Direct and indirect effects of metal pollutants on lotic food webs: comparative sensitivities of warmwater and coldwater forage fish

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Protection of our waters depends upon our ability to understand ecosystem complexity enough to attain a level of confidence in predictive relationships between a pollutant and the response of exposed organisms. Due to the complexities of aquatic ecosystems, our understanding of how pollutants (e.g., metals and metal mixtures) affect lotic (river) food webs is limited. Extrapolation of our results from warm water to coldwater fishes is also very limited. The long term objectives of the proposed research are to better understand direct and indirect effects of pollutants including metals on lotic food webs and comparative sensitivities among species of fish. We will use selenium as our model pollutant. Se is an essential micronutrient that is both beneficial and toxic within a narrow concentration range. Mining, irrigation of agricultural land, petroleum refining and coal combustion can increase Se in aquatic ecosystems. Direct (waterborne exposure) and indirect (dietary exposure) effects of Se on the partial lifecycles of warm water (fathead minnow) and cold water (slimy sculpin) forage fishes and the lifecycle of a dominant prey item (midge) will be investigated using simple food webs (algae, invertebrate, fish). A partial lifecycle reproductive bioassay will be developed for slimy sculpin. Sensitivities of fathead minnow and slimy sculpin to Se will be assessed under different temperature regimes and when these fish are interacting in the same self-sustaining four-level food web (algae, invertebrate, slimy sculpin, fathead minnow). This research will better our understanding of how river food webs are affected by Se and the different sensitivities of cold and warm water fishes. Understanding biological responses for single metals will assist our understanding of responses to complex mixtures (e.g., metal mine effluents).