The Zebra Mussel

Interesting fact: Zebra mussels are actually razor sharp and can cut the feet of swimmers without them feeling it at first.

The zebra mussel, Dreissena polymopha, is a freshwater shellfish native to  the lakes of Eurassia, in southern Russia. This species spread through Europe to area in Great Britain, Ireland, Italy, Spain, and Sweden by canals. In 1988, the zebra mussel was introduced to North America and quickly spread in the Great lakes. It is theorized that the species was transported accidentally in the ballast water of ocean ships travelling through the St Lawrence River.  It has since spread to lakes in Minnesota, Wisconsin, various other states and in July 2009, to Laurel Lake in Massachussetts.

Zebra mussels cover over the substrate, thus posing a serious threat to native freshwater mussels and clams because they actually smother them. This species breeds prolifically since one female produces 1 million eggs per year. The monotypic colonization of these mussels has actually benefited some populations as a steady food source. Theorized effects of this invasive species includes possibly increasing the number of small mouth bass in Lake Erie and  yellow perch in Lake St Clair. Scientists have suggested that this species may be the source of avian botulism which has killed a variety of birds in the Great Lakes. These filter feeds can process as much as 1 gallon of water per day/mussel and thus large populations quickly clear the lakes they have colonized. This cleansing, though, removes the food supply for larval fish and other invertebrates, disturbing the existing food chain. Also, clearer water allows more light to penetrate the waters and can cause aquatic plants to increase in size, number, or density. These plant blooms can be beneficial to some species, like providing ideal nursery areas for young fish and animals, but can pose a threat to human recreation and municipal water.

Zebra mussels can colonize very densely; they can even grow up to a foot thick in some places. Also they are able to attach themselves to “all types of living and non-living surfaces including boats, water-intake pipes, buoys, docks, piers, plants, and slow moving animals such as native clams, crayfish, and turtles” (glsc). Certain chemicals can be applied to boat hulls to prevent zebra mussels from attaching themselves. When attached to pipelines, zebra mussels can clog water for municipal water supplies and hydroelectric plants. It is quite costly to prevent such situations.

There is no way to eradicate Dreissena polymopha from a lake once it has become established, people instead must prevent their introduction. This species is usually transported through human activity including “recreational boating, fishing, and diving practice” (glsc). Thus certain actions such as removing zebra mussels from boat hulls and decontaminating diving gear can prevent the spread of this invasive species.