Bulletin E3544
Harmful Algal Blooms in Western Lake Erie
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March 26, 2026 - Subhasis Giri, Michigan State University
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EmailLake Erie is the smallest and shallowest of the five Great Lakes, and it is divided into three parts, including the shallow western basin, the flatter central basin, and the deep eastern basin. The delineation of the watershed draining to the western basin differs among studies; here, I consider the tributaries that directly empty into the western basin, stretching from the River Raisin to the Maumee River. These lands that drain directly into the western basin are mostly agricultural, with corn and soybeans as dominant crops. They include major urban centers such as Toledo, Ohio; Monroe, Michigan; and Fort Wayne, Indiana. Rainfall and snowmelt carry nutrients like phosphorus and nitrogen from farm fields and cities into Lake Erie through these rivers (Reutter, 2019). These nutrients are considered nonpoint source pollution, meaning we cannot pinpoint precisely where the pollution comes from. While nutrients are essential for aquatic life, too much of them lead to excessive algae growth.
Algal blooms occur when algae grow rapidly and form thick, green scums on the water’s surface. Some types of algae, especially cyanobacteria (commonly called blue-green algae), can release harmful toxins known as cyanotoxins. These toxins can harm fish and other aquatic animals and may cause liver, neurological, and respiratory problems in humans and other animals (Weigle, 2020; Michalak et al., 2013). Toxic algal blooms are also referred to as harmful algal blooms (HABs).
Protecting the health of Lake Erie requires keeping nutrients on the land and out of the water. Reducing nutrient runoff from farms and cities not only helps control HABs but also supports clean, safe, and sustainable water for communities and ecosystems across the Great Lakes region for now and future generations.
