Several general hypotheses will be tested. These include the assertion that zebra mussel will bioconcentrate or bioaccumulate PCBs and PAHs when exposed to contaminated media; that unassimilated material will be deposited into pseudofeces in significant levels; that benthos can accumulate significant levels of PVBs and PAHs by ingesting contaminated pseudofeces. Specific objectives are the following:
To determine kinetically the accumulation of 4 hydrophobic contaminants (benzo(a)pyrene, phenanthrene and 2 hexachlorobiphenyls) in adult zebra mussels;
To evaluate the relative rates of accumulation when the contaminants are sorbed directly from water vs when they are assimilated from phytoplankton or suspended sediment;
To determine the relative amounts of partitioning into feces and pseudofeces via the previously described modes of administration;
To measure the accumulation of PCBs and PAHs by the benthic contaminated feces/pseudofeces.

Although much attention has been focused on the potential for zebra mussel to act as biofouling agents and to disrupt phytoplankton distributions, little attention has been paid to its probable capacity to direct the disposition of toxic chemicals in the Great Lakes. We believe that this potential includes not only the ability to concentrate toxins from a variety of media (e.g. water, sediment and phytoplankton) but also to redistribute hydrophobic contaminants from the latter media to benthic foodchains via deposition in pseudofeces. Thus, a major impact zebra mussels on toxic materials could be to redirect toxins from the water column to the benthic environment. This propensity is accentuated by the tremendous filtering capacity of the animal and its proclivity for occupying environments which are likely to be contaminated. The zebra mussel thus represents a unique opportunity to examine the interplay between biota and the physical environment in determining the distribution of toxic materials in the Great Lakes. The proposed research will describe quantitatively the ability of the zebra mussel to accumulate hydrophobic contaminants from different media, the assimilation efficiency of 2 PCBs and 2 PAHs into the zebra mussel, the residues which remain in the pseudofeces and the ability of benthos to accumulate toxins from contaminated pseudofeces. The research will thus provide major insight towards understanding the impact of the zebra mussel in the Great Lakes.