Ecological factors regulating chemical bioaccumulation and fish consumption advisories

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Fish consumption advisories place economic constraints on fishing activities and generate a high degree of public concern about environmental health risks and sustainability of aquatic resources. Methyl-mercury (MeHg) and polychlorinated biphenyls (PCBs) are responsible for most of the fish consumption advice issued in North America even though both contaminants have been subject to bans in their production (PCBs) or major restrictions in commercial uses and loadings to the environment. These pollutants exhibit differences in their physical properties, environmental fate and mechanisms of bioaccumulation yet have a common property of undergoing food web biomagnification and generate among the highest trophic magnification factors (TMFs) observed for any environmental contaminants in aquatic ecosystems. Yet, even at the scale of ecosystems, MeHg and PCBs show differences in their behavior when present in the same environment suggesting that each chemical responds to common sets of ecological processes in different ways. MeHg and PCBs have each been used as fish bioenergetic tracers but have never been attempted to be co-interpreted as independent ecological tracers. In this proposal I will generate and calibrate a common bioaccumulation model that can be applied to MeHg and PCBs to predict how each tracer responds to sets of ecosystem stressors. Studies in Research Theme 1 will focus on uncovering differences in chemical toxicokinetics in fish under combinations of diet and temperature treatments to predict how each tracer will respond to alterations in food web structure and environmental conditions. The second research theme will focus on changes in specific growth rates of fish and how changes in compartment size of protein and lipid pools regulate chemical concentrations and generate individual variation in bioaccumulated residues. The third theme will integrate results of theme 1 and 2 to develop and validate a stochastic, non-steady state food web bioaccumulation model applicable to MeHg and PCBs. The model will be used to forecast fish consumption advisories in the Great Lakes food webs under hypothetical sets of environmental stressors. The proposed research will train 10 HQP at the undergraduate and graduate levels exposing them to experimental approaches using laboratory and mesocosm experiments, field sampling, advanced analytical chemistry and environmental modelling techniques, all skills that are in strong demand in government and industry.**