Zebra Mussels (Dreissena polymorpha)
Introduction
A small freshwater mussel that has been introduced into the Great Lakes and other native waters from Europe is known as the zebra mussel. This alien species has caused millions of dollars of environmental and economic damage in the Great Lakes region. Native to Europe, they were introduced to this country, probably in the ballast waters of commercial ships.
Characteristics
The zebra mussel is a freshwater mollusk that has a life span of 3 to 5 years (U.S. Fish and Wildlife Service, 1993). Zebra mussels are distinguished from native species by their small size (approximately an inch long) and the alternating light and dark bands present on their shells.
Ecological and Economical Impacts
Zebra mussels have the ability to remove a large portion of the plankton and dissolved nutrients within the water (U.S. Fish and Wildlife Service, 1993). Even though this increases the clarity of the water, it changes the food web that the native freshwater mussels and other organisms need to survive (U.S. Fish and Wildlife Service, 1993). This would, in time, decrease the native populations within their habitat (U.S. Fish and Wildlife Service, 1993). Native mussels have been eliminated from the western basin of Lake Erie by the zebra mussels (Watters, 1995).
Zebra mussels can be found attached to any type of firm substrate such as piers, boats, rocks, plants, and even native mussels. They have also been found on intake systems of factories, power facilities, and municipal water supplies.
Zebra mussels do have a variety of predators: ducks, various fish species (catfish, drum), raccoons, etc., but they do not seem to affect the exponential population growth of the zebra mussels.
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