In July 2019, a severe bloom of blue-green algae began spreading across the western half of Lake Erie. The dominant organism—a Microcystis cyanobacteria—produces the toxin microcystin, which can cause liver damage, numbness, dizziness, and vomiting. On July 29, the National Oceanic Atmospheric Administration (NOAA) reported unsafe toxin concentrations in Lake Erie and have since advised people (and their animals) to stay away from areas where scum is forming on the water surface.
A recently released image shows the bloom on July 30, 2019, as observed by the Operational Land Imager on the Landsat 8 satellite. Green patches show where the bloom was most dense and where toxicity levels were unsafe for recreational activities. Around the time of this image, the bloom covered about 300 square miles of Lake Erie’s surface, according to news reports; by August 13, the algae had spread across 620 square miles, eight times the size of Cleveland.
While blooms in Lake Erie are a regular occurrence in the summer, NOAA researchers forecasted that 2019 could bring some of the most abundant blooms in recent years.
Bloom conditions this year were influenced by calm winds and rainfall. Calm winds in July allowed algal toxins to accumulate at the surface (instead of being dispersed). Strong winds in August have since mixed some surface algae to deeper depths. Heavy rains carry excess nutrients (often fertilizer) from farms into the lake. However, such nutrient runoff may have been less than anticipated this year because heavy spring rains and flooding prevented many farmers from planting crops.
If you see an algal bloom, stay out of the water and keep your animals out of the water. You cannot tell if an algal bloom is harmful by looking at it, so it is best to be careful and avoid contact. If you or your animals do go in water that has an algal bloom, wash yourself or your animals off immediately afterwards with tap water. Do not let your animals lick their fur until you wash them off with tap water.
When visiting lakes, rivers, or beaches, check your local water conditions, and follow any advice posted by your state or local environmental health department online or near the water. If you have concerns about the appearance, smell, or taste of the water, stay out of the water and contact your local park authority, environmental authority, or health department.
If you have been notified of a harmful algal bloom in a local water body or in your public drinking water supply, follow local or state guidance to reduce your risk.