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



The qualitative wealth of the Kara Sea fauna, and probably also of the 

 northwestern part of the Laptev Sea, is explained by its being the meeting 

 ground of fauna of different origins. This is connected with the different 

 sources of the water masses noted above. 



Plankton 



The phytoplankton of the Kara Sea has been quite fully studied. There is the 

 following to be added to what has already been said in our introduction to 

 northern seas : the total number of species of plankton algae found in the Kara 

 Sea is 78 (see Table 100). 



Table 100. Qualitative composition of phytoplankton of the Kara Sea {data of 



P. Usachev, 1947) 



Percentage of the 

 Form No. of species total number 



Flagellates 2 2 



Silicoflagellates 2 2 



Peridineans 20 27 



Diatoms 52 67 



Green algae 2 2 



Total 78 100 



According to P. Usachev (1947), two areas of increased phytoplankton bio- 

 mass can be distinguished in the Kara Sea: * a northern one near Wiese Island 

 with a biomass of 1 to 3 g/m 3 and more, in the parts of the Sea warmed by the 

 warmer Atlantic waters and near the edge of the melting ice ; and a southern 

 one, influenced by the inflow from the Ob and Yenisey, with a biomass of 

 more than 1 g/m 3 (Fig. 99). It is evident from the diagrams given that the 

 main mass of plankton is adapted to the upper 25 m layer (more than 

 500 mg/m 3 ). 



Typical spring diatoms are preponderant in the northern region; in the 

 southern one later forms and forms typical of the estuarial zones are found 

 side by side with the former. In Usachev's opinion (1946) the productivity of 

 Kara Sea phytoplankton is about equal to the indices for the northeast region 

 of the Barents, Laptev and East Siberian Seas. The phytoplankton mass in 

 some cases is as high as 6 to 8 g/m 3 . 



Qualitative composition of zooplankton. V. Khmisnikova (1936) has recorded 

 169 forms of plankton for the whole Kara Sea, not counting larvae and 



* It should be borne in mind that all data on Kara Sea phytoplankton refer to the short 

 summer period of one to two months and are valid for one area and for one time of the 

 year. No observations exist for different seasons of the year and for different parts of the 

 Sea simultaneously. 



