Bacterial production was calculated by the fomiula 



Pb =:Q.x16.6, 



where 



Pg = bacterial production, |ag C/l/d; 



Q, = quantity of 14 CO, assimilated, |ig C/l/d; 



16.6= relationship of total biomass carbon and 



biomass synthesized from carbon dioxide 



(100:6). 



To assess mineralization processes of organic matter, 

 biochemical oxygen demand ( BOD) is usually used. In practice, 

 BOD is more often determined after 24 hours of exposure 

 under in situ conditions. Presently, there is no single and 

 reliable technique for BOD determination. "Bottle" technique 

 over-estimates the oxygen demand of bacteria and is labor 

 intensive. Apart from that, the effectiveness of the oxygen 

 technique in eutrophic waters to determine destruction of 

 organic matter in waters with low temperature and primary 

 production is difficult. In mesotrophic and oligotrophic waters, 

 the radioisotope technique is extensively used to measure 

 destruction of organic matter which is more sensitive and less 

 labor intensive. The application of this technique is due to the 

 relationship between oxygen demand and heterotrophic 

 assimilation of CO, by bacteria (Romanenko, 1965), where 

 7 mg C/CO, is assimilated per mg of oxygen used for bacterial 

 respiration. Hence, there is a coefficient to determine the 

 quantity of oxygen consumed by bacteria relative to 

 heterotrophic assimilation of CO,. 



Oxygen used by bacterial respiration was calculated by the 

 formula 



where 



O, = 



Ct = 



7 = 



O, = Cj/l. 



oxygen deinand for organic matter 



destruction, mg 0,/l/d; 

 dark CO, assimilation, |ag/l/d; 

 Coefficient between oxygen demand and 



CO, assimilation. 



Results and Discussion 



Bacterial Production and Organic Matter Destruction in the 

 Bering Sea 



The change in bacterial numbers and biomass does not 

 determine their biological state and role in marine ecosystems. 

 These questions can be assessed by means of a sensitive 

 radiocarbon technique to measure the bacterioplankton 

 respiration. 



The data obtained in summer 1988 (Table 1) show 

 considerable variance in the rate of bacterial production 

 (1.5-135 |ig C/l/d) and destruction of organic matter 

 (4.8^35.0 |ig C/l/d). Production in the Bering Sea averaged 

 17.3 ng C/l/d or 28.4 fig C/m'. The destruction of organic 



TABLE 1 



The rates of bacterial production and destruction of 

 oraanic matter in the Berins Sea in summer 1988. 



Investigated 

 sea areas 



Bacterial 

 production 



Organic matter 

 destruction 



P/B 



Hg C/l/d gC/m- ngC/yd g C/m- 



Benna 

 Strait 



8.0-28.9 0.7 25.7-92.7 



16.4 52.7 



2.4 



1.1 



2.5 



1.0 



matter averaged 55.7 |ig C/l/d or 9 1 .2 fig C/m-. These rates are 

 20 times higher than similar estimates obtained in summer 

 1981 and 1984 (Tsyban et al., 1987a). These rates also 

 equalled production and destruction processes in mesotrophic 

 marine ecosystems (Sorokin, 1980). 



High rates of bacterial production and destruction of 

 organic matter occurred in eastern and south Bering Sea 

 (e.g.. East and South Polygons). Maximum rates, found at 

 Stations 3 and 108, averaged 47.8 and 153.7 |ag C/l/d, 

 respectively. 



Low rates of bacterial production occurred between 

 0.5—15 m at Stations 5 and 109, where rates averaged 8.3 and 

 1 5.8 ng C/l/d, respectively. Rates of organic matter destruction 

 at these stations averaged 26.8 and 50.9 |ig C/l/d. These rate 

 processes in 1988 are 10 times higher than those measured in 

 1981. The rates of bacterial production and organic matter 

 destruction varied considerably across the eastern and south 

 Bering Sea areas (Table 1). Thus, southern and eastern Bering 

 Sea were characterized by high but variable rates of bacterial 

 production and organic matter destruction across the basin. A 

 high production/biomass (P/B) coefficient was also obser\'ed 

 in eastern Bering Sea (Table 1 ). 



In the central basin and in the Gulf of Anadyr, low rates of 

 production and destruction occurred even though the total 

 numbers of bacterioplankton in these areas were higher than in 

 the southern and eastern Bering Sea (Tsyban et a!. , Section 4. 1 , 

 this volume). The rate of bacterial production and organic 



76 



