Harmful Algae Blooms

What is a blue-green algae bloom?

Blue-green algae or cyanobacteria are bacteria naturally found on land and in water bodies. A combination of warm temperatures, sunlight, and nutrient-rich waters can cause blue-green algae to reproduce rapidly, or "bloom." These blooms usually float to the surface and can be several inches thick near the shoreline. They often look like blue-green paint was spilled on the surface of the water, but can also look bluish, brownish, or reddish green.

Most lakes will naturally have an occasional algae bloom. Temperature, wind and sunlight play a role in the formation of blooms. An excess of nutrients, particularly phosphorus, can increase the frequency and severity of algae blooms. Frequent algae blooms can be a sign of declining water quality.

Harmful algae blooms (HABs)

Most blue-green algae blooms do not present a health risk. However, some can produce toxins that can be harmful to pets and humans, especially if any of the water containing the toxins is swallowed.  People and animals can also get exposed through skin contact during swimming, breathing in small airborne droplets that contain toxins or eating food or supplements containing toxins.

What do I do if I see a blue-green algae bloom?

Algae blooms can be patchy, move to other parts of the lake and change with time. When in doubt, follow these guidelines when you see an algae bloom:

  1. Do not swim or water ski in areas where algal scum has accumulated.
  2. Do not drink lake water.
  3. Keep kids, pets and livestock away from areas where a visible bloom is present.
  4. Clean fish well and discard entrails – do not feed them to your pets.

If you see a blue-green algae bloom that can be tested from an area that is publicly accessible, please contact us at 360-778-600 or [email protected] to report it. Once a bloom has been reported, WCHCS will visit the site and determine whether sampling is necessary. If a sample is taken and the lab results show that a bloom is toxic, we will post appropriate signage and send notifications to the community of potential health concerns.  

We can only test if the area with the bloom is within a general public access area. If you see a blue-green algae bloom adjacent to private property, call our office or visit www.nwtoxicalgae.org to obtain sampling instructions.

Testing does not ensure that all areas of a lake are safe. 

What are the signs of toxic algae poisoning?

Blue-green algae can produce nerve toxins (neurotoxins) and liver toxins (hepatotoxins). Signs of neurotoxin poisoning include numbness, tingling and dizziness in humans. In animals, symptoms can include weakness, staggering, difficulty breathing, convulsions and death. Signs of hepatotoxin poisoning include abdominal pain, diarrhea and vomiting in humans and death in animals. Call your doctor or veterinarian right away if you or your pets have signs of poisoning.

Can I eat fish from the lake when a toxic bloom is present?

Toxins can accumulate in fish tissues, especially in the liver, kidneys and other organs. Before eating, remove internal organs, which may contain more of the toxin.

Is it safe to drink water from the lake during a bloom?

No, do not use this water as a drinking source, even if using a filter. A water filter or purifier will not remove the toxins. 

What can I do to help prevent toxic algae?

The best way to help prevent future toxic algae blooms at your lake is to reduce phosphorus coming into the lake. This includes: 

  • Avoiding fertilizers for your lawn or using phosphorous-free fertilizer 
  • Clean up pet waste immediately.
  • Scheduling a routine septic system inspection. 
  • Re-establishing shoreline vegetation by replacing lawn with native plants. 
  • Wash your car at a commercial car wash or on your grass lawn to prevent runoff directly into the lake.

Additional Resources

Current Projects

Wiser Lake

Contact Us

Phone: 360-778-6000

Email: [email protected]