Harmful Algal Blooms (HABs) Background
Harmful algal blooms (HABs) in freshwater (lakes, ponds, rivers, and streams) generally consist of visible patches of cyanobacteria, also called blue-green algae. Cyanobacteria are naturally present in low numbers in most aquatic (freshwater and/or marine) systems. Under certain conditions, including adequate nutrient (e.g., phosphorus) availability, warm temperatures, and calm winds, cyanobacteria may multiply rapidly and form blooms that are visible on the surface of the affected waterbody. Several types of cyanobacteria can produce toxins and other harmful compounds that can pose health risks to people and animals through ingestion, skin contact, or inhalation.
DEC has routinely documented the occurrence of HABs in New York State since 2012 and has produced resources to inform the public of the occurrence of HABs and strategies to avoid them. In addition, through data collection, development of lake and river surveillance programs, and research, the DEC is working to identify the primary factors triggering HAB events and facilitate decision-making to minimize the frequency, intensity, and duration of HABs as well as the effects that HABs have on both people and aquatic life which rely on clean water.
Before you go in the water, check which 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 which waterbodies have had blooms in the past. For additional information, please see the DEC Program Guide (PDF, updated in 2020) or sign up for weekly HAB notifications through DEC Making Waves email listserv.
The NYS Office of Parks and Recreation, County officials or local Department of Health has the authority to close swimming beaches. Beach operators close beaches as needed to assure public health and safety. This can happen under a number of circumstances, including when excessive algal blooms are detected. DEC does not have the authority to close a lake in the event of a bloom, but can close beaches that are operated by DEC (limited to a small number of beaches within the Adirondack and Catskill Parks).
Know it, Avoid it, Report 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.
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 are likely triggered by a combination of water and environmental conditions such as:
- excess nutrients (phosphorus and nitrogen);
- lots of sunlight;
- low-water or low-flow conditions;
- calm water; and
- warm temperatures.
Depending on the weather and the characteristics of the lake, HABs may be short-lived (appearing and disappearing in hours) or long-lived (persisting for several weeks or more).
- 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 you suspect that you have seen a HAB, please report the HAB to DEC. Fill out and submit a Suspicious Algal Bloom Report Form.
- If possible, attach digital photos (close-up and landscape to show extent and location) of the suspected HAB in the web form.
- Email [email protected] if you are not able to complete the form.
- Please report any health symptoms to NYS Health Department at [email protected] and your local health department.