. Biology of the seas of the Marine biology -- Soviet Union; Hydrology -- Soviet Union. THE CASPIAN SEA 621 The Nereis biocoenosis (L. Vinogradov, 1953) has not replaced, and could not have replaced, the biocoenosis of small Adacna, higher crustacean and chironomid larvae. Only in one place (Tyuleni Island), forming 1 -8 per cent of the whole area, has the Nereis biocoenosis taken the place of an oligochaete biocoenosis, but it formed a biomass there two to seven times (in different years) greater than the oligochaete biocoenosis. The examination of benthos throughout the whole Caspia
. Biology of the seas of the Marine biology -- Soviet Union; Hydrology -- Soviet Union. THE CASPIAN SEA 621 The Nereis biocoenosis (L. Vinogradov, 1953) has not replaced, and could not have replaced, the biocoenosis of small Adacna, higher crustacean and chironomid larvae. Only in one place (Tyuleni Island), forming 1 -8 per cent of the whole area, has the Nereis biocoenosis taken the place of an oligochaete biocoenosis, but it formed a biomass there two to seven times (in different years) greater than the oligochaete biocoenosis. The examination of benthos throughout the whole Caspian Sea carried out in 1956, 18 years after the 1938. Fig. 291. Quantitative distribution of benthos in Central and part of the Southern Caspian in 1956 (g/m2) (Romanova, 1960). survey (N. Romanova, 1960), has revealed considerable changes in the nature of the distribution of the bottom-living fauna (Fig. 291). The eastern shores of the Northern and Central Caspian are richer in benthos than the western ones. The main mass of benthos is formed by Mytilaster, with a pronounced decrease in the amount of Dreissena, Didacna, Monodacna and Adacna (63 per cent of total biomass in the Central Caspian, and 94 per cent in the Southern). The part played by Cardium is increased, and Nereis is strongly developed (Fig. 292) on soils rich in organic matter (Fig. 293). In its central parts the Sea is deeper than 200 m and the benthos biomass there falls below 1 g/m2. Total benthos biomass reaches its maximum at depths of 10 to 25 m. In the Southern Caspian at depths of 200 to 300 m the biomass decreases to. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Zenkevich, L. A. (Lev Aleksandrovich), 1889-1970. New York, Interscience Publishers
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