Zebra mussel

Zebra mussel
Live zebra mussels underwater with shells open, animals respiring, siphons visible.
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Bivalvia
Subclass:	Heterodonta
Order:	Veneroida
Superfamily:	Dreissenoidea
Family:	Dreissenidae
Genus:	Dreissena
Species:	D. polymorpha
Binomial name
Dreissena polymorpha Pallas, 1771

The zebra mussel, Dreissena polymorpha, is a small freshwater mussel. This species was originally native to the lakes of southeast Russia^[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 superficially resemble marine mussels in the family Mytilidae, and like them, are attached to solid substrates with a byssus. However, zebra mussels are not at all closely related to the mytilids; they are much more closely related to the Veneridae, the Venus clams.

Zebra mussels get their name from a striped pattern which is commonly seen on their shells, though not all shells bear this pattern. They are usually about the size of a fingernail, but can grow to a maximum length of nearly 2 in (5.1 cm).^[3] The shape of the shell is also somewhat variable.

Anatomy

Drawing of zebra mussel, showing the byssus

Zebra mussels are relatively small, with adults ranging from 0.25 to 1.5 in (0.64 to 3.8 cm) long.^[4] They have tiny stripes down their shells. Zebra Mussels have a D-shaped shell. They attach to things with 'strings', byssal threads, which come out of their umbo on the dorsal (hinged) side. Removal of the mussel is therefore difficult.

Ecology

Three color varieties of the shell of the zebra mussel

Close-up of a typical shell of a zebra mussel

Zebra mussels and the closely related and ecologically similar quagga mussels are filter-feeding organisms. They remove particles from the water column. Some particles are consumed as food, and feces are deposited on the lake floor. Non-food particles are combined with mucus and other matter and deposited on lake floors as pseudofeces.

Lake floor food supplies are enriched by zebra mussels as they filter pollution out of the water. This biomass becomes available to bottom feeding species and to the fish that feed on them.^[5] The catch of yellow perch increased 5 fold after the introduction of zebra mussels into Lake St. Clair.^[6]

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.^{[citation needed]} This has eliminated many native mussel species from affected lakes in North America.^{[citation needed]} 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.^{[citation needed]}

Life cycle

The life span of a zebra mussel is four to five years.^[7] A female zebra mussel begins to reproduce within 6-7 weeks of settling. (see Borcherding, J. (1991): The annual reproductive cycle of the freshwater mussel Dreissena polymorpha Pallas in lakes. Oecologia 87: 208-218) Oecologia 87:208-218. In terms of reproduction, zebra mussels are among the most prolific of all animals. An adult female zebra mussel may produce between 30,000 and one million eggs per year.^{[8][not specific enough to verify]} Spawning usually begins in the months from late spring to early summer by free-swimming larvae (veligers), which are microscopic in size, thus invisible to the naked human eye. About two to five percent of zebra mussels reach adulthood.

Predators

There are a number of natural predators of zebra mussel. Zebra mussels have high nutritional value (Walz, 1979^{[not specific enough to verify]}) and are consumed in large quantities by crayfish, waterfowl and in smaller quantities by muskrats.

Crayfish could have a significant impact on the densities of 1 to 5 mm long zebra mussels. An adult crayfish consumes an average of nearly 105 zebra mussels every day, or about 6000 mussels in a season. Predation rates are significantly reduced at cooler water temperatures.

Several species of fish consume zebra mussels. Of these, roach seems to have the most significant impact on mussel densities. In some Polish lakes the diet of the roach consists almost exclusively (~95%) of zebra mussels (Stanczykowska, 1957^{[not specific enough to verify]}). Despite all this, it seems that fish do not limit the densities of zebra mussels in European lakes. Smallmouth bass are a predator in the zebra mussels' adopted North American Great Lakes habitat.^[9]

As an invasive species

Sign advising boaters on how to prevent zebra mussel spread on Titicus Reservoir in North Salem, New York

The native distribution of the species is in the Black Sea and Caspian Sea in Eurasia. Zebra mussels have become an invasive species in 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 in Cambridgeshire in the 1820s, London in 1824, and in the Union Canal near Edinburgh in 1834.^[9] 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;^[10] in southern Moravia is probably native.^[11] 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;^[12] in central Italy they appeared in Tuscany in 2003.^[13]

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.^[14]

North American invasion

In the U.S. and Canada, they were first detected in the Great Lakes in 1988, in Lake St. Clair, located between Detroit, Michigan, and Windsor, Ontario.^[15] 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. In 1990 almost every surface the zebra muscles could grow on they were on. 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 also been known to attach themselves to the crayfish bait, this is one of the ways they have spread to different waterways.^[16]

By Location

From their first appearance in American waters in 1988, zebra mussels have spread to a large number of waterways, including Lake Simcoe the Great Lakes region and the Mississippi, Hudson, St. Lawrence, Ohio, Cumberland, Missouri, Tennessee, 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.^[17] 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.^[18] 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.^[19] As recently as 2010 California similarly reported invasions.^[20]

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.

Cost

The cost of fighting the pests at power plants and other water-consuming facilities is substantial, but the exact magnitude of the damage is a matter of some controversy. According to the Center for Invasive Species Research at the University of California, Riverside,^[15] the cost of management of Zebra mussel in the Great Lakes alone exceeds $500 million a year. A more conservative study estimated total economic costs of $267 million for electric generation and water treatment facilities in the entire United States from 1989 through 2004.^[21]

Effects of zebra mussels

Zebra mussel infestation on the walls of Arthur V. Ormond Lock on the Arkansas River

Zebra mussel-encrusted Vector Averaging Current Meter from Lake Michigan

Zebra mussels are filter feeders. When in the water, they open their shells to admit detritus. As their shells are very sharp, they are known for cutting people's feet, resulting in the need to wear water shoes wherever they are prevalent.

Since their colonization of the Great Lakes, they have covered the undersides of docks, boats, and anchors. They have also spread into streams and rivers nationwide. In some areas they completely cover the substrate, sometimes covering other freshwater mussels. They can grow so densely that they block pipelines, clogging water intakes of municipal water supplies and hydroelectric companies. Recent research has found that zebra mussels don't attach to cupronickel alloys, which can be used to coat intake and discharge grates, navigational buoys, boats, and motors where the species tend to congregate.^[15]

Zebra mussels are believed to be the source of deadly avian botulism poisoning that has killed tens of thousands of birds in the Great Lakes since the late 1990s.^[22]

They are also responsible for many species near extinction in certain areas of the great lake system like georgian bay they out work native species for food and grow on top of the native clams and mussels suffocating them

However, zebra mussels and other non-native species are credited with the increased population and size of smallmouth bass in Lake Erie^[23] and yellow perch in Lake St. Clair.^[24] They cleanse the waters of inland lakes, resulting in increased sunlight penetration and growth of native algae at greater depths. This cleansing also increases water visibility and filters out pollutants. Each quagga and zebra mussel filters about 1 US quart (0.95 l) of water a day when confined to small tanks.^[25] In lakes, their filtering effects are usually spatially restricted (near the lake bottom) due to non-homogeneous water column mixing.

See also

• Quagga mussel

References

1. ^ Hoddle, M. S.. "Quagga & Zebra Mussels". Center for Invasive Species Research, UC Riverside. http://cisr.ucr.edu/quagga_zebra_mussels.html. Retrieved 2010-06-29. 
2. ^ (Slovak) Lisický M. J. 1991. Mollusca Slovenska [The Slovak molluscs]. VEDA vydavateľstvo Slovenskej akadémie vied, Bratislava, 344 pp.
3. ^ The National Atlas of the United States of America (2009-09-17). "Zebra Mussels". Nationalatlas.gov. http://nationalatlas.gov/articles/biology/a_zm.html. Retrieved 2010-06-29. 
4. ^ "Zebra mussel — Invasive species: Minnesota DNR". Dnr.state.mn.us. 1999-08-24. http://www.dnr.state.mn.us/invasives/aquaticanimals/zebramussel/index.html. Retrieved 2010-06-29. 
5. ^ Garton, D. W.; Berg, D. J.; Stoeckmann, A. M.; Hagg, W. R. (1993). Biology of recent invertebrate invading species in the Great Lakes: The spiny water flea, Bythotrephes cederstoemi, and the zebra mussel, Dreissena polymorpha. (in B. N. McKnight editor. Biological pollution: The control and impact of invasive exotic species. ed.). Indianapolis, Indiana.: Indiana Academy of Science.. pp. 63–84 
6. ^ Saggoff, M. (Accessed July 2007) (^{[dead link]}). What’s Wrong with Exotic Species?. College Park, Maryland: Institute for Philosophy and Public Policy, Maryland School of Public Affairs. http://www.puaf.umd.edu/IPPP/fall1999/exotic_species.htm 
7. ^ Amy Benson (2009-12-22). "Zebra mussel FAQs". Fl.biology.usgs.gov. http://fl.biology.usgs.gov/Nonindigenous_Species/Zebra_mussel_FAQs/zebra_mussel_faqs.html. Retrieved 2010-06-29. 
8. ^ /nationalatlas.gov
9. ^ ^{a b} Mackie, G; Gibbons, W; Muncaster, B; Gray, I (1989). The Zebra Mussel, Dreissena polymorpha: A synthesis of European Experiences and a preview for North America. Ontario Ministry of Environment 
10. ^ Blažka, F. (1893). "Do Čech zavlečená slávka: Dreissena polymorpha Pall" (in Czech). Vesmír 22 (15): 177–178. 
11. ^ (Czech) Horsák M., Juřičková L., Beran L., Čejka T. & Dvořák L. (2010). "Komentovaný seznam měkkýšů zjištěných ve volné přírodě České a Slovenské republiky. [Annotated list of mollusc species recorded outdoors in the Czech and Slovak Republics]". Malacologica Bohemoslovaca, Suppl. 1: 1-37. PDF.
12. ^ "Dreissena polymorpha (Pallas) nuovamente in Italia. (Bivalvia, Dreissenidae)" (in Italian). Mem Mus Civ St Nat Verona 20: 45–49. 1973. 
13. ^ "New records of Dreissena polymorpha (Pallas, 1771) (Mollusca: Bivalvia: Dreissenidae) from Central Italy". Aquatic Invasions 1 (4): 281–283. 2006. doi:10.3391/ai.2006.1.4.11. http://www.aquaticinvasions.ru/2006/AI_2006_1_4_Lori_Cianfanelli.pdf. 
14. ^ "British waterways fight invasion by Russian zebra mussels". BBC News. 2011-08-04. http://www.bbc.co.uk/news/science-environment-14398995. 
15. ^ ^{a b c} "Zebra Mussels Overwhelm U.S. Waterways in the Great Lakes Region and Beyond - Copper Screens and Coatings Provide a Solution to this $500 million Problem". Copper Development Association. 2009-07-30. Archived from the original on 2011-03-13. http://www.webcitation.org/5x9UPINSt. 
16. ^ J. Thompson, F. Parchaso, A. Alpine, J. Cloern, B. Cole, O. Mace, J. Edmunds, J. Baylosis, S. Luoma & F. Nichols (December 13, 2007). "The History and Effects of Exotic Species in San Francisco Bay". United States Geological Survey. http://sfbay.wr.usgs.gov/benthic_eco/exotic_species/next.html. 
17. ^ "2 Mass. towns start fight against zebra mussel". Boston Herald. 2009-07-13. http://www.bostonherald.com/news/regional/view/200907132_mass_towns_start_fight_against_zebra_mussel/srvc=home&position=recent 
18. ^ "Zebra mussels found in Pelican Lake in Otter Tail County" (Press release). MN Department of Natural Resources. 2009-09-17. http://news.dnr.state.mn.us/index.php/2009/09/17/zebra-mussels-found-in-pelican-lake-in-otter-tail-county/#more-43227. Retrieved 2009-09-18. 
19. ^ "Zebra Mussel Discovered in North Dakota" (Press release). ND Game and Fish Department. 2010-07-01. http://gf.nd.gov/multimedia/news/2010/07/100701.html. Retrieved 2010-07-02. 
20. ^ http://fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5144740.pdf usda.gov. Zebra mussels found. Access date: 5/22/2010.
21. ^ "Economic impacts of zebra mussels on drinking water treatment and electric power generation facilities". 2007-05-24. http://www.ncbi.nlm.nih.gov/pubmed/17530329. 
22. ^ Janega, James (2008-01-15). "Botulism takes fatal toll on thousands of Great Lakes birds". Chicago Tribune. Archived from the original on 2011-04-05. http://www.webcitation.org/5xiuS7cmi. Retrieved 2011-04-05. 
23. ^ "Report at ESPN Sports". Sports.espn.go.com. 2005-03-16. http://sports.espn.go.com/outdoors/bassmaster/news/story?page=tourn_03_north_open_NY_erie_preview. Retrieved 2010-06-29. 
24. ^ Exotic species at PUAF.
25. ^ "Great Lakes: 'Amazing change'". http://michigantoday.umich.edu/2009/07/story.php?id=7510&tr=y&auid=5077806. Retrieved 2009-08-06. 

Further reading

• Minchin, D. 2003. The Zebra Mussel Dreissena polymopha (Pallas) extends its range westwards in Ireland. Bull. Ir. biogeog. Soc. 26: 176 - 18.

External links

• Zebra mussels in Kawartha Lakes, by Jim Russell
• Zebra Mussel on National Atlas
• Dreissina FAQs
• Species Profile- Zebra Mussel (Dreissena polymorpha), National Invasive Species Information Center, United States National Agricultural Library. Lists general information and resources for Zebra Mussel.
• Zebra Mussel Watch
• Charting the progression of the Zebra mussel in the Eastern United States
• Zebra mussel in N.I.
• CISR - Zebra Mussels Center for Invasive Species Research summary on Zebra Mussels
• GLANSIS Species FactSheet
• Did the Zebra Mussel affect Atlantic Fishing?-C.Yukna (EMSE France)