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Friday, March 5, 2010

how low will you go for a free lunch? How about the dead zone?

FORENSIC archaeologists have for years been using pigs to study how the human body decomposes as part of research into murders and mass killings.

But sometimes scientists uncover things they were never expecting.

While running experiments at how the body decomposed in sea water (using pig carcasses of course), scientists in Canada found deep sea dwelling animals risk their own lives to take a free lunch and a chance on feeding at great depths.

Low-oxygen (hypoxic) zones are caused by the nutrient-rich run-off from agricultural land. This feeds algae in the ocean. When this algae dies, sinks and decomposes, it consumes most of the vital oxygen supply in the water, leading to what are known as dead zones - areas where nothing can survive for long.

But the research, coordinated with Canada’s VENUS project, has found creatures are prepared to push the envelope for food.

In one case, the project filmed several six-gill sharks annihilated a carcass, eliminating it within a day at more than 900 feet below sea level.

The scavenger animals usually hang out at shallower depths, where oxygen levels are higher. But the pig carcasses attracted a daring crowd. If the crabs, squat lobsters and other animals stay too long in oxygen-depleted waters, they will suffocate.

The lead researcher, Verena Tunnicliffe of the University of Victoria, said the scientists were very surprised to see how far animals pushed their limits to go after an enticing meal.

"This big hunk of meat on the seafloor represented a good food source for these marine creatures," she told the BBC.

"Scavengers are very important in the world. They're what allow things to restore."

The study placed three pigs into very oxygen-poor zones in the Saanich Inlet, which is off the coast British Columbia.

She added: "On day one, we lowered the pig. By day two, we've had crabs and shrimp, then octopus. Then sea stars arrive. They've had to travel across the bottom. They know something's there and they arrive almost immediately and stay there."

At levels down to almost seven per cent oxygen in the water the animals still coped.

But at depths where the oxygen level was much lower than that severe level, nothing stirred on the pig carcass. On the seafloor, therefore, nothing feeds and bacterial decomposition is the only thing that works.

The findings will help scientists in their study of other locations, such as the Mississippi Delta, where fertilizer in upstream agricultural runoff lowers oxygen levels.

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