Skip to main content
U.S. flag

An official website of the United States government

Excess nutrients flowing into Lake Erie can cause serious algal blooms

Detailed Description

Toxic Algal Bloom, Lake Eire, 2011

The green scum shown in this image is the worst algae bloom Lake Erie has experienced in decades. Such blooms were common in the lake’s shallow western basin in the 1950s and 60s. Phosphorus from farms, sewage, and industry fertilized the waters so that huge algae blooms developed year after year.

Heavy snow fell in the winter and spring, resulting in snowmelt runoff, followed by heavy rainfall in April. The rain and melting snow ran off fields, yards, and paved surfaces, carrying an array of pollutants into streams and rivers—including phosphorus and nitrogen from fertilizers. More rain and runoff resulted in more phosphorus that nutrient nourished the algae in the lake.

Though not directly toxic to fish, the bloom isn’t good for marine life. After the algae dies, bacteria break it down. The decay process consumes oxygen, so the decay of a large bloom can leave “dead zones,” low oxygen areas where fish can’t survive. If ingested, the algae can cause flu-like symptoms in people and death in pets.



Public Domain.