San Luis Reservoir is not safe for swimmers because of a big bloom of blue-green algae, state authorities warned Tuesday.
People looking to enjoy a day at the Merced County reservoir can safely ride atop the water in boats but must avoid any contact with the water, said the California Department of Water Resources, which issued the health warning. The alert will remain in place until further notice.
Danger signs are posted at the Basalt and Dinosaur Point boat launches. O’Neill Forebay, next to the reservoir, is not affected by the alert.
Exposure to toxic blue-green algae, also known as cyanobacteria, can cause eye irritation, allergic skin rash, mouth ulcers, vomiting, diarrhea, and cold- and flu-like symptoms. Pets can be especially susceptible because they tend to drink while in the water and lick their fur afterward.

Take Precautions Near Algae Bloom

Algae bloom conditions can change swiftly, with wind or waves shifting the bloom or changing its concentration.
The water resources department recommends that people near a body of water with algae bloom take precautions:

• Ensure that pets and livestock do not drink the water, swim through algal blooms, scum, or mats, or lick fur after going in the water. Rinse pets in clean water to remove algae.
• Avoid wading, swimming, jet-skiing or water skiing.
• Don’t drink, cook, or wash dishes with untreated surface water. Common purification techniques such as camping filters, tablets, and boiling don’t remove toxins.
• Don’t eat mussels or other bivalves collected from the area. Limit or avoid eating fish. If fish are consumed, remove the guts and liver and rinse filets in clean drinking water. If the area is under a danger advisory, don’t eat fish at all.
• Get medical treatment immediately if you think that you, a family member, friend, pet, or livestock might have been poisoned by blue-green algae toxins.