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Harmful Algal Blooms (HABs) Additional Information

Learn more about how to reduce you and your family's exposure to harmful algal blooms:

Swimming Concerns

Swimmers should be concerned about HABs in any lake in which they are considering swimming (check the HABs Notifications page to see if your lake is listed). The risk for exposure while swimming is greater when blooms cover a large part of a lake or when water sample results show a bloom is present in the open water (this may indicate more extensive bloom coverage). The Notifications page indicates, when known, the extent of the bloom coverage.

People vary in their sensitivity to HABs exposure, in the same way some people are more sensitive to poison ivy. Cyanobacteria can release toxins and other harmful compounds that affect people through skin exposure or ingestion. Gastrointestinal symptoms including nausea, vomiting, and diarrhea are possible. Skin or throat irritation, allergic reactions or asthma-like breathing difficulties are also symptoms of exposure.

If you think you may have been exposed to a HAB and are experiencing symptoms, contact your physician or, in the case of severe reactions, seek immediate medical attention. You should inform your physician and your local health department if you were exposed to an algal 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 webpage (leaves DEC website). Swimming at regulated beaches will greatly reduce your risk of exposure to HABs, since beaches are closely monitored for the presence of blooms. Beach closures by health officials are conducted to protect swimmers.

If you plan on swimming outside of a regulated swimming beach, please visit the DEC 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. People and pets should avoid swimming in heavily discolored water or surface scums, and should not handle algae material. Don't let children or pets wade, drink the water, or walk in beach debris if you suspect an algae bloom is present. The best advice is "If you see it, avoid it". Following this advice will greatly reduce the likelihood of exposure to HABs.

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 cyanotoxins 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, disinfecting water with chlorine or ultraviolet (UV), and water filtration units do not protect people from HABs or toxins. If washing dishes in untreated surface water is unavoidable, rinse with bottled water to reduce possible residues. While we don't know if water containing low levels of HABs toxins could leave residues on dishes, taking this precaution may help reduce possible exposure risk.

If you are not on public water and use surface water for drinking, preparing food, cooking, or making ice, you are at risk of exposure to HABs, cyanotoxins, and other common drinking water contaminants. Please contact your local health department (leaves DEC website.) More information about can be found on the Department of Health Blue-green Algae webpage (leaves DEC website.)

Fishing Concerns

How much HABs 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 cyanobacteria blooms.

Animal Exposure Concerns

HABs cells can stick to animal fur and become concentrated when the animal cleans itself. Rinse your dog, pet or livestock with clean water and seek veterinarian medical assistance should your animal show any signs of distress. HABs may release a fast-acting nerve toxin that can be dangerous for pets, particularly dogs that swim within blooms. Symptoms of HABs 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 algal bloom, seek immediate veterinarian care.

Long-term exposure to algal 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) brochure (leaves DEC website). 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.

Preventing HABs

Some lakes regularly experience HABs during most summers. Lakes listed on the HABs Archive page for this year or previous years may be particularly susceptible to recurrent blooms in the future. Neither DEC nor researchers can accurately predict exactly when or where blooms will occur. DEC collects and analyzes lake information to better understand why some lakes have blooms and others don't. The scientific community does not yet fully understand what triggers blooms or why some blooms produce toxins or other harmful compounds and others don't. Data collected in New York and other states continue to be studied to better understand HABs.

In most New York lakes, biological activity, including algal growth, is greatly reduced in the winter, as water temperatures fall and lakes ice over. Most algae growth decreases, although there are a few types of harmful algae that can grow in cold water, even under the ice. In rare cases, winter blooms have been reported in New York. Some HABs form overwintering spores that rest in bottom sediments and can cause blooms when water temperatures rise the following year.

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

  • Limiting lawn fertilization
  • Maintaining septic tanks
  • Installing and maintaining shoreline buffers
  • Reducing erosion and stormwater runoff
  • Improving 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.

Some lakes appear to be more likely than others to have frequent blooms. Excessive nutrients, particularly phosphorus, is probably the most important factor, but some lakes with relatively low nutrients still have blooms while some lakes with high nutrient levels don't have algal blooms. Preliminary results from studies conducted in New York and elsewhere suggest shallow lakes that repeatedly turn over during the summer, lakes with lower nitrogen to phosphorus ratios, and lakes with zebra mussels all may be more susceptible to HABs. Researchers continue to look at the characteristics of lakes with HABs in hopes of finding ways to minimize blooms. For more information, see the HABs Mitigation Studies page.

DEC has many ongoing programs to reduce the amount of nutrients going into NYS waters:

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 the Water Quality Improvement Project Program.

The DEC HABs Program

The DEC HABs Program consists of DEC staff within the Division of Water, Lake Monitoring and Assessment Section that work to identify HABs, communicate public health risks through outreach and education and conduct research. DEC maintains collaborative partnerships with NYS Department of Health (DOH) and NYS Office of Parks, Recreation and Historic Preservation to coordinate the response to HABs concerns around the state. DEC and DOH conduct research projects specifically to assess HABs risk and to better understand the conditions that trigger HABs occurrence.

DEC promotes long lasting partnerships with watershed organizations, lake associations and academic institutions to report HABs and inform the public about risks. Current partners include:

  • Canandaigua Lake Watershed Association
  • Chautauqua Lake Association
  • Citizen Science Institute
  • Finger Lakes Institute
  • Honeoye Lake Watershed Task Force
  • New York City Department of Parks and Recreation
  • New York State Federation of Lake Associations
  • Otisco Lake Preservation Association
  • Owasco Watershed Lake Association
  • Seneca Lake Pure Waters Association
  • Skaneateles Lake Association
  • SUNY College of Environmental Science and Forestry
  • SUNY Stony Brook University
  • The Lake Champlain Committee
  • The US Army Corps of Engineers, Pittsburgh District
  • The Vermont Department of Environmental Conservation
  • Upstate Freshwater Institute

Through these partnerships, participants receive training on how to identify and report HABs to DEC. For more information, see the HABs Reporting Guide.