development, with the maximum of phytoplankton,* while further downstream 

 in the current we observe the maximum of herbivorous zooplankton, which 

 requires more time for its development, and still further from the upwelling 

 zone we find the maximum of predators (Vinogradov et al . , 1961; Vinogradov, 

 Voronina, 1954; Vinogradov et al . , 1972; Timonin, 1971; Gueredrat, 1971). 

 Consequently, the maxima of the biomass of the various groups, which require 

 various lengths of time for their development, do not coincide in space 

 (Chapter II, Fig. 3). 



The spreading of zones of predominance of various trophic groups 

 in space, accompanied by differences in number, biomass, dimensions and 

 vertical distribution of plankton, allows us to look upon the individual 

 stages in the development of the system as independent communities. Some- 

 times, this approach facilitates the study of the communities (Timonin, 

 1971; and others), since it allows us to ignore the degree of intermixing 

 of the various communities with each other. However, obviously, we should 

 always keep in mind that we are in fact analyzing and comparing not 

 steady-state pictures, but rather individual frames from a continuous 

 dynamic process. 



The pelagic tropic communities require at least one or two months to 

 achieve the comparatively mature state characteristic of the ol igotrophic, 

 halistatic areas in the central waters of the ocean. During this time, the 

 community is carried by currents hundreds of miles from the region 

 where it was formed by the upwelling of the water. 



Actually, in the tropical ocean, the water of various streams of 

 currents and the communities which it carries has significantly different 

 "age." Therefore, there is a constant, more or less intensive, mixing of 

 communities of varying degrees of maturity. Correspondingly, the 

 picture of development of a community which we have studied, and for which 

 quantitative mathematical models have been constructed (Vinogradov et al . , 

 1972: Vinogradov et al . , 1973) is rather idealized. In actual fact, the 

 whole process is much more complex. First of all, the flow of water from 

 the upwelling zone does not form an integral whole. At various depths, 

 layers of water move at different speeds and in different directions. 

 Secondly, the picture which we have presented of the "primary" succession in 

 the ocean is rarely actually observed. It has been seen, for example, off 

 the coast of Peru, near southwest Africa and in certain other regions of 

 particularly intensive upwelling of water. Usually, however, the researcher 



*If the rise occurs at 10"3-10"'^ cm/s or somewhat greater, i.e., if 

 the water rises by decimeters or meters per day, then a thermocline can form 

 directly at the point where the water rises, and a phytoplankton bloom is 

 observed. A bloom can develop in the rising water in three or four days 

 (Smith et al . , 1971: Strogonov, Vinogradov, 1975; and others). The more rapid 

 the rise of the water, the closer to the surface the thermocline forms; 

 if the rise is particularly rapid, for example, in the Peruvian upwelling, 

 the water may rise tens of meters per day (Smith et al . , 1971), the 

 phytoplankton cannot reach its maximum development at the point where 

 the water is rising, and the maximum is formed downstream from the point 

 of the water ascent. 



15 



