the epipelagic zone of the deep-water of the southwest Bering 

 Sea. the striking similarity of species composition, dominating 

 taxa, similar abundance, and biomass allow assessment of this 

 vast area as a homogeneous region; that is, a continuation of the 

 North Pacific Ocean. At the East and South Polygons, 

 mesozooplankton abundance is considerably influenced by a 

 population of Oithona similis: their number totaled 80% of the 

 overall average. Species of the south Bering Sea oceanic group 

 constituted only 8%. Still, these organisms, especially 

 Eucalanus bungii, dominated the biomass accounting for 60% 

 of the total weight. Oithona ^/'»;;7;'5 biomass constitutes only 

 13% of the total biomass of the community. 



Off Cape Navarin, at depths more than 100 m (Stations 7, 

 1 1 , and 13), abundance of mesozooplankton was relatively low 

 (800,000 ind/m-). In 0-100 m water columns, total biomass 

 reached maximum values, averaging 75 g/m-. This was 

 attributed to a concentration of large interzonal oceanic 

 copepods, Calanus plumchius and Eucakmiis bungii. Taken 

 together with other species from the south Bering Sea oceanic 

 group, they equal 24% of the total number and 78% of the total 

 biomass of zooplankton. Oithona similis formed the most 

 numerous group here totaling 59%, as well as at other deep- 

 water Bering Sea stations. There was a tremendous increase of 

 the absolute and relative abundance of species ofPseudocalaniis 

 minutiis (up to 13%). At the same time, it was noted that 

 composition of zoocenosis was influenced by the vicinity of 

 the vast shallow shelf area. The pelagic zone of this area is 

 inhabited with a specific plankton fauna. This influence was 

 manifested in the presence of large numbers of hydromedusa, 

 Aglautha digiiale, decapod larvae, the copepods Cakvms 

 glacialis and Euphaiisiida larvae. Appendicularians that are 

 abundant in shelf areas rich with phytoplankton were scarcely 

 traced in samples. 



The status of the mesozooplankton community in the 

 southern part of the Gulf of Anadyr at the stations situated over 

 lOOm-isobath (Stations 9 and 15) was obviously determined 

 by hydrographic conditions of the frontal zone that separates 

 deep-sea and shelf waters. The same frontal zone covers the 

 outerboundaryoftheeastemshelf(McRoyf?a/., 1986). While 

 qualitative composition of the community in this region is 

 fairly similar to that of the oceanic type, its quantitative 

 structure is completely different. The percentage of abundance 

 of O. similis in the population is drastically decreased. The 

 amount off. minuiiis in the community increased to 30%, and 

 the amount of the north Bering Sea oceanic group, to 12%. 

 Biomass of the latter totaled 73% of the overall value. Levels 

 of abundance and biomass decreased by 1 .5 times, if compared 

 to those in the neighboring deep-sea area. 



We believe that to analyze data on the distribution of the 

 structural characteristics of the mesozooplankton community 

 in the Gulf of Anadyr, it is necessary to take into account 

 complexity of the hydrographic process in this region. 

 Penetration of a branch of the Bering Slope Current into the 

 Gulf of Anadyr from the deep-water areas of the Bering Sea, 

 origination of the Kamchatka Current flowing southward along 

 the coastline of Siberia, and origination of the Anadyr Current 

 flowing along Chukchi Peninsula in the direction of the Bering 

 Strait — all of these factors surely influence conditions and 



distribution of the zooplankton community in the Gulf of 

 Anadyr (Coachman et al., 1975). 



Results of the studies showed that the area of the gulf and 

 the shelf that are adjacent to the east can be divided into two 

 regions. The pelagic zones of these regions are inhabited by the 

 various zooplankton communities (Figs. 19,20). In the outer 

 waters of the gulf and the neighboring western part of the 

 central shelf regions (Stations 18, 19, 22, 35, and 36), the 

 number of species of the south Bering Sea oceanic group 

 constitutes only 75% of the abundance and 3% of biomass. 

 Larvae of benthic organisms (meroplankton) and 

 appendicularians (respectively, 10 and 2%) were found. 

 Appendicularians constituted up to 30% of the biomass. 

 Eurybiontic species, O. siinilis (37%) and P. minutiis (28%), 

 dominated the abundance; north Bering Sea species (28%) 

 prevailed in terms of biomass. 



Fig. m. Structure of mesozooplankton communities in the defined regions of 

 the Bering and Chukchi Seas (number). 



The inner part of the gulf (Stations 24, 27, and 32) was 

 inhabited by a specific community that was marked by large 

 differences from the community found at the stations of the 

 outer shelf. Most of the biomass (53%) was constituted by a 

 species of the oceanic species complex dominated by Eucalanus 

 hungii. The most numerous species was O. similis (32% ). The 

 plankton community was characterized by the presence of the 

 Anadyr group that includes Euphisa sp. and a copepod Acartia 

 tumida. Their share in the total number and biomass of 

 organisms reached 5 and 7%, respectively. One-tenth of the 

 total value fell on meroplankton organisms. The qualitative 

 composition of the community suggests a close relation between 

 zoocenosis of the pelagic zone of this region and zoocenosis of 



170 



