Aquatic Nuisance Species (ANS) are nonindigenous species that threaten the diversity or abundance of native species or the ecological stability of infested waters, or commercial, agricultural, aquacultural or recreational activities dependent on such waters. ANS include nonindigenous species that may occur in inland, estuarine and marine waters and that presently or potentially threaten ecological processes and natural resources. In addition to adversely affecting activities dependant on waters of the United States, ANS adversely affect individuals, including health effects.

Nonindigenous Species (NIS) are any species or other viable biological material that enters an ecosystem beyond its historic range, including any such organism transferred from one country into another. Nonindigenous species include both exotics and transplants. Synonyms for NIS include introduced, foreign, exotic, alien, non-native, immigrant and transplants.

The table below provides a list of the 3 classes of adverse impacts caused by aquatic nuisance species:

Nonindigenous aquatic species impact biological and economic resources and can also impact human health. Nonindigenous species disturb native species through predation or displacement, clog intake pipes for municipal and industrial water supplies and can pose serious human health risks. Great Lakes water users spend tens of millions of dollars on zebra mussel control every year. Affected municipalities and industries, using large volumes of Great Lakes water, expend approximately $360,000 per year on zebra mussel control; small municipalities average $20,000. Nuclear power plants average an additional $825,000 of additional costs per year for zebra mussel control. As the zebra mussel spreads to inland lakes and rivers across North America, such as the Mississippi River Basin and Lake Champlain, so do the costs to water users. Other invading species of fish (such as the sea lamprey, ruffe and round goby) can harm native fish. Reductions in native fish populations (such as lake trout, walleye, yellow perch and catfish) threaten a sport and commercial fishing industry that is valued at almost $4.5 billion annually and supports 81,000 jobs.

Zebra mussel infestations cause pronounced ecological changes in the Great Lakes and major rivers of the central United States. The zebra mussel's rapid reproduction, coupled with consumption of microscopic plants and animals, affects the aquatic food web and places valuable commercial and sport fisheries at risk. In waters infested with the zebra mussel, large blooms of potentially toxic blue-green algae have been observed in waters such as Saginaw Bay, Lake Huron and the western basin of Lake Erie.

Nonindigenous aquatic nuisance plants, such as giant salvinia, purple loosestrife, Eurasian watermilfoil and hydrilla quickly establish themselves replacing native plants. Environmental and economic problems caused by the dense growth of these weeds include impairment of water-based recreation, navigation and flood control, degradation of water quality and fish and wildlife habitat, accelerated filling of lakes and reservoirs and depressed property values.

ANS invasions also can pose serious health risks. A South American strain of human cholera bacteria was found in ballast tanks in the port of Mobile, Alabama in 1991. Cholera strains were also found in oyster and fin-fish samples in Mobile Bay, resulting in a public health advisory to avoid handling or eating raw oysters or seafood.

More information on Impacts of Aquatic Nonindigenous Species is available on this website and at www.protectyourwaters.net.

The Great Lakes Information Network provides further information on Impacts