THE SEA OF AZOV 



513 



several years, and Mytilaster was almost completely replaced by Cardium. 

 The increase of benthos up to 1947 was mostly due to Cardium (Fig. 241). 

 The amount of benthos continued to decrease, and by the autumn of 1948 

 its mean biomass was reduced to 106 g/m 2 in the northern part of the Sea of 

 Azov. In Stark's opinion these changes in the quantitative composition of the 

 benthos may have been partly the result of silting, linked with the abundance 



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Fig. 241. Bottom biocoenoses of the Sea of Azov (occurrence at the stations (Stark, 

 I960)). 1 Mytilaster; 2 Cardium; 3 Brachynotus; 4 Syndesmya; 5Balanus; 6 Hy- 

 drobia ; 7 Nereis ; 8 Corbulomya ; 9 Nephthys. 



of flood waters in 1937-39, which had an unfavourable effect on fauna which 

 avoids soft mud bottoms (Mytilaster, Balanus and others). 



Bottom-fauna of the Gulf of Taganrog varies considerably from year to 

 year; Stark (1955), as well as Mordukhai-Boltovskoy (1948), connects these 

 fluctuations with the changes in the spring floods of the river Don. During the 

 years 1933-35 Cardium, Balanus, Hydrobia and other more salt-loving species 

 were widely represented in the benthos. Those were years of low spring floods. 

 In 1948, when floods were high, the role of these forms became insignificant, 

 but after the exceptionally low floods of the Don in 1949 and 1950 a pro- 

 nounced increase of marine fauna, principally the inferior food forms Balanus 



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