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 levels of hydrophobic contaminants in its tissue. To better understand zebra mussel bioconcentration and ultimately, contaminant cycling, we measured bioconcentration factors (BCFs) and kinetic parameters for accumulation of polychlorinated biphenyl and polycyclic aromatic hydrocarbon congeners for two size classes of mussels and for a pre-spawning (high 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 kinetics determined for the less hydrophobic compounds, i.e., tetrachlorobiphenyl 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 shell length) mussels. Contaminant elimination was not affected by size or differences in lipid levels. For both lipid levels rand size classes of mussels, the BCFs were positively correlated with compound log octanol:water partition coefficient. Hence, the lipid affinity of a compound can be a good indicator of mussel contaminant accumulation Potentially large contaminant concentration in zebra mussels may alter contaminant cycling in the Great Lakes by increasing contaminant transfer to mussel predators. Selective predation on small, pre-spawning (high lipid) mussels may present a greater hazard to predators than predation on larger, post-spawning (low lipid) mussels.