Harmful Algal Blooms (HABs)

Harmful algal blooms (HABs) are excess growth of cyanobacteria (more commonly called blue-green algae) that produces toxins. View images of harmful and non-harmful algal blooms provided by NYS Dept. of Environmental Conservation (NYSDEC). For reports of HABs so far in 2020 view the Cayuga Lake map kept by the Community Science Institute and the NYS map kept by NYS Dept. of Environmental Conservation (NYSDEC).

Microcystin is the chemical most commonly found in harmful algal blooms in New York. NYSDEC defines a “bloom with high toxin” as microcystin equal or greater than 20 ppb near the lake shore and 10 ppb in open water ( NYSDEC HABs Program Guide, p 10).

Risk to people and pets

Exposure to blue-green algae during recreational activities such as swimming, wading, and water-skiing may lead to rashes, skin, eye irritation, nausea, stomach aches, tingling in fingers and toes, or breathing difficulty. If these occur, seek medical assistance.

Livestock, pets and wild animals can be poisoned. Dogs are particularly susceptible to blue-green algae poisoning because the scum can attach to their coats and be swallowed during self-cleaning. Clinical signs of blue green algae poisoning in animals include vomiting, diarrhea, decreased appetite, weakness, seizures, and sudden death. View Dogs and HABs brochure by NYS Sea Grant and, for more extensive information, see Freshwater HABS for Animal Owners by Cornell University College of Veterinary Medicine.

Know it

It might be harmful blue-green algae if you see: strongly colored water, paint-like appearance, floating mats or scum. View these images for examples: www.dec.ny.gov

Avoid it

If you see a bloom, avoid it and wait 24 hours after the bloom is no longer visible before swimming or having contact with the water. Never swim, fish, boat, wade or eat fish caught in water with blooms.

The Health Department may close swimming areas due to the presence of HABs. Please contact the facility operator directly for information.

Pet owners should keep their pets away from water experiencing algae blooms. If animals ingest the toxins either through drinking or cleaning their fur after exposure, they can become sick quickly. Call your veterinarian if your pet comes in contact with a bloom.

If you are not on a public water supply, household water treatment such as ultraviolet (UV), boiling or chlorinating will not make your water safe for use. During a bloom, do not drink, prepare food, cook, or make ice with water from the lake or from beach wells. Never drink untreated surface water.

Visually monitor the water near your beach well daily and call Environmental Health with questions: 607-274-6688.

The Health Department works closely with public water supplies. There is no concern with public water supplies at this time.

Report it

If you see a suspicious bloom, stay out of the water and report the bloom to the NYS Department of Environmental Conservation at HABsInfo@dec.ny.gov and to our local responders athabshotline@gmail.com.  See left sidebar for details on how to effectively report.

What to do if contact occurs with blue-green algae:

Rinse thoroughly with clean water to remove algae, including dogs that may have gone in the water.

Stop using water and seek medical attention immediately if symptoms such as vomiting, nausea, diarrhea, skin, eye or throat irritation, allergic reactions or breathing difficulties occur after drinking or having contact with blooms or untreated surface water.

Report any HAB-related health symptoms to the NYS Health Department at harmfulalgae@health.ny.gov, or call TCHD Community Health Services at (607) 274-6604.

Learn more about HABs 

visit: www.health.ny.gov/environmental/water/drinking/bluegreenalgae/ and Tompkins County DOH, which can be followed at Facebook.com/TompkinsWholeHealth.

Information on this page adapted from  NYSDEC, NYSDOH and Tompkins County DOH materials

Last updated September 18, 2023