Anderson Lake High In Toxins

Contact: Michael Dawson

Water Quality Manager

Jefferson County Public Health

(360) 385-9444  x301

Port Townsend Very high levels of the potent nerve toxin anatoxin-a were detected in a water sample taken from Anderson Lake on Monday, May 10th. The toxin level is 1,396 micrograms per liter, which is well 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 – Lake Closed” signs at access points to the park alerting visitors of the 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, biking and birdwatching.  

Cyanobacteria Bloom

JCPH has monitored local lakes for cyanobacteria since 2007 and Anderson Lake has had closures every year since then. In May 2019, a dog died after short exposure to Anderson Lake water. Other dog deaths have occurred in the past. In addition to Anderson Lake, Crocker, Gibbs, Leland, Silent, and Tarboo lakes have all been assessed for cyanobacteria activity this year and found no evidence of blooms forming.

To check the status of Jefferson County Lakes and learn more about toxic cyanobacteria monitoring, consult the JCPH website at or call (360) 385-9444. For fishing seasons and regulations, see the WDFW website Information on visiting Anderson Lake State Park is available at


Always working for a safer and healthier community