Invasive species are non-native plants and animals whose presence degrades habitat, outcompetes native species, and decimates the food web. They are introduced to the environment by humans, animals, and various modes of transportation and interconnecting pathways (i.e. rivers). The Great Lakes are susceptible to invasive species, with ocean freight transportation being a major contributor. Sixty-five percent of the invasive species in the Great Lakes arrived through the discharge of ballast water from these ocean-going freighters. Another major source of invasive species entering the Great Lakes has been through canals and waterways. To date, there are more than 180 known invasive species in the Great Lakes.
The biggest threat to life in and on the Great Lakes may be Asian Carp, which would massively disrupt the food chain in the Great Lakes. Should Asian Carp enter the Great Lakes, the economic cost for fisheries alone is estimated at $7 billion per year. The fish will likely enter Lake Michigan via the Chicago River or other waterways connected to the Mississippi watershed.
The introduction of invasive species via canals and waterways is complex, and the Asian Carp threat brings these issues to light. There are 18 points along the Great Lakes Basin and the Mississippi Basin that pose risks where Asian Carp and other species could potentially enter into the Great Lakes. Among the highest risks is the Chicago River in Illinois. The Chicago River was reversed at the turn of the century to flush Chicago’s sewage through the canals, the Des Plaines River, and eventually to the Mississippi River. The long-anticipated Great Lakes and Mississippi River Interbasin Study was released in 2015 by the U.S. Army Corps of Engineers. The study affirmed the feasibility of the hydroseparation of the Great Lakes and Mississippi River Basins to restore the continental divide and prevent further transfer of invasive species, but the project was estimated to cost over $18 billion and would take 25 years to complete.
Zebra and Quagga Mussels
Quagga mussels first arrived in the Great Lakes in 1924. The National Oceanic and Atmospheric Administration estimates that there are 437 trillion quagga mussels in Lake Michigan alone. Quagga mussels have consumed a majority of the vegetation on southern Lake Michigan bottomlands, and reduced the biomass of Lake Huron by 95%, resulting in the closure of several commercial fisheries and charters.
The quagga mussel is also a contributor to the massive algal blooms occurring on Lake Erie and in other areas of the Great Lakes. Although the mussels actually clean the water, this allows sunlight to penetrate deeper, creating perfect conditions for algae to grow and take over the ecosystem, especially combined with nutrient runoff. Beaches are now frequently closed throughout the Great Lakes because of the health risks associated with these massive blooms.
The sea lamprey entered the Great Lakes through the Welland Canal in 1921, and since then has been decimating key predator and game fish like lake trout, lake whitefish, chub, and lake herring. The species played a large role in the destruction of the Lake Superior lake trout population. The lamprey has an advantage by parasitizing these native species, who had previously faced no predators in the native Great Lakes ecosystem.
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