They went over to the oysters, but they didn't eat as many — sometimes fewer than half of what other crabs ate under normal conditions. Dodd scratched his head. "Acidification may be confusing the crab," he said. The situation, he concluded, "is more complicated than you'd be led to believe."
Ries said crabs might be getting loopy from all that carbon in their systems, depriving them of oxygen and putting them in a fog.
Both researchers said that acidification happens so slowly that crabs may eventually grow more accustomed to it. "You can't discount evolution taking over," Dodd said.
The Chesapeake Bay oyster certainly doesn't need any more bad news. Two diseases, Dermo and MSX, origin unknown, have killed them by the bushel for decades. That and overfishing have dramatically reduced their numbers, officials said.
Recently, the critter showed signs of a modest recovery in Virginia and Maryland. Virginia, which harvested only 79,600 bushels of oysters in 2005, racked up about 236,200 bushels in 2011, the most since 1989. Maryland had 26,400 bushels in 2005 but hauled in 121,200 bushels in 2011.
Oysters are filter feeders that play a critical role in cleaning the polluted bay. "One hundred years ago, the bay was crystal-clear because they filtered it every three weeks, as opposed to every three years today," Ries said.
That is one of several reasons why the two states recently launched all-out offensives to protect bay oysters.
Virginia created huge sanctuaries in public waters such as the Rappahannock River where watermen are allowed to harvest oysters on a rotating basis about every two years. The state also strongly encourages private aquaculture, selling plots of riverbed or bay floor to oyster farmers for $1.50 an acre.
Maryland has poured $50 million into its oyster recovery effort over the past 16 years. The state now forbids oyster harvesting on a quarter of the bars where they grow, protecting them with a fine of up to $25,000 and 15 years in prison. Maryland is only beginning to develop aquaculture.