PORT TOWNSEND — The latest samples from Anderson Lake contain more than 1,000 times the safe level of a potent neurotoxin, the highest level of the algae-created poison seen at the popular fishing hole since it set a deadly world record in 2008.
Test results received Friday showed 1,112 micrograms per liter of anatoxin-a, for which the safe level is 1 microgram per liter.
“It’s the most since 2008,” said Greg Thomason, Jefferson County environmental health specialist.
In 2008, Anderson Lake water contained 172,640 micrograms per liter of anatoxin-a.
“That’s a world record,” Thomason said. “It’s still a world record.”
Although 1,000 times less than in 2008, the amount of anatoxin-a now in Anderson Lake is still more than enough to kill, Thomason noted.
Anatoxin-a acts quickly on the nervous system. In lethal amounts, it kills both people and animals through respiratory paralysis.
Anderson Lake “is a good place to not get near the water,” Thomason said.
The amount of toxin in Anderson Lake has increased in geometric leaps since
June 10, when the lake was closed to fishing, swimming and any kind of recreation after samples taken June 6 contained 2.67 micrograms per liter of anatoxin-a.
Test results of samples taken June 13 showed a concentration of 7.37 micrograms per liter.
Although the 70-acre lake is posted with red closure signs, the 410-acre park surrounding it remains open.
Hiking, horseback riding and biking — all recreation not related to the lake — are permitted in Anderson Lake State Park, which is between Chimacum and Port Hadlock.
A warning sign remains posted at Lake Leland, which tested at 0.275 micrograms per liter of anatoxin-a, while tests found the toxin to be below detectable levels in Gibbs and Silent lakes.
Caution signs are posted at Gibbs and Silent lakes because both contain algae known to produce toxins at times, even though the algae remains benign for now.
Leland, Gibbs and Silent lakes are all open for fishing.
Fish that have been cleaned with the guts discarded can be eaten from lakes posted with either caution or warning signs.
The difference is that the caution sign notes that toxic algae may be present, and that swimmers should avoid scums, while the warning sign reads toxic algae are present and warns against any swimming at all.
In both cases, lake water should not be consumed.
Sandy Shore Lake, which was last sampled for testing July 13, remains clear, Thomason said.
For the first time this season, another toxin created by blue-green algae, microcystin, has shown up in lakes in Jefferson County.
Microcystin, which can damage the liver, was found in a concentration of 6.5 micrograms per liter in Anderson Lake.
The safe limit for microcystin, a slower-acting toxin than anatoxin-a, is 6 micrograms per liter, Thomason said.
The liver toxin also was found in last wee’s test results for the first time this year in Gibbs Lake, although the level — 0.057 micrograms per liter — was barely detectable and is not a hazard.
Researchers don’t fully understand why blue-green algae will begin to produce toxins nor what fuels increases in the amount of toxins. Algae growth itself is thought to be encouraged by warm, sunny weather when sufficient nutrients, such as phosphates, are present.
But Anderson Lake’s huge increase in toxins last week — in which anatoxin-a was found in greater concentrations than at any time in the 2009 or 2010 — cannot be explained by the weather.
“It’s still cooler than normal and cloudier than normal,” Thomason said.
“Why this year such a high level when the last two years had sunnier weather and warmer temperatures?” Thomason asked. “It’s tied in with sun and daylight, but it’s not the whole picture. We don’t know what’s causing it.”
Anderson Lake has been plagued with deadly toxins since 2006, when two dogs died on Memorial Day after drinking lake water with a heavy concentration of anatoxin-a.
That was the first year the lake was closed for the fishing season.
In April 2010, Anderson Lake was opened for fishing for the first time since 2008 but was closed three weeks later.
The highest levels [of toxins] historically have been in May and June, Thomason said.
“It seems to drop off after that, although it’s still high enough to keep people out of the lake.”
Anyone who observes an algae bloom at a lake is urged to phone the Jefferson County Public Health Department at 360-385-9444.
For more information about lake quality in Jefferson County, visit the environmental health website at http://tinyurl.com/6z64ofy.
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.
Algae blooms in Clallam County lakes should be reported to the Clallam County Department of Health and Human Services’ environmental health division at 360-417-2258.
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Managing Editor/News Leah Leach can be reached at 360-417-3531 or leah.leach@peninsuladailynews.com.