Anderson Lake High in Toxin

Port Townsend – Elevated levels of the potent nerve toxin anatoxin-a were detected in a water sample taken from Anderson Lake on Monday, April 25th. The toxin level is 1.30 micrograms per liter, which is just above the Washington State recreational criteria of 1 microgram per liter. The bloom of cyanobacteria in the lake contains toxin-producing species of algae, including Dolichospermum (formerly Anabaena) and Aphanizomenon. Anatoxin-a can result in illness and death in people and animals when ingested.

Washington State Parks has posted “Danger – Keep Out of Lake” signs at access points to the park alerting visitors of the potential hazards. Recreational activities such as fishing, boating, and swimming are prohibited until the toxins dissipate and the lake is deemed safe for recreation. Anderson Lake State Park remains open for other recreational activities such as horseback riding, hiking, and birdwatching.


Jefferson County Public Health has monitored local lakes for cyanobacteria since 2007 and Anderson Lake has had closures every year since then, including very high levels of toxin. Anderson Lake was monitored monthly this winter, and toxins were not detected, but starting in April, bloom activity and toxin level have been steadily rising. In addition to Anderson Lake, Crocker, Gibbs, Leland, and Tarboo lakes have all been assessed for cyanobacteria activity this year and found no evidence of blooms forming.

More Info