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Blue-Green Harmful Algal Blooms

What is a Harmful Algal Bloom (HAB)?

Most algae are harmless and are an important part of the food web. Algae are naturally present in slow moving streams, lakes, marine waters and ponds in low numbers. Certain types can become abundant and form blooms under the right conditions. Some algae can produce toxins that can be harmful to people and animals. These are collectively called harmful algal blooms (HABs).

Avoid Algae Blooms

Algae blooms most frequently occur in nutrient-rich waters, particularly during hot, calm weather.

Because it is hard to tell a harmful algae bloom from other algae blooms, we recommend avoiding contact with any floating rafts, scums, and discolored water. Find out what waterbodies have a blue-green algal bloom notice.

Spilled paint appearance of a blue-green algae bloom.
Blue-green algae blooms may have the
appearance of spilled green paint.

Freshwater Blue-green Algal Blooms

Blue-green algae, technically known as cyanobacteria, are naturally present in lakes and streams in low numbers. Blue-green algae can form HABs that discolor the water or produce floating rafts or scums on the surface of the water. These can cause health risks to people and animals when they are exposed to them.

Blue-green algae blooms can occur in freshwater lakes and ponds and can reduce the recreational value of a waterbody, due to unpleasant appearances and odors, and can cause a variety of ecological problems, such as reduced oxygen levels. They also have the potential to form harmful (toxic) blue-green algal blooms, although the factors that cause blue-green algae to produce toxins are not well understood.

Harmful blue-green algae blooms can cause health effects when people and animals come in contact with them. Symptoms can include nausea, vomiting, diarrhea, skin or throat irritation, allergic reactions or breathing difficulties. Blue-green algae can also produce toxins that affect the liver and nervous systems when water is consumed in sufficient quantities.

More information about blue-green algae and blue-green harmful algal blooms effect on lakes.

Marine Algal Blooms

Different algae can form harmful algal blooms in marine waters, producing marine blooms and a variety of biotoxin events that occur off the coast of New York and other eastern and western seaboard states.

What should I do if I see or come in contact with a blue-green algae bloom?

If you see it--avoid it

Blue-green algae blooms may have the appearance of pea soup.
Blue-green algae blooms may
have the appearance of pea soup.
  • People, pets and livestock should avoid contact with water that is discolored or has scums on the surface. Colors can include shades of green, blue-green, yellow, brown or red. If contact does occur, wash with soap and water or rinse thoroughly with clean water to remove algae.
  • Never drink untreated surface water, whether or not algae blooms are present. Untreated surface water may contain other bacteria, parasites or viruses, as well as algal toxins, that all could cause illness if consumed.
  • People not on public water supplies should not drink surface water, even if it is treated, during an algal bloom because in-home treatments such as boiling or disinfecting water with chlorine or ultraviolet (UV) or water filtration units do not protect people from blue-green algal toxins.
  • If washing dishes in untreated surface water is unavoidable, rinsing with bottled water may reduce possible residues. While we don't know if water containing low levels of blue-green algal toxins could leave residues on dishes, taking this precaution may help reduce possible exposures.
  • Stop using the water and seek medical attention if needed if symptoms such as vomiting, nausea, diarrhea, skin, eye or throat irritation, allergic reactions or breathing difficulties occur while in contact with untreated surface waters. However, swimming, bathing or showering with water not visibly affected by a blue-green algae bloom is not expected to cause health effects.

What is New York State doing?

DEC has many ongoing programs that reduce nutrient runoff into NYS waters, one of the factors related to blue-green algae HABs.

DEC Bureau of Marine Resources has an ongoing, established Marine Biotoxin Monitoring Program to search for the presence of toxin producing marine algae (Alexandrium and other species) and detect marine biotoxins in shellfish, such as clams, mussels and oysters.

DEC, the NYS Department of Health (DOH), and the NYS Office of Parks, Recreation and Historic Preservation (OPRHP) are working together to identify and respond to blue-green algae concerns. DEC and DOH are coordinating field personnel to investigate HAB reports. DEC and DOH are also conducting research to learn more about blue-green algae HABs and evaluate their risks to public health and the environment.

For more information or to report a suspected blue-green algae bloom

If you suspect that you have seen a blue-green algae bloom or you, your family, or pet has been in contact with a blue-green algae bloom please fill out and submit the Suspicious Algae Bloom Report Form (PDF, 787 KB). We recommend using Internet Explorer or Mozilla Firefox to complete and send this PDF form. If these browsers are not available, send an email to HABsInfo@dec.ny.gov with the following information: name and location of the waterbody, when the bloom was first observed, the date of any attached pictures, if the bloom is still present, and the location and extent of the bloom within the waterbody. Images showing the bloom should be attached to the email.

You are encouraged to include digital photographs as email attachments with the form (close-up, and landscape showing extent and location of bloom). If possible, please include an image from an online mapping application such as Google, Bing or Yahoo Maps, with a marker at the bloom location.

You may also contact your regional DEC office or contact:

Scott Kishbaugh, Division of Water
Phone: (518) 402-8179
Email the Division of Water

More about Blue-Green Harmful Algal Blooms: