Since their invasion into the Great Lakes, zebra mussels, Dreissena polymorpha, have increased the water clarity in Lake St. Clair and Lake Erie due to their extensive particle filtration. Because these particles contain sorbed contaminants, the potential for contaminant accumulation from both suspended sediment and algae were examined. Sediment or algae were dosed with selected radiolabeled polycyclic aromatic hydrocarbon congeners and/or hexachlorobiphenyl (HCBP). Assimilation efficiencies were measured and depended on food quality. Zebra mussels, 17 +/- 2 mm long, assimilated 58.3 +/- 13.5% of the pyrene and 44.7 +/- 5.8% of the benzo(a)pyrene (BaP) from sediment particles with a particle clearance rate of 493-897 ml/g tissue/h. However, assimilation efficiencies were 91.7 +/- 3.7% for pyrene, 91.9 +/- 1.4% for BaP, 96.6 +/- 1.4% for chrysene, and 97.7 +/- 0.5% for HCBP from suspended algae. Algal particle clearance rates for the mussels ranged from 47-143 ml/g tissue/h. Thus, zebra mussels efficiently accumulated non-polar contaminants sorbed to algae, while a smaller fraction of the sediment-associated contaminant was bioavailable. Furthermore, the contaminants sorbed onto suspended sediment particles were quickly removed from the water and deposited as pseudofeces. The pseudofeces production was positively correlated with filtration rate and suspended particle concentrations.