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Information about Blue-green Algae HABs for Individuals and Communities

Learn more about how to reduce you and your family's exposure to blue-green algae blooms.

Swimming concerns

Swimmers should be concerned about blue green algae blooms for a number of reasons. Some people are sensitive to exposure to the scum material associated with algae blooms, in the same way some people are more sensitive to poison ivy. Blue green algae can also release toxins that affect people through skin exposure and gastrointestinal or asthma-like symptoms, including nausea, vomiting, diarrhea, skin or throat irritation, allergic reactions or breathing difficulties. Keep in mind that some blooms do not produce these toxins, and there have been few reports of illness associated with blue green algae exposure. Swimming can also be affected by the ugly appearance and smell from algae that accumulated along the surface or shoreline, and beaches may be closed by health officials to protect swimmers.

The waterbodies listed on the notification web page are based on information from 150-200 lakes collected through DEC monitoring programs and public reports. There are more than 7000 lakes in the state and most are not routinely sampled.

If you plan on swimming outside of a regulated swimming beach, please visit DEC's swimming web page for information to help you reduce your risk for exposure to potential hazards. It is ultimately your responsibility to decide if the risks associated with swimming in a lake are acceptable.

Protect your family and pets

The best advice is that "If you see it--avoid it". Following this advice will greatly reduce the likelihood of exposure to blue green algae blooms. People and pets should avoid swimming in heavily discolored water or surface scums, and they should also not handle algae material--scums or algae covering weeds along the shoreline. Don't' let children or pets wade, drink the water or walk in beach debris, and remove them from heavily discolored water immediately. Swimming at regulated beaches will also greatly reduce the risk of exposure to these blooms, since these beaches are closely monitored for the presence of blooms.

What to do if a person has contact with a bloom

Swimmers that have been exposed to blue green algae blooms should seek medical assistance if they observe any symptoms associated with blue green algae toxins.

The symptoms of blue green algae exposure:

  • nausea, vomiting, diarrhea,
  • skin or throat irritation
  • allergic reactions or breathing difficulties

These symptoms are commonly mistaken for other gastrointestinal stress, whether from illness, food poisoning, or other health problems. Regardless of the cause of the illness, these symptoms may require medical attention. You should contact your physician, or, in the case of severe reactions, seek immediate medical attention. You should also inform your physician and the local health department if you were exposed to an algae bloom, both to help determine the proper course of treatment and to determine if others should also be notified of this potential risk.

More information about these symptoms can be found on the Department of Health Blue-green Algae web page.

What to do if an animal has contact with a bloom

The blue-green algae cells can stick to animal fur and become concentrated when the animal cleans itself. Rinse your dog, pet or livestock animal with clean water and seek veterinarian medical assistance should your pet show any signs of distress.

Blue green algae blooms may release a nerve toxin that can be very dangerous for pets, particularly dogs that frequently swim within blooms.
Symptoms of blue green algae exposure for dogs include:

  • stumbling, seizures, convulsions, paralysis
  • excessive salivation or drooling,
  • disorientation, inactivity or depression,
  • elevated heart rate, and difficulty breathing.

If you see or suspect any of these symptoms, particularly within 30 minutes to a few hours after exposure to an algae bloom, seek immediate veterinarian care.

Long-term exposure to algae liver toxins may lead to symptoms such as repeated vomiting (green liquid), diarrhea or tarry (bloody) stool, loss of appetite, anorexia, jaundice (yellowing of eye whites or gums), abdominal swelling tender to the touch, cyanosis (bluish coloration) of skin, dark urine or reduced urine output. Your veterinarian should be consulted to see if veterinarian assistance is appropriate. Any information you can provide to the veterinarian about the potential duration of algae exposure will help to determine the appropriate course of action.

New York Sea Grant published a Dogs and Harmful Algal Blooms (HABs) (809 KB, PDF) brochure. The brochure includes: descriptions of common symptoms and what to do, information about toxins and how dogs are exposed, how to reduce your dog's risk of exposure and how to report suspected blooms.

Drinking water concerns

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 could cause illness if consumed.

People not on public water supplies should not drink surface water during an algae bloom, even if it is treated, 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.

Fishing concerns

How much blue-green algae toxins accumulate in fish flesh is still being studied. There have been no reports of people becoming sick from eating fish caught during a bloom.

Some states have provided some precautionary advice about limiting consumption of fish fat, skin, and organs, and recommend rinsing cleaning filets with fresh water before cooking or freezing. The New York Freshwater Fishing Guide advises anglers to avoid eating fish caught from areas that have the thick paint-like or pea soup-like coloration characteristic of blue-green algae blooms.

Reporting a suspected 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).

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.

Help prevent blue-green algae blooms

The public and lake residents can do their part to reduce the likelihood of algae blooms to waterbodies by reducing the amount of nutrients (phosphorus and nitrogen) added. The amount of nutrients can be decreased by:

  • limiting lawn fertilization,
  • maintaining septic tanks and shoreline buffers,
  • reducing erosion and stormwater runoff, and
  • maintaining water movement.

Detailed information about these nutrient control strategies are discussed in chapters 7 and 9 in Diet for a Small Lake, a publication prepared by DEC and the New York Federation of Lake Associations to advise New Yorkers about lake management.

Many of the nutrients inputs that can cause an algae bloom are from activities and sources outside of shorefront properties. Lake community residents and lake associations should work with local and county government agencies to identify sources of nutrients and identify strategies to reduce nutrient inputs to the lake.

Does the state close lakes?

DEC does not have the authority to "close the lake" in the event of a blue green algae bloom, although they can close beaches that are operated by DEC (generally limited to a small number of beaches within the Adirondack Park).

The local Department of Health has the authority to close swimming beaches, and they work closely with beach operators and the State Office of Parks and Recreation to close beaches as needed to assure public health and safety. This can happen under a number of circumstances, including when excessive algae blooms are detected.

Lakes with blue-green algae blooms are listed on the Blue-green Algae Bloom Notices web page when DEC receives credible information about the presence of a blue green algae bloom that might adversely affect lake users.

The public can use this information to help them to make informed decisions about where and when to recreate, particularly outside of designated swimming areas. Swimmers and recreational users should remember that health and safety cannot be assured outside of designated swimming areas- for more swimming information, visit DEC's swimming web page .

Information for municipalities and lake communities

What advice should we give to protect lake community residents

The advice provided throughout the DEC HAB web pages- if you see it, avoid it- should continue to be provided to community residents and businesses using the lake for a variety of purposes. If blooms have been observed at your community's lake, community residents interested in preventing blooms and minimizing risks associated with blue green algae blooms should be encouraged to help identify and clean up the sources of nutrients that are contributing to the blooms- failing septic tanks, over fertilization, shoreline erosion, pet and wildlife waste, and stormwater runoff.

Residents are asking if the community's lake is susceptible to blooms

Some lakes are more susceptible than others to blooms, particularly along the shoreline where people swim and recreate. The DEC blue-green algae notification page and the archive page show locations in the state where blooms are occurring or have been reported in previous years.

The archive web page shows lakes have had blooms over several years or several times during the summer. Many of these lakes are more susceptible to blooms due to elevated nutrient levels, but the reasons for a bloom in any given lake can be complicated and are still not well understood. This archive list should NOT be assumed to be a list of lakes where blooms will occur. Lakes with previous blooms may suggest a higher likelihood of future blooms. Lake residents and visitors to any lake should be aware of the potential for a bloom, and should be on the lookout for any evidence of conditions shown on the algae photo gallery web page.

Should people be advised to get out of the water?

The risk for exposure while swimming is greater when blooms cover a large part of lake or when water sample results show a bloom occurring in the open water (this may indicate more extensive bloom coverage). The notification web page indicates, when known, the extent of the bloom coverage.

However, swimming or bathing with water not visibly affected by a blue-green algae bloom is not expected to cause health effects.

The advice provided throughout the DEC HAB web page- if you see it, avoid it- should continue to guide decisions by people whether they should recreate or stay out of the water. This advice is particularly important because blooms come and go, and the exact locations of blooms in all lakes throughout the state are not known.

When community residents have questions

Municipal officials can direct callers to the DEC or DOH web pages for general information about blooms, and for information about waterbodies where blooms have been reported.

Officials can also provide the links to these web pages on any information provided to town residents and local businesses, including information posted on the web pages maintained by the municipality. This is the best way to provide updated information to community residents, since the DEC HAB notification page is updated weekly during the summer and should reflect the most accurate information available about the extent and duration of the blooms.

Community residents and other lake users should continue to follow the DEC and DOH advice that "if you see it, avoid it", to minimize exposure to these blooms and to best protect lake users in locations where blooms have not been reported.

Should we post a sign at our park?

Posting signs at boat launches and parks is one way to inform people that are using the water about potential risks associated with blue green algae bloom exposure. Signs are often posted at swimming beaches to inform swimmers why a beach may be closed or to provide an alert. However, if the bloom is not visible and does not return for the rest of the summer, these signs may unnecessarily alert lake users to conditions that no longer exist. Therefore, signs should be posted where appropriate and removed when the bloom has clearly passed.

DEC's activities and programs help reduce nutrients to waterbodies

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


DEC maintains collaborative partnerships with NYS Department of Health (DOH) and NYS Office of Parks, Recreation and Historic Preservation (OPRHP) to coordinate response to blue-green harmful algal bloom concerns around the state. DEC and DOH are also conducting research projects specifically to assess blue-green algae HABs risk and to better understand the conditions that trigger blue-green algae HABs.

DEC promotes long lasting partnerships with watershed organizations and associations. For example, Finger Lakes- Lake Ontario Watershed Protection Alliance (FL-LOWPA), New York State Federation of Lake Associations (NYSFOLA), and county water quality coordinating committees (WQCC).

Funding Opportunities

DEC provides grant funding to municipalities, soil and water conservation districts, and non-profit organizations for projects that reduce polluted runoff into waterbodies, including Clean Water Act (CWA) Section 604(b), and Water Quality Improvement Project Program.