Anderson Lake was open for fishing and other water recreation Saturday for the first time since it was closed June 10.
The decision to reopen the lake, closed because of a dangerously high level of algae-produced toxins, was made after water samples tested below the warning threshold for three consecutive weeks.
“We’re going to reopen it as of tomorrow morning and keep it open until we get another bad sample,” Jon Crimmins, the state parks ranger who made the decision, said Friday.
Crimmins expected the fishing to be good at the popular trout lake, which is in Anderson Lake State Park near Chimacum.
“The fishing was doing well before the lake closed,” he said.
Levels of both anatoxin-a, a powerful nerve toxin that can cause convulsions and death by respiratory paralysis, and microcystin, which can cause liver damage, were far below the warning threshold in the three weekly tests.
But even though the closure sign came down, a caution sign is posted at the lake, said Greg Thomason, Jefferson County environmental health specialist, who recommended the lake be reopened.
That’s because the 70-acre lake still has a bloom of algae — and the algae is of species known to sometimes produce toxins.
So lake users should be careful around the water despite the good test results, Crimmins said.
“Swimming is probably not a good idea,” he said.
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.
Test results are always about a week behind the fact, since the samples are taken from the lake at the boat dock Mondays and results are received from King County Environmental labs Fridays.
The decrease in anatoxin-a fits the pattern of Anderson Lake — which has been plagued with deadly toxins since 2006, when two dogs died on Memorial Day after drinking lake water — except that it’s about six weeks behind schedule.
Anatoxin-a levels shot up late this season and have settled down late, Thomason said.
That’s probably due to a late summer, he said.
But the pattern for the lake is that when anatoxin-a goes down, microcystin levels tend to rise, he said.
That hasn’t happened so far, but it could, he said.
“We’re not done yet,” he warned.
“It’s good news right now, but hold on to your hats because anything could happen with microcystin.”
Levels of toxins also have been falling at other lakes in East Jefferson County, all of which test well below the warning threshold of 1 microgram per liter for anatoxin-a and 6 micrograms per liter for microcystin.
Leland, Gibbs and Silent lakes all are posted with caution signs only because of algae blooms.
In the latest tests, toxin levels for Anderson Lake were 0.13 micrograms per liter for anatoxin-a and 0.38 micrograms per liter for microcystin.
No anatoxin-a was detected in Gibbs, Leland or Silent lakes.
Gibbs Lake contained 0.63 micrograms per liter of microcystin, while none was detected in Leland and Silent lakes.
The state park around Anderson Lake has never been closed to use.
Each nonexempt visitor must have a Discover Pass to visit both the state park and the lake, Crimmins noted.
If purchased at a manned state park office or kiosk, the annual Discover Pass costs $30 per vehicle, and daily passes are $10.
The passes are $35 and $11.50 at www.discoverpass.wa.gov, by phone at 866-320-9933 or at outlets that also sell hunting and fishing licenses. A list of exemptions also can be found at the website.
Failure to display a Discover Pass on a vehicle can lead to a fine of $99.
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.