The Zebra Mussel Essay Example

Populations of the zebra mussel, Dreissena polymorpha (Pallas), were first found in the Laurentian Great Lakes in 1988 (Hebert et al., 1989). This species is native to the Caspian, Aral, and Black Seas and the rivers that drain into them but has spread throughout Europe, principally during the 18th century. Since it is restricted to estuarine and freshwater habitats, it is presumed that it was introduced into North America by ballast waters of transoceanic vessels. Based on the substantial amount of genetic variation found in these initial populations, as estimated from electrophoretic variation of allozymes, the colonization of the Great Lakes was by a large number of immigrants and not just a few founders (Hebert et al., 1989).

Despite this recency of establishment of this species, the zebra mussel has rapidly spread throughout a large portion of the United States. It has been reported from all the Great Lakes and Lake Champlain, the Mississippi River from St. Paul down to New Orleans, the Illinois River, the Ohio River, and many others (National Aquatic Nuisance Species Clearinghouse; Web site at: http://cce.cornell.edu/aquaticinvaders). This spread has produced a number of negative economical and ecological consequences. Because of its high fecundity and its ability to tightly adhere to surfaces, it is a very serious fouling organism. The weight of attached mussels can become so great that marker buoys can sink. They can also interfere with the workings of lock gates. The main problem for industry is that zebra mussels can line the interiors of intake pipes to such an extent that water flow is blocked or greatly reduced. This blockage can result in heat damage to power plants and necessitates costly removal or replacement of intake pipes (Minchin and Moriarty, 1998).

Colonization by zebra mussels has devastating ecological impacts on native bivalves (Mackie, 1991; Haag et al., 1993), frequently driving them to local extinction. Zebra