SAN MATEO, Calif. (KRON) – On the Peninsula signs posted at one San Mateo County beach are warning people of toxic algae in the water. They say exposure can cause a sore throat, nausea and other health issues.

Algae visible along the path to San Gregorio State Beach on friday. Posted signs warn beach goers against going into the creek.

Heather Forshey, San Mateo County director of environmental health services tells KRON4, “if you see stagnant water with visible signs of algae you should be concerned. In this particular case, there was a positive for toxic algae bloom.”

Forshey says, “exposure to humans can cause a rash, vomiting, diarrhea, cold and flu like symptoms.” The algae also poses a threat to pets, symptoms include: vomiting, diarrhea, weakness, difficulty breathing and seizures or death.

That’s why Forshey is urging people to be mindful of the water and banks of the lagoon and creek. “We want everyone to avoid swimming in it and allowing their pets in the water or even touching the algae. It’s not safe,” she told KRON4 News.

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Forshey says these conditions that have been popping up around the Bay Area are most likely caused by the drought. She says, “cyanobacteria in algae tend to grow in the warm summer months when the water is warmer and the water flow is slower.”

“There isn’t a lot of flow and the water has been sitting there,” Forshey explains, “ it’s been stagnant for quite a while and so the algae is growing pretty thickly down in that area.”

Forshey tells KRON4 that the next water sampling event for San Gregorio State Beach is scheduled for mid August.