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.

Report Algae Bloom

If you see an algae bloom in a lake or river in Madison County, avoid it and report it to Madison County Health Department at 315-366-2526 or email the New York State Department of Environmental Conservation.


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.