University of North Texas

UNT Insider | January 2012 issue | UNT biologist part of team studying mercury contamination in Texas

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UNT biologist part of team studying mercury contamination in Texas

From a UNT News Service press release

Aaron Roberts

Aaron Roberts

Aaron Roberts, assistant professor of biological sciences, is working with both Ray Drenner and Matt Chumchal of Texas Christian University to study the implications of mercury contamination on fish and other organisms.

Three recent studies by the research team indicate that the southern United States may have a mercury pollution problem that has been underappreciated. Their research has important implications for humans and animals that consume fish and important fishery resources.

Their research is based on Drenner and Chumchal's discovery of a 64,000-square-kilometer area in eastern Texas with high concentrations of toxic mercury. They discovered the contaminated area, which is roughly the size of West Virginia, by sampling fish in the region and analyzing data collected during previous studies. They are both ecologists who specialize in studying the trophic transfer and biogeochemistry of mercury in the region.

Roberts, a mechanistic toxicologist who studies the health impacts of a wide array of contaminants, including mercury, joined the team for a focused study of Caddo Lake, located within the contaminated area of East Texas. Caddo Lake is one of the most beloved lakes in the state and is renowned for its diversity of fish and wildlife. Roberts and his collaborators discovered that spotted gar in Caddo Lake have liver damage that appears to be related to mercury. Their study represents some of the first direct evidence that mercury negatively impacts the health of fish.

"There are health benefits to consuming fish as a regular part of a person's diet and not all fish should be avoided. However, both the FDA and the EPA recommend that children and women who are pregnant, nursing or planning to become pregnant should avoid eating fish that exceed the mercury advisory criteria," Roberts says. "It should also be noted that there are potential economic costs to sport fisheries due to mercury's effect on fish reproduction, as well as perceptions of a lake being 'dirty.'"

A research team led by Chumchal examined how mercury moves through the Caddo Lake food web. They found that the entire food chain is contaminated and that many organisms have levels of mercury that could pose a risk to their health.

"Mercury accumulation in fish and wildlife is dependent not only on the deposition of mercury into a lake, but also a number of ecological factors, such as land cover type and sulfate deposition. It appears that several of these factors converge in our region, resulting in high concentrations of mercury in fish," Chumchal says.

High levels of mercury have been well documented in the Northeast and the Great Lakes, but there hasn't been a unified investigation of mercury levels in Texas and the surrounding states prior to this collaboration. Research has shown that mercury contamination can have negative impacts on fish, including damage to immune response, liver function and reproduction.

Mercury also is of particular concern for pregnant women and their unborn children. The results of the recent studies suggest that about 50 percent of the water bodies in North Texas may contain fish with mercury concentrations higher than those deemed safe by the Environmental Protection Agency.

The team recently published a paper on the Caddo Lake Food Web in Environmental Toxicology and Chemistry, a study on the impact of mercury on the livers of fish in Environmental Science and Technology and a study on the distribution of mercury in Texas in Environmental Toxicology and Chemistry. More information about the research can be found on the TCU Aquatic Ecology Lab website and the Roberts' Lab website.

Alyssa Yancey with UNT News Service can be reached at

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January 2012

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