Oysters face double threat


Olympia oysters, a California coast native decimated by overfishing in the late 1800’s, grow more slowly in acidified oceans—one of the consequences of global warming. But new research involving native oysters extracted from Tomales Bay, undertaken by the University of California, Davis Bodega Marine Laboratory, shows that the bivalve, which is being used in aquaculture restoration projects, faces an equal threat by invasive predator snails. Previous research has documented how oysters suffer from ocean acidification, in which water absorbs the increasing levels of carbon dioxide in the air, altering ocean acidity and taxing sea life. The Bodega Marine Laboratory study, titled “Ocean acidification increases the vulnerability of native oysters to predation by invasive snails,” published Jan. 15, found that acidification stunts the growth of native oysters, resulting in shellfish 29 to 40 percent smaller than normal; this lackluster growth encourages predation by the Atlantic oyster drill, which eats 20 percent more oysters in acidified conditions. (The snails secrete acid on the shell and then drill through to the meat). Eric Sanford, the lead researcher of the study, explained that it’s like going out for tacos: if the tacos are smaller, you will simply eat more of them. He added that his team was not surprised at the results per se, but rather at their scale. “It was a significant effect,” he said. Ocean acidification did not appear to affect the snail; invasive species, scientists believe, may be better equipped to withstand environmental stressors.