PORT TOWNSEND — Test results show that toxins in Anderson Lake have decreased, but the lake remains closed — and is likely to stay closed for at least another two weeks.
Last week’s sample contained 2.3 micrograms per liter of anatoxin-a — a fast-acting neurotoxin that can cause convulsions or even death in mammals, said Neil Harrington, Jefferson County Public Health water quality manager, Friday.
That’s an improvement over the 7.3 micrograms of anatoxin-a found in a sample of the lake water on April 24 — which led to the closure of the popular trout-fishing lake in Anderson Lake State Park near Port Townsend just before the April 25 annual fishing season-opener.
But it’s not enough of an improvement, Harrington said.
State health officials recommend cutting off recreational exposure at 1 microgram per liter.
And even if results had come in below that threshold, the county health department generally doesn’t change its recommendations based upon only one test result.
Two clear weeks
At least two weeks of results — and perhaps more — showing a lake to be clear of toxins is needed before permitting usual recreational use, Harrington has said.
“It’s better than last week,” Harrington said of the Anderson Lake results Friday.
“But it’s not yet a trend. Next week, if it’s gone down again, I will start to get cautiously hopeful.”
All lakes tested in Jefferson County showed some improvement, Harrington said, but warnings have not changed.
Anderson Lake remains completely closed for recreation, although the park is open.
Gibbs Lake near Chimacum, and Lake Leland north of Quilcene are not closed to recreation, but the county health department warns against eating fish from the lake, drinking the water or swimming in them.
They can be used for such activities as boating, catch and release fishing, hiking, bicycling and bird-watching.
The warnings at Gibbs and Leland lakes are based on a high concentration of algae in the water.
The county tests both for toxins and the number of cells of algae per liter.
No toxins were found in Gibbs or Leland lakes, Harrington said on Friday, but the potential is there, given that samples from both contained more than 100,000 cells of algae per liter.
The state recommends issuing a caution when the algae cell count reaches 30,000 per liter, and issuing a warning when the cell count hits 100,000 per liter, Harrington said.
“We also have been keeping a eye on Crocker Lake, Teal Lake and Tarboo Lake,” Harrington said. “They have all seemed to be clear so far.”
Sandy Shore Lake has very low concentrations of algae, and no toxins, so it also is open for recreation, he said.
Lake samples are not tested in Clallam County, where health officers visually monitor lakes for signs of algae bloom. No cautions or warnings have been issued in Clallam County.
Results a surprise
The lower amount of toxin found in the Anderson Lake sample last week was a surprise. Harrington has said that experience has shown that lakes, once the toxin appears in the spring, become progressively more toxic in the summer.
That’s because warmer weather — or at least sunlight — seems to contribute to blooms of blue-green algae, which can produce toxins. Scientists don’t know why algae becomes toxic.
Algae blooms in fresh water lakes, which occur naturally, are fed by nutrients such as nitrogen or phosphorus, which can come from fertilizer, sewage, lake sediments or other sources, Harrington said.
Since 2006, Jefferson County Public Health has tested water samples from Lake Leland, Anderson Lake and Gibbs Lake to determine what species of algae are present and at what concentration.
Two dogs died from drinking Anderson’s water in spring 2006. That was the first indication that the popular trout fishing lake was poisoned, and the first year it was closed.
This year is the first time the lake has been closed before the fishing season began.
The health department is conducting weekly tests through the fall. Samples are collected on Monday and sent to King County Environmental Labs for analysis, with results generally announced by Friday.
County researchers also are collecting samples for nutrient analyses and physical data to determine possible causes for the blue-green algae blooms in a study funded with a $45,000 state Department of Ecology grant.
The county health department expects to complete the study early next year, Harrington said.
Jefferson County Public Health maintains an updated database of lake monitoring information at www.jeffersoncountypublic health.org/. The department can be reached at 360-385-9400.
Algae blooms in Clallam County lakes should be reported to Clallam County Department of Health and Human Services environmental health division at 360-417-2258.
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Managing Editor Leah Leach can be reached at 360-417-3531 or leah.leach@peninsuladaily news.com.
