Harmful Algal Blooms

Information for Campground Operators and Privately-Owned Lakes and Ponds (pdf)

Information and Monitoring Data

HAB Fact Sheet


What types of health problems can people and pets experience from exposure to high numbers of Blue-Green Algae and HABs?

How to protect yourself, your family, and your pets from exposure to HABs:

How to treat people or animals that have been exposed to HAB toxins:

More about Harmful Algal Blooms

Cyanobacteria, often called blue-green algae, are bacteria that are naturally found in Ohio lakes, ponds, rivers and slow-moving streams. Although many species of algae do not produce toxins, some species of blue-green algae can cause Harmful Algal Blooms (HABs).

Several of Ohio’s inland lakes have experienced cyanobacteria blue-green algae blooms.

Depending on the general, water conditions, and other factors, neurotoxins, hepatotoxins, cytotoxins, dermatoxins and gastrointestinal toxins can be produced by cyanobacteria. These toxins are released into the water as the bacteria die. Water samples from various Ohio lakes have detected the presence of microcystin, anatoxin-a, cylindrospermin, and saxitoxin. Both humans and animals can experience illness from exposure to these toxins during recreational activities and other water uses.

Under the right water conditions, which usually occur in the warmer months, the number of these blue-green algae can dramatically increase, or “bloom.” Scientists do not fully understand what causes the same species of algae to trigger toxin production during one bloom and not produce toxin during the next.

Some cyanobacterial blooms can look like foam, scum, or mats on the surface of freshwater lakes and ponds. The blooms can be blue, bright green, brown, or red and may look like paint floating on the water. Some blooms may not affect the appearance of the water.

Humans and pets can get sick from exposure to cyanobacteria toxins. The development of illness will depend on the type of cyanobacteria, the levels in the water and the type of contact an individual has had with this “algae.”

The World Health Organization set guidelines for microcystin toxin (a toxin produced by cyanobacteria) at 1 part per billion (ppb) in drinking water and 20 ppb for recreational waters. Currently, no similar guidance exists for the other toxins produced by cyanobacteria.

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