Zebra Mussel

• 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.

Skeleton type

Invertebrate - external calcareous bivalve shell (mollusc)

Habitat and environment

Reservoirs, rivers and irrigation canals

Sources consulted: Wikipedia (es): Dreissena polymorpha · ScienceDirect (Hughes 1989) · Science Advances, How colonial animals evolve · Wikipedia, Zooid

The pins mark the dive sites where its presence is documented.