English: Lake Erie sits on the boundary of the United States and Canada, extending 241 miles (388 km) in length and only 57 (92 km) wide. In the United States, four states line up on the shoreline – from east to west these are New York, Pennsylvania, Ohio, and Michigan.

As the waters warm each spring conditions become ripe for growth of algae, especially in the west end of the lake. The worst blooms tend to occur in years with heavy spring rains and excess winter snow and ice runoff. Runoff from lakes and streams can carry heavy loads of phosphorous, nitrogen and other fertilizers into the lake. High quantities of nutrients may promote excessive blooms of a number of types of algae, including what is known as HABs – or harmful algal blooms. Such blooms produce a type of toxin that is harmful to humans, marine mammals, birds, fish, and even shellfish.

HABs are reported in Lake Erie frequently enough that the National Oceanic and Atmospheric Association (NOAA) provides a weekly bulletin to advise of the status of such blooms. On June 29, NOAA reported that two types of plant-like organisms associated with toxins were blooming in Lake Erie. Cyanobacteria was present in low concentrations, including along Sandusky Bay and extending outside the bas west along the Ohio coast. Microcystis was present in the Maumee Bay area of the western basin. While toxin concentration was below recreational thresholds throughout the bloom extent, NOAA warned, “Keep pets and yourself out of the water where scum is forming”.

On June 29, 2018, the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Aqua satellite acquired a true-color image of Lake Erie. The swirling discoloration in the western end of the lake represents a large bloom of algae.