between the elements of the community which are distinguished, 

 nutritional selectivity coefficients are selected and the increase in 

 weight (production) per unit of time (per day) is described for each of 

 the elements distinguished: 



dWi _i 



-^= CiUi' - Ri (3.5) 



It is desirable to consider how the assimilation Uj is influenced 

 by the degree of trophicity of the waters, membership in a predaceous or 

 peaceful level of zooplankton, as well as the variation in the daily 

 diet Cj as a function of concentration of food (Ivlev, 1955; Jergensen, 

 1955; Petipa, 1967; Winberg Anisimov, 1969; Petipa et al . , 1971). The 

 assimilation of the food U"^ = (P + R)/C, apparently depends to some 

 extent on the trophicity of the water, i.e., on the concentration of 

 food, and decreases with increasing food concentration (Jergensen, 1955; 

 Klekowski et al . , 1966; Petipa et al . , 1971, 1974). It is thought that 

 the minimum value of assimilation U"j , with an abundance of food, is 

 near 0.4 (Winberg et al., 1965; Klelciwski, Shushkina, 1966; Klekowski, 

 et al . , 1972; Petipa et al . , 1975). For carnivorous animals, the 

 assimilation of food is usually higher than for herbivorous animals 

 (Soldatova et al . , 1969; Monakov, Sorokin, 1972; Winberg, 1973). The 

 mean value of assimilation for herbivores can be assumed to be close to 

 0.6 (Conover, 1966; Sushchenya, 1975), for predators--0. 7-0.8. 



The rate of metabolism R^- is determined experimentally by the 

 method of Winkler or by a polarographic method for animals of each 

 element in the community (Shushkina, Pavlova, 1973; Muscaeva, Vitek, 

 1975; Klekovskiy et al . , 1975). All of the ecologic-physical indices 

 included in equation (3.5) are expressed in calories. 



It is assumed that the radiocarbon label introduced with the 

 labeled phytoplankton to the portion of the planktonic community 

 isolated in the water bottle is distributed among the elements of the 

 community according to equation (3.5), which allows us to determine the 

 radioactivity of the organisms C^-/W-j individually as a function of time 

 and use it as a control to estimate the reliability of the parameters 

 used in the model (Shushkina et al . , 1974; Shushkina, Kislyakov, 1975). 



We can also use the method of mathematical modelling based on 

 equations (3.1-3.5) and the parameters which they include, in 

 combination with physiologic methods, to estimate the rate of production 

 of individual trophic levels of zooplankton and calculate the net 

 production of zooplankton and of the planktonic community as a whole 

 (Vinogradov et al . , 1976). In estimating the intensity of production of 

 populations of aquatic animals and individual trophic groups (levels) 

 using the balance equation (3.5), we must have some idea of the spectrum 

 of feeding of the animals studied, their trophic connections, rates of 

 consumption of food C and its assimilation U"^ as a function of the 

 concentration of the food. These parameters are rather well known for 

 fresh water, less well known for marine planktonic communities, 

 particularly in the tropics. Nevertheless, the experimental and field 



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