PORT TOWNSEND — The level of algae-produced toxins has ratcheted up in Anderson Lake, while an algae bloom in a small lake in the Toandos Peninsula never before tested for toxins led to the posting of a yellow “caution” sign there.
The amount of anatoxin-a, a powerful neurotoxin, was measured at 1.3 micrograms per liter in Anderson Lake water samples taken Tuesday, according to preliminary testing results released Friday.
The week before, samples show 0.22 micrograms of anatoxin-a per liter, said Greg Thomason, Jefferson County environmental health specialist.
“It’s gone up about six times,” he said.
The state threshold for posting a warning sign is 1.0 micrograms of toxin per liter.
The new test results triggered an upgrade in the lake’s status, which was posted this weekend with a “warning” sign replacing the “caution” sign that had been in place at the popular 70-acre trout fishing hole between Chimacum and Port Hadlock.
Warning sign posted
The difference between the two is that a “caution” sign means toxins may be present in the lake, while a “warning” means they have been found in the lake but not at concentrations that warrant closure to fishing.
A “warning” sign still permits consumption of fish from the lake, so long as they are cleaned and gutted.
Thomason also observed a bloom of algae along the shoreline near the boat dock of the lake in Anderson Lake State Park.
“The lake itself doesn’t look too bad,” he said, but “there was a visible bloom for the first time” this year.
“It’s a relatively minor bloom compared to what we’ve seen in the past” at the lake, which has been plagued with toxic blue-green algae seasonally for six years, Thomason said.
“It’s not bad enough to close it.”
Decisions about changes in the status of the lake — including changes in warnings signs or closure — are made by State Parks after hearing recommendations from the county, Thomason said.
Silent Lake
On Friday, Thomason posted a yellow “caution” sign at Silent Lake, a small county lake north of Coyle at the intersection of Coyle and Thorndyke roads in the Toandos Peninsula south of Port Townsend.
The lake is open to the public and is stocked with fish by the state Department of Fish & Wildlife.
A homeowner near the lake reported seeing an algae bloom, so county personnel took a sample of the water, even though the lake is not usually tested.
“The toxin levels were not detectable,” Thomason said results from King County Environmental labs showed, “but there was a definite bloom going on in that lake,” and the type of algae found in the lake, anabaena, is known to be able to produce toxins.
“Right now, it’s not producing toxins,” Thomason said.
But that could change.
Researchers don’t understand why certain kinds of cyanobacteria, or blue-green algae — which is present in most bodies of water and usually is not toxic — will suddenly begin to put toxins in the water.
They know that calm water, warmth and a high concentration of such nutrients as phosphates, a chemical commonly found in lawn fertilizers, can encourage a bloom of algae.
But they don’t understand why such algae sometimes begins producing toxins that can make lake water deadly.
Anderson Lake water killed two dogs that lapped from it during Memorial Day weekend in 2006, the first year the lake was closed because of algae toxins.
Both dogs died quickly — and they are thought to have been killed by anatoxin-a, which can cause convulsions and death by respiratory paralysis.
Another toxin historically found in East Jefferson County lakes is microcystin, which can damage the liver.
Microcystin has not been detected this season.
Leland, Gibbs
The latest test results found microcystin below detectable levels and anatoxin-a barely detectable at 0.05 micrograms per liter in Lake Leland, which is north of Quilcene and south of U.S. Highway 101.
Both toxins were below detectable levels in Gibbs Lake in Chimacum.
Anyone who observes an algae bloom at a lake is urged to phone the Jefferson County Public Health Department at 360-385-9444.
For more information about lake quality in Jefferson County, visit the environmental health website at http://tinyurl.com/6z64ofy.
No toxic blue-green algae has been reported in Clallam County, where health officers visually monitor lakes for signs of algae bloom.
Algae blooms in Clallam County lakes should be reported to the Clallam County Department of Health and Human Services’ environmental health division at 360-417-2258.
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Managing Editor/News Leah Leach can be reached at 360-417-3531 or leah.leach@peninsuladailynews.com.