deep-water regions of the Bering Sea. It is obviously determined 

 by penetration of waters of the Bering Slope Current into the 

 Gulf of Anadyr. At the same time, the gulf was characterized 

 by favorable developmental conditions of the specific Anadyr 

 species complex. In this location, values of the total number 

 and biomass were higher than in other areas of the northern 

 shelf region and equaled 440,000 ind/m- and 40 g/m-. 



Fig. 20. Structure of mesozoopli>nkton communilies in the defined region,s of 

 the Bering and Chukchi Seas. 



Another type of community similar to the Anadyr 

 community was found in the Strait of Anadyr (Station 41). 

 Waters of the Anadyr Current originate in the gulf and flow 

 through the strait. Due to mixing with north Bering Sea Shelf 

 water, we observed a decrease of the content of the south 

 Bering Sea oceanic species that lead to the decrease of 

 zooplankton biomass to 25 g/m- and the increase of content of 

 the appendicularian, Oikopleuni lahnidahensis. Effects of the 

 Anadyr waters that are inhibited with the Anadyr type 

 communities are also marked in the western Chirikov basin and 

 the Bering Strait (Stations 86, 89, 96, 100, 104, and 106; 

 Figs. 19,20). Theaverage values of quantitative indices of the 

 community status of the region are similar to those of the 

 Anadyr Strait. Total number of species was predominantly 

 influenced by eurybiontic species and meroplankton (O. similis. 

 32<7c:P.minitus. 15'7f;meroplankton, 19%). About 50%ofthe 

 zooplankton biomass of this region was constituted by the 

 south Bering Sea species; 14%, appendicularian 

 O. lahradoriensis; 10%, meroplankton organisms. One can 

 usually find small quantities of the Anadyr complex species. 

 The highly dynamic nature of hydrographic processes in this 



region cause wide ranges of variability of quantitative 

 zooplankton parameter levels. The amplitude of variation of 

 organism abundance equaled 1 82- 1 ,00 1 ,000 ind/m-, and total 

 biomass, 12-35 g/m-, while the density of plankton 

 conglomerations per cubic meter reached the maximum value 

 for the study period, 1 .4 g at Station 104. 



The mesozooplankton community in the eastern Chirikov 

 basin and Bering Strait (Stations 83, 92, and 102) was 

 characterized by a predominance of a neretic group of species 

 that includes larvae of benthic animals (73% of abundance and 

 55% of biomass): copepods Acartia longiremis. A. cleiusi, 

 Centropages memurrichi. Tortanus discaunialus, Eurytemora 

 herdmani, E. pacifica; the cladocera Evadne nordman, and 

 Podon leuckartii. These species are primarily features of the 

 summer season (Kun, 1975). Mesozooplankton samples showed 

 practically no species from the south Bering Sea and Anadyr 

 complexes, nor euphasiid larvae. As a result of formation of 

 numerous agglomerations of small neretic organisms, the total 

 number was considerably larger than that of the western basin 

 and equaled 1.2-2.7 x 10" ind/m', while the biomass was 

 smaller, averaging 14 g/m-. 



As it was shown above, results of statistic analysis of 

 common character of species composition of the community of 

 mesozooplankton sampled at stations in the southern Chukchi 

 Sea demonstrated qualitative homogeneity of the plankton 

 fauna of the region. At the same time, the structure of the 

 community (i.e.. relative content of elements, their part in the 

 monitored levels of total quantitative characteristics) was 

 marked by considerable differences. Classification of stations 

 on the basis of I,, value calculated according to equation I 

 allowed differentiation into three groups of stations in terms of 

 value of the index of 0.6 (Fig. 21). 



We should note that, in general, the mesozooplankton 

 community of the Chukchi Sea Shelf was greatly affected by 

 zoocenosis of the northern Bering Sea. It was manifested in the 

 presence of the south Bering Sea oceanic and Anadyr groups of 

 species at the pelagic zone. These groups were transported 

 there most obviously by waters of the Anadyr Current 

 (Coachman et al.. 1975). Although, their number was not 

 significant and never exceeded the average of 5% of the total 

 number and biomass of the community. Density of 

 conglomerations of Ointhoiui similis population in the Bering 

 Sea was at the same level. Mesozooplankton of the Chukchi 

 region of investigation had another common feature; that is, 

 prevalence of pelagic larvae of benthic animals (average of 

 35% of abundance and 20% of biomass) and Pseudocalanus 

 miniitus (27% of abundance and 14% of biomass). 



In addition to the pronounced similarity of community 

 structure, there were certain differences in some regions. In the 

 northwest Chukchi Sea (Stations 45, 47, 57, and 59), we 

 detected an intensive development of population of the 

 appendicularian Oikopleiira labradoriensis that totaled 20% 

 of the abundance and 57% of biomass (Figs. 19,20). This 

 formed total index levels that are unusually high for the 

 Chukchi Sea. The structure of community in the northwest 

 (Stations 49, 50, 52, and 53) and south (Stations 69 and 74) 

 regions most of all showed good agreement with the average 

 assessments for the Chukchi Sea in general. Mesozooplankton 



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