numbers averaged 10- cells/ml, and at Stations 89, 92, and 104, 

 numbers averaged 10' cells/ml. At Station 102, in the 

 southeastern part of the basin, SB averaged only 1 70 cells/ml, 

 but near the Alaskan shore (Station 92) we found the largest 

 concentrations (4.4 x 10' cells/ml) in the Bering Sea. 



In the deep Bering Sea (South Polygon), SB ranged from 

 to 1.8 X 10' cells/ml, but mean values (per station) were 

 higher, 1.3-2. 6 X 10' cells/ml. Compared to 1984(Izraelc/^j/., 

 1988; Tsyban er ai. 1990), the numbers of SB increased 

 slightly. In 1984, they were within the range of 

 0-3. Ox lO'cells/ml. Themean values were also higher in 1988 

 than in 1984. Distribution of these bacteria varied over water 

 column depth. Saprophytic microflora in the near-surface 

 microhorizon (0-2 cm thick) were absent or in extremely low 

 numbers at Stations 108, 1 10, and 1 12. 



In summer 1988, the first microbiological survey in the 

 southeastern Chukchi Sea was made. The area was characterized 

 by two large sources of biogenous elements. Here, inorganic 

 nitrogen compounds were being advected through the Bering 

 Strait and along the coastal Siberian Current. Biogenous 

 elements also originated from the Chukchi and Alaska Rivers. 

 Through the combination of these flows, a wide area with high 

 rates of primary production of organic matter by phytoplankton, 

 was fonned in the southeastern Chukchi Sea. In the process of 

 photosynthesis, phytoplankton excrete newly synthesized 

 organic matterthat is substrate forbacterioplankton. Extensive 

 growth of phytoplankton is usually accompanied by increased 

 numbers of SB (Gocke, 1977; Rheinheimer, 1977, 1985). 



Indeed, our results show that the numbers of SB were 

 higher in the Chukchi Sea than in the northwestern and northern 

 parts of the Bering Sea. The number of SB varied between 

 1.8 and 2.0 x 10^ cells/ml, with averages between 0.4 and 

 16.6 X 10' cells/ml. Highest mean numbers of SB occurred in 

 the coastal zone of Alaska (Station 66, 1 1.2 x 10' cells/ml; 

 Station67, 16. 6x 10' cells/ml). High mean numbers of SB also 

 occurred at Station 55, 10.3 x 10' cells/ml. At other stations in 

 the Chukchi Sea, mean values varied between 

 0.4 X 10' cells/ml (Station 74) and 9.6 x 10' cells/ml (Station 

 57; Fig. 2). Vertical distribution of bacteria varied little over 

 depth. At Stations 50, 55, 61, 67, and 69, SB distribution 

 remained constant with depth and varied by no more than one 

 order of magnitude at Stations 50, 61, and 69 

 ( 10--10' cells/ml). At other stations, SB varied by 2-3 orders 

 of magnitude. The largest variation was observed at Station 49 

 (3-1.8 X 10-* cells/ml). 



Analysis of SB in the Bering and Chukchi Seas Relative to 

 Temperature and Salinity 



During the time of expedition in the Bering Sea, water 

 temperatures varied from - 1 .6°C to + 1 0. 1 °C and salinity ranged 

 from 29.73% to 34.64%. For analysis, we grouped samples to 

 both temperature and salinity (Fig. 3a). In the Bering Sea, 27% 

 of the water samples fell in the temperature range between -2 

 and +2°C; 40% between +2 and +6°C; and 33% between +6 

 and + 10°C. The waters of the Chukchi Sea, in comparison with 

 the Bering Sea, was colder. The majority of samples (65% ) fell 

 within the temperature range between +2 and -i-6°C, and only 

 10% of samples had temperatures exceeding +6°C. 



Fig. 2. Vertical distribution of mean values of saprophytic (a), hexadecane 

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

 at stations in the Chukchi Sea in summer 1 988. Numbers near symbols 

 are station numbers. 



N«IO cells/ml 

 6 — I 



Fig. 3. Occurrence rate (%) of samples with various combinations of 

 temperature and salinity in pairs in the Bering (a) and the Chukchi (b) 

 Seas in summer 1988. and mean values of heterotrophic saprophytic 

 bacteria number in the above samples from the Bering (c) and Chukchi 

 (d)Seas. Number of bacteria are 10' cells/ml. 



83 



