Rising ocean acidity bad news for West Coast’s $200 million Dungeness crab fishery
Acidification of the world’s oceans was supposed to be a distant problem — nothing to worry about until some time in the future.
But a new study of juvenile Dungeness crab collected off the Pacific Northwest coast shows the crustaceans are vulnerable to conditions that exist right now.
Published last week in the journal “Science of The Total Environment,” the study found that tiny developing crabs sampled from coastal waters off Oregon and Washington suffered damage to their shells as well as to bristly, hairlike sensory organs believed to help them orient to their surroundings.
The findings have unsettling implications for a roughly $200 million West Coast fishery — California’s most valuable ocean crop and a key economic driver for struggling fishing ports on the North and Central Coast.
The California fleet caught more than $47 million worth of Dungeness crab last year, including nearly $5 million worth of crustaceans landed in Bodega Bay.
The new research, said veteran Bodega Bay fishermen Tony Anello, sounds “very discouraging.”
“The way I look at things right now, if I had to start in this business right now, I wouldn’t start at all,” he said grimly.
The findings are consistent with laboratory studies demonstrating ill effects on developing crabs and other shellfish from increasingly acidic conditions predicted to occur as oceans absorb ever-higher concentrations of carbon dioxide from the atmosphere.
They mark the first conclusive evidence that existing conditions in the natural environment are severe enough already in some areas to interfere with development of larval crabs, causing abnormal ridging and scarring of their external shells and legs from the corrosive effects of the water, the authors said.
“We found dissolution impacts to the crab larvae that were not expected to occur until much later in this century,” co-author Richard Feely, a senior scientist with the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory, said in a news release.
It’s also the first time scientists have seen evidence of secondary effects on the organisms’ bristly “mechanoreceptors,” which jut out from their shells and help the creatures navigate through space.
Ocean acidification — a side effect of global greenhouse gas emissions — is intensifying more rapidly on the west coast of the United States than anywhere else in the world, and particularly off California, said lead author Nina Bednarsek, a senior scientist with the Southern California Coastal Water Research Project. The worsening conditions are a function of temperature, currents and ocean dynamics, she said.
The resulting chemical changes reduce the availability of calcium carbonate, a key building block used by crab, mollusks and other organisms to build strong, hard shells and other organic structures.
It also corrodes calcified shell material and, in the case of the nearly translucent, juvenile Dungeness crabs, appears to destabilize the anchors that attach their sensory receptors in some cases, causing them to fall out, researchers said.
Those crabs showings signs of shell dissolution also were smaller overall than their counterparts, according to the study.
The concern is that affected crab will have developmental delays, difficulty swimming and regulating buoyancy and spatial position, as well as increased energy demands and generally impaired survival.