Algal

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Cyanobacteria Harmful Algal Blooms

Cyanobacteria are photosynthetic bacteria that occur naturally in Idaho’s lakes and rivers. Many of us learned about “blue-green algae” in school, but these algae are actually bacteria that photosynthesize like algae and plants. The photosynthetic structures within the bacterial cell contain the blue-green pigments that gave cyanobacteria their former name of “blue-green algae.” Cyanobacteria are present in a water body but typically exist in numbers too small to cause problems (sight, smell, and cyanotoxins). However, a variety of environmental conditions influence cyanobacteria population growth. The right summer time conditions can allow cyanobacteria populations to “bloom” to high enough numbers that a variety of toxins, known as cyanotoxins, are produced. These ideal conditions include warm temperatures, low or slow water flow, high nutrient levels, strong light, and calm weather.

Cyanobacteria harmful algal blooms (HABs) in Idaho can vary in appearance, often looking like pollen, grass clippings, spilled paint, mats, foam, or a dense surface scum. Blooms can range in color from blue and bright green to brown, red, and even white. Some blooms may produce a foul odor.

Cyanotoxins can present a real threat to people and animals. Cyanotoxins are thought to primarily be metabolites and used for taking in nutrients. Toxin exposure primarily occurs from ingesting the cyanobacteria and the water they live in but may also occur with skin contact. Ingesting cyanotoxins, which can remain after a visible HAB subsides, can result in a range of health effects from skin irritation and stomach upset to neurotoxic effects and, at very high levels, death. Symptoms in humans are rare; anyone with symptoms should seek medical attention.

Health Advisories

Health advisories are typically issued by the public health districts, who work closely with DEQ staff.

Take the following precautions when an advisory is in effect:

  • Avoid exposure to water experiencing a HAB. Take extra precautions to ensure children, pets, and livestock are not exposed to the water.
  • Do not consume water with a HAB. Neither boiling nor disinfecting water removes cyanotoxins from water.
  • Consume only the fillet portion of fish exposed to a HAB. Cyanotoxins can accumulate in fish. Removing the fat, organs, and skin minimizes the exposure. Wash hands after handling. The risk associated with consuming fish caught in waters with a HAB is unknown and under research.

Harmful Algal Blooms FAQ

What causes a harmful algal bloom?

Cyanobacteria occur naturally in the environment and are a vital part of the ecosystem. A harmful algal bloom occurs when excessive growth cyanobacteria exists, which has the potential to produce toxins. Abundant nutrients (phosphorus and nitrogen), sunny conditions, warm temperatures, and low-flow or low-water conditions can contribute to exponential growth resulting in algal blooms.

When is a health advisory issued for a harmful algal bloom?

When a harmful algal bloom is suspected, the Idaho Department of Environmental Quality (DEQ) will collect a water sample from the affected water body and send it to a lab for analysis. Health advisories are issued for a water body when the number of cells in the water is above a level recommended as unsafe for recreating.

What about other types of algae?

Algae in our lakes, ponds, and streams are an essential component of the food web and a healthy aquatic ecosystem. Algae have many forms and colors, and most do not produce toxins. Cyanobacteria are the exception, and when algae blooms, toxins can be produced.

When a health advisory is issued, is the entire water body unsafe for recreational use?

Cyanobacteria occur naturally in the environment and are a vital part of the ecosystem. A harmful algal bloom occurs when excessive growth cyanobacteria exists, which has the potential to produce toxins. Abundant nutrients (phosphorus and nitrogen), sunny conditions, warm temperatures, and low-flow or low-water conditions can contribute to exponential growth resulting in algal blooms.

What does a harmful algal bloom look like?

The physical appearance of a harmful algal bloom can be unsightly, often presenting discolored water, streaks, or globs of scum, and causing thick green mats along shorelines. Blooms can vary in appearance, often looking like pollen, grass clippings, spilled paint, mats, foam, or a dense surface scum, and can range in color from blue and bright green to brown, red, and even white. Some blooms may produce a foul odor.

Can I swim and undertake other watersports when a harmful algal bloom is in process?

Swimming and water sports, including waterskiing, or other activities that result in direct contact  with affected water are not recommended.

What should I do if I come into contact with affected lake water when a harmful algal bloom is in process?

If contact with an affected water body does occur, users should remove any affected clothing and wash themselves thoroughly with clean water after coming ashore.

What are some of the symptoms?

Symptoms of exposure to toxins vary according to exposure. Exposure is most likely through contact with skin, ingestion, and inhalation. Symptoms include rashes, hives, diarrhea, vomiting, coughing, or wheezing. More severe symptoms affecting the liver and nervous system may result from longer or greater amounts of exposure. If symptoms persist, consult your local health care provider.

Is it safe for pets and other animals to access water when a harmful algal bloom is in process?

Harmful algal blooms may produce toxins that could kill or sicken pets. Do not allow your pet to swim in or drink water that may have a bloom, and thoroughly clean or throw away pet toys that were exposed to the bloom. After swimming in water, pet’s fur can contain toxins and can be ingested when the pet cleans and licks fur. If pets do come into contact with a harmful bloom, rinse them off immediately. Livestock owners are reminded to continue to check stock water supplies for cyanobacteria and to remove stock from foreshores when cyanobacteria are present in the water body.

How will the public know when conditions are safe again?

The public will be advised when levels have returned to normal and toxin levels are below the safety threshold. The public should always avoid contact with and ingesting water from surface water with a scum layer that they are unfamiliar with or when the water has an unsightly color.

What do I do if I observe surface water with a scum layer or when the water has an unsightly color?

Call DEQ at (208) 373-0502 to report a potential harmful algal bloom, and you will be directed to the appropriate regional office. Download the bloomWatch app to learn what to look for and report a bloom to DEQ. DEQ bases responses on calls received by the public and relies on public observation for identifying potential harmful algal blooms.

Public Health - Idaho North Central District
215 10th Street
Lewiston, ID 83501

Phone: (208) 799-3100
Fax: (208) 799-0349

Idaho Careline: 211

To report a Public Health risk, Contact Public Health 24/7 here.
For medical emergencies dial 911.

Disclaimer

All information is general in nature and is not intended to be used as a substitute for appropriate professional advice.

For more information please call (208) 799-3100 or Idaho Careline: 211.

Idaho Public Health

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