critical C' centration values in the Bering-Chukchi Sea to 

 those foi the Baltic Sea, a highly polluted region, it was found 

 that the Baltic was more susceptible to PCB's and BaP but 

 slightly less susceptible to Cu and Cd. For the Bering and 

 Chukchi Seas, BaP and Cu are the two pollutants whose critical 

 concentration levels approached the natural levels that were 

 found for this region; therefore, these pollutants may be having 

 an impact in this region. 



Toxicity of a- and y-HCH to natural communities of 

 microplankton were tested. At concentrations from 80 to 

 100 ng/1, distinct effects were observed on the ambient 

 ammonium pool and '''N ammonium uptake rates, both of 

 which increased in the experimental containers. 



Bacterial activity per cell increased in the oceanic experiments 

 and decreased in the shelf experiment. These tests indicate that 

 HCH has the capability of altering plankton nitrogen cycling in 

 open ocean systems. 



A sediment bioassay technique was employed to examine 

 the toxic potential of sediment collected from several regions 

 throughout the study area. Standard single species test protocols 

 were carried out employing Artew/a salina (brine shrimp), and 

 a dinoflagellate, Pyrocystis lonula. No acute effects were 

 observed. These first time tests provided benchmark values 

 that will be useful to future studies monitoring the status of 

 these waters. 



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