impacts influence not only the biotic component of the marine 

 environment but different abiotic components as well. Such 

 impacts lead to even more significant changes in the World 

 Ocean and in the biosphere as a whole. 



Specific features of the Bering Sea and other ecosystems 

 w ith "background" levels of contamination are such that they 

 are especially vulnerable because of the continual input of 

 small doses of pollution. This leads to a gradual accumulation 

 of pollutants, and may ultimately cause the degradation of the 

 ecosystems. Therefore, ecological investigations and 

 monitoring of the background regions of the ocean, especially 

 in such highly bioproductive zones as the Bering Sea, are of 

 g reat importance. In order to assess the ecological consequences 

 of the pollution and isolate anthropogenic effects from the 

 background of natural variability, it is necessary to make long- 

 term observations of fundamental physical, chemical and 

 biological processes in selected areas of the above regions. 

 These regions differ in their geographical location, as well as 

 in the subsystems of their ecosystems, and are subjected to 

 different anthropogenic impacts. 



2. Study of the Processes Determining the Assimilative 

 Capacity for Contaminants in Marine Ecosystems 



In the marine environment, various physical, chemical, 

 and biological processes occur through which contaminants 

 can be eliminated from the ecosystem without serious 

 disturbances of the biogeochemical cycles of the elements or 

 changes in the biota. Diverse oceanological investigations 

 carried out in the last few years have shown that the biotic 

 component is important in the fluxes of pollutants. 



The ability of an ecosystem to protect itself against a 

 foreign interference at the expense of many biological, physical, 

 and chemical processes is its natural ■■immunity"' and the 

 measure of this immunity is its assimilative capacity. 



According to the contemporary interpretation (Izrael & 

 Tsyban. 1983b, 1989; Izrael et a/., 1988b.c), the assimilative 

 capacity of a marine ecosystem is an integral function of its 

 ex ist ing environmental status that reflects the ability of physical, 

 chemical, and biological processes forelimination of pollutants 

 and their impacts on the biota. 



When using the concept of assimilative capacity in practice, 

 it is necessary to bear in mind that a marine ecosystem occupies 

 a finite volume that may be isolated on the basis of the spatial 

 distribution of organisms of various trophic levels, groups of 

 ecologically similar species, and production/destruction 

 processes, as well as physical and chemical characteristics. 

 Hence, the assimilative capacity of each specific ecosystem 

 also has a value that objectively characterizes existing properties 

 of the marine em ironment. This value could be determined in 

 practice on the basis of integrated investigations and monitoring 

 of the marine environment, carried out in accordance with 

 existing methodological recommendations (Izrael & Tsyban. 

 1983b, 1985, 1987, 1989; Izrael etal., 1988b). 



The use of this concept in the BERPAC studies will 

 include investigations of the following basic problems: 

 /. quantitative assessment ol the balance of chemical elements 

 in the ecosystem and possible changes in residence times due 

 to disturbances: 2. assessment of adverse biological effects at 



the level of population and communities: and.v determination 

 ol the critical concentrations at whichcontaminants adversely 

 impact the marine organisms and communities. 



Thus, a conceptual model of the assimilative capacity, 

 based on a better understanding of the laws of marine ecosy stem 

 functions, can serve as a theoretical basis for the dev elopment 

 of forecasts of both the immediate and long-range 

 consequences of anthropogenic and climatic impacts on the 

 ocean ecosystems. 



3. Study of the Elements of the Biogeochemical Carbon Cycle 

 and Its Role in Global Climatic Processes 



Global warming predicted in connection with the 

 developing greenhouse effect depends directly upon the 

 biogeochemical cycle of carbon — the most important process 

 forming the Earth's climate. The basic elements of this cycle 

 are carbon-dioxide and other "greenhouse gases" exchanged 

 within the ocean-atmosphere system, the function of the 

 carbonate system, and the turnover of organic forms of carbon 

 in the ocean. 



The most intensive uptake of atmospheric CO, occurs at 

 high latitudes, as a result of favorable thermal and hydrological 

 conditions (low sea surface temperature and permanent 

 downwelling) in the region. These peculiarities explain the 

 important role of the Bering Sea, a subarctic body of water 

 having a large area, in the global cycle of carbon dioxide. 



The relationship between the rates and directions of CO, 

 flow within the ocean-atmosphere system directly affects the 

 functioning of the carbonate system. So. in the conditions 

 where global warming is induced by an increase in the 

 concentration of atmospheric CO : . a shift of the equilibrium 

 between carbonate forms of carbon in seawater might occur, 

 which will be accompanied by a decrease of pH and. 

 consequently, elevation of the lysocline. 



Investigations of these processes, directly affecting the 

 sedimentation of organic carbon and the vital functions of 

 marine organisms, are only possible with direct determination 

 of all components of the carbonate system (i.e.. HCO„ CO,, 

 H : CO,. andCO,). 



To fully understand all of the characteristics of the oceanic 

 portion of the global carbon cycle, it is necessary to stud) the 

 processes of the circulation of its organic forms in the 

 composition of dissolved and particulate matter and in the cells 

 of living organisms (Zaitsev. 1970. 1980, 1985). 



The dynamic equilibrium of dissolved and particulate 

 organic matter, living matter, and the content of organic carbon 

 within water masses depends on the relations between 

 production/destruction processes established in the ecosystem. 

 In this connection, the predicted effects of global warming on 

 the bioproductivity of the Bering Sea ecosystem will influence 

 the organic carbon cycle. In order to studv possible changes, 

 long-term observations of the concentrations of all organic 

 forms of carbon are necessary. 



Thus, to establish the carbon balance in the Bering Sea 

 ecosystem, comprehensive long-term observations of all carbon 

 constituents in the aquatic interface and the study of quantitative 

 and qualitative composition of both the carbonate system and 

 organic forms of carbon are required. 



IV 



