The latest test results found the concentration of a powerful neurotoxin in Anderson Lake had fallen to a safe level for the first time since the lake was closed for the season June 10.
The lake remains closed to any recreation, including fishing, since one test result from one sample isn’t enough to convince experts that the lake is safe.
But a second clear sample this week could lead to Anderson being reopened before the end of the fishing season Sept. 30.
“Our policy is, we have to get two weeks of safe level readings before we recommend reopening the lake,” said Greg Thomason, Jefferson County environmental health specialist, Friday.
The latest sample, which was pulled from the lake a week ago today, contained 0.26 micrograms per liter of water of anatoxin-a, a fast-acting nerve toxin that can cause convulsions and death by respiratory paralysis.
The safe level is 1 milligram per liter.
If the sample taken today at the Anderson Lake boat launch results in another low reading Friday, then the county will recommend reopening the lake, he said.
“We’ll see what happens,” he said. “We’re keeping our fingers crossed.
Park, other lakes, open
The closure doesn’t affect the 410-acre state park surrounding the 70-acre lake between Chimacum and Port Hadlock.
Fishing is permitted at all other lakes in East Jefferson County, although both Gibbs, south of Port Townsend, and Leland, north of Quilcene, are posted with warning signs, and Silent Lake on the Toandos Peninsula has a caution sign.
Sandy Shore Lake south of Port Ludlow near state Highway 104 remains clear, Thomason said.
Reopening Anderson Lake to the public isn’t the county’s decision.
State Parks decision
Since Anderson Lake is in a state park, it is state Parks officials who decide if the lake is to be open or closed to the public.
And even if county specialists recommend reopening it, their state counterparts could decide to keep it closed, simply because the toxin content of a lake infested with blue-green algae can change quickly.
Instead of a seesaw of opening and closing, officials sometimes will opt for a longer view of conditions, Thomason said.
“Sometimes they keep it closed because it could change again,” he said.
The lake should not be considered safe now, despite the low toxin content of one sample.
Testing is always a week behind the fact, since samples are taken Mondays and results are received from King County Environmental labs Fridays.
And the cause of the appearance of the toxin, as well as the levels of toxin, are something of a mystery.
Researchers know toxins are created by blue-green algae.
Blue-green algae growth itself is thought to be encouraged by warm, sunny weather when sufficient nutrients, such as phosphates, are present.
But only certain species of algae produce toxins.
Researchers don’t fully 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.
Highest level
Anderson Lake toxin readings have been decreasing since a June 24 test result showed 1,112 micrograms per liter of anatoxin-a.
But the downward trend could change, Thomason said.
“We’ve seen this before, and it’s come back up,” he said.
However, he is hopeful that the worst is over for this year.
“We’re seeing fewer varieties of [the algae species] that can create toxins,” he said.
The rise and fall is a familiar phenomenon.
“We see this every year,” Thomason said.
The algae “wear themselves out like flowers in your garden,” he said.
“They bloom and then they’re done.”
Anderson Lake has been plagued with deadly toxins in the summer months since 2006, when two dogs died on Memorial Day after drinking lake water with a heavy concentration of anatoxin-a.
Can’t tell by looking
It’s impossible to tell by a lake’s appearance if it is poisonous or not.
“Anderson still has a bloom,” he said. “Gibbs still has a bloom. Gibbs actually looks worse than Anderson.
“But the toxins are what tell the story.”
For instance, testing last week found that Gibbs, with its heavy algae bloom, had no detectable anatoxin-a.
None of the neurotoxin was found in Leland or Silent lakes, as well.
The level of microcystin, another algae toxin that has been found in East Jefferson County lakes, is well below the safety threshold in all the lakes that are tested.
The safe limit for microcystin — which can cause liver damage with chronic exposure — is 6 micrograms per liter, Thomason said.
The level found in samples last week was 0.9 in Anderson, 0.1 in Leland, 0.4 in Gibbs and none detected in Silent.
Warning and caution signs are based on the types of algae in the water and whether or not any toxins have been detected.
Some ignore signs
Still, some ignore the signs, Thomason said.
“People are still going in the water” at Anderson Lake, despite the signs that say “danger, closed,” Thomason said.
The volunteer camp host has had to tell some people to get out of the lake, Thomason said.
“We’re glad he’s there,” Thomason said.
“He may be saving some people’s lives.”
Information about lake quality is posted at http://tinyurl.com/6z64ofy.
To report blooms in Jefferson County, phone 360-385-9444.
Clallam County health officers do not test for toxins. Instead, they look for algae blooms.
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.