PORT TOWNSEND — Gibbs Lake has been reopened after tests last week found algae-created toxins to be at a safe level.
Toxins remained low in Anderson Lake, but a heavy bloom, thick with scum, convinced State Park officials to keep the lake near Chimacum closed.
Preliminary results from King County Environmental Labs of samples taken Sept. 9 found 0.24 micrograms of microcystin per liter in Gibbs Lake, well below the recreation guideline of 6 micrograms per liter, said Michael Dawson, lead environmental health specialist at the Jefferson County Public Health Department.
Gibbs Lake south of Port Townsend had been closed since July 18 because of high levels of microcystin, which can cause skin irritation, nausea and muscle weakness if touched and liver damage if swallowed over a long period of time.
It is now posted with a caution sign.
Fishing is permitted, but fish should be cleaned well with the guts discarded, and the health department warns that some toxin may be present in the fish tissue.
Visitors also are warned not to drink the water, not to swim or boat in areas of scum and to keep pets and livestock away.
It was the second consecutive sample below the recreational guideline for the toxin. Because toxins can rise quickly, health officials wait for two such tests to confirm low levels before changing the status of a health.
Test results for Anderson Lake also showed low levels in the second consecutive test — 0.08 micrograms of anatoxin-a per liter, below the recreational guideline of
1 microgram per liter, and 0.23 micrograms of microcystin per liter.
The algae bloom has grown heavier since the last observation in August, however, and although the species of algae has not been identified through tests, it appears to be the typical anabaena-dominated bloom for Anderson Lake, Dawson said.
Anabaena is a species of algae that is considered to be responsible for creating anatoxin-a, a potent nerve poison that can kill within four minutes of ingestion.
“Although toxins are low, State Parks has determined that due to the heavy bloom of toxic species, it will keep the lake closed,” Dawson said.
Anderson Lake has been closed since May 17, only three weeks into the fishing season, because of high levels of anatoxin-a.
The 410-acre state park around the 60-acre lake remains open for hiking, biking and horseback riding. A Discover Pass is needed to park there.
No toxins were detected in Lake Leland north of Quilcene, but because of a light bloom, it remains posted with a caution sign.
Both anatoxin-a and microcystin are created by some strains of blue-green algae, also known as cyanobacteria, which are usually benign but which can suddenly begin to poison the freshwater lakes they grow in.
Scientists don’t know why, although they do know that algae growth is fueled by nutrients such as phosphorus, which is usually found in heavy concentrations in Anderson Lake, daylight and warmth.
Testing for toxins was weekly until this year, when the state Department of Ecology cut back to funding only monthly tests.
Toxin-producing blue-green algae has not been spotted in Clallam County.
Report algae blooms in Clallam County by phoning 360-417-2258, while Jefferson County blooms can be reported at 360-385-9444.
For more information about Jefferson County lakes, visit http://tinyurl.com/jeffersonlakequality or phone the office.
Managing Editor/News Leah Leach can be reached at 360-417-3531 or at leah.leach@peninsuladailynews.com.
