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Anatoxin from Algae Detected in Blue Lakes

LAKE COUNTY, CA (December 19, 2019) – Following recent rains, an algae bloom was noted in the southern edge of Blue Lakes on December 12.  Samples were collected and sent for testing.  The laboratory has confirmed a low level of a toxin called anatoxin at 0.17 µg/l.  This is a chemical produced by the algae that can cause severe nerve problems.  Caution signs have been posted in the affected area, in accordance with State recommendations responsive to detection of any level of anatoxin.

We at Public Health recommend the public take note of the bloom and the presence of the anatoxin.  Small children and pets are especially at risk; please keep children and dogs away from the material on the beach and avoid letting them swim or play in the water until this bloom subsides.

Under a Caution advisory, fishing is allowed but our guidance is to throw away the guts (and liver) and clean and rinse the fillets with tap or bottled water before cooking.  Shellfish should not be eaten under a Caution advisory.

The Clear Lake cyanobacteria monitoring program run by the Big Valley Band of Pomo Indians and Elem Indian Colony funded the analysis.  Their program has been routinely collecting a water sample at the Upper Blue Lakes as part of their monitoring program.  Further testing will be performed in order to monitor ongoing risk.  This program has been highly beneficial to the health of our community.
For more information, the Water Boards posts information about the bloom on the State Water Boards twitter page:

For current cyanotoxin lab results, please visit the Big Valley Band of Pomo Indians cyanotoxin monitoring website:

For more information and resources, visit the County’s cyanobacteria pages:


Water Faucet
Urgent Health Advisory

Effective immediately, people on private water systems whose tap water comes from their own private intake into the lake, in the Oaks Arm and Lower Arm of Clear Lake should not drink the water.

More info