Testing shows persistent toxic algae bloom at Clear Lake in Thurston County

People should avoid Clear Lake in southeast Thurston County due to an ongoing toxic algae bloom, according to Thurston County Public Health and Social Services.

Lab results from a sample taken on Oct. 25 showed microcystin levels were greater than 10 micrograms per liter, according to a Wednesday news release. That’s more than the state advisory level of 8.0 ug/L. PHSS staff issued a health advisory for Clear Lake on Aug. 31 and has been regularly testing the lake since then.

The release said the advisory for the lake will remain in effect until two weeks of consecutive sampling show results below advisory levels. In the meantime, people will continue to find warning signs at the boat launch.

Clear Lake is a 181-acre lowland lake southeast of Lake Lawrence. It’s typically open for fishing from the fourth Saturday in April to Oct. 31, according to the Washington state Department of Fish and Wildlife.

Microcystin is a liver toxin that may cause cancer in humans and illness in livestock and pets that drink affected water.

In the event of a toxic algae bloom, health officials advise people to avoid swimming, wading, wind surfing and water skiing. Those with boats should avoid areas with scum, and anglers should not eat fish that come from the lake, officials say.

People who contact water during an algae bloom can develop stomach pain, vomiting, diarrhea and allergic reactions, according to PHSS. More information on harmful algal blooms can be found on the PHSS website.