Philadelphia shells help measure pollution from BP oil spill

As biologists rush to understand the toxic impact of the Deepwater Horizon spill, they are pulling dozens of old oyster shells from the well-stocked drawers of Philadelphia's Academy of Natural Sciences.

The oysters, dating back to 1887, hold a record of pollution in the Gulf of Mexico, and could tell scientists how the spilled oil and chemicals used to disperse it are working their way through the food chain.

The academy houses one of the largest and oldest shell collections in the world.

"You never know what these things will be useful for," said Peter Roopnarine, the leader of the ongoing study, whose first results are expected by September. "Each individual shell is going to give us a record back in time."

While the bodies of sea turtles, porpoises, and other marine animals have been turning up around the region of the spill, the exact causes of death remain a mystery.

The animals may have been poisoned by oil that has come up through the food chain, or by the detergents used to disperse it, or they may have died from some cause other than the BP spill.

The shells promise to offer clues.

Roopnarine, curator of geology and invertebrate zoology at the California Academy of Sciences in San Francisco, said the oldest shells there were destroyed in the fire after the 1906 earthquake.

So he turned to the academy in Philadelphia. Above the dinosaur skeletons and dioramas is an entire floor devoted to shells - cases and cases, each filled with candy-striped snails from exotic lands and homely oysters from closer to home.

There are 10 million specimens, weighing a total of 55 tons and dating back to 1812, said Paul Callomon, manager of the mollusk collection.

"We never throw anything away," Callomon said.

When Roopnarine called several weeks ago, Callomon said, he was able to search a database of the collection to locate 107 oyster shells gathered from various regions of the gulf between 1887 and 1960.

Callomon said that when oysters or other mollusks take in hydrocarbons, PCB, heavy metals, or other pollutants through water or food, these get incorporated into the shells.

The study will also help scientists figure out the impact of the detergents used to disperse the oil. They were sprayed underwater, leaving an enormous plume of dissolved oil hanging in the water and being taken up by anything with gills.

It's an unprecedented situation, Callomon said, and the impact on the ecosystem is unknown.