Zebra mussels, Dreissena polymorha, first arrived in the U.S. in the 1980s in the Great Lakes. Like many other aquatic invaders, this diminutive freshwater mollusk from Eurasia likely arrived in ballast water on large, trans-continental shipping vessels. Zebra mussels have now spread throughout many waterways in the eastern U.S., negatively impacting many aquatic communities. They have also caused biofouling of boat hulls, navigational buoys, and municipal and industrial water-intake facilities.
In addition to their enormous capacity for colony growth and subsequent biofouling, zebra mussels frequently post risks to biological communities. They displace native mollusks through direct competition and physically eliminate fish spawning areas. Perhaps most significanly, zebra mussels feed on phytoplankton—often the foundation of the food chain. With zebra mussels consuming this important resource, native species that rely on phytoplankton have less for themselves. This zebra mussel-caused shortage in phytoplankton can then cause food shortages at all levels of the food chain. Furthermore, decreases in phytoplankton can allow increased light penetration, which in turn may result in increased growth of certain undesirable macrophytes and in increased water tempertures.
Given the risk to regional economies following infestation, and the difficulty in removing zebra mussels once a population gets established, managment tends to focus on limiting the further spread of the organism. This frequently takes the form of community outreach efforts aimed at boaters, anglers, and other recreational user of waterways. These programs highlight the importance of thoroughly cleaning boats and equipment before moving from one water body to another.