from Washtenaw County Conservation District
Harmful algal blooms (HABs) are a growing threat to water quality, human and animal health, and our local economies. In southeastern Michigan, excessive nutrient runoff — especially phosphorus — from agricultural and urban landscapes contributes to HABs in the Huron River and River Raisin watersheds, both of which drain into the Western Lake Erie Basin.
HABs occur when algae — primarily cyanobacteria or “blue-green algae” — rapidly grow in nutrient-rich freshwater. These blooms:
- Deplete oxygen in water, harming fish and aquatic life
- Produce toxins harmful to humans, pets, and livestock
- Disrupt recreation, tourism, and drinking-water supplies
- Impact downstream ecosystems, including Lake Erie
In Michigan, HABs often form during the warm summer and fall months, particularly in slow-moving or nutrient-rich waterbodies like lakes, ponds, and impoundments. Tributaries such as the Huron River and River Raisin feed into Lake Erie, meaning local nutrient runoff has regional consequences…