100 



50 



Station 3 

 P 



10 20 40 60 



Cadmium Concenlralions (pg/ll 



10 20 50 



PCB Concentrations (pg/1) 



100 



S 50 



N 



10 20 40 



Cadmium Concentrations (pg/1) 



60 



10 



20 



50 



PCB Concentrations (pg/1) 



100 - 



50 



10 20 40 



Cadmium Concentrations (pg/1) 



60 



Fig- 



3. Negative effects of Cd concentrations on piimary production (?) and 

 the total number of infusoria (N) on Stations 3. 7, and 9. 



production) for bacterioplankton in Anadyr Bay, on 

 Stations 35 and 7. were very close to critical concentrations for 

 phyto- and microzooplankton in the same area (3-20 |ig/l). 

 The value of P/Bp coefficient increased together with Cu 

 concentrations on Station 7, and we think that 3 |ig/l Cu was 

 very close to the critical concentration for the whole plankton 

 community because this toxic effect disturbs the balance of 

 organic matter significantly (Table 6; Fig. 8). Low 

 bacterioplankton tolerance on Station 35 to Cd and Cu additions 

 probably depends upon the high level of primary production 

 and biomass of phytoplankton. which can suppress 

 bacterioplankton (Tables4,6). The phytoplankton populations 

 most sensitive to Cd additions were located on Stations 3 and 

 9, and the most sensitive microzooplankton populations were 

 at Station 7 (Table 2; Fig. 3). The average Cd critical 

 concentrations for phyto- and microzooplankton in the Bering 

 Sea ecosystem were 40 and 28 |ig/l, respectively (Table 7 ). The 

 critical concentration of Cd to the whole plankton community 

 ( P/Bp - target) on Station 3 was nearly 8 |ig/I (Tables 6,8 ). It was 

 noticed that the sensitivity of plankton to Cd additions, as well 

 as to additions of BaP and Cu, varied significantly among 

 different stations (Tables 1-8; Figs. 1-7). The sensitivity of 



100- 



50- 



20 

 PCB Concentrations (^ig/l) 



50 



Fig. 4. 



Distribution of benthic biomass (gm-) at stations in the Gulf of 

 Anadyr and neighboring waters. 



Station 



100-, 



PCB Concentrations (pg/1) 



20 

 PCB Concentrations 



50 



(|Jg/l) 



Fig. 5. 



Negative effects of PCB concentrations on primary production (?) and 

 total number of infusoria (N) on Stations 18 and 45. 



359 



