Ohio Algae Information for Recreational Waters

Algal blooms have become more noticeable in Ohio’s lakes, streams and rivers during the last few years.

 As a precautionary response to COVID-19, Ohio EPA is currently operating with most staff working remotely. If you are working with our staff on a current project and you know the name of the employee you are working with, email them at firstname.lastname@epa.ohio.gov or call them directly. The Agency website has contact information for every district, division, and office. To report a spill or environmental emergency, contact the spill hotline (800) 282-9378 or (614) 224-0946. This number should only be used for emergencies. For all other calls, please contact Ohio EPA’s main phone line at (614) 644-3020 or the main line for the division or office you are trying to reach.

After March 23, our district offices and Central Office will be temporarily closed and will have increasingly limited ability to receive deliveries, plans, etc. All entities are encouraged to submit plans, permit applications, etc., electronically where there are existing avenues to do so, such as the eBusiness Center (eBiz). Please refer to the list of available services on the main eBiz webpage. We encourage you to make use of all that apply, even if you have not used eBiz in the past. Plans under 25 MB can be emailed. For large plans over 25 MB, entities should work with the reviewer/division to upload via LiquidFiles. Directions for submitting docs via LiquidFiles is available on YouTube. We apologize for the inconvenience and thank you in advance for your understanding. If you wish to send hard copies of documents to any of Ohio EPA’s district offices, the best method to ensure we receive these documents is to send them via U.S. Mail. Since all offices are closed, deliveries outside of U.S. Mail (FedEx, UPS) will likely be returned because the offices are closed and deliveries cannot be made.

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. We hope the information here 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 advisory for state park beaches has two levels.

Be alert for these advisories and changing water conditions.


General Signs

These signs will be posted at state park beaches and boat ramps. The white sign describes what a harmful algal bloom looks like and advises that people be on the alert and avoid them.

Download General Sign (PDF)

Recreational Public Health Advisory

An orange Recreational Public Health Advisory will be added to the white sign when a HAB is visually confirmed and/or when cyanotoxin toxin levels are equal to or exceed Recreational Public Health Advisory threshold. It indicates that an algal bloom has been detected, and that swimming and wading are not recommended for children, pregnant or nursing women, those with certain medical conditions and pets.

Download Recreational Public Health Advisory Sign (PDF)


Elevated Recreational Public Health Advisory

A red sign will be added to the white sign when HAB toxin levels are equal to or exceed the Elevated Recreational Public Health Advisory threshold. It advises that algal toxins at unsafe levels have been detected and to avoid all contact with the water.

Download Elevated Recreational Public Health Advisory Sign (PDF)

    Drinking Water Advisory

    If microcystin, anatoxin-a, cylindrospermopsin or saxitoxin is found above drinking water thresholds in the finished water of a public water system, the water system will public notice a drinking water advisory.

    Depending on the toxin level detected, either a do not drink or do not use warning will be issued. The public water system may end a public notice when algal toxin levels are below the drinking water thresholds in two consecutive samples collected at least 24 hours apart.

    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. Click here for images of HABs.

    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.

    What should I do if my pets or livestock become ill?

    Time can be critical — some exposures to HABs can produce life-threatening illnesses within a half-hour of ingestion, while other symptoms may take several hours to days to emerge. Contact your veterinarian immediately if your pet or livestock become ill. Indicate that your animal was in water containing an algal bloom and was drinking the water; eating algae off the beach; or licking algae off its fur/skin while grooming.

    What are the symptoms?

    According to Dr. Michael Carlson, diagnostic toxicologist with the UNL Veterinary Diagnostic Center at the University of Nebraska, liver toxins such as microcystin can cause lethargy, vomiting, diarrhea, weakness, pale mucous membranes and death. Animals suffering from the nerve toxin, anatoxin-a poisoning, can experience muscle tremors, rigidity, lethargy, respiratory distress, convulsions and death. Victims of the nerve toxin anatoxin-a(s) poisoning can experience salivation, urination, defecation, secretion of tears, tremors, shortness of breath, convulsions and death.

    How can I keep my pets and livestock safe?

    • Keep pets and livestock out of water with algal blooms. “When in doubt, keep them out.”
    • Keep livestock fenced out of water with algae blooms.
    • If your pets do enter the water, be sure to rinse them off well so they do not lick algae
      off their fur or skin as toxins may still be present.
    • Do not let your pet eat algae off the beach as toxins may still be present.

    Where should I report HAB-related illnesses?

    After immediate treatment, report illnesses to the State Veterinarian at (614) 728-6220 or (800) 300-9755.

    Helpful Links

    Report HABs in Ohio Waters

    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.

    HABs - A Guide to Collecting Grab and Composite Cyanotoxin Samples
    This video demonstrates cyanotoxin sample collection procedures at beaches for both grab and composite samples.



    The Ohio Department of Health (ODH) samples selected public beaches along Lake Erie for E. coli bacteria. When the amount of bacteria in the water exceeds state standards, beaches are posted with signs that advise against swimming. ODH's site will allow you to view current sample results to determine the risks for swimming.

    For Physicians

    ODH has numerous fact sheets and resources, including the Blue-Green Algae/Cyanobacteria Harmful Algal Bloom (HABs) Health Assessment fact sheet, available for physicians on their Harmful Algal Bloom (HAB) Cyanotoxins webpage.

    Related Links

    to learn more about collecting grab and composite cyanotoxin samples from beaches.

    to learn more about harmful algal blooms and state park beach advisories.

    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 online bloom report form or the 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. The directory of local health districts can be found here. Local health districts should complete forms for reports of human illnesses associated with either recreational or public water system exposure to HABs toxins, which are available here.

    Algal Toxin Results

    From Lake Erie, Ohio state park beaches and public water supplies:
    Excel file

    Get to the
    Right Person Faster


    For more information about harmful algal blooms, contact:
    Public Interest Center, Ohio EPA
    (614) 644-2160