8. Zebra Mussel
The World In Spatial Terms Video Vocabulary
The zebra mussel (Dreissena polymorpha) is an invaisve species of shellfish native to the Caspian Sea and Ural River, being first documented in 1769. By the late 18th century and early 29th century, the mussels had spread rapidly through the major waterways of Europe, due to the building of canals. By 1821, zebra mussels entered British waterways and are now a well-established species. In 1998, zebra mussels were discovered on the Canadian side of the Great Lakes, the first account reported a stable population in Lake St. Clair, a water body connecting Lake Huron and Lake Erie. Within two years, zebra mussels were found in all four Great Lakes, and in 1991, the mussels escaped the Great lakes and were found in the Illinois and Hudson Rivers. In the year 1994, a large number of states in cluding Alabama, Arkansas, Illinois, Indiana, Iowa, Kentucky, Louisiana, Michigan, Minnesota, Mississippi, Missouri, New York, Ohio, Oklahoma, Pennsylvania, Tennessee, Utah, Vermont, and West Virginia reported large populations of zebra mussels in border waterways or waterways inside state borders. In a study taken in 2010, the states of Connecticut, Nebraska, South Dakota, California, Colorado, Texas, Oklahoma, Massachusetts, and North Dakota were added to the list of areas with zebra mussel populations. Zebra mussels have an incredibly rapid reproductive growth and no natural predators in North America. And because mussels can attach to each other when they settle, large clusters occur in small areas. As many as 700,000 zebra mussels have been found in only one square yard of surface area on boats, pilings, and pipes. In addition, zebra mussels are efficient at filtering large volumes of water and as an adult may filter more than four quarts a day. This filtration process, although greatly improving water clarity, contributes to the explosive growth of harmful algal blooms in Saginaw Bay and other fresh bodies of water during the summer months. Also, the mussel is low in fat and its shell has no nutritional value causing fish to expend lots of energy crushing and digesting the mussel. The zebra and quagga mussels displace other more energy-rich food sources and leave fish and other aquatic species with fewer food options. As a result, fish stocks and conditions have declined in many of the Great Lakes. Of particular concern is a decline in lake whitefish, an important commercially-fished species.
Sources:
NOAA: http://www.noaa.gov/features/earthobs_0508/zebra.html
USGS: http://nas.er.usgs.gov/queries/factsheet.aspx?speciesid=5
Will Skinner
