Dead fish pile up in Lake Merritt, on the shores of San Francisco Bay, and algae grow

When KQED showed Social media video of dead fish piled up on the shores of Lake MerrittJohnson said, “It’s a pretty powerful image. Yeah, it’s not good.”

Damon Tai, who describes himself as an educator and naturalist who studies mycology in his LinkedIn profile, tweeted a picture of a pile of dead fish in Lake Merritt on Sunday.

“Too many dead fish in Lake Merritt right now,” Tighe tweeted. “It could be related to the giant algae blooms that have been happening since earlier this month in the eastern bay in front of Alameda, where the wastewater flows.” Included a link to the nature app iNaturalist.

The algal bloom likely to lead to mass fish mortality is Heterosigma akashiwo, which has been tracked by SF Baykeeper and the San Francisco Estuary Institute and Center for Aquatic Sciences since its appearance last month. The Center for Aquatic Sciences noted that dead fish began to be reported around August 22, but also noted that the size of the bay made data collection a “huge challenge.”

Rosenfield said what has changed is that these reports are finally coming in and confirmation from field investigators this weekend.

The blue-green algal blooms, Rosenfield says, are most likely causing a die-off he says is caused by a combination of environmental conditions exacerbated by climate change and treated sewage discharged from wastewater treatment plants across the Bay Area. High. Heterosigma, a red-tide species of algae, may be killing fish in two ways. It can produce toxins that are deadly to fish, but it also lowers dissolved oxygen levels in water and can be deadly.

“So I don’t know which mechanism is at work here. It’s probably both,” Rosenfield said. However, the same blooms are also causing massive fish deaths in other parts of the world.

According to Rosenfield, the changes that spurred local flowering are likely tipping points in rising ocean temperatures. The solution, therefore, is for wastewater treatment plants to start recycling much more wastewater than they currently do.

An April 2022 report by an environmental group called the Pacific Institute explains that wastewater recycling is underutilized throughout California. The group estimates that California could reuse 1.8 to 2.1 million acre-feet of municipal wastewater per year.

San Francisco supervisor Aaron Peskin, an avid swimmer for the South End Rowing Club, witnessed red tide when he took a dip last Tuesday, Wednesday and Thursday.

“My wife said I couldn’t swim there anymore,” Peskin said. “I told her about it. It was like swimming in the rust.”

He’s starting to see problems on the coast too. His supporters have already started sending him pictures of dead fish on San Francisco beaches. Pesquin’s district includes Fisherman’s Wharf and the Embarcadero, all areas bordering the water. Peskin wants to see climate action in these regions and beyond.

“Our sewer provider, the Public Utilities Commission, urgently needs to come up with a strategy on how San Francisco can do its part to reduce the drainage that can exacerbate red tide. There is,” said Peskin.

Johnson of the Water Quality Control Board disagreed with claims that wastewater was to blame, and he says a jury has yet to come out.

He said the Water Stewardship Board spends $2.2 million each year to fund scientists studying algal blooms to see if they’re actually caused by human wastewater. increase.

“So if the solution is to ask the wastewater community to spend billions of dollars on nutrients, that’s what we’re going to do,” Johnson said. If the cause is something else and investing all that money doesn’t solve the problem, then we need to know that before we take action.”

According to Rosenfield, understanding what causes algal blooms is critical. Without precautions, this happens every year and can rise when the water warms and disappear when the water cools.

After four years as senior scientist at the SF Baykeeper and nearly 11 years as chief scientist at the Bay Institute, Rosenfield is already starting to get scared.

What really rocked him was when he saw a particular white sturgeon, a rare recreational fish, dead on Stinson Beach.

They are large armored fish, so they don’t die easily.

“Seeing sturgeon is an indicator of a much bigger problem,” he said.

It’s like a canary in a coal mine, but with scales.

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