Zebra Mussel Invasion Hits Landmark

WASHINGTON — The 20th anniversary of the discovery of zebra mussels in the Great Lakes was marked last week with regret and a warning by U.S. and Canadian conservationists.

The tiny mussels are an invasive species that wreak havoc on aquatic ecosystems.

"It’s time to stop thinking of them as a Great Lakes crisis," said Jennifer Nalbone of Great Lakes United on a conference call. "The invasion struck suddenly, spread quickly and now it’s a national crisis."

In Wisconsin, the zebra mussel has invaded the Mississippi River and roughly 75 inland bodies of water, said Philip Moy, a fisheries and invasive species specialist with the University of Wisconsin-Madison Sea Grant Institute.

"But we have 15,000 water bodies in the state and the mussels are only in one half of one percent of our state waters," he said.

The invasion of quagga mussels in Lake Michigan is even more serious — beds of zebra mussels in the lake have been colonized and overgrown by quaggas. Dense quagga populations, close to 40,000 per square meter, have been observed by scientists at the University of Wisconsin-Milwaukee’s Great Lakes WATER Institute.

Zebra mussels are fingernail-sized mollusks that look like little striped clams. They attach themselves to hard surfaces such as the shells of native mussels, boats, water pipes, dock pilings and submerged rocks. They grow in clusters in algae-rich shallow water. In winter, they are dormant and do not feed.

Quagga mussels can live on lake bottoms where the water is deep and cold, as well as in warm and shallow waters. Quaggas are never dormant and feed continuously.

Quaggas have the potential to cover much of the bottom of Lake Michigan, said Jeffrey Bode, a lakes, wetlands and aquatic invasive species specialist at the Wisconsin Department of Natural Resources.

The mussels feed by drawing in water and eating the microscopic plants and animals floating in it. The result is a combination of oxygen and food depletion for fish and other organisms.

"This may mean that fish won’t have the same growth rate as they’ve had in the past," Bode said.

The base of the food web — 80% of the food in the bottom sediments of the Great Lakes — has crashed, said Andy Buchsbaum, regional executive director of the Great Lakes office of the National Wildlife Federation.

Despite the concern about quaggas, zebra mussels are still a problem, Bode said. "Absolutely. They aren’t decreasing. New water bodies are showing new populations."

He is concerned about zebra mussels moving from the Mississippi River into the St. Croix River and from the Great Lakes into their tributaries. Bode also is working to prevent zebra mussels in Lake Winnebago and the lower Fox River from migrating upstream.

"Our primary emphasis is prevention and education," he said, teaching people to take responsibility for keeping their boats and equipment clean.

The conservationists issued a call to action for the federal governments of both countries to enact more stringent legislation to regulate the ballast water of ships coming into the Great Lakes.

In the House, the Aquatic Invasive Species Research Act is in a Natural Resources subcommittee awaiting debate. Tammy Baldwin (D-Madison), Steve Kagen (D-Appleton) and Tom Petri (R-Fond du Lac) are co-sponsors.

Wisconsin law states a boat cannot be launched if it has weeds or zebra mussels attached to it. Moy said he is hopeful that the law will be made stricter.