The zebra mussel, Dreissena polymorpha, is a small freshwater mussel. This species was originally native to the streams of southernRussia[1] being first described in 1769 by a German zoologist Peter Simon Pallas in the Ural, Volga and Dnieper rivers. They are still found nearby, as Pontic (Black Sea) and Caspian (Caspian Sea) species.[2] However, it has been accidentally introduced in many other areas, and has become an invasive species in many different countries worldwide.
Zebra mussels attach to most substrates including sand, silt, and harder substrates. Other mussel species frequently represent the most stable objects in silty substrates, and zebra mussels attach to, and often kill these mussels. They build colonies on Native American Unionid clams, reducing their ability to move, feed and breed, eventually leading to their death. This has led to the near extinction of the Unionid clams in Lake St. Clair and the western basin of Lake Erie.[5] This pattern is being repeated in Ireland where zebra mussels have eliminated the two freshwater mussels from several waterways, including some lakes along the River Shannon in 1997.
As an invasive species
The native distribution of the species is in the Black Sea and Caspian Sea in Eurasia. Zebra mussels have become an invasive speciesin North America, Great Britain, Ireland, Italy, Spain, and Sweden. They disrupt the ecosystems by monotypic colonization, and damage harbors and waterways, ships and boats, and water treatment and power plants. Water treatment plants are most impacted because the water intakes bring the microscopic free-swimming larvae directly into the facilities. The Zebra Mussels also cling on to pipes under the water and clog them.
Grossinger reported it in Hungary in 1794. Kerney and Morton described the rapid colonization of Britain by the zebra mussel, first inCambridgeshire in the 1820s, London in 1824, and in the Union Canal near Edinburgh in 1834.[13] In 1827 zebra mussels were seen in the Netherlands at Rotterdam. Canals that artificially link many European waterways facilitated their early dispersal. It is non-indigenous in the Czech Republic in Elbe river in Bohemia since 1893;[14] in southern Moravia is probably native.[15] Around 1920 the mussels reached Lake Mälaren in Sweden.
The first Italian appearance of the organism was in northern Italy in Lake Garda in 1973;[16] in central Italy they appeared in Tuscany in 2003.[17]
Zebra mussels are also present in British waterways. Many water companies are reporting having problems with their water treatment plants with the mussels attaching themselves to pipeworks. Anglian Water has estimated that it costs £500,000 to remove the mussels from their treatment plants.[18] It has been argued that Zebra Mussels also have had an effect on fish populations, with dwindling fish populations in areas such as Salford Quays.[19]
North American invasion
They were first detected in Canada in the Great Lakes in 1988, in Lake St. Clair, located north of Detroit, Michigan, and Windsor, Ontario.[20] It is believed they were inadvertently introduced into the lakes in the ballast water of ocean-going ships traversing the St. Lawrence Seaway. Another possible often neglected mode of introduction is on anchors and chains, although this has not been proven. Since adult zebra mussels can survive out of water for several days or weeks if the temperature is low and humidity is high, chain lockers provide temporary refuge for clusters of adult mussels that could easily be released when transoceanic ships drop anchor in freshwater ports. They have become an invasive species in North America, and as such they are the target of Federal policy to control them, for instance in the National Invasive Species Act (1996).
As zebra mussels have to attach themselves to the crayfish bait, this is one of the ways they have spread to different waterways.[21]
By Location
From their first appearance in American waters in 1988, zebra mussels have spread to a large number of waterways, including Lake Simcoe in the Great Lakes region and theMississippi, Hudson, St. Lawrence, Ohio, Cumberland, Missouri, Tennessee, Michigan, Colorado, and Arkansas Rivers. Today the invasion continues. For instance, in 2009 the Massachusetts Department of Conservation and Recreation confirmed that zebra mussels had been found in Laurel Lake in the Berkshires.[22] That same year the Minnesota Department of Natural Resources announced that live zebra mussels have been found in Pelican Lake, Minnesota. This was the first confirmed sighting in the Red River Basin, which extends across the international border into the province of Manitoba.[23] In July, 2010, the North Dakota Game and Fish Department confirmed the presence of zebra mussel veliger in the Red River between Wahpeton, N.D. and Breckenridge, Minnesota.[24] As recently as 2010 California similarly reported invasions.[25] In 2011 an invasion of the mussels has resulted in reduced water supplies during a drought year, worsening water restrictions across the Dallas area [26]
A common inference made by scientists predicts that the zebra mussel will continue spreading passively, by ship and by pleasure craft, to more rivers in North America. Trailered boat traffic is the most likely vector for invasion into Western North America. This spread is preventable if boaters thoroughly clean and dry their boats and associated equipment before transporting them to new bodies of water. Since no North American predator or combination of predators has been shown to significantly reduce zebra mussel numbers,[citation needed] such spread would most likely result in permanent establishment of zebra mussels in many North American waterways.
<https://en.wikipedia.org/wiki/Zebra_mussel> accessed 5/2/2013
You must be logged in to post a comment.