Fig. 5. Vertical distribulion of mean values of saprophytic (a), hexadecane 

 oxidizing { b), BaP-transfomiing (c ). and PCB-transforming ( d) bacteria 

 at stations in the northern Bering Sea (Chirikov basin) in summer 

 1988. 



oxidizing microflora were also high in waters with temperatures 

 <6°C, but with relatively high salinity (>33%) (Fig. 6). In the 

 Chukchi Sea, the highest mean number of DB 

 (6.6 X 10- cells/ml) (Fig. 7) were found in waters with 

 temperatures between +2°C and +6°C and salinity between 

 31.35% and 33.00%. Such conditions occurred in 60% of all 

 the samples (Fig. 7). 



This analysis of hexadecane-oxidizing microtlora in the 

 waters of the Bering and the Chukchi Seas confirms that these 

 waters remain relatively unpolluted. The waters of the northern, 

 central, and especially southern areas of the Bering Sea have 

 experienced aliphatic hydrocarbon inputs of natural or 

 anthropogenous origin. 



Benzo(a)pyrene Transforming Bacteria in the Bering and 

 Chukchi Seas 



Mean numbers of BaPB in the northwestern Bering Sea, 

 includingtheGulfof Anadyr, averaged about lO'ceils/ml. The 

 highest concentration of BaPB occurred at Stations 24 and 27 

 near the coastal zone and at Station 41 between the Gulf of 

 Anadyr and the Chirikov basin (Fig. 1). 



The vertical distribution of BaP-transforming microflora 

 followed a similar distribution for hexadecane-oxidizing 

 microflora. However, in the Chirikov basin, high mean numbers 

 of BaPB were not only found at Stations 83 and 89. but also at 

 Stations 86 and 104 (Fig. 5). Similar numbers occurred in the 

 Chukchi Sea (Fig. 2). 



In the central and southern Bering Sea, BaPB varied 

 between 0-3.0 x 10"" cells/ml, but most often values fell 

 between 10 and 100 cells/ml (28%^ of all the samples) and 

 100-1,000 cells/ml (29% of all the samples), respectively 



N. celli/ml 

 500—1 



Fig. 6. 



Occurrence rate (R,%) of samples with various pair combinations of 

 temperature and salinity in Bering Sea in summer 1988 (a), and mean 

 numbers of hexadecane oxidizing (b). BaP-transforming (c). and 

 PCB-transforming (d) bacteria (cells/ml) in the above samples. 



(Fig. 4). As for BaPB distribution, the open waters in the 

 central and southern Bering Sea differed from other areas. 

 Here, 40% of samples possessed low BaPB numbers, whereas 

 only 11% of samples contained more than 1,000 cells/ml 

 (Fig. 4). Water samples with relatively high temperatures 

 (>6°C) and salinity (>33%) in the southern Bering Sea again 

 contained the highest mean numbers of BaP transforming 

 microorganisms, 8.9 x 10- cells/ml (Fig. 6). 



In the Chukchi Sea, highest mean numbers of BaPB 

 (6.0 x 10- cells/ml) occurred in water samples with relatively 

 low salinity (<31.35%) and temperatures between 2°C and 

 6°C. Such conditions exist in the surface waters at Stations 45 

 and 59, a coastal area affected by the Siberian rivers outflow, 

 and at Station 53 in Alaska Coastal waters ( Figs. 2,7). Compared 

 to 1 984 and, as far back as 1 98 1 , the number of BaP-transforming 

 microflora in the Bering Sea in 1988 has increased at a number 

 of stations, and their distribution has become more extensive. 



Polychlorinated Biphenyls-transfonning Bacteria in the Bering 

 and Chukchi Seas 



In 1981, research in the Bering Sea began on the number 

 and distribution of heterotrophic bacteria that transform PCB's 

 and has continued in summers 1984 and 1988. 



At the East Polygon, in the central Bering Sea, the PCBB 



varied between and 180 cells/ml. Maximal concentration, 



3.0 X 10' cells/ml, was measured at only 150 m at Station 1. 



The distribution of this bacterial group varied with depth, but 



85 



