THE ROLE OF THE ZEBRA MUSSEL, DREISSENA-POLYMORPHA, IN CONTAMINANT CYCLING .1. THE EFFECT OF BODY-SIZE AND LIPID-CONTENT ON THE BIOCONCENTRATION OF PCBS AND PAHS

The zebra mussel, Dreissena polymorpha, a recent invader to the Great Lakes, may influence contaminant cycling by bioconcentrating high leve ls of hydrophobic contaminants in its tissue. To better understand zeb ra mussel bioconcentration and ultimately, contaminant cycling, we mea sured bioconcentration factors (BCFs) and kinetic parameters for accum ulation of polychlorinated biphenyl and polycyclic aromatic hydrocarbo n congeners for two size classes of mussels and for a pre-spawning (hi gh lipid) and post-spawning (low lipid) mussel population. High lipid, pre-spawning mussels had greater BCFs and faster uptake kinetics for the highly hydrophobic compounds, i.e, hexachlorobiphenyl and benzo(a) pyrene, than the low lipid, post-spawning mussels. BCFs and uptake kin etics determined for the less hydrophobic compounds, i.e., tetrachloro biphenyl and pyrene, were not measurably influenced by differences in lipid content. Small mussels (15 mm shell length) had higher BCFs and faster uptake kinetics for all compounds compared to larger (21 mm she ll length) mussels. Contaminant elimination was not affected by size o r differences in lipid levels. For both lipid levels rand size classes of mussels, the BCFs were positively correlated with compound log oct anol:water partition coefficient. Hence, the lipid affinity of a compo und can be a good indicator of mussel contaminant accumulation Potenti ally large contaminant concentration in zebra mussels may alter contam inant cycling in the Great Lakes by increasing contaminant transfer to mussel predators. Selective predation on small, pre-spawning (high li pid) mussels may present a greater hazard to predators than predation on larger, post-spawning (low lipid) mussels.