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Oil Contamination of Crab Larvae Could Be Widespread

2 July 2010 5:58 pm
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Tulane

Researchers have found droplets of oil inside crab larvae in the Gulf of Mexico. Although preliminary, the findings represent the first sign of hydrocarbons from the Deepwater Horizon well entering the food web. "So many things feed on larvae, that's the disturbing part," says Darryl Felder of the University of Louisiana-Lafayette. But Felder and others say it's too soon to predict what the larger effects on the ecosystem might be.

Two groups of scientists, funded by NSF rapid response grants, have been looking for changes in abundance of tiny crab larvae as they swim to estuaries along the U.S. Gulf Coast. One team, led by population ecologist Caroline Taylor of Tulane University in New Orleans, first found mysterious yellow-orange droplets in May while collecting blue crab larvae off Grand Isle, Louisiana. "We didn't expect to find anything [like this] inside them," Taylor says.

Subsequent surveys by Taylor's team have turned up droplets in larvae in several genera of crabs in sites including Pensacola, Florida, and Galveston, Texas. In some places, up to 100% of larvae contain these droplets. The composition of the droplets is currently being analyzed, and Taylor expects results next week.

Another team, headed by Harriet Perry of the University of Southern Mississippi in Hattiesburg, has already determined that droplets in blue crab and fiddler larvae contain hydrocarbons. "I've never seen anything like this," says Perry, who has studied the gulf for more than 4 decades. The lab hasn't determined whether the oil came from the BP spill.

The researchers don't know what impact, if any, the oil is having on the larvae. The tiny droplets sit between the shell and inner integument, Perry says, and the oil is probably forced under the shell as the larvae swim. "Some of them are pretty heavily loaded," she says. Perry's group is planning toxicological studies of oil and dispersant on larvae starting later this month. Two encouraging signs for the wild larvae: They are alive when collected, and they may lose the oil droplets when they molt, Perry says.

Meanwhile, however, many species are probably feeding on the oil-laden larvae, including red fish, speckled trout, and adult crabs. Fish can metabolize dispersant and oil, Perry says, but crabs may accumulate the hydrocarbons, which could harm their ability to reproduce.

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