Effects of Zebra Mussels
Zebra mussels are filter feeders. When in the water, they open their shells to admit detritus. As their shells are very sharp, they are known for cutting people's feet, resulting in the need to wear water shoes wherever they are prevalent.
Since their colonization of the Great Lakes, they have covered the undersides of docks, boats, and anchors. They have also spread into streams and rivers nationwide. In some areas they completely cover the substrate, sometimes covering other freshwater mussels. They can grow so densely that they block pipelines, clogging water intakes of municipal water supplies and hydroelectric companies. Recent research has found that zebra mussels don't attach to cupronickel alloys, which can be used to coat intake and discharge grates, navigational buoys, boats, and motors where the species tend to congregate.
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. Because they are so efficient at filtering water, they tend to accumulate pollutants and toxins. For this reason, although they are edible, most experts recommend against consuming zebra mussels.
They are also responsible for the near extinction of many species in the Great Lake system by out-competing native species for food and by growing on top of and suffocating the native clams and mussels.
However, zebra mussels and other non-native species are credited with the increased population and size of smallmouth bass in Lake Erie and yellow perch in Lake St. Clair. They cleanse the waters of inland lakes, resulting in increased sunlight penetration and growth of native algae at greater depths. This cleansing also increases water visibility and filters out pollutants. Each quagga and zebra mussel filters about 1 US quart (0.95 l) of water a day when confined to small tanks. In lakes, their filtering effects are usually spatially restricted (near the lake bottom) due to non-homogeneous water column mixing.
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