Warning sign at Lake Mendocino boat ramp cautions visitors about harmful algae, advising against drinking the water, eating shellfish, or letting pets near algae or scum.
Signs warning of harmful cyanobacteria, or blue-green algae, are posted at a dock at Lake Mendocino near Ukiah, Calif. on Thursday, Aug. 28, 2025. Harmful blooms were reported in the reservoir on Thursday resulting in a lake-wide warning about the algae, which if ingested can cause nausea, vomiting or diarrhea in people and death in pets. (U.S. Army Corps of Engineers via Bay City News)

MENDOCINO CO., 8/29/25 — Low concentrations of harmful cyanobacteria, or blue-green algae, have been detected in Lake Mendocino near Ukiah, the U.S. Army Corps of Engineers said Thursday. 

According to the Army Corps, the current bacteria levels do not pose a significant health risk to people or pets, despite signs dotting the shorelines asking that people and pets stay away from the algae.

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Laytonville resident Lin Due edits and writes for the Mendocino Voice.

Sarah Stierch covers breaking news and more for The Mendocino Voice. Reach her at sarah@mendovoice.com.