THE CHUKOTSK SEA 265 



amphitrites and others. The most typical Arctic forms are the Infusoria 

 Metacylis vitroides, the jellyfish : Euphysa flammea and Aeginopsis laurentis; 

 the Copepoda Calanus hyperboreus, Euchaeta glacialis and Metridia longa, 

 and the Appendicularia Oikopleura vanhoeffeni. 



V. Bogorov (1939) and V. Jashnov (1940) give a quantitative percentage 

 ratio of various plankton groups of the Chukotsk Sea, set out in Table 115. 



Table 115 



Plankton composition in the second 

 half of July 1934 (Bogorov's data) Plankton corn- 

 Form position, August- 



Throughout whole Surface layer September 1 929 

 water column (10 m deep) (Jashnov's data) 



44-8 

 25-2 

 73-0 

 140 

 50 



27-6 Z. 32-6 



80 



The difference in the plankton composition as given by these two authors 

 depends on the fact that Jashnov collected his data in the western and north- 

 western parts of the Sea, often far removed from the coast, whereas Bogorov 

 collected his data close to the Siberian shores. The relative decrease of Cope- 

 poda near the shores and the large admixture of larval forms is striking. 

 Data on the phyto- and zoo-plankton biomass are given in Table 116. 



The reduction of the open sea biomass to almost one-third (right-hand 

 column) must be attributed to the season : the collection was made in the 

 second half of July, when zooplankton had not yet reached its full develop- 

 ment. The low indices of both parts of plankton for the Cape Angueme region 

 (second column) are explained by the accumulation of solid ice. The eastern 

 and western parts of the Sea were already clear of ice and phytoplankton was 

 in a state of vigorous bloom. According to V. Jashnov's calculation the largest 

 total biomass is almost 1 million tons ; this is apparently a considerable under- 

 estimate. 



Benthos 



Qualitative composition. The qualitative composition of the flora and fauna 

 of the Chukotsk Sea reveals a complex mixture of an Arctic fauna of Pacific 

 and Atlantic origin. According to data compiled by A. D. Zinova (1952) 70 

 species of green, brown and red algae — 29 brown and 31 red — have been 



