PORT TOWNSEND — Anderson Lake, green with algae scum, is so toxic it’s in a class by itself in Jefferson County.

“If we had a different warning level beyond red, we would have given it to Anderson,” said Neil Harrington, county water quality programs manager, Friday afternoon.

“Anderson is a mess,” he said. “Literally, it’s very green. It’s been undergoing an ongoing bloom all summer.

“It’s sort of the lake that won’t stop.”

Warning levels for Anderson — which is within Anderson Lake State Park between Port Hadlock and Chimacum — Lake Leland, north of Quilcene and south of U.S. Highway 101, and Gibbs Lake in Chimacum remained unchanged after test results of last Monday’s water sampling came in Friday.

Anderson and Leland still have red warning signs posted, while a yellow warning sign is posted at Gibbs.

The postings are based on weekly water samples of some lakes in Jefferson County. The samples test for the amount of blue-green algae and toxins.

Blue-green algae is a common freshwater scum that can, at times — for reasons researchers don’t understand — begin producing toxins that can damage human and animal livers or neurological systems.

What does red mean?

But Leland isn’t anywhere nearly as clogged with poisonous blue-green algae as Anderson, Harrington said.

The threat isn’t quite as great because Anderson has at times been an incredibly toxic lake,” Harrington said.

While Anderson is closed by State Parks to all forms of recreation, Leland is not — even though both are posted with red warning signs.

“Our warning is against swimming in the lake” or drinking the water from Lake Leland, Harrington said.

“In terms of boating or other recreation in which people are not running the risk of ingesting the water, it’s OK.”

The Jefferson County Health Department doesn’t have the jurisdictional authority to close Leland, Harrington added, saying it is fortunate that the lake that has the worst infestation of any of those tested by the county health department — Anderson — is under the authority of the state agency.

“State Parks has prohibited people from going on [Anderson Lake],” he said.

The decision was “based on the history, that this lake was shown to kill good-sized animals, and through conferring with risk managers and with us.”

Two dead dogs

Two dogs died after drinking Anderson Lake water in June 2006. That was the first time the lake was closed to use.

Each year since, it has been closed for periods of time during warmer months.

This year, the popular trout lake was closed earlier than ever before — on April 25, just before the opening of the fishing season.

Leland was closed because of toxic algae in mid-May, but the levels have never been as high as those of Anderson.

“We haven’t seen nearly the same toxicity in Leland as Anderson, but we don’t want people ingesting water,” Harrington said.

So why is Anderson so toxic?

“Comparing data among the four lakes we look at, the levels of blue-green algae are directly correlated with the level of phosphorus in the lakes,” Harrington said, explaining that phosphorous tends to be the limiting factor in freshwater plant growth because it typically is the first nutrient to be depleted.

“For whatever reason, Anderson has more phosphorous than any other lake that we’ve tested,” he said.

“Leland is higher than Gibbs, and Gibbs is higher than Sandy Shore,” which is clear.

The origin of Anderson Lake’s high phosphorus content remains a mystery.

Phosphorus is an ingredient in fertilizers and can be in septic-system effluent.

“State Parks has done no fertilizing, and the septic system is in good shape. So that’s probably not it,” Harrington said.

Phosphorus can get into lakes through the atmosphere, through runoff, through some other aspect of the environment or it could be historical.

“I’m checking historical records to see if there was a source for phosphorus in past,” Anderson said.

Whatever the source, phosphorus tends to concentrate in Anderson Lake because it has no outlet.

“It’s a big pond. Any phosphorus that’s in there stays in there,” Harrington said.

By comparison, Sandy Shore Lake is the headwaters of Thorndyke Creek.

“The water’s not staying there forever,” Harrington said.

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Managing Editor Leah Leach can be reached at 360-417-3531 or leah.leach@peninsuladailynews.com.