Identification of the determinants of fish tissue mercury concentrations in temperate lakes: Factors to be considered in the establishment or revision of fish consumption advisories

The Need
Mercury (Hg) is number two on the Agency for Toxic Substances and Disease Registry’s (ATSDR) priority pollutant list and a global contaminant of major concern because exposure to this neurotoxin poses risk to human and wildlife health. The threat of this toxin to human health has resulted in the establishment of consumption advisories of marine and freshwater fish in 44 states in the U.S. and all of the eastern Canadian provinces. Maine is one of only two states with a blanket fish consumption advisory for all inland waters. Given the policy’s economic and social costs, the Maine Department of Environmental Protection (DEP) is interested in supporting scientific research to better understand mercury dynamic  in watersheds, which would allow consideration of alternative approaches.

Program Overview & Objectives
We have analyzed the existing DEP and UMaine lake databases for Hg and other physical, chemical, and biological parameters that control fish Hg bioaccumulation, with a goal to identify mechanistic relationships, formulate testable hypotheses, and prioritize future empirical and statistical analyses that will be used as a basis for revising the current fish advisory. Our statistical analysis to date shows that a) trophic status, b) dissolved organic carbon (DOC) concentration, and c) lake depth explain most of variability in fish Hg concentration in lakes across Maine. However, there are gaps in the existing data and, thus, there is a need to collect more data to better explain the observed variability in fish Hg concentration in Maine lakes. We propose to analyze relevant parameters in fish, sediment, and water column from 100 targeted lakes that cover a wide continuum of conditions within each of the above three indicators. Analysis of data from these lakes will allow us to rigorously assess the factors that control fish Hg bioaccumulation in Maine lakes, and likely other regions, and formulate a scientific basis for the refinement of fish consumption advisories to exempt lakes where Hg is unlikely to bioaccumulate. Assessment of new data is expected to lead to the development of a quantitative process-oriented model that accounts for a significant portion of variation in fish tissue Hg concentrations in Maine lakes. Results of model testing are likely to lead to fish consumption advisory refinements that will have significant social and economic impacts. The objectives of this project are as follows:

• Test that variation on fish tissue Hg concentrations among lakes may be explained by parameters that control lake trophic status;
• Test that lake trophic status is related to sediment geochemistry, and that the latter is a good predictor of fish tissue Hg concentrations;
• Test that lake DOC concentration, size, and other factors that control

Contact Information
Aria Amirbahman
Civil & Environmental Engineering
319A Boardman Hall
University of Maine
Orono, ME 04469

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