Anderson Lake at Warning Level

This just in from the Jefferson County Health Department.

Port Townsend – A toxic cyanobacteria (bluegreen algae) bloom that has kept Anderson Lake closed since early June has dissipated. Two consecutive samples taken by Jefferson County Public Health (JCPH) on Tuesday, November 13 and Monday, November 26 showed that toxins have declined to safe levels. The anatoxin-a concentrations were found to be 0.168 and 0.129 micrograms per liter, respectively, and both of those samples are below the 1 microgram per liter recreational guideline set by the Washington Department of Health. Microcystin was found in the November 13 sample at concentrations below the recreational guideline of 6 micrograms per liter and it was not detected in the November 26 sample. With the recommendation from JCPH, Anderson Lake State Park will remove the closure signs and post the lake at a Warning level. Anderson Lake State Park will have limited parking available due to the gate remaining closed this season, but the lake will be open for walk-in fishing.

Algae species that can produce toxins are still present, and blooms can develop even in the winter, so the public is urged to follow these guidelines:

  • Use the lake at your own risk.
  • Avoid contact with areas of scum, or water that is green in color. Keep children and pets out of the water.
  • Clean fish well and discard the guts. Some algae toxins are known to accumulate in fish tissue.

Jefferson County Public Health has monitored local lakes for cyanobacteria since 2007. Regular monitoring of blooms, and toxin testing, have ended for the season but will resume in April, 2019.

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 Washington Department of Fish and Wildlife website Information on visiting Anderson Lake State Park is available at


What makes Anderson Lake so unusually toxic? Scientists to try to find answer – PDN

Anderson Lake, which has the dubious distinction of setting a poisonous world record in 2008, is under a microscope. The goal: to try to find out why one of the North Olympic Peninsula’s most popular fishing spots has been plagued since 2006 by soaring levels of anatoxin-a, a potent nerve toxin produced by blue-green algae. Jeremy Schwartz reports.

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Anderson Lake Remains Closed–Toxin Levels High – PDN

The level of a fast-acting nerve poison in Anderson Lake has leaped to more than 500 times the warning level, according to results of tests taken last week. The lake between Port Townsend and Chimacum, which was closed May 3 this year because of elevated levels of toxins produced by blue-green algae, remains closed to recreation. The level of anatoxin-a, which can quickly cause convulsions and stop breathing, was measured at 534 micrograms per liter of water. The safety threshold is 1 microgram per liter.    Anderson Lake toxins highest of the year

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