The invasive zebra mussel has quickly taken over much of the Great Lakes waterways of the United States. The immediate goal is to curb the distribution of these deleterious invaders. A small mussel, with a maximum shell size from 3.5 - 4 centimeters, is usually found in large clusters. It is most likely to be confused with Dreissena bugensis, the Quagga mussel, which is also an introduced species to North America. The native false dark mussel, Mytilopsis leucophaeata, is likely the only native mussel that can be confused with the zebra mussel. Zebra mussels have a salient zebra-like striped pattern on their shells, and also lie flat on a smooth surface, unlike many other mussels.
Zebra mussels have a high rate of filtration, this is further amplified when populations are dense, leading to a decrease in phytoplankton and algae populations. Furthermore, sunlight penetration is increased causing water temperature and Secchi depths (the depth that light penetrates underwater) to also increase. This may be harmful to other aquatic biota as this changes habitat qualities throughout the water column. Additionally, Zebra mussels also feed on zooplankton, and have been associated with their declines as well.
In addition to their ecological effects, zebra mussels may also have a negative impact on the economy. Zebra mussels have the ability to adhere to just about any substrate. Due to their sessile nature, once the veliger larvae has bound to its substrate of choice, mussels develop into adults and are permanently secured via anchors known as byssal threads. These byssal threads allow many zebra mussels to cluster together on various types of subtrates. Including pipes, boats, boat trailers, buoys and dinghys. High cost has been associated with removing zebra mussels from intake pipes to power plants, piping associated with air conditioning, fire hoses, and many others. As they constrict water flow. The mussels may also sink buoys, destroy fishing equipment, and take over objects left in the water for a long period of time.
Zebra mussels are capable of invading new ecosystems through adaptive and anthropogenic factors. First, zebra mussels possess a free-floating larval stage called a veliger stage. Zebra mussel veligers may float in the water column for up to a month, allowing for transportation in ballast water, irrigation water, or pipes for local water supply. The veliger stage, in addition to the ability to breed within the first year of life (as well as aggressive feeding rates) allows Zebra mussels to multiply and expand their territory rapidly.
Adult zebra mussels are able to attach to a wide range of substrates, including boats, boat trailers, or even algae. This allows for easy invasion of multiple lakes if boaters are neglectful of vigorously checking and cleaning their boats. Many states' Department of Natural Resources have attempted to inform and alert boaters of this issue to avoid further invasions.
The Zebra mussel was first observed in North America in 1988 in Lake St. Clair (a body of water that is on the border between Michigan, USA and Ontario, Canada). Since then the zebra mussel has spread to various states located along the Mississippi Waterway, and has been recently reported in Texas, Utah, and California.
Eurasia: specifically Russia
U.S. Habitat: Indigenous to lakes, zebra mussels prefer slow-moving water. They are still found in rivers and streams, but their populations are high in lakes. Very turbid water minimizes zebra mussel populations.
U.S. Present: States associated with the Great Lakes or the Mississippi Waterway. Has expanded to many other states outside those waterways including California, Colorado, Texas and Utah.
Hebert, Paul, B. W. Muncaster, and G. L. Mackie. 1989. Ecological and Genetic Studies on Dreissena polymorpha (Pallas): a New Mollusc in the Great Lakes. Canadian Journal of Fisheries and Acquatic Sciences . 46(9):1587-1591.
Ricciardi, Anthony, Richard Neves, and Joseph Rasmussen. 1998. Impending extinctions of North American freshwater mussels (Unionoida) following the zebra mussel (Dreissena polymorpha) invasion. Journal of Animal Ecology. 67(4):613-619.
Johnson, Ladd, and James Carlton. 1996. Post-Establishment Spread in Large-Scale Invasions: Dispersal Mechanisms of the Zebra Mussel Dreissena polymorpha. Ecology. 77(6):1686-1690.