Mercury in Fishes from Yosemite (CA), Mount Rainier (WA), and Rocky Mountain (CO) National Parks: Potential Drivers and Ecological Risk

Colleen Flanagan Pritz1, Collin Eagles-Smith2, James Willacker3, Michelle Lutz4 and Michael Tate5

The National Park Service (NPS) safeguards over 400 special places for the protection of unique natural resources and scenic beauty. Although celebrated as some of the most pristine ecosystems, recent studies have documented the presence of mercury in fish from NPS units across the western United States, including Mount Rainier (MORA; WA), Rocky Mountain (ROMO; CO), and Yosemite (YOSE; CA) national parks. Even protected areas, such as national parks, are subjected to mercury contamination because it is delivered through atmospheric deposition, often after long-range transport. Approximately 1,200 fish (primarily Salmonidae) were sampled from 52 subalpine lakes and rivers between 2003–2012 in MORA, ROMO, and YOSE, and analyzed for total mercury concentrations. Preliminary results indicate that mercury concentrations in fish varied substantially among and within parks, suggesting that landscape factors may be particularly important determinants of mercury risk in the parks. Basin delineations and landscape models were utilized to determine significant drivers in fish mercury concentrations, such as atmospheric deposition and dissolved organic carbon (DOC). Although mercury concentrations in most fish were low, at some sites they exceeded health thresholds for potential impacts to fish, birds, wildlife, and humans. Ongoing studies aim to further characterize mercury in fish from eastern national parks, evaluate the utility of dragonfly larvae as a biosentinel for mercury in aquatic food webs, and assess mercury source attribution via mercury stable isotope markers. With a strong foundation in research, the NPS strives to understand how best to minimize air pollutants in park ecosystems, including airborne contaminants like mercury where concentrations in fish challenge the very mission of the national parks to leave resources and wildlife unimpaired for future generations. 


1National Park Service,