Even with the neurotoxin-shortened season, 2016 has been a good year to be a commercial crab fisherman. “It's better than it's ever been,” says Fisherman's Wharf-based crabber John Mellor, who has been gathering Dungeness crab from the waters outside the Golden Gate for 37 of his 53 years.
Mellor believes efforts to clean up the once-brackish bay — where larval crabs begin their life cycles — have helped local Dungeness become some of the healthiest on the West Coast.
And for the record: Even the neurotoxin-laden crabs, poisoned with domoic acid after feasting on an algal bloom that warm weather and still winds failed to dissipate last year, were healthy. (The same can't be said about the seals or seabirds that ate them.)
But while scientists are still squabbling over whether it was climate change caused by carbon emissions that kept the ocean waters still and warm long enough to grow the bloom — at the same time rain and snowstorms were steered away by a ridge of high pressure, fueling the drought — CO2 may pose a mortal threat to Dungeness after all. In a study published in the journal Marine Biology, scientists found that ocean acidification — which is a byproduct of carbon emissions — can kill off crab larvae, by preventing the formation of the hard shells needed to survive.
And ocean acidification is already well underway. Just ask local oyster farmers, who, more than a decade ago, saw as much as half the population of young oysters die off mysteriously. The culprit turned out to be the pH levels in the sea. Oyster farmers have started growing more seed — oyster larvae — to compensate, but scientists warn that “upwelling,” currently seasonal wind patterns that allow more acidic ocean water to rise up to coastal areas where oysters and crabs live and reproduce, could become year-round by 2050.
There are a few factors working in the favor of crabs (and the humans who love to eat them). The at-risk crabs in the recent study were in the Puget Sound, a heavily populated area where ocean water is already naturally acidic. And the Pacific Ocean, which is vast, can absorb a lot of carbon — but that's also part of the problem.
The Pacific Rim is full of developing countries that are burning coal to power new cities and industries. And, according to a 2012 study from the Center for Ocean Solutions, even the cleaned-up bay is acidifying.
“The ocean can only support so much carbon,” says Mellor, who recently traveled to Washington, D.C. to help convince lawmakers to study the issue before it becomes a real problem that sneaks up on crab fishers and consumers in the same way the domoic acid situation did — with two weeks' notice. “You really don't see what's going on in the [deeper] levels … you don't want to be in a situation where, two to three years later, there suddenly aren't any crabs.” Which is exactly what happened with the oysters.