GENERAL CHARACTERISTICS OF THE NORTHERN SEAS 



49 



to 



о 



<o 

 о 



<^?q 



Ш Ш 



Fig. 8. Change in number of species (7) and number of specimens (2) per m 3 from 

 tropical part of Pacific Ocean (/) through northern part of the Pacific (//, ///), 

 Bering Sea (IV, V), Chukotsk Sea (VI, VII) and Arctic basin (VIII) (K. Brodsky, 



1956). 



again, on account of the Atlantic forms of the intermediate warm layer, in the 

 western sector of the polar basin. On the other hand the biomass increases up 

 to the Bering Sea, decreasing sharply in the polar basin. However, the zoo- 

 plankton of the polar basin contains some endemic forms and very few Pacific 

 ones (Table 21). 



Table 21. Number of Atlantic, Pacific and endemic forms of Calanoida in the Arctic 



basin (percentage) 



Area 



Atlantic species 



Pacific species Endemic species 



Nansen Ridge 

 Arctic basin 



60 

 48-50 





 13 



Most typical of the endemic forms are the deep-water ones described by 

 K. Brodsky (1956): Pseudagaptilus polaris, Pareuchaeta polarls, Lucicutia ano- 

 mala, L. polaris and others. The quantitative and qualitative vertical sequence 

 of plankton in the central parts of the Arctic basin, illustrated in the following 

 manner by V. Jashnov (1940) (Table 22), is most significant. 



The greatest density of plankton is related to the less saline surface layer of 

 water, while the greatest quantitative variety is found in the deep layers in 



