Pass Lake is closed to all activities due to dangerous levels of blue green algae.

Recently tested water samples from the lake showed anatoxin-a levels exceeding state recreational guidelines.

“It’s really, really bad,” said Deception Pass State Park Manager Jason Armstrong. “I mean really, really high levels.”

Armstrong takes the water samples personally and overnights them to a lab.

The preliminary result from the lab was 2,576 micrograms per liter of anatoxin-a in the water sample taken from Pass Lake. According to the state Department of Health, the level of public health concern for anatoxin-a is 1 microgram per liter.

The submitted sample was taken Thursday from the boat launch area and Armstrong received the test results Monday.


“The approach we took is because of (Pass Lake’s) history and its extreme high levels we decided this year to move forward with a more aggressive response and close it,” Armstrong said.

Anatoxin-a is an acute neurotoxin that can be harmful to humans and animals. Even short-term exposure is a concern.

Levels of the neurotoxin at Pass Lake have been above state guidelines 13 times since 2019, and a year ago they led to a closure of the lake.

Armstrong said in his three years at the park, these blooms arise following the same pattern.

“It’s hot for a long stretch of time,” he said. “Then the rain causes a turbulence that stirs up the lake and that algae rises to the surface. Then it gets hot again and then it explodes.”

Signs of neurotoxin poisoning appear within 15 to 20 minutes of ingestion, and may include numbness of the lips, tingling in fingers and toes, and dizziness. The neurotoxin can kill animals or cause weakness, staggering, difficulty breathing and convulsions in them.


Due to the extended warm weather this summer, activity at Pass Lake has increased. Armstrong said just the sheer numbers of swimmers and paddle boarders that show up at the lake was cause for concern, along with the potential for animal exposure.

“Other lakes in Washington have had those experiences where a family loses a beloved family pet, and I do not want to have anyone experience that or worse here,” Armstrong said.

It’s a deadly situation for pets who swim, drink and then lick their fur to clean themselves.

“They go into a neurological shutdown and respiratory failure and there is nothing veterinarians can do for it,” Armstrong said.

Until the toxin levels are back within state recreational guidelines, signs will be posted at the lake advising people to keep themselves and their pets out of the lake, and avoid fishing and drinking the water.

With the number being so high, Armstrong said he will not be taking another sample for some time.

“That number is not going to drop to an allowable one in a week,” he said. “It’s just too large and it’s probably going to go up even more.

“It’s going to be around two weeks before I test again. Then once we start to see that number reducing, we will start to test every week.”