Most toxic lake in all of Washington?

Carmen Jaramillo
Posted 5/22/19

The main toxin affecting Anderson Lake is known as Anatoxin-a, and last week it was measured at almost 5,000 times the state’s acceptable level for recreation: one microgram per liter.

“It’s …

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Most toxic lake in all of Washington?


The main toxin affecting Anderson Lake is known as Anatoxin-a, and last week it was measured at almost 5,000 times the state’s acceptable level for recreation: one microgram per liter.

“It’s a particularly dangerous toxin,” Michael Dawson, water quality manager at Jefferson Environmental Health said. “It affects both animals and humans and it acts very quickly.”

Another common name for Anatoxin-a in science literature is “VFDF,” which is short for “very fast death factor.” According to the U.S. Environmental Protection Agency, harmful algal blooms occur in all 50 states and pose serious risks to public health, natural ecosystems and by extension local economies.

The “algae” is not really algae but cyanobacteria, a single-cell organism. Blooms occur when cyanobacteria grow exponentially due to changing water temperatures, increased sunlight or increased levels of nutrients such as nitrogen or phosphorus. The cyanobacteria may then produce one or multiple kinds of toxins.

Officials at Jefferson Environmental Health and the Washington State Department of Ecology say they don’t really know how the toxins are affecting local wildlife. Geese and swallows have been observed drinking from the lake but there is currently no evidence of wildlife deaths as a result of the toxic water.

Last week, at Lake Minterwood south of Port Orchard, another toxin, Microcystin, was measured at 137 micrograms per liter, about 23 times the state’s acceptable level of 6 micrograms per liter. No other lake in Washington is currently showing Anatoxin-a or any other dangerous toxins with levels as high as Anderson, and no other lake in Washington is currently reported to be experiencing a dangerous bloom.

Anderson Lake has previously measured above the state limit for Microcystin but as of the last reading is still below the limit.

Dawson said a grant from the Washington Department of Ecology is funding research into the causes of the blooms at Anderson Lake, in order to create a science-based lake management plan. Solutions could range from addition of a mineral to take phosphorus out of the water, to solar-powered stratification or circulation of the water. The study is on track to be finished by the end of 2019, he said.

Even if a credible solution is found, he said it may be difficult to secure funding.

According to the Washington State Algae Control Program, blooms in Washington typically occur when temperatures start to rise in spring and summer, but may still occur in winter months. Anderson Lake’s bloom season is typically between April and October, with the most activity in the spring and summer months.

Climate change may be a contributing factor to increased harmful blooms across the nation through increased water salinity, warming temperatures, rising sea levels and rising carbon dioxide levels according to the Centers for Disease Control and the EPA.

Different types of blooms can range in color from blue-green to red or brown and form an oily scum on the surface of the water. Suspected blooms should be reported to Jefferson County Environmental Health at 360-385-9444.

“Avoid contact with these closed lakes,” Dawson said. “If you have an encounter, rinse your skin immediately and head directly to the emergency room.”


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I have lived here for 24 years & cannot remember a time when Anderson Lake was fully usable. All that’s left is trail walking, but unfortunately we know what that led to with the dog who was quickly in & out of the water. Shouldn’t the whole park be shut down until we can get a handle on how to resolve this ongoing problem. If there are no funds available, I guess that means it’s a closed resource until it’s a priority.

Thursday, May 23, 2019