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Posted on: May 9, 2019

Anderson Lake Closed Due to Toxin

Danger Lake Closed Sign image

May 9, 2019

For Immediate Release

Contact: Michael Dawson

Water Quality Manager

Jefferson County Public Health

(360) 385-9444

Port Townsend – High levels of the potent nerve toxin anatoxin-a were detected in a water sample taken from Anderson Lake on Monday, May 6th. The toxin level is 9.5 micrograms per liter, which is above the Washington State recreational criteria of 1 microgram per liter. The bloom of blue-green algae (also known as cyanobacteria) in the lake contains several toxin-producing species of algae, including Dolichospermum (formerly Anabaena). Anatoxin-a can result in illness and death in people and animals. Washington State Parks has closed the lake for recreation including fishing, boating, and swimming. Visitors are also urged to keep pets out of the water. The rest of Anderson Lake State Park remains open for hiking, biking and horseback riding. Blooms have also appeared this year at Gibbs Lake and Sandy Shore Lake, but toxins have not been detected at either of those lakes so far in 2019.


Photomicrograph of Dolichospermum from Anderson Lake by Tim Weissman, April, 2019

Jefferson County Environmental Public Health (JCEPH) has monitored local lakes for cyanobacteria since 2007 and Anderson Lake has had closures every year since then. In March 2019 JCEPH began collecting water quality data and water samples to be analyzed for nutrient concentrations as part of a lake management plan to identify the underlying cause of the toxic cyanobacteria blooms and determine potential strategies for mitigation. This project is funded in part through a grant from the Washington State Department of Ecology.

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


Jefferson County Public Health
Always Working for a Safer and Healthier Community

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