6- 



Modeling 449 



Pond A 1973 



June 



July 



August 



FIGURE 10-5. Model simulation and 

 measured estimates (black circles) of 

 net photosynthesis of the benthic 

 algae. The data are for rates at 1200. 

 (After Stanley 1974.) 



(year to year) light and temperature. Although the behavior of all the state 

 variables of the model have been simulated and the output data have been 

 compared with the field observations, we present here the behavior of only 

 one variable from each of the three major categories — primary producers, 

 consumers and decomposers. 



Figures 10-3 and 10-4 depict the seasonal trend in the biomasses of 

 benthic and planktonic algae populations. In these figures experimental 

 data are also included for a comparison. There is excellent agreement 

 between the simulation and the field data. For the best studied case, the 

 photosynthesis of the benthic algae (Stanley 1976a, 1976b), the parameters 

 were measured in 1973 and tested against the photosynthesis measured in 

 1971, 1972, and 1973. Figure 10-5 shows the measured and simulated 

 values of net photosynthesis for benthic algae. 



Daphnia and chironomid biomasses are given in Figures 10-6 and 10- 

 7. Daphnia in the water and chironomids in the sediment are the main 

 consumers and they account for about 90% of the biomass of the consumer 

 population of this system. 



