Early Wednesday morning, Robert Fairbank steered a boat out of San Francisco’s South Beach Harbor under coral-colored skies.
As the vessel entered the open water, Fairbank, a skipper for the environmental nonprofit Baykeeper, pointed its bow eastward where the bay’s blue waters have turned tea-brown.
The culprit, scientists and public health experts suspect, is a harmful algal bloom caused by a microscopic marine organism, Heterosigma akashiwo, which is known to turn tides red.
If concentrated enough, Heterosigma akashiwo can produce toxins that kill fish and, potentially, even seabirds. Past blooms in places like Japan, China, Korea, Canada and the United States have resulted in millions of dollars lost to dead and decaying fisheries.
In general, blooms occur when algae — simple photosynthetic organisms that live in the sea and freshwater — grow out of control. Though the California Department of Health has so far deemed this bloom a “nuisance” and not a direct threat to public health, there is still much uncertainty about the brown bloom’s toxicity, origin and extent.
These unknowns are why Fairbank, senior scientist Jon Rosenfield and field investigator Julia Dowell piled onto Baykeeper’s boat just after dawn, armed with empty water bottles and rubber gloves to scoop up water samples across the San Francisco Bay.
The ruddy waters were first reported by residents of houseboats along the Alameda channel in late July and have also been observed in Lake Merritt and other parts of the East Bay.
As the boat bobbed near the mouth of the San Leandro Bay, Dowell collected samples where scales of flat white bubbles could be seen floating on the water’s surface. In the distance, a woman and a dog waded in the waves on a nearby beach.
Rosenfield explained that microorganisms like these are always present in the bay, but with the right combination of sunlight, nutrients and tidal and wind conditions, vast blooms can form — sometimes overnight.
“People see the blue bay, and they’re like, ‘Oh, it’s so clean,’” said Rosenfield. But “looks can be deceiving. The bay is highly enriched for nitrogen and phosphorus.”
San Francisco Bay is one of the most nutrient-polluted water bodies in the nation. This is partly because treated sewage and stormwater from millions of people is discharged directly into the water. That discharge is nutrient-dense.
The overabundance of these elements in water bodies is considered one of the nation’s most pressing environmental challenges and can cause microorganisms like Heterosigma to grow faster than ecosystems can handle, which chokes them of oxygen and threatens marine life and water quality.
Though it’s something of a scientific mystery why harmful algal blooms — or HABs — don’t occur here more often given the nutrient overload, scientists like David Senn of San Francisco Estuary Institute posit that several factors, including wind patterns and tidal exchanges with the Pacific Ocean, keep these bloom-forming abilities at bay.
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But when blooms do happen, scientists are left to piece together the conditions that caused them.
Why now?
“I think the ‘why now’ question is not an easy one at all to answer,” said Senn. “What exactly is the trigger for any one event is something that is difficult to nail down, and especially at this early stage.”
Still, Rosenfield called this week’s bloom a “ticking time bomb” of what’s to come if cities don’t address the sheer volume of pollutants we flush down the drain. “This algal bloom points to the urgency that the regional water board and all of us need to have about the treated wastewater that we’re putting into the bay,” he said.
Climate change could also make blooms like this one worse. While it’s difficult to link any one event to a warming world — especially in an ever-changing tidal estuary like the San Francisco Bay — scientists predict that warming temperatures will increase the size, severity and frequency of harmful algal blooms throughout the world.
“There is a lot of complexity to climate change,” said Keith Bouma-Gregson, a biologist with the U.S. Geological Survey. “We’re adding layer upon layer of factors. It’s not just like, oh, the air got hot; therefore, the water’s hot. It’s: What’s the global wind pattern doing? How is that affecting upwelling? What’s the water temperature that’s coming into the bay? What does the coastal fog pattern look like?”
And though harmful algal blooms here are unusual, Senn noted, it’s important to understand how a warming world would shift “the cocktail of contaminants” in the bay.
“One of the major concerns is if the dynamics of the system shift, there is the potential for large events in the future,” he said. “What’s unknown is the degree to which they would shift, but the ingredients are there.”
Rosenfield was more pointed in his assessment, noting that these tiny critters respond directly to the changes in their surroundings.
“There’s no way it’s not going to get worse as temperatures increase,” he said. “Most of these organisms, if not all, respond directly to temperature. They’re not warm-blooded like us. ... As things warm up, they are going to be reproducing faster, and the season that they can reproduce in will be longer. So you’ll get a greater window of opportunity for them to bloom — just like wildfires.”
Ultimately, he sees this week’s red tide as a wake-up call for Bay Area water managers to rethink their policies and regulations.
“Our bay is resilient, and the water quality is much better than it used to be. So we’ve been given the benefit of more time than other places in the world. But we need to use that time to actually address the problem before things get really bad,” he said. “This needs to be a high priority before we wake up to a bay that’s green pea soup.”
