Ecology
Invasive Species
Non-native organisms that spread aggressively in lake ecosystems, outcompeting native species and often degrading water quality and habitat.
Invasive Species is a term from limnology — the scientific study of inland waters. The detailed explanation below covers the definition, why the concept matters to lake water-quality interpretation, and how it intersects with the LakeGrade rubric. Reading Invasive Species alongside the LakeGrade rubric helps make the rubric's structure intuitive — each grading parameter maps directly onto an established limnological concept.
The per-lake pages on LakeQuality always show the specific Invasive Species value for that lake, so you can move from the general concept to the specific lake without leaving the site.
What It Means for Your Lake
Invasive species are non-native organisms that have been introduced to lake ecosystems where they lack natural predators and competitors, allowing them to spread rapidly and cause ecological and economic harm. In Minnesota and Wisconsin, aquatic invasive species (AIS) are one of the most significant threats to lake health and are managed by both states under aggressive prevention and control programs. The most consequential aquatic invasive species in the region include zebra mussels and their larger relatives spiny water fleas (Bythotrephes), Eurasian watermilfoil, curly-leaf pondweed, starry stonewort, and common carp. Each species impacts lakes differently: zebra mussels filter vast quantities of water, increasing clarity but shifting nutrients to nearshore areas and promoting attached algae growth; Eurasian watermilfoil forms dense surface mats that impede boating, swimming, and native plant growth; and common carp uproot aquatic vegetation and stir up bottom sediments, dramatically increasing turbidity. Minnesota law requires boaters to remove all plants and drain all water from boats, trailers, and equipment before leaving any water body. Wisconsin has similar regulations and has invested heavily in boat inspection programs at public accesses. Despite prevention efforts, the number of lakes with confirmed invasive species continues to grow, Minnesota DNR tracks over 700 infested waters, and Wisconsin DNR has documented invasives in hundreds of lakes. Once established, most aquatic invasive species cannot be eradicated, making prevention the most cost-effective management strategy.
Frequently Asked Questions
What is invasive species?
Non-native organisms that spread aggressively in lake ecosystems, outcompeting native species and often degrading water quality and habitat.
Why does invasive species matter for lake health?
Invasive species are non-native organisms that have been introduced to lake ecosystems where they lack natural predators and competitors, allowing them to spread rapidly and cause ecological and economic harm. In Minnesota and Wisconsin, aquatic invasive species (AIS) are one of the most significant...
Related Terms
Zebra Mussels
Small, striped freshwater mussels native to Eastern Europe that attach to hard surfaces in lakes, filter large volumes of water, and alter lake ecosystems.
Eurasian Watermilfoil
An aggressive invasive aquatic plant that forms dense surface mats, displaces native vegetation, and impairs swimming, boating, and fishing.
Water Quality Monitoring
The systematic collection and analysis of water samples and measurements to track lake health over time and detect changes in water quality.
Source: EPA National Aquatic Resource Surveys, 2026.