LAKE COUNTY, Calif. – A seasonal blue-green algae bloom has reemerged in several areas on Clear Lake and has prompted Lake County Health Department officials to post precautionary advisory signs at two impacted public beaches in the City of Clearlake: Austin Park and Highlands Park.

The seasonal blooms have been observed in areas of the Northshore, near Lakeport, in Soda Bay, and in southern sections of the lake where prevailing winds tend to cause localized accumulation of algae, which form a filmy layer or mats on the water’s surface.

State guidelines call for the posting of areas where there is visible build-up of film or mats. The majority of the lake remains open for recreation.

Lake County Health Officer Dr. Karen Tait recommended that people and pets stay out of areas where visible algal mats are present and avoid swimming or wading in the immediate vicinity.

Tait also emphasized that untreated lake water should never be used for drinking.

While several species of blue-green algae – also known as cyanobacteria, which is not a true algae – are present in Clear Lake, the mix of algae types fluctuates.

Based on periodic testing being done on the lake water, only minimal and mostly no measurable toxins have been detected.

“It is best to err on the side of caution by avoiding contact in areas where blue-green algae mats are visible,” Tait said.

Preparations for mitigating this seasonal bloom began several weeks prior to the first sighting of algae.

Staff in the Lake County Department of Water Resources entered into contracts with specialized contractors who now are working to help minimize the impacts in the most affected areas, especially at public access points.

Clear Lake’s large drainage basin, shallow depth, and warm summertime water temperatures contribute to its rich nutrient content that supports the growth of algae and aquatic plants, which in turn, supports large populations of fish and wildlife, county officials reported.

With more than 68 square miles of surface area and 100 miles of shoreline, Clear Lake is the largest natural freshwater lake within the boundaries of California, and at an estimated two million years old, it also is one of the oldest lakes in North America.

For more information about the algae bloom and efforts to mitigate its impacts, contact the Lake County Department of Water Resources at 707-263-2344.

For health-related questions or for assistance regarding posting of advisory signs on private property, contact the Lake County Health Services office at 707-263-1164.

For more information regarding blue-green algae, visit the following sites:

http://www.co.lake.ca.us/Government/Directory/Environmental_Health/Blue-Green_Algae.htm
http://www.cdph.ca.gov/HealthInfo/environhealth/water/Pages/Bluegreenalgae.aspx
http://water.epa.gov/scitech/swguidance/standards/criteria/nutrients/cyanohabs.cfm .