Bioaccumulative contaminants in aquatic food webs in six national park units of the western Great Lakes region: 2008–2012

Wiener, James; Haro, Roger; Rolfhus, Kristofer; Sandheinrich, Mark; Bailey, Sean; Northwick, Reid

We report results of an intensive assessment of selected bioaccumulative contaminants in aquatic food webs and ecosystems in six national park units within the Great Lakes Inventory and Monitoring Network. The park units included in our study were Grand Portage National Monument (GRPO), Indiana Dunes National Lakeshore (INDU), Isle Royale National Park (ISRO), Pictured Rocks National Lakeshore (PIRO), Sleeping Bear Dunes National Lakeshore (SLBE), and Voyageurs National Park (VOYA). The principal objectives of this project were (1) to assess spatial patterns in contamination of aquatic ecosystems and biota in the six park units, (2) to identify park units and water bodies where bioaccumulative contaminants may pose a risk to organisms—particularly piscivores atop aquatic food webs, and (3) to provide data for assessing temporal trends in contamination of fish and aquatic food webs in parks of the Great Lakes Network. The contaminants analyzed were total mercury, methylmercury, total lead, the insecticide DDT and its metabolites DDE and DDD, polychlorinated biphenyls (PCBs, 72 congeners), perfluorochemicals (PFCs, nine analytes), and polybrominated diphenyl ethers (PBDEs, 9 to 17 congeners). A total of 23 water bodies were studied, including three streams at GRPO, three sites at INDU (Great Marsh, Long Lake and Middle Lagoon), four lakes at ISRO, five lakes at PIRO, four lakes at SLBE, and four lakes at VOYA. This study followed a pilot study that quantified bioaccumulative contaminants in adult predatory fish, prey fish, and larval dragonflies sampled in 2008–2009 from the six park units (Wiener et al. 2013). Subsequent funding from the Great Lakes Restoration Initiative was used to expand the sampling and analyses of mercury in the six park units during 2010–2012 to include water, surficial sediment, soil, seston, and zooplankton, and to continue sampling and analyses of larval dragonflies, prey fish, and adult predatory fish. Adult predatory fish were also analyzed for selected bioaccumulative organic contaminants (DDT, PCBs, PBDEs, PFCs) and total lead; for these analytes, we analyzed axial muscle tissue from fish collected during 2008–2009 and whole-body samples from fish collected during 2010–2012. The accumulation of mercury (as methylmercury) in aquatic food webs and fish varied greatly among the 23 water bodies studied, both within and among the six park units. Moreover, fish in some park units have bioaccumulated mercury to toxicologically significant levels. Mercury concentrations in axial muscle tissue (skinless fillets) of adult predatory fish from several water bodies substantially exceeded 300 ng/g (parts per billion) wet weight, the U.S. Environmental Protection Agency (USEPA) tissue residue criterion for methylmercury, which was established to protect the health of humans who eat noncommercial fish. Concentrations of mercury in axial fillets of one or more individual predatory fish from five park units—including fish from four lakes at VOYA, four lakes at PIRO, four lakes at ISRO, and four lakes at SLBE—exceeded the USEPA tissue residue criterion. None of the individual fish from streams at GRPO and only one fish from INDU exceeded the USEPA tissue residue criterion. Mean concentrations of mercury in axial fillets of predatory fish exceeded the USEPA criterion in four lakes at VOYA, three lakes at PIRO, two lakes at ISRO, and two lakes at SLBE.

Bioaccumulative contaminants in aquatic food webs in six national park units of the western Great Lakes region: 2008–2012

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