PORT TOWNSEND — Anderson Lake remains closed to recreation after the most recent test results showed that the level of a powerful nerve poison in the water increased last week.
The level of anatoxin-a, which can cause convulsions and stop breathing, rose to 17.5 micrograms per liter of water in test results received Friday from samples taken last Monday.
The safety threshold is 1 microgram per liter.
The level of the toxin, which is created by blue-green algae, had fallen to 6.07 micrograms per liter the week before after reaching a high of 70 micrograms per liter the second week of this month to 6.07 micrograms per liter last week.
A moderate bloom remains on the lake, said Greg Thomason, Jefferson County environmental health specialist.
Warm weather may encourage algae blooms in lakes in the days ahead, he said.
“It’s good weather for blooms,” he said.
The 410-acre Anderson Lake State Park, which surrounds the lake, remains open for recreation.
A Discover Pass — which is $10 for one day or $30 for an annual pass, and which can purchased at state parks — is needed to visit state parks.
The lake within the park, which is between Port Townsend and Chimacum, was closed May 3, only a few days after it had opened for the start of the trout-fishing season the last Saturday in April.
Toxins created by blue-green algae have prompted closures of the lake since 2006, when two dogs died Memorial Day weekend after drinking lake water.
In other lakes sampled, only a trace of anatoxin-a was found in Lake Leland, north of Quilcene, with none detected in Gibbs, south of Port Townsend.
Crocker Lake, which is near the intersection of U.S. Highway 101 and state Highway 104, was not sampled last week.
A trace of microcystin — another algae-produced toxin common in East Jefferson County — was detected in Anderson Lake.
None could be found in Leland or Gibbs.
Microcystin can cause skin irritation and, if ingested over a period of many years, can result in liver failure.
Caution signs remain posted at Leland, Gibbs and Crocker lakes because they contain species of algae that are known to sometimes produce toxins.
Researchers know algae flourishes in warm temperatures when sufficient nutrients, such as phosphates, are present, but they don’t understand why some species of blue-green algae begin to produce toxins, nor what makes them increase.
No toxic blue-green algae has been reported in Clallam County, where health officers do not test for toxins. Instead, they visually monitor lakes for signs of algae bloom.
Report algae blooms in Clallam County by phoning 360-417-2258.
Report algae blooms in Jefferson County by phoning 360-385-9444.
For more information about lake quality in Jefferson County, visit the environmental health website at http://tinyurl.com/6z64ofy.
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Managing Editor/News Leah Leach can be reached at 360-417-3531 or at leah.leach@peninsuladailynews.com.
