Validating possible effects of eutrophication using PCB concentrations in bivalves and sediment of the US musselwatch and benthic surveillance programs

In order to examine the possible interactions of eutrophication and hydroph obic organic contaminants, data for polychlorinated biphenyl (PCB) concentr ations (C-PCB) in three species of bivalves and in sediments were examined. These were correlated to total organic carbon content of sediments (TOCsed ), which was assumed to represent the trophic status of the sampling sites. Almost all C-PCB on dry weight basis in the bivalves and in the sediments were positively linearly correlated to TOCsed. Regarding the sediments, thi s simply reflects the high affinity of these compounds for TOC, but for the bivalves the correlation was not explained. In the bivalves, the differenc e in PCB homologue concentration was positively linearly correlated to TOCs ed. To understand these field data, a box model was used to simulate the fa te of PCB in oligotrophic, mesotrophic, eutrophic, and hypertrophic marine environments. The calculated results qualitatively predicted the change in C-PCB for the sediment correctly. For increased trophic status of the water compartment, on a scale from oligo- to hypertrophic, the model predicted d ecreasing fugacities for the PCBs, and thus could not support the observati ons of increased bivalve C-PCB seen in the field data study. It was suggest ed that the PCB pattern change in the bivalves could be influenced by algae -growth dynamics in the watercolumn. This would selectively intensify the w ashout of the lighter chlorinated homologues from the water and, thereby, d ecrease their concentrations in the bivalves.