Harmful Algal Blooms (HABs)

Over the last 50 years, the amount of nitrogen (N) and phosphorus (P) pollution entering our nation’s waters has escalated significantly.  When excess nutrients enter streams and lakes, increases in N and P concentrations may trigger algal blooms.

Algae are a natural component of the aquatic food chain and are typically not harmful to people. However, some algal species, known as Harmful Algal Blooms (HABs), may cause harm through the production of toxins.  HABs can cause illness or irritation – sometimes even death – in pets, livestock, and humans.  Most HABs are caused by planktonic bacteria called cyanobacteria, which are commonly known as “blue-green algae.”  Cyanobacteria often float to form scums on or near the surface, forming colonies that often look like bright green paint.

Not all algal blooms are HABs and cyanobacteria should not be confused with small harmless aquatic plants called duckweeds or other true algae.

Factors that contribute to HABs include an overabundance of nutrients, sunlight, low water, calm water, warmer temperatures, and low salinity.  Nutrients that contribute to HABs and other algal blooms come from many sources, including agriculture, lawn fertilizers, wastewater treatment plants, sewer overflows and leaking septic systems.

HABs can occur almost anywhere there is water: lakes, ponds, stormwater retention basins, rivers, streams or reservoirs.  HABs can cause taste and odor problems in drinking waters, pollute beaches with scum, reduce oxygen levels for fish and other animals, causing processing problems for public water supplies, and may generate toxic chemicals.

The Ohio EPA, Ohio Department of Health and Ohio Department of Natural Resources are monitoring HABs across the state and working to educate local communities.  The State issues advisories when toxins released by cyanobacteria are detected and exceed health standards for recreational use.  People and pets are advised to minimize contact with and avoid ingestion of the lake water.

For more information, visit Ohio EPA’s Harmful Algal Bloom page.