Numbers were determined by the method of ultimate 

 dilutions, described as early as 1927 by Razumov (1927), 

 which is widely used in similar works (Gunkel, 1967; Atlas, 

 1981; Platpira, 1982, 1985; Shtukova, 1990). The method 

 consists of adding into two to three rows of test tubes, containing 

 a liquid medium or "sea potassium-yeast medium" (SPY). 

 These media were supplemented with hexadecane, BaP, or 

 PCB as the only source of carbon. Dilutions were made in 

 measured volumes of analyzed seawater so that the initial 

 sample in the first test tubes was diluted 1:10, and followed by 

 1:100, 1:1,000, 1:10,000 (etc.) times accordingly. After 

 incubation, test tubes were checked for maximum dilution of 

 the sample that showed growth of the bacterial physiological 

 group understudy. Growth was determined visually by change 

 in transparency and color of the medium. A special statistical 

 McCredy table was used to determine the numbers of bacterial 

 cells per milliliter. When using the method of ultimate dilutions, 

 we assumed that the observed bacterial growth occurred when 

 at least one actively dividing bacterial cell was transferred 

 during inoculation. 



To study SB. fish broth made with seawater from 

 investigated areas was used as a liquid medium, prepared from 

 0.5 kg of fish cooked in 1 liter of water, and diluted 10 times 

 with the same seawater. The medium was poured into test 

 tubes and sterilized in an autoclave with pressure 1 atm 

 (1.01 X 10' Pa) for 20 minutes. To determine the number of 

 other indicator bacteria groups, a liquid SPY medium was used 

 (Tsyban, 1970; Seki, 1986) containing K.HPO^ (1 g), 

 NHjCl ( 1 g), yeast extract (0.5 mg), and seawater ( 1 ,000 ml). 

 These media were poured into test tubes and autoclaved. 

 Sterile substrate, hexadecane, BaP, PCB, or Aroclor 1232 

 (0.01-1%) was added into test tubes after inoculation. 



The SPY medium, as an elective media, has found extensive 

 application in the practice of marine microbiology ( Seki, 1 982; 

 Tsyban etai, 1985; Izrael & Tsyban, 1989). 



The statistical method of prismatic ecograms was used to 

 analyze the results (Tsyban, 1970). 



Results and Discussion 



Saprophytic Bacteria in the Bering and Chukchi Seas 



In the central Bering Sea (East Polygon), the MPN of SB 

 varied within the range of 0-1.8 x 10' cells/ml, 

 222^40 cells/ml for the investigated stations. These bacteria 

 varied with depth at Stations 1, 2, and 3 of about 

 3,000 m deep. Maximum concentrations of more than 

 1,000 cells/ml occurred at depths 10-25 m (thermoline), 150, 

 500, and 2,500 m. The above bacterial groups were not 

 discovered at Station 1, 15 m and 3,000 m; at Station 2. 

 2,000 m; Station 3, surface microlayer; or Station 4, 25 m. At 

 shallow-water stations ( Stations 4 and 5 ), SB increased only in 

 deep-water and near-bottom layers of waters deeper than 

 100 m. Such distribution of microflora reflected water masses 

 heterogeneity in this sea area. Compared to 1984 (Izrael c? a/., 

 1988; Tsyban el al., 1990), the number of SB at East Polygon 

 remained constant (0-10'' cells/ml), but their vertical distribution 

 varied with depth. 



In the northwest Bering Sea at the sections near 

 St. Lawrence Island, SB distribution was also variable. 

 Maximum concentrations ( 10' cells/ml) occurred at depth and 

 in the near bottom layers of Stations 7, 18, and 19. Overall, the 

 vertical distribution of this group of microorganisms showed 

 an increase in numbers with increase in depth. At Station 36, 

 not far from the St. Lawrence Island, the SB (10- cells/ml) 

 remained constant over the entire water column from 1 5 m to 

 the bottom. At other stations SB in the upper layers of water (0, 

 5, and 10 m) ranged from 10' to 10' cells/ml. 



Distribution analysis of mean SB number showed that 

 maximum mean MPN values were typical for Station 7 

 (2.4 X 10' cells/ml). At other stations of the section (with the 

 exception of Station 35), mean values for saprophytes varied 

 between 105 and 360 cells/ml. At Station 35, the SB mean was 

 about 96 cells/ml. 



First studies of microflora of the Gulf of Anadyr were 

 made during this cruise. Numbers varied across a very wide 

 range from zero to 1.8 x 10^ cells/ml. Maximum values 

 occurred at Stations 24 and 27. At Station 1 1, SB did not range 

 greatly — 0-300 cells/ml. mean 56 cells/ml. At Station 41, 

 situated between the Gulf of Anadyr and Chirikov basin, SB 

 averaged 7.1 x 10' cells/ml. Vertical distribution of saprophytes 

 was variable, with a trend towards increasing concentration 

 with depth (Fig. 1 ). 



In the Chirikov basin and Bering Strait, SB varied vertically 

 and horizontally. Overall, concentrations ranged between 

 and 1.8 x 10' cells/ml. At Stations 96, 100, 102. and 104. cell 



C>7 



Fig. I. Vertical distribution of mean values of the most probable number 

 (MPN) of heterotrophic-saprophytic (a), hexadecane oxidizing (b), 

 benzo(a)pyrenc transforming (c) and PCB-transforming (d) bacteria 

 at stations in the northwestern Bering Sea and the Gulf of Anadyr in 

 summer 1988. 



82 



