PORT TOWNSEND — The lakes may look clearer, but the closure signs remain at Anderson and Gibbs lakes until more water samples are tested the middle of this month.
“You can’t always tell how toxic the lake is just by looking,” said Michael Dawson, lead environmental health specialist at the Jefferson County Public Health Department, last week.
“The wind might have blown the algae” that produces toxins in the lakes out of sight or “the algae might be beginning to decompose, but toxin levels might be high,” Dawson said.
“We still advise the public to be very cautious and heed those signs,” he added.
The latest tests of Anderson, Gibbs and Leland lakes were the week of Aug. 12.
The next tests will be the week of Sept. 16.
“I’m afraid we don’t have any more recent test data yet,” Dawson said Friday.
“Normally this time of year, our algae blooms tend to start to dissipate,” he said.
“Sometimes, the lakes have been looking a little better.
“But looks can be deceiving, so Gibbs Lake and Anderson Lake remain closed until we get another toxin sample back that is low in toxins,” Dawson added.
Anderson Lake has been closed since May 17, only three weeks into the fishing season, because of high levels of anatoxin-a, a potent nerve toxin that can kill within four minutes of ingestion.
In the August test, the sample from Anderson Lake, which is in Anderson Lake State Park near Chimacum, was found to contain a level of anatoxin-a that was below the recreational guideline. But the policy is to have two tests showing safe levels before reopening a lake to the public.
That’s because levels can fluctuate, Dawson said.
“We did see some declines in toxins at Anderson Lake, but we often get a resurgence at the end of the summer, so we may still see toxin levels climbing again,” he said.
The 410-acre state park around the 60-acre lake remains open for hiking, biking and horseback riding. A Discover Pass is needed to park there.
Gibbs Lake south of Port Townsend has been closed since July 18 because of high levels of microcystin.
Microcystin can cause skin irritation, nausea and muscle weakness if touched and liver damage if swallowed over a long period of time.
Lake Leland remains posted with a caution sign, though the level of toxins is barely detectable, because it contains algae known to sometimes produce toxins and has a light bloom.
Both anatoxin-a and microcystin are created by some strains of blue-green algae, also known as cyanobacteria, which are usually benign but which can suddenly begin to poison the freshwater lakes they grow in.
Scientists don’t know why.
They also don’t know why Anderson Lake has had historically high levels of anatoxin-a. In June 2008, the lake set a world record with 172,640 micrograms of anatoxin-a per liter. The safety threshold for the toxin is 1 microgram per liter.
Researchers at the University of Oregon and the Centers for Disease Control and Prevention in Atlanta are studying the algae in Anderson Lake to see if it is unique in the state — and if that will provide clues as to how to control it.
Although the final report isn’t expected until fall at the latest, researchers have identified the strain of anabaena — a type of cyanobacteria — that seems to be producing anatoxin-a in Anderson Lake, Dawson said.
“They isolated the particular strain, but they don’t know if it differs from other strains yet,” Dawson said.
In addition to testing for toxin levels, Jefferson County also tests monthly for nutrients that feed the blue-green algae.
Anderson Lake usually has a high amount of phosphorus, one of the nutrients that fuel algae growth, but the latest nutrient analysis of a water sample found that phosphorus was low in Anderson Lake, Dawson said.
“But what tends to happen, we think, is that phosphorus is used by the algae,” and after the algae dies off each year, the mineral is released back into the water to be used by the next crop.
“That’s the problem with phosphorus: It doesn’t really get out of the lake,” Dawson said.
Cow manure from a dairy farm that was operated near Anderson Lake for more than 50 years could be the source of high phosphorus levels, Dawson and Greg Thomason, Jefferson County environmental health specialist, said in a report released in February.
Testing for toxins was weekly until this year, when the state Department of Ecology cut back to a monthly frequency.
County public health department officials had hoped to find a way to finance more frequent tests but have not been successful, Dawson said Friday.
Toxin-producing blue-green algae has not been spotted in Clallam County.
Report algae blooms in Clallam County by phoning 360-417-2258, while Jefferson County blooms can be reported at 360-385-9444.
For more information about Jefferson County lakes, visit http://tinyurl.com/jeffersonlakequality or phone the office.
Managing Editor/News Leah Leach can be reached at 360-417-3531 or at leah.leach@peninsuladailynews.com.
