Zebra and Quagga Mussels

The zebra mussel was originally native to the lakes of southern Russia and Ukraine but was accidentally introduced into numerous other areas and has become an invasive species worldwide most notably the US, Great Britain, Ireland, Italy, Spain and Sweden. It is thought they were introduced into North America in 1988 through the ballast release of a commercial cargo ship traveling from the Black Sea to the Great Lakes. They are now established in all the Great Lakes, many small lakes in the Great Lakes region, all the large rivers of the eastern Mississippi drainage, and all of the large navigable rivers in the eastern United States. They have also been found in Texas, Colorado, Utah, Nevada, and California. Its rapid dispersal is due to passive drifting in the larval stage and their ability to attach to boats and then travel overland. A common inference made by scientists predicts that the zebra mussel will continue spreading passively most likely resulting in the permanent establishment of zebra mussels in many North American waterways.

Zebra mussels negatively impact ecosystems in many ways. They are responsible for the near extinction of many species in the Great Lake system by outcompeting native species for food and by growing on top of and suffocating the native clams and mussels.

Zebra mussels primarily consume phytoplankton, but also filter out other suspended material from the water column including bacteria, protozoans, other microzooplankton and silt, unfortunately however, they do not consume blue-green algae. As the invasion spread eastward during 1988 to 1990, sampling stations recorded declines in total algae abundance from 62{c84f4263cff769fd6fda75e481f8c50ebc0ba520b41f3ff17aef52667440c57e} to 90{c84f4263cff769fd6fda75e481f8c50ebc0ba520b41f3ff17aef52667440c57e}. In Saginaw Bay, a 60–70{c84f4263cff769fd6fda75e481f8c50ebc0ba520b41f3ff17aef52667440c57e} drop in chlorophyll-a and doubling of Secchi depth was recorded. Zooplankton abundance dropped 55-71{c84f4263cff769fd6fda75e481f8c50ebc0ba520b41f3ff17aef52667440c57e} following mussel invasion in Lake Erie. Reductions in zooplankton biomass may cause decreased biomass of planktivorous fish., Unionids have been extirpated from Lake St. Clair and nearly so in western Lake Erie. Biomagnification of toxins into both fish and birds is possible. Zebra mussels are believed to be the source of deadly avian botulism poisoning that has killed tens of thousands of birds in the Great Lakes since the late 1990s.

Since the zebra mussel has become established in Lake Erie, water clarity has increased from 6 inches to up to three feet in some areas. This increased water clarity allows sunlight to penetrate deeper, enabling growth of submerged macrophytes. These plants, when decaying, wash up on shorelines, fouling beaches and causing water-quality problems.

Recreational areas have been extensively fouled reducing their enjoyment and power plants spend millions of dollars removing zebra mussels from clogged water intakes. According to the Center for Invasive Species Research at the University of California, Riverside, the cost of management of zebra mussel in the Great Lakes alone exceeds $500 million per year. Congressional researchers have estimated that the zebra mussel has cost businesses and communities over $5 billion since their initial invasion. Zebra mussels have cost power companies alone over $3 billion.