You are here:
The historical reconstruction of energy pathways and contaminant accumulation in Lake Trout between two contrasting Great Lakes: Superior and Michigan
Citation:
Lepak, R., J. Hoffman, S. Jannsen, M. Gordon, M. Tate, J. Ogorek, D. Krabbenhoft, E. Murphy, J. Hurley, AND A. Cotter. The historical reconstruction of energy pathways and contaminant accumulation in Lake Trout between two contrasting Great Lakes: Superior and Michigan. Presented at SETAC North America, Fort Worth, TX, November 15 - 19, 2020. https://doi.org/10.23645/epacomptox.13235021
Impact/Purpose:
Elevated mercury in fish poses risks to fish-consuming wildlife and humans. Regionally, mercury emissions have been declining yet temporal reconstruction of lake trout mercury concentrations reveal that Lakes Michigan and Superior have not responded in unison. This is because the energy pathways to lake trout have not remained constant through time and the fluctuations in diet due to invasive species and niche partitioning has impacts fish mercury concentrations. However the historical data necessary to demonstrate these fluctuations is lacking and thus alternative methods to trace fish diets must be employed. Here we measure carbon and nitrogen stable isotope ratios in bulk fish tissue and amino acids of a well-preserved fish archive to reconstruct dietary preferences of lake trout since 1982. Aided with this data, we can then better interpreting mercury concentration trends. Results also show methylmercury concentrations in fish are sensitive to changes in trophic structure and diet driven by invasive species
Description:
Evaluation of contaminant load reductions to the Great Lakes have typically relied on sediment core reconstructions and long-term biological monitoring and specimen archiving. These two retrospective approaches can reveal differing narratives about the success of reducing contaminant loading to the Great Lakes. Interpreting contaminant trends in fish through time is particularly challenging because they are mobile, express individuality in resource use (niche partitioning) and are highly sensitive to physical, ecological, and biological changes yet contaminant reductions in fish are a prized marker of success in resource management. In addition, fish-reconstruction efforts are often limited by supporting evidence, sample availability and typical archival approaches (ex. museum curation) which tend to blur the inferential power new analytical tools can provide. Here we present bulk and compound-specific stable carbon and nitrogen isotope ratios in amino acids in two frozen lake trout archives (1982 – present) from Lakes Superior and Michigan to evaluate the impact biological and ecological changes have on energetic pathways and contaminant concentrations in fish. We explore how aquatic invasive species (ex. dreissenid mussels – Lake Michigan) and polymorphism (Lake Superior) impact lake trout and thus changed diet (resource use), growth and mercury (Hg) concentrations. Once the energetic differences are accounted for, we can then compare Hg trends in lake trout to decreasing Hg emission trends in North America to answer the following questions: are fish responding to declining Hg emissions/loading; what are the sources for ecological variability in Hg concentrations; does considering energetic differences lead to improved source-receptor understanding; and, what actions should be taken in the future to improve continued sampling?
URLs/Downloads:
DOI: The historical reconstruction of energy pathways and contaminant accumulation in Lake Trout between two contrasting Great Lakes: Superior and Michigan