An algal bloom in Lake Elsinore prompted the city and state Tuesday to warn swimmers to stay out of the water and others engaged in recreational activity to take precautions to minimize exposure to the green slime.

According to the California Water Resources Control Board, the bloom appeared last week and poses a potential health threat to people and pets.

“No swimming” signs have been posted around the water, with additional warnings not to let dogs drink from the lake or eat scum washing up on shore. Fish caught in the lake should be properly gutted and the fillets cleaned with tap or bottled water, officials said.

“Cyanobacteria, a group of organisms that form harmful algal blooms, can produce potent toxins,” according to a Water Resources Control Board statement. “Health risks include skin inflammation, gastrointestinal distress, headaches, agitation and weakness or abnormal breathing if … material is swallowed while swimming.”

Blooms have appeared in the lake in previous years, and according to officials, the current one is suspended at the surface.

Algal growth is attributed to higher volumes of nutrients in the water, combined with elevated temperatures, lots of sunshine and little to no wind.

“Bloom conditions can change rapidly, as the winds and waves move or concentrate the bloom into different regions of the lake,” the WRCB stated. “In some areas, the bloom may concentrate and form a film or scum on the water surface. The color of the water may also appear discolored as bright or dark green and brown.”

Officials could not say when conditions might change on the lake.

Additional information is available at

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