PORT TOWNSEND — Gibbs Lake is closed to swimming, fishing and boating until further notice because of high levels of microcystin, a toxin created by cyanobacteria.
Jefferson County Public Health (JCPH) announced the closure of the lake on Friday after water samples taken Monday found a toxin level of 46 micrograms per liter, which is more than five times above the Washington state recreational criteria of 8 micrograms per liter, according to a press release.
The rest of Gibbs Lake County Park remains open for hiking, biking and horseback riding.
Microcystin can cause skin irritation, nausea and muscle weakness if touched and liver damage if swallowed over a long period of time in people and in animals.
It is produced by cyanobacteria, also known as blue-green algae. Blue-green algae, which occurs naturally, can begin at times to produce toxins in a process researchers still don’t understand.
Visitors are urged to keep pets out of the water. JCPH has posted warning signs at lake access points and signboards.
JCPH has monitored local lakes for cyanobacteria seasonally since 2007. Monthly monitoring of Anderson, Gibbs, and Leland lakes began in April of this year, the release said.
Anderson Lake closed in May due to high levels of anatoxin-a, a potentially lethal nerve toxin, which also is produced by blue-green algae. The state park around the lake remains open.
Low concentrations of microcystin and no anatoxin-a were detected in Lake Leland on July 6.
JCPH urges people to avoid contact with heavy algae blooms or scums.
People who observe a bloom in a Jefferson County lake are asked to report it by calling 360-385-9444.
To check the status of Jefferson County Lakes and learn more about toxic cyanobacteria monitoring, people can visit the JCPH website at www.jeffersoncountypublichealth.org or call 360-385-9444.
Toxin-producing blue-green algae has not been spotted in Clallam County.
Report algae blooms in Clallam County by phoning 360-417-2258.
