PCBs, DDE, and mercury in young-of-the-year littoral fishes from Green Bay, Lake Michigan

Forage fish were collected in August and September, 1991 to characterize the influence of human disturbance at 23 coastal wetlands and beaches in Green Bay, Lake Michigan. Disturbance characterization included analysis of contaminant residues (total PCBs, p,p'-DDE, and total mercury) in young-of-the-year fish for at least one species per site. Yellow perch (Perca flavescens) and spottail shiners (Notropis hudsonius) were the primary species sampled. Residue concentration differences among species were minimal. Residues of PCBs were highest of the three compounds measured and were the only residues that exceeded International Joint Commission Aquatic Life Guidelines: all 14 fish samples from the lower bay exceeded the 100 ng/g PCB guideline. Based on the concentration gradient measured, the Fox River is the primary source of PCBs; whereas, the more evenly distributed p,p'-DDE and mercury appear to originate mostly from nonpoint sources. The high percentage of more-chlorinated PCB homologs in upper bay fish supports the hypothesis that less-chlorinated PCBs volatilize more quickly and therefore are less abundant farther from their source. Habitat-specific delta suggest that contaminants (particularly PCBs) are more available to biota at beaches than at wetlands.