Bioconcentration and redeposition of polychlorinated biphenyls by zebra mussels ( Dreissena polymorpha) in the Hudson River

Abstract

The potential impact of zebra mussel infestation on the dynamics of polychlorinated biphenyls (PCBs) in the Hudson River was determined by investigating the biodeposition and bioconcentration of PCBs, using algal food contaminated with 2,5,2′- and 2,4,2′,4′-chlorobiphenyls (CBPs) in the laboratory. Approximately 46–90% of the total food was ingested depending on the supply rate. The highest proportion of ingested congeners was found in biodeposits (64±11% for 2,5,2′-CBP, and 52±6% for 2,4,2′,4′-CBP), followed by tissues (17±3% for 2,5,2′-CBP, and 23±5% for 2,4,2′,4′-CBP), and the lowest in shells. The clearance rate decreased with increasing food concentration, but increased with dilution rate. On the other hand, ingestion rate (IR) increased with food concentration and dilution rate. IR also increased with food supply rate (food concentration×dilution rate) following the same linear function whether the supply rate was varied through food concentration or dilution rate. Therefore, the dilution rate- or food concentration-dependent variation in IR was due to the change in the food supply rate. IR was independent of the kind of PCB congeners. The trend of bioaccumulation in mussel tissues from food ingestion was similar to that of IR; bioaccumulation increased linearly with food supply rate, whether the supply rate was varied through the dilution rate or the food concentration. The bioaccumulation of 2,4,2′,4′-CBP was significantly higher than that of 2,5,2′-CBP ( p<0.05). The bioaccumulation was linearly related to the IR or to the total amount of food ingested. Assimilation efficiency, PCB incorporated in the tissue per total ingested PCB, was higher for 2,4,2′,4′-CBP than for 2,5,2′-CBP ( p<0.05). The congener concentration in biodeposits increased with food supply rate. However, the concentration of 2,5,2′-CBP was significantly greater than that of 2,4,2′,4′-CBP in a mirror image of bioaccumulation. These results indicate that zebra mussels may significantly alter PCB dynamics in the Hudson River through redeposition from the water column and through bioconcentration.