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Harmful Algal Blooms (HABs)

A new DEC Harmful Algal Bloom brochure (PDF, 415 KB) and Harmful Algal Bloom Program Guide (PDF, 1.8 MB) are now available.

What are Harmful Algal Blooms (HABs)?

Most algae are harmless and are an important part of the food web. Certain types of algae can grow quickly and form blooms, which can cover all or portions of a lake. Even large blooms are not necessarily harmful. However some species of algae can produce toxins that can be harmful to people and animals. Blooms of algal species that can produce toxins are referred to as harmful algal blooms (HABs). HABs usually occur in nutrient-rich waters, particularly during hot, calm weather.

Keep reading to learn what to do if you spot a bloom. Click on the links below for more detailed information.

AVOID it!

Because it is hard to tell a HAB from non-harmful algal blooms, it is best to avoid swimming, boating, otherwise recreating in, or drinking water with a bloom.

Before you go in the water, find out what waterbodies have blooms or have had them in the past. DEC maintains a HABs Notifications page of waterbodies that currently have blooms. Please note that if a waterbody is not listed, it does not mean that it does not have a bloom. It may have one that was not reported. Find out what waterbodies have had blooms in the past on the HABs Archive page.

Spilled paint appearance of an algal bloom.
Algal blooms may have the
appearance of spilled green paint.
  • People, pets and livestock should avoid contact with any floating mats, scums, or discolored water. Colors can include shades of green, blue-green, yellow, brown or red.
  • Never drink, prepare food, cook or make ice with untreated surface water, whether or not algae blooms are present. In addition to toxins, untreated surface water may contain bacteria, parasites or viruses that could cause illness if consumed.
  • People not on public water supplies should not drink surface water during an algal bloom, even if it is treated, because in-home treatments such as boiling, disinfecting water with chlorine or ultraviolet (UV), and water filtration units do not protect people from HABs toxins.

If contact occurs:

  • Rinse thoroughly with clean water to remove algae
  • 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.

Be prepared:

Before you go in the water, find out what waterbodies have blooms or have had them in the past. DEC's HABs Notifications page of waterbodies that currently have blooms. Please note that if a waterbody is not listed, it does not mean that it does not have a bloom. It may have one that was not reported. You can find out what waterbodies have had blooms in the past on the HABs Archive page.

REPORT it!

  • HABs may have the appearance of pea soup.
    HABs may have the appearance of pea soup.
    If you suspect that you have seen a HAB, please report the bloom to the DEC. Fill out and submit a Suspicious Algal Bloom Report Form (PDF, 764 KB). Email the completed form and, if possible, attach digital photos (close-up and landscape to show extent and location) of the suspected bloom to HABsInfo@dec.ny.gov.
  • Please report any health symptoms to NYS Health Department at harmfulalgae@health.ny.gov and your local health department (link leaves DEC website).

Marine Algal Blooms

HABs can form in marine waters, producing marine blooms and a variety of biotoxin events that occur off the coast of New York and other eastern and coastal states. The DEC Bureau of Marine Resources has a Marine Biotoxin Monitoring Program to search for the presence of toxin-producing marine algae (Alexandrium and others) and to detect marine biotoxins in shellfish, such as clams, mussels and oysters.


More about Harmful Algal Blooms (HABs):