juvenile Euphausiacea , etc. 



Many experimental data on the variation in the intensity of feeding 

 of zooplankton with concentration of available food density forced us to 

 abandon the plan of Vol 'terra and begin use of the equation of V. S. 

 Ivlev (1955). According to this equation, the relationship between the 

 actual ration (C) and concentration of food (B) can be represented as: 



C = Cn,axCl-e-?(B-B0)], (1.8) 



where C„,^ is the maximum ration; Bn is the minimum concentration of 



mdx ,  1 . u . - - . . 

 food, below which consumption ceases; C is a coefficient. 



In establishing the selectivity of feeding in those cases when 

 direct experimental data were not available, it was hypothesized that 

 the concentration of a given type of food is proportional to its 

 fraction in the actual ration. The mean daily rations (C) were 

 calculated by the equation: 



C = H + P + R = ■g(P + R), (1.9) 



where H is the unassimilated food, P is the production, R is the rate of 

 metabolism, U is the efficiency of assimilation. The values of R and U 

 were determined directly in experiments (Shushkina, Vilenkin, 1971; 

 Shushkina, Pavlova, 1973; Petipa et al., 1971; and others). The mean 

 daily production was calculated by the equation: P = RKo^l - Ko), 

 where K2 is the coefficient of assimilated food used up for growth. 



The equations related to the functioning of phytoplankton in the 

 pelagic community were significantly refined, in comparison to the model 

 of A. A. Lyapunov. An empirical ration was established (Voytov, 

 Kopelevich, 1971) between the concentration of phytoplankton and 

 detritus in the water and the light attenuation factor, which makes 

 equation (1.2) more concrete: 



a = 0.01 + 0.001(p + d). (1.10) 



According to Ryther (1956), the variation in the intensity of 

 photosynthesis with light flux I can be expressed as follows: 



(I ^ ) 

 P'n = Pmax^r-^ "^ , (l.H) 



p " f^max" 



opt 



where Iqp^ is the light flux at which the maximum photosynthesis P^,^^ is 

 achieved. This relationship can be replaced by the following equation, 

 which is closer to the empirical data: 



326 



