How did zebra mussels get into the Great Lakes, and why is that a problem?

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How did zebra mussels get into the Great Lakes, and why is that a problem?

It is generally agreed upon by scientists that zebra mussels entered the Great Lakes from ballast water dumping by large ocean-going vessels from Europe. Ballast water is used to keep ships stable in the water. A ship will carry large amounts of ballast water when there is no cargo and will dump it in port as cargo is loaded.

The zebra mussel has the potential to inhabit most of the fresh waters of the U.S. and may impact a variety of native aquatic species and eventually entire ecosystems. They also have had a large economic impact already. Many power plants and water users have had to spend millions of dollars cleaning out zebra mussels from their facilities. In addition, more money has been spent on retrofitting facilities with devices to keep zebra mussels out and to monitor for them. These costs, unfortunately, get passed along to the consumers.

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