Harmful algae bloom found at San Luis Reservoir in Merced County

MERCED COUNTY, Calif. (KFSN) -- It was an urgent warning Tuesday for people and their pets heading to the San Luis Reservoir.

The Merced County waterway is experiencing a dangerous level of toxic blue-green algae, so the Department of Water Resources issued a danger advisory and it remains in effect until further notice.

Sarge Green, a Research Scientist with Fresno State's Water Institute, urges people to not go inside the water.

"If you see floating materials on the edge of the reservoir, don't go in it, don't drink it and don't let your pets get near it," he said.

Drought conditions and warm weather means algae bloom season on Central Valley waterways.

RELATED: Toxic algal blooms found in Merced River, recreation closures in place

Certain types of blooms can produce toxins that make you and your pets sick.

"There are quite a few viral and bacterial opportunities when you go hiking or whatever, and they always warn you have to treat the water before you drink it," Green said.

The algae can create scum and foam at the surface and along the shoreline, and range in color from blue, green, white, or brown.

RELATED: Toxic algal blooms found in Merced River, recreation closures in place

Sarge says warmer weather due to climate change might make harmful algae a bigger concern not only just around California but also around the country.

The state recommends the following precautions:
  • Don't drink the water
  • Avoid entering the water
  • When camping, do not use untreated water
  • Do not eat the fish or mussels in the lake
  • If you think you may be poisoned, get treatment immediately.


  • "Yes, it's occurring nationwide and it can occur as long as you have that shallow water and the opportunity for the organism to grow in those circumstances," Green said.

    To date, CDPH has no reported human fatalities from cyanobacteria toxin exposures.

    The last time that San Luis Reservoir had a danger advisory was more than two years ago.

    Similar advisories have been issued recently for Hensley Lake in Madera County and the Merced River between Bagby and Briceburg in Mariposa County. Right now, the state is testing the water where a Mariposa family was found dead.

    RELATED: Cause of death still undetermined in case of family found dead in Mariposa County
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