How does eutrophication change lakes?
Eutrophication is excessive algal and plant production caused by high inputs of nutrients such as nitrogen and phosphorus.
Formation process and geographic mechanism
Fertilizer runoff, sewage, livestock and urban surfaces carry nutrients. Blooms make water turbid and shade bottom plants. Bacterial decay of dead material consumes oxygen and can create hypoxia in stratified bottom waters. Some cyanobacteria produce toxins, but not every green water body is toxic without testing.
Spatial outcomes, measurement and management
Removing surface algae is not a lasting solution while external inputs continue. Wastewater treatment, farm nutrient management, buffer strips and erosion control reduce loading. Phosphorus stored in sediments can return to the water for years and delay recovery. Basin-scale source budgets accompany long-term oxygen and chlorophyll monitoring.