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King crabs invade Antarctica

The crabs are moving from the deep ocean, up the continental slope to the shallower shelf areas. Unlike most areas of the world, the shallower waters on the Antarctic continental shelf are actually slightly colder than the deeper waters of the Southern Ocean. That's because of a clockwise current of water called the Antarctic circumpolar current.

That flow of cold water keeps Antarctic marine life - especially the bottom-dwelling creatures - isolated. There are no sharks, rays or fish with bony jaws, for example, in Antarctica.

"If you look at the warming trends on the peninsula, you would expect that the crabs would come back in 40 or 50 years," Aronson said from his office in Melbourne, Fla. "But, boom, they're already here."

Not all experts agree that the crabs are destined to wreak havoc on the sea bottom. David Barnes, a marine ecologist at the British Antarctic Survey, said that the seawater temperature changes may be occurring on the surface of the ocean but that they're too small to affect animals living on the bottom.

Barnes studies colonial animals in Antarctica, such as sponges and corals, and how they fit into the ecosystem. He said not enough is known about existing crab populations - where they live and how long they have been there - to declare that climate change is causing an invasion.

At the same time, he agrees with the Swedish and U.S. researchers that there are rapid changes underway in Antarctica, especially on the Western Antarctic peninsula, a thumb of land that juts northward to the bottom of South America. There's less sea ice, for example, on the waters of the peninsula. That is causing problems for the penguins and seals that depend on sea ice for food and shelter.

"Yes, there is some cause for concern in that the rate of [environmental] change is greater than has been the case in recent millions of years," Barnes said. "Obviously, for animals to tolerate or adapt to things in a very short period of time is going to be tricky."

Niiler is a freelance writer.

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