THE SEA OF OKHOTSK 



803 



the total biomass is frequently of the order of 1 kg/m 2 . In the deep trench in 

 the central part of the Sea the benthos biomass is extremely small, as low as 

 10 mg/m 2 . 

 The mean benthos biomass throughout the Sea of Okhotsk is about 200 g/m 2 , 



Fig. 398. Ecological zones of bottom-living fauna of Sea of Okhotsk (Savilov, 

 1961). See page 800-802 for key. 



while the general total biomass of bottom-living fauna is about 300 million 

 tons, molluscs occupying the first place among the individual groups. 



In some cases biocoenoses acquire an oligomixed character, and under 

 markedly unfavourable life conditions only a few specifically adapted species 

 are able to multiply and develop. Thus, for example, on pure beach sands 

 there is a great and almost exclusive development of the Echinarachnius parma 



