Uptake and depuration of PCB 77, PCB 169, and hexachlorobenzene by zebra mussels (Dreissena polymorpha)

Zebra mussels (Dreissena polymorpha) were examined for their ability to take up and depurate hexachlorobenzene (HCB), 3,3',4,4'-tetrachlorobiphenyl (PCB 77), and 3,3',4,4',5,5'-hexachlorobiphenyl (PCB 169) in the laboratory. The intent was to investigate response to acute exposure at high contaminant levels and to observe the time course of depuration. Tissue loads of all three compounds taken up from food increased rapidly and peaked after 10 (PCB 169), 14 (PCB 77), and 21 (HCB) days followed by rapid depuration to equilibrium levels. Peak tissue loads were 3.7, 3.4, and 3.6 micrograms/g for PCB 169, PCB 77, and HCB, respectively (wet weight basis). Equilibrium levels were approximately 1.0 microgram/g for both PCB 169 and HCB. Uptake rate of PCB 77 followed the order: sediment > food > water. Dreissena sampled from five Great Lakes field sites had tissue Aroclor loads ranging from 120 to 530 ng/g for Aroclor 1242 and 33 to 270 ng/g for Aroclor 1254 (wet weight basis). PCB 77 was detected at 1.9 ng/g at one site. Tissue levels for both Aroclors in Dreissena were approximately 10 times those of Lampsilis siliquoidea, a unionid bivalve to which they were attached. Where Dreissena reaches high densities, it is likely to play a significant role in contaminant dynamics.