Algae Blooms & Health

Harmful algal blooms result from excessive growths of certain type of bacteria. They can produce toxins that can make people and animals sick.

Algae blooms can cause discolored water, floating scums, and unpleasant odors in a lake or river. Algae blooms, sometimes called blue-green algal blooms, commonly occur in nutrient-rich, shallow, stagnant surface water. Blooms occur mostly during hot, sunny, and calm weather. The color of harmful algae blooms can vary. Colors can include shades of green, blue-green, yellow, brown, red, or white. You can’t tell by just looking at an algae bloom if it has harmful toxins.

Be Aware for Harmful Algal Blooms (HABs)

Algae and harmful algae blooms may occur at bathing beaches. 

Look for signs at beaches. If a beach is closed due to an algae bloom, do not swim in the water. A beach may reopen once a bloom has cleared for at least 24 hours and bathing water sample results are below the level of concern.

Avoid it.

  • 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.

View locations of freshwater HABs in New York State. 

  • Each blue dot with black outline dot represents a HAB reported in the past 2 weeks.
    • Blue icon with black halo: Current HABs have been reported through DEC's reporting system within the last two weeks.

      Blue icon without black halo: Archived HABs have been reported through DEC's reporting system within the current season.

  • There may be other waterbodies with HABs that have not been reported to DEC.

Report it.

Exposure

See a healthcare provider if you, your family, or your animals have symptoms that may be related to an algae bloom exposure.

In the event of a harmful algae bloom, swimming areas may be closed to protect public health. Pay attention to official temporary beach closures, advisory signs, press releases, and websites. Never swim at beaches that are closed and follow blue-green algae advice.

Don't get sick from algae blooms:

  • Avoid water with floating scum or that is strongly colored. Don’t swim, bathe, wash, fish, or in areas with discolored water.
  • If you come into contact with an algae bloom, immediately wash with soap and water. Rinse well with clean water.
  • If you are not on a public water supply and use surface water, do not drink it or use it for cooking, even if it is treated. During an algae bloom, boiling or disinfecting water with chlorine or ultraviolet (UV) or water filtration units do not protect people from toxins that may be present in blue-green algae.