Computer program used to estimate primary productivity from pH and carbon dioxide data employing the upstream--downstream method [report]

E.G. Wolf, R.J. Olson
1974 unpublished
oxygen (Odum 1956 ) and the more recent ups tream-downstream method (Odum 1956) . Each o f these methods i s adaptable t o -i n s i t u a n a l y s i s b u t t h e d i u r n a l curve and the upstream-downstream methods can be used i n s i t u w i t h o u t a l t e r i n g t h e n a t u r a l system. The o t h e r methods e i t h e r -i n t r o d u c e some component t o the system ( N~H~ 4~0 3 , enclosing b o t t l e s ) o r remove e s s e n t i a l envi ronmental f a c t o r s ( f l o w , n u
more » ... r s ( f l o w , n u t r i e n t replenishment). These elements become s i g n i f i c a n t when studying l o t i c systems (Odum 1957). Any method which w i l l d e l e t e these v a r i a b l e s provides a c l o s e r estimate o f t h e t r u e p r o d u c t i v i t y o f t h e system. The use o f the upstream-downstream method and the conversion o f pH t o carbon d i o x i d e i n freshwater systems has been thoroughly documented by R. J. Beyers -e t a l . (1963) and H. T. Odum (1957). T h e i r studies a l s o i n c l u d e d t h e adaptation o f t h e method t o computer analysis. I n t h e f o l l o w i n g sections i s a d e s c r i p t i o n o f t h e program as adapted from t h e o r i g i n a l program o f Beyers -e t a1 . (1 963). The program was m o d i f i e d t o i n c l ude mu1 ti p l e s t a t i o n sampl i n g and t o i n t e r p o l a t e readings t h a t do n o t occur a t h o u r l y i n t e r v a l s . The program also u t i l i z e s mathem a t i c a l equations f i t t e d t o t h e carbon dioxide-pH conversion data (Wolf e t a1 . 1971 ) . Method o f Computation The basic equation f o r t h e upstream-downstream method f o r e s t i m a t i n g p r o d u c t i v i t y can be i 11 u s t r a t e d as f o l 1 ows ( A f t e r , Odum 1956) Q = P R -D o u t + A Q = r a t e o f change o f carbon d i o x i d e p e r area P = r a t e o f gross primary production p e r area R = r a t e o f r e s p i r a t i o n p e r area Do"t = r a t e o f carbon d i o x i d e d i f f u s i o n o u t o f the system p e r area A = r a t e o f accrual The a p p l i c a t i o n o f t h i s formula t o computer analysis i s o u t l i n e d i n proceeding steps: 1. The pH values from the sampling s t a t i o n s a r e read i n and converted t o m i l l i m o l e s C02. This conversion i s accomplished w i t h data obtained t i t r a m e t r i c a l l y as described by R.J. Beyers e t a1 . (1 963). The mathematical equation f o r t h i s conversion was-6ui 1 t i n t o t h e computer program. 2. O f f s e t the pH values f o r the downstream s t a t i o n by t h e average f l o w time. Flow times can be estimated r e a d i l y using dyes, r a d i onucl ides o r s a l t s as t r a c k i n g agents. 3. Accrual c o r r e c t i o n i s t o a d j u s t t h e upstream o r downstream C02 values t o account f o r any a d d i t i o n o f C02 t o t h e study area. The mathematical expression Ac = [S (F) + C]/F + 1.0 i l l u s t r a t e s t h e c o r r e c t i o n where Ac = accrual corrected C02 values f o r t h e upstream s t a t i o n , S = t h e C02 concentration a t t h e upstream s i t e , C i s the C02 l e v e l o f the accrued component and F i s the accrual f a c t o r . This f a c t o r i s derived from t h e r a t i o o f t h e volume o f f l o w c o n t r i b u t e d by t h e two components; i.e., t h e accrued drainage and t h e f l o w i n t o t h e study area. This value o f t e n i s n e g l i g i b l e and no c o r r e c t i o n i s necessary (Odum 1956). 4. M i 11 in101 es C02/1 a r e converted t o gm co2/rn2; i .e. , m i 11 imol es * 44 * mean depth o f study area. 5. Correct C02 values f o r d i f f u s i o n . This c o r r e c t i o n i s accomplished through a v a r i e t y o f methods, many o f which have been discussed by Odum (1956). The method used i n t h i s program i s where D i s t h e d i f f u s i o n corrected C02 values f o r t h e downstream s t a t i o n , A i s the accrual corrected upstream C02, B i s t h e downstream COz, C = t h e s a t u r a t i o n constant, K = t h e gas t r a n s f e r c o e f f i c i e n t and F i s t h e f l o w t i m e between the two sampling s t ati ons. 6. Subtract t h e dahnstream CO data from t h e upstream values and d i v i d e b y t h e average f l o g time between the two s t a t i o n s . T h i s f i n a l step y i e l d s p o s i t i v e and negative values. The p o s i t i v e values represent gms per hour comnunity r e s p i r a t i o n w h i l e t h e negatives are gms per hours n e t p r o d u c t i v i t y . T h i s program was a l s o w r i t t e n t o i n t e g r a t e t h e r e s p i r a t i o n and p r o d u c t i v i t y values t o o b t a i n subsequent d a i l y values f o r p r o d u c t i v i t y and r e s p i r a t i o n , average p r o d u c t i v i t y and r e s p i r a t i o n p e r hour. A summary s e c t i o n o f t h e program a l s o permits t h e i n t e g r a t i o n o f t h e data over an annual p e r i o d and t o t a l p r o d u c t i v i t y o f t h e stream discharge volume p e r hour. The program was w r i t t e n f o r a LINIVAC 1108 computer using t h e FORTRAN l e v e l 5 language. Data Card Format The data form (page 6) i s s e t up t o r e c o r d pH readings d i r e c t l y from a s t r i p c h a r t r e c o r d e r w i t h one day recorded p e r form. The t i m e of t h e f i r s t r e a d i n g i s recorded and times o f subsequent readings f o r each s t a t i o n a r e c a l c u l a t e d based on t h e c y c l e t i m e o f t h e recorder. The program then i n t e r p o l a t e s between t h e readings o f each s t a t i o n t o o b t a i n h o u r l y values. Factors f o r t h e various c o r r e c t i o n s and conversions a r e read from cards i n t h e STREAM2 program. Output The f i n a l r e p o r t c o n s i s t s o f a one page summary f o r each day presenti n g pH values, C02 values and i n t e g r a t e d production. A t y p i c a l r e p o r t i s presented on page 7. Summary The program, as reproduced here, represents t h e i n i t i a l e f f o r t s by
doi:10.2172/4285626 fatcat:fxewy7i5vvdqvmsclyl4g3k5hy