The level of a slow-acting liver toxin created by blue-green algae is now over the safety threshold at Gibbs Lake south of Port Townsend, preliminary results of the most recent lake sample tests show.
“Toxin levels have been creeping up at Gibbs Lake and [it] is at a ‘warning’ status, which means we don’t recommend that people swim there or have contact with the water right now,” said Mike Dawson, Jefferson County environmental health specialist.
“Microcystin is rising and is over the recreational guideline, it appears,” he said.
Preliminary results show 6.8 micrograms per liter of microcystin in Gibbs Lake.
The recreational safety threshold is 6 micrograms per liter.
Final results of tests of water samples taken last Monday were not available Friday, Dawson stressed, saying he had only preliminary results from King County Environmental Labs, and that the numbers might change when they are finalized.
Microcystin can damage the liver after longtime ingestion.
The posted status of lakes in East Jefferson County did not change last week after initial test results were received.
Toxin levels at Anderson Lake — historically the worst for high levels of anatoxin-a, a fast-acting nerve poison that can be fatal — remain low, Dawson said, and no bloom is visible on it now.
It remains open to fishing and other recreation, but is posted with a “caution” sign because of the existence of some toxins in the water sample taken last week, he said.
The lake near Chimacum, which is in Anderson Lake State Park, was reopened Aug. 27 after having been closed since June 10 because of high levels of anatoxin-a, which can cause convulsions and death by respiratory paralysis.
Anderson Lake State Park, which is around the lake, has never been closed to recreation.
Lake Leland north of Quilcene remains posted with a “caution:” sign because of a slight algae bloom and because small amounts of toxins and toxic species are present there.
Silent Lake on the Toandos Peninsula is posted with a “caution” sign because of algae in the lake.
Sandy Shore Lake south of Port Ludlow remains clear.
Blue-green algae growth itself is thought to be encouraged by warm, sunny weather when sufficient nutrients, such as phosphates, are present.
But researchers don’t understand why some species of blue-green algae will begin to produce toxins, nor what fuels increases in the amount of toxins.
Shallow, aging lakes are more likely to become overgrown with algae and contain toxins.
The “warning” level means people should not swim in the lake or drink its water, that pets and livestock should be kept away from it, boaters should avoid scums and fish should be well-cleaned, with the guts discarded.
The “caution” recommendations are the same except swimming should be avoided only in areas of scum.
Clallam County lakes, most of which are deep and relatively free of algae, are not tested for toxins.
To report algae blooms in Clallam County, phone 360-417-2258.
Information about Jefferson County lake quality is posted at http://tinyurl.com/6z64ofy.
To report blooms in Jefferson County, phone 360-385-9444.
________
Managing Editor/News Leah Leach can be reached at 360-417-3531 or leah.leach@peninsula
dailynews.com.
