Six people were swimming in Gibbs Lake on Thursday, and that worried Jefferson County environmental health specialist Greg Thomason.
Thomason was at the lake south of Port Townsend changing out a “caution” sign for a “warning” sign.
“Gibbs is becoming a problem,” he said Friday.
While Anderson Lake apparently remains safe for fishing during the Labor Day weekend, the level of an algae-produced toxin in Gibbs Lake is climbing, he said.
The level of microcystin, a slow-acting toxin produced by blue-green algae, is below the safety threshold of 6 micrograms per liter of water, tests show, but it has been climbing.
The latest test results, received Friday, show that the lake sample contained 3.24 micrograms of microcystin per liter.
“It’s halfway to the danger level of 6 micrograms per liter and five times last week’s level” of 0.63 micrograms per liter, Thomason said.
At the same time, Gibbs Lake — “probably the most popular swimming lake in the county,” Thomason said — is thick with algae, and the plants are of the type of algae known to produce microcystin.
Test results lag a week behind the actual conditions in the lake, since they are announced Fridays for samples taken Mondays.
That means the lake could be producing more toxin now than has been measured.
Although microcystin, a liver toxin, is fatal only after many years of ingestion, it can cause immediate discomfort.
Skin irritation
“In the short term, it can produce skin irritations, a rash, hives, itching and burning of the skin,” Thomason said.
Thomason said he warned the swimmers Thursday to try not to get the water in their mouths.
“You just don’t want to get it in your body,” he said.
The swimmers were in the algae scum, which should be avoided, Thomason said.
“The scum is thicker than anything we’ve seen at Anderson Lake,” Thomason said.
Good news
At Anderson Lake, which historically has had the highest level of algae toxins in East Jefferson County, the news is good.
Test results from samples taken Monday show that toxins levels remain low in Anderson Lake, which is in Anderson Lake State Park near Chimacum.
“So [the lake] will remain open” for the Labor Day weekend, Thomason said.
Anderson Lake was reopened Aug. 27 after having been closed since June 10 because of high levels of anatoxin-a, a fast-acting nerve poison that can cause convulsions and death by respiratory paralysis.
The park around the lake has never been closed to recreation.
The latest Anderson Lake sample test results showed a level of 0.28 micrograms per liter for anatoxin-a, well below the safety threshold of 1 microgram per liter, and 0.47 micrograms per liter of microcystin.
“So the lake stays open, but the ‘caution’ signs stay up because we still have toxic algae in the lake,” Thomason said.
Lake Leland north of Quilcene tested below detectable levels for both toxins, but a “caution” sign is posted because it has a slight bloom.
Silent Lake on the Toandos Peninsula was not sampled this week. A caution sign remains posted there because of algae in the lake.
Sandy Shore Lake south of Port Ludlow remains clear.
Blue-green algae growth itself is thought to be encouraged by warm, sunny weather when sufficient nutrients, such as phosphates, are present.
So the warm weather expected during the Labor Day weekend is likely to fuel algae growth.
That doesn’t necessarily mean toxins will increase.
Researchers don’t understand why some species of blue-green algae will begin to produce toxins, nor what fuels increases in the amount of toxins.
Shallow, aging lakes are more likely to become overgrown with algae and contain toxins.
The two algae-created toxins seen in East Jefferson County are anatoxin-a and microcystin.
Anatoxin-a is fast-acting. It can kill quickly if a high concentration is ingested.
That’s the toxin blamed for the death of two dogs Memorial Day in 2006, the event that sparked the first closure of the lake and subsequent weekly samplings.
That toxin remains low in Gibbs Lake. The latest test found 0.02 micrograms per liter of water.
Microcystin can kill but only after long-term, constant exposure, such as drinking lake water tainted with the toxin for many years, Thomason said.
However, it is a skin irritant.
“If your skin starts to itch and burn, get out of the water,” Thomason said.
“Watch little kids, and don’t let them drink the water,” he added.
Clallam County lakes, most of which are deep and relatively free of algae, are not tested for toxins.
To report algae blooms in Clallam County, phone 360-417-2258.
Information about Jefferson County lake quality is posted at http://tinyurl.com/6z64ofy.
To report blooms in Jefferson County, phone 360-385-9444.
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Managing Editor/News Leah Leach can be reached at 360-417-3531 or leah.leach@peninsuladailynews.com.
