also followed the increase in all numbers (Fig. la.b). However, 

 after 10 days biotransformation decreased as most of PCB 

 congeners remained practically unchanged. 



Figure 2 shows Aroclor 1232 chromatograms that reflect 

 the change in concentrations of individual PCB congeners over 

 the experiment period. The concentration of congeners varied 

 from to 10%. 



Experimental data (Table 3; Figs. 3,4.5) indicate a great 

 similarity in the rates of PCB transfomiation in various regions 

 of the Bering and the Chukchi Seas. In the Chukchi Sea. with 

 a thawing ice flow and a low salinity of 24.04%. the change in 

 the MPN of bacteria under study and the rate of Aroclor 1232 

 transformation were similar to those found in the Bering Sea 

 (Figs. 1,5; Table 3). Controlbottles with sterile water and PCB 

 concentrations at 100 ng/l or 10 ng/1 remained unchanged. 



cells/ml 



10 



10 



10 



1 



10 



14 



€ PCBB 



I 

 21 



days 



Fig. .^a. Most probable number (MPN) of saprophytic bacteria (SB, 

 cells/ml) and PCB transforming bacteria (PCBB, cells/ml). 



TABLE 3 



Transformation rate (degradation percentage) of individual 

 Aroclor 1232 congeners by bacterioplankton of the Bering and the Chukchi Seas. 



Experiment 

 Numbers 



Congeners 

 Numbers 



Initial concentration of PCB 

 100 ng/1 



1 ?• 5 10 14 21 



day days days days days days 



Initial concentration of PCB 

 10 ng/1 



I 3 5 10 14 21 



day days days days days days 



^ 



s 



10 



II 



13 



14 



5 

 8 



15 

 18 



22 



28 



31 



40 



44 



47 



52 



60 



66 



70 



77 



87 



97 



101 



153 



5 

 8 



15 

 18 

 22 

 28 

 31 

 40 

 44 

 47 

 52 

 60 

 66 



98 



