of demonstrable differences in the tissue trace metal and PCB 

 concentrations among the three populations located in the western 

 Sound both on (WLISc and 500MW) and off (WLISrN) the disposal 

 site lends further support to the argument presented above. The 

 finding of compositional change of Aroclors in favor of Aroclors 

 1254+1260 in the disposal site populations reflects the high 

 concentration of suspended matter in this region; it is known 

 that more highly-chlorinated biphenyls (biphenyls with more 

 chlorine radicals) such as Aroclors 1254 and 1260 are closely 

 associated with particulates and that lesser chlorinated isomers 

 such as-Aroclor 1242 are water soluble (Duinker et al. , 1982a, b) . 

 One could, therefore, predict that invertebrates which are 

 deposit and suspension feeders would contain more highly 

 chlorinated biphenyls. Such a prediction was verified in Mvtilus 

 edulis (Feng, 1984; the present study) and in the benthic 

 invertebrates Macoma balthica, Arenicola marina and Cranoon 

 crangon from the Dutch Wadden Sea (Duinker et al. , 1983). Thus, 

 in order to resolve the question whether the Aroclor 

 compositional change in the experimental mussel populations was 

 due to environmental availability of the Aroclors or to 

 biological processes (e.g., selective uptake or depuration of 

 Aroclors) , data on the composition of Aroclors in both water 

 (dissolved and particulate-associated Aroclors) and sediment from 

 both the reference and disposal site would be required. 



Biological Effects . Mortality is a common phenomenon in all 

 living organisms which can be ascribed to aging, diseases, and 

 the effects of environmental changes. The key issue is how 

 natural mortalities can be separated from those induced by the 

 effect of pollutants. In the' present study, the heightened 

 cumulative mortalities found in the three mussel populations 

 located in the western Sound are probably the result of abnormal 

 reactions superimposed on the natural seasonal mortality (the 

 latter exemplified by the reference population at Rlr) . When the 

 cumulative mortality curves depicted in Figure 10 are scrutinized 

 carefully, one notices that the onset of heightened mortalities 

 at WLISc and 500MW occurred during July and August; for the 

 populations held at WLISrN and Rlr, the onset was delayed and 

 took place during August and September. Even though the 

 magnitude of the mortalities of the two populations was 

 different, the initial elevated mortalities found at the stations 

 in the western Sound could not have been associated with disposal 

 activities, because there was little or no disposal of dredged 

 material during the summer months at the WLIS disposal site. 

 However, there is a noted increase in cumulative mortalities at 

 the WLISc station from January to March of 1985. This correlates 

 with the time of renewed disposal activity at the WLIS disposal 

 site; because this is the only station to show a marked increase 

 in mortality, it can be surmised that the effect of disposal on 

 mortality, if any, is limited to the immediate disposal area. The 

 high cumulative mortalities found at WLISc, 500MW, and WLISrN in 

 part, are probably related to other environmental conditions, 



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