Blue-Green Algae

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Harmful Algal Blooms (HABs) Interactive Location Map

Interested in seeing what local bodies of water have HABs? The link below displays the location of HABs in New York State. Each blue dot with black outline dot represents a HAB reported in the past 2 weeks. There may be other waterbodies with HABs that have not been reported to DEC.

Click the link to learn more: Click here

(Updated 6/23/2020) 

Algae Dog

Attention Pet Owners!

Harmful algal blooms (HABs) can make animals very sick and could even kill your pet! Don't allow pets to swim or drink in areas that appear to have blue-green algae.
Exposure to algae toxins can cause dogs to have liver failure and/or neurological problems. Signs that a dog has ingested blue-green algae include twitching, weakness, seizures, vomiting, and diarrhea. Although it is more common to see symptoms within minutes or hours, it might be days before the toxins take effect. Call your vet immediately if you notice these symptoms.

Click here to learn more: Click here 

(Updated 9/4/2019)


Water Quality Information on Canandaigua Lake

Have you seen Harmful Algal Blooms (HABS) and don't have the number to report it? What is causing the foam on Canandaigua Lake? Find the answers to these questions by clicking the link for the Canandaigua Lake, Water Quality Update for September 17, 2019. 

To answer all your Canandaigua Water Quality Questions: Click here

(Updated 9/17/2019)

For up to date information on algae blooms in NYS lakes click here:
NYS Dept of Health:Blue Green Algae

Go Jump in the Lake, but...

Look before You Leap!

Blue-green algae (cyanobacteria) are naturally-occurring bacteria that live in ponds, lakes, rivers and streams across our state. Sunny weather causes them to grow. Blue-green algae thrive in shallow, undisturbed, surface waters. Large amounts of algae can discolor water and form floating scums on the surface. Water may look greenish, yellowish or even brownish red. Severely affected water may take on a paint-like appearance.


Some types of blue-green algae produce toxins (poisons) that are dangerous to animals and humans. Contact with toxins can cause skin, eye, nose, and throat irritation. If swallowed, they can harm the liver and nervous system of both humans and animals. Humans should avoid exposure to blue-green algae and should protect their pets and livestock from exposure, as well. Some animals have died after ingesting large amounts of floating scum.

Symptoms of Toxin Exposure

  • Skin, eye, nose, and throat irritation
  • Allergic reactions
  • Breathing difficulties
If you develop symptoms of toxin exposure after swimming, bathing, or showering stop using the water and seek medical attention.

Using Lakes Safely

  • Swimming, bathing and showering with water that is not visibly affected is usually considered safe.
  • Avoid contact with water that appears discolored or has surface scums. Prevent pets and livestock from contact, as well. If contact occurs, wash area with soap and clean water.
  • Do not drink surface water, regardless of whether algae is present. In addition to algal toxins, surface water can harbor other types of organisms that make people sick.
  • If you use surface water in your home, find out if blue-green algae have been reported in your water source.
  • If you wash dishes with surface water, wearing gloves and rinsing dishes with bottled water may lessen exposure risk.
  • Blue-green algal toxins cannot be detected by the water’s taste or odor.
  • Home treatments (boiling, filtering, UV light, and chlorine) do not deactivate toxins.

Health Department's Role

In addition to providing education, Ontario County Public Health works with the NYSDOH, DEC, and town authorities to inform the public if blue-green algae is detected in bodies of water in our county. This summer check our website and Facebook pages for updates about lakes and beaches. The health department also works closely with local media to keep the public informed about water quality.

Water Testing

Testing lake water may not be the best way to determine if water is safe on a particular day. In the days between sample collection and testing, an algal bloom can dissolve or be carried to another part of the lake by currents or wind. It is more effective to simply look for blooms and scums before using or entering the water. Humans should avoid contact (swimming, drinking, bathing, etc.) with water that appears discolored or has surface scums.

(Updated 4/24/2019)
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