PORT TOWNSEND — The toxins in Anderson Lake were measured below the warning level last week for the first time since it was closed for the season May 3 — but the lake will remain closed for at least one more week.
The level of anatoxin-a, a quick-acting nerve poison produced by blue-green algae, was measured at 0.95 micrograms per liter of water — just below the warning level of 1 microgram per liter — in a sample taken from the lake last Monday, said Greg Thomason, Jefferson County environmental health specialist, Friday after test results were received.
The county recommendation to State Parks is that the lake in Anderson Lake State Park remain closed until two weeks of test results show that the lake is safe.
“We need one more week of anatoxin being below the warning level and then we’ll recommend that the state open it,” Thomason said.
Only the lake is closed in Anderson Lake State Park, which is between Port Townsend and Chimacum. The 410-acre parkland surrounding the lake remains open. A Discover Pass is needed to park there.
Toxin levels can change quickly, so public health officials want to see additional results before recommending that the lake be reopened for fishing and other recreation.
The level of microcystin, a potential liver toxin over the long term that can cause skin irritation and nausea in the short term, was measured in Anderson Lake at 0.06 micrograms per liter, far below the warning level of 6 micrograms per liter.
Elevated levels of anatoxin-a have prompted closures of the lake since two dogs died after drinking lake water during the Memorial Day weekend in 2006.
This season, the popular trout-fishing lake opened only for a few days before skyrocketing levels of anatoxin-a prompted its closure.
Samples in the first week of July contained 619 micrograms per liter of the deadly toxin.
Other lakes in East Jefferson County are safe, Thomason said, although he is watching Gibbs Lake warily.
The most recent sample from Gibbs Lake showed no anatoxin-a and a safe amount of microcystin at 2.5 micrograms per liter — but the level of microcystin is rising.
“Two weeks in a row, it’s still rising,” Thomason said.
The popular swimming hole south of Port Townsend also has a heavy bloom with scum along the shore, he said.
Toxins could be concentrated in the scum, he said.
“People shouldn’t let their toddlers get into it,” he warned.
Neither anatoxin-a nor microcystin could be detected in Lake Leland north of Quilcene.
Caution signs remain posted at Gibbs Lake and Lake Leland because both contain species of blue-green algae that are known to sometimes produce toxins.
Researchers know that warm weather fuels algae growth when sufficient nutrients such as phosphates are present, but they don’t know why some types of algae, which usually are benign will suddenly begin to produce toxins.
The low levels of toxins are a typical pattern for the time of year, Thomason said.
“It’s a nice time when we have low toxins,” he said. “Both tend to drop off.”
If the pattern holds, the level of anatoxin-a will stay low for the rest of the season while microcystin creeps up, Thomason said.
“Later in August, microcystin usually picks up,” he said.
“We’ll have to sit tight and see what happens.
Anatoxin-a acts quickly and can cause paralysis and stop breathing.
The most severe effect of microcystin is that some people could develop liver failure if they have consumed water containing the toxin over a long period of time.
Its short-term effects can include nausea, vomiting, diarrhea, skin irritation and burning, abdominal pain, blistering in the mouth and sore throat.
Weekly test results are announced Fridays after samples are taken Mondays.
No toxic blue-green algae has been reported in Clallam County, where health officers do not test for toxins; instead, they visually monitor lakes for signs of algae bloom.
Report algae blooms in Clallam County by phoning 360-417-2258.
Report algae blooms in Jefferson County by phoning 360-385-9444.
For more information about lake quality in Jefferson County, visit the environmental health website at http://tinyurl.com/6z64ofy.
Managing Editor/News Leah Leach can be reached at 360-417-3531 or at leah.leach@peninsuladailynews.com.