Summary 



The Third Joint US-USSR Expedition to the Beting and 

 Chukchi Seas was carried out in the summer of 1988. This 

 expedition is the third in a series of expeditions are being 

 carried out under the auspices of the Joint US-USSR BERPAC 

 program. The BERPAC program is a program for long-term 

 ecological research of ecosystems of the Bering and Chukchi 

 Seas and the Pacific Ocean (BERPAC). Its goals include 

 /. assessment of ecological consequences of contamination; 

 2. study of the processes detennining the assimilative capacity 

 forcontaminants in marine ecosystems; 3. study of the elements 

 of the biogeochemical carbon cycle and its role in global 

 climatic processes; and 4. investigations of the physical 

 mechanisms related to climate variations. Central to the 

 BERPAC program is the occupation of fixed sites at regular 

 intervals in order to provide data on long-term trends. 



The Bering-Chukchi Sea plays a critical role in global 

 climate processes. This region can be defined as a major impact 

 area. Since it is located at the boundary of so many critical 

 temperature dependent forces, it is logically very susceptible to 

 disruptions in the world' s temperature budget. Several of these 

 critical processes are discussed; unfortunately most of them are 

 only partially understood. Better understanding of these 

 processes will be necessary in order to assess the full impact 

 that global warming will have. For example, this region is 

 directly impacted by the major northward cold-water current 

 flow, which arrives from the deep Pacific and which is part of 

 the major global current that has a central role in regulating the 

 world's climate. This oceanic current is largely responsible for 

 the high productivity of the Bering-Chukchi Shelf regions, and 

 thus, the fisheries are intimately linked to this systein, not to 

 mention the entire biology of the area. This area is also the 

 boundary region for the annual iceover cycle, which has a 

 major impact on climate, sea level, and other critical processes. 



The specific results of the Third Joint US-USSR Bering & 

 Chukchi Seas Expedition are discussed in a .series of 45 

 separate research articles, including observations from many 

 scientific disciplines. The major focus of the program was on 

 biological processes and anthropogenic pollutant interactions, 

 especially chemical pollutants. Studies of the hydrology of the 

 system and several hydrochemical parameters were also 

 monitored in order to better understand material transport 

 processes. Overall, 1 19 stations were occupied. Sampling 

 included areas in the deeper waters of the Bering Sea, several 

 stations along the western portion of the Bering Shelf, the 

 Chirikov basin, the Bering Strait, and the southern half of the 

 Chukchi Sea. Two specific sites in the Bering Sea. the East and 

 North Polygons (see Frontispiece), were sampled as a 

 continuation of long-term sampling at these locations that was 

 started on the 1977 cruise. Data from these sites were analyzed 

 for trend characteristics. 



The northern Bering-Chukchi Sea ecosystem is a series of 

 three centers of high biological production deposition centers 

 arranged in the prevailing northward flow from the northern 

 Bering Sea into the Arctic Ocean. Advection transports the 



nutrient supply, which is in sufficient abundance to seldom 

 become limiting. The northward current arises from the shelf 

 edge of the northern Bering Sea and Oows first around the Gulf 

 of Anadyr, containing the first production center; it then 

 crosses the Chirikov basin, with the second; and then traverses 

 the southern Chukchi Sea, which contains the third. An 

 overview paper describes /. the water masses of the system, 

 their spatial arrangement, interannual variability, and formation; 



2. the flow field including transports and residence times; and 



3. the Chukchi Sea, a center of very high production, but about 

 which little is known. In a second paper, the more than 100 

 conductivity, temperature, and density depth (CTD) stations 

 occupied during the expedition were used to provide the first 

 complete synoptic picture of the regional water masses. Rates 

 of change indicate the different degrees of effectiveness of 

 vertical and lateral mixing in different parts of the basins. 



The biogenic nutrient content of the Bering Sea is closely 

 coupled to the primary production and regeneration processes 

 occurring in its water. The waters at depth in the deep Bering 

 Sea hold large quantities of nutrients compared to other parts 

 of the world's oceans, indicating that the Bering Sea is a sink 

 rather than a source for these nutrients. The Gulf of Anadyr 

 receives deep water from the open Bering Sea. The surface 

 waters in the Gulf of Anadyr are productive, especially near the 

 coastline where upwelling occurs. The resulting phytoplankton 

 probably act as seeds for the bathy metrically upwelled water in 

 Anadyr Strait and provide organic matter to support subsequent 

 regenerative processes. The Chukchi Sea receives the northward 

 flow of nutrients and organic matter from the Bering Strait. In 

 the central portion of the Chukchi, surface concentrations of 

 nitrate are high, greater than 1 |amole/l, while subsurface values 

 are as high as 20 )imole/l. Along the Siberian coast in the 

 Chukchi, an additional source of high salinity-high nutrient 

 water was encountered. The high nitrate content of this 

 southward flowing coastal water adds to the central Chukchi 

 Sea as it joins the Bering Strait water. The gains and losses of 

 nutrients in the Bering-Chukchi Shelf ecosystem ultimately 

 transit to the deep-ocean Arctic basin. 



Studies of the microbiological regime of the Bering Sea 

 showed that the concentration of bacterioplankton during this 

 expedition was, generally, higher than in the BERPAC 

 expeditions of 1981 and 1984. For instance, the total number 

 and biomass of microorganisms for the entire area varied over 

 a wide range (i.e., from 0.12 to 3.3 x lO*" cells/ml and 

 2.7-75 |ig C/1. respectively). Maximum average values for the 

 total number and biomass of bacteria for the whole of the water 

 column were highest in the northern region of the sea, followed 

 by the Gulf of Anadyr, and lowest in the southern part of the 

 basin. The average values for all these areas together were 

 0.67 X lO"' cells/ml and 15 |ig C/1. The indices for microbial 

 cenoses were five times higher than they were in 1984. For the 

 Chukchi Sea. the total number of microorganisms varied from 

 0.31 to 2.0 X 10" cells/ml, and the biomass varied from 6.9 to 

 44,7 |ig C/1. The most developed microbial cenoses were 



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