To understand the impact reduced mercury (Hg) loading and invasive species have had on methylmercury bioaccumulation in predator fish of Lake Michigan, we reconstructed bioaccumulation trends from a fish archive (1978 to 2012). By measuring fish Hg stable isotope ratios, we related temporal changes in Hg concentrations to varying Hg sources. Additionally, dietary tracers were necessary to identify food web influences. Through combined Hg, C, and N stable isotopic analyses, we were able to differentiate between a shift in Hg sources to fish and periods when energetic transitions (from dreissenid mussels) led to the assimilation of contrasting Hg pools (2000 to present). In the late 1980s, lake trout δ202Hg increased (0.4) from regulatory reductions in regional Hg emissions. After 2000, C and N isotopes ratios revealed altered food web pathways, resulting in a benthic energetic shift and changes to Hg bioaccumulation. Continued increases in δ202Hg indicate fish are responding to several United States mercury emission mitigation strategies that were initiated circa 1990 and continued through the 2011 promulgation of the Mercury and Air Toxics Standards rule. Unlike archives of sediments, this fish archive tracks Hg sources susceptible to bioaccumulation in Great Lakes fisheries. Analysis reveals that trends in fish Hg concentrations can be substantially affected by shifts in trophic structure and dietary preferences initiated by invasive species in the Great Lakes. This does not diminish the benefits of declining emissions over this period, as fish Hg concentrations would have been higher without these actions.
|Original language||English (US)|
|Number of pages||9|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Jan 1 2019|
Bibliographical noteFunding Information:
aEnvironmental Chemistry and Technology Program, University of Wisconsin–Madison, Madison, WI 53706; bUS Geological Survey, Upper Midwest Water Science Center, USGS Mercury Research Laboratory, Middleton, WI 53562; cUS Environmental Protection Agency (US EPA) Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, Duluth, MN 55804; dState Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guanshanhu District, 550081 Guiyang, Guizhou, China; eGreat Lakes National Program Office, US EPA, Chicago, IL 60604; fSt. Croix Watershed Research Station, Science Museum of Minnesota, Marine on St. Croix, MN 55047; gDepartment of Civil and Environmental Engineering, University of Wisconsin–Madison, Madison, WI 53706; and hUniversity of Wisconsin Aquatic Sciences Center, Madison, WI 53706
ACKNOWLEDGMENTS. This work was supported by the US EPA Great Lakes Restoration Initiative (Project GL-00E01139), the US Geological Survey (USGS) Toxic Substances Hydrology Program, and the US EPA Great Lakes Fish Monitoring and Surveillance Program (Elizabeth Murphy, Program Manager). Partial graduate student support was provided by the Wisconsin Alumni Research Foundation through the University of Wisconsin–Madison Graduate School (Award MSN165161) and the University of Wisconsin Water Resources Institute through a USGS-National Institutes for Water Resources fellowship (Award MSN197848). Lake Michigan sediment core collection was coordinated by Mark Edlund (St. Croix Watershed Research Station) and was supported by the Great Lakes Fishery Trust (Project 2008.960) and
the National Park Service and US EPA (Great Lakes Restoration Initiative Project #91). Ship support was provided by the University of Michigan/ National Oceanic and Atmospheric Administration R/V Laurentian and the US EPA R/V Lake Guardian. The views expressed in this paper are solely
- Lake Michigan
PubMed: MeSH publication types
- Journal Article
- Research Support, Non-U.S. Gov't
- Research Support, U.S. Gov't, Non-P.H.S.