A novel nonequilibrium, steady-state model is presented to predict the bioaccumulation of organic chemicals by filter feeding and detritivorous benthic invertebrates. This model accounts for chemical disequilibria between overlying water, diet and sediment, biomagnification, and benthic invertebrate feeding preferences and strategies. The results of a field study of PCB congener bioaccumulation in various benthic invertebrate species in western Lake Erie are reported to verify the model. A comparison of model-predicted and field data demonstrate that the predictability of this model is better than that of the widely used equilibrium partitioning model for as sessing bioaccumulation in benthic organisms and for developing sediment quality criteria.

The denominator of eq 13 should read as follows:The diet of emerald shiner should contain 93%, 1%, 2%, and 4% of zooplankton, caddisfly larvae, Hexagenia limbata, and Gammarus, respectively. The diet of walleye should contain 10% zooplankton rather than 10% phytoplankton.These errors were typos and do not affect the results presented in the paper. The authors thank Theo Traas (RIVM) for bringing the error in eq 13 to their attention.

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A mathematical model is described that estimates chemical concentrations in phytoplankton, zooplankton, filter-feeding and detritovorous benthic invertebrates, and fish. Chemical concentrations are determined at steady-state using conventional chemical, biological, and environmental data. Concentration data for 31 PCB congeners in 14 different fish species, five benthic invertebrate species, water and sediment collected from western Lake Erie, and corresponding feeding preference data were used to verify the model. The results illustrate that 95% of the observed concentrations in filter-feeding benthic invertebrates, detritous feeding benthic invertebrates, and fish were within a factor of 1.8, 1.9, and 2.0 of the model-predicted concentrations, respectively. The ability of this model to predict contaminant transfer in a complex food web and its potential applicability to other food webs indicate that it could be an important tool for managing contaminants on an ecosystem level.

The bivalve mollusc Dreissena polymorpha colonized Lake St. Clair in 1986 as a result of ballast water discharge. The present study shows that since initiating reproduction in 1988, its population density at all of the sites originally colonized has increased more than a 1000-fold. The species has, as well, expanded its range in Lake St. Clair dramatically. The density and range increase is not yet complete, as populations at most sites remain dominated by juveniles. Densities in excess of 5000 individuals/m2 seem likely to be achieved at most sites in Lake St. Clair within 5 years. It appears likely that D. polymorpha will have a significant impact on composition of the benthos. Shells of individual unionids carry in excess of 10 000 D. polymorpha, and lipid reserves of such unionids are only half those of unaffected individuals. Aside from direct interactions with benthic organisms, the filtering activity of D. polymorpha populations may be sufficient to result in a significant impact on the turbidity of water exiting Lake St. Clair.

The elimination rate constants (k(2)) of nine polycyclic aromatic hydrocarbons (PAHs) were examined for the freshwater mussel Elliptio complanata. The concentrations of fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[ a]anthracene, chrysene, benzo[ b]fluoranthene, and indeno[1,2,3-c,d]pyrene revealed a significant inverse relationship with time and their k(2) values ranged from 0.10 to 0.22 day(-1). The k(2) values of these significantly cleared PAHs were similar to k(2) values observed for nonmetabolized organochlorines in mussels previously reported in the literature. The inverse relationship between k(2) and K(ow) provides evidence that the nine PAHs were being passively eliminated from the mussels and that they can be used to calibrate the mussel as a quantitative biomonitor. A general expression relating elimination rate constants and chemical K(ow) is derived for hydrophobic contaminants in E. complanata. The k(2) versus log K(ow) regression equation for mussels developed herein was similar to other studies documenting the elimination of PCBs and PAHs in a number of bivalve species.

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A food web bioaccumulation model was used to hindcast PCB congener concentrations in aquatic biota from western Lake Erie in the years prior to the zebra mussel invasion, and these results were compared to post-mussel predicted concentrations that had been verified previously against measured data to estimate the effects of mussels on the trophodynamics of PCB congeners in western Lake Erie. Two hindcasting scenarios were compared to a third, previously verified, scenario to determine the changes in PCB congener concentrations in biota in response to (i) modifications to food web structure, before and after the introduction of mussels, and (ii) modifications to food web structure combined with a decline in particulate organic carbon (POC) concentrations resulting from removal of seston from the water column by mussel filtering activities. The reduction in the concentration of POC, attributed to the prodigious filter-feeding of large zebra mussel populations, was predicted to have caused increases in the freely dissolved concentrations of PCB congeners ranging from 2.9% to 9.3%. These increases in dissolved chemical were predicted by the model to cause small increases (range 0-7.3%) in the PCB congener burdens of many biota including zooplankton, prey fish species, and walleye. Other organisms, such as Gammarus, small white suckers, and freshwater drum, were predicted to have larger increases in their PCB body burdens (9.1-22.2%) as a result of the increase in freely dissolved chemical and a shift in diet. For crayfish, yellow perch, black crappie, white perch, large white suckers, gizzard shad, and largemouth bass, the increased exposure to chemical via water was offset by decreased chemical exposure via the diet, which resulted from shifts in diet toward less contaminated items brought about by the presense of zebra mussels. The results of this study are relevant to Lake Erie resource managers that are concerned about the potential of zebra mussels to alter PCB congener dynamics in the western basin.