AN ELECTRONIC TOUR OF THE WORLD OF EXOTIC SPECIES
| What are exotic species (aquatic nuisance species)? |
Exotic species, also called non-indigenous species (NIS), or invasive species, are organisms that have moved beyond their natural geographical range of habitat. They represent all phyla, from microorganisms to various plants and animals, both terrestrial and aquatic. Specially,
exotic aquatics, also called aquatic nuisance species (ANS), are
non-indigenous
species (NIS) 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. |
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| What are the impacts of exotic species? |
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The impacts of introducing non-indigenous species (NIS) or aquatic nuisance species (ANS) can be divided into two areas: ecological (or environmental), and economic. Even they can have bad impacts on human's health. Each exotic species has an ecological impact also has an economic one, and vice versa. ECOLOGICAL
(ENVIRONMENTAL) IMPACTS Introductions do not always have a negative impact, however. Exotic species can help an ecosystem by providing a missing link in a failing food chain. Some scientists believe that introductions can also be beneficial by preserving species in cases where they are endangered or threatened in their natural habitats. Sometimes introducing them into a different habitat enables them to survive, and thus preserve biodiversity. For example, 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. ECONOMIC IMPACTS For example, 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. Not only may exotic species import diseases that affect related species, but
humans as well. Often cures are costly. The threat of non-indigenous species is
their unpredictability. They may be poisonous, serve as vectors for human
disease, or create conditions for disease to spread. Invading species may also
breed with native species, resulting in dangerous or poisonous hybrids, which
humans may unknowingly consume. 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. |
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