CHIMACUM – Anderson Lake State Park was closed Friday night after tests showed toxin levels to be 250 times higher than last year.
Water samples taken from the popular fishing and recreation lake on June 5 were found late Friday night to contain the blue-green algae species known as anabaena, which was producing a toxin called anatoxin-a.
Anatoxin-a is a very powerful neurotoxin that can cause neurological problems in animals and humans as well as gastrointestinal problems in small doses if ingested, said Mike McNickle, director of the Jefferson County Department of Environmental Health.
The amount of toxin present is 5,000 parts per billion.
McNickle said one part per billion is the threshold to close the lake.
Last summer, the lake one mile east of Chimacum was closed after tests found toxins at 20 parts per billion. Two dogs had died after drinking the water on Memorial Day weekend.
“I think we’re back in the cycle that we were in last year,” McNickle said Friday.
He said he had never seen such a high level of toxin in the lake.
“For Anderson Lake, that’s pretty shocking to me.”
The high level of toxin means that half a liter would be a lethal does for a human being, McNickle said.
For a smaller animal, the fatal dose would be much less.
Gibbs Lake, about two miles southeast of the south end of Discovery Bay, has shown signs of blue-green algae but has not tested positive for toxins.
Blue-green algae is present in most bodies of water and usually causes no problems for humans or animals.
But when the right conditions align – the water is calm, relatively warm and overly rich in phosphates and nitrogen, common chemicals in lawn fertilizers – it can bloom into high concentrations.
Aging lakes that are growing shallow and marshy, such as Lake Anderson, tend to provide those conditions, Dr. Tom Locke, health officer for Clallam and Jefferson counties has said.
