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Mollusks and oil don’t mix part 2

By Staff | Jul 2, 2010

Crude oil is a complex mixture of hydrocarbons (molecules containing any number of arrangements of atoms of hydrogen and carbon). Some of these hydrocarbons, called polycyclic aromatic hydrocarbons (PAH) are known to be carcinogens. Crude oil also contains non-hydrocarbon compounds such as sulphur and vanadium (a heavy metal). All components of crude oil are degradable by bacteria, although at varying rates. A variety of yeasts and fungi can also metabolize the hydrocarbons in oil. In my previous article about mollusks and oil, I mentioned the distinction between the immediate mayhem caused by oil spills versus the long-term effects of hydrocarbons and heavy metals present in oil as they are incorporated by mollusks and work their way through marine food webs.

Dr. Peter Roopnarine, Curator of Geology at the California Academy of Sciences in San Francisco and a past Visiting Curator at The Bailey-Matthews Shell Museum, has joined with Laurie Anderson from Louisiana State University and David Goodwin from Denison College to study the problem. Their approach is to study the accumulation of hydrocarbons and heavy metals on shells–mollusks are always adding to their shells, and will incorporate small amounts of these compounds when they are present in the surrounding water. Dr. Roopnarine is applying the same principles and technology to the problem as he used in a similar study developed in the San Francisco Bay area during the past three years. In that study, Roopnarine and his associates found that mollusks from polluted areas incorporated vanadium and nickel, two metals that are also found in oil.

Their study will include three mollusks that differ in their feeding habits, an oyster, a filter-feeder that gobbles up plankton, a tellin, which is a clam that filter-feeds detritus from the sea floor, and a periwinkle, a marine snail that grazes on algae. By monitoring the speed at which the different hydrocarbons and heavy metals appear in the shells (through repeated collecting in affected areas), they will be able to determine whether the nasty compounds are being removed directly from seawater of ingested via food sources. So far, Dr. Roopnarine and his team have collected pre-oil spill material from the coasts of Louisiana and Alabama. These initial samples will provide the background information, or “control” data, against which the contaminated samples will be compared. Last week Dr. Roopnarine requested that the Shell Museum send samples from Sanibel and adjacent areas for comparative studies in case the oil eventually make it down our way, a chore that I sincerely hope won’t be necessary, as a direct, local hit is not anticipated at this point.