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Red Tide Washes Dead Fish Onto Bay Area Shores

The Bay Area is in the grip of an algal bloom, resulting in thousands of dead fish washing onto shorelines throughout the Bay. San Francisco Baykeeper, a group that focuses on Bay Area water conditions, has been monitoring the water and communicating with relevant agencies and researchers since receiving reports of brown water from Lake Merritt, the Oakland Estuary, San Leandro Bay, and surrounding areas of San Francisco Bay in late July. The bloom has now been identified as being caused by the species Heterosigma akashiwo, a microscopic swimming alga known to form what is also called a red tide. According to Baykeeper, the species is always present in the Bay at background levels, but the region has not seen a bloom of this magnitude since 2004.

The previous bloom in the Bay was recorded on September 8, 2004, and was said to have occurred due to “a coincidence of unusually weak neap tides, calm winds, and four consecutive days of record high air temperature.” The surface water temperature that day was also the “highest ever measured” at 72.68°F.

The current bloom became visible several weeks ago. On July 29, KTVU reported that residents on the Oakland Estuary had seen “unusually murky and muddy” water for days, and in Embarcadero Cove Marina the rust-colored water was visible for days “despite the tides coming in and going out.” A week later, Oakland Estuary resident Michael West described what he saw: “It’s so thick, it looks just like when you’re stirring up your hot chocolate or something.”

red tide on mission creek
The algal bloom is clearly visible in Mission Creek, San Francisco.
© 2022 San Francisco Baykeeper

Baykeeper Executive Director Sejal Choksi-Chugh told us the organization is concerned about the numbers of fish that are dying. “The sturgeon especially have been turning up dead in great numbers, and we’re concerned about the threat to the Bay’s historic population.” And although H. akashiwo is not generally considered an acute risk to people, Choksi-Chugh issued the following statement on the organization’s website: “Baykeeper cautions against people or pets contacting the brown murky water, or eating seafood caught in the area, until the algal bloom dissipates.” An unfortunate situation for the long weekend ahead.

dead sturgeon on local beaches
These sturgeon were found washed up last week at Coyote Point, San Mateo (left) and Keller Beach, Richmond.
© 2022 San Francisco Baykeeper

Dr. Jon Rosenfield, a senior scientist with Baykeeper, told the NY Times that the fish are “most likely being asphyxiated as a result of the algae” and added it’s likely that many more fish have died at the bottom of the Bay. The alga is expected to die off eventually as the days get shorter, temperatures cool off, and the bloom exhausts its supply of nutrients. In the meantime, the weekend’s forecast hot weather may help keep the bloom alive a little longer.

Choksi-Chugh said the Bay’s ecosystem has certainly suffered, but there is hope it will bounce back and the food chain will replenish itself. And while there is nothing anyone can do right now to fix the current problem, addressing the issues of pollution, including “reducing nitrogen and phosphorus that are entering the water from wastewater plants,” could go a long way toward preventing blooms in the future.

“Treated sewage discharges from the Bay’s 40 sewage treatment plants and the pollutants from five dirty oil refineries create conditions ideal for algal blooms,” Choksi-Chugh wrote. “Once a waterway is choked with algal blooms, the water becomes a dead zone for fish and wildlife.”

Large fish or small, predator or prey, the red tide doesn’t discriminate. This shark has suffered the same fate as thousands of fish across the Bay Area.
© 2022 San Francisco Baykeeper

“Baykeeper scientists have been actively working for the past five years through agency technical advisory committees to prevent large blooms of any number of potentially toxic microorganisms from becoming commonplace in the Bay. The Regional Water Board needs to get excessive sewage and refinery discharges under control, and Bay Area cities need to invest in water recycling to keep wastewater out of the Bay in the first place. These changes must happen fast in order to keep algal blooms like the ones cropping up right now in the Bay from taking over more regularly. Hopefully this is a wake-up call for the agency to take faster action, because consistent algal blooms in the Bay would be detrimental to wildlife and people recreating in and around the Bay.”

Baykeeper is asking anyone who notices a large quantity of dead fish near shoreline areas where blooms have occurred to contact them via their pollution hotline or San Francisco Estuary Institute’s observation form.

We can only suggest that you shelve any plans to swim in the Bay this weekend, and instead, go sailing.


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Finding a Seat on the Ocean
The 'Latitude 38' Crew List parties have come back to life as sailors showed up to compare notes, read the stickers pasted on one another's chests, and sort out who's sailing where and with whom. We'll assume it will all get sorted out in the weeks to come.