All water activities, including fishing, have been closed at Anderson Lake State Park in Jefferson County.
The state park will remain open for picnicking, hiking, biking and horseback riding.
The Jefferson County’s health department found high levels of the nerve toxin anatoxin-a in water samples taken on Friday, May 9.
The toxin occurs in blue-green algae that periodically blooms in the lake south of Port Townsend, which has been closed off and on since the county started monitoring for the algae in 2007.
Anderson Lake had just opened on April 26 for lowland trout fishing.
The lake will reopen after county health department tests show that water quality is safe for recreation. People are asked to also to keep pets out of the lake.