Scientists say spill altering food chain

Health news Health & Medical News Scientists say spill altering food chain

Story Photo: A baby Kemp's Ridley sea turtle
A baby Kemp's Ridley sea turtle

NEW ORLEANS - Scientists are reporting early signs that the Gulf of Mexico oil spill is altering the marine food web by killing or tainting some creatures and spurring the growth of others more suited to a fouled environment.

Near the spill site, researchers have documented a massive die-off of pyrosomes - cucumber-shaped, gelatinous organisms fed on by endangered sea turtles. Along the coast, droplets of oil are being found inside the shells of young crabs that are a mainstay in the diet of fish, turtles, and shorebirds.

And at the base of the food web, tiny organisms that consume oil and gas are proliferating. If such impacts continue, the scientists warn of a grim reshuffling of sealife that could, over time, cascade through the ecosystem and imperil the region's multibillion-dollar fishing industry.

Federal wildlife officials say the impacts are not irreversible, and no tainted seafood has yet been found. But Rep. Edward J. Markey (D., Mass.), who chairs a House committee investigating the spill, warned Tuesday that the problem was just beginning to unfold and that toxic oil could be entering seafood stocks as predators eat contaminated marine life.

"You change the base of the food web, it's going to ripple through the entire food web," said marine scientist Rob Condon, who found oil-loving bacteria off the Alabama coastline more than 90 miles from BP's collapsed Deepwater Horizon drill rig. "Ultimately, it's going to impact fishing and introduce a lot of contaminants into the food web."

The food web is the fundamental fabric of life in the gulf. Once referred to as the food chain, the updated term reflects the cyclic nature of a process in which even the largest predator becomes a food source as it dies and decomposes.

What has emerged from research are snapshots of disruption across a swath of the northern gulf. It stretches from the 5,000-foot-deep waters at the spill site to the continental shelf off Alabama and the shallow coastal marshes of Louisiana.
Much of the spill - estimated at up to 182 million gallons of oil and 12 billion cubic feet of natural gas - was broken into small droplets by chemical dispersants at the site of the leaking wellhead. That reduced the direct impact to the shoreline and kept much of the oil and natural gas suspended in the water.

But immature crabs born offshore are suspected to be bringing that oil - tucked into their shells - into coastal estuaries from Pensacola, Fla., to Galveston, Texas. Oil carried by small organisms for long distances means the spill's effects could be wider than previously suspected, Tulane professor Caz Taylor said.

Chemical oceanographer John Kessler and geochemist David Valentine spent two weeks sampling the waters in a six-mile radius around the BP-operated Deepwater Horizon rig. More than 3,000 feet below the surface, they found natural gas levels had reached about 100,000 times normal, Kessler said.

Already those concentrations are pushing down oxygen levels as the gas gets broken down by bacteria, Kessler and Valentine said.

When oxygen levels drop low enough, the breakdown of oil and gas grinds to a halt and most life can't be sustained. The researchers also found dead pyrosomes covering the gulf's surface in and around the spill site.

The scientists said they believed the pyrosomes had been killed by toxics in the oil because they had no other explanation, but they plan further testing.

Source: Philly.com Health News , By Matthew Brown and Ramit Plushnick-Masti

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