400-500 g/m-. The Macoma cakarea community type was the 

 most widely distributed in the areas investigated. Two new 

 biocenoses, Leioniicula injlata in the Chukchi Sea and Nitcida 

 lamellosa radiata in the Gulf of Anadyr, were found with 

 average biomass values of 647 and 1,4 13 g/m-. respectively. At 

 the outlet from the central Gulf of Anadyr, biocenosis Macoma 

 calcarea had been replaced by biocenosis Nitculana lamellosa 

 radiata. 



Sediment accumulation, measured using -'"Pb inventories 

 in surface sediments, was low in the sandy regions of the 

 northern Bering Sea, with higher accumulation zones occurring 

 in the silt and clay regions in the central Gulf of Anadyr and 

 southern Chukchi Sea. Hydrodynamics have a major influence 

 on benthic community structure, biomass. and sediment 

 respiration in this arctic region. 



Filtered seawater and particulate material was collected 

 and analyzed for their isotopic content of Th-"/U-'^ Using a 

 ratio technique for these two isotopes, biosedimentation rates 

 in the Bering Sea were found to be 46.5 ± 5.3 mg/mVd, 

 suspended organic matter averaged 0.98 ± 0.04 mg/mVd, and 

 residence times were 29.7 ± 2.7 days. The values for the Gulf 

 of Anadyr were much lower, while those in the Chukchi Sea 

 were much higher. Calculated on an areal basis, the 

 biosedimentation tlu.x values range from 0.67 in the Gulf of 

 Anadyr to 5.9 g/m-/d in the Chukchi Sea. Regional variations 

 can be accounted for by phytoplankton blooms. The high rates 

 of biosedimentation demonstrate the high productivity in this 

 region. 



Humic acids comprise the bulk of dissolved organic matter, 

 which resists biochemical breakdown. They also form a large 

 fraction (30-60%) of the total dissolved organic carbon in this 

 system. The concentration of humic substances was related to 

 primary production and served as a measure of primary 

 productivity even after actual plankton blooms had disappeared. 

 The highest values were found in the region near the Bering 

 Strait. This is a result of the transport of water masses from 

 highly productive areas such as the Gulf of Anadyr, as well as 

 (>; situ production. Local maxima of humic acids in other areas 

 were related to freshwater discharges from the Anadyr River 

 and the Yukon River. The organic carbon distribution in 

 sediments indicate that there are several depositional zones in 

 the major basins that were studied. The major total carbon 

 depositions appeared to follow the regions where the major 

 algal blooms occurred. The carbon signatures for these regions 

 were mostly marine rather than terrestrial. Some specific 

 regions of organic matter buildup indicated terrestrial origins, 

 especially near the mouth of the Yukon River. Chemical and 

 isotopic data indicate that terrestrially derived organic matter 

 is transported from the North American continent into the 

 eastern area of the Anadyr-Bering-Chukchi study area, while 

 little Asian-derived terrestrial material is incorporated into the 

 western sediments. 



Observation of seabird abundance and distribution were 

 compared to the several distinct water masses that existed over 

 the studied regions. Piscivorous birds predominated by 10 to 

 20 times in the Alaska coastal area and planktivorous birds 

 were by far more numerous in the Anadyr and Bering Central 



Shelf water masses. There also was a distinct water mass 

 affinity for northern fulmars and short-tailed shearwaters to 

 locate in the Siberian Coastal water, and these were the same 

 species that were dominant in the Bering Shelf- Anadyr waters. 

 For the southern Chukchi Sea Shelf, these same bird species 

 exhibited greater along, as opposed to across, shelf 

 variability in abundance. The densities corresponded well 

 to the locations of distinct water masses in similar zonal 

 patterns. 



Anthropogenic pollutant impacts on the area were assessed 

 by observing their distributions, degradation processes, and 

 toxic effects. In general, concentrations of chlorinated 

 hydrocarbon pesticides and polychlorinated bipheny Is ( PCB ' s ) 

 were typical of data reported for other nearby arctic ecosystems. 

 Chlorinated hydrocarbons quantified in the atmosphere included 

 hexachlorocyclohexanes (HCH), hexachlorobenzene, 

 toxaphenes. and chlordane. Polychlorinated biphenyls and 

 DDT's were found at excessively high concentrations, 

 suggesting possible contamination from the ship. Detailed 

 studies of the tlux of a- and y-HCH across the air-sea intertace 

 indicated that, in many areas, the predominate flux for the 

 Y isomer was from the air and that there was a net atmospheric 

 loading of this compound into this area. No local sources were 

 apparent. 



The concentration of DDT in the seawater was lower than 

 the 1984 BERPAC data, although its level of accumulation in 

 the suspended sediment was still very high, as before. In water, 

 the HCH's are the contaminant group of highest concentration 

 (3.44 ng/1), exceeding the concentration of the other 

 chloroorganic pesticides more than 10-fold. The HCH isomer 

 ratio, a-HCH versus y-HCH, indicates their presence is probably 

 due to long-distance atmospheric transport. 



In biota, PCB's were measured at levels as high as 

 67.9 ng/g in neuston and 23.9 ng/g in zooplankton. a-HCH 

 concentration ranged from I to 10 ng/g; the isomer 

 concentrations were lower. Chlordanes, DDT. and 

 hexachlorobenzene were present at low concentrations in most 

 samples. Toxaphene was measured in biota for the first time in 

 these seas. Residues were highest in fish at 1 0.8 ng/g. Sediments 

 had low to nondetectable residues of most compounds analyzed. 



The HCH's {a, p. and y isomers) displayed behavior that 

 was different from the other measured organochlorines ( OC s ). 

 Global behavior of these compounds in the world's oceans 

 indicates that higher levels tend to occur in colder waters of the 

 poles rather than equatorial waters, which are geographically 

 closer to the areas of their major use. It has been postulated that 

 the globe may function as a giant distillation device, driving 

 them into the air near the equator where they eventually distill 

 into the cooler waters at the poles. In support of this theory, it 

 was observed that the water concentrations for the HCH 

 isomers did indeed exhibit a gradient for higher water 

 concentration with increasing latitude; this relationship was 

 strongest for the P-HCH isomer. The HCH"s also 

 bioaccumulated to a lesser extent than the other OC"s in this 

 system, e.g., bioaccumulation factors for HCH of 

 5.8 X 10Sersus6.3 x lOM'orthe sum of DDT residues in fish 

 tissue;thisappearstorelatetotheirrelatively low lipid solubility. 



402 



