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Warning signs posted at Lake San Antonio due to algae bloom

Public advised to stay out of lake after dangerous cyanotoxins detected

Lake San Antonio (Monterey County)

SOUTH MONTEREY COUNTY — Monterey County Public Works, Facilities and Parks has posted “DANGER” warning signs at Lake San Antonio South Shore due to dangerous cyanotoxins detected in the lake.

Prior to every major summer holiday weekend, water testing at Lake San Antonio is performed by the California Central Coast Regional Water Quality Control Board.   

In anticipation of the Labor Day weekend, samples of Lake San Antonio South Shore surface water were collected on Aug. 23. Test results were received by Monterey County on Sept. 1.

Cyanotoxins — toxins produced by blue-green algae — were detected at both sampling locations, which requires that a “DANGER” level warning to be issued for the entire lake.  

The Regional Water Quality Control Board advises the following:

  • Stay out of the water until further notice;
  • Do not let pets and other animals drink or go into the water or go near the scum;
  • Stay away from scum, and cloudy or discolored water;
  • Do not eat fish or shellfish from this water; and
  • Do not use this water for drinking or cooking. Boiling or filtering will not make the water safe.

For more information relating to harmful algae blooms, and information about what to do if advisory signs are posted, visit this link.