Photo via Shutterstock
A surge of giant crabs might sound like something from a 1950s B-movie, but that is exactly what is happening in the Chesapeake Bay. According to a new study done by researchers at the University of North Carolina’s Aquarium Research Center, carbon pollution is causing the animals to drastically increase in size. Crustaceans have been bulking up on the carbon from factories, power plants, and vehicles to grow larger and faster, making them even more voracious predators to vital filter-feeders such as oysters. The oysters, who play an important role in cleaning the Bay, conversely mature much slower in the presence of carbon, making them even more vulnerable to the claws and huge appetites of crabs.
Researchers predict that over the next century, ocean acidification from carbon pollution could make for bigger crabs who would in turn consume more organisms and throw the food chain out of balance. Lobsters and shrimp are also plumping up with the extra carbon, further complicating the problem. In an experiment Ries and his colleagues published in Geology back in 2009, they found that crabs, lobsters, and shrimp bulked up as much as four times more than when in tanks containing low levels of carbon. Meanwhile, under the same high carbon conditions, scallops, oysters, and other organisms grew at only one-quarter of the speed that they did in low-carbon waters.
Bay oysters, which are endangered in the Chesapeake, are currently having trouble developing from spat to adult. Combined with disease, and overfishing, predation is just one more challenge facing the restoration of their numbers. However, oysters may not be completely out of luck. Strangely, in an experiment conducted by Luke Dodd, Michael F. Piehler of UNC and Jonathan Grabowski of Northeastern University, the team noticed that when they placed mud crabs in a high-carbon tank, the animals became confused and ate half of the amount of oysters they would under normal circumstances. The researchers hypothesize that the carbon could be depriving crabs of oxygen and confusing their systems. Even so, they note that there is a possibility that the arthropods could eventually evolve to deal with the carbon and go right back on feeding.
States are doing their best to restore the oyster population and keep their waters clean. Virginia has created sanctuaries in places such as the Rappahannock River to protect them and allow harvesting on a rotating basis every two years. They also have been encouraging private aquaculture by selling plots of riverbed to farmers at $1.50 an acre. Maryland has contributed tens of millions of dollars into restoring oyster habitat, are working to develop aquaculture, and protect the animals with massive fines and prison sentences for poaching. Both states have already seen modest recoveries in both oyster and blue crab populations.