Elevated mercury levels have been detected in fish at national parks throughout the West, including Rocky Mountain National Park.
The mercury, found in habitats located in some of the most remote areas in the region, exceeds U.S. Environmental Protection Agency health thresholds for potential impacts to fish, birds and humans in some cases. The information came after scientists with the U.S. Geological Service and National Park Service analyzed both popular sport fish and smaller prey fish in 21 national parks across 10 western states. According to their recently published report, mercury concentrations were generally low, but they still found some individual fish with mercury levels exceeding the EPA’s human health criterion in Colorado, California, Washington and Wyoming.
“This is a wake-up call,” NPS ecologist Colleen Flanagan Pritz, a co-author of the study, said in a press release. “We need to see fewer contaminants in park ecosystems, especially contaminants like mercury where concentrations in fish challenge the very mission of the national parks to leave wildlife unimpaired for future generations.”
The study collected 1,400 fish from 86 rivers and lakes between 2008 and 2012. It included both sport fish and smaller prey fish consumed by birds and wildlife. Of the fish studied, 95 percent of detected mercury was in the form of methylmercury, the most harmful to human and wildlife health. The contaminant is among the most widespread in the world. It can be distributed naturally through volcanic eruptions or through human sources, like coal-burning power plants. According to the study, human activities have caused atmospheric mercury levels to jump by as much as five times in the past 150 years.
In Rocky Mountain National Park, the study collected fish samples of brook trout, brown trout, cutthroat trout and rainbow trout as well as suckers in 19 lakes and streams. Six sites were located on the west side of the Park. Mirror Lake on the east side had the highest mean levels of mercury, at 121.2 nanograms per gram wet weight, or ng/g ww. The Colorado River was at a close second, with a mean level of 118.0 ng/g ww. The EPA criterion for human health is 300 ng/g ww; however, the Great Lakes Advisory Group has set a criterion of 50 ng/g ww for unlimited consumption by humans. According to the study, the benchmark risk for highly sensitive birds is 90 ng/g ww.
Both the Centers of Disease Control and Prevention and World Health Organization report serious health risk from human exposure to mercury, including toxic effects on the nervous, digestive and immune systems. Mercury exposure also carries serious health risks for developing fetuses. According to the National Wildlife Federation and EPA, high mercury concentrations in fish, birds and wildlife cause difficulty in reproduction and finding food.
“Although fish mercury concentrations were elevated in some sites, the majority of fish across the region had concentrations that were below most benchmarks associated with impaired health of fish, wildfire and humans,” said the study’s lead author, Collin Eagles-Smith of the U.S. Geological survey, in the press release. “However, the range of concentrations measured suggest that complex processes are involved in driving mercury accumulation in these environments and further research is needed to better understand these processes and assess risk.”
To read the full study, visit pubs.usgus.gov/of/2014/1051/.
Leia Larsen can be reached at 970-887-3334.