CHIMACUM — A spring bloom of toxic blue-green algae has closed Anderson Lake after only a three-week opening to boating and fishing.
The action portends another summer in which the centerpiece of the state park by the same name will be closed to fishing and other recreation — as it has for the last half of the decade.
Water samples taken May 11 and sent to King County Environmental Labs showed high levels of anatoxin-a, a potent neurotoxin at about 100 times the safe recreational limit, Jefferson County Public Health officials said.
Alison Petty, environmental health specialist with Jefferson County Public Health, said water samples taken after algae blooms were spotted on the lake showed 103 micrograms per liter of anatoxin-a, which is dramatically above the safety threshold of 1 microgram per liter.
“Anatoxin is a very nasty toxin,” Petty said. “And that, we suspect, is what killed the dogs in 2006.”
Toxic algae was first discovered in Anderson Lake in May 2006 when two dogs died after drinking water from the lake, which the county and state then closed.
Jefferson County Health Officer Tom Locke said it remains a mystery as to what makes Anderson Lake prone to blue-green algae toxins.
“It appears to be one of the most, if not the most affected lake in Washington state,” Locke said.
No telltale signs of such toxins have been found in Clallam County’s largest lakes — Crescent, Sutherland and Ozette.
Locke said it might come down to looking at natural nutrients as the source of blue-green algae toxins in Anderson.
“Anderson Lake is a senior citizen when it comes to lakes,” Locke said.
“It’s filled up with nutrients. It’s probably something that has accumulated over a long time, such as plant debris and breakdown products that create the nutrient media.”
No man-made sources
Locke said no other potential man-made nutrient sources — such as failing septic systems or agricultural fertilizers — have been identified in Anderson Lake.
Jefferson County Public Health officials on Tuesday posted a red warning sign at the lake’s boat ramp to notify the public that it was closed.
Petty said because of the risk of exposure to the toxin, Washington State Parks, in consultation with county Public Health, decided Tuesday to close Anderson Lake for recreational uses.
Other recreation not in the lake, such as hiking, horseback riding and biking, is still allowed at Anderson Lake State Park, and the main entry from Anderson Lake Road remains open during park hours.
Jefferson County Public Health will continue to monitor the lake weekly, Petty said.
If test results continue to show high levels of toxin, the lake will remain closed, she said.
Since 2006
Public Health has been collecting and submitting water quality and algae samples from Lake Leland, Anderson Lake and Gibbs Lake since 2006.
Lake Leland was downgraded last week to a “caution” warning just because algae blooms have been spotted there, Petty said.
That lake north of Quilcene is open to fishing and boating but closed to swimming, she said.
All other Jefferson County lakes remain open to recreational uses, such as fishing and boating, until further notice.
Anderson Lake opened in April 24 for the trout fishing season.
It was the first time that the blue-ribbon trout lake had been open since 2008 for fishing.
However, it was closed after three weeks during that year when toxin levels shot up as the weather warmed.
Jefferson County Public Health updates toxic blue-green algae reports at http://tinyurl.com/algaelake.
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Port Townsend-Jefferson County Editor Jeff Chew can be reached at 360-385-2335 or at jeff.chew@peninsuladailynews.com.
