Great Lakes Invaders

April 27, 2003


Provided and copyright by: Peg Staudenmaier
Summary authors & editors: Peg Staudenmaier

This photo shows zebra mussel shells (Dreissena polymorpha) littering the Lake Michigan shore at Point Beach State Forest, Two Rivers, Wisconsin. These invaders from the Caspian Sea region have caused billions of dollars in damage to industry, agriculture and fresh water supplies. They were first discovered in 1988 and believed to have been dumped from ballast tanks of oceanic vessels into Lake St. Clair. They're populating lakes farther inland by attaching themselves to recreational boats. Latest findings indicate that these inch-long (2.54 cm) creatures may be a threat to the food chain of Lake Michigan's whitefish as well as other species. Their numbers in the Great Lakes and virtually every connecting body of water in the Great Lakes watershed is out of control.

Adult zebra mussels colonize nearly all types of living and non-living surfaces including boats, water-intake pipes, docks, slow moving animals such as clams, even each other. See also the Earth Science Picture of the Day for May 16, 2002.

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