Large-Scale Blue-Green Algae Bloom in Lake Erie

Due to the combined effects of persistent high temperatures and agricultural nonpoint source pollution, the blue-green algae bloom in the western part of Lake Erie has expanded rapidly, covering an area of 812 square kilometers—the largest such bloom for this time of year in the past three years. Test results show that microcystin concentrations in some areas have approached the drinking water safety warning threshold. Fertilizer runoff from surrounding agricultural areas is the primary cause of the blue-green algae bloom. While Lake Erie experiences varying degrees of blue-green algae pollution every summer, extreme heat waves are causing the scale and duration of these events to worsen year by year.