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In many tropical neritic communities, in contrast to the oceanic 

 communities, the trophic relationships of phytoplankton and herbivores 

 are essentially unbalanced (Heinrich, 1970) for long periods of time. 

 The phytoplankton is abundant and underutilized. The fluctuations in 

 quantity of phytoplankton are great. Along the west coast of India, e.g., 

 the number of algae during the maximum exceeds their number during the 

 minimum by a factor of 150 (Subrahmanyan, 1959), and the maximum mean 

 monthly biomass of algae in the Gulf of Panama is 57 times greater than 

 the minimum one (Smayda, 1966). The ratio of the quantity of phytoplankton 

 to the quantity of zooplankton in the Gulf of Panama varies from 0.04 to 

 980, averaging 83, and at times reaches ratio characteristics for boreal 

 communities (Smayda, 1956). Based on the calculations of this author, 

 the daily rate of grazing of phytoplankton by herbivores is only 20-44% of 

 the daily primary production. 



The weak balance of trophic relationships in neritic tropical 

 communities in comparison to oceanic communities is explained first of 

 all by the instability of environmental conditions, the strong but 

 inconstant enrichment with nutrients as a result of upwelling of water 

 and runoff from the land. In places where, as at the Great Barrier Reef, 

 the mixing regime is constant, and there is no runoff from the land, the 

 quantity of phytoplankton is low and its fluctuations are slight throughout 

 the year (S. M. Marshall, 1933). Furthermore, neritic communities have 

 a simpler structure than oceanic communities (smaller number of species, 

 with relatively strong dominance of a few species, predominance of short 

 food chains). This reduces the possibilities of regulation of trophic 

 relationships of the organisms and thereby facilitates instability in 

 the production cycle. 



The distant neritic communities in the eastern boundary currents 

 are, like the neighboring neritic communities, under the influence of 

 strong upwelling of variable intensity. Some of the nutrients and 

 phytoplankton may reach there due to advection from neighboring neritic 

 regions. These regions are dominated by large herbivorous Copepoda, while 

 herbivorous fishes are not of essential significance. In the California 

 Current, Pleuroncodes planipes is abundant both in the neritic and in 

 the distant neritic region (Blackburn, 1959). Changes in the intensity 

 of upwelling of water during the course of the year lead to alternation 

 of oligotrophic and eutrophic periods and changes in the trophic relation- 

 ships in the community (Gushing, 1971). For example, in the Peru Current 

 in September-November, phytoplankton is consumed in the regions off the 

 shelf quite intensively, while in June there is much less zooplankton, 

 and the consumption of phytoplankton has been estimated to be less than 

 10% of its daily production (Beers et al . , 1971; Heinrich, 1974b; Rat'kova, 

 1975). Significant seasonal changes also occur in the California 

 Current (Walsh et al . , 1974). 



The greatest changes in trophic relationships should occur when a 

 period of relative stability is replaced by a period of upwelling of water, 

 and vice-versa. Apparently, at the beginning of upwelling of the water 

 one can expect a delay in grazing and underutil ization of phytoplankton, 

 particularly since these regions are dominated by relatively large, slowly 

 developing Copepoda. Probably, in these communities the underutil ization 



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