The technique takes advantage of low energy radio waves. “Zapping” zebra mussels with these waves forces them to surrender essential minerals such as the calcium they need to maintain their shells, says Matthew F. Ryan, Ph.D., a chemist at Purdue University Calumet in Hammond, Ind., and principle investigator for the study.
These freshwater critters, not to be confused with saltwater mussels consumed by humans, suck in liters of water a day, thus absorbing large amounts of nutrients, as well as heavy metals and environmental toxins. Unfortunately they leave few nutrients behind for other lake dwellers such as crabs, crayfish and other species of freshwater mussels.
Zebra mussels lay their eggs near intake pipes of electric generating stations. Their dust-sized larvae attach to the interior of the pipes, then grow to approximately the size of a lima bean, clogging the pipes to the point that they’re unusable.
Zebra mussels immigrated to the United States in the mid-80s as stowaways on foreign ships. Although first discovered in the Great Lakes, they are now causing trouble in nearly every body of fresh water from the Mississippi River to the Ohio River to inland lakes in Wisconsin.
Chemicals such as chlorine and bromine have been used to remove zebra mussels. While they are effective, some ecologists are concerned that overuse of such chemicals might be polluting lakes and streams. Another approach has been the use of molluscicides. But Ryan says they aren’t fully understood and may add to the growing list of environmental toxins.
The use of low-energy radio waves appears promising. Ryan and coworkers exposed 1,100 zebra mussels in large fish tanks to low-energy radio waves from a generator placed roughly a meter away. All died within 40 days. In the unexposed group, only 10 percent of the mussels died. Moreover, the researchers measured a fourfold increase of calcium in the water compared to the unexposed group. Ryan says, “If you have an excess of calcium in the water, you know it can only be coming from the zebra mussels.”
At the same time, Ryan reports, other exposed organisms like crabs, crayfish and other freshwater mussels were significantly less affected. Fish were unharmed.
Ryan and coworkers plan field tests using low-energy radio wave generators placed near intake pipes. “We can’t get the zebra mussels out of the Great Lakes, but we can certainly prevent them from settling into intake pipes,” says Ryan.
The paper on this research, ENVR 78, will be presented at 11:35 a.m., Tuesday, August 28, at McCormick Park South, Room S502A, Level 5.
Matthew F. Ryan, Ph.D., is an Associate Professor of Chemistry at Purdue University Calumet in Hammond, Ind.
— by Linda Wang
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