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The Willamette River basin in western Oregon is a system with legacy mercury contamination from both mining and reservoirs

To examine methylmercury exposure in songbirds and aquatic invertebrates in different habitats in the basin, researchers sampled at a mercury-contaminated Superfund site in the headwaters (Black Butte Mercury Mine), a reservoir known to methylate mercury (Cottage Grove Reservoir), and downstream reaches of the Coast Fork and Willamette River. Methylmercury concentrations in both aquatic invertebrates and songbirds varied among habitat type and species. The highest mercury concentrations occurred near the mine, but mercury did not decline linearly with distance from the contamination source. Birds had high mercury levels in habitats commonly associated with enhanced methylmercury production, such as backwater or wetlands. Findings suggest that mercury 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.

Jackson, A.K., Eagles-Smith, C.A., Emery, C.S., 2019, Spatial variation in aquatic invertebrate and riparian songbird mercury exposure across a river-reservoir system with a legacy of mercury contamination: Ecotoxicology,  

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