peaked at 0.5- 1 m, i 50-200 m, and 1 ,500 m at the deep-water 

 stations. At shallow-water Stations 4 and 5. highest 

 concentrations occurred at 0.5, 15, and 45 m. Compared to 

 1984, the numbers of PCB-transforming bacteria had not 

 increased and their vertical distribution remained constant 

 (Fig. 8). 



Vertical variations of PCBB in the northwestern Bering 

 Sea resembled the distribution of both hexadecane and especially 

 BaP-transforming bacteria. Maximum numbers of PCBB 

 (10- cells/ml) occurred in near-bottom waters. At Station 7, 

 which is the farthest from St. Lawrence Island, only 

 10 cells/ml were measured. At Station 35, the density of 

 PCB-transforming bacteria increased to 180 cells/ml at 25 m. 



Fig. 7. Occurrence rate {9c) of samples with various pair comhinations of 

 temperature and salinity in the Chukchi Sea in summer 1988 (a) and 

 mean valuesof numbers (cells/ml ) of hexadecane oxidi/mg (b), BaP- 

 transformmg (c). and PCB-transformina (d) bacteria. 



The horizontal distribution of PCBB in the northwestern 

 Bering Sea, including the Gulf of Anadyr, was highly variable. 

 Mean numbers ranged between 1 and 10 cells/ml at Stations 32 

 and 36; 1 1-100 cells/ml at Stations 7, 9, 10, 13, 19, 27, and 35; 

 and 101-1,000 cells/ml at Stations 24 and 41 (Fig. 1). The 

 variation of PCBB was generally greater than for HDB, but 

 similar to the BaP-transfonning microflora (Fig. 1 ). 



Compared to 1981, the numbers of PCBB in 1988 increased 

 2-3 times, from 100 cells/m in 1 98 1 to 1 80 and 300 cells/ml in 

 1988. The distribution of PCBB also became more extensive 

 in 1988 (Fig. 9). 



Stations 



16(B) 



Fig. 8 Vertical distribution of PCB-transforming bacteria in the central 

 Bering SeatEast Polygontsummer 1984 and I98X. The insert shows 

 location of stations. 



1 10 100 1000 



Fig. 9 Vertical distribution of PCB-transforming bacteria at three stations of 

 North Polygon in the northern Bering Sea near St. Lawrence Island in 

 summer 1981. 1984, and 1988. 

 X - axis = station numbers and indices of stations; and 

 Y - axis = depth (m). 



In the Chirikov basin and the Bering Strait, PCBB varied 

 between and 180 cells/ml. with 39% of all the samples 

 containing 180 cells/ml (Figs. 4,5). Due to significant vertical 

 variability, mean numbers for the various stations never 

 exceeded 100 cells/ml. Only at Station 83 in the Bering Strait, 

 the mean number of PCBB averaged more than 100 cells/ml, 

 ranging from 180 to 690 cells/ml. Distribution of PCBB 

 showed high numbers at 0.5, 45, 250, and 2,500 m. 



In the southern Chukchi Sea, PCBB also varied between 

 and 3.0 x 10' cells/ml (Fig. 2), but concentrations most often 

 fell within the range of 10-100 cells/ml in 29% of all the 

 samples (Fig. 4a). 



Although the mean numbers of PCB-transforming 

 microflora ranged between 10 and 1,000 cells/ml (Figs. 2,6), 

 PCBB at 6 out of 1 8 stations under investigation rarely exceeded 

 100 cells/ml. At the remaining 12 stations, PCBB fell within 

 range of 10 and 100 cells/ml (Fig. 2). In the Chukchi Sea, 10% 

 of samples contained PCB-transforming microflora with more 

 than 10' cells/ml (Fig. 4a). These bacteria were absent in 16% 

 of all those analyzed whereas, in the Bering Sea, as much as 

 30% of the samples had no PCBB (Fig. 4). 



PCB-transforming bacteria showed similar distribution 

 ecograms as other indicator groups in the Bering Sea. Maximum 

 mean numbers of PCB-transforming bacteria 

 (7.4x 10- cells/ml) occurred at stations with high temperatures. 



86 



