Nearly 40 years after the oil spill, residual oil under the sediment is still damaging the health of a salt marsh, impacting crabs and sea grass beds.

In 1969 a barge ran aground in Buzzard’s Bay off Cape Cod, spilling 200,000 gallons of oil. Today, nearly four decades later, that oil spill is still affecting a salt marsh and its wildlife. The general public became aware of the damage oil spills can cause when the Exxon Valdez tanker accident spilled an estimated 11 million gallons of oil in 1989. A great deal has been learned since then about long term damage from oil spills. Chronic oiling has been shown to affect seabirds along every coast of the world. But the work done at Wild Harbor, Falmouth, Massachusetts gives a much more dramatic picture of just how long term the impacts on entire ecosystems are and why prevention is key to protecting those fragile environments.

After the Exxon Valdez oil spill, efforts were made to try several different, and often controversial, cleaning methods including hot water washing some beaches. Ongoing studies which were funded until 2005 measured the recovery of each type of beach treatment. And in 2005 they found oil just below the surface, especially in areas that are sheltered. This is mirrored by the finding at Wild Harbor, a salt marsh also protected from the most intense wave action.

The effects on this marsh are dramatic. When plaster casts were made of fiddler crab burrows, it showed that the ones in Wild Harbor dug short, twisted burrows as compared to the long straight down burrows of the crabs in nearby Great Sippewissett marsh, which has no residual oil. The burrowing of fiddler crabs aerates the sediment which in turn enhances sea grass beds. Sea grass beds provide the stability that prevents erosion of the marshes in addition toserving as critical habitat for a multitude of birds, fish and invertebrates

Crabs exposed to oil have been affected in their feeding patterns, escape response and overall population growth in addition to the abnormal burrowing most obvious in this study. And these affects are still evident after nearly 40 years, reinforcing the concerns raised by findings on chronic oiling in birds. Oil spill cleanup is difficult at best and any cleaning effort can affect entire ecosystems for at least 15 years, as evidenced by the Exxon Valdez follow-up studies. These studies point up the immense level of damage done long term by oil spills. And unfortunately oil spills will continue to occur, which means that preventing oil from coming ashore is going to be most important for protecting sensitive habitat from long term damage.