Oiled Blue Crabs Hint at Tainted Food Chain in Gulf of Mexico

Oil droplets found in blue crab larvae

Where did all the oil go? Some fear it is making its way into the food chain

Even as the “static kill” on BP’s Macondo well stops the flow of oil and many talk of corners turned and “disappearing” oil, researchers remained concerned with the longterm ecological damage caused by the millions of gallons of oil and dispersant released into the Gulf.

For several weeks biologists have been closely monitoring blue crab in the Gulf in response to the BP spill. Blue crab is considered a “keystone species,” playing a fundamental role in the food web as both predator and prey. The crab are a “living repository of information on the health of the environment,” according to oceanographer Richard Condrey.

Oil droplets have been found in blue crab larvae, a “troubling” sign for the overall health of the food chain that may have consequences in the Gulf for years to come.

“It would suggest the oil has reached a position where it can start moving up the food chain instead of just hanging in the water,” said Loyola University biologist Bob Thomas. “Something likely will eat those oiled larvae … and then that animal will be eaten by something bigger and so on.

The amount of oil ingested by the tiny creatures is small enough that they can survive says Thomas, but as the oil moves up the food chain, creatures such as dolphins and tuna could get “megadoses.”

Marine biologists regularly collect and study shellfish to monitor the health of the greater ecosystem. Since the spill began last April, researchers have seen orange-tinged droplets of in the blue crap larvae, a condition that biologist Harriet Perry has never seen before. “In my 42 years of studying crabs I’ve never seen this,” she said.

It is too soon to tell what percentage of the crab larvae population is affected, but Perry said that at least 40 percent of their known habitat has been hit by the oil spill. If large numbers of larvae are contaminated, scientists say it is “virtually certain” that a the blue crab population will be hit hard, though it remains unclear just how large the die-off would be. Spawning season for blue crap is from April to October, with July and August the peak months.

Crab country – fisherman in the food web

Crab fishing is big business in Luisiana, indeed along the entire Gulf coast, with a typical 33 million pound harvest worth $300 million annually in Luisiana alone. The longterm sustainability of the harvest has many lifelong Gulf fisherman worried:

“If they’d let us go out and fish today, we’d probably catch crabs,” said Luisiana fisherman Glen Despaux. “But what’s going to happen next year, if this water is polluted and it’s killing the eggs and the larvae? I think it’s going to be a long-term problem”

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