The bacterial density and biomass varied considerably 

 between stations. Maximum average values of total numbers 

 (1,103 X 10' cells/ml) and bacterial biomass (24.83 mg C/m') 

 occurred at Station 6 and minimum values at Station 1 8, where 

 values averaged 513 x 10' cells/ml and 11.55 mg C/m\ 

 respectively. 



The distribution of bacterioplankton in the water column 

 also varied with depth (Figs. 1,2). Numbers increased at the 

 thermocline. In contrast to East and South Polygons, the 

 surface microlayerhere lacked high concentrations of bacteria. 

 Total numbers and biomass of bacteria averaged 

 691 X 10' cells/ml and 15.5 mg C/m', respectively. Highest 

 density of bacterioplankton occurred in the euphotic zone, and 

 cell number and bacterial biomass averaged 790 x 10' cells/ml 

 and 17.8 mg C/m', respectively. Bacterial numbers declined 

 with depth, but near the bottom, numbers reached a density of 

 708 X 10' cells/ml. 



Vertical and honzontal distribution 

 86 89 100 104 



, ■ 



05 

 10 



E 15 



t 25 



a 







os' 



10 



15 



Vertical and horizontal distribution 



Scale 10 /ml 



05 10 15 



Fig. 1. Distribution of bacterial population in the northern Bering Sea, 

 summer 1988. 



Compared to other areas, bacteria in the central basin 

 showed the lowest activity (Table 1 ), and rates of dark CO, 

 assimilation compared with those in oligotrophic waters. 

 Maximum activity of bacterioplankton occurred at Station 7, 

 where rates averaged 1 . 1 1 /ig C/l/d. At Stations 6, 1 8, and 19, 

 all rates varied between 0.20 and 0.30 jjg C/l/d. 



In the surface microlayer and euphotic zone, microflora 

 showed similar rates of dark CO, assimilation, averaging about 

 0.50 ng C/l/d. Near the bottom, rates averaged 0.37 /Jg C/l/d. 

 Thus, in the central basin with shallow depths and strong 

 thermocline, the bacteria numbers and biomass are modest but 

 bacterial activity is low. 



In the Gulf of Anadyr, river effluence influenced microbio- 

 cenoses. The Anadyr River discharges nearly 41 km' yearly 

 into the Gulf of Anadyr (Dobrovolski & Zalogin, 1982). 



Fig. 2. Distribution of bactenal population in the southern Bering Sea, 

 summer 1988. 



During the summer, surface salinities in the gulf waters declined, 

 and terrestrial microorganisms and suspended organic matter 

 of terrigenic origin enter the sea. Consequently, bacteria that 

 absorb to suspended matter may seriously influence the structure 

 of coastal bacterial populations. 



Total numbers and biomass of bacterioplankton in the 

 Gulf of Anadyr are high (Table 1 ) and as high as those in the 

 northern basin. Maximum numbers and biomass occurred at 

 Stations 24 and 26 located in the gulf coastal waters, with 

 minimum values at Station 22 nearest the open sea. Vertical 

 profiles of bacterioplankton showed some increase in both 

 numbers and biomass with depth (Fig. 3). The bulk of 

 bacterioplankton concentrated in the euphotic zone where total 

 numbers and biomass averaged 910 x 10' cells/ml and 

 20.5 mg C/m', respectively. Near-bottom waters contained the 

 lowest density of bacteria in the water column. 



Bacterioplankton in the Gulf of Anadyr showed the lowest 

 activity relative to other studied areas. This suggests that most 

 of the microflora were dormant. The highest activity of 

 microbiocenoses occurred at Station 26, the lowest activity at 

 Station 1 1 . Dark CO, assimilation by bacteria at those stations 

 averaged 1.11 andO. 17 ^ug C/l/d, respectively, and distributed 

 evenly throughout the water column. Dark CO, assimilation in 

 the surface microlayer, euphotic zone, and near the bottom 

 ranged between 0.48 and 0.50 ^ug C/l/d. Thus, high density of 

 bacterioplankton and low activities of microbiocenoses 

 characterized the shallow Gulf of Anadyr with its sharp 

 thermocline and low surface salinity. Generally speaking, 

 bacteria remained constant with depth, although at Stations 1 5 

 and 22, highest numbers and activities of bacterioplankton 

 occurred at the thermocline. 



In conclusion, by studying bacteria in the Bering Sea in 

 summer 1988, it was possible to assess the status and variance 

 of total number, biomass, and activities of bacterioplankton in 

 relation to different hydrological and chemical conditions and 



58 



