444 J. L. Tiwariet al. 



populations into groups based upon phyla (green, blue-green, etc.). We 

 would have liked to be able to have a number of physiological groups in 

 this model and tried to obtain information from autoradiography on the 

 half-saturation constants for nutrient uptake or light responses; these 

 measurements were not completely successful (Chapter 5). The rate of 

 photosynthesis is modeled as a function of algal biomass, light, 

 temperature, and phosphorus concentration (RPI). As discussed earlier 

 the functional form of the effects of light and phosphorus on the rate of 

 photosynthesis is a Michaelis-Menten type equation. Experimental 

 observations (Stanley 1974) indicate that the magnitude of the half 

 saturation constant (C29) in the light function is influenced by' 

 temperature. Thus, this quantity is multiplied by a Qio function. 

 Furthermore, the Qio type of temperature function can independently 

 influence the rate of photosynthesis. The experimental data of Stross 

 indicate that the photosynthetic capability in these algae is rhythmic and 

 hence V,„ax is represented as an oscillatory quantity with a mean of 0.06 

 mg C (mg algal C) " ' hr " ^ and an amplitude of 0.002. 



The loss of carbon from algae is due to death (RP9) and excretion of 

 U-DOC (RP5). It is assumed that a constant fraction of the biomass is lost 

 due to these processes. Furthermore, the algae are also transferred to the 

 bottom of the pond by burial, which is facilitated by the settling of large 

 detrital particles (RPI 7) (Rublee 1974). 



Carex aquatilis and Arctophilafulva grow in the shallow areas of the 

 ponds. Carex, in particular, is amphibious and is a part of the carbon cycle 

 of both the aquatic and terrestrial systems. It has been studied and 

 modeled in detail by the investigators of the terrestrial section of the 

 Tundra Biome (see Brown et al. in press). Therefore, no attempt has been 

 made to duplicate that work. Nevertheless, for the sake of completeness 

 we have included some equations to describe the input from these plants. 

 One equation gives the growth rate in terms of a gross photosynthesis rate 

 (RP301). The losses from this box are due to respiration (RP302), 

 excretion of U-DOC (RP303), and death (RP304). 



Consumers 



Though there are several consumer species in the ponds (see Chapter 

 6, Zooplankton), Daphnia and fairyshrimps are dominant and account for 

 more than 95% of the total consumer biomass. Because of the major role 

 of these two species in the carbon dynamics of these ponds, we have 

 included them in the plankton model. 



In the early part of the season, Daphnia are inactive. After the first 

 week these organisms hatch and begin feeding on algae, bacteria and 

 detritus present in the water column. Daphnia are parthenogenetic and 

 start producing young after 3 weeks. These second generation organisms 



