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Invasive Species: Zebra Mussels Zebra mussels (Dreissena polymorpha) are natives of the Caspian Sea in Asia. They get their name from the striped pattern found on their shells. In 1988, the first zebra mussels were introduced to the U.S. into the Great Lakes. Since that introduction, the zebra mussel has been steadily moving west across the United States. It seems that the mussels have moved as far west as Minnesota, Kansas, Nebraska, and Oklahoma but confirmed sightings of zebra mussels have occurred in Colorado, Utah, and California. Zebra mussels can live up to 4-8 years and a female produces 30,000 to 1.6 million eggs. They range in size from a ¼ inch to a maximum length of 2 inches. The mussel grows filament-like threads (byssus filaments) from the flat side of its shell that allow it to attach to hard surfaces, such as the bottoms of ships and the components of water facility intakes. Four more lakes in Minnesota have been recently infested with zebra mussels, bringing the total to 10 in the state. In 2009, zebra mussels were found in the Red River Basin watershed for the first time. North Dakota Game and Fish Department biologist Doug Leier reported that the mussels were found in Pelican Lake in northwestern Minnesota’s Otter Tail County.
The barnacle-like zebra mussel poses a multibillion-dollar threat to North America’s industrial, agricultural, and municipal water supplies, and it could become a costly nuisance for freshwater shipping, boating, fishing, and clamming as well. Currently, the annual cost of fighting infestations at water consuming facilities is estimated to be $500 million. Zebra mussels are known for inhabiting intakes and pipes of public water supply facilities, hydroelectric and nuclear power plants, and industrial facilities. They take over pipes and constrict flow, thereby reducing the intake capacity. Zebra mussel densities were as high as 700,000 per square meter at one power plant in Michigan, and the diameters of pipes have been reduced by two-thirds at water treatment facilities. Although there is little information on zebra mussels affecting irrigation, farms, and golf courses, they could be likely candidates for infestations, especially if they have intakes near or on infested waters. Taking Control There are a number of methods currently being researched to help control the growth of zebra mussels including UV Light, acoustical vibration, and different coatings for large vessels. According to a July 2009 press release, the Copper Development Association (CDA) has determined that zebra mussels do not attach to copper-nickel alloys. One of the most widely used copper-nickel alloys is Z-Alloy which is manufactured by Johnson Screens in Brighton, MN. Copper screens and copper based coatings are being used to block the spread of zebra mussels. State agencies are stepping up educational and enforcement efforts to slow the progression of the invasive species. The Minnesota Department of Natural Resources Invasive Species Program, established in 1991, strives to prevent and curb the spread of invasive species within the state, and reduce the impacts caused by invasive species to Minnesota’s ecology, society, and economy. Boaters and others who use the water can contribute to such efforts by taking steps to prevent the transportation of aquatic invasive species from one lake or river to another. Transporting prohibited species is illegal in Minnesota, with violators facing fines up to $500.
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