The triennial investigation gave us right not only in completion of taxonomic structure of zooplankton of the Middle Caspian, but also revealed that, under optimum environmental conditions the dominance in communities are divided on a sufficiently number of zooplankton species which leads to an increase of species diversity. According to the results of test on the portion of rotifers include 20 species which are represented mainly by such genera as Trichocerca, Brachionus, Synchaeta and 13

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... es of Copepoda and 11 species of Cladoceran. On the basis of these data there carried out comparision of the species of composition of Ciliophora, Rototoria, Copepoda and Cladocera for each pair of points of collection. The analyses showed that the maximum value of the index of species composition of community is in the range from 35% to 72 %, and maximum value from 11% to 21% was observed in Sumgait littoral, which was first of all deals with the strong stress of technogeneous pollution and oil products of the Southern coast of the Absheron Peninsula.