Thousands of dead fish are washing ashore in the San Francisco Bay Area as a harmful algal bloom—called a red tide—turns local waters a murky reddish-brown.
While the area normally sees algal blooms during the summer, the size of this one and the carnage that has come with it are unusual, Eileen White, executive officer of San Francisco Bay Regional Water Quality Control Board, tells Terry Chea and Olga R. Rodriguez from the Associated Press (AP).
"From a fish's point of view, this is a wildfire in the water," Jon Rosenfield, a senior scientist with the environmental group San Francisco Baykeeper tells KQED’s Joe Fitzgerald Rodriguez and Lesley McClurg.
Harmful algal blooms are overgrowths of algae in the water that can harm people, animals or the local ecology. This one was caused by a type of algae called Heterosigma akashiwo, which is always present in the bay, per the AP. Experts believe the bloom has led to the mass fish death by producing toxins or depleting the water’s oxygen levels—or both.
Rotting fish carcasses have already piled up in waters across the region, including Oakland's Lake Merritt, the oldest government-owned wildlife refuge in the United States. Certain environmental conditions, such as warmer water and excess nutrients from fertilizers or sewage, can trigger these blooms. And a heat wave forecast for the holiday weekend could exacerbate the algae’s growth even further, per the AP. Extreme heat in future years might also aid conditions for algae growth.
“It’s exactly what we would expect with climate change,” Raphael Kudela, a phytoplankton ecologist at the University of California, Santa Cruz, tells the New York Times’s Livia Albeck-Ripka. “We’re going to see more blooms like this.”
Kudela tells the newspaper that while this particular algal bloom could not be directly linked to climate change, the warming trend is making these events more likely.
A red tide bloom, likely caused by a mixture of warm water temperatures and nutrient runoff, has killed fish, rays, and even sharks in San Francisco Bay, San Pablo Bay, and South Bay in California— NowThis (@nowthisnews) September 1, 2022
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“It doesn’t smell very good right now, so it’s a bit of a nuisance," Graham Webster, who takes jogs around the lake at least once a week, tells the AP. “But the bigger question is what’s happening to the lake and the bay? And what’s causing it? Is it our fault? Can it be fixed?"
High amounts of nutrients, such as nitrogen and phosphorus, also affect algal blooms. Right now, the city's wastewater treatment facilities that operate around the bay aren’t designed to filter nutrients out of the water. Environmentalists say the plants need updates to prevent blooms like this one from happening in the future, the Times reports—but treating the water would cost billions of dollars, per the AP.
Rosenfield tells KQED the number of dead fish is “uncountable,” though his field investigator confirmed the bloom has killed “tens of thousands” in Lake Merritt alone.
“It smells horrible,” Simine Yahaghi, who lives near the lake and walks around it daily, tells the San Francisco Chronicle’s Jessica Flores. “More than that, it’s sad that you see thousands of fish dead. It’s like a massacre.”