Wednesday 26 November, 2014

Biological effects of oil spill linger on for decades

Published On: Tue, Apr 24th, 2007 | Environment | By BioNews

Washington, Apr 24 : Researchers at the Woods Hole Oceanographic Institution (WHOI) have found evidence that the biological effects of an oil spill linger on for decades after the spill.

The scientists found that buried, residual oil was affecting wildlife nearly four decades after a fuel oil spill polluted the beaches of Cape Cod, US.

Through a series of field observations and laboratory experiments with salt marsh fiddler crabs (Uca pugnax), doctoral student Jennifer Culbertson and colleagues found that burrowing behaviour, escape response, feeding rate, and population abundance are significantly altered after the crabs are exposed to leftover oil compounds from a 1969 spill.

They found that crabs that burrowed into the relatively pristine marsh of Great Sippewissett made holes that were straight and stretched an average of 14.8 centimetres (the longest was 18 cm).

Elsewhere, in Wild Harbor, the burrows averaged 6.8 cm (none were deeper than 14) and showed erratic shapes as the fiddler crabs halted or turned laterally. The locations of the stunted, twisted burrows mapped closely with the location of residual oil in the sediments.

Researchers also observed a very slow escape response among crabs caught from the polluted marshes.

As part of the experiment, Culbertson caught fiddler crabs from both marshes, and fed them sediments from either the oiled or clean marsh and used visual stimuli—a 5 by 5 cm weighted black square, swinging in front of the crab—to test how long they took to move away from it.

Findings revealed that crabs fed with oiled sediments were significantly slower to respond, which matched with what Culbertson had observed in the wild.

“It was shocking that you could bend over and poke the crabs, even flip them over, and they were slow to get up. It was as if they were drunk,” said Culbertson.

The study builds on previous work by researchers from the WHOI, which showed that oil compounds from the 1969 wreck of the barge Florida are still lingering in the sediments eight to 20 centimetres below the surface of Wild Harbor in Falmouth, Massachusetts.

“There are outward signs that the marsh in Wild Harbor has recovered. But there is still chemical warfare going on just a few centimetres beneath the surface,” said WHOI marine chemist Chris Reddy, whose lab group has been studying Cape Cod oil spills for nearly a decade.

Culbertson, a graduate student from the Boston University Marine Program (BUMP) and a guest student at WHOI, conducted the research in collaboration with Reddy, ecologist Ivan Valiela of the Marine Biological Laboratory, and several student colleagues from WHOI and BUMP.

The findings were published in the online version of Marine Pollution Bulletin on April 19, 2007 and it will appear later this spring in a printed edition. (ANI)

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