IMW Initial Phase Report 



observed when the concentrations measured in Crassostrea rizhophorae are compared to those 

 encountered in Mytella guayanensts or Anomalocardia brasiliana. 



If Crassostrea rizhophorae is used as a reference to link these species, it is reasonable to 

 expect that, when exposed to the same environmental concentrations, Isognomon alatus will 

 accumulate these chemicals to a slightly larger extent than Mytella falcata, Mytella guayanensis 

 and Anomalocardia brasiliana. Except for total chlordane, the concentrations will be within a 

 factor of two to three. The differences observed among Mytella falcata, Mytella guayanensis and 

 Anomalocardia brasiliana are small. 

 Aulacomya ater, Choromytilus chorus and Mytilus platensis 



Aulacomya ater was found to share substrate with two different species of mussels, 

 Choromytilus chorus and Mytilus platensis, in Chile and Argentina, respectively. As shown in 

 Figure 16, Aulacomya ater seems to contain slightly higher concentrations of HCHs, chlordanes, 

 DDTs and PCBs compared to the other two species of mussels. The concentrations observed in 

 Aulacomya ater, however, are not larger than threefold higher than those measured in 

 Choromytilus chorus or Mytilus platensis. 

 Semimytilus algosus and Perumytilus purpuratus 



These two species of mussels were collected off the rocky coasts off Paracas, Peru. 

 Concentration differences (Figure 16) between both species were small, i.e. less than 50%, for all 

 analytes. 

 General Comment 



In spite of being exposed to the same environmental habitat concentrations of HCHs, 

 chlordanes, DDTs and PCBs, there appear to be several small differences when comparing tissue 

 concentrations in species collected at the same or nearby sites. Most tissue concentration 

 differences were within a factor of three or less but these differences are of interest when trying to 

 understand the relationships between habitat exposure and tissue concentration in different species. 

 These small differences permit the broad global region comparisons we originally sought to make 

 in the IMW program even though there were several species sampled. In a similar study with 

 oysters and mussels for the NOAA's National Status and Trends Program, O'Connor (1991) 

 similarly reported concentration differences for total PAHs, DDTs, PCBs and chlordanes to be 

 within a factor of two to three. 



CHLORINATED PESTICIDES AND PCBS 



In this discussion of the results of analysis of samples from the IMW Phase I Region, we 

 utilize summary plots of data for ease of viewing, but remind the reader that all the data are 

 presented in tabular form in Appendix A. We will not attempt an exhaustive interpretation of the 

 IMW data in this report. Our purpose is to present the first order interpretations 



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