A comparison of the distribution of elements of the model with 

 observed data in the equatorial portion of the east Pacific (Vinogradov, 

 Voronina, 1963; Voronina, 1964; Blackburn et al . , 1970) shows 

 qualitative agreement of the distribution of phyto- and zooplankton in 

 the model and in the field. The decrease in the concentration of 

 phytoplankton to the west as we move along the equator appeared rather 

 clearly in the model, in spite of its approximate nature. The maximum 

 of predaceous zooplankton in the area of the convergence at 5°N is also 

 noted in the model although another maximum of carnivores, on the 

 equator between 150 and 160°W, is almost not reflected in the model. It 

 is possible that this is related to the elevated values of horizontal 

 flow speeds in the model, or to the fact that only predators with 

 characteristic dimensions of not over 10 mm were analyzed. 



This model, despite its extreme sketchiness and the qualitative 

 nature of results produced, demonstrates the genuine possibility of 

 creating 3-dimensional models of pelagic ecosystems in the ocean. 

 However, the experience of development of models of this type has shown 

 that there are significant difficulties. First of all, clarification of 

 the 3-dimensional field of the velocity vector of a current, even for 

 steady conditions, is a complex, cumbersome and, at the present time, 

 sometimes impossible hydrophysical task. Secondly, to ignore processes 

 of turbulent transfer, as this model does, is possible only as a first 

 approximation. Consideration of horizontal and vertical turbulent 

 transfer, however, would introduce new complications. In 3-dimensional 

 models, consideration of the active movements of zooplankton and, 

 particularly nekton, becomes extremely necessary, greatly complicating 

 them in comparison to 1-dimensional and plane models. 



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