The influence of the zone of Antarctic divergence is significantly 

 weaker, and changes from season to season. In the winter, relatively 

 rich plankton accumulates here, yielding the maximum spawning pool. 

 Numerous juveniles appear in spring, moving northward with the surface 

 water, forming easily visible "spots" (Voronina, 1968). The divergence 

 influences the distribution of various species differently. Among the 

 mass copepods, the greatest concentrations are observed for R. g igas , ap- 

 parently due to the fact that it spends the winter in the higher layers, 

 where the velocities of the currents are greater than in those inhabited 

 by C_. acutus and C. p ropinquus . 



Let us sum up our information on zoocenes. Their basic specifics 

 are: low specialization of the most numerous species: absence of any 

 attachment to definite depths or water masses, broad feeding spectra; 

 relationship of periods of breeding and feeding of juveniles to periods 

 of abundant phytoplankton, as a result of which most species in the 

 Antarctic are monocyclic, in the Subantarctic, apparently, bicyclic; 

 significant plasticity of the life cycles; a delay in identical stages 

 of'cycles in the southern latitudes in comparison to the northern 

 latitudes; complexity of the picture of quantitative distribution of 

 individual species, depending on both temporal and local factors. 



4.3 Communities . 



Specific and trophic structure . The number of species in the pelagic 

 zone of the Subantarctic, and particularly the Antarctic, waters is 

 significantly less than in the tropics. Why is this? 



The biotopic variety in the temperate and polar waters in the summer, 

 is no less than in the tropics. There are: surface film, an upper mixed 

 layer, a residual layer of winter cooling and two thermoclines separating 

 it from the waters above and below. However, the autumnal mixing disrupts 

 this stratification, and the time of its vernal restoration is variable. 

 As a result, ascending populations, at the same time but at different 

 places, may encounter completely different situations: from complete 

 homothermy of the surface water mass to well-developed stratification, 

 from winter shortage of algae to rather abundant bloom. This factor, 

 apparently, greatly hinders the adaptation of the fauna to the specific 

 conditions of existence. As a result, neither food specialization of 

 herbivores, i.e., adaptation to individual stages of succession of phyto- 

 plankton, nor spatial divergence occurs. As a result of this, the variety 

 of species in the population is not great. The relationship between low 

 specific variety of communities and unpredictability of temporal changes 

 in the environment is well known (Margalef, 1968; Slobodkin, Sanders, 1969). 

 For the pelagic zone, where the primary consumers of phytoplankton are 

 located beyond the producing layer for a long time, this factor should 

 have particularly great significance. Another factor in the low variety of 

 the population of the higher latitudes may be the brevity of the period 

 of vegetation of the algae (Heinrich, 1962). In the plankton of the 

 Southern Ocean, phytophagous forms are clearly dominant, their biomass 

 in the upper 100 meter layer representing an average of 82%. in places 

 as much as 96% of the total. The zoophagous animals, the prey of which 



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