Lake (Fig. 11, October 31, 1961). Autumnal c i r c u l a t i o n of Corbett Lake i n 1963 and 1964 i s a r t i f i c i a l . The 1962 autumn c i r c u l a t i o n of Courtney Lake occurred prematurely on August 25 and r e l a t i v e l y s l i g h t s t r a t i f i c a t i o n occurred before the ice formation (October 31). Marquette Lake does c i r c u l a t e completely but dissolved oxygen concentrations are much lower than those of Courtney Lake. Autumnal c i r c u l a t i o n i s s i m i l a r l y e f f e c t i v e i n 1963— Courtney Lake being oxygenated and Marquette Lake r e l a t i v e l y poor i n oxygen (Fig. 11, November 9, 1963). 36 (3) Winter Stagnation After natural autumn c i r c u l a t i o n (1961) i n Cor-bett Lake, winter stagnation i s severe. V i r t u a l l y no oxygen i s present i n Corbett Lake by mid-March, 1962, whereas the v e r t i c a l extent and concentration of oxygen i n Courtney Lake i s r e l a t i v e l y great. The under-ice oxygen features are unusual i n Mar-quette and Courtney Lakes for the winter 1962-63. A well defined stratum of supersaturation of oxygen i s recorded i n both lakes (Fig. 11, March 7 and 8, 1963). This stratum of supersaturation corresponds exactly with the layer i n which increased temperature i s recorded for the same date (Physi-c a l C h a r a c t e r i s t i c s - Temperature). The under-ice oxygen content of Courtney Lake i s somewhat higher i n 1962-63 than in the previous winter. S i m i l a r l y Corbett Lake has a higher oxygen content. Marquette Lake i s almost completely depleted of oxygen by March 6, 1964, whereas Corbett and Courtney Lakes have much higher mean concentrations of oxygen. The slope of oxygen isopleths under the i c e drawn for Corbett Lake i s much greater than the slope of oxygen isopleths drawn for Courtney Lake (Fig. 11). Oxygen i s o -pleths recorded for Courtney Lake show an i n i t i a l steep slope immediately after i c e cover but for the remaining i c e -37 covered period they are r e l a t i v e l y p a r a l l e l . The slope of isopleths for Marquette Lake, sim i l a r to Corbett Lake, are greater than those of Courtney Lake. Thus, during winter stagnation there i s a more rapid consumption (depletion) of oxygen i n Marquette and Corbett Lakes compared to Courtney Lake and under the normal natural circumstances th i s would r e s u l t i n nearly complete oxygen depletion i n Marquette and Corbett Lakes but not i n Courtney Lake. (4) Vernal C i r c u l a t i o n Vernal c i r c u l a t i o n i n Corbett Lake i s incomplete whereas Courtney Lake i s completely mixed at spring turn-over (Fig. 11, A p r i l 30, 1962). Data recorded at a l a t e r date (June 24, 1962) for Marquette Lake are good evidence for a spring c i r c u l a t i o n s i m i l a r to that of Corbett Lake. Data c o l l e c t e d on Marquette Lake at an e a r l i e r date i n 1963 (May 13) support th i s conclusion. The r e l a t i v e e f f e c t i v e -ness and extent of vernal c i r c u l a t i o n i s well i l l u s t r a t e d by data c o l l e c t e d two days after i c e break-up i n 1964 (Fig. 11). Surface concentration i n Marquette and Corbett Lakes i s low compared to that of Courtney Lake. Hydrogen Sulfide The presence of hydrogen s u l f i d e i n Corbett Lake i s r e s t r i c t e d to the hypolimnion (Fig. 12). Some over-lap i n the presence of hydrogen s u l f i d e and oxygen i s evident 3 8 a F i g . 1 2 . H y d r o g e n s u l f i d e - v e r t i c a l s e r i e s ( J a n u a r y 3 0 , 1 9 6 5 ) . CO oo 39 at about the 12 meter l e v e l . Corbett Lake was experimental-ly c i r c u l a t e d again i n the autumn of 1964 s u f f i c i e n t to provide a mean concentration, top to bottom, of oxygen of about 10 mg/1 pri o r to i c e cover. Thus, the presence of hydrogen s u l f i d e at the 17 meter l e v e l , i n excess of 5 mg/1 must be considered a r e l a t i v e l y high concentration and higher concentrations l i k e l y occur under natural conditions without a r t i f i c i a l autumnal c i r c u l a t i o n . pH Summer (August 28, 1961) pH readings show a gradation from surface to bottom for both Corbett and Court-ney Lakes and (Fig. 13) v e r t i c a l changes i n pH generally p a r a l l e l temperature and oxygen s t r a t i f i c a t i o n . pH read-ings taken during f a l l turn-over (October 28, 1961) r e f l e c t the change i n chemical and physical s t r a t i f i c a t i o n that occurs with autumnal c i r c u l a t i o n . Courtney Lake i s gener-a l l y more a l k a l i n e than Corbett Lake and Marquette Lake i s r e l a t i v e l y a c i d i c compared to Corbett and Courtney Lakes (Fig. 13). A l k a l i n i t y Absolute values of bicarbonate a l k a l i n i t y i n Mar-quette, Corbett and Courtney Lakes are rather si m i l a r (Table V). Carbonate a l k a l i n i t y occurs only i n Courtney Lake. Minimum surface values for carbonate a l k a l i n i t y occur i n the winter and are probably a r e s u l t of the freeze-out o 2 h 4 -6 -8 -I O -I 2 I 4 f-I 6 -1 8 -2 O in UJ ct I-UJ 2 I CL 0 — 2 -4 -6 -8 ~ 1 O -I 2 -I 4 . I 6 -I 8 " 2 0 -O 2 4 6 8 I O I 2 I 4 I 6 h 1 8 2 0 L PH 7 8 T T V A U G . 2 8 /61 I I / pH 7 8 -i • — r O C T . 2 8 /6 I pH 8 - J A N . 3 0 / 6 5 i 9 • 1 9 4 0 M A R Q U E T T E L A K E C O R B E T T L A K E C O U R T N E Y L A K E F i g . 1 3 . V e r t i c a l pH s e r i e s ( 1 9 6 1 a n d 1 9 6 5 ) . Table V. Maximum and minimum bicarbonate and carbonate a l k a l i n i t y (mg/1) recorded during the study period (August 28, 1961 - May 24, 1964). larquette Lake Corbett Lake Courtney Lake Bicarbonate A l k a l i n i t y Depth (m) Maximum 300 (Jun.24/62) 7.6-8.5 365 (Mar.4/63) 350 (Aug.28/61) 10.7-18.3 349 (Aug. 8/62) 329 8.5-10.7 329 (Mar.14/6 2) (Mar.14/6 2) Minimum 150 345 (Mar. 4/63) (Aug.9/62) 35 (Jan. 31/62) 310 (Sep.30/62) 20 285 (Mar. 7/63) (Oct. 1/62) Carbonate A l k a l i n i t y Maximum Minimum N i l N i l N i l N i l N i l N i l N i l N i l 80 (May 20/62) 32 (May 13/62) 74 (May 20/62) 42 phenomenon (Welch, 1952; Anderson,1958a; Krumholz and Cole, 1959). Total Dissolved Solids Courtney Lake has the highest mean concentration of t o t a l dissolved s o l i d s (406 mg/1) and Marquette Lake has least (352 mg/1). Corbett Lake has an intermediate value of 361 mg/1 (Table VI). In each lake the surface concentration i s lower than that of the bottom. Table VI. Mean concentration of t o t a l dissolved s o l i d s (mg/1). (Calculated from data c o l l e c t e d i n Aug-ust, October and December, 1961, and May, 1962, for Corbett and Courtney Lakes—June, 1962, for Marquette Lake. Marquette C o r b e t t L a k e Courtney Lake Lake Depth i n Meters 0 8.5 0 13.1-16.7 0 7.9-9.7 Mean Concentration 294 410 345 377 287 426 Mean Concentration for Whole Lake 352 361 406 Spe c i f i c Conductivity Selected, t y p i c a l summer and winter s p e c i f i c con-d u c t i v i t y readings ( i n s i t u v e r t i c a l series) are presented i n F i g . 14. Autumn (data not shown) recordings are i n t e r -mediate to summer and winter values but vernal recordings for Marquette and Courtney Lakes are s l i g h t l y higher than summer readings whereas spring records for Corbett Lake are yH. M H O S / C M . (25°C) O IOO 2 0 0 4 3 1 1 ^ ' 1 1 X 1 i > » ' M A R Q U E T T E LAKE ( ** I 2 I 6 A U G. 7/6 2 •X MA R. 4/6 3 1 2 O 10 HI 2 Z 8 I I-Q. ui I 2 Q I 6 2 0 L ^ M H O S / C M . (2S°C) I O O 2 0 0 1 — — r -CORBETT L A K E m m AUG. e/62 X X MAR. 5/63 M H O S / C M . (2 5°CJ O 5 0 IOO ISO 2 O O 2 SO 12 h 16 h 2 0 «--WT5 COURTNEY LAKE 1 1 • • AUG. 9/6 2 X - - - X MAR. 7/63 F i g . 1 4 . Summer a n d w i n t e r v e r t i c a l s p e c i f i c c o n d u c t i v i t y v a l u e s . M e a s u r e m e n t s t a k e n i n s i t u . 44 si m i l a r to those of summer. INDICES OF PRODUCTIVITY Physical Ranked morphometric indices of productivity show that Courtney Lake i s most productive ( t o t a l of 19). Cor-bett Lake i s intermediate (14) and Marquette Lake i s least productive ( t o t a l 10) (Table VII). In order to further e s t a b l i s h the r e l a t i v e productivity of each lake winter areal oxygen d e f i c i t s were calculated (Hutchinson, 1957, p l a n i -metric method). . Chemical Hypolimnetic areal oxygen d e f i c i t s are used as an index of productivity i n s t r a t i f i e d lakes because i t i s assumed that organic seston from the trophogenic layer, "raining" down (into the tropholytic zone) w i l l use oxygen i n the same proportion to the amount of production i n the tro-phogenic zone. Thus a measure of oxygen consumed i n unit time per unit area i s a measure of productivity. Courtney Lake i s not sharply s t r a t i f i e d i n the summer, therefore the method could not be used on a comparative basis. In Corbett Lake, during the winters of 1961-62, 1962-63 and 1963-64, there i s no evidence for an increase i n dissolved oxygen after ice cover and therefore the t o t a l lake area (T) i s used i n calcu-l a t i n g oxygen d e f i c i t s (Table VII). In Courtney Lake, 45 Table V i l a . Morphometric indices of ; productivity (ranked). Marquette Lake Corbett Lake .Courtney Lake Mean Depth ? 2 1 3 Maximum E f f e c t i v e Length 1 2 3 Shoreline Development 2 3 1 Ratio Mean Depth to Maxi-mum Depth 1 2 3 Relative Depth 2 2 3 Mean Slope of Basin 1 2 3 L i t t o r a l Development 1 2 3 Total 10 14 19 Table V l l b . Chemical indices of productivity. Marquette Lake Corbett Lake Courtney Lake Oxygen D e f i c i t s mg/cm.2/day 0ct.28-Mar. 15, 1961-62 No data 0.0165(T) 0.0282 Dec.21, 1962 (Theoretical) 0.0077 0.0469(T) 0.1315 Nov.24, 1963 (Theoretical) 0.0163 0.0965(T) 0.1339 (Theoretical) - see text for explanation. (T) - Total lake area u t i l i z e d i n c a l c u l a t i n g d e f i c i t (see text). 46 however, there i s evidence for an increase i n dissolved oxygen after i c e cover and consequently the area of the hypolimnion, for purposes of computing areal oxygen d e f i c i t , i s determined by the depth at which no increase i n oxygen concentration over the previous reading i s recorded. "Theoretical" oxygen d e f i c i t s are calculated because there i s a s l i g h t difference i n freeze-over time for each lake and the rate of oxygen consumption i n each lake i s greatest immediately after i c e cover (Fig. 11). Therefore, i f oxygen d e f i c i t s were calculated for each lake, say two weeks after freeze-over, a meaningful comparison could not be made. In order to make r e l i a b l e comparisons of oxygen d e f i c i t s between lakes, the surface oxygen concentration recorded on December 21 and November 24 of 1962 arid 1963 respectively was assumed to be the top to bottom concentra-tion for each lake at the time of freeze-over. Areal oxygen d e f i c i t s were calculated on the difference of thi s " t h e o r e t i -c a l " value and those values actually recorded on the above-mentioned dates. Each winter areal oxygen d e f i c i t i n Table VII shows that Courtney Lake i s more productive than Corbett Lake and that Marquette Lake i s the least productive. Preliminary C ^ investigations were begun on Janu-ary 30, 1965. Water samples were c o l l e c t e d at 0, 1 and 2 meters from Marquette, Corbett and Courtney Lakes and 47 incubated, without ice and snow cover, i n Corbett Lake at the same depths of c o l l e c t i o n . Replicates varied consider-ably and consequently the data are not too r e l i a b l e . The general trend, however, showed that Courtney Lake was the most productive of the three. EXPERIMENTAL CIRCULATION Experimental c i r c u l a t i o n i s evidenced i n depres-sed isotherms and depressed and altered dissolved oxygen isopleths (Figs. 9 & 11). In 1962 (Fig. 9) the f i r s t nine days of experimental c i r c u l a t i o n depressed the 6°C isotherm 3.25 meters. In 1963 during the f i r s t eight hours of a r t i -f i c i a l c i r c u l a t i o n the 8°C isotherm i s depressed 2.5 meters. Oxygen isopleths show sharp changes s i m i l a r to those of isotherms, during experimental c i r c u l a t i o n . The i n i t i a l e f f e c t of experimental c i r c u l a t i o n i s to reduce the mean concentration of oxygen (Fig. 15). (Mean concentration of oxygen i s determined pl a n i m e t r i c a l l y on the concentration—depth curve.) A second immediate e f f e c t of a r t i f i c i a l c i r c u l a t i o n i s a strong odour of hydrogen s u l f i d e which persisted i n 1962 from October 17 ( c i r c u l a t i o n started) and decreased gradually u n t i l November 23. Fig . 15 shows the i n i t i a l reduction i n the mean 4 8 a F i g . 1 5 . D a i l y c h a n g e s i n m e a n o x y g e n c o n c e n t r a t i o n a n d t h e v e r t i c a l e x t e n t o f d i s s o l v e d o x y g e n e f f e c t e d b y t h e e x p e r i m e n t a l c i r c u l a t i o n o f C o r b e t t L a k e , 1 9 6 3 a n d 1 9 6 2 . ( N o t e h o u r s o f e x p e r i m e n t a l c i r c u l a t i o n a n d s u r f a c e w a t e r t e m p e r a t u r e . ) (5 s • 3 z UJ O | ' - - i ACCUMULATED HOURS OF EXPERIMENTAL CIRCUL AT I ON SURFACE WATER TEMPERATURE nnn VERTICAL EXTENT OF OXYGEN , MEAN CONCENTRATION OF OXYGEN START EXPERIMENTAL CIRCULATION 49 concentration of oxygen from 6.39 mg/1 to 5.62 mg/1 i n the f i r s t four hours of c i r c u l a t i o n (October 17, 1962). After 18 hours of a r t i f i c i a l c i r c u l a t i o n a minimum of 4.70 mg/1 was reached (October 18, 1962). The accompanying changes i n v e r t i c a l penetration of oxygen were from 10.7 meters to 12.2 meters i n the f i r s t four hours and from 12.2 meters to 13.7 meters i n 18 hours of c i r c u l a t i o n (Fig. 15). L i t t l e increase i n mean concentration of oxygen was shown (October 17 - 19) during the f i r s t period of experimental c i r c u l a t i o n . From October 18 to 25 there was greatest increase i n depth penetration of oxygen (13.7 to 17.5 meters), whereas the greatest increase i n mean concen-tr a t i o n (October 25 to 28) was attendant with the smallest increase i n v e r t i c a l extent of oxygen (17.5 to 18.3 meters). From October 29 to November 7, 1962, Corbett Lake was not c i r c u l a t e d experimentally and the mean concentration of oxygen dropped from 5.50 mg/1 to 4.85 mg/1 (surface water temperature was s t i l l r e l a t i v e l y high, F i g . 15). A r t i f i c i a l c i r c u l a t i o n was again i n i t i a t e d from November 7 to 8 and a substantial increase i n mean oxygen concentration was e v i -dent (4.85 to 5.63 mg/1). I t i s pertinent to note that the lake was oxygenated from surface to bottom on October 28. Although the oxygen concentration decreased from October 29 to November 7 there was no oxygen d e f i c i t at the bottom of the lake, for that period. Accompanying changes i n surface 50 w a t e r t e m p e r a t u r e ( F i g . 1 6 ) a r e d o u b t l e s s c o r r e l a t e d w i t h t h e r a t e o f s o l u t i o n o f o x y g e n . A r t i f i c i a l c i r c u l a t i o n a g a i n c e a s e s f r o m N o v e m b e r 10 t o 1 8 b u t t h e m e a n c o n c e n t r a t i o n o f o x y g e n i n c r e a s e s a n d i s p r o b a b l y t h e r e s u l t o f n a t u r a l c i r c u l a t i o n s c o u p l e d w i t h d e c r e a s e d s u r f a c e w a t e r t e m p e r a t u r e . F r o m N o v e m b e r 18 t o 26 t h e r a t e o f i n c r e a s e i n m e a n o x y g e n c o n c e n t r a t i o n i s m u c h i n c r e a s e d a n d a m a x i m u m o f 8.28 mg/1 i s r e a c h e d o n N o v e m b e r 26 a f t e r 3 5 9 . 2 h o u r s o f e x p e r i m e n t a l c i r c u l a t i o n . A s i m i l a r t r e n d i n c h a n g e o f m e a n o x y g e n c o n c e n -t r a t i o n a n d a g r a d u a l p e n e t r a t i o n o f d i s s o l v e d o x y g e n f r o m s u r f a c e t o b o t t o m i s e v i d e n t f o r t h e p e r i o d o f e x p e r i m e n t a l c i r c u l a t i o n i n 1 9 6 3 - - t h e m e a n c o n c e n t r a t i o n o f o x y g e n a t t h e e n d o f t h e e x p e r i m e n t b e i n g 6.80 m g / 1 — a r e s u l t o f 1 8 0 h o u r s o f e x p e r i m e n t a l c i r c u l a t i o n . T h e l a t e r a l e x t e n t o f e x p e r i m e n t a l c i r c u l a t i o n w a s a s s e s s e d b y p e r i o d i c a n d d a i l y t e m p e r a t u r e a n d o x y g e n r e a d i n g s a t S t a t i o n s A t o G ( F i g . 3 ) . D a i l y v e r t i c a l t e m p e r a t u r e r e c o r d s a t S t a t i o n s A t o G s h o w t h a t a r t i f i c i a l c i r c u l a t i o n d o e s i n d e e d a f f e c t C o r b e t t L a k e a t i t s e x t r e m e e n d s . H o w e v e r , t h e r e i s a t i m e - l a g b e t w e e n t h e c h a n g e s e f f e c t e d a t S t a t i o n 1 a n d t h e m o r e d i s t a n t s t a t i o n s . W a t e r s a m p l e s t a k e n a t S t a t i o n s A a n d G o n t h e 5 1 2 5 t h o f N o v e m b e r , 1 9 6 2 , h a v e a m e a n c o n c e n t r a t i o n o f 8.2 mg/1 a n d 8.7 r e s p e c t i v e l y . F r o m t h e s e d a t a i t i s d e d u c e d t h a t e x p e r i m e n t a l c i r c u l a t i o n e f f e c t i v e l y i n c r e a s e d t h e m e a n c o n -c e n t r a t i o n o f o x y g e n i n t h e e n t i r e l a k e v o l u m e . O x y g e n d e t e r m i n a t i o n s a t S t a t i o n s A a n d G, h o w e v e r , may b e a f f e c t e d b y o x y g e n p r o d u c e d p h o t o s y n t h e t i c a l l y i n t h e l i t t o r a l z o n e . O x y g e n p u l s e s m e a s u r e d i n t h e l i t t o r a l z o n e a t t h e e x t r e m e " e n d s " o f C o r b e t t L a k e o n N o v e m b e r 2 0 - N o v e m b e r 2 1 a n d N o v e m b e r 2 2 t o 2 3 , 1 9 6 2 , s h o w e d 12 h o u r d i f f e r e n c e s a s g r e a t a s 2.5 mg/1 a n d a s s m a l l a s 1.9 mg/1. H o w e v e r , i n C o r b e t t L a k e t h e c o n t r i b u t i o n o f o x y g e n f r o m a p h o t o s y n t h e t i c s o u r c e i s p r o b a b l y s m a l l a n d t h e l a r g e c h a n g e s i n m e a n o x y g e n c o n -c e n t r a t i o n a n d v e r t i c a l p e n e t r a t i o n a r e d o u b t l e s s t h e r e s u l t o f e x p e r i m e n t a l c i r c u l a t i o n . D I S C U S S I O N R E L A T I V E P R O D U C T I V I T Y L a k e s t h a t a r e s u b j e c t t o o v e r - w i n t e r m o r t a l i t y o f t r o u t p o p u l a t i o n s a r e g e n e r a l l y s h a l l o w a n d h i g h l y p r o d u c -t i v e . C o u r t n e y L a k e i s s h a l l o w e r a n d m o r e p r o d u c t i v e t h a n C o r b e t t L a k e . C o n s e q u e n t l y o n e w o u l d e x p e c t t h a t C o u r t n e y L a k e , r a t h e r t h a n C o r b e t t L a k e , w o u l d b e s u b j e c t t o w i n t e r m o r t a l i t y o f f i s h e s . T h e r e f o r e , a n e x a m i n a t i o n o f t h e p r o d -u c t i v i t y o f t h e l a k e s s h o u l d h e l p t o e x p l a i n t h e e x p e c t e d d i f f e r e n c e s w i t h r e s p e c t t o w i n t e r m o r t a l i t y o f f i s h e s . 52 Morphometric parameters are frequently employed by limnologists as indices of productivity (Rawson, 1939, 1955, 1961; Northcote and Larkin, 1956; Larkin and Northcote, 1958). Limnologists are generally agreed that no single parameter serves alone as an index of productivity and that the i n t e r - r e l a t i o n s h i p s of the e f f e c t s of d i f f e r e n t param-eters are complex. Rawon (1939) c l a s s i f i e d the factors influencing lake productivity into three groups: morphom-e t r i c , edaphic, and cli m a t i c . Rawson (1939) states that edaphic and clim a t i c factors cause over-riding deviations from the correlations between morphometry and productivity. In t h i s study, morphometric and l o c a l c l i m a t i c differences are largely responsible for differences i n productivity. Rawson (1939, 1952, 1955 and 1961) correlated low mean depth with r e l a t i v e l y high productivity i n large Can-adian lakes. Larkin (1964) maintains that mean depth i s a valuable indicator for capacity of b i o l o g i c a l production within limited areas. Small lakes are treated by Hayes and Anthony (1964) who f i n d that there i s good c o r r e l a t i o n between high "Productivity Index" and low mean depths (1.4-11.6 m). On the basis of mean depth, Courtney Lake (4.9 m) i s most productive, Marquette Lake (5.8 m) next most produc-tive and Corbett Lake (6.9 m) i s least productive of a l l three. 53 "A lake with a gradually sloping basin or with broad shoals could normally be expected to be more produc-tive b i o l o g i c a l l y than a deep lake with steep sides.", (Reid, 1961). Basin shape i s indicated by the r a t i o of mean depth to maximum depth and mean slope. Shoal area i s indicated by " l i t t o r a l development". The contribution of each index of productivity (above) to the r e l a t i v e produc-t i v i t y of each lake r e s u l t s i n the same inter-lake r e l a t i o n -ship-—Courtney Lake i s most productive, Marquette Lake i s least productive and Corbett Lake i s intermediate. North-cote and Larkin (1956) c i t e a case, s i m i l a r to t h i s study, wherein two basins with similar a l t i t u d e , climate, substrate and area d i f f e r because one has a greater productivity which i s due to " the more productive of the two having extensive shoal areas " Probably the most s i g n i f i c a n t morphometric param-eter i n t h i s limnological comparison i s maximum e f f e c t i v e length. Larkin (1964) maintained that c l i m a t i c and edaphic factors are responsible for over-riding the r e l a t i o n s h i p between morphometry and productivity. The maximum e f f e c t i v e length of Marquette, Corbett and Courtney Lakes (141.68, 244.30 and 946.0 meters respectively) demonstrates the dram-a t i c differences i n wind action on the lakes. The e f f e c t of wind action on productivity i s con-sidered by several investigators (Larkin, 1964; Murphy, 1962; Patalas 1960b; Rawson, 1961; Larkin and Northcote, 54 1958). A l l are agreed that increased mixing of a lake does indeed increase production. Courtney Lake on the average i s subject to 4.3 times as much wind as Corbett Lake and Mar-quette Lake receives less wind on the average than does Corbett Lake. C 1^ data c o l l e c t e d on January 30, 1965, further support, i n part, the above conclusions regarding the produc-t i v i t y of the three lakes (Fig. 15). Replications of determinations vary considerably and thus the data are probably not too dependable. They do show, however, that Courtney Lake i s the most productive of the three study lakes. Any single index of productivity discussed above may not alone be conclusive demonstration of the produc-t i v i t y of the respective lakes. However, ranked morphom-e t r i c indices of productivity, the r e l a t i v e amounts of wind action and the respective winter oxygen d e f i c i t s a l l show that Courtney Lake i s more productive than Corbett Lake which i s more productive than Marquette Lake (Table VIII). In addition, preliminary C ^ data Show Courtney Lake to be the most productive of the three lakes. The o r i g i n a l premise states that: productive shallow lakes are more l i k e l y to be subject to over-winter mortality of f i s h populations than are less productive, deeper lakes. The data i n Table VIII demonstrate the 55 productivity of each lake i n r e l a t i o n to i t s neighbours and on t h i s basis one would expect Courtney Lake to be sub-j e c t to frequent over-winter m o r t a l i t i e s of fishes and that Corbett and Marquette Lakes would not. However, records of winter f i s h m o r t a l i t i e s show that Marquette and Corbett Lakes are subject to th i s phenomenon and Courtney Lake i s not. Table VIII. Summary of indices of productivity. Marquette Lake Corbett Lake Courtney Lake Ranked Morphometric Indices of Productivity (Summed) (Table VII) 10 14 19 Ratio of Average Wind Velocity (Fig. 4) 1 1.3 5.7 Ratio of Oxygen D e f i c i t s 1 6 12.6 TOPOGRAPHY AND WIND ACTION Marquette and Corbett Lakes are c l o s e l y bordered by high r i s i n g h i l l s p a r a l l e l to the long axis of the lakes (Fig. 1). Courtney Lake, on the other hand, i s not as cl o s e l y bounded by protective h i l l s and i s consequently well exposed to the pr e v a i l i n g winds. As a r e s u l t of exposure the mean t o t a l wind recorded for Courtney Lake i s 4.3 times greater than that recorded for Corbett Lake. Marquette Lake being even more 56 surrounded by shielding h i l l s , i s probably subject to even less wind action. Total wind action on Courtney Lake i s not only greater, on the average, than that of Corbett and Mar-quette Lakes, but i t i s predominantly u n i d i r e c t i o n a l . The major portion of t o t a l wind action on Corbett Lake and prob-ably on Marquette Lake i s variable i n d i r e c t i o n . A strong pre v a i l i n g wind w i l l produce agitat i o n and waves on a lake surface whereas a weak wind, variable i n d i r e c t i o n , w i l l produce l i t t l e surface ag i t a t i o n . Break-ing waves were rarely seen on Corbett Lake, never on Mar-quette Lake but frequently on Courtney Lake. In th i s instance, wave action i s of paramount importance i n oxygen-ation (pers. comm. Dr. R.W. Stewart). Thus, wind acting on Courtney Lake i n a preva i l i n g d i r e c t i o n produces breaking waves which are largely responsible for complete mixing and a higher mean oxygen concentration than i s found i n Mar-quette or Corbett Lakes. Conversely, lower winter oxygen concentration and incomplete autumnal mixing of Marquette and Corbett Lakes are the r e s u l t of i n s u f f i c i e n t and v a r i -able winds that do not produce breaking waves and consequent high oxygen concentrations. An excellent example of the difference i n wind action that the exposure of the three lakes affords i s provided by an-unusually strong wind on August 25, 1962. Weekly t o t a l i z i n g anemometer readings for both Corbett and 57 Courtney Lakes for the week August 15-22 and 22-29 are higher than the weekly average for the period of recording. The e f f e c t of the strong wind was to completely mix Courtney Lake (Fig. 11) whereas Corbett Lake was r e l a t i v e l y undisturbed and Marquette Lake was probably equally unaffected. A consideration of Schmidt's s t a b i l i t y values (Fig. 10), or the amount of work necessary to c i r c u l a t e a lake, explains i n part, the d i f f e r e n t i a l e f f e c t of the above men-tioned wind. The amount of work necessary to c i r c u l a t e Corbett Lake (August 7, 1962) i s much greater than the amount necessary to mix Marquette Lake, which i n turn i s greater than the quantity necessary for Courtney Lake. Consequently, i f each lake did receive the same amount of wind on August 25, 1962, Courtney Lake would be most l i k e l y to have mixed followed by Marquette Lake and Corbett Lake would probably be least affected. The drop i n s t a b i l i t y of Courtney and Cor-bett Lakes between August 7 and 19 respectively and the end of August i s probably due to the increased wind action. This d i f f e r e n t i a l e f f e c t of c i r c u l a t i o n and oxygenation i s c r i t i -c a l at the time of autumnal c i r c u l a t i o n (Fig. 11 - Autumn, 1961, 1962 and 1963). The consequence of incomplete autumnal c i r c u l a t i o n was low oxygen concentration prior to ice-cover which resulted i n a complete over-winter mortality of f i s h i n Corbett Lake (1961-62). Si m i l a r l y , incomplete autumnal c i r c u l a t i o n of 58 Marquette Lake resulted i n t o t a l over-winter f i s h mortality i n 1963-64 and i n a l l p r o b a b i l i t y the same phenomenon would have occurred under ice cover i n 1962-63 except for unusu-a l l y l i g h t snow f a l l that winter. Because of differences i n autumnal c i r c u l a t i o n , fishes i n Corbett and Marquette Lakes were subject to over-winter mortality and those of Courtney Lake were not. Winter m o r t a l i t i e s of fishes i n Corbett Lake were prevented i n 1963-64 arid 1962-63 by experimental c i r c u -l a t i o n . SNOW COVER AND WINTER LIMNOLOGY Anomalous physical and chemical limnological con-di t i o n s recorded during the winter of 1962-63 are p r i n c i p a l l y the r e s u l t of a below-average snow f a l l . The e f f e c t of snow and ice cover, and e s p e c i a l l y snow cover, on photosynthetic oxygen production and the cor-responding e f f e c t on f i s h s u r v i v a l has been documented (Greenbank, 1945; Cooper and Washburn, 1946; Foster, 1960; Woods, 1961; Carufel, 1962). In a l l instances, complete, severe or p a r t i a l m o r t a l i t i e s of f i s h populations are cor-related with heavy snow cover and s u r v i v a l of the respective f i s h populations i s correlated with the absence, periodic, or l i g h t snow cover. In p a r t i c u l a r , Greenbank (1945), Woods (1961) and Carufel (1962) f i n d fluctuations of dissolved oxygen con-centrations correlated with f l u c t u a t i o n of snow cover, i n 59 shallow lakes, within one winter. L i t t l e such f l u c t u a t i o n i s recorded for t h i s study within one winter but s i m i l a r c o rrelations of winter oxygen concentrations and degree of snow cover are evident between winters. Relatively high snow f a l l (Fig. 6) i n 1961-62 and 1963-64 resulted i n rapid depletion of oxygen i n Corbett Lake (1961-62) and Marquette Lake (1963-64) with consequent complete m o r t a l i t i e s of the respective f i s h populations. In 1962-63 the snow f a l l was almost n i l , and as a r e s u l t oxygen l e v e l s i n Marquette Lake were unexpectedly high. Consequently, no f i s h mortality occurred from oxygen deple-tion. Over-winter f i s h m o r t a l i t i e s were not expected to occur i n Corbett Lake because of the e f f e c t s of experimental c i r c u l a t i o n but probably would not have occurred regardless of t h i s because of the l i g h t snow f a l l . Snow cover e f f e c -t i v e l y reduces the amount of l i g h t that enters the lake. There are s i g n i f i c a n t differences, between win-ters, i n l i g h t transmission through ice and snow cover on Corbett Lake (Fig. 8). In addition to snow cover, cloudy ice also reduces l i g h t transmission but snow cover i s the most important factor (Croxton, et a l . , 1937; Greenbank, 1945; Woods, 1961; Wright, 1964). Reduced l i g h t transmis-sion through snow and ice r e s u l t s i n reduced oxygen of a photosynthetic o r i g i n (Woods, 1961). Supersaturation of oxygen was recorded i n Mar-quette and Courtney Lakes for March 7 and 8, 1963 (Fig. 11) 60 (Increased temperature a t the same r e s p e c t i v e depths was recorded f o r Marquette and Courtney Lakes and to a much l e s s degree f o r C o r b e t t Lake). Greenbank (1945) a l s o recorded under-ice s u p e r s a t u r a t i o n of oxygen that was s i m i l a r l y c o r -r e l a t e d w i t h low snow f a l l and r e l a t i v e l y h i g h l i g h t t r a n s -m i s s i o n . Greenbank (1945) d i d not r e p o r t any p o s i t i v e evidence of the presence of phytoplankton. Wright (1964) recorded maximum numbers of p h y t o p l a n k t e r s i n an i c e covered lake d u r i n g a snow-free p e r i o d . Rhode (1955) s i m i l a r l y shows h i g h e s t numbers of phytoplankton immediately under the i c e where l i g h t i n t e n s i t y was h i g h e s t . A w e l l - d e f i n e d l a y e r of phytoplankton was observed through the use of SCUBA immedi-a t e l y below the i c e and extended to a depth of about 1.5 meters i n Marquette Lake on March 8, 1963. Trout were observed i n t h i s l a y e r of oxygen s u p e r s a t u r a t i o n . The d i f f e r e n c e i n depth d i s t r i b u t i o n of the s u p e r s a t -urated oxygen l a y e r i n Marquette and Courtney Lakes i s probably the r e s u l t of p h o t o s y n t h e t i c i n h i b i t i o n and s e l e c -t i o n of optimum l i g h t i n t e n s i t i e s by p h y t o p l a n k t e r s (Wright, 1964). The s u p e r s a t u r a t i o n of oxygen i s probably a r e s u l t of the phytoplankton l a y e r i n Marquette Lake and a l s o i n Courtney Lake. The l i g h t snow f a l l of 1962-63 r e s u l t i n g i n r e l a t i v e l y h i g h l i g h t p e n e t r a t i o n with the consequent i n c r e a s e i n p h o t o s y n t h e t i c a l l y produced oxygen i s the reason 61 for the prevention of winter mortality of fishes i n Marquette Lake. In at least three other lakes i n south central B.C., that are subject to frequent winter m o r t a l i t i e s of the res-pective f i s h populations, none occurred i n winter of 1962-63. However, i n 1963-64 with greater snow f a l l reports received and some data were c o l l e c t e d that indicated com-plete winter mortality of f i s h populations. WINTER OXYGEN DEMAND The differences i n oxygen consumption or oxygen d e f i c i t between the winters 1961-62, 1962-63 and 1963-64 are evidenced i n the concentration of dissolved oxygen represen-ted by the duration and depth of, and the slope of i n d i v i d u a l oxygen isopleths (Fig. 11). The slopes and depths of oxygen isoplethsO, 2, 4 and 6 mg/1 i n Courtney Lake, for the winters 1961-62, 1962-63 and 1963-64 suggest a rather low oxygen con-sumption rate except that the 0 oxygen isopleth for the win-ter of 1961-62 and 1963-64 i s rapidly established as are 0, 2, 4 and 6 mg/1 isopleths. This suggests an i n i t i a l l y large 02 consumption (usually up to about December 22) and then a f a i r l y stable s i t u a t i o n u n t i l the i c e goes o f f the lake. The winter of 1962-63 follows t h i s general pattern but the i n i t i a l decline of oxygen i s not so rapid and larger quantities of O2 are present due to photosynthetically produced oxygen. In contrast, the slope of the oxygen isopleths for Corbett Lake i n any given winter are much greater than those of Courtney Lake which suggests a greater oxygen consumption for Corbett Lake than that for Courtney Lake. As i n Courtney Lake the i n i t i a l period of greatest oxygen consumption i s between freeze-over and about December 22. The slope of oxygen i s o -pleths 0, 2, 4 and 6 mg/1 for Corbett Lake, for 1963-64 more clo s e l y approximates the slopes of isopleths 0 and 2 mg/1 i s o l i n e s for 1961-62 than those for 1962-63 which i s probably a r e f l e c t i o n of the e f f e c t of greater photosynthesis i n 1962-63 due to a much l i g h t e r snow f a l l . The degree of oxygen depletion i n Marquette Lake i s si m i l a r to that of Corbett Lake but i s somewhat more severe which i s probably due to the poor l i g h t transmitting q u a l i t i e s of Marquette Lake water (Fig. 7). In addition to dissolved oxygen, another environmental parameter i s worth consideration—temperature. Moore (1942), i n a f i e l d study of the summer and winter l e t h a l low-oxygen l e v e l s , found that the oxygen threshhold i s considerably depressed at winter temperatures (about 4-5°C). Si m i l a r l y , Lindeman (1942) found experi-mentally that invertebrate organisms are more r e s i s t e n t to extended anaerobiosis at 0 and 5°C than at 10°C. F i g . 9 shows that i n any winter Corbett Lake i s colder than Court-ney Lake. A r t i f i c i a l c i r c u l a t i o n may well provide a means of building up the oxygen concentration and at the same time lowering the water temperature. Both factors are an obvious advantage to f i s h s u r v i v a l i n i c e covered lakes. 63 EXPERIMENTAL CIRCULATION Experimental c i r c u l a t i o n of Corbett Lake was con-ducted to test the hypothesis that the difference i n s u r v i -v a l of the respective f i s h populations and differences i n physical-chemical c h a r a c t e r i s t i c s between Corbett and Court-ney Lakes and Corbett and Marquette Lakes i s a d i r e c t r e s u l t of the lack of s u f f i c i e n t autumn c i r c u l a t i o n and oxygenation in Corbett Lake. Thus, i f a r t i f i c i a l c i r c u l a t i o n of Cor-bett Lake could b u i l d up a dissolved oxygen reserve s u f f i c i e n t to maintain the f i s h population for the period during which i t would normally be eliminated, the hypothesis would be con-firmed. Marquette and Courtney Lakes serve as experimental controls for the a r t i f i c i a l c i r c u l a t i o n of Corbett Lake. Except for area the morphometric parameters of Marquette Lake are s i m i l a r to those of Corbett Lake and Marquette Lake i s likewise protected from wind action. Consequently i t would be expected that the limnology of Marquette Lake would be affected by climate i n a l i k e manner to that of Corbett Lake. Courtney Lake on the other hand, being well exposed to wind action, would be expected to show limnological differences caused by normal cl i m a t i c e f f e c t s . Thus, the e f f e c t s of experimental c i r c u l a t i o n i n Corbett Lake can be compared to complete, autumn c i r c u l a t i o n i n Courtney Lake and to incom-plete autumnal c i r c u l a t i o n i n Marquette Lake. 64 The method of a r t i f i c i a l c i r c u l a t i o n employed i n this experiment i s not new. Puke (1949), Schmitz and Hasler (1958), Burdick (1959), Schmitz (1959), Foster (1960), Rassmussen (1960), Patriarche (1961), Woods (1961), Carufel (1962) a l l either suggest or report on i t s use and a p p l i -cation. The time of such application i s i n t h i s study, however, unique. In the above c i t a t i o n s the compressed a i r system i s usually employed after the permanent i c e cover has been formed. Consequently, the primary object i n such operations i s to remove the i c e cover so that atmospheric oxygen w i l l be available for solution. The object of the applicationwof the compressed a i r method of a r t i f i c i a l c i r -culation, i n thi s study, was to b u i l d up a reserve of d i s -solved oxygen, before the permanent i c e cover formed, such that the respiratory needs of the f i s h population would be met for the period of ice cover. The d i r e c t comparison of th i s experiment with any other published data i s therefore precluded. Many ef f e c t s of experimental c i r c u l a t i o n by compressed a i r are, however, comparable to t h i s experiment. Fig. 15 shows the re s u l t s of changes i n mean oxygen concentration and increase penetrations of dissolved oxygen, along with the accumulated hours of pumping and the surface water temperature for the respective periods of a r t i f i c i a l c i r c u l a t i o n . One of the i n i t i a l e f f e c t s of experiment c i r c u l a -tion where the a i r outlet pipe(s) i s located i n the 65 hypolimnion i s the sharp depression of the thermocline which i s shown by sharply depressed isotherms. Schmitz and Hasler (1958) and Gilson (1962) note i d e n t i c a l e f f e c t s . Patriarche (1961) showes depressed isotherms for winter a r t i f i c i a l c i r c u l a t i o n . This i s caused by the r i s i n g bubbles l i f t i n g colder water from the hypolimnion to the epilimnion and thus depressing the thermocline u n t i l the lake i s homother-mal. Hooper, B a l l and Tanner (1952) report i d e n t i c a l r e s u l t s using a somewhat d i f f e r e n t method of c i r c u l a t i o n . Fig. 16 shows the change i n mean oxygen concentra-tion immediately after the i n i t i a t i o n of a r t i f i c i a l c i r c u -l a t i o n . The i n i t i a l e f f e c t i s a decrease i n mean oxygen concentration. Patriarche (1961) suggests that the lowered oxygen values immediately following the i n i t i a t i o n of a r t i f i c i a l c i r c u l a t i o n are the r e s u l t of upwelling bottom water that has a high B.O.D. However, Greenbank (1945) found that water samples taken from near the surface of shallow lakes usually had a higher B.O.D. than those taken near the bottom. In addition, Greenbank (1945) comments on the e f f e c t of H2S i n reducing the amount of dissolved oxygen. Simil a r l y , Puke (1949) warns against the danger of a r t i f i -c i a l l y introducing large amounts of H2S into an epilimnion already undersaturated with oxygen. H2S and oxygen are mutually exclusive except i n the absence of heavy metals (Waldichuck, 1964, pers. comm.). In Corbett Lake a very strong odour of &2S was evident immediately at the onset of 66 experimental c i r c u l a t i o n . The H2S odour continued strong u n t i l October 20 (in the 1962-63 experiment) and gradually decreased u n t i l October 23 when i t was no longer detectable. In a l l p r o b a b i l i t y , the considerable amount of H^S i n the epilimnion of Corbett Lake played a s i g n i f i c a n t part i n the i n i t i a l reduction of dissolved oxygen at the onset of experimental c i r c u l a t i o n - - a s i m i l a r trend i n the mean con-centration of dissolved oxygen i s noted for the 1963-64 experiments and i s probably caused by the same events: (1) an introduction of hypolimnion deoxygenated water containing oxidizable organic matter into the oxygenated epilimnion and (2) the introduction of quantities of dissolved H2S into the oxygenated epilimnion. I t i s s i g n i f i c a n t to note (Fig. 12) that the mean concentration of oxygen s t a r t s to make sub-s t a n t i a l increases after October 2 2 — t h e day before H2S odour was l a s t detected—a gradual increase i n mean concen-tr a t i o n of O2 during a r t i f i c i a l c i r c u l a t i o n i s evident after October 23, 1962. A r t i f i c i a l c i r c u l a t i o n was again i n i t i a t e d on Nov-ember 7 - 1 0 and an increase i n mean oxygen concentration was achieved. The lower surface water temperature, plus the fact that the lake, at t h i s point, has a uniform concentra-tion of oxygen, i s s i g n i f i c a n t . From November 10 to Novem-ber 18 the mean concentration of oxygen increased without the assistance of experimental c i r c u l a t i o n . Some natural c i r c u -l a t i o n was obviously taking place and a much lowered surface 67 water temperature assisted the solution of atmospheric oxygen at t h i s time. The rate of solution for this period, judging by the slope of the l i n e (Fig. 12) was not as great as the rate of solution for the f i n a l period of experimental c i r c u l a t i o n — f r o m November 18 to November 26, 1962. The increased rate of solution of oxygen which was r e f l e c t e d i n the increased mean oxygen concentrations for thi s period was probably the e f f e c t of a much lower surface water tem-perature. Experimental c i r c u l a t i o n of Corbett Lake resulted i n a mean concentration of oxygen s u f f i c i e n t l y high to provide for the oxygen requirements of the f i s h population during the winters of 1962-63 and 1963-64. In the winter of 1961-62 the natural autumnal c i r c u l a t i o n resulted i n low oxygen concentrations and consequent complete over-winter mortality of the f i s h population. Snow conditions i n 1961-62 were sim i l a r to those of 1963-64. In the winter of 1963-64 no over-winter mortality of fishes occurred i n the control lake, Courtney (complete natural autumnal c i r c u l a t i o n ) where-as i n the other control lake, Marquette (incomplete natural autumnal c i r c u l a t i o n ) over-winter mortality of the f i s h pop-ulation did occur. Over-winter mortality did not occur i n Corbett Lake because experimental c i r c u l a t i o n provided an oxygen concentration high enough to prevent i t . Thus, the experimental c i r c u l a t i o n of Corbett Lake confirms the o r i g -i n a l hypothesis. 68 SUMMARY 1. A comparison of indices of productivity showed that Courtney Lake i s most productive, that Marquette Lake i s least productive and that Corbett Lake i s intermedi-ate . 2. Measurement of average wind v e l o c i t y and wind d i r e c t i o n showed that Courtney Lake i s subject to 4.3 times as much wind, as i s Corbett Lake and that t h i s wind i s a prev a i l i n g wind whereas the wind acting on Corbett-Lake i s predominantly variable i n d i r e c t i o n . The difference i n wind action on the respective lakes was found to be due to d i f f e r e n t topographical location. 3. Differences i n snow cover during the study winters caused anomalous differences i n dissolved oxygen i n Mar-quette and Courtney Lakes which favourably affected f i s h s u r v i v a l i n 1962-63. 4. The winter oxygen depletion was found to be greatest i n Marquette and Corbett Lakes respectively and least i n Courtney Lake. 5. Experimental autumnal c i r c u l a t i o n of Corbett Lake provided a mean dissolved oxygen concentration s u f f i c i e n t to prevent over-winter mortality of f i s h e s . This a f f i r -med the hypothesis that the differences i n s u r v i v a l of the respective f i s h populations and differences i n 69 physical-chemical c h a r a c t e r i s t i c s between Corbett and Courtney Lakes and Corbett and Marquette Lakes were a di r e c t r e s u l t of the lack of s u f f i c i e n t autumnal c i r c u -l a t i o n and oxygenation i n Corbett Lake. 70 LITERATURE CITED Anderson, G.C. 1958a. Some limnological features of a shal-low saline meromictic lake. Limnol. and Oceanog., 3(3): 259-270. Burdick, M.C. 1959. Open water i n winter. Wise. Cons. B u l l . , 24(2) :21-23. Carufel, L.H. 1962. W i n t e r k i l l research on Lake Upsilon, Gordon Lake and School Section Lake i n Rolette County. North Dakota State Game and Fish Department, Devils Lake, N.D. Proj. F-2-R-8, Job No. 6: 17 pp. Cooper, G.P. and George N. Washburn. 1946. Relation of dissolved oxygen to winter mortality of f i s h i n Michigan lakes. Trans. Amer. Fish. S o c , 76:23-33. Croxton, W.C., W.B. Thurman and Theodore S h i f f e r . 1937. The penetration of l i g h t through snow and ice cover. Minnesota Academy of Science Proc .,£>: 50-53. Eckel, 0. 1950. Concerning the numerical and graphical determination of the s t a b i l i t y of water by W. Schmidt's method. Hydrol., 12:38-46. Faber, Lawrence (Editor). 1960. Standard methods for the examination of water and wastewater. American Public Health Assoc., Inc., N.Y. , N.Y. Foster, D.I. 1960. A summary of Big Lake w i n t e r - k i l l stud-i e s . Arizona Game and Fish Commission, Special Report, 7 pp. Gilson, H.C. 1962. Report of the director. Operation swiz-z l e s t i c k . Freshwater B i o l o g i c a l Association T h i r t i e t h Annual Report, p. 16-17. Greenbank, J.T. 1945. Limnological conditions i n i c e -covered lakes, e s p e c i a l l y as related to w i n t e r - k i l l of f i s h . Ecological Monographs, 15:343-392. Hayes, F.R. and E.H^ Anthony. 1964. Productive capacity of North American lakes as related to the quantity and the trophic l e v e l of f i s h , the lake dimensions, and the water chemistry. Trans. Amer. Fish. S o c , 93 (1) : 53-57. Hooper, F.F., R.C. B a l l and H.A. Tanner. 1952. An experi-ment i n the a r t i f i c i a l c i r c u l a t i o n of a small Michigan lake. Trans. Amer. Fish. S o c , 82:222-241. 71 Humphreys, R.D. 1964. Spatial and temporal d i s t r i b u t i o n of invertebrate organisms inhabiting the Chara zone. M.Sc. Thesis, The University of B r i t i s h Columbia, Van-couver, B r i t i s h Columbia. < Hutchinson, G.E. 1957. A t r e a t i s e on limnology, Vol. I. Geography physics and chemistry. New York, John Wiley and Sons Inc. Kendrew, W.G.and D. Kerr. 1955. The climate of B r i t i s h Columbia and the Yukon Te r r i t o r y . Queen's Printer, Ottawa. Krumholz, L.A. and G.A. Cole. 1959. Some limnological con-di t i o n s during an unusually cold winter. Limnol. and Oceanog., 4(4):367-385. Larkin, P.A. 1964. Canadian Lakes. Verh. Int. Ver. Lim-nol ., 15 : 76-90 . Larkin, P.A. and T.G. Northcote. 1958. Factors i n lake typology i n B r i t i s h Columbia, Canada. Verh. Int. Ver. Limnol., 13:252-263. Lindeman, R.L. 1942. Experimental simulation of winter anaerobiosis i n a senescent lake. Ecology, 23:1-13. Moore, W.G. 1942. F i e l d studies on the oxygen require-ments of certain freshwater fishes. Ecology, 23:319-329. Murphy, G.I. 1962. E f f e c t of mixing depth and t u r b i d i t y on the productivity of fresh-water impoundments. Trans. Amer. Fish. Soc., 93. (1) : 69-76 . Northcote, T.G. and P.A. Larkin. 1956. Indices of produc-t i v i t y i n B r i t i s h Columbia lakes. J. Fish. Res. Bd. Canada, 13(4):515-540. i \0kland, Jan. 1964. The eutrophic lake Borrevan (Norway) -An eco l o g i c a l study on shore and bottom fauna with s p e c i a l reference to gastropods, including a hydro-graphic survey. F o l i a Limnologica Scandinavica> No. 13, p. 49. Patalas, K. 1960a. Stosunki termiczne i tlenowe oraz prezezroczystose wody W44 jeziorach okolic wegorzewa. Rocznihi Nauk Rolniczych Tom 77-B-l:106-217. English summary pp. 217-222. 1960b. Mieszanie wody jako czynnik okreslajacy intensywnosc krazenia materii w roznych morfologicznie jeziorach okolic wegorzewa. Roczniki Nauk Rolniczych Tom 77-B-l:223-240. English summary pp. 240-242. 7 2 P a t r i a r c h e , M.H. 1 9 6 1 . A i r - i n d u c e d w i n t e r c i r c u l a t i o n o f t w o s h a l l o w M i c h i g a n L a k e s . J . o f W i l d l i f e M a n a g e m e n t , 2 5 ( 3 ) : 2 8 2 - 2 8 9 . P u k e , C. 1 9 4 9 . T h e p o s s i b i l i t y o f a v o i d i n g w i n t e r - k i l l o f f i s h . I n s t . F r e s h w a t e r R e s . D r o t t n i n g h o l m , R e p . 3 1 : 1 3 7 -1 4 6 . R a s m u s s e n , D.H. 1 9 6 0 . W i n t e r k i l l p r e v e n t i o n i n S o d a L a k e . W y o m i n g Game a n d F i s h C o m m i s s i o n . P r o j . 1 7 5 8 - 1 - 1 , 5 p p . R a w s o n , D.S. 1 9 3 9 . Some p h y s i c a l a n d c h e m i c a l f a c t o r s i n t h e m e t a b o l i s m o f l a k e s . T h e A m e r i c a n A s s o c i a t i o n f o r t h e A d v a n c e m e n t o f S c i e n c e , N o . 1 0 : 9 - 2 6 . . 1 9 5 2 . M e a n d e p t h a n d f i s h p r o d u c t i o n o f l a r g e l a k e s . E c o l . S o c . A m e r . , 3 3 ( 4 ) : 5 1 3 - 5 2 1 . . 1 9 5 5 . M o r p h o m e t r y a s a d o m i n a n t f a c t o r i n t h e p r o d u c t i v i t y o f l a r g e l a k e s . V e r h . I n t . V e r . L i m n o l . , 1 2 : 1 6 4 - 1 7 5 . - . 1 9 6 1 . A c r i t i c a l a n a l y s i s o f t h e l i m n o l o g i c a l v a r i a b l e s u s e d i n a s s e s s i n g t h e p r o d u c t i v i t y o f n o r t h e r n S a s k a t c h e w a n l a k e s . V e r h . I n t . V e r . L i m n o l . , 1 4 : 1 6 0 - 1 6 6 . R e i d , G.K. 1 9 6 1 . E c o l o g y o f i n l a n d w a t e r s a n d e s t u a r i e s . R e i n h o l d P u b l i s h i n g C o r p o r a t i o n , New Y o r k . R h o d e , W. 1953/. P r o d u c t i v i t y . C a n p l a n k t o n p r o d u c t i o n p r o c e e d d u r i n g w i n t e r d a r k n e s s i n s u b a r c t i c l a k e s ? V e r h . I n t . V e r . L i m n o l . , 1 2 : 1 1 7 - 1 2 2 . S c h m i d t , R . L . a n d J . R . M a r s h a l l . 1 9 6 0 . A w i n d - d i r e c t i o n r e c o r d e r f o r r e m o t e s t a t i o n s . E c o l o g y , 4 1 ( 3 ) : 5 4 1 - 5 4 3 . S c h m i t z , W.R. 1 9 5 9 . R e s e a r c h o n w i n t e r k i l l o f f i s h . W i s e . C o n s . B u l l . , 2 4 ( 2 ) : 1 - 3 . , a n d A r t h u r D. H a s l e r . 1 9 5 8 . A r t i f i c i a l l y i n d u c e d c i r c u l a t i o n o f l a k e s b y m e a n s o f c o m p r e s s e d a i r . S c i e n c e , 1 2 8 : 1 0 8 8 - 1 0 8 9 . T e r a g u c h i , M. 1 9 6 4 . T h e e f f e c t o f a g e a n d e n v i r o n m e n t a l f a c t o r s o n t h e v e r t i c a l m i g r a t i o n a n d d i s t r i b u t i o n o f C h a o b o r u s f l a v i c a n s ( M e i g e n ) l a r v a e . M . S c . T h e s i s . T h e U n i v e r s i t y o f B r i t i s h C o l u m b i a . W e l c h , P . S . 1 9 4 8 . L i m n o l o g i c a l m e t h o d s . T h e B l a k i s t o n C o . . 1 9 5 2 . L i m n o l o g y . M c G r a w - H i l l B o o k C o m p a n y I n c . W o o d s , D.E. 1 9 6 1 . T h e e f f e c t s o f c o m p r e s s e d a i r o n w i n t e r o x y g e n l e v e l s i n a f e r t i l e S o u t h e r n M i n n e s o t a l a k e . M i n n e s o t a F i s h a n d Game I n v e s t i g a t i o n s , No. 3 : 5 1 - 6 8 . 73 Wright, R.T. 1964. Dynamics of a phytoplankton community i n an ice-covered lake. Limnol. and Oceanog., 9(2):163-178. 

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