Oil spill 'already damaging deep sea ecosystem'

As Americans anxiously waited for a slick in the Gulf of Mexico to wash up along the coast, globules of oil were already falling to the bottom of the sea, where they threatened virtually every link in the ocean food chain, from plankton to fish on dinner tables everywhere.

Meanwhile, a giant concrete-and-steel box seen as the best short-term solution to bottling up the disastrous oil was loaded onto a boat and the 100-ton contraption began its journey to the leak site about 50 miles off the Louisiana coast.

Oil has been gushing into the Gulf of Mexico at a rate of at least 200,000 gallons a day since an offshore drilling rig exploded last month and killed 11 people.

Officials hope to lower the concrete-and-steel box the size of a four-story building to the bottom of the sea by week’s end to capture some of the oil.

For marine life, though, the damage is already done, experts said.

“The threat to the deep-sea habitat is already a done deal – it is happening now,” said Paul Montagna, a marine scientist at the Harte Research Institute for Gulf of Mexico Studies at Texas A&M University-Corpus Christi.

Hail-size gobs of oil the consistency of tar or asphalt will roll around the sea’s bottom, while other bits will get trapped hundreds of feet below the surface and move with the current, said Robert S. Carney, a Louisiana State University oceanographer.

Scientists said bacteria, plankton and other tiny, bottom-feeding creatures will consume oil, and will then be eaten by small fish, crabs and shrimp. They, in turn, will be eaten by bigger fish, such as red snapper, and marine mammals like sea turtles.

The petroleum substances that concentrate in the sea creatures could kill them or render them unsafe for eating, scientists said.

“If the oil settles on the bottom, it will kill the smaller organisms like the copepods and small worms,” Mr Montagna said. “When we lose the forage, then you have an impact on the larger fish.”

Making matters worse for the deep sea is the leaking well’s location: it is near the continental shelf of the Gulf where a string of coral reefs flourish. Coral is a living creature that excretes a hard calcium carbonate exoskeleton, and oil globs can kill it.

The reefs are colourful underwater metropolises of biodiversity, attracting sea sponges, crabs, fish, algae and octopus.

“In my mind, they are at least as sensitive to contamination to oil as coastal habitat,” said James Cowan, an oceanographer at Louisiana State. “They are in deeper water, so they are kind of out of sight, out of mind.”

There are other important habitats in shallower waters, such as an ancient oyster shell reef off the Mississippi and Alabama coasts. It is a vital nursery ground for red snapper and habitat for sponges, soft corals and starfish.

Scientists are watching carefully to see whether the slick will hitch a ride to the East Coast by way of a powerful tide known as the “loop current”, which could send the spill around Florida and into the Atlantic Ocean. If that happens, the oil could foul beaches and kill marine life on the East Coast.

“Once it’s in the loop current, that’s the worst case,” said Steve DiMarco, an oceanographer with Texas A&M University-College Station. “Then that oil could wind up along the Keys and transported out to the Atlantic.”