Mercury (Hg) is a globally distributed pollutant that poses a great risk to humans and wildlife health, affecting reproduction and overall fitness. Because Hg moves globally through the atmosphere across state and national boundaries, even protected habitats like the US National Parks are not immune from Hg pollution. Under appropriate conditions in wetland areas, inorganic Hg is microbially converted to methylmercury (MeHg). This highly toxic organic form allows for bioaccumulation and magnification through the food web, including aquatic and terrestrial wildlife. We focused this study on riparian songbirds in five National Parks across the continental United States: Acadia (n = 59), Grand Teton (n = 65), Mount Rainer (n = 24), Olympic (n = 151), and Yosemite (n = 68).
Results/Conclusions
Whole blood total Hg (THg) concentrations ranged from 0.006- 1.441 µg/g wet weight. Coastal Parks, that were also generally wet regions, such as Olympic (within 80 km of the ocean, mean =0.2507), Acadia (within 2 km, mean = 0.2609), and Mount Rainer National Parks (within 190 km, mean =0.1628), experience higher THg levels in their songbird populations than areas that are more inland (>300km from an ocean) and arid, such as Yosemite (mean = 0.1105) and Grand Teton National Parks (mean = 0.0852). Across all parks, species that rely more heavily on insect prey during the breeding season generally presented higher THg concentrations. This study can be used as a baseline to understand Hg exposure from non-point source pollution across the United States.