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Giant, stinking algae bloom in San Francisco Bay due in part to excess human waste

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Photo by Justin Sullivan/Getty Images

In July, an algae bloom began to spread across the San Francisco Bay, killing tens of thousands of fish, turning the water a brownish color, and creating a fetid stench. According to the Alameda County Public Health Department, "Contact with the algae blooms can cause skin irritation and burning eyes to humans and can cause more dangerous effects to dogs."

San Francisco's algae bloom — considered the worst in over a decade — grew in August, such that the sickly-looking water's discoloration was reportedly visible to drivers on the Bayshore Freeway and Bay Bridge.

The SF Chronicle reported that by mid-August, concentrations of chlorophyll (an indicator of algae density) in the South Bay were the highest seen in over 40 years.

Eileen White, executive officer of the San Francisco Bay Regional Water Quality Control Board, said that while algae blooms in the summer can be expected, "What's surprising is the magnitude of it, how much it spread so quickly in the last several weeks and the fish kills."

Heterosigma akashiwo is the name of the algae responsible. Though the culprit has been identified, there is uncertainty about what is responsible for its recent spectacular growth.

Some scientists suggested that the phenomenon and its severity were resultant, not just of anomalous weather, but of so-called climate change. "Getting blooms like this is exactly what we expected to happen with climate change," Raphael Kudela, a professor and chair of ocean sciences at UC Santa Cruz, told the SF Chronicle.

The City of Oakland similarly emphasized on August 30 that "rising temperatures and changing precipitation patterns caused by climate change are a catalyst for their growth."

Eighteen years ago, U.S. Geological Survey scientists reported a similarly massive algae bloom in San Francisco Bay. Scientists then suggested a climate anomaly was responsible, and that normally, such blooms were usually made unlikely even during periods of hot weather by "inputs of turbulent kinetic energy from wind stress and tidal currents."

Amit Mutsuddy, deputy director of the San Jose/Santa Clara Regional Wastewater Facility, recently admitted that "The science is still premature in determining the exact cause of these algal blooms, but we're going to continue to do what we can on our part."

Although fluctuations in the weather (e.g., an absence of fog or wind; weak currents; improved water clarity; heat waves) may catalyze the algae's growth, the overabundance of nitrogen and phosphorous from wastewater and storm water dumped into the bay is believed to play a more central role. It certainly does not help that the region's 37 sewage plants are spewing nitrogen along with their wastewater — courtesy of the Bay Area's 8 million residents — into the bay at all hours.

Last week, White provided a reminder at a press conference: "When you flush the toilet every day, you're flushing nutrients down." Those nutrients end up in the bay and set the stage for the algae bloom.

David Senn, a scientist at SF Bay Nutrient Management Strategy, noted the impact of these nutrients: "They contributed to its size, the amount of the organism and how long it lasted."

To prevent or at the very least curb the reemergence of such blooms in subsequent years, the regional water board has indicated it will likely impose caps on nutrients in wastewater. Upgrading treatment facilities to achieve this end may cost upwards of $14 billion, which will inevitably lead to an increase in residents' water bills.

While some Bay Area localities are already doing their part to reduce outgoing nutrient loads, the wastewater facility servicing Silicon Valley blasts 85 million gallons of wastewater — containing 5.5 tons of nitrogen — into the bay every day.

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