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The effect of current on natural periphyton communities Oguss, Emily 1973

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THE EFFECT OF CURRENT ON NATURAL PERIPHYTON COMMUNITIES by EMILY OGUSS B.A.. , U n i v e r s i t y of C a l i f o r n i a , San D iego , 1970 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE In the Department of Zoo Iogy We accept t h i s t h e s i s as conforming to the requ i red s tandard THE UN I VERS!TY OF BRITISH COLUMBIA June, 1973 In presenting t h i s thesis i n p a r t i a l f ulfilment of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t freely available for reference and study. I further agree that permission for extensive copying of t h i s thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. I t i s understood that copying or publication of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of Zoology The University of B r i t i s h Columbia Vancouver 8, Canada Date July 12, 1973 Chai rman i i ABSTRACT The e f f e c t of c u r r e n t on loss r a t e s of pe r iphy ton t i s s u e was s t u d i e d in t h r e e d i f f e r e n t f l o w - c o n t r o l l e d streams in B r i t i s h C o l u m b i a . A r t i -f i c i a l s u b s t r a t e s were exposed t o cons tan t c u r r e n t s rang ing from 3 . 0 t o 121.8 c m . / s e c . Indigenous pe r iphy ton s p e c i e s which c o l o n i z e d the s u b -s t r a t e s were labe led wi th i n o r g a n i c P"5"^, and the loss of the label mon i -to red f o r up to 46 days . D a i l y loss r a t e s were c a l c u l a t e d from these d a t a . Graphing the d a i l y loss r a t e s a g a i n s t c u r r e n t s i n d i c a t e d a s igmoid r e l a t i o n s h i p : very l i t t l e e f f e c t of c u r r e n t s less than 20 c m . / s e c ; s h a r p l y i n c r e a s i n g e f f e c t of c u r r e n t s between 20 and 80 c m . / s e c ; and a l e v e l i n g o f f above 80 c m . / s e c . T h i s model f i t s a l l t h r e e streams d e s p i t e t h e i r many d i f f e r e n c e s and i s t h e r e f o r e i n t e r p r e t e d as a general model of c u r r e n t e f f e c t s on pe r iphy ton loss r a t e s in na tu ra l s t reams . The com-ponent of loss due to i n v e r t e b r a t e g r a z i n g i s d i s c u s s e d . A computer s i m u l a t i o n model of pe r iphy ton dynamics was used to com-pare d i f f e r e n t t h e o r i e s about o ther aspects of pe r iphy ton dynamics . Th is model d i f f e r s from p r e v i o u s per iphy ton models in s e v e r a l important ways: (1) up to t h r e e a l g a l s p e c i e s can be handled s e p a r a t e l y , r a t h e r than grouping a l l p e r i p h y t o n i n t o one " q u a s i - o r g a n i s m " , (2) changing co lony morphology was used as a f a c t o r , (3) emphasis was put on the rea l i sm.of each dynamic r e l a t i o n s h i p r a t h e r than on mimick ing t o t a l biomass data from s p e c i f i c s t reams . Three q u e s t i o n s t h a t are p r e s e n t l y unsolved about pe r iphy ton dynamics are examined us ing the computer s i m u l a t i o n program, and t e n t a t i v e answers are a r r i v e d a t . A complete l i s t i n g of the program p l u s the parameter l i s t i s inc luded in the Appendixes . i i i TABLE OF CONTENTS Page LIST OF TABLES iv LIST OF FIGURES v S e c t i o n INTRODUCTION 1 FIELD WORK . . . . 4 Aim 4 Hypotheses and Exper imental Design 4 Choice of Streams 5 Methods . 6 R e s u l t s 12 D i s c u s s i o n 16 SIMULATION MODEL OF PER IPHYTON DYNAMICS 20 D e s c r i p t i o n of the Model 22 Sample Uses of the Computer Model 30 D i s c u s s i o n 42 REFERENCES 45 APPENDIX A L i s t i n g of the Computer Program . . . . . . . 48 APPENDIX B Sample Parameter L i s t 54 LIST OF TABLES Table 1. D i s t i n c t i v e f e a t u r e s of the t h r e e exper imenta l s t reams. V LIST OF FIGURES F igure Page 1. The r e g r e s s i o n of weight l o s t by Wint -O -Green L i f e Saver cand ies at d i f f e r e n t s t r a i g h t - f l o w i n g c u r r e n t s . . . . 7 2 . Photographs of s e t t i l e s a t B i g Qual icum R i v e r a r t i f i c i a l salmon spawning channel 11 3 . Loss of P"^ a c t i v i t y a t seven d i f f e r e n t c u r r e n t s a t B i g Qual icum R i v e r 13 4 . Loss of P"^ a c t i v i t y a t s i x d i f f e r e n t c u r r e n t s a t Fu I ton Ri ver 14 5 . Loss of a c t i v i t y a t f i v e d i f f e r e n t c u r r e n t s a t Loon Lake S p r i n g 15 6 . D a i l y loss r a t e s ( 1 - e ) f o r each c u r r e n t t e s t e d a t the t h r e e streams 17 7. I n t e n s i t i e s of s o l a r i l l u m i n a t i o n d u r i n g d a y l i g h t hours a t d i f f e r e n t t imes of year 25 8 . The e f f e c t of the deciduous canopy on i l l u m i n a t i o n 26 9 . The e f f e c t of water temperature on the r e a l i z e d p r o p o r t i o n of p o t e n t i a l growth r a t e s 28 10. The e f f e c t of c u r r e n t on d a i l y l oss r a t e s 29 11. The e f f e c t of i l l u m i n a t i o n i n t e n s i t y on hour l y growth r a t e s 32 12. Comparison of two growth dynamics 33 13. Comparison of hypotheses on the e f f e c t of i l l u m i n a t i o n on c o l o n i z a t i o n 37 14. Comparison of hypotheses concern ing p e r i p h y t o n loss r a t e s . . 39 15. The e f f e c t of temperature on loss r a t e s 42 INTRODUCTION The g r e a t i n s t a b i l i t y of stream environments has caused l o t i c p e r i -phyton t o evo lve a d a p t i v e s t r a t e g i e s t h a t a re more extreme than those of a l g a e i n h a b i t i n g r e l a t i v e l y s t a b l e water env i ronments . These s t r a t e g i e s i n c l u d e : (1) r e p r o d u c t i v e c e l l s t h a t can w i t h s t a n d very long per iods of un -f a v o u r a b l e c o n d i t i o n s ; (2) h i g h l y s p e c i f i c requirements f o r growth and c o l o n i z a t i o n ( i n c l u d i n g temperature , c u r r e n t , i l l u m i n a t i o n , s u b s t r a t e f e a t u r e s , e t c . , and in some cases i n c l u d i n g the p a t t e r n s of change in these c o n d i t i o n s ; (3) tremendous r a t e s of growth under f a v o u r a b l e c o n d i t i o n s ( r a t e s as high as \2% per hour have been measured (So rok in .and Krauss , 1958) ) . H i g h l y s p e c i f i c requi rements f o r growth make l o t i c per iphy ton more d i f f i c u l t t o study than o t h e r types of a l g a e . Exper iments t h a t measure responses t o c o n d i t i o n s t h a t g r e a t l y exceed the narrow v i a b l e range of the organism are a t best measuring the e f f e c t s of s t r e s s . Yet many e x p e r i -ments have been performed in which pe r iphy ton c o l o n i e s t h a t have developed under one s e t of c o n d i t i o n s are sub jec ted t o a tremendous range of one o r more f a c t o r s , and the r e s u l t s have s t i l l been i n t e r p r e t e d as the normal response of per iphy ton to those c o n d i t i o n s ( see , f o r example, M c l n t i r e , e t  a l , 1964; o r , W h i t f o r d and Schumacher, 1964). In g e n e r a l , much of the research t h a t has been done on l o t i c pe r iphy ton has been poor l y designed because of the tempta t ion t o use the e x c e l l e n t machinery , t e c h n i q u e s , and 1 2 t h e o r e t i c a l models t h a t were designed f o r o t h e r p l a n t s in o t h e r e n v i r o n -ments . Th is study began as an attempt t o s o r t out the rea l b i o l o g i c a l dynamics of pe r iphy ton from the volumes of e x i s t i n g data and t h e o r i e s . The i n i t i a l search led t o the c o n c l u s i o n t h a t the importance of c u r r e n t to l o t i c pe r iphy ton was the f a c t o r t h a t had been l e a s t adequate ly s t u d i e d . In I960, W h i t f o r d determined t h a t a c u r r e n t of 15 c m . / s e c . i s s u f f i c i e n t to a l t e r the d i f f u s i o n g r a d i e n t around an a t tached mass, and he hypothes -ized t h a t s p e c i e s w i th an " i n h e r e n t c u r r e n t demand" a c t u a l l y r e q u i r e t h i s s teeper d i f f u s i o n g r a d i e n t in o rder t o m a i n t a i n high r a t e s of r e s p i r a t i o n . A s e r i e s of exper iments were performed by C. David M c l n t i r e ( M c l n t i r e and Ph inney , 1965; M c l n t i r e , 1966a, 1966b, 1968 ) in which the r e s p i r a t i o n of pe r iphy ton communit ies was measured a t d i f f e r e n t f low r a t e s in l a b o r a t o r y s t r e a m s . In on ly one of these exper iments ( M c l n t i r e , 1968b) was the importance of a c c l i m a t i z a t i o n c o n s i d e r e d , and in t h i s case on ly four c u r r -ents ( 0 , 14, 24 and 38 c m . / s e c . ) were used. Fur thermore , these c u r r e n t s were measured a t the water s u r f a c e , and i t i s d i f f i c u l t t o guess what the c u r r e n t s near the pe r iphy ton s u r f a c e s may have been. The problem of mea-s u r i n g the e f f e c t i v e c u r r e n t a l s o appears in the work of Kevern and B a l l (1965) who c a l c u l a t e d an "average c u r r e n t " based on the t o t a l d i s c h a r g e of t h e i r a r t i f i c i a l s t reams. Kevern and B a l l concluded t h a t c u r r e n t enhances p r o d u c t i v i t y , but they found no p o s i t i v e c o r r e l a t i o n between p r o d u c t i v i t y and s t a n d i n g c r o p . Obv ious l y c u r r e n t a l s o a f f e c t s the r a t e s of t i s s u e loss ( e x p o r t ) . The components of t i s s u e loss r a t e s a re s c o u r , s l o u g h i n g , and h e r -b i v o r e g r a z i n g . The s i z e and shape of the s u b s t r a t e t o which the 3 p e r i p h y t o n i s a t tached ( i . e . i t s tendency t o r o l l ) and the average s u b -s t r a t e s i z e in the stream ( i . e . the l i k e l i h o o d t h a t the co lony w i l l be h i t by a r o l l i n g stone) are f a c t o r s a f f e c t i n g s c o u r . The age, s i z e and shape of the c o l o n i e s and a l s o the frequency of spates are f a c t o r s a f f e c t i n g s l o u g h i n g . Food p re fe rences and p o p u l a t i o n s i z e of h e r b i v o r e s are f a c t o r s a f f e c t i n g g r a z i n g . The v a r i a b i l i t y of the c u r r e n t i s a f a c t o r i t s e l f — high t u r b u l e n c e and spates are common in na tu ra l s t r e a m s . The work of M c l n t i r e o u t l i n e d how expor t r a t e s change when p e r i p h y t o n grown a t one c u r r e n t i s exposed t o sudden changes. The exper iments d e s c r i b e d in t h i s t h e s i s were designed t o measure the normal r a t e s of expor t of n a t u r a l l y o c c u r r i n g pe r iphy ton communit ies a t the c u r r e n t s to which they are a c c l i -mati zed . In a d d i t i o n to l e a r n i n g the dynamics of e x p o r t , i t i s i n t e r e s t i n g t o see how i t f i t s i n t o the t o t a l p i c t u r e of pe r iphy ton growth . A com-prehens ive framework was needed, in which the r e l a t i v e importance of each f a c t o r and response cou ld be e v a l u a t e d . S i m u l a t i o n models of p e r i p h y t o n growth have been produced ( M c l n t i r e , 1973; F i s h e r and L i k e n s , 1972; and Bloom e t a l , 1969) but they a re s e r i o u s l y f lawed by making i n a p p r o p r i a t e assumpt ions , such a s : a stream is l i k e a moving l a k e , a st ream is a s e l f -conta ined ecosystem, m e t a b o l i c r a t e s of one pe r iphy ton community under s t r e s s c o n d i t i o n s are the same as those of a community a c c l i m a t i z e d t o those c o n d i t i o n s , and , any mathematical equat ions are a c c e p t a b l e i f the r e s u l t s r e p l i c a t e numerical data from a s p e c i f i c l o c a t i o n . A major goal of t h i s study was to b u i l d a s i m u l a t i o n model which would be based on the i n s t a b l e , n o n - r e t e n t i v e nature of the st ream environment and which would p l a c e pr imary emphasis on the a d a p t i v e s t r a t e g y of p e r i p h y t o n as a means 4 of u n i f y i n g the knowledge about the dynamics of pe r iphy ton growth in s t reams . FIELD WORK Aim The o r i g i n a l aim of the study was t o measure the e f f e c t s of c u r r e n t on the growth, death and expor t r a t e s o f n a t u r a l l y o c c u r r i n g pe r iphy ton communi t ies . A f l o w - t h r o u g h r e s p i r a t i o n chamber was b u i l t in o r d e r to measure m e t a b o l i c r a t e s . However the chamber c o u l d not be made to work adequate ly under f i e l d c o n d i t i o n s ; i t s pump caused water temperature i n -c reases up t o I4°C per hour . There fo re the f i e l d work was l i m i t e d to measurements of expor t — i . e . the r a t e a t which l i v i n g and dead p e r i -phyton t i s s u e i s removed by s l o u g h i n g , scour and g r a z i n g a t d i f f e r e n t c u r r e n t r a t e s . Hypotheses and Exper imenta l Design (1) The r a t e of expor t ( s l o u g h i n g , scour and g r a z i n g ) in n a t u r a l l y o c c u r r i n g p e r i p h y t o n communit ies i s a f u n c t i o n of the mean c u r r e n t . (2) T h i s f u n c t i o n ( the e f f e c t of mean c u r r e n t on expor t r a t e s ) i s general t o a c c l i m a t e d per iphy ton communities t h a t are found in w i d e l y d i f f e r i n g s t reams. In o r d e r to t e s t the f i r s t h y p o t h e s i s , i t i s necessary t o measure the r a t e s of expor t a t d i f f e r e n t c u r r e n t r a t e s in a s t r e a m , h o l d i n g a l l o t h e r f a c t o r s equal ( i t i s i m p o s s i b l e t o keep a l l o t h e r f a c t o r s cons tan t in a na tu ra l s t r e a m ) . Th is was done by s e l e c t i n g c l o s e l y spaced s i t e s between which the c u r r e n t s d i f f e r e d due to the shape of the stream bed. Streams in which the d i s c h a r g e is a r t i f i c i a l l y mainta ined were chosen so t h a t the c u r r e n t s a t each s i t e would be r e l a t i v e l y steady and a l s o t o avo id spate c o n d i t i o n s . The n u t r i e n t s in the w a t e r , exposure t o sun , depth , water temperature , e t c . , were very s i m i l a r o r i d e n t i c a l a t a l l s i t e s w i t h -in the s t r e a m . To t e s t the second h y p o t h e s i s , the exper iment was repeated in two o t h e r s t reams , the t h r e e streams being chosen so as t o be as d i f f e r e n t as p o s s i b l e in B r i t i s h Co lumbia . A f t e r r a t e s o f expor t had been measured a t d i f f e r e n t c u r r e n t s in each of the t h r e e s t r e a m s , a f u n c t i o n t o d e s c r i b e the e f f e c t of c u r r e n t on expor t was chosen on the b a s i s of the elements common t o the t h r e e s t reams . Choice of Streams Constant f low r a t e s d u r i n g the course of the exper iment were necessary in o rder to e s t a b l i s h the e f f e c t s of a r e l a t i v e l y s t a b l e c u r r e n t as d i s t i n c t from the e f f e c t s of spates and f l u c t u a t i n g c u r r e n t s . T h i s requirement l i m i t e d the c h o i c e of streams t o n a t u r a l s p r i n g s and a r t i f i c -i a l spawning c h a n n e l s . Streams were chosen in t h r e e d i f f e r e n t g e o g r a p h i -c a l a reas of B r i t i s h Co lumbia : (1) Spawning channel #2 a t the B i g Qualicum R i v e r Salmon Deve lop -ment P r o j e c t on Vancouver I s l a n d . (2) Spawning channel #2 a t the Babine Lake Salmon Development P r o -j e c t on the Fu l ton R i v e r , in the nor thern i n t e r i o r . 6 (3) The n a t u r a l s p r i n g used to f i l l the B. C. F i s h and W i l d l i f e t r o u t h o l d i n g ponds a t the Loon Lake p r o j e c t in the i n t e r i o r dry b e l t . The two salmon spawning channels were both twenty f e e t w ide , un -shaded, and s u p p l i e d w i t h water drawn from l a k e s ; they d i f f e r p r i m a r i l y in e l e v a t i o n and temperature regime. The s p r i n g a t Loon Lake has an average width of o n l y I f o o t , and the on ly impoundment above the study s i t e i s very s m a l l ; the e n t i r e course of the stream was shaded by a c a n -opy of a l d e r and mixed c o n i f e r d u r i n g the course of the exper iments . The d i s t i n c t i v e f e a t u r e s of each stream are summarized in Table I. Methods ( I ) Measurement of c u r r e n t . McConnell and S i g l e r (1959) o r i g i n -a l l y proposed the use of d i s s o l v i n g s a l t t a b l e t s t o measure c u r r e n t s in smal l t u r b u l e n t a r e a s . I have found t h a t L i f e Saver cand ies g i ve s u p e r i o r r e s u l t s because: (a) the ho le a l l o w s them to be he ld s e c u r e l y w i thout a p -p l y i n g p ressure t o the t a b l e t i t s e l f ; (b) sucrose does not d i s s o l v e as r a p i d l y as s a l t , a l l o w i n g a longer immersion t i m e ; (c) t h e i r packaging o f f e r s p r o t e c t i o n a g a i n s t dampness and damage; (d) they are u b i q u i t o u s l y a v a i l a b l e and cheap. The r e g r e s s i o n of weight l o s t by Wint -O -Green L i f e Savers a t d i f f e r e n t s t r a i g h t - f l o w i n g c u r r e n t s was measured us ing a la rge flume and an O t t meter . T a b l e t s were immersed f o r 60 seconds . ( F igure I) Comparison w i t h s a l t t a b l e t s t e s t e d a t the same t ime showed the d i s s o l v i n g of L i f e Savers to be s i g n i f i c a n t l y (p< .025) more un i fo rm than t h a t of s a l t t a b l e t s . Es t imates of c u r r e n t in the f i e l d were made by averag ing the weight l o s t by four L i f e Savers and a p p l y i n g i t in the f o l l o w i n g e q u a t i o n : .7 . 5 -.3-.1 •• • I 30 60 90 120 Current (cm./ sec.) Fi gure 1 The reg ress ion c f weight l o s t by Wint -O-Green L i f e d i f f e r e n t s t r a i g h t - f l o w i n g c u r r e n t s . Candies were f o r c e p s . Water temperature 12°C. Saver cand i es a t held wi th a curved TABLE 1 D i s t i n c t i v e f e a t u r e s of the th ree exper imental s t r e a m s . Chemical and pH ana lyses are the average of two samples taken a t the s t a r t of the P^3 s a m p l i n g . Measurements were made w i t h a Hach k i t . Feature Qua 1i cum Fu1 ton Loon E l e v a t i o n 100 f t . 2400 f t . 3300 f t . Sun or Shade sun sun shade S u b s t r a t e gravel on mud (man-made channe1) gravel on c o n c r e t e (man-made channel ) mud and g rave l (naturaI channeI) pH 7.0 6 . 9 7 . 2 Tota l N i t rogen 15ppm 13.2ppm 5ppm Tota l Phosphorus 10ppm 15ppm 2ppm Iron Ions .05mg./1 . 3 5 m g . / 1 . (not measured) Dominant a l g a l genera Thorea (red) (35 t o 45 c m . / s e c . ) Bumi I l e r i a (yeI low-green) (•v 80 c m . / s e c . ) U l o t h r i x (green) (~ 80 c m . / s e c . ) Hydrurus (golden) (20 to 40 c m . / s e c . ) Lemanea (red) (<~ 80 c m . / s e c . ) Gomphonema (diatom) (25 to 40 c m . / s e c . ) Date of f i e l d study March-May, 1972 M a y - J u l y , I972 J u l y - S e p t e m b e r , I972 9 (Sokal and R o h l f , 1969) X = Y - a b . y x where: X c u r r e n t ( s t r a i g h t f low e q u i v a l e n t ) Y average weight l o s t by four t a b l e t s a the y - i n t e r c e p t of the r e g r e s s i o n e q u a t i o n b = the r e g r e s s i o n c o e f f i c i e n t y x (The use of t h i s equat ion compensates f o r the s t a t i s t i c a l problems i n v o l -ved in e s t i m a t i n g a va lue of x from a r e g r e s s i o n of y on x . ) f low a c r o s s the s u r f a c e , a un i form a r t i f i c i a l s u b s t r a t e was chosen . S i x -inch wh i te ceramic f l a t t i l e s were used. A smal l h o l e was d r i l l e d in two co rners of each t i l e so t h a t they c o u l d be anchored w i t h t e n t pegs in f a s t c u r r e n t a r e a s . (3) Measurement of expor t r a t e s . Rates of e x p o r t of p e r i p h y t o n t i s s u e were measured by l a b e l l i n g the c o l o n i e s w i t h P"^ and then r e c o r d i n g the loss of the r a d i o a c t i v e label over s e v e r a l months. My c h o i c e of phosphorous was based on the work of B a l l and Hooper (1959 and 1964) who 32 d i s c o v e r e d t h a t i n o r g a n i c P i s very e f f i c i e n t l y i n c o r p o r a t e d by st ream per iphy ton and i s q u i c k l y d i s t r i b u t e d throughout the l i v i n g t i s s u e of the a lgae ( r a t h e r than j u s t the growing t i p s ) , and main ta ined by them f o r more than t h r e e months w i t h o u t s i g n i f i c a n t losses v i a d i f f u s i o n . The t e n a c i t y of the pe r iphy ton is perhaps e x p l a i n e d by the f a c t t h a t phosphate i s commonly the l i m i t i n g f a c t o r in per iphy ton growth in streams (Stewart and (2) S u b s t r a t e . S i n c e the s i z e and shape of s u b s t r a t e i n f l u e n c e s 10 A l e x a n d e r , 1971). B a l l and Hooper concluded t h a t the on ly s i g n i f i c a n t 32 loss of the P l a b e l , a f t e r a p e r i o d of wash ing , i s due to the p h y s i c a l removal of pe r iphy ton t i s s u e . The use of the r a d i o a c t i v e label r e q u i r e s a w a i t i n g p e r i o d a f t e r l a b e l i n g dur ing which the excess labe l t h a t has adhered to p l a n t and s u b -s t r a t e s u r f a c e s can be washed away o r absorbed by the p e r i p h y t o n . B a l l and Hooper found t h a t t h r e e t o four weeks were r e q u i r e d f o r t h i s washing 32 t o t a k e p l a c e . Because the h a l f - l i f e of P i s 14.3 days , I dec ided t h a t P"^ w i t h a ha I f - l i f e of 25 days would be a b e t t e r i so tope f o r t h i s exper iment . (4) Sequence of e v e n t s . An Ot t meter was used t o i d e n t i f y s i t e s in each stream wi th r e l a t i v e l y un i fo rm f low over an area la rge enough to accommodate seven t i l e s and t o measure the range of c u r r e n t s a v a i l a b l e so t h a t the bes t d i s t r i b u t i o n of s i t e s cou ld be made. F i v e to seven s i t e s were chosen a t each s t r e a m . Photographs of some s e t t i l e s are in F igu re 2 . Once the t i l e s were in p l a c e , the c u r r e n t s 5mm over t h e i r s u r f a c e s were measured us ing the more a c c u r a t e L i f e Saver t e c h n i q u e . The t i l e s were c o l o n i z e d by indigenous pe r iphy ton over a p e r i o d of a t l e a s t two months. Once the c o l o n i e s were w e l l - e s t a b l i s h e d , two t i l e s from each group were removed from the s t r e a m , exposed t o P ^ f o r h a l f an hour , and r e p l a c e d . The L i f e Saver techn ique was used t o v e r i f y t h a t the labe led t i l e s were p o s i t i o n e d so as to have the same c u r r e n t s as b e f o r e . Washing of the labe l was a l lowed t o t a k e p l a c e f o r t h r e e o r four weeks. Then a 2 . 5 s q . cm. s e c t i o n of each labe led t i l e and of two c o n t r o l t i l e s was scraped c l e a n , and the removed p e r i p h y t o n d r i e d a t 80°C. f o r twe lve 11 F i g u r e 2 Photographs of s e t t i l e s a t B i g Qualicum R i v e r a r t i f i c i a l salmon spawning c h a n n e l . Groups of seven t i l e s each were p laced so t h a t each t i l e in the group had approx imate ly the same c u r r e n t over i t s s u r f a c e . 12 hours . Sampling was repeated every two or t h r e e days f o r a t l e a s t 18 days . The remaining t h r e e t i l e s from each group were used to p rov ide ma-t e r i a l f o r taxonomic study and e s t i m a t e s of t o t a l b iomass. A record of the appearance of a l l t i l e s ( d e n s i t i e s and types of c o l o n i e s ) was kept d u r i n g the exper imenta l p e r i o d . P 3 3 a c t i v i t y was counted by l i q u i d s c i n t i l l a t i o n . The d r i e d a lgae samples were weighed, d i s s o l v e d in P r o t o s o l , and suspended in a s c i n t i l l a -t i o n " c o c k t a i l " c o n t a i n i n g 6 g . PPO and 75mg. POPOP per i i t e r of t o l u e n e . The s c i n t i l l a t i o n counter used was an l socap -300 by Nuc lear C h i c a g o . R e s u I t s . Measurements of P 3 3 loss r a t e s ( c o r r e c t e d f o r r a d i o a c t i v e decay) i n d i c a t e t h a t some washing of excess label was s t i l l o c c u r r i n g a t the s t a r t of the sampl ing p e r i o d a t each s t r e a m . There fo re the loss r a t e s d i s c u s s e d in the r e s t of t h i s t h e s i s have been c a l c u l a t e d from on ly the l a s t week's samples . F igu res 3 , 4 and 5 show the P 3 3 a c t i v i t i e s a t each s i t e f o r each st ream d u r i n g the sampl ing p e r i o d . The important f e a t u r e to note on these graphs i s not the a b s o l u t e v a l u e s of r a d i o a c t i v i t y but r a t h e r the r a t e s a t v.'hich the labe l i s being l o s t in the f i n a l 6 o r 7 days . If the r a t e a t which p e r i p h y t o n t i s s u e i s l o s t i s a c o n s t a n t , one would expect P 3 3 a c t i v i t y t o decrease a c c o r d i n g t o a n a t u r a l decay (expo-n e n t i a I ) f u n c t i o n : ^ — = k ( P 3 3 - C) ; k < 0 dt •where: P 3 3 = P 3 3 a c t i v i t y , c o r r e c t e d f o r r a d i o a c t i v e decay 13 FIGURE 3 Loss of P a c t i v i t y a t seven d i f f e r e n t c u r r e n t s a t B i a Q u a l i c u m R i v e r . Each l i n e i s l a b e l e d w i t h the c u r r e n t a t the c o r r e s p o n d i n g s i t e . 14 FIGURE 4 Loss of P a c t i v i t y at six di f f e r e n t currents at Fulton River. Each line is labeled with the current at the corresponding s i t e . 15 16 C = background leve l of P 3 " 5 a c t i v i t y k 33 k = a c o n s t a n t such t h a t (1 - e ) = the p r o p o r t i o n of P a c t i v i t y l o s t per day. Us ing t h i s e q u a t i o n , d a i l y loss r a t e s (1 - e ) were est imated f o r each c u r r e n t a t each s t r e a m . The combined r e s u l t s a re summarized in F i g u r e 6 . The shape of the curve i s c l e a r l y s i g m o i d , i n d i c a t i n g t h a t some c o n s t r a i n t s ( t h r e s h o l d s ) are important t o the r e l a t i o n s h i p between c o l o n -ies of pe r iphy ton and the c o n s t a n t c u r r e n t to which they are a c c l i m a t e d . These t h r e s h o l d s a r e : (a) 15 t o 20 c m . / s e c ; below t h i s c u r r e n t the r a t e s of loss do not appear t o d e c r e a s e . (b) 50 t o 60 c m . / s e c ; the i n f l e c t i o n p o i n t of the curve ( impor -tance d i s c u s s e d be low) . (c) 50$ loss r a t e per day; the approximate maximum s u s t a i n a b l e loss f o r a c c l i m a t i z e d pe r iphy ton c o l o n i e s . D i s c u s s i o n . L .A. W h i t f o r d (1960) demonstrated t h a t a c u r r e n t of a p p r o x i -mately 15 c m . / s e c i s r e q u i r e d in o r d e r to decrease the d i f f u s i o n g r a d i e n t around an a t tached c e l l . Approx imate ly the same t h r e s h o l d i s i n d i c a t e d in F igu re 6 f o r the e f f e c t of c u r r e n t on loss r a t e s . The loss r a t e below t h i s t h r e s h o l d i s due t o f a c t o r s o t h e r than c u r r e n t . The maximum d a i l y loss r a t e t h a t i s i n d i c a t e d by the graph i s .50 ( i . e . 50% per d a y ) . Th is may seem i m p o s s i b l y l a r g e , but i t i s reasonab le when compared t o the tremendous growth p o t e n t i a l s of some per iphy ton under f a v o u r a b l e c o n d i t i o n s . S o r o k i n and Krauss (1958) repor ted growth r a t e s } 0 0 t t t V Qualicum O Fulton • Loon -+- •+-2 0 4 0 6 0 8 0 100 120 Current (cm./sec.) FIGURE 6 D a i l y loss ra tes (1 -e ) f o r each c u r r e n t t e s t e d a t the t h r e e s t reams, 18 as high as 3 . 8 d o u b l i n g s (of biomass) in a 24 hour p e r i o d , which i s e q u i -v a l e n t t o 12$ i n c r e a s e per hour . At such a r a t e , on l y 4 hours of f a v o u r -a b l e c o n d i t i o n s per day would be s u f f i c i e n t f o r a per iphy ton co lony to s u s t a i n a d a i l y l oss of .50 and s t i l l i nc rease i t s biomass s l i g h t l y . In f a c t , i t i s p o s s i b l e t h a t under l a b o r a t o r y c o n d i t i o n s even h igher d a i l y loss r a t e s might be measured. In n a t u r a l s t reams , however, a t a s i t e w i t h such h igh f low r a t e s ( > 120 c m . / s e c . ) the p a t t e r n of t u r b u l e n t c u r r e n t s is so u n s t a b l e t h a t i t cannot be cons ide red a c o n s t a n t f l o w . The i n f l e c t i o n p o i n t of the curve in F i g u r e 6 o c c u r s between 50 and 60 c m . / s e c . In the t h r e e streams s t u d i e d , t h i s c u r r e n t range a l s o d i v i d e d the two dominant pe r iphy ton s p e c i e s . F requent l y one s p e c i e s would be abundant in s i t e s w i th c u r r e n t s between 20 and 40 c m . / s e c , w h i l e a d i f f e r e n t s p e c i e s would be dominant in c u r r e n t s between 80 and 100 c m . / s e c . The dominant a l g a of the f a s t e r c u r r e n t areas was g e n e r a l l y c h a r a c t e r i z e d by long f i l a m e n t s a t tached t o a narrow base , w h i l e the dominant a l g a of the s lower c u r r e n t areas had a more compact and s p r e a d i n g growth h a b i t . (The s p e c i e s r e f e r r e d t o a re l i s t e d in Tab le I a long w i th t h e i r " p r e f e r -red" c u r r e n t s . ) In f a c t , t h i s dichotomy i s one reason t h a t t h e r e i s r e l a t i v e l y l i t t l e data in the 40 to 80 c m . / s e c . c u r r e n t range: t i l e s e x -posed t o these c u r r e n t s were not h e a v i l y enough c o l o n i z e d t o p r o v i d e a d e -quate samples , and were not used . I t would seem t h a t the i n f l e c t i o n p o i n t in F i g u r e 6 i n d i c a t e s some c u r r e n t - r e l a t e d f a c t o r t h a t i s of impor -tance t o p e r i p h y t o n . U n f o r t u n a t e l y the data c o l l e c t e d in these e x p e r i -ments cannot c l e a r l y d e f i n e what t h a t f a c t o r may be . No at tempt was made t o p r o t e c t the exper imenta l pe r iphy ton from g r a z e r s , so i t i s n a t u r a l l y of i n t e r e s t t o at tempt t o separa te the e f f e c t 19 of g r a z i n g from the e f f e c t of c u r r e n t a l o n e . The types and abundance of h e r b i v o r e s d i f f e r e d g r e a t l y between the s t reams: F u l t o n had o n l y the s m a l l e s t of ( u n i d e n t i f i e d ) midge and s t o n e f l y l a r v a e , and these were not abundant, w h i l e Qual icum had d e n s i t i e s as g r e a t as 500 smal l la rvae per square f o o t in some p l a c e s and a l s o had some very la rge h e r b i v o r e s ( s n a i l s and large f l y l a r v a e ) . However the d a i l y l oss r a t e s a t the two streams do not appear t o be d i f f e r e n t . Th is lack of a d i f f e r e n c e due t o d i f f e r -ent h e r b i v o r e l e v e l s can be a t t r i b u t e d to t h r e e f a c t o r s : (a) C u r r e n t s and the s i z e and d r i f t r a t e s of h e r b i v o r e s a re not independent f a c t o r s . There i s probably a n e g a t i v e c o r r e l a t i o n between the s i z e of h e r b i v o r e s and the c u r r e n t s a t which they g r a z e . If t h i s i s the c a s e , t h i s r e l a t i o n s h i p would e x e r t a s i m i l a r e f f e c t in a l l s t reams . (b) Not a l l h e r b i v o r e s are g r a z e r s . Many of the he rb i vo rous i n v e r t e b r a t e s of streams are f i l t e r f e e d e r s , s u b s i s t i n g p r i m a r i l y on a I lochthonous d e t r i t u s and on pe r iphy ton t h a t has a l r e a d y been detached due t o s l o u g h i n g o r scour (Hynes, 1970). (c) The amount eaten by g r a z e r s i s very smal l in comparison t o the d a i l y loss and growth r a t e s of the p e r i p h y t o n . A sample c a l c u l a t i o n of growth r a t e s and g r a z i n g shows how t h i s o c c u r s . T i l e #63 (a c o n t r o l t i l e ) a t Qual icum supported la rge numbers of i n v e r t e b r a t e s d u r i n g the exper iment -a l p e r i o d . At the end of the exper iment t h i s t i l e was removed from the s t r e a m , scraped c l e a n , and i n v e r t e b r a t e s were separated from the a l g a e . The dry weight (80°C. f o r 24 hours) of the a lgae was .94 g . The 167 macroscopic i n v e r t e b r a t e s on the t i l e had a combined dry weight of .010 g . S i n c e the biomass of a l g a e d i d not change n o t i c e a b l y (based on v i s u a l appearance) d u r i n g the exper imenta l p e r i o d , i t can be assumed t h a t the 20 d a i l y growth r a t e was approx imate ly equal t o the d a i l y loss r a t e of .40 per day, o r .38 g . Research d i s c u s s e d by Hynes (1970) i n d i c a t e s t h a t on ly approx imate l y one t h i r d (by weight) of stream i n v e r t e b r a t e s are g r a -z e r s . Assuming t h a t these g r a z e r s eat t h e i r weight in a lgae each day , t h e i r consumption was approx imate ly .033 g . , o r l ess than one tenth of the d a i l y a l g a l loss r a t e . N e a r l y a l l of the t i l e s in these exper iments had fewer i n v e r t e b r a t e s than t i l e #63, so t h i s i s a c o n s e r v a t i v e c a l c u l a -t i o n . I t would appear t h a t the amount of pe r iphy ton eaten by g r a z e r s i s of much more importance in p r e d i c t i n g h e r b i v o r e growth than in p r e d i c t i n g per iphy ton l o s s e s . SIMULATION MODEL OF PERIPHYTON DYNAMICS Aim An environment t h a t i s p e r f e c t l y s t a b l e y i e l d s no i n f o r m a t i o n about how i t s components would r e a c t t o change — i t s dynamics are c o n -c e a l e d s i n c e any e q u i l i b r i u m s t a t e can have been produced by an i n f i n i t e number of d i f f e r e n t dynamic paths and i n t e r a c t i o n s . The re fo re s t u d i e s of dynamics must be performed on environments t h a t are n a t u r a l l y u n s t a b l e o r ones t h a t can be d i s t u r b e d . In temperate c l i m a t e s , n a t u r a l streams are the most i n s t a b l e envi ronment : changes in d i s c h a r g e , temperature and n u t r i e n t l e v e l s can occur hour by hour . Small changes in a watershed are magn i f i ed in i t s stream because t h e r e i s l i t t l e b u f f e r i n g ; the f l o w i n g water J_s_ the env i ronment , and i t i s c o n s t a n t l y being r e p l a c e d . One would t h i n k , t h e n , t h a t the dynamics of stream organisms would be the most e a s i l y 21 s t u d i e d , and would by now be c l e a r l y d e f i n e d . U n f o r t u n a t e l y t h i s is not the c a s e . There are s e v e r a l reasons : (1) Streams are not ecosystems in the s t r i c t e s t s e n s e , i . e . s e l f -conta ined u n i t s in which the major energy source i s the sun and in which important r e c y c l i n g can o c c u r . Much of the i n t e r e s t in dynamics has been focused on ecosystems, and thus r e l a t i v e l y l i t t l e a t t e n t i o n has been g iven t o the st ream env i ronment . (2) Changes can occur so f r e q u e n t l y t h a t o b t a i n i n g adequate sam-p l e s i s di f f i c u l t . (3) Organisms t h a t r e q u i r e a c u r r e n t cannot g e n e r a l l y be s t u d i e d wi th the techn iques and machinery designed f o r o t h e r k inds of o rgan isms. S p e c i a l equipment and techn iques a re s t i l l be ing deve loped . (4) The usual approach t o s t u d y i n g the dynamics of a t tached a lgae has been to c o n s i d e r i t a " q u a s i - o r g a n i s m " ( e . g . M c l n t i r e , 1973; Bloom et a l , 1969) w i th one s e t of responses to changing c o n d i t i o n s . T h i s s o r t of s i m p l i f i c a t i o n i s very common in s i m u l a t i o n models and i s a p p r o p r i a t e when the purpose of the model i s t o p r e d i c t s t a n d i n g c r o p s . But i t cannot r e s o l v e q u e s t i o n s about the changes in s p e c i e s dominance o r d i s t r i b u t i o n t h a t occur so f r e q u e n t l y , and t h a t r e f l e c t the very s e n s i t i v e responses of pe r iphy ton to t h e i r changing env i ronment . I became i n t e r e s t e d in s e e i n g i f a computer s i m u l a t i o n model cou ld be used t o compare d i f f e r e n t t h e o r i e s about pe r iphy ton dynamics in the s e t -t i n g of an i n s t a b l e stream env i ronment . The best t h e o r i e s cou ld be i d e n -t i f i e d by comparing the output of the model w i th the known n a t u r a l o c c u r -rence of p e r i p h y t o n . Th is e x e r c i s e r e q u i r e d a k ind of pe r iphy ton s i m u -l a t i o n model d i f f e r e n t from any t h a t had been produced b e f o r e . I t had t o 22 be a b l e t o s i m u l a t e many d i f f e r e n t s o r t s of s t r e a m s , w i th d i f f e r e n t temper -a t u r e regimes and v a r i a t i o n s in d i s c h a r g e . The pe r iphy ton dynamics had to be in a form t h a t cou ld r e a d i l y be changed, so as t o accommodate the wide range of phys io logy in st ream a l g a e . And s i n c e i t i s obv ious t h a t the shape and s i z e of pe r iphy ton c o l o n i e s i s sometimes c r i t i c a l in d e t e r m i n i n g dynamics, p r o v i s i o n had t o be made f o r c o n s i d e r i n g the e f f e c t s of morpho l -ogy . The d e s c r i p t i o n of the model e x p l a i n s how these s p e c i f i c a t i o n s were met. D e s c r i p t i o n of the Model . ( I ) General s t r u c t u r e . The model i s w r i t t e n in FORTRAN IV and was run on an I .B .M . 3 6 0 - 6 7 . A m a i n l i n e program reads in parameter v a l u e s , takes c a r e of bookkeeping , and w r i t e s the output on f i l e s . The s i m u l a t i o n g e n e r a l l y i s run f o r 365 days , s t a r t i n g w i t h January I. For each "day" a s u b r o u t i n e PHYS i s c a l l e d , which generates the c o n d i t i o n s of water tem-p e r a t u r e , mid-day i l l u m i n a t i o n , d i s c h a r g e and n u t r i e n t l e v e l s . In o rder t o make the p h y s i c a l c o n d i t i o n s f l e x i b l e , PHYS uses parameters t h a t can be changed w i thout r e c o m p i l i n g the program. A f t e r c a l l i n g PHYS, the m a i n -l i n e program c a l l s ALGA, which i s the s u b r o u t i n e t h a t c a l c u l a t e s the s u c -cess of c o l o n i z a t i o n , growth and losses f o r each type of a l g a e . Some changes in pe r iphy ton dynamics can be made v i a the parameter l i s t , so t h a t r e c o m p i I a t i o n of the program is unnecessary . Changes t h a t r e q u i r e new programming can be made in the s u b r o u t i n e ALGA, which can then be s e p a r a t e -ly recompi led and the whole program rerun q u i c k l y . The e n t i r e program in i t s f i n a l fo rm, p lus a sample parameter l i s t , i s l i s t e d in the Append ices . A more d e t a i l e d d e s c r i p t i o n of the s u b r o u t i n e s PHYS and ALGA i s g iven 23 below. (2) P h y s i c a l C o n d i t i o n s . C e r t a i n f e a t u r e s of a watershed t h a t i n f l u e n c e the p h y s i c a l c o n d i t i o n s in i t s stream are read in from the p a r a -meter l i s t . The s u b r o u t i n e PHYS generates a d a i l y a i r tempera tu re , ARTM, as a s i n e f u n c t i o n which v a r i e s from the s p e c i f i e d minimum, TMMN, to the s p e c i f i e d maximum, TMMX. ( S o l s t i c e s are on December 21 and June 2 1 . ) A random number between +5 and - 5 i s added t o the a i r temperature to g i v e v a r i a t i o n t o the sequence. On the c o o l e r days ( i . e . when the random number i s l ess than 0) p r e c i p i t a t i o n may o c c u r . The amount of p r e c i p i t a -t i o n i s c a l c u l a t e d so t h a t the y e a r ' s t o t a l w i l l approx imate a s p e c i f i e d average annual r a i n f a l l , APPT. A r a i n f a l l p a t t e r n can be mimicked by a s s i g n i n g p r o p o r t i o n s (RFP) of the annual r a i n f a l l t o each of the four seasons . When the a i r temperature i s l ess than 0 ° C . , p r e c i p i t a t i o n i s added t o the snow pack. If the a i r temperature i s g r e a t e r than 0 ° C . , the p r e c i p i t a t i o n c o n t r i b u t e s t o the st ream d i s c h a r g e . To ta l stream d i s -charge i s c a l c u l a t e d by adding groundwater (a s p e c i f i e d cons tant , (GRND) , p r e c i p i t a t i o n and snow m e l t . The temperature of the water i s c a l c u l a t e d as a weighted average of the ground water temperature (GTEM), snowmelt (at 0 . 5 ° C ) , and p r e c i p i t a t i o n (whose temperature i s a f u n c t i o n of the a i r temperature and AMPW). C u r r e n t (5mm above the s u b s t r a t e ) i s c a l c u l a t e d from the t o t a l d i s c h a r g e and an a r b i t r a r y f a c t o r , CMOD, R i f f l e s and poo ls in the same stream can be s i m u l a t e d by making runs w i th d i f f e r e n t v a l u e s of CMOD. N u t r i e n t l e v e l s (RNUT) are modeled on ly as a u n i t f a c t o r , i . e . com-b i n i n g a l l n u t r i e n t s as one l i m i t i n g f a c t o r . Normal ly the v a l u e of RNUT i s z e r o . F o l l o w i n g leaf drop in the autumn and a l s o d u r i n g p e r i o d s of 24 heavy r a i n RNUT i s inc reased a c c o r d i n g t o a s p e c i f i e d f a c t o r FNUT, and does not g e n e r a l l y exceed 0 . 2 . Two f e a t u r e s of s u n l i g h t a re important in a model of pe r iphy ton growth: hours of s u n l i g h t and i n t e n s i t y of i l l u m i n a t i o n . The hours of d a y l i g h t , SUN, are approximated by a s i n e f u n c t i o n , wi th s o l s t i c e s on December 21 and June 2 1 . The ampl i tude of the d i f f e r e n c e between summer and w i n t e r (a f e a t u r e of l a t i t u d e and a l t i t u d e ) can be m o d i f i e d by the parameters SMIN (hours of d a y l i g h t on December 21) and ZNIT (hours of day -I i g h t on June 2 1 ) . I n t e n s i t y of i l l u m i n a t i o n i s a f e a t u r e u s u a l l y g l o s s e d over in a l g a l growth models , d e s p i t e exper imenta l work ( e . g . S o r o k i n and K r a u s s , 1958; M c l n t i r e , 1968) t h a t has e s t a b l i s h e d the e f f e c t s of d i f f e r e n t i l l u -m i n a t i o n l e v e l s on a l g a l growth. I b e l i e v e t h i s r e l a t i o n s h i p i s we l l enough understood to warrant the i n c l u s i o n of r e a l i s t i c i l l u m i n a t i o n l e v e l s in the model . The i n t e n s i t y of i l l u m i n a t i o n v a r i e s w i th l a t i t u d e , a l t i -t u d e , t ime of day and day of y e a r . The parameters BRTE ( f o o t - c a n d l e s i n -t e n s i t y a t noon on June 21) and DIM ( f o o t - c a n d l e s i n t e n s i t y a t noon on December 21) are s e t f o r 50°N l a t . a t sea leve l in the parameter l i s t g i ven in the Appendix . For each day , the hours of d a y l i g h t and the noon i n t e n -s i t y are used t o approximate an hour l y i n t e n s i t y c u r v e : 25 I I Iumi n a t i o n i ntens i ty ( f o o t - c a n d I e s ) 0 2 4 6 8 10 N 2 4 6 8 10 M Hours of the day F i g u r e 7 . I n t e n s i t i e s of s o l a r i l l u m i n a t i o n d u r i n g d a y l i g h t hours a t d i f f e r e n t t imes of y e a r . F i g u r e adapted from the I l l u m i n a t i o n Eng ineer ing Handbook. The shape of these curves is approx imate ly normal , but v a r i e s s l i g h t l y d u r i n g the course of the y e a r , as shown (see IES Handbook). On days w i t h p r e c i p i t a t i o n the i n t e n s i t y of s u n l i g h t i s reduced p r o p o r t i o n a t e l y . Fo r es t canopy a l s o reduces l i g h t i n t e n s i t y . A c o n s t a n t f a c t o r , SHAD, a p p l i e s a l l year (non-deciduous t r e e s and o t h e r permanent f i x t u r e s ) . A f a c t o r f o r shade caused by the leaves of deciduous t r e e s i s s e t by the parameters IBUD (day t r e e s begin to leaf o u t ) , IDRP (day t r e e s begin t o drop t h e i r l e a v e s ) , and SHDE ( p r o p o r t i o n of sun cut out by d e c i -duous canopy ) . (SHAD, IBUD, IDRP, and SHDE a r e a l l parameters t h a t can be m o d i f i e d t o s i m u l a t e d i f f e r e n t l o c a t i o n s and c l i m a t e s . The v a l u e s I have used most f r e q u e n t l y are l i s t e d w i t h the o t h e r parameters in Appendix B.) A d i s c o n t i n u o u s l i n e a r r e l a t i o n s h i p ( F igu re 8) i s used to c a l c u l a t e the e f f e c t of leaves in reduc ing i l l u m i n a t i o n : Mi d-summer S p r i n g and Autumn Mi d-w i n t e r 26 P r o p o r t i o n 1.0 of SHOE 0 . 5 0 . 0 I BUD IBUDt30 IDRP IDRPt30 F igure 8 . Days of the year The e f f e c t of the deciduous canopy on i l l u m i n a t i o n . (3) A l g a l Types and Morphology. "Stream p e r i p h y t o n " i s a very d i v e r s e c o l l e c t i o n of a lgae from every phylum (except the Phaeophyta) , w i th the e n t i r e range of pigments and enzymes t h a t e x i s t in the p h y c o l o g i c a l w o r l d . Changes in s p e c i e s dominance and d i s t r i b u t i o n of the p e r i p h y t o n community are common responses to changing c o n d i t i o n s . Thus the model a l l o w s comparison of t h r e e d i f f e r e n t a lgae a t a t i m e . Each k ind i s d e s -c r i b e d by a s e t of parameters , which w i l l be e x p l a i n e d below as they are used. The parameter va lues l i s t e d in Appendix B apply t o t h r e e types of a lgae t h a t might be found in a B r i t i s h Columbia s t ream: (A) an e a r l y - s p r i n g t y p e ; p r e f e r s c o l d w a t e r , r a p i d c u r r e n t s , and high I i g h t l e v e l s ; (B) an ear ly -summer t y p e ; p r e f e r s temperatures below I 5 ° C , moder-a te c u r r e n t s , and moderate l i g h t l e v e l s . minimal c u r r e n t s , and low l i g h t l e v e l s . The parameters t h a t d e f i n e these p re fe rences can e a s i l y be changed t o s u i t o t h e r k inds of a l g a e . (C) a m i d - and late-summer t y p e ; p r e f e r s temperatures up to 20°C D i f f e r e n t k inds of p e r i p h y t o n produce c o l o n i e s w i t h d i f f e r e n t 27 shapes . The shape i s important in de te rmin ing the p r o p o r t i o n of a co lony t h a t i s exposed t o optimum d i f f u s i o n g r a d i e n t s and l i g h t , and c o n v e r s e l y , how r a p i d l y a bottom layer of c e l l s w i l l d i e and cause the e n t i r e mat t o be swept away. The s i z e parameters (P) i n d i c a t e f o r each a l g a l type the f i v e s i z e groups ( i . e . grams dry weight per co lony) t o which the a c t i v e p r o p o r t i o n s (PP) and the spate loss f a c t o r s (SL) a p p l y . In the parameter l i s t shown (Appendix B ) , a l g a A tends to produce long f i l a m e n t s wi th a s t r o n g base ( i . e . r e l a t i v e l y c u r r e n t r e s i s t a n t ) , a l g a C tends t o grow f a t s p r e a d i n g mats ( i . e . r e l a t i v e l y l i k e l y t o s l o u g h ) , and a l g a B i s i n t e r -med ia te . On each day in which t h e r e i s s u c c e s s f u l c o l o n i z a t i o n of an a l g a , a new " c o h o r t " i s e s t a b l i s h e d , which i s ass igned the i n i t i a l s i z e , COLG. Growth and loss r a t e s are c a l c u l a t e d s e p a r a t e l y f o r each cohor t of each a l g a , so t h a t the s i z e and shape of the c o l o n i e s can be a f a c t o r in t h e i r development. (4) C o l o n i z a t i o n . Spores and v e g e t a t i v e c e l l s probably attempt t o c o l o n i z e any s u r f a c e t h a t they c o n t a c t . But in o r d e r f o r c o l o n i z a t i o n t o be s u c c e s s f u l , c e r t a i n p h y s i c a l requirements must be met. The dynamics of c o l o n i z a t i o n (as opposed to growth a f t e r c o l o n i z a t i o n ) are not we l l documented, l a r g e l y because of the g r e a t d i f f i c u l t y in making any a s s e s s -ment of c o l o n i z a t i o n f a i l u r e . (A lga l spores and v e g e t a t i v e r e p r o d u c t i v e c e l l s are a lmost i m p o s s i b l e t o count a g a i n s t a background of b a c t e r i a and p h y t o p l a n k t o n , and p o s i t i v e i d e n t i f i c a t i o n i s v i r t u a l l y i m p o s s i b l e . ) Therefore o n l y the s i m p l e s t assumptions are made: ( I ) the temperature must be w i t h i n the s p e c i f i e d t h r e s h o l d s TMIN and TMAX, and (2) the c u r r e n t (5mm above the s u b s t r a t e ) must be w i t h i n the s p e c i f i e d t h r e s h o l d s CMIN 28 and CMAX. The adequacy of these assumptions as a model f o r pe r iphy ton c o l o n i z a t i o n are d i s c u s s e d in more d e t a i l in r e l a t i o n to Problem #2 below. (5) Growth. Two d i f f e r e n t t h e o r i e s about pe r iphy ton growth r a t e s were programmed, as i s e x p l a i n e d in d e t a i l in the d i s c u s s i o n of Problem #1, below. The r e s u l t of t h i s c a l c u l a t i o n g i v e s the f i r s t e s t i -mate, o r " p o t e n t i a l " growth, which w i l l be r e a l i z e d by each cohor t on ly i f temperature c o n d i t i o n s are optimum and the c o l o n i e s a re not large enough to cause i n t e r f e r e n c e among ne ighbour ing c e l l s . The temperature e f f e c t i s c a l c u l a t e d us ing a s i n e f u n c t i o n , so t h a t on ly temperatures c l o s e t o the s p e c i f i e d t h r e s h o l d s w i l l r e s u l t in g r e a t l y reduced growth : P r o p o r t i o n of p o t e n t i a l growth TMIN TMAX Water temperature F igure 9 . The e f f e c t of water temperature on the r e a l i z e d p r o p o r t i o n of p o t e n t i a l growth r a t e s . S i n c e a c c l i m a t i z a t i o n i s a c r i t i c a l f a c t o r in d e t e r m i n i n g temperature e f f e c t s on growth r a t e s , I f e l t t h a t none of the exper iments repor ted in the l i t e r a t u r e (which ignore a c c l i m a t i z a t i o n ) gave i n f o r m a t i o n t h a t would suppor t a more e l a b o r a t e f u n c t i o n . The e f f e c t of co lony morphology i s determined by s e l e c t i n g the parameter f o r a c t i v e p r o p o r t i o n (PP) t h a t a p p l i e s to i t s s i z e and t y p e . If the n u t r i e n t l eve l i s h i g h e r than normal ( i . e . > 0 ) , growth i s 29 inc reased p r o p o r t i o n a t e l y . (6) L o s s e s . The dynamics of expor t are based p r i m a r i l y on my own exper iments , as d e s c r i b e d e lsewhere in t h i s t h e s i s . The s igmoid curve ( F i g u r e 6) i s not symmetr ical and t h e r e f o r e does not f i t a s imple mathe-m a t i c a l e q u a t i o n . So the r e l a t i o n s h i p between c u r r e n t and d a i l y loss r a t e s has been reduced t o a d i s c o n t i n u o u s l i n e a r f u n c t i o n as shown in F i g -ure 10. Dai ly . 9 .. . v • • l oss r a t e . 3 •• • 2 • 0 20 40 60 80 100 120 C u r r e n t ( c m . / s e c . ) F i g u r e 10. The e f f e c t of c u r r e n t on d a i l y loss r a t e s . The same loss r a t e s are assumed t o app ly to a l l types and s i z e s of a l g a e , s i n c e there i s no data on which to base a more r e a l i s t i c model . S i n c e the loss r e l a t i o n s h i p was measured under c o n d i t i o n s of m a i n -t a i n e d f low i t does not i n c l u d e the e f f e c t of s p a t e s . A spate o c c u r s in the model when the c u r r e n t f o r any day exceeds the recent c u r r e n t average (CADV) by more than a s p e c i f i e d l i m i t , SPLM. (CADV i s a " r u n n i n g average" i . e . each d a y ' s c u r r e n t is averaged wi th the p r e v i o u s CADV to c a l c u l a t e the next CADV.) The e f f e c t of a spate i s determined by the parameters SL which apply to each s i z e group of each a l g a . A d e s c r i p t i o n of f u r t h e r a d d i t i o n s to the loss dynamics i s inc luded in Problem #3 below. 30 When c o l o n i e s of a cohor t are reduced below the i n i t i a l s i z e COLG, the cohor t i s removed from the s i m u l a t i o n . (7) Output . The model produces two types of o u t p u t : (A) a t a b l e of the biomasses of each a l g a l type a t the end of each day i s l i s t e d in a permanent f i l e . Th is can be examined d i r e c t l y o r graphed. (B) a d e t a i l -ed d e s c r i p t i o n of d a i l y growth and losses of each c o h o r t , p lus the p h y s i -c a l c o n d i t i o n s f o r the day and the t o t a l biomasses and growth r a t e s of each a l g a l type are w r i t t e n on a d i s k s c r a t c h f i l e . T h i s i s use fu l when a f u n c t i o n a l r e l a t i o n s h i p has been changed and the r e s u l t s in the biomass t a b l e are not e a s i l y unders tood . Sample Uses of the Computer Model . To i l l u s t r a t e the use of t h i s model as an a i d in e v a l u a t i n g ideas about per iphy ton dynamics, t h r e e sample problems are examined. In each case the s u b r o u t i n e ALGA has been recompi led w i t h d i f f e r e n t dynamics, as d e s c r i b e d , and the r e s u l t s shown as a graph of the d a i l y biomass t a b l e s f o r one o r more types of a l g a e . In a l l o f the runs shown, the p a r t s of the model t h a t are not d i s c u s s e d are in the form t h a t i s shown in Appendix A. Problem #1 The general model of pr imary p r o d u c t i o n , as put f o r t h by C l a r k e , Edmondson and R i c k e r (1946) s t a t e s t h a t : P = A - R - D - C where: P = t o t a l inc rease o r decrease in b iomass . A = r a t e of a s s i m i l a t i o n of carbon (gross p h o t o s y n t h e s i s ) per u n i t b iomass. R = r a t e of loss of carbon ( r e s p i r a t i o n ) per u n i t b iomass . D = r a t e of death per u n i t b iomass . 31 C = r a t e of loss (due t o g r a z i n g , e t c . ) per u n i t b iomass . Gross p h o t o s y n t h e s i s minus r e s p i r a t i o n (A - R) i s d e f i n e d as the net p r o d u c t i o n , which i s assumed to be the r a t e a t which the p l a n t can add to i t s b iomass . Th is assumption i s adequate when the p l a n t t i s s u e s c o n -s i s t p r i m a r i l y of sugar , s t a r c h , c e l l u l o s e and o ther (Ch^O^ compounds. However, a high r a t e of p r o t e i n o r amino a c i d s y n t h e s i s r e s u l t s in a low-ered r a t e of biomass p r o d u c t i o n because of the high energy requi rements of p roduc ing these compounds. A p l a n t ' s a s s i m i l a t o r y q u o t i e n t (A.Q. = CO^/O^) i n d i c a t e s how much of i t s metabol ism i s devoted to s y n t h e s i s of ( Q ^ O ^ compounds; an A .Q . of 1.0 would i n d i c a t e pure (CH20) n s y n t h e s i s , and would f i t the C l a r k e , Edmondson and R i c k e r growth model p e r f e c t l y . In 1969 Myers e s t a b l i s h e d t h a t the a s s i m i l a t o r y q u o t i e n t s o f p e r i -phyton a re g e n e r a l l y q u i t e low compared to A . Q . ' s of t e r r e s t r i a l p l a n t s . Fur thermore , i t i s not p o s s i b l e t o amend the C l a r k e , Edmondson and R i c k e r model s imply by adding the A.Q. f a c t o r because A . Q . ' s are not c o n s t a n t ; they vary w i t h the age of the co lony and i t s degree of a c c l i m a t i z a t i o n ( V o l l e n w e i d e r , 1969). D e s p i t e these s h o r t c o m i n g s , the C l a r k e , Edmondson and R i c k e r model has been w i d e l y a p p l i e d to pe r iphy ton w i thout m o d i f i c a -t i o n ( e . g . Odum, 1956; Thomas and O ' C o n n e l l , 1966; M c l n t i r e , 1966b and 1968b; and Hal 1, 1973). A d i f f e r e n t approach to e s t i m a t i n g growth r a t e s was suggested by Kevern and B a l l (1965) ; p o t e n t i a l growth c o u l d be c a l c u l a t e d from the r a t e of i n c r ease of a new co lony d u r i n g the log -phase of i t s growth ( i . e . be fo re f e a t u r e s such as the s i z e of the co lony begin t o reduce growth r a t e s ) . Measurements of log -phase growth r a t e s were made by S o r o k i n and Krauss (1958) a t d i f f e r e n t l i g h t i n t e n s i t i e s f o r s e v e r a l d i f f e r e n t s p e c i e s 32 of a l g a e . These r e s u l t s can be combined w i t h the r e s u l t s of M c l n t i r e and Phinney (1965) on the r e l a t i v e e f f i c i e n c i e s of l i g h t - a d a p t e d and shade-adapted communit ies t o produce a theory of pe r iphy ton growth r a t e s as i l l u s t r a t e d in F i g u r e I I . Growth r a t e TI6 KM T i r I I Iuminat ion F i g u r e I I . The e f f e c t of i l l u m i n a t i o n i n t e n s i t y on hour l y growth r a t e s . PMAX = log -phase (Maximum) growth r a t e ; TIB = lower i l l u m i n a t i o n t h r e s h o l d ; TIT = i l l u m i n a t i o n a t which i n h i b i t i o n b e g i n s ; KM = the i l l u m i n a t i o n a t which the growth r a t e equa ls i PMAX. The computer s i m u l a t i o n program was used t o compare the C l a r k e , Edmondson and R i c k e r growth model w i th the model shown in F igu re I I . Stream parameters were s e t as much as p o s s i b l e to be l i k e New Hope Creek , North C a r o l i n a , which was s t u d i e d e x t e n s i v e l y by C . A . S . H a l l (1971 and 1973). H a l l ' s data f o r r e s p i r a t i o n and p h o t o s y n t h e s i s were used f o r the run shown in F igure ' 12a; p o t e n t i a l growth was c a l c u l a t e d from the d i f f e r -ence between gross p h o t o s y n t h e s i s and r e s p i r a t i o n . The p e r i p h y t o n commu-n i t y c o n s i s t e d of a l i g h t - a d a p t e d and a shade-adapted a l g a (parameters s e t as f o r a lgae A and C in Appendix B ) , and t h e i r growth was combined in the g r a p h i c o u t p u t . FIGURE 1 2 Comparison of two growth dynamics, (a) C l a r k e , Edmondson and R i c k e r model , (b) Log-phase growth model . 34 For the run shown in F igu re 12b the r e l a t i o n s h i p shown by the curve above was programmed as an equat ion of the form: PMAX * F F t KM where: P = p o t e n t i a l hour l y growth r a t e . PMAX = a maximum h o u r l y growth r a t e (based on the work of S o r o k i n and K r a u s s , 1958). F = the a v a i l a b l e l i g h t f o r the hour minus a lower t h r e s h o l d o f iI I u m i n a t i o n , T IB . KM = the i l l u m i n a t i o n a t which P = £PMAX. P h o t o s y n t h e t i c i n h i b i t i o n due to e x c e s s i v e l i g h t l e v e l s was programmed as a l i n e a r f u n c t i o n which took e f f e c t i f the a v a i l a b l e l i g h t exceeded the t h r e s h o l d i l l u m i n a t i o n , TIT. The lack of biomass p r o d u c t i o n shown in F igu re 12a i s p a r t l y due t o the f a c t t h a t the r e s p i r a t i o n l e v e l s recorded by H a l l i n c l u d e the r e s -p i r a t i o n of a l l the b a c t e r i a and microfauna t h a t are i n s e p a r a b l e from the pe r iphy ton community under n a t u r a l c o n d i t i o n s . H i g h l y t u r b u l e n t water and s a t u r a t e d oxygen l e v e l s a l s o o f t e n c o n t r i b u t e t o e r r o r f a c t o r s in such measurements t h a t may be l a r g e r than the m e t a b o l i c r a t e s be ing mea-s u r e d . Th is r e f l e c t s a very rea l problem in stream p e r i p h y t o n s t u d y : a p p l i c a t i o n of the C l a r k e , Edmondson & R i c k e r theory puts emphasis on mea-s u r i n g gross p h o t o s y n t h e s i s and r e s p i r a t i o n , when in f a c t these r a t e s a re inadequate in p r e d i c t i n g p o t e n t i a l growth (as shown by the model o u t p u t s ) and are as yet ex t remely d i f f i c u l t to measure in n a t u r a l s t r e a m s . On the o t h e r hand, the inc rease in biomass s h o r t l y a f t e r c o l o n i z a t i o n ( i . e . l o g -phase growth) i s e a s i l y measured in the f i e l d , and i s s u f f i c i e n t to 35 generate r e a l i s t i c output in the model . I t would seem then t h a t measure-ments of gross p h o t o s y n t h e s i s and r e s p i r a t i o n are not the bes t t h i n g s t o measure i f one i s i n t e r e s t e d in e s t i m a t i n g growth r a t e s of p e r i p h y t o n . Problem #2 Does l i g h t a f f e c t c o l o n i z a t i o n ? It has long been known t h a t s p e c i e s of pe r iphy ton are remarkably p a r t i c u l a r about the s u b s t r a t e they choose to c o l o n i z e . Each s p e c i e s seems t o have some requirement f o r the s i z e , o r minera l c o n t e n t , o r s u r f a c e t e x t u r e , o r presence/absence o f some o t h e r o rgan isms , e t c . , on t h e i r s u b s t r a t e . But t h e r e are some general requi rements in which p e r i p h y t o n are more a l i k e : c o l o n i z i n g c e l l s each seem t o r e q u i r e a s p e c i f i c temperature range ( P a t r i c k _et a_L, 1969), and they each r e q u i r e a c u r r e n t range s i m i l a r t o the c u r r e n t r e q u i r e d by an e s t a b l i s h e d c o l o n y . But do c o l o n i z i n g c e l l s r e q u i r e a c e r t a i n leve l of i l l u m i n a t i o n , and , i f s o , i s i t the same i l l u m i n a t i o n leve l t h a t i s p r e -f e r r e d by a we I I -developed co lony? M c l n t i r e and Phinney (1965) compared c o l o n i z a t i o n in two labora to ry streams in which a l l f a c t o r s were the same except f o r l i g h t l e v e l s . They found t h a t the r a t e of log -phase growth was g r e a t e r in the b r i g h t e r s t r e a m , but i t i s not c l e a r from t h e i r r e s u l t s how the a c t u a l r a t e of e s t a b l i s h i n g new c o l o n i e s d i f f e r e d . I observed in my f i e l d work a t a l l t h r e e streams t h a t t h e r e were more c o l o n i e s per square inch on my wh i te ceramic t i l e s ( i . e . a b r i g h t , r e f l e c t i v e s u r f a c e ) than on the darker g r a v e l , but t h i s c o u l d have been p a r t l y due t o the ease w i th which c o l o n i e s c o u l d be s p o t -ted on the wh i te background. The computer s i m u l a t i o n model was used to t r y some d i f f e r e n t hypo-theses f o r the e f f e c t of i l l u m i n a t i o n on c o l o n i z a t i o n . The stream 36 parameters were s e t to be l i k e the B i g Qual icum R i v e r , where I had a chance t o observe n a t u r a l pe r iphy ton growth. In the f i r s t run ( F igu re 13a) s i m u l a t e d temperature and c u r r e n t were the o n l y f a c t o r s a f f e c t i n g c o l o n i z a t i o n . The r e s u l t i s t h a t growth appears l a t e r than e x p e c t e d , and c o l o n i z a t i o n c o n t i n u e s a t a r a p i d r a t e l a t e r than e x p e c t e d . Most s u r p r i s i n g is the reappearance and bloom of the s p r i n g - t y p e a l g a in the autumn; t h e r e i s o f t e n a smal l regrowth o f e a r l y types of a l g a e in the f a l l , but i t i s r a r e l y as g r e a t as the s p r i n g bloom. For the second run the c o l o n i z a t i o n s e c t i o n of the program was recompi led w i t h an i l l u m i n a t i o n requirement f o r c o l o n i z a t i o n . If the i l l u m i n a t i o n was g r e a t e r o r less than the amount r e q u i r e d f o r maximum growth r a t e s , no c o l o n i z a t i o n o c c u r r e d . T h i s y i e l d e d a lmost the same d i s -t o r t e d r e s u l t s ( F igu re 13b). How then does i l l u m i n a t i o n e x e r t i t s e f f e c t ? P e r i p h y t o n i s in some ways analagous t o annual t e r r e s t r i a l p l a n t s . The seeds of annuals g e n e r a l l y germinate under c o n d i t i o n s t h a t would not be conduc ive t o the best growth in an o l d e r p l a n t ; by the t ime the s e e d -l i n g has developed the weather has improved. If the seeds wa i ted u n t i l c o n d i t i o n s were opt imal f o r an o l d e r p l a n t , weeks of good growing c o n d i -t i o n s would be l o s t t o g e r m i n a t i o n . Perhaps pe r iphy ton have a s i m i l a r response to the r e g u l a r changes in i l l u m i n a t i o n throughout the y e a r . ( I l l u m i n a t i o n would be a more r e l i a b l e cue than water tempera tu re , s i n c e m e l t i n g snow can run out q u i c k l y and a t less p r e d i c t a b l e t i m e s . ) For the next run the c o l o n i z a t i o n dynamics were aga in reprogrammed. Each p e r i p h y t o n type was ass igned an " i n d e x i l l u m i n a t i o n " ( C I I ) , equal to the expected mid-day i l l u m i n a t i o n leve l t h a t e x i s t s d u r i n g the t ime t h a t J F M R M J J R S Q N D FIGURE 13 Comparison of hypotheses on the e f f e c t of i l l u m i n a t i o n on c o l o n i z a t i o n . (a) No e f f e c t , (b) I l l u m i n a t i o n parameters from growth dynamics used, (c) " Index i l l u m i n a t i o n s " used. 38 i t s c o l o n i e s are beg inn ing t o appear a t Qua l icum. T h i s gave the r e s u l t s shown in F igu re 13c. The idea t h a t pe r iphy ton may use the r e g u l a r annual p a t t e r n of i l l u m i n a t i o n as a cue to e s t a b l i s h c o l o n i e s p r i o r t o opt imal growth c o n -d i t i o n s arose from use of the computer model : i t was the s i m p l e s t a d j u s t -ment to the c o l o n i z a t i o n dynamics t h a t gave good r e s u l t s . Exper iments on rea l pe r iphy ton would be necessary in o r d e r t o determine whether t h i s i s a rea l p a r t of t h e i r dynamics o r merely a f o r t u i t o u s c o i n c i d e n c e . Problem #3 How does temperature a f f e c t loss ra tes? The r e s u l t s of my own research i n d i c a t e d t h a t t h e r e i s a complex r e l a t i o n s h i p between the a v e r -age c u r r e n t and the d a i l y loss r a t e s . Th is r e l a t i o n s h i p was inc luded in the s i m u l a t i o n model as a d i s c o n t i n u o u s l i n e a r f u n c t i o n , as e x p l a i n e d in the d e s c r i p t i o n of the model . However, the e f f e c t of c u r r e n t a lone was found t o be i n s u f f i c i e n t t o s i m u l a t e loss r a t e s t h a t would remove a l g a l growth r a p i d l y enough a f t e r i t s f a v o u r a b l e season had ended. T h i s was e s p e c i a l l y e v i d e n t f o r the s p r i n g - t y p e a l g a e , whose biomass would l i n g e r a l l through the summer because the c u r r e n t e f f e c t would be removing on ly a smal l p r o p o r t i o n each day. A sample run us ing the c u r r e n t e f f e c t a lone i s shown in F i g u r e 14a. When c o o l e r weather and more r a p i d c u r r e n t s occur red in the autumn, in a d d i t i o n t o a smal l i n c r e a s e in n u t r i e n t l e v e l s from f a l l e n l e a v e s , t h e r e were s t i l l so many c o l o n i e s of s p r i n g a lgae l e f t t h a t a very la rge bloom r e s u l t e d . C l e a r l y the re i s some component o t h e r than the s h e a r i n g and s c o u r -ing of c u r r e n t t h a t determines loss r a t e s . Two p o s s i b l e f a c t o r s a re l i k e l y : ( I ) i n s u f f i c i e n t c u r r e n t ( i . e . to meet m e t a b o l i c requi rements) 39 FIGURE 14 Comparison of hypotheses concern ing pe r iphy ton loss r a t e s , (a) Losses due to c o n s t a n t c u r r e n t e f f e c t o n l y , (b) " i n s u f -f i c i e n t c u r r e n t e f f e c t " added, (c) Temperature e f f e c t added, (d) Temperature e f f e c t made more s e v e r e . a b c J F M R M J J R S Q N D FIGURE 14 (cont inued) 41 would cause more r a p i d senescence of the i n t e r i o r c e l l s in mats , and lead to increased losses v i a s l o u g h i n g , o r (2) temperatures above o r below the t h r e s h o l d s would cause e x t e r i o r c e l l s t o d i e , and these dead c e l l s would be more e a s i l y removed by normal c u r r e n t e f f e c t s . In the second run , an " i n s u f f i c i e n t c u r r e n t f a c t o r " was added t o the o r i g i n a l dynamics ( F igu re 14b). Large mats were more r a p i d l y reduced, and there were fewer c o l o n i e s a t the end of the summer, but the o v e r a l l r e s u l t was not much improved. So in the t h i r d run the dynamics of loss r a t e s were changed: f o r each degree above o r below the temperature t h r e s h o l d s , the d a i l y loss r a t e was inc reased by .01 (\%). T h i s was b e t t e r ( F igu re 14c ) , but s t i l l e x -c e s s i v e numbers of o l d c o l o n i e s were l i v i n g through the summer and p roduc -ing a Iarge fa I I bloom. Examinat ion of the d e t a i l e d output showed t h a t the loss r a t e s due t o temperature , c a l c u l a t e d as above, were never very la rge because the max-imum summer water temperature was not g r e a t l y in excess of the upper t h r e s h o l d . So t h e r e were two p o s s i b i l i t i e s : the a lgae cou ld be made more " s t e n o t h e r m i c " ( i . e . the upper t h r e s h o l d reduced ) , o r the losses due to e x c e s s i v e heat cou ld be made more s e v e r e . My o r i g i n a l c h o i c e s f o r temper -a t u r e t h r e s h o l d s had produced r e a l i s t i c growth r a t e s , so I t r i e d i n c r e a s i n g the r a t e s of loss a t temperatures beyond the t h r e s h o l d s . T h i s was done by s q u a r i n g the d i f f e r e n c e between the t h r e s h o l d and the water tempera tu re , and i n c r e a s i n g the losses due t o temperature a c c o r d i n g l y , as i l l u s t r a t e d in F igu re 15. 42 Increase i n loss r a t e f a c t o r MIN-5 MIN _ MAX MAXt5 Temp. F i g u r e 15. The e f f e c t of temperature on loss r a t e s . I decided a r b i t r a r i l y to l i m i t such losses t o .25 per day, f e e l i n g t h a t g r e a t e r d a i l y l osses were very u n l i k e l y . Th is new temperature e f f e c t was used in the f o u r t h r u n , which g i v e s r e s u l t s t h a t look very much l i k e the p a t t e r n of Thorea growth a t B i g Qua l i cum. One can conc lude t h a t , w h i l e the model cannot be s a i d t o have d e -f i n e d the e f f e c t of temperature on loss r a t e s , i t has i n d i c a t e d one p o s s i -b i l i t y . P i scuss ion In the t h r e e cases d e s c r i b e d above, the computer s i m u l a t i o n model has served as a framework in which hypotheses about pe r iphy ton dynamics can be compared. It has made i t p o s s i b l e to c a l c u l a t e in g r e a t d e t a i l the p r e c i s e consequences of the "dynamics" w i th which i t was programmed. Each t ime two hypotheses were compared, the c r i t i c a l assumption was t h a t the r e s t of the model was " c o r r e c t " ( i n the sense of being a d e -q u a t e l y r e a l i s t i c ) . I t i s p o s s i b l e f o r mis takes to be complementary, e . g . f o r a shor tcoming in one p a r t of the model t o be hidden by an i n c o r r e c t f e a t u r e in another p a r t . There fo re a model can produce "good l o o k i n g " d a i l y biomass amounts w i thout be ing a t a l l r e a l i s t i c . There are many 43 p a r t s of t h i s model where the dynamics had to be guessed because the i n -fo rmat ion was not unambiguously a v a i l a b l e from the l i t e r a t u r e . The f i n a l form of the model generates r e a l i s t i c numbers f o r d i f f e r e n t types of s t reams , but i t s g r e a t e s t va lue i s in the i n i t i a l t e s t i n g of some new hypotheses about pe r iphy ton dynamics. The unambiguous language of FORTRAN has s t a t e d these hypotheses c l e a r l y , so t h a t d e s i g n i n g exper iments to prove or d i s p r o v e them is s i m p l i f i e d . T h i s i s an important use of s i m u l a t i o n models in B i o l o g y : t o c l e a r l y i d e n t i f y areas where research i s needed, t o help the r e s e a r c h e r i d e n t i f y i n c o n s i s t e n c i e s in h i s own t h i n k i n g , and to s t a t e h i s hypotheses and assumptions in unambiguous te rms . Instead of produc ing computer models t o summarize long research p r o j e c t s , i t should be recognized t h a t t h e i r g r e a t e s t va lue is when the research i s being p lanned . When a l l the dynamics of pe r iphy ton have been d e f i n e d , we w i l l not need t o model them. REFERENCES 45 REFERENCES B a l l , R . C - a n d F .F . Hooper 1959. 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H y d r o b i o l o g i a 2 7 : 5 5 9 - 5 7 0 . M c l n t i r e , C .D . 1966b. Some f a c t o r s a f f e c t i n g r e s p i r a t i o n in l o t i c e n -v i ronments . Ecology 4 7 : 9 1 8 - 9 3 0 . M c l n t i r e , C. David 1968. P h y s i o l o g i c a I - e c o l o g i c a I s t u d i e s of b e n t h i c a l g a e in l a b o r a t o r y s t reams. Journa l of Water P o l l u t i o n C o n t r o l . 4 0 : 1 9 4 0 - 1 9 5 2 . M c l n t i r e , C. David 1973. " P e r i p h y t o n Dynamics in L o t i c Env i ronments . " Ecology 54 ( i n press ) 46 M c l n t i r e , C D . , R . L . G a r r i s o n , H.K. Phinney and C . E . Warren 1964. Pr imary P r o d u c t i o n in Laboratory St reams. Limnology and Oceanography 9 : 9 2 - 1 0 2 . M c l n t i r e , C .D. and H.K. Phinney 1965. Laboratory s t u d i e s of pe r iphy ton p r o d u c t i o n and community metabol ism in l o t i c env i ronments . E c o l o -g i c a l Monographs 3 5 : 2 3 7 - 2 5 8 . Myers , Jack 1969. G e n e t i c and a d a p t i v e p h y s i o l o g i c a l c h a r a c t e r i s t i c s observed in the c h l o r e l l a s . _[n_: P r e d i c t i o n and Measurement of P h o t o s y n t h e t i c P r o d u c t i v i t y . Wageningen Centre f o r A g r i c u l t u r a l P u b l i s h i n g and Documentation 1970. Odum, H.T. 1956. Pr imary p r o d u c t i o n in f l o w i n g wate rs . Limnology and Oceanography 1 : 1 0 2 - 1 1 7 . P a t r i c k , Ruth , Boman Crum, and John C o l e s , 1969. Temperature and Manganese as d e t e r m i n i n g f a c t o r s in the presence of diatom or b l u e -green a l g a l f l o r a s in s t r e a m s . Proceed ings of the N a t i o n a l Academy of Sc ience 6 4 : 4 7 2 - 4 7 8 . S o k a l , Robert R. and F. James RohIf 1969. B iomet ry ; the p r i n c i p l e s and p r a c t i c e of s t a t i s t i c s in b i o l o g i c a l r e s e a r c h . San F r a n c i s c o , W.H. Freeman. S o r o k i n , C o n s t a n t i n e and Robert W. Krauss 1958. The e f f e c t s of l i g h t i n t e n s i t y on the growth r a t e s of green a l g a e . P l a n t P h y s i o l o g y 3 3 : 1 0 9 - 1 1 3 . S t e w a r t , W.D.P. and G a i l A lexander 1971. Phosphorous a v a i l a b i l i t y and n i t r o g e n a s e a c t i v i t y in a q u a t i c b l u e - g r e e n a l g a e . Freshwater B i o l o g y 1 : 3 8 9 - 4 0 4 . Thomas, N.A. and R . L . O 'Connel l 1966. A method f o r measuring pr imary p r o d u c t i o n by stream benthos . Limnology and Oceanography 1 1 : 3 8 6 - 3 9 2 . W h i t f o r d , L .A . I960. The c u r r e n t e f f e c t and the growth of f r e s h - w a t e r a l g a e . T r a n s a c t i o n s of the American Microscopy S o c i e t y 7 9 : 3 0 2 - 3 0 9 . W h i t f o r d , L .A . and G . J . Schumacher 1964. E f f e c t of a c u r r e n t on r e s p i r a -t i o n and minera l uptake in S p i r o q y r a and Oedoqoniurn. Ecology 4 5 : 168-170. APPENDIXES 48 'APPENDIX A Listing of the Computer Program. C INPUT READS IH PARAMETER VALUES FOR ALGAE MOCEL COMMON ARTM,PPT,SNO,SMLT,CUR,TIB (3) ,TIT (3) ,RNUT,WTEM,SUN,SLTE, . A (25,3,2) ,CMIJJ (3) ,CMAX(3) ,TKIN (3) , T M A X (3) ,PMAX (3) ,SPER (16,9) , .P(3,6),PP (5) ,CL (11) ,5L(5) ,G (3) ,TMMX,TMMN,APPT,SNOW,CKOD,GRND, ,FNUT,RLEF,GTEM,AMPW,ZNIT,SMIN,SHDE,PI,TPPT,RAIN,BRTE,DIM,TS, .COLG,COLN,CADV,SPLN,IBUD,IDRP,KM (3) ,ICO(3),OMEG,IS,IR,I, . B (365,3) ,RFP (4) ,CII (3) COMMON CLT (12) ,ICN (3) DIMENSION AA (40) READ (4,8)AA 8 FORMAT (40A2) HRITE(5,9)AA 9 FORMAT (3X,40A2) C WRITE HEADINGS FOR PRINTER OUTPUT WRITE(5,10) 10 FORMAT(4X/4X,'DAI CUR RNUT WTEM ILLUM CORT-A .'BMAS-A GRT-A CORT-B BKAS-B GRT-B COBT-C EMAS-C GRT-C') READ(4,1)TMMX,TMMN,APPT,SNOW,CMOD,GHND,FNUT,RLEF,GTEM,AMPW,ZNIT, .SMIN,SHDE,PI,TPPT,RAIN,BRTE,DIM,TS,COLG,COIN,CAEV.SPLM READ (4,2)IBUD,IDRP, (KH (I) ,1=1,3) READ (4, 1) (CHIN (I) ,1=1 ,3) , (CM AX (I) , 1= 1 , 3) , (TMIN (I) , 1= 1 , 3) , . (TMAX (I) ,1=1,3) , (TIB (I) ,1=1,3) , (TIT (I) ,1=1,3) , (PMAX (I) ,1=1,3) , . (RFP (I) ,1=1,4) , (CII (I) ,1=1,3) DO 4 0 J=1,9 * READ(4,3) (SPER (I,J) ,1=1,16) 40 CONTINUE DO 45 J=1,3 READ{4,4) (P (J,I) ,1=1,6) 45 CONTINUE READ (4,5) (PP (I) ,1=1,5) , (SL(I) ,1=1,5) READ(4,6) (CL(I) ,1=1,11) READ(4,6) (CLT (I) ,1=1, 12) DO 50 J=1,3 G (J) =0.0 ICO(J)=0 ICK(J)=0 CO 50 1=1,365 B(I,J)=0.0 50 CONTINUE 1 FORMAT (9X.F10.2) 2 FORMAT (9X,13) 3 FORMAT (7X,16F4.2) 4 FORMAT (9X,5F5.2,F8.2) 5 FORMAT (9X.5F5.2) 6 FORMAT(9X,12F5.2) RETURN END SUBROUTINE PRYS C PHYS GENERATES THE PHYSICAL CONDITIONS FOR EACH EAY COMMON ARTM,PPT,SNO,SKLT,CUR,TIB(3) ,TIT (3) ,RNUT,WTEM,SUN,SLTE, .A(25,3,2),CMIN(3),CMAX(3),TKIN(3),TMAX(3),PMAX(3),SPER(16,9), .P (3,6),PP (5) ,CL (1 1) ,SL (5) ,G (3) ,TMMX,TMMN,APPT,SNOW,CMOD,GRND, .FNUT,RLEF,GTEM,AMPW,ZNIT,SMIN,SHDE,PI,TPPT,RAIN,ERTE,EIM,TS, .COLG,COLN,CADV,SPLM,IBUD,IDRP,Ktt (3) ,ICO (3),OMEG,IW,IR,I, 49 C MELTING OCCURS 45 SMLT = ARTM/1** SNO=SNOW-SMLT SNOW=St!0 C TOTAL DISCHARGE IS CALC. BY SUMMING FPT, SHOW KELT, AND GROUNDWATER 50 IF (1-3)51,51,55 51 DRAN=PPT GO TO 60 C DRAINAGE FROM RAIN IS DISTRIBUTED OVER SEVERAL CAYS 55 DRAN= (PPT + RAItO/2. RAIN=DRAN C NUTRIENTS ARE PICKED UP IN WATERSHED AT A CONSTANT RATE 60 RN= (DRAN+ (SMLT*.2))*FNUT C GROUNDWATER DILUTES NUTRIENT CONCENTRATION RNOF=DPAN+GRMD+ (SMLT*.2) RNUT=RH*( (DRAN +(SMLT*.2))/RNOF) IF (I .GE. ICLN .AND. ARTM .GT. 0.)RNUT=RNUT*(1.0+RLEF) C CURRENT (5MK. ABOVE SUBSTRATE) IS A LINEAR FACTOR OF TOTAL DRAINAGE CUR=RNOF*CMOD C ESTABLISH RECENT CURRENT AVERAGE CADV= ( (3.*CADV)+ CUR)/4.0 C WATER TEMP IS CALC. FROM WATER SOURCES T1 = GRND * GTEM T2= (SMLT/5.)*0.5 T3=DRAN*((SIN(OMEG)+1.)/2.)*AMPW WTEM = (T1+T2*T3) / (GRND+(SMLT/5.)+DRAN) C WATER TEMP. CHANGES ARE BUFFERED BY LATENT HEAT WRITE (3,1) 1 FORMAT (3X,'OUT OF PHYS') IF (ARTM - GTEM)200,200,90 90 WTEM= (WTEM*3.+ARTK)/4. 200 RETURN END SUBROUTINE ALGA COMMON ARTM,PPT,SNO,SMLT,CUR,TIB (3) ,TIT (3) ,RNUT,WTEM,SUN,SLTE, .A(25,3,2) ,CMIN(3) ,CMAX(3) ,TMIN (3),TMAX (3),PMAX(3),SPER(16,9), • P (3,6) ,PP (5) ,CL (11) ,SL (5) , G (3) ,TMMX,TKMN,APPT,SNOW,CMOE,GRNC, .FNUT,RLEP,GTEM,AHPW,ZNIT,SMIN,SHDE,PI,TPPT,RAIN,BRTE,DIM,TS, .COLG,COLN,CADV,SPLM,IBUD,IDRP,KM (3) ,ICO (3) ,OMEG,IW,IR,I, .B(365,3) ,RFP (4) ,CII (3) COMMON CLT (12) ,ICN (3) DIMENSION TE(3) C BEGIN LOOP OVER THREE ALGAL TYPES DO 100 IT=1,3 C C COLONIZATION C C CALC. SUCCESSFUL COLONIZATION FROM UPSTREAM C TEST TEMPERATURE THRESHOLDS IF (WTEM .GT. TMIN (IT) .AND. WTEM .LT. TMAX (IT))GO TO 50 TE (IT) =0.0 GO TO 100 C TEST CURRENT THRESHOLDS 50 IF (CUR .LE. CHIM (IT) .OR. CUR .GE. CMAX(IT))GO TO 90 C SCALE SUCCESS OF COLONIZATION BY TEMPERATURE AND ILLUMINATION IF (ICO (IT) .GE. 25)GO TO 90 T=((WTEM-TMIN(IT))/(TKAX(IT)-TMIH(IT))*2.0*PI)• (PI*1.5) T=(SIN (T) + 1.0J/2.0 S1=CII (IT)-1000. IF (SLTE .LE. SI .OR. SLTE .GE. CII (IT))GO TO 90 50 . E (365,3) ,RFP (4) ,CII (3) COMMON CLT (12) ,ICN (3) DIMENSION ISR(6) DATA ISR/0,70,161,252,34 3,366/ C DAILY AIR TEMPERATURES ARE GENERATED WITH A SINE FUNCTION TEMP= ( ( (SIN (OMEG)+1.)/2.)* (TMMX-TMUN))+TMMN C A RANDOM VARIABLE IS ADDED TO MAKE TEMP SEQUENCE REALISTIC X=FRANDN (0.0) ARTM=TEHP+<X*5.) C HOURS OF SUNLIGHT IS GENERATED FROM A SINE FUNCTION SUN= ( (SIN (OMF.G)+1.)/2.) * (ZNIT - SHIN) + SMIN C INTENSITY OF NOON HOUR (CLOUDLESS) SUN IS ALSO A SINE FUNCTION SLTE = ( (SIN (OMEG)+1.J/2.) * (BRTE - DIM) + DIM C LIGHT INTENSITY IS REDUCED BY PERMANENT SHADE SLT£=SLTE*(1.0-SHDE) C LIGHT INTENSITY REDUCED BY DECIDUOUS CANOPY ILEF=IBUD+30 ICLN=IDRP+30 IF (IBUD - I)10,20,20 10 IF (ILEF - I) 12, 1 1, 11 11 S= (TS/30.)*(I-IBUD) GO TO 19 12 IF (IDRP - I)14,13,13 13 S=TS GO TO 19 14 IF (ICLN - I)20,15,15 15 S= (TS/(-30.))*(I-IDRP)+TS 19 SLTE = SLTE * (1. 0 - S) C PRECIPITATION OCCURS ONLY ON BELOW AVERAGE TEMP CAYS 20 IF (X)30,30,25 C THERE IS NO PRECIPITATION 25 PPT=0. IF (SNOW)40,40,28 28 IF (ARTM)29,29,45 C ACCUMULATED SKOW DOES NOT MELT 29 SNO=SNOW SMLT=0. GO TO 50 30 DO 33 JJ=1,5 KK=JJ+1 IF (I .GE. ISR(OJ) . AND. I . LT. ISR (KK))IR=JJ 33 CONTINUE IF (IR .EQ. 5)IR=1 PPT=-X*3.*(APPT*RFP(IR)/91.25) TPPT - TPPT + PPT C INTENSITY OF SUNLIGHT IS REDUCED ON DAYS WITH PRECIPITATION SLTE = SLTE * (1.0-(PPT/2.)) IF (ARTM)35,35,34 34 IF (SNOW)40,40,45 C PPT FALLS AS SNOW IF ARTM .LE. 0. C ASSUMPTION THAT 1 INCH RAIN EQUALS 5 INCHES SNOW 35 SNO=SNOW+ (5.*PPT) PPT = 0. S NOW = SNO SMLT=0.0 GO TO 50 C THERE IS NO SNOW TO MELT 40 SMLT=0.0 SNO=0. GO TO 50 S=((SLF -S1) /1000.*2.*PI)+(PI*1.5) S= (SIN (S) +1.0)/2.0 C CALC. NUMBER OF COLONIES IH THIS NEW COHORT CA= (COLN+1.0) *T*S IA=CA IF (IA . LT. 1) GO TO 90 C INCREASE NUMBER OF COHORTS ICN (IT)=ICN(IT) +IA ICO(IT)=ICO(IT) +1 IC=ICO(IT) A (IC,IT,1)=IA C THEY ALL BEGIN AT THE INITIAL SIZE {'PARAMETERS') A (IC,IT,2) =COLG C C GROWTH C C POTENTIAL GROWTH IS CALC FROM LIGHT AND TEMP FACTORS C CALC TEMP EFFECT ON POTENTIAL GROWTH 90 OM = (WTEM - TMIN (IT)) / (TMAX (IT)-TMIN (IT))*PI TE(IT)= (SIN (OM)/2.)+.5 100 CONTINUE IF (ICO(1)+ICO(2)+ICO (3)) 500,500, 110 C LIGHT EFFECT IS DIVIDED INTO HOURS AT EACH ILLUMINATION 110 IHR=SUN-7 C LOOP OVER HOURS OF DAYLIGHT C EACH HOUR'S GROWTH IS CALCULATED IN SEQUENCE DO 250 IP=1,16 IF (SPEH(IP,IHR) .LE. 0.0)GO TO 260 C CALC LIGHT AVAILABLE THIS HOUR AL=SLTE*SPER(IP,IHR) C BEGIN LOOP OVER ALGAL TYPES DO 245 IT=1,3 INUM=ICO(IT) IF (INUM .LE. 0)GO TO 245 IF (TE (IT) . LE. 0.0JGO TO 245 C CALC. POTENTIAL GROWTH BASED ON AVAILABLE LIGHT IF (AL .LE. TIB (IT))GO TO 245 IF (AL .GE. TIT(IT))GO TO 160 F=AL-TIB(IT) C DISK EQUATION FOR MOST ILLUMINATIONS PGRO = PMAX (IT) * F / (F + KM (IT) ) GO TO 180 C PHOTO-INHIBITION OCCURS AT HIGH ILLUMINATIONS 160 PGRO= (2.*PMAX(IT))-(PMAX(IT)*AL/TIT(IT)) IF (PGRO .LT. Q.0)PGRO=0.0 C CALC GROWTH OF EACH COHORT 180 DO 240 IC=1,INUM C CALC PORPORTION OF MAT MASS THAT IS IN ACTIVE GROWTH PHASE DO 200 JJ=1,5 KK=JJ*1 IF (A(IC,IT,2) .GE. P(IT,KK))GO TO 200 PACT=PP(JJ) GO TO 210 200 CONTINUE C INCREASE BIOMASS BASED ON POT. GROWTH PLUS TEMP. FACTOR 210 GROW= (PGRO*(1.0 + RNUT))*PACT*TE(IT) IF (GROW .LE. 0.0JGO TO 240 A (IC,IT,2)=A (IC,IT,2)*(1.0 + GROW) 240 CONTINUE 245 CONTINUE 52 250 CONTINUE C C LOSSES C C ESTABLISH DAILY LOSS RATE DUE TO CURRENT 260 DO 262 JJ=1,11 KK=JJ+1 IF (CUR . GE. CLT(KK))GO TO 262 CLOS=CL(JJ) GO TO 264 262 CONTINUE 264 IF (CUR .LT. CADV)CLOS=CLOS*CUR/CADV C CHECK IF SPATE CONDITIONS EXIST SPCK=CADV+SPLM isc=o IF (CUR .LT. SPCK)ISC=1 C BEGIN LOOP OVER ALGAL TYPES DO 400 IT=1,3 INUM=ICO(IT) IF (INU« .LE. 0)GO TO 400 C TEMPS ABOVE OR BELOW THRESHOLD TEMPS CAUSE CELL EEATH TE(IT)=1.0 IF (WTEM - TMIN (IT)) 270,265,265 265 IF (WTEM-TMAX(IT))272,271,271 270 TF= (TMIN(IT)-WTEM)**2. TE(IT)=TF*.01 IF (TE(IT) .GT. .25)TE(IT)=.25 TE(IT) = 1.0-TE(IT) GO TO 272 271 TF=(WTEM-TMAX(IT))**2. TE(IT)—TF*.01 IF (TE (IT) .GT. . 25)TE(IT)=.25 TE(IT)=1.0-TE(IT) C INSUFFICIENT CURRENT CAUSES CELL DEATH 272 BCF=1.0 IF (CUR .LT. CMIN (IT) ) BCF= 1.0- ( (CMIN (IT)-CUR) *.01) DO 340 IC=1,INUM C BIOMASS LOSSES DUE TO NORMAL CURRENTS A (IC,IT,2)= A (IC,IT,2)*(1.0-CLOS) *BCF*TE(IT) GO TO (340,273),ISC 273 DO 290 JJ=1,5 KK = JJ+1 IF (A(IC,IT,2) .GE. P(IT,JJ) .AND. A(IC,IT,2) . LT. P (IT, KK) ) SLOS=SL (JJ) 290 CONTINUE C HAT LOSSES DUE TO SPATES A (IC,IT,2)=A(IC,IT,2)*(1-SLOS) 340 CONTINUE C C SORT OUT HULL COHORTS AND CLOSE RANKS C DO 360 JJ=1,INUM IF (A(JJ,IT,2) .GE. COLG)GO TO 360 ICO (IT)=ICO(ITJ-1 ICC=A (JJ,IT,1) 0000001 ICN (IT)=ICN(IT)-ICC 360 CONTINUE G(IT)=0.0 INUM=ICO(IT) IF (INUM.LE.O) GO TO 400 DO 390 IC=1,INUM 53 375 WRITE(5,1)I,IT,IC,A(IC,IT,1),A(IC,IT,2) 1 FORMAT (3X,'DAY',15,« TYPE',13,' COHORT',13,' A1=',F6.2, .« A2=',F10.7) 378 B(I,IT)=B(I,IT) • (A(IC,IT,1)*A(IC,IT,2)) 390 CONTINUE J=I-1 IF (J)100,400,380 380 IF (B(J,IT) . LE. 0.0) GO TO 400 G (IT)=B (I,IT)/B (J,IT) 400 CONTINUE 500 CONTINUE RETURN END COMMON ARTM,PPT,SNO,SMLT,CUR,TIB (3) ,TIT(3),RNUT,WTEM,SUN,SLTE, .A (25,3,2) ,CMIN (3) , CM AX (3) ,TMIN (3) ,TM AX (3) , PM AX (3) ,SPER (16,9) , .P (3,6),PP (5) ,CL (1 1) ,SL (5) ,G(3),TMMX,TMMN,APPT,SNOW,CMOD,GRND, .FNUT,RLEF,GTEM,AMPW,ZMIT,SMIN,SHDE,PI,TPPT,RAIN,ERTE,CIti,TS, .COLG, COLJ?,CADV,SPLM,IBUD,IDRP,KM (3),ICO (3) ,OMEG,IW,IR,I, ,B (365,3) ,RFP (4) ,CII (3) COMMON CLT (12),ICN (3) DO 100 1=1,3 G(I)=0.0 DO 100 J=1,2 DO 100 K=1,25 A(K,I,J)=0.0 100 CONTINUE C BEGIN SIMULATION FOR ONE YEAR DO 200 1=1,365 200 CONTINUE CALL INPT C INITIALIZE RANDOM NUMBER GENERATOR (-1<X<+1) CALL RANDN (123.4567) C ADJUST AIR TEMPERATURE GENERATOR FOR SOLSTICES ON DEC.21 AND JUNE ADD= 2*PI/365. OMEG = (1.5 * PI) + (10 * ADD) DO 300 1=1,365 CALL PHYS CALL ALGA WRITE (5,3)I,CUR,RNUT,WTEM,SITE, (ICN (J),B (I,J),G (J),J=1,3) OMEG=OMEG+ADD WRITE(2,1) (B(I,J),J=1,3) 1 FORMAT (3F10.5) 300 CONTINUE WRITE (5,6)TPPT 400 CONTINUE 3 FORMAT(4X,I3,3F8.2,F8.0,3(2X,I5,F11.5,F5.2)) 6 FORMAT (3X,'TOTAL PRECIPITATION =',F5.2,• INCHES') STOP END 54 APPENDIX B Sample Parameter L i s t . BIG QUALICUM RIVER THMX 25. MAXIMUM DAILY AVERAGE AIR TEMP. (CENT.) (MID-SUMMER) THMN -15. MINIMUM DAILY AVERAGE AIR TEMP. (CENT.) (MID-WINTER) APPT 50. AVERAGE ANNUAL RAINFALL (INCHES) SNOW 2U. SNOW PACK AT START OF SIMULATION (INCHES) CMOD 30. ARBITRARY FACTOR CONVERTING DRAINAGE TO CURRENT GRND .5 GROUND WATER IN DAILY INCHES OF RAIN EQUIVALENT FNUT . 10 NUTRIENT FACTOR RLEF .2 NUTRIENT INCREASE FROM LEAF DROP GTEM 4. TEMP (CENT.) OF GROUNDWATER AMPW 20.0 MAXIMUM TEMPERATURE OF DRAINAGE WATER ZNIT 16. MAXIMUM HOURS OF SUN SHIN 8. MINIMUM HOURS OF SUN SHDE .05 PROPORTION ILLUMINATION IS REDUCED BY PERMANENT SHADE PI 3. 14159 GOOD OLD MATHEMATICAL CONSTANT TPPT 0.0 INITIALIZATION OF TOTAL PRECIPITATION COUNTER RAIN 0.0 STORAGE INFO OF PREVIOUS PRECIPITATION BRTE 8800. FOOT-CANDLES ILLUMINATION ON JUNE 21 AT NOON DIH 5300. FOOT-CANDLES ILLUMINATION ON DECEMBER 21 AT NCON TS .30 PROPORTION ILLUMINATION IS REDUCED BY DECIDUOUS SHADE COLG .001 GRAMS DRY WEIGHT OF NEW COLONIES COLH 5. MAXIMUM NUMBER OF NEW COLONIES PER DAY CADV 20. INITIALIZATION OF AVERAGE CURRENT CALCULATOR SPLM 10.0 LIMIT OF 'TOLERABLE' CURRENT INCREASES IBUD 120 DAY TREES BEGIN TO BUD OUT LD RP 280 DAY TREES BEGIN TO LOOSE LEAVES Ktt-A 170 FOR ALGA A, ILLDM AT WHICH PGRO=.5*PMAX KH-B 100 II II g II II II H n KM-C 20 II II Q n II ti n n CMIN-A 80. MINIMUM CURRENT FOR GROWTH CHIN-B 10. MINIMUM CURRENT FOR GROWTH CMIN-C 1.0 MINIMUM CURRENT FOR GROWTH CMAX-A 100. MAXIMUM CURRENT FOR GROWTH CMAX-B 50.0 MAXIMUM CURRENT FOR GROWTH CMAX-C 30.0 MAXIMUM CURRENT FOR GROWTH TMIN-A 4. MINIMUM TEMPERATURE FOR GROWTH TMIN-B 6.0 MINIMUM TEMPERATURE FOR GROWTH TMIN-C 8.0 MINIMUM TEMPERATURE FOR GROWTH TMAX-A 10. MAXIMUM TEMPERATURE FOR GROWTH TMAX-B 15.0 MAXIMUM TEMPERATURE FOR GROWTH TMAX-C 20.0 MAXIMUM TEMPERATURE FOR GROWTH TIB—A 300. THRESHOLD (MIN. ILLUMINATION FOR PHOTOSYN.) TIB-B 100. 1 1 1 1 1 - 1 1 5 t TIB-C 50. 1 1 t I I 1 8 0 TIT-A 4000. THRESHOLD (ILLUMINATION AT WHICH PHOTO INHIBITION STARTS) TIT-B 3000. THRESHOLD (ILLUMINATION AT WHICH PHCTO INHIBITION STARTS) TIT-C 2000. THRESHOLD (ILLUMINATION AT WHICH PHOTO INHIBITION STARTS) PMAX-A .117 POTENTIAL MAX. PROPORTION INCREASE PER HOUR PMAX-B .09 POTENTIAL MAX. PROPORTION INCREASE PER HOUR PMAX-C .07 POTENTIAL MAX. PROPORTION INCREASE PER HOUR RFP-WIN .30 PROPORTION OF ANNUAL RAINFALL THAT FALLS IN WINTER RFP-SPR .40 PROPORTION OF ANNUAL RAINFALL THAT FALLS IN SPRING RFP-SUM . 10 PROPORTION OF ANNUAL RAINFALL THAT FALLS IN SUMMER RFP-AUT .20 PROPORTION OF ANNUAL RAINFALL THAT FALLS IN AUTUMN CII-A 6000. COLONIZATION ILLUMINATION INDEX 55 CII-B 5000. COLONIZATION ILLUMINATION INDEX CII-C 3000. COLONIZATION ILLUMINATION INDEX SPEB .18 .40 .84 1.0 .84 .40 .18 .0 SPER .10 .25 .50 .85 1.0 .85 .50 .25 .10 .0 SPER .15 .30 .60 .86 1.0 .86 .60 .30 .15 .0 SPER .10 .20 .40 .66 .87 1.0 .87 .66 .40 .20 .10 .0 SPER .15 .30 .50 .75 .88 1.0 .88 .75 .50 .30 .15 .0 SPER .10 .20 .35 .55 .77 .90 1.0 .90 .77 .55 .35 .20 .10 .0 SPER .15 .30 .43 .60 .78 .92 1.0 .92 .78 .60 .43 .30 .15 .0 SPER .08 .18 .36 .50 .65 .79 .92 1.0 .92 .79 .65 .50 .36 .18 .08 .0 SPEB .10 .23 .42 .55 .70 .80 .96 1.0 .96 .80 .70 .55 .42 .23 .10 .0 P-A 0.00 0.30 1.00 5.00 1000.9999. SIZE PARAMETERS P-B 0.00 0.10 0.40 1.00 10.0 1000. SIZE PARAMETERS P-C 0.00 0.50 2.50 10.0 50.0 1000. SIZE PARAMETERS PP 1.0 0.64 0.40 0.25 0.10 ACTIVE PORTIONS FOR EACH SIZE COLON SL 0.0 .05 .10 .40 .80 PROPORTIONS OF SPATE LOSSES CL .02 .06 .13 .18 .24 .28 .32 .35 .38 .45 .50 CURRENT LOSSE: CLT 0.0 20. 30. 40. 50. 60. 70. 80. 90. 100. 120. 9999. 

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