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STOCKTON, Calif. (KTXL) — Harmful algae blooms are back in San Joaquin County and health officials are warning people to stay out of the water. 

The toxic blue-green algae can be dangerous for people, pets and wildlife. It occurs year after year, but Stockton residents say the green sludge is a sight they will never get used to seeing. 

Nicholas Thompson and Janett Barron were walking along Morelli Park in downtown Stockton and say the color of the water caught their eye. 

“It looks lime-green with brown in it. Doesn’t look very appealing right now,” Thompson said. 

Those patches of blue-green algae are appearing along the edges of McLeod Lake and washing up on boat ramps. 

“I wouldn’t let my kids in the water. Honestly, I feel like we need to take better care of the environment, more than anything,” Barron said. 

San Joaquin County Public Health Services put up signs around the Delta warning of the dangers of the toxic algae. 

“It’s great that they have the warning signs up, but when people know that an area is at the dangerous level, we would really like to see them not boating out of that area,” said Barbara Barrigan-Parrilla, executive director of Restore the Delta. 

She says the algal blooms are a public health concern. 

“You know they are dangerous to people. They can cause nausea; they can cause liver damage in small children. They can kill dogs. They can cause nerve damage or rashes,” Barrigan-Parrilla said. “So, it’s not just that you don’t like them or the water doesn’t look pleasant, it’s that they are a public health threat. They also cause air pollution.”

The toxic algae blooms are caused by the combination of rising water temperatures, pollution and the lack of freshwater flow through the Delta system.

Barrigan-Parrilla says prevention is possible if the state moves forward with the Bay-Delta water plan, which would protect water quality in the region. 

“We have to have regular cool water temperatures to keep water circulating in the Delta to prevent harmful algal blooms,” Barrigan-Parrilla explained. 

To view a map of toxic algal blooms throughout the state, click or tap here.