Anderson Lake will remain closed to recreation for at least one more week, despite passing the toxins test for two weeks in a row.

But if it tests clear next week, it might be reopened the following week, in time for the Labor Day holiday weekend, said Mike Zimmerman, manager of Anderson Lake State Park between Chimacum and Port Hadlock.

“We had two good samples, which is really good news,” Zimmerman said Friday. “But my decision is to not open until we get one more [safe level] sample.”

The 70-acre lake was closed June 10 because it contained a high concentration of antatoxin-a, a powerful nerve toxin that can cause convulsions and death by respiratory paralysis.

Weekly tests of samples continued to find high levels of the toxin, which is created by blue-green algae growing in the lake, until Aug. 12, when a sample taken the preceding Monday contained only 0.26 micrograms of the neurotoxin per liter of water.

The latest test results of a sample taken last Monday and received Friday contained 0.4 micrograms of antatoxin-a per liter of water, and so also was far below the safety threshold of 1 microgram per litter.

The policy is to consider reopening a lake after two consecutive weekly tests show safe levels, said Zimmerman, who makes the decision about the status of the state lake, and Greg Thomason, Jefferson County environmental health specialist, who makes recommendations on action.

Lake’s history

But both experts wanted to hold off because they are leery of the lake’s history.

Anderson Lake has been plagued with deadly toxins since 2006, when two dogs died on Memorial Day after drinking lake water.

Since then, “We have had it happen before that toxin levels drop in the summer then bounce up again,” prompting another closure of the lake, Thomason said.

That creates a health risk because “it takes people time to realize it’s closed again,” Zimmerman said.

Areas of Anderson Lake still are covered in an algae bloom made up of the species known to create toxins.

Blue-green algae growth itself is thought to be encouraged by warm, sunny weather when sufficient nutrients, such as phosphates, are present. But researchers don’t understand why some species of blue-green algae will begin to produce toxins nor what fuels increases in the amount of toxins. And between the taking of a sample and the results of a test, conditions can change.

The closure doesn’t affect the 410-acre state park surrounding the lake.

Tests detected no anatoxin-a in both Leland and Gibbs lakes, which remain posted with warning signs because of algae blooms.

The level of microsystin, an algae-produced toxin that can cause liver damage, was far below the safety threshold of 6 micrograms per liter in Anderson, Leland and Gibbs.

Information about lake quality is posted at http://tinyurl.com/6z64ofy.

To report blooms in Jefferson County, phone 360-385-9444.

To report algae blooms in Clallam County, phone 360-417-2258.

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Managing Editor/News Leah Leach can be reached at 360-417-3531 or leah.leach@peninsuladailynews.com.