hydrooptical means matched the chlorophyll intensities that 

 were associated with these zones. 



Study of epipelagic mesozooplankton of the Bering and 

 Chukchi Seas revealed structural characteristics with 

 considerable dependence on distribution of four groups of 

 species (south Bering Sea oceanic, north Bering Sea oceanic, 

 neritic and Anadyr), as well as two eurybiontic species {Oithona 

 similis and Pseudocahinus miniitiis). In deep-water regions of 

 the Bering Sea and on the northern shelf, high biomasses 

 (40 g fresh weight/m- average in the 0- 1 00 m layer ) were made 

 up of species from south Bering Sea oceanic groups. In the 

 cold-water masses from the shelf, there was a predominance of 

 species from the north Bering Sea oceanic groups. Neritic 

 groups of species (including Rotatoria. Clodecera. and small 

 species of copepods, as well as pelagic larvae of benthic 

 organisms) constituted over 70% of the total number in the 

 eastern part of the Chirikov basin, which was out of reach of 

 Anadyr Currents. The mesozooplankton community of the 

 Chukchi Sea basically consists of neritic and eurybiontic 

 species. The persistent presence of species from the south 

 Bering Sea and Anadyr groups among the Chukchi Sea species 

 confirms the obvious influence of Bering Sea fauna on this 

 region. 



Study of zooneuston in the Chukchi Sea found copepods 

 to be most abundant throughout. The mosaic distribution of 

 Bering Sea groups in the neuston layer of the Chukchi Sea 

 verifiedthecomple.xhydrodynamicsof near-surface water and 

 their connection with the Bering Sea. 



Necrozooplankton were measured throughout the study 

 area. Stratification of dead zooplankton were observed at 

 water mass boundaries most typically characterized by 

 differences in temperature. More typically, the 

 necrozooplankton were found at the same zones where they 

 had died and were not layered. Noteworthy for the Anadyr was 

 the presence of dead zooplankton of both oceanic and neritic 

 types. 



Ciliate protozoa were monitored over the study area. Their 

 abundance followed the general abundance of other planktonic 

 species. The Chukchi Sea is characterized by a unique mi.x 

 including several larger species. The levels of ciliate 

 development in the deep Bering Sea, the East Polygon, and 

 Bering Strait exceeded those for the Chukchi Sea. Elevated 

 ammonia and chlorophyll accompanied high ciliate biomass. 

 Overall, for the Bering Sea. the ciliates constituted 1.5 g of 

 primary and bacterial production per mVday, yielding 

 0.5 g/mVday. For the Chukchi Sea, these figures are 

 2 g/mVday and 1 g of production, respectively. 



The 5 "C values for copepods and euphausiids zooplankton 

 showed enrichment in 5 "C relative to similar taxa collected 

 in 1986 from the Beaufort Sea. Euphausiids were approximately 

 1.1 parts per thousand (ppt) more enriched in 5 "C than 

 copepods from the same area. Overall 8 "C values for 

 zooplankton were about 1 ppt depleted in 1988 relative to the 

 same taxa collected in 1987. The changes in average 

 zooplankton 5 '^C values reflect previous studies in the isotopic 

 composition of bowhead whales (Balaena mysticetus). which 



feed on the zooplankton in these regions and carry muliiycar 

 records of feeding activity in the "C:'-C ratios in their baleen 

 plates. 



Seven families of icthyoplankton were identified among 

 the zooplankton species sampled. Exact species were identified 

 from the codfish and the flatfish families. Two of these 

 specimens were newly hatched at a location considerably north 

 of reported spawning grounds, Theragra chalcograimna 

 (walleye pollock) and Hippoglossoiodes elassodon (flathead 

 sole). These findings suggest the possible occurrence of a new 

 spawning location considerably north of previously reported 

 sites. Larval fish densities were highest where shelf waters 

 overlie Anadyr water and in areas where integrated chlorophyll 

 a concentrations were less than 100 mg/m'. 



A plankton model was described that was developed from 

 1981 and 1984 BERPAC results from the North and East 

 Polygons. Bacterioplankton, phytoplankton, and zooplankton 

 (micro- and mesozooplankton) were considered the major 

 contributors to the biological activity in the model. The 

 modeling results indicated that production and destruction of 

 organic matter were occurring at very high rates and seasonal 

 factors have an overriding influence on the ecosystem. Similar 

 modeling is planned with the 1988 data. With the high rates of 

 organic turnover indicated by the model, anthropogenic 

 influences on these rates, even when they are very slight, could 

 have profound effects on the natural processes in this system. 



The distributional patterns of primary production reflected 

 similar trends to those observed in the Bering Sea during the 

 summer of 1984. The average areal production was 

 1.8 g C/m-7d' with a high of about 15 g C/mVd'. Primary 

 production during the growing season fixed an estimated 

 0.2 X 10" metric tons of carbon. In addition, the sampled areas 

 of the Chukchi Sea contributed another 8.3 x 10" metric tons for 

 the growing season. The particulate phytoplankton carbon flux 

 through the Bering Strait was estimated to be 3.2 x 10" metric 

 tons per year. The estimated tlux of dissolved carbon to the 

 Chukchi Sea-Arctic Ocean amounted to 0.82 x 10' metric tons 

 per year. A significant portion of this carbon likely finds its 

 way to the deeper waters of the Arctic Ocean. Eventually, this 

 carbon may be incorporated into the North Atlantic bottom 

 water. Both of these avenues would act as greenhouse gas 

 sinks. 



In studying benthic processes, significant correlations 

 were found between the stable oxygen isotope composition of 

 bottom seawater, salinity, and tunicate cellulose in the study 

 area, enabling determination of O'VO'" ratios and spatial 

 locations for the major water masses in the region. High 

 sediment oxygen uptake rates and high benthic biomasses were 

 observed in the western shelf regions of the Gulf of Anadyr, 

 Chirikov basin, and southern Chukchi Sea. Low sediment 

 respiration and faunal biomass were observed in the central and 

 slope areas of the Gulf of Anadyr and near the Alaska coastline. 

 There was little difference in benthic faunal composition over 

 the entire study area. Species composition was always 

 characterized by panarctic and boreal-arctic complexes. 

 Average benthic biomass was always high, exceeding 



401 



