Harmful Algal Blooms (HABs)

A harmful algal bloom is the excess growth of cyanobacteria (more commonly called blue-green algae) that causes water quality problems, including sometimes the production of toxins. The most common harmful chemical found in New York algal blooms is microcystin. 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).

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 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.

Never swim, fish, boat, wade or eat fish caught in water with blooms.

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.

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.

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.

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.

The Health Department is working closely with operators of bathing beaches. Beaches may be closed due to the presence of HABs. Please contact the facility operator directly for more information.

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

To learn more about HABs, visit: www.health.ny.gov/environmental/water/drinking/bluegreenalgae/ and Tompkins County DOH, which can be followed at Facebook.com/TompkinsPublicHealth.

Information on this page adapted from NYSDECNYSDOH and Tompkins County DOH materials


Sharon Anderson
Environment Team Leader
(607) 272-2292 ext. 156

Last updated January 22, 2019