Mercury Levels in Carson River’s Wood Ducks Raise Environmental Concerns
Researchers at the University of Nevada, Reno have highlighted a pressing environmental issue with their latest study, which reveals high mercury concentrations in wood ducks inhabiting the Carson River area. This region lies downstream of the historic Comstock Lode in Nevada, a site known for its mining activities in the 1800s.
During the gold and silver rush of the 19th century, miners employed mercury to extract precious metals from crushed ore. The residual mercury subsequently found its way into nearby waterways, embedding itself in the sediment along riverbanks and floodplains.
Over a span of 15 years, scientists gathered and analyzed feather samples from wood ducks residing along the Carson River. The data revealed alarming mercury levels in some ducklings, surpassing the federal safety standards for human consumption.
Co-author Perry Williams explained the pervasive nature of mercury contamination, stating, “Mercury is not just in the water or in the banks. It’s continuously being taken up by the invertebrates and the fish and the things that eat the fish, and everything in the food web. And we’re part of that food web as well.”
This issue is compounded by the conversion of mercury into methylmercury, a more toxic variant that accumulates in living organisms, increasing in concentration up the food chain.
Another critical finding of the study is the impact of wet years. Heavy snowfall and robust spring runoff can disturb river sediments, liberating mercury that had been dormant during drier periods. Mae Gustin, another co-author, noted that high water flows can elevate wildlife exposure: “Mercury forms in the banks, and then when you have high flows, it gets washed out into the river so the ducks are exposed to it.”
Despite these findings, Nevada lacks a statewide advisory regarding the consumption of wild waterfowl, even though certain ducklings have mercury concentrations exceeding federal guidelines.
Although the research primarily focuses on the Carson River watershed, its implications are broader. Historic mining activities have affected watersheds throughout the Mountain West, including in Colorado, Idaho, and Montana. Many of these rivers still bear the legacy of contamination from past mining operations.
With climate change potentially causing more extreme fluctuations between drought and heavy runoff, similar environmental patterns might appear in other regions.
This report is a product of the Mountain West News Bureau, a collaboration among several public media organizations including KUNR, Wyoming Public Media, and others, with funding from the Corporation for Public Broadcasting and Eric and Wendy Schmidt.
