Ecology

Invasive Species

Non-native organisms that spread aggressively in lake ecosystems, outcompeting native species and often degrading water quality and habitat.

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