cannibalism are considered analogously (coefficients y. , y„ and y^). 

 The natural mortality of the zooplankton ( e) and rate of vertical 

 migrations (w„) are also considered. 



It is assumed that detritus is formed from dying zooplankton, and 

 also from zooplankton excreta, the quantity of which is proportional to 

 the quantity of food consumed (coefficients 6 , 6 , 6 ). The 

 phytoplankton does not die, but is completely consumed by the 

 zooplankton. The decomposition (g) and settling (cijo) of the detritus 

 are considered. The dissolved compounds of nutrients, phytoplankton, 

 zooplankton and detritus are carried in the vertical direction by 

 turbulent diffusion, the intensity of which is described by coefficient 

 K. The depth axis z is assumed to be directed from the surface of the 

 water downward. 



The systems of equations of the model are therefore: 



3Z 



I (a + a^p + a2f + ajd). (1.2) 



3nN a 3nw 



-3t = -^NPpP^ V ^ ^(K-^)- (1-3) 



3nn a 3nn 



= YlPf - V'^ V^ -ef ^-3|(Kf) -^(.^f). (1.6) 



ud + 6ipf + 62f2 + -^ (K If) - ^ (u)3d). (1.7) 



Figure 1 presents a schematic diagram of one cell of the model. 

 The symbols used in the figure will be retained throughout this entire 

 section and serve as a language for the description of the structure of 

 the model of an aquatic ecologic system. 



1.2 Model Simulating the Vertical Distribution of Elements of an 

 Ecosystem 



The results of investigations carried out during the 44th and 50th 

 cruises of the VITYAZ' forced us to revise the model of A. A. Lyapunov 

 (Vinogradov et al., 1972; Vinogradov et al., 1973). The establishment 

 of a significant role of bacteria in the process of energy transfer and 

 the cycle of matter in the pelagic ecosystem (Sorokin, 1971a; and 

 others) forced a new structural element to be added to the model -- 

 bacterioplankton. At the same time, it became necessary to consider the 

 transfer of energy from phytoplankton to bacteria by means of dissolved 

 organic matter (DOM). It was assumed that the excretion of DOM by 

 phytoplankton represented 30% of its production. The intensity of 



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