PORT TOWNSEND — The level of a fast-acting nerve poison continued to drop in Anderson Lake, but not fast enough to re-open the popular trout-fishing destination.
The level of anatoxin-a in the lake between Port Townsend and Chimacum dropped to 135 micrograms per liter last week, according to test results received Friday.
The week before, the level of the algae-produced toxin, which can cause convulsions and stop breathing, had been measured at 166 micrograms per liter, which was a big decrease from the prior week’s measurement of 534 micrograms per liter — the highest seen in the lake this season.
But all measurements since the lake was closed May 3 have been above the warning level of 1 microgram per liter.
“Nothing has changed,” said Greg Thomason, Jefferson County environmental health specialist, on Friday.
“Anderson Lake stays closed . . . Leland is still safe . . . Gibbs is still very safe,” he summed up.
Only the lake in Anderson Lake State Park is closed to recreational use. The 410 acres surrounding it remain open. A Discover Pass is needed to park there.
A trace of anatoxin-a was found in Lake Leland, north of Quilcene. None could be found in Gibbs Lake, north of Port Townsend.
No microcystin was found in Anderson Lake or Lake Leland. A trace was found in Gibbs.
Microcystin can cause skin irritation and, if ingested over a period of many years, can result in liver failure.
Toxins are created by blue-green algae, which is generally benign, but some species can begin to produce toxins at times.
Sunny weather and warm temperatures encourage the growth of blue-green algae when sufficient nutrients, such as phosphates, are present, but researchers don’t know what triggers the production of toxins.
Caution signs remain posted at both Leland and Gibbs lakes because they contain algae known to sometimes suddenly begin to produce toxins.
A caution sign remains at Crocker Lake because it, too, contains algae known to produce toxins.
Samples are taken on Mondays and results are received from King County Environmental Labs at the end of each week, usually on Friday.
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.
Managing Editor/News Leah Leach can be reached at 360-417-3531 or at leah.leach@peninsuladailynews.com.