title: Mercury in streams at Grand Portage National Monument (Minnesota, USA): assessment of ecosystem sensitivity and ecological risk.
abstract: Mercury (Hg) in water, sediment, soils, seston, and biota were quantified for three streams in the Grand Portage National Monument (GRPO) in far northeastern Minnesota to assess ecosystem contamination and the potential for harmful exposure of piscivorous fish, wildlife, and humans to methylmercury (MeHg). Concentrations of total Hg in water, sediment, and soil were typical of those in forest ecosystems within the region, whereas MeHg concentrations and percent MeHg in these ecosystem components were markedly higher than values reported elsewhere in the western Great Lakes Region. Soils and sediment were Hg-enriched, containing approximately 4-fold more total Hg per unit of organic matter. We hypothesized that localized Hg enrichment was due in part to anthropogenic pollution associated with historic fur-trading activity. Bottom-up forcing of bioaccumulation was evidenced by MeHg concentrations in larval dragonflies, which were near the maxima for dragonflies sampled concurrently from five other national park units in the region. Despite its semi-remote location, GRPO is a Hg-sensitive landscape in which MeHg is produced and bioaccumulated in aquatic food webs to concentrations that pose ecological risks to MeHg-sensitive piscivores, including predatory fish, belted kingfisher, and mink.
authors: University of Wisconsin-La Crosse, River Studies Center, 1725 State Street, La Crosse, WI 54601, USA. Electronic address: krolfhus@uwlax.edu.
authors: Kristofer R
authors: KR
authors: Rolfhus
authors: University of Wisconsin-La Crosse, River Studies Center, 1725 State Street, La Crosse, WI 54601, USA. Electronic address: jwiener@uwlax.edu.
authors: James G
authors: JG
authors: Wiener
authors: University of Wisconsin-La Crosse, River Studies Center, 1725 State Street, La Crosse, WI 54601, USA. Electronic address: rharo@uwlax.edu.
authors: Roger J
authors: RJ
authors: Haro
authors: University of Wisconsin-La Crosse, River Studies Center, 1725 State Street, La Crosse, WI 54601, USA. Electronic address: msandheinrich@uwlax.edu.
authors: Mark B
authors: MB
authors: Sandheinrich
authors: University of Wisconsin-La Crosse, River Studies Center, 1725 State Street, La Crosse, WI 54601, USA. Electronic address: sbailey@uwlax.edu.
authors: Sean W
authors: SW
authors: Bailey
authors: National Park Service, Grand Portage National Monument, P.O. Box 426, 170 Mile Creek Road, Grand Portage, MN 55605, USA. Electronic address: brandon_seitz@nps.gov.
authors: Brandon R
authors: BR
authors: Seitz
mesh_terms: D000818:Animals; D017753:Ecosystem; D004784:Environmental Monitoring; D005399:Fishes; D020387:Food Chain; D007313:Insecta / Q000737:chemistry; D008628:Mercury / Q000032:analysis*; D008910:Minnesota; D018570:Risk Assessment; D045483:Rivers / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D008628:Mercury
keywords: Aquatic food web; Bioaccumulation; Contaminant; Exposure; Methylmercury