Cyanobacteria

What is cyanobacteria?

Cyanobacteria, also known as blue-green algae, are tiny organisms commonly found on land and in lakes, rivers, ponds, estuaries, and marine water.

What is a cyanobacteria bloom?

A combination of warm temperatures, sunlight, and nutrient-rich waters can cause cyanobacteria to reproduce rapidly. Within a few days, a clear lake, pond, or ditch can become cloudy with algae growth, which is called a "bloom." These blooms usually float to the surface and can be several inches thick near the shoreline.

Although cyanobacteria can be a nuisance and cause poor water quality, most are not toxic. A cyanobacteria bloom:

  • Often looks like green paint floating on the water, but it can also look bluish, brownish, or reddish green.
  • Is made up of extremely small organisms that cannot be identified by eye.
  • Is most common in the summer and fall, but it can form anytime.

What is a toxic bloom?

Some cyanobacteria produce toxins or poisons called cyanotoxins. These cyanotoxins can cause illness in humans, pets, waterfowl, and other animals that come in contact with the algae. In severe cases, toxic blooms can kill livestock and pets that drink the water. Eventually, the toxins break down in the water and are destroyed naturally.

Signs of a toxic bloom include:

  • Dead fish, waterfowl, or other animals.
  • Sudden, unexplained sickness or death of a cat or dog, especially if it has algae on its mouth, legs, or feet.
  • Skin rashes on humans after being in the water.

How do the toxins affect animals and humans?

Cyanobacteria can produce both nerve toxins (neurotoxins) and liver toxins (hepatotoxins). Call your doctor or veterinarian right away if you or your pets or livestock have signs of poisoning.

Drinking water is sometimes taken from surface water sources (such as reservoirs) that can have algal blooms. If there is a bloom, do not drink the water until laboratory testing shows the water is safe.

Neurotoxin (Nerve) Poisoning

  • In people, signs include numbness of the lips, tingling in fingers and toes, and dizziness.
  • In animals, signs include weakness, staggering, difficulty breathing, convulsions, and death.
  • Signs appear within 15–20 minutes after ingestion.

Hepatotoxin (Liver) Poisoning

  • Signs include abdominal pain, diarrhea, and vomiting in humans and death in animals.
  • It may be hours or days before signs of liver poisoning appear.

What if I see a bloom?

How can I get a lake sample tested for algae?

If you think your lake has an algae bloom, go to Washington State Toxic Algae, Report and Test a Bloom for help identifying the algae and conducting a toxin analysis. 

What happens if a test confirms a toxic bloom?

If a test shows that a bloom is toxic, county health officials will decide whether to close the lake for recreation, post notifications, or wait for further testing.

Can testing ensure that all areas of a lake are safe?

No. Cyanobacteria blooms are known to be very patchy. There may be higher levels in areas not surveyed, particularly along shorelines. People and pets should avoid contact with lake water that clearly contains algae or has a green to blue-green color.

How is it determined when the water becomes safe once a bloom is reported?

The Washington State Department of Health recommends testing the water once a week after toxin levels are identified as too high. Recreational use should be avoided until levels drop below recommended guidelines. Local health officials will decide when to reopen an area.

Can I eat fish from cyanobacteria contaminated water?

Toxins can accumulate in fish tissues, especially in the liver, kidneys, and other organs. Be cautious about eating fish caught in areas where major cyanobacteria blooms occur. Before eating, remove the fish’s internal organs, which might contain more of the toxin.

How can I help?

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