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



infusorians (Tintinnoides) and 21 are forms whose systematic position is not 

 clear ('problematic' forms). 



Apart from these two groups above there are 259 species. The numbers of 

 species are distributed among the various seas as follows (including the species 

 encountered in several seas): Barents Sea 131, White Sea 62, Kara Sea 138, 

 Laptev Sea 78, East Siberian Sea 37, Chukotsk Sea 74. 



The number of species of the basic groups of plankton present in various 

 seas is: Tab/e J5 



In the plankton fauna the greatest variety is found in the Copepoda group 

 (81 species). Copepoda, and in the Barents Sea Euphausiacea also, are as 

 usual the predominant groups of the biomass, forming the basic components 

 of the food of fish and some mammals. 



In the epicontinental parts of the eastern sector of the Arctic basin a 

 definite change in the qualitative composition of plankton can, according to 

 Jashnov (1940), be traced as one moves eastwards and approaches the shores 

 where the coastal waters have lost some of their salinity (Fig. 6). Throughout 

 the southern part of the Barents Sea, to the west and north of Spitsbergen, 

 i.e. in the regions most subject to the influence of the Atlantic waters, nine- 

 tenths of the plankton consists of Calanus finmarchieus (1)* and contains many 

 boreal forms of Copepoda : Metridia lucens, Euphausiacea : Limacina retro- 

 versa and others. The average plankton biomass of these regions is equal to 

 230 mg/m 3 . In the northern part of the Barents Sea besides Calanus finmarchi- 



* V. A. Jaschnov (1957, 1958) distinguished and singled out Calanus finmarchieus s.l. 

 species C. glacialis. The area of the latter's dwelling covers the entire Arctic Basin, the 

 waters adjoining from the east and west and extending towards North America up to New- 

 foundland in the southern direction. This area included also the Bering and the Okhotsk 

 Seas. From the south its area links up with the areas in the Pacific Ocean C. pacificus 

 and in the Atlantic Ocean C. finmarchieus s.str. 



