A vendor at Fisherman’s Wharf holds up a live crab outside a food stand on March 9 in San Francisco. (Jessica Christian/S.F. Examiner)

Climate change could further delay crab season


When the state delayed our local Dungeness crab season last November, San Franciscans were upset. I heard people blame climate change for the toxic algae bloom that poisoned our crabs, but this explanation may be too simple. What really caused the unusual bloom of Pseudo-nitzschia phytoplankton and will our Thanksgiving plates be without crab again?

A team of scientists hopes to answer these and other questions as they travel from Mexico to Canada aboard a National Oceanic and Atmospheric Administration research vessel. Their ship docked at Pier 15 last Saturday, and some of the world’s preeminent scholars on ocean acidification disembarked to talk about their research.

Ocean acidification is a change in the water’s chemistry caused by elevated levels of carbon dioxide. The ocean absorbs about a quarter of the carbon dioxide we release from our cars, power plants and agricultural operations every year. While this process lowers emissions in our atmosphere, the massive amount of carbon dioxide we’re emitting also lowers the ocean’s pH making it more acidic.

Dr. Richard Feely, a senior scientist with NOAA’s Pacific Marine Environmental Laboratory, was one of the first scientists to study ocean acidification. He told me when he began his work he actually bet with other scientists they wouldn’t find a problem. The scientists found a problem everywhere they looked.

“That was an ‘Aha!’ moment for me,” Dr. Feely said. “I realized how sensitive this region is.” He added the San Francisco Bay is “a particularly sensitive region.”

Dr. Feely is leading the current NOAA research expedition. He hopes by working collaboratively with other scientists they can expand their understanding of ocean acidification and how it affects marine life.

While ocean acidification has been linked to deaths in oyster hatcheries in Washington, not much is known about how the Pacific ecosystems will respond to lower pH levels. Some species may actually thrive in warmer, more acidic waters. Pseudo-nitzschia, the phytoplankton behind the delay in our local Dungeness crab season, may be one such species.

This spring the phytoplankton began its regular, seasonal bloom in the Pacific, and Dr. William Cochlan of San Francisco State University’s Romberg Tiburon Center is hard at work studying the species. Although Dr. Cochlan isn’t traveling aboard the NOAA vessel, he is collaborating with Dr. Feely and other scientists to understand how ocean acidification affects the phytoplankton.

He told me warmer oceans associated with El Niño patterns does increase the phytoplankton’s growth. But this doesn’t necessarily mean it will produce high levels of domoic acid, the neurotoxin responsible for poisoning our crabs. The Pacific Ocean has endured El Niño seasons in the past with no impact to our plates.

In lab experiments, however, Dr. Cochlan has found a “big jump” in the phytoplankton’s toxicity as pH levels decline. This means current pH levels off the coast of San Francisco could promote the growth of very toxic Pseudo-nitzschia. Scientists aboard the NOAA vessel are determining if Dr. Cochlan’s lab experiments are echoed in the real world.

“It’s really complex,” he said. “Scientists want to solve this and we’re very close. But we’re not there yet.”

Larry Collins, president of the San Francisco Crab Boat Owners Association, recognizes the ocean’s complexity and the risk associated with declaring anything the new normal. He has seen some bizarre things during his decades as a commercial fisherman. But if scientists find a definitive link between the warmer, more acidic oceans caused by climate change and large, toxic algae blooms, Collins and his colleagues could be in for some trouble.

“I think that absolutely we need to do anything we can do to cut carbon,” he told me. “Because no matter how big the ocean is, it’s not an infinite sump pump we can count on.”

San Franciscans who care about our local Dungeness crabs should keep a close eye on NOAA’s findings. It could be one more reason to care about climate change.

Robyn Purchia is an environmental attorney, environmental blogger and environmental activist who hikes, gardens and tree hugs in her spare time.algae bloomclimate changeDungeness crabenvironmentgreen spaceRobyn PurchiaSan Francisco

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