Washington State Toxic Algae

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Welcome to the freshwater algae site

The purpose of this site is to provide toxin data related to cyanobacteria blooms in Washington lakes, ponds and streams. Washington State Department of Ecology (Ecology) uses this site to share the data from their ongoing freshwater algae monitoring program.

Cyanobacteria (or blue-green algae) can produce toxins at levels that are harmful to humans, pets, domestic animals, and wildlife. There is no way to detect toxins in an algae bloom except through laboratory analysis. This website provides access to Ecology's results.

Find your lake

Use our database to locate a lake and find out the most recent testing.
Or find your lake >

See lakes with algae bloom

Examples of local lakes experiencing algae blooms.
View our gallery and descriptions.

Report a bloom

If you think that your lake has an algae bloom and you want to have the algae identified: Report a bloom.

Know Your Signs

If you see a Warning or Danger sign at a lake, make sure you know what to do.

Current lakes with values above guidelines

Location	Last Sample Date
Anderson Lake	10/02/2023
Lake Washington Arrowhead PT	11/14/2023
Lake Wilderness	11/14/2023

News and announcements

6/28/2023 KOMO
Toxic algae bloom at Lake Lawrence in Thurston County prompts health advisory

6/16/2023 KHQ
Toxic algae reported at Potholes Reservoir

5/25/2023 WA Dept of Ecology
Headed to a lake or river today? Look out for blooming harmful algae!

5/15/2023 Seattle Met
Should We Be Scared of Washington's Toxic Lakes?

4/26/2023 Kitsap Sun
Kitsap Lake access closed due to potentially toxic algae bloom

Links to external sites do not constitute endorsements by King County. By visiting this and other King County web pages, you expressly agree to be bound by terms and conditions of the site. For questions on the Freshwater Algae Program please contact . For questions on the content or functionality of the site please contact . For information or concerns about a current Algal Bloom please contact your local Health Department.