Peninsula Daily News
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A water sample taken Jan. 16 from the 492-acre lake was tested for potentially lethal toxins after blue-green algae appeared.
Those tests determined that the algae contain extremely low levels of toxins — low enough that county officials lifted recommended restrictions that were put in place last week for recreational use of the West End.
A lab determined that the level of toxic microcystin was 0.0645 micrograms per liter, which is nearly 100 times lower than the 6 micrograms per liter that is considered to be unsafe.
High doses of microcystin can cause liver damage over long-term ingestion of water containing high amounts.
The same water sample showed 0.0201 micrograms per liter of anatoxin-a, or roughly 50 times lower than the 1-microgram-per-liter threshold used for closures.
High doses of anatoxin-a can cause paralysis, seizures and respiratory failure.
Blue-green algae comes in both toxic and non-toxic forms.
“The testing results from Lake Pleasant indicate that most of the blue-green algae is of the non-toxin-producing form, but a small percentage is capable of producing the harmful toxins,” Clallam County environmental health officials said in a statement.
“Based on current test results, Clallam County Health and Human Services is recommending no restrictions on recreational use of Lake Pleasant at the present time,” it continued.
Lake Pleasant is located about 8 miles northeast of Forks just off U.S. Highway 101. It has a year-round open fishing season for trout and kokanee.
Last week’s recommendations were to avoid swimming in scum, to not drink the water, to keep pets and livestock away, and to clean fish well.
Pet owners still are advised to keep their animals from drinking from Lake Pleasant when blue-green algae is visible from the shoreline.
The greatest risk of toxin exposure comes from ingesting the algae itself.
Environmental health officials said it is unusual for blue-green algae blooms to occur during the winter — and very rare to find blue-green algae in Clallam County lakes.
The same type of algae has caused summertime closures of the 57-acre Anderson Lake — and occasional warnings in other lakes — in East Jefferson County.
Clallam County Health and Human Services officials said they will continue to monitor algae blooms in Lake Pleasant through the spring and summer.