a 



communities is characteristic. The foraminifer fauna in the Pacific 

 Ocean is richest in the equatorial community, while the greatest number 

 of species of euphausiids is observed in the central community. The 

 Siphonofora in the Atlantic (Margulis, 1972, 1974) and Indian (Musaeva, 



1973) Oceans, as well as the salps in the Atlantic Ocean (Kashkina, 



1974) have the greatest number of species in the equatorial and distant 

 neritic communities, rather than in the central communities. The increase 

 in the number of species in communities of a certain type is preserved 

 at least for the chaetognaths in all three oceans. 



In the transient communities between the high-latitude and tropical 

 communities, the number of species in all groups is low, in spite of the 

 simultaneous presence of species of different origins, a result of the 

 gradual impoverishment of the fauna toward the periphery of the tropical 

 community. Within the tropical community, the faunistically richest 

 areas are also located in the central, equatorial and distant 

 neritic communities, not in the transient zones between them. The 

 transient biotopes are not favorable for many species from the neighboring 

 communities; therefore, the mixing does not produce enrichment of the faun._ 

 in these zones. In the neritic regions, the number of species of planktonic 

 animals is less than in the oceanic ones (Heinrich, 1952; Bowman, 1971). 



The tropical oceanic plankton is distinguished by a relatively low 

 dominance of individual species. The dominance varies from season to 

 season and from region to region. In the Indian Ocean, the dominance 

 among copepods increases from regions with stable water stratification 

 or with feebly marking water sinking toward regions with upwelling of 

 water, while species diversity of filtering copepods (based on biomass 

 using the formula of Shannon), conversely, decreases (Timonin, 1969, 

 1972). Thus, in zones of upwelling of water, 75?. of the biomass of 

 Calanoida is accounted for by three species, while outside the upwelling 

 zones, the five or six most numerous species make up only 30-40?. of the 

 biomass. A similar picture is observed for the chaetognaths and euphausiids, 

 In the equatorial area of the Pacific Ocean, the intensity of upwelling 

 of water decreases from east to west, and the standing stock of plankton 

 decreases, while the species diversity of large copepods and euphausiids 

 simultaneously increases (Gueredrat et al., 1972), and still greater 

 species diversity of euphausiids is observed in the south central community 

 (Roger, 1974). 



Thus, in equatorial communities, where upwelling of water is stronger 

 and more frequent, we can expect a greater dominance of individual 

 species than in the central communities. 



In the distant neritic communities in currents along the western 

 coasts of the continents, and in neritic communities, dominance of one 

 or two species is quite clear. In the region of the California Current, 

 an increase has been shown in the dominance of the two most numerous 

 species in the direction from the ocean to the shore, and the species 

 diversity of zooplankton decreases to the shore, as evaluated by the 

 Fisher coefficient (Longhurst, 1967). 



Taxonomic and trophic groups . In the tropical oceanic communities, 

 in comparison to the Arcto-boreal communities, the relative quantity of 



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