Danger advisories posted at East Bay lakes over harmful blue-green algae blooms

FREMONT, Calif. (KGO) -- Harmful blue-green algae blooms have the East Bay Regional Park District warning everyone to keep themselves and their pets out of the water.

The danger advisories have been posted at a number of East Bay parks, including Fremont's Quarry Lakes.

From our SKY7 view, an obvious green tint to Livermore's Lake Del Valle is spreading on the first day of spring.

"They're a whole wide bunch of organisms, some of which produce toxins that can be harmful to people or pets or fish," said Jon Rosenfield, Science Director at San Francisco Bay Keeper.

Jon Rosenfield, Science Director at San Francisco Bay Keeper, an environmental watchdog group, says this is called a blue-green algae bloom.

"They bloom particularly when there's enough nutrients, the water is warm enough, there's enough sunlight - but also when the water is moving slowly or not moving at all," he said.

The East Bay Regional Park District has posted a Danger Advisory, urging to keep people and pets out of the water not just at Lake Del Valle, but also at Shadow Cliffs lake in Pleasanton and Quarry Lakes in Fremont.

"Do take it seriously," said William Cochlan, an emeritus biology professor at San Francisco State University's Estuary and Ocean Science Center.

Cochlan says blooms are becoming more common across the globe and they're starting to happen earlier in the year.

MORE: Is it still safe to swim in Bay Area waters amid toxic algae bloom? Experts weigh in

"With increasing water temperatures, and we've seen that all through California that they're inching up due to climate change, that gives these blue-green algae a little advantage over the others," he said.

For Fremont resident Matthew Stewart, that means not taking his toddler to the beaches of Quarry Lakes, despite living within walking distance.

"I know that they opened this stretch of beach over here a long time ago and since my kid was a toddler, I've wanted to take her there, but I haven't because it's been closed ever since," he said. "Minor disappointment, but that's how it's been."

But Rosenfield says if the bloom becomes big enough to drop oxygen levels in the water, fish will be at risk next, similar to the red tide algal bloom that happened in Lake Merritt two years ago, which killed off thousands of fish.

"They can last all summer but they're starting now," Rosenfield said. "As long as they have nutrients, the nitrogen and phosphorus fertilizer, that they need to grow and reproduce, they'll keep growing."

You can track the current water status of lakes at East Bay parks here.

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