Spatial variation in aquatic invertebrate and riparian songbird mercury exposure across a river-reservoir system with a
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Spatial variation in aquatic invertebrate and riparian songbird mercury exposure across a river-reservoir system with a legacy of mercury contamination Allyson K. Jackson
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Collin A. Eagles-Smith3 Colleen Emery3 ●
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Accepted: 8 April 2019 © Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract Mercury (Hg) loading and methylation in aquatic systems causes a variety of deleterious effects for fish and wildlife populations. Relatively little research has focused on Hg movement into riparian food webs and how this is modulated by habitat characteristics. This study characterized differences in Hg exposure in aquatic invertebrates and riparian songbirds across a large portion of the Willamette River system in western Oregon, starting at a Hg-contaminated Superfund site in the headwaters (Black Butte Hg Mine) and including a reservoir known to methylate Hg (Cottage Grove Reservoir), all downstream reaches (Coast Fork and Willamette River) and off-channel wetland complexes (Willamette Valley National Wildlife Refuge Complex). After accounting for year, date, and site differences in a mixed effects model, MeHg concentrations in aquatic invertebrates varied spatially among habitat categories and invertebrate orders. Similarly, THg in songbird blood varied by among habitat categories and bird species. The highest Hg concentrations occurred near the Hg mine, but Hg did not decline linearly with distance from the source of contamination. Birds were consistently elevated in Hg in habitats commonly associated with enhanced MeHg production, such as backwater or wetlands. We found a positive but weak correlation between aquatic invertebrate MeHg concentrations and songbird THg concentrations on a site-specific basis. Our findings suggest that Hg risk to riparian songbirds can extend beyond point-source contaminated areas, highlighting the importance of assessing exposure in surrounding habitats where methylmercury production may be elevated, such as reservoirs and wetlands. Keywords Methylmercury Willamette Black Butte Songbird Aquatic invertebrate ●
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Introduction Human development, changes in land use, and other anthropogenic alterations have substantially changed
Supplementary information The online version of this article (https:// doi.org/10.1007/s10646-019-02043-z) contains supplementary material, which is available to authorized users. * Allyson K. Jackson [email protected] 1
Department of Environmental Studies, Purchase College SUNY, 735 Anderson Hill Road, Purchase, NY 10577, USA
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Department of Fisheries and Wildlife, Oregon State University, 104 Nash Hall, Corvallis, OR 97331, USA
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U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, 3200 SW Jefferson Way, Corvallis, OR 97331, USA
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natural biogeochemical cycles, biodiversity, and ecological interactions (Vitousek 1997). One of the most widespread alterations has been the appropriation of freshwater for various human needs (Eagles-Smith et al. 2018). Most freshwater e
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