Dreissena

Dreissena polymorpha1

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Dreissena is a genus of freshwater molluscs in the family Dreissenidae, commonly known as zebra mussels and quagga mussels. These small, bivalve molluscs are native to the lakes of southern Russia and Ukraine, but have become invasive species in numerous other regions, notably in North America, where they pose significant environmental and economic challenges.

Description

Members of the genus Dreissena are characterized by their distinctive bivalve shells, which are typically marked with zebra-like stripes in the case of the zebra mussel (Dreissena polymorpha), or a more uniform, pale coloration in the case of the quagga mussel (Dreissena bugensis). These mussels attach to surfaces using byssal threads, allowing them to form dense colonies that can clog water intake pipes, affect aquatic structures, and outcompete native species for food and habitat.

Ecology and Habitat

Dreissena species are adaptable to a variety of freshwater habitats but prefer waters that are rich in calcium, which is necessary for shell development. They are filter feeders, consuming plankton and other small particles from the water, which can lead to increased water clarity but also disrupt local ecosystems by removing significant amounts of phytoplankton and zooplankton, the base of the aquatic food web.

Invasive Species

The spread of Dreissena species beyond their native range is primarily attributed to human activities, particularly the discharge of ballast water from ships and the movement of contaminated watercraft. Once established, they can spread rapidly and are difficult to eradicate. Their presence in non-native waters has been linked to declines in native mussel populations, alterations in aquatic ecosystems, and significant economic costs associated with the maintenance of water intake systems and other infrastructure.

Management and Control

Efforts to manage and control Dreissena populations include physical removal, chemical treatments, and the introduction of biological controls. Preventative measures, such as thorough cleaning of watercraft before moving them between bodies of water, are also critical in preventing their spread.

Impact

The environmental impact of Dreissena invasions includes altered water chemistry, changes in the abundance and diversity of native species, and increased costs for water treatment and power generation facilities. Economically, they can affect industries reliant on affected waterways, including fishing, tourism, and water supply.

Research

Ongoing research aims to better understand the biology and ecology of Dreissena species, develop more effective control methods, and assess their long-term impact on invaded ecosystems.

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