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Harmful algal blooms
Water Shores with Harmful Algae

Harmful algal blooms

When in doubt, stay out. Learn what HABs can look like and how to safely enjoy Ohio's waterways.

Although most blooms are green algae and not harmful, there are some that are actually a type of cyanobacteria that have the ability to produce toxins – called harmful algal blooms (HABs).

Remember, you can still boat, fish and recreate in Ohio's lakes, streams and rivers. Just be aware that HABs exist. WHEN IN DOUBT, STAY OUT!

The Ohio Environmental Protection Agency hopes the information on their website will give you a better idea of what HABs can look like and provide you with the information you need to safely enjoy Ohio's waterways. The Weekly Update includes HAB monitoring news and recreational advisories/reports.

HAB Basics

What is a harmful algal bloom?

A harmful algal bloom (HAB) is a large growth of bacteria that can produce toxins. These toxins may affect the liver, nervous system and/or skin.

What causes HABs to form?

Some factors that can contribute to HABs include sunlight; low-water or low-flow conditions; calm water; warmer temperatures; and excess nutrients (phosphorus or nitrogen). The primary sources of nutrient pollution are runoff of fertilizers, animal manure, sewage treatment plant discharges, storm water runoff, car and power plant emissions and failing septic tanks. The State of Ohio is currently working on a statewide nutrient reduction strategy that will document ongoing nutrient reduction activities and identify areas where more work is needed.

How dangerous are HABs?

If you touch HABs, swallow water with HAB toxins or breathe in water droplets, you could get a rash, have an allergic reaction, get a stomach ache, or feel dizzy or light-headed. HABs also are toxic to pets.

Always look for HABs before going in the water. Check for HAB advisories. Ask the park manager if there has been a recent HAB because colorless toxins can still be in water.

How will I know if there is a HAB?

HABs have different colors and looks. Some colors are green, blue-green, brown, black, white, purple, red and black. They can look like film, crust or puff balls at the surface. They also may look like grass clippings or dots in the water. Some HABs look like spilled paint, pea soup, foam, wool, streaks or green cottage cheese curd.

What should I do if I see a HAB?

  • Stay out of water that may have a HAB.
  • Do not let your children or pets play in HAB debris on the shore.
  • After swimming or wading in lake water, even where no HABs are visible, rinse off with fresh water as soon as possible.
  • Never swallow any lake or river water, whether you see HABs or not.
  • Do not let pets lick HAB material from their fur or eat HAB material.
  • Do not drink or cook with lake water.
  • See a doctor if you or your children might be ill from HAB toxins. If your pet appears ill, contact your veterinarian.
  • Report the bloom to Ohio EPA by completing the Bloom Report Web form or paper form and emailing it to HABmailbox@epa.ohio.gov.

What about fishing and other activities?

If you plan to eat the fish you catch, remove the guts and liver, and rinse fillets in tap water before eating. Other activities near the water such as camping, picnicking, biking and hiking are safe. If you are picnicking, wash your hands before eating if you have had contact with lake water or shore debris.

Report a bloom or illness

If you see surface scum or something that looks like cyanobacteria at Ohio’s rivers, lakes, or public swimming beaches, report it to Ohio EPA by completing the Bloom Report Web form or paper form and emailing it to HABmailbox@epa.ohio.gov.

Individuals who are concerned that they may be experiencing HABs illness symptoms after exposure to contaminated water should contact their healthcare provider. Healthcare providers who rule out other potential causes of the symptoms and suspect a HABs illness should notify their local health district epidemiologist. Local health districts should complete forms for reports of human illnesses associated with either recreational or public water system exposure to HABs toxins.