Fish from Lake Aumond have more than twice the levels of mercury as those from nearby Lake Olmstead, according to a new study.
"It was very much of a surprise," said Augusta State University biology professor Donna Wear. Student Jennifer Fernandez helped compile the data.
As part of a project that began this year, largemouth bass from 10 inches to 17 inches long were caught in each lake and sent to the University of Georgia's Plant, Soil & Water Laboratory, which is state-certified to perform mercury analyses in fish tissue.
The results were not only surprising but also reveal that fish consumption advisories might be warranted for one or both lakes, Wear said, adding that the threshold for such advisories in Georgia waters is 0.23 parts per million.
"What we had, on the average in Lake Olmstead, was 0.2786 parts per million," she said. "But the really interesting thing is that in Lake Aumond, we had an average of 0.7454 parts per million."
Lake Olmstead is downstream from Lake Aumond, so it seems more likely that higher mercury levels would be found in Lake Olmstead, she said.
Under state Environmental Protection Division guidelines, levels higher than 0.23 call for suggested consumption limits of one meal per week, and levels of 0.7 parts per million and above yield suggestions of one meal per month.
Levels higher than 2 parts per million yield a "do not eat" advisory.
Mercury occurs naturally in the environment, but heavier loads can be transferred through air pollution emitted by electric generating plants, which are common across the Southeast.
The element can be transported through rainfall and can accumulate in fish tissue that then might then be consumed by anglers.
Such "methylmercury" is a concern because of its potential to damage the nervous system, especially in the developing fetus and young child.
Exposure can affect a baby's brain and the ability to learn and move.
There is no apparent reason why fish from the upstream lake were more contaminated than those downstream, and an analysis by ASU statistician Dharma Thiruvaiyaru failed to find any patterns based on the sex, length or weight of the bass that were tested.
Lake Olmstead, Wear said, was dredged in 1992-93 to remove silt that washed into the area during the 1990 flood, so it might be possible that some of Olmstead's mercury-laden sediment was removed.