Venical and horizontal disinbuiion of cells. 



Fig. 3. Distribution of bacterial population in the Gulf of Anadyr of the 

 Bering Sea, summer 1988. 



to compare them with the data obtained in previous years. 

 Relating bacterial numbers, biomass, and activities with other 

 oceanographic parameters, it was possible to analyze the 

 microbiological conditions with increasing anthropogenic load 

 in the Bering Sea ecosystem. 



Total Number, Biomass. and Activity of Bacterioplanktim in 

 the Chukchi Sea 



Until recently, there has been no microbiological studies 

 in the Chukchi Sea ecosystem. The first investigations, 

 conducted in suinmer 1988, focused on bacterioplankton, their 

 distribution, and biological status of the microbiocenoses. 

 Microbiological studies included variance across the region, 

 vertical distribution of bacterial nuinber, biomass, and activity. 



The Chukchi Sea is one of many adjacent seas of the Arctic 

 Ocean. It freely communicates with cold waters to the north 

 and limitedly with the Pacific. Nevertheless, every year 

 30,000 km' of water flow into the Chukchi Sea from the Pacific 

 through the Bering Strait (Dobrovolski & Zalogin, 1982). Sea 

 water teinperatures depend mostly upon solar warming and 

 autumn-winter cooling. The space-time scales for salinity 

 depend on the inflow of Pacific waters and river waters from 

 coastal areas. The horizontal and vertical variance of dissolved 

 oxygen and biogenic elements affect the formation and growth 

 of microbiocenoses. 



The analysis of results (Table 2) shows that total number 

 of bacteria and their biomass in the Chukchi Sea varied across 

 locality and depths. In coastal waters of Chukchi and Alaska, 

 maximum numbers and biomass of bacteria occurred. These 

 regions are strongly influenced by both river effluence and 

 Pacific Ocean waters. Deep-ocean waters from the Pacific, 

 which are warm and enriched with biogenic nutrients, penetrate 

 through the Bering Strait and mix with Chukchi Sea, resulting 

 in varied growth and distribution of microbiocenoses across 

 the Chukchi Sea. The activity of Chukchi littoral bacteria was 



high and equal to that of mesotrophic waters. Bacterioplankton 

 showed the lowest activity in Alaskan waters. The distribution 

 of bacterioplankton along sections across different water types 

 (Fig. 4) can be attributed to water depths (0-45 m), temperature 

 (0. 1-5.2°C), salinity (30.6% to 33.6%), and dissolved oxygen 

 (from 51% to 98%). 



TABLE 2 



Assessments of population, biomass and dark CO, assimilation by 

 bacteria in Chukchi Sea Waters, summer 1988. 



Sea regions Total population Bacterial 



explored of bacteria bioinass 



10' cells/ml (/igC/1) 



Dark CO, 

 assimilation 

 by bacteria, 



pg C/l/d 



Maximum density of bacteria (averaging 

 997 X 10' cells/ml) occurred near the bottom in the Chukchi 

 Coastal waters. In the euphotic zone and surface layer bacteria 

 and their biomass were almost 1 .5 times lower than those near 

 the bottom. 



In the Alaska littoral zone, bacterioplankton were most 

 abundant between and 25 m. In this layer, numbers and 

 biomass averaged 92 1 x 10' cells/ml and 17.92 mgC/m'. In the 

 surface microlayer and near the bottom bacterioplankton were 

 somewhat lower than the euphotic zone. 



Due to mixing in the northern area of the sea, bacteria 

 remained constant with depth as did hydrological and chemical 

 factors. In the Chukchi Sea, the growth of bacteria equalled 

 that of mesotrophic waters. The highest number of 

 bacterioplankton occurred at Station 46. where bacteria and 

 their biomass averaged 1.154 x 10' cells/ml and 

 25.96 mg C/m'. respectively. High bacterial activity also 

 occurred at Station 45. The highest daily dark CO, assimilation 

 by bacteria was averaged (2.08 /ig C/1) at Station 50. where 

 bacterial numbers and biomass average 765 x 10' cells/ml and 

 17.01 mg C/m'. respectively. Vertically, total number, biomass, 

 and activity of bacterioplankton increased from the surface 

 microlayer to the bottom (Fig. 3). 



The waters in the central basin of the Chukchi Sea showed 

 variable temperatures and dissolved oxygen. Waters mixing 

 over this area distributed bacteria within specific localities. 

 Maximum numbers occurred at Stations 55 and 74, and 

 numbers and biomass of bacteria averaged 1,028 and 



59 



