Zebra mussel

Naming

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 affected 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....hieroglyph snipped...
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; in southern Moravia it is probably native. 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; in central Italy they appeared in Tuscany in 2003.

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. 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.

Behavior

The life span of a zebra mussel is four to five years. A female zebra mussel begins to reproduce within 6–7 weeks of settling. : The annual reproductive cycle of the freshwater mussel Dreissena polymorpha Pallas in lakes. Oecologia 87: 208-218).

An adult female zebra mussel can produce 1,000 eggs in each reproductive cycle, and over 1 million each year. Free-swimming microscopic larvae, called veligers, will drift in the water for several weeks and then settle onto any hard surface they can find. Zebra mussels also can tolerate a wide range of environmental conditions and adults can even survive out of water for about 7 days.

Habitat

Zebra mussels and the closely related and ecologically similar quagga mussels are filter-feeding organisms. They remove particles from the water column. The mussels process up to one gallon of water per day, per mussel. 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. Since the zebra mussel has become established in Lake Erie, water clarity has increased from 6 inches to up to three feet in some areas. This improved water clarity allows sunlight to penetrate deeper, enabling growth of macrophyte bacteria. These bacteria, when decaying, wash up on shorelines, fouling beaches and causing water quality problems.

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....hieroglyph snipped... The catch of yellow perch increased 5 fold after the introduction of zebra mussels into Lake St. Clair....hieroglyph snipped...

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. 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.

In 2012 the National University of Ireland, Galway, said "The discovery of zebra mussels in Lough Derg and the lower Shannon region in 1997 has led to considerable concern about the potential ecological and economic damage that this highly invasive aquatic nuisance species can cause."

Predators

Research on natural enemies, both in Europe and North America, has focused on predators, particularly birds and fish (15 and 38 species eating veligers and attached mussels.

The vast majority of the organisms that are natural enemies in Europe are not present in North America. Ecologically similar species do exist, but it is unlikely that these species are able to eliminate those mussels already established and will have a limited role in their control.

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.
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.