Zebramussel

Zebramussel, or zebra mussel, Dreissena polymorpha, is a freshwater bivalve mollusk in the family Dreissenidae. Native to the Black Sea and Caspian Sea basins of eastern Europe, it has become one of the most widespread aquatic invaders in the world.

Adults reach up to about 2.5 to 5 centimeters in length and have rounded, laterally compressed shells with alternating dark and light bands, giving a zebra-like appearance. They attach to substrates such as rocks, docks, pipes, and boats using byssal threads. Zebra mussels are filter feeders, consuming suspended algae and phytoplankton. They reproduce rapidly: females can release hundreds of thousands of eggs in a single spawning season, and the released larvae (veligers) drift with the current before settling. Maturation can occur within a year, enabling swift population growth in suitable habitats.

Since their introduction to North America via ballast water in the Great Lakes region in the late 1980s, zebra mussels have spread to numerous inland waterways in Europe and North America. They can form dense colonies that foul surfaces and infrastructure, clog water intakes, and fouling boats, pipelines, and irrigation systems. Ecologically, they increase water clarity by filtering plankton, which can alter plankton communities and affect native species, including unionid mussels that rely on similar food sources.

Management focuses on prevention of spread, mechanical removal, and ongoing monitoring. Chemical control is possible in some settings but impractical at large scales. Public awareness, boat cleaning, draining, and thorough decontamination are key strategies to slow the spread and reduce impacts.