Bivalves · Myida · Dreissenidae

Zebra Mussel

Dreissena polymorpha

Least Concern

The species is abundant and widely distributed; it faces no significant short-term risk. See full glossary

The zebra mussel is a freshwater and brackish-water bivalve mollusc. It feeds on plankton and suspended organic matter. It is on the list of the 100 most damaging invasive alien species in the world drawn up by the International Union for Conservation of Nature.

Size

up to 5 cm

Lifespan

5 years

Social structure

Colony

Lives in large concentrations, often for breeding reasons.

Sighting difficulty

Easy

FreshwaterColonial Freshwater Mollusc

33countries 6dive sites

Fun facts

GeneralAn invader that clogs pipes and channels; it reached the Ebro in 2001.
It is the only freshwater bivalve that attaches to hard surfaces with a byssus, as marine mussels do, and that is the key to its success as an invader: it colonises pipes, screens and hulls, which native freshwater clams do not.
It comes from the Ponto-Caspian region and has invaded much of western Europe and North America, above all the Great Lakes.
It filters so much that it clears the water: by removing phytoplankton it increases light penetration, which changes the temperature and the bottom vegetation and reorders the whole ecosystem.
In the Great Lakes its invasion was estimated to cost between 2 and 5 billion dollars over a decade, mainly through blockage of water intakes and cooling systems.
Its ability to accumulate pollutants has made it a standard sentinel species in freshwater biomonitoring, and it is now used as an indicator of microplastics too.
In some areas it is being displaced by a related Ponto-Caspian invader, the quagga mussel.