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Collaborative research finds mercury contamination in fish species

Aaron Roberts, assistant professor of biologyTwo TCU researchers have discovered a 64,000-square-kilometer area in eastern Texas with high concentrations of toxic mercury, and are working with UNT's Aaron Roberts, right, assistant professor of biology, to study the implications of the contamination of fish and other organisms.  

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

Ray Drenner, professor and chair of the Department of Biology, and Matt Chumchal, assistant professor of biology, both at TCU, 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.

Roberts 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, left, 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.

Mercury pollution study on fish and wildlife at Caddo lakeA research team led by Chumchal then 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,” said Chumchal.

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.

“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 avoid eating fish that exceed the mercury advisory criteria,” said Roberts. “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.’”

Chumchal and Drenner are ecologists who specialize in studying the trophic transfer and biogeochemistry of mercury in the region. Roberts is a mechanistic toxicologist who studies the health impacts of a wide array of contaminants, including mercury. 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.

- Alyssa Yancey, News Promotions, and Holly Ellman, TCU

Posted on: Mon 07 November 2011

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