216 



BIOLOGY OF THE SEAS OF THE U.S.S.R. 



size of individual specimens of most of the characteristic forms. The popu- 

 lation of individual forms of the White Sea, so far as we could observe, never 

 reached a density characteristic of the other regions of the Arctic. This can 

 be shown by a comparison of the quantitative data for a number of forms 

 common to the Barents and White Seas {Table 94). 



Table 94. The largest biomass determined for certain forms in the White and Barents 

 Seas and in some other regions of the Arctic 



Only a few forms in the White and Barents Seas give similar biomass in- 

 dices, although the living conditions in the White Sea are exceptionally 

 favourable for a number of forms, such as Zostera marina among the plants 

 and Portlandia arctica, Leda pernula, Yoldia hyperborea, Asterias lincki and 

 others among the animals. Moreover both as regards the inflow of river water 

 and the supply of vegetative detritus, the White Sea may be classed as a most 

 favourable environment. In this respect there is some similarity between 

 the White and Baltic Seas. The biomass indices of this latter are also compara- 

 tively very low. The scarcity of the Baltic Sea fauna is naturally related to the 

 bad aeration of deep-floor layer and to a considerable dilution of the waters 

 of the eastern and especially the northern parts of the Sea. In the White Sea 

 this last factor is not of much importance for the quantitative development 

 of its fauna; as regards the deep-floor layer aeration, most investigators 

 consider it quite sufficient for the development of bottom life. 



We think that the lowering of the indices of biological productivity of the 

 White Sea is mainly due to two factors. For the littoral fauna and for that of 



