Pp = P'p(l - lOO.l nN)0.6, (1.12) 



and has the same sense as the Michael is-Menten equation. 



In addition to limitations as to light and concentration of 

 nutrients, the limitation of production of phytoplankton resulting from 

 the maximum breeding rate was also considered. 



In describing the hydrological situation, a three-layer model was 

 used. In the surface layer (0 < z < z-,), high coefficients of turbulent 

 diffusion were assumed: in the pycnoctine (z^ < z < z^) the coefficient 

 of turbulent diffusion decreased rapidly, and only at greater depths (z 

 > z^) did the intensity of mixing increase once more. The values of z^ 

 and Zo, defining the depth and thickness of the discontinuity layer are 

 assumed in the model to be dependent on the time of development of the 

 ecosystem (see Fig. 3). 



The rate of natural descent of the phytoplankton (co, ), bacteria 

 (a)„) and detritus (w_) are assumed to depend on the density of the 

 water, which is determined by the vertical distribution of temperature 

 and salinity. 



Vertical migrations of a part of the zooplankton were simulated in 

 the model so that the food requirements of the elements (f4, Sj^, Sp, S3) 

 inhabiting the 0-50 m layer are supplemented by a certain portion (K™) 

 of the total food requirements of the same elements located in the 50- 

 150 m layer. 



A schematic diagram of one cell of the model is shown in Figure 2, 

 its spatial arrangement--in Figure 3. A water column was considered, 

 extending from the surface to a depth of 200 m and divided into 20 

 elementary 10-meter cells. The relationship between cells located 

 vertically one above the other was determined by the penetration of 

 light (a), turbulent diffusion (k), sinking rate of phytoplankton (w ) 

 and of detritus (w^). The daily input of light energy from the surface 

 of the ocean (Iq) and the concentration of nutrients at 200 m depth 

 (C2qq) were assumed constant. 



The horizontal displacement of the column of water was assumed to 

 occur under the influence of a constant current with uniform 

 distribution of velocity with depth. Vertical transfer of the water was 

 by turbulent diffusion. 



Under these assumptions, it becomes possible to replace the 

 horizontal displacement of the water column containing the simulated 

 ecosystem being modelled with the time of existence of the ecosystem 

 from a certain initial state. In our case the initial state 

 corresponded to the moment of ascent of the deep waters in the upwelling 

 area. 



It was assumed that in the initial state (t = 0) , all elements of 

 the simulated system were evenly distributed with respect to depth. The 

 study of the model showed little sensitivity of the system to the 



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