The zonal changes in the composition of the tropical zooplankton are 

 related to these regularities. Although in equatorial communities, areas 

 may be found without upwelling of water, on the whole upwellinq pre- 

 dominates in these communities. Therefore, in the Pacific Ocean, within 

 the equatorial region, an increase was observed in comparison with the 

 central regions in the relative quantity of Gymnoplea. 



In the Indian Ocean, areas with predominance of filter feeders are 

 also found within the equatorial community. The central regions are 

 characterized by stable water stratification or water sinking, upwelling 

 being rare and weakly expressed. Therefore, within the central community 

 of the Indian Ocean, between 20 and 29°S, A. G. Timonin found small 

 quantities of herbivorous filter feeders and relatively larger quantities 

 of predators in all locations. 



In the Pacific Ocean on the equator between 95 and 160°W, a population 

 which did not fit into this system was found (Vinogradov, Semenova, 1975; 

 Flint, 1975). In spite of clear upwelling of water and abundant plankton, 

 the upper 200 m was dominated by predators, which composed about 60% of 

 the biomass. Toward the west, as the upwellinq of water weakened and 

 the biomass of plankton decreased, the relationship of the trophic groups 

 remained essentially the same. As yet, no satisfactory explanation for 

 this has been found, but this composition of the population is not typical 

 for the broad oceanic tropical regions. 



Around the peripheries of the tropical area, the relative quantities 

 of Tunicata increase, particularly the Salpidae and Pyrosoma (Heinrich. 

 1964, 1968). These are filter feeders with a broad diet. This regularity 

 is seen in all oceans. An increase in the quantity of Salpidae has also 

 been noted in certain inshore regions in the lower latitudes and in zones 

 of upwelling of water (Yount, 1958; Russell, Colman, 1935; Rao et al . , 

 1973; Gordeeva, Shmeleva, 1971; Gruzov, 1971). There are insufficient 

 data for comparison but, apparently, at least in the open ocean, these 

 swarms are less frequent and not as great as in the peripheral tropical 

 areas. 



In the distant neritic communities of the eastern boundary currents 

 the relative quantity of Copepoda is great, clearly dominated by the 

 coarse filter feeders, both herbivores and omnivores, while predators 

 are few. For example, in the Peru Current, according to M. E. Vinogradov 

 and T, N. Semenova (1975), predators represent less than 10% of the 

 biomass. In the Benguela Current, the large herbivorous and omnivorous 

 Copepoda represent 80-95% of the biomass (Andronov, 1971). In the 

 California Current, in a region of upwelling water, predominance of 

 coarse herbivorous filter feeders (Copepoda and Decapoda Pleuroncodes 

 p lanipes ) is also seen. With increasing distance from the coast, toward 

 the central waters, the relative number of predators increases (Longhurst, 

 1967). 



The zooplankton of neritic communities is usually dominated by the 

 Copepoda. These are most frequently small Copepoda, herbivores or 

 omnivores. One significant feature of the trophic structure of many 



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