Flint Lake, located on the north side of Valparaiso, Indiana, is facing serious challenges from invasive aquatic weeds—particularly Eurasian milfoil. This fast-spreading species is contributing to significant fish habitat destruction. The infestation has become so severe that during a Department of Natural Resources (DNR) fish survey, biologists had to repeatedly stop to clear plant material from their boat propellers, according to biologist Courtney Weldon.
While removing invasive species like Eurasian milfoil can improve water quality and support a healthier lake ecosystem, the current reliance on aquatic herbicides presents its own set of problems. Herbicides don’t actually remove the plant biomass from the lake; instead, they kill the plants in place, leaving the decaying material to sink and rot. This process contributes to lake oxygen depletion, creating conditions that can suffocate fish and other aquatic life.
Complicating matters further, Eurasian milfoil is becoming increasingly herbicide-resistant, making chemical treatments less effective over time. Even worse, non-selective herbicides can damage or kill native aquatic plants that are crucial for maintaining balanced ecosystems and protecting fish populations.