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Making Waves at 35: Stopping Harmful Algae Blooms

Dead sturgeon on the shoreline

In celebration of our 35th year of defending San Francisco Bay, each month we’re sharing significant victories that we’ve won together. And we’re highlighting how these wins are still making waves today! 

Stopping Harmful Algae Blooms at the Source

The summer of 2022 broke our hearts. In late July, we started receiving hotline tips from people who live on houseboats in the Oakland-Alameda Estuary—they were seeing brownish-red water and reporting a funny smell. It turned out to be the beginning of the worst algae bloom the Bay had seen in decades.

Our field science team investigated using our boat and drones, a private plane, and even satellite imagery—documenting the spread of the outbreak, taking water quality samples, and holding our breath to see how bad it would get.

The bloom spread from the East Bay to San Francisco and from the lower South Bay to north of Richmond.  And then the nightmare began. About a month after it started, rafts of dead minnows, bat rays, bass, and other fish started washing up around the shoreline. Our investigators were some of the first to document the massive Bay-wide fish die-off, witnessing dead sturgeon, including the endangered green sturgeon, washing up onto beaches around the Bay

In all, the bloom killed unimaginable numbers of fish—it’s not even possible to estimate how many died because so many dead fish went unseen or washed out on the tides. Sadly, the same algae returned in 2023. Then our scientists found it again this summer in pockets around the Bay.

These repeat occurrences are worrisome. It means we have to tackle the source—now.

The primary cause of the blooms is too much nitrogen and phosphorus in the water. Those pollutants come from treated sewage discharges into the Bay from the 37 wastewater treatment plants around its shore.

Luckily, Baykeeper is experienced with reducing pollution at the source.

Immediately following the 2022 devastating outbreak, we increased our pressure on the SF Regional Water Board—the agency in charge of regulating sewage treatment plants—to lower the amount of nitrogen and phosphorous that treatment plants are allowed to discharge. Over the last two years, we met with countless officials, presented at agency hearings, organized public petitions, and raised awareness in the media at every opportunity.

And we won! This past July, the Water Board voted unanimously to enact a new law that would require a 40% reduction in nitrogen levels over the next 10 years. It’s a great first step—although Baykeeper’s experts suspect it won’t be enough.

Baykeeper will keep watch and continue advocating for the health of the Bay and everyone who lives around it. Some of our other big efforts to reduce sewage pollution over the years include:

  • Reducing sewage spills around the Bay: Baykeeper has successfully undertaken a three-decade legal campaign to reduce sewage spills from cities around the Bay. These efforts have helped reduce raw sewage pollution from more than 20 cities – in some cases by 90%.  We compelled the cities of San Bruno, Burlingame, San Jose, and Richmond to upgrade their sewage treatment systems and replace failing pipes. We also secured a multi-year agreement for East Bay Municipal Utilities District to upgrade its sewage infrastructure.
  • Stopping the Bay’s biggest sewage polluter: Last year, we discovered San Francisco dumps on average 1.2 billion gallons of polluted stormwater runoff and raw sewage into the Bay annually, which makes them the single largest source of the nitrogen and phosphorous that cause algae outbreaks. So earlier this year, Baykeeper filed a groundbreaking lawsuit to hold the city accountable under the Clean Water Act—and then US EPA and California’s Attorney General joined our action.
  • Monitoring for HABs: This year, Baykeeper launched a brand-new program to train community volunteers to detect the spread of harmful algae in the Bay proactively. The five-year program—in partnership with the National Oceanic and Atmospheric Administration, US Geological Survey, and SF Estuary Institute—will monitor algae concentrations in hotspots around the Bay. The results will help scientists better understand what level of nitrogen and phosphorous reductions are needed as part of our long-term strategy to stop fish-killing algae blooms.

Baykeeper’s work has made waves across the Bay—and your support over the years has made it all possible. You can learn about our victories stopping algae-causing sewage pollution and supporting the health of the Bay by scrolling through Baykeeper’s timeline of historic wins, below.

Image of a dead sturgeon in San Mateo in the wake of a harmful algae bloom in 2022.