Thursday, May 11, 2006

ENV: Eradicating Zebra Mussels

Zebra Mussels Eradicated in Va. Quarry
Scientists Eradicate an Infestation of Zebra Mussels in a Virginia Quarry
By KRISTEN GELINEAU, The Associated Press

RICHMOND, Va. - An infestation of zebra mussels in a Virginia quarry has been eradicated, marking what biologists and environmental experts believe is the first successful extermination of the notoriously invasive species in open waters.

"I'm not aware of any other successful eradication," said zebra mussel expert Hugh MacIsaac, invasive species research chair at the Great Lakes Institute for Environmental Research in Ontario, Canada. "That's quite impressive."

The small black-and-white striped mussels, native to eastern Europe, were first discovered in Virginia in a Prince William County quarry in August 2002, surprising and concerning state wildlife officials.

Zebra mussels are voracious eaters, gobbling up large amounts of plankton the same food many native freshwater fish need to survive. They also pose a threat to utility companies by clogging industrial pipes.

"Zebra mussels throughout North America and, in fact, throughout Europe, are a serious threat," said Ray Fernald, manager of nongame and environmental programs for the Virginia Department of Game and Inland Fisheries. "The economic and environmental damage that they can cause is tremendous."

A contractor, Aquatic Sciences L.P., of Orchard Park, N.Y., injected the quarry with thousands of gallons of potassium chloride solution over a three week period beginning in late January. The solution, while toxic to zebra mussels, did not pose a threat to the environment or humans, Fernald said Thursday.

To verify that all the creatures had been killed, thousands of zebra mussels were imported from the Great Lakes and suspended throughout the 12-acre quarry in mesh bags in late March. On May 2, officials checked the creatures in the bags and determined all were dead. More than a thousand other mussels scraped from the rocks at various sites throughout the quarry were also examined and deemed dead, and scuba divers conducted a visual inspection of the quarry to make sure no live mussels were left.

The eradication process cost about $365,000, Fernald said. Water quality at the quarry and in nearby landowners' wells will be monitored for the next two years, he said.

While Virginia's success with potassium chloride could be replicated in smaller bodies of water infested by zebra mussels, one invasive species expert said the approach would likely fail in a region as large as the Great Lakes.

"Trying to do that on Lake Michigan, or a thousand-acre lake the cost would just be prohibitive," said Phil Moy, a fisheries and non-indigenous species outreach specialist at the University of Wisconsin Sea Grant Institute.

Zebra mussels are difficult to eradicate because they reproduce very quickly, said Thomas Horvath, a professor at the State University of New York in Oneonta who has been researching zebra mussels for about 15 years.

There has been at least one other attempt to eliminate zebra mussels from a body of water. In 1999, researchers from Rensselaer Polytechnic Institute began manually pulling the unwelcome mollusks from Lake George in New York. Since then, the population has declined dramatically, but has not been completely eradicated, said Sandra Nierzwicki-Bauer, a professor at Rensselaer who directs the zebra mussel removal efforts.

You're not going to necessarily get every single last one," she said. "But our goal was initially to go in and to remove the bulk of them. And we did that."

Zebra mussels were first discovered in the United States in 1988 in the Great Lakes, after apparently being carried in a trans-Atlantic ship's ballast water, which was emptied in the lakes. In addition to the five Great Lakes, the creatures have been found in 398 lakes nationwide, as far west as Kansas and as far south as Louisiana, according to the U.S. Geological Survey.

Amy Benson, a fisheries biologist with the U.S. Geological Survey, cautioned against celebrating too soon.

"You never know, they could be back next year," Benson said. "Mother nature has a way of surviving."

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