BIOMAGNIFICATION OF POLYCHLORINATED-BIPHENYLS THROUGH A RIVERINE FOOD-WEB

From 1989 to 1993, biota collected from Pottersburg Creek, London, ON, Canada were analyzed for total polychlorinated biphenyls (PCBs) and l ipids. Data were analyzed by analysis of covariance (ANCOVA) with lipi d as the covariate, to investigate station, time, and trophic effects on PCB accumulation in aquatic organisms. All three variables were hig hly significant (p < 0.0001). PCB concentrations in biota decreased al ong the length of the creek away from the point source. PCB concentrat ions in biota collected in July 1993 were not significantly different from concentrations in biota collected in July 1990 (p > 0.16), sugges ting that sources into the creek have not been alleviated. The relatio nship between PCBs and lipid for biota from Pottersburg Creek suggests that organisms accumulate PCBs relative to their position in the food web (p < 0.0001). Fish and leeches occupying the top of the food web accumulated more PCBs than organisms occupying a lower trophic positio n (crayfish and oligochaetes/ chironomids), indicating that biomagnifi cation through trophic transfer (i.e., the uptake of a chemical throug h ingestion) is the primary mechanism governing contaminant levels in biota and not bioconcentration (i.e., the uptake of a chemical from wa ter).