Harmful Algal Blooms

Microscopic organisms that live in aquatic environments, algae contain chlorophyll and produce energy from sunlight through the process of photosynthesis. Algae are naturally occurring, and a key component of any aquatic ecosystem—but excessive algal growth leads to challenges with water quality.

Under conditions of warm, slow-moving water rich in nutrients (found commonly in Iowa during the summer and early fall)—algae reproduce rapidly, or “bloom.” Algal blooms are visually recognizable by their kelly green to blue-green color, and water that appears to have a cloudy or paint-like consistency. Some algal blooms also appear as a scummy or mossy layer on the surface of the water body, especially near shorelines.

Blue-green algae, also known as cyanobacteria, are especially troublesome. Their blooms are highly dynamic and are of particular concern due to their potential to release harmful cyanotoxins such as microcystin.

When people play or swim during an algal bloom, they may ingest water containing this microcystin toxin, which can lead to nausea, vomiting, diarrhea, cough, runny eyes and nose, sore throat, skin rashes, and in severe cases, liver failure. Pets that drink contaminated water, or even lick themselves after being in the water, can be exposed to microcystin toxins that can cause illness or death. Harmful algal blooms and elevated microcystin toxin levels are an emerging concern for cities such as Des Moines, where the drinking water is supplied by rivers (vs. underground wells).

Video Resources

What’s In Your Water?—The Beach

Additional Resources

Statewide Beach Monitoring – Iowa Department of Natural Resources

A Closer Look: Harmful Algal Blooms – Iowa State University | Conservation Learning Group