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Broad-scale assessment of methylmercury in adult amphibians

October 30, 2023

Mercury (Hg) is a toxic contaminant that has been mobilized and distributed worldwide and is a threat to many wildlife species. Amphibians are facing unprecedented global declines due to many threats including contaminants. While the biphasic life history of many amphibians creates a potential nexus for methylmercury (MeHg) exposure in aquatic habitats and subsequent health effects, the broad-scale distribution of MeHg exposure in amphibians remains unknown. We used nonlethal sampling to assess MeHg bioaccumulation in 3,241 juvenile and adult amphibians during 2017–2021. We sampled 26 populations (14 species) across 11 states in the United States, including several imperiled species that could not have been sampled by traditional lethal methods. We examined whether life history traits of species and whether the concentration of total mercury in sediment or dragonflies could be used as indicators of MeHg bioaccumulation in amphibians. Methylmercury contamination was widespread, with a 33-fold difference in concentrations across sites. Variation among years and clustered subsites was less than variation across sites. Life history characteristics such as size, sex, and whether the amphibian was a frog, toad, newt, or other salamander were the factors most strongly associated with bioaccumulation. Total Hg in dragonflies was a reliable indicator of bioaccumulation of MeHg in amphibians (R2 ≥ 0.67), whereas total Hg in sediment was not (R2 ≤ 0.04). Our study, the largest broad-scale assessment of MeHg bioaccumulation in amphibians, highlights methodological advances that allow for nonlethal sampling of rare species and reveals immense variation among species, life histories, and sites. Our findings can help identify sensitive populations and provide environmentally relevant concentrations for future studies to better quantify the potential threats of MeHg to amphibians.

Publication Year 2023
Title Broad-scale assessment of methylmercury in adult amphibians
DOI 10.1021/acs.est.3c05549
Authors Brian J. Tornabene, Blake R. Hossack, Brian J. Halstead, Collin Eagles-Smith, Michael J. Adams, Adam R. Backlin, Adrianne Brand, Colleen Emery, Robert N. Fisher, Jillian Elizabeth Fleming, Brad Glorioso, Daniel A. Grear, Evan H. Campbell Grant, Patrick M. Kleeman, David Miller, Erin L. Muths, Christopher Pearl, Jennifer Rowe, Caitlin Teresa Rumrill, J. Hardin Waddle, Megan Winzeler, Kelly L. Smalling
Publication Type Article
Publication Subtype Journal Article
Series Title Environmental Science and Technology
Index ID 70249807
Record Source USGS Publications Warehouse
USGS Organization Forest and Rangeland Ecosys Science Center; Fort Collins Science Center; National Wildlife Health Center; New Jersey Water Science Center; Northern Rocky Mountain Science Center; Western Ecological Research Center; Wetland and Aquatic Research Center; Eastern Ecological Science Center