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Great Lakes Aquatic Invasive Species
Nonindigenous species, also commonly referred to as nuisance, non-native,
exotic, invasive and alien species, are species that did not originate in the
Great Lakes ecosystem and have been introduced either intentionally or
accidentally. Over 160 species have been introduced into the Great Lakes basin
since the 1800s. More than 1/3 of the species have been introduced into the
Great Lakes in the last half of the 20th century coinciding with the
expansion of the St. Lawrence Seaway in 1959, which allowed greater transoceanic
shipping traffic. Species, such as the zebra mussel, ruffe, goby, and others
also considered aquatic nuisance species (ANS), threaten the diversity or
abundance of native species and the ecological stability of infested waters, or
commercial, agricultural, aquacultural or recreational activity dependent upon
the lake. The four primary vectors of entry include ballast water from
ocean-going ships, unintentional releases, multiple sources and unknown.
The introduction of nonindigenous species into an established ecosystem can
alter or disrupt existing relationships and ecological processes. This
disruption has caused significant changes to the ecosystem, such as alterations
of food webs, nutrient dynamics, reproduction, sustainability, and biodiversity.
Without co-evolved parasites and predators, some nonindigenous aquatic species
are a nuisance because they out-compete and even displace native populations.
Organisms invading the Great Lakes can also threaten public health through
disease, concentration of pollutants, contamination of drinking water, and other
harmful human health effects. Exotic species can also have economic impacts.
Local communities dependent upon water from the Great Lakes or tourism as a
major portion of their economy can be severely impacted by the introduction of
species. Additionally, the quality of life of the citizens of these communities
can be impacted by the introduction of these organisms. The zebra mussel, for
example, colonizes the intake/discharge pipes of hundreds of facilities that use
raw water from the Great Lakes, incurring extensive monitoring and control
costs. Recent studies estimate that over the next ten years, roughly $3 million
will be spent on monitoring and control costs for the zebra mussel. This
estimate excludes impacts on Great Lakes fisheries. Research has yet to
discover an effective control for most of these species. This biological form
of pollution has altered the ecosystem more than pollution by chemical
contaminants ever has.