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Cold-Crawling

By Richard B. Aronson
Sunday, February 17, 2008

This occasional feature, written by researchers around the world, highlights new discoveries in the sciences and what they mean for your outlook.

THE BIG IDEA: The waters of the Antarctic are still way too cold for beach volleyball and sand castles, but some hardy crabs are sneaking into them for the first time in millions of years. If the temperature of Antarctica's shallow seas keeps rising, as scientists predict, even more of these fast-moving predators will make their way south, where they'll disrupt communities of giant ribbon worms, marine pill bugs, brittle stars, sea stars, sea lilies and sea spiders found nowhere else on the planet.

HOW WE DISCOVERED IT: My colleagues and I analyzed fossils and sediments from Seymour Island, near the southern tip of South America. Using a remote-controlled robotic camera, other researchers captured dramatic video footage of crabs creeping across the deep seafloor -- closer to the Antarctic shallows than ever before.

WHAT WE FOUND: The ancient fossils revealed an explosion of brittle stars and sea lilies in shallow Antarctic waters 40 million years ago, when the temperature started to drop, eventually freezing out crabs and other predators. But the video shows that crabs are back on the doorstep of their chilly habitat today, in slightly warmer water just a few hundred meters deeper.

WHY IT MATTERS: Imagine a giant, ribbon-like worm with mucus so acidic that it can scar a diver's dry suit, or armies of brittle stars crawling across the seafloor with their long, flexible arms. For millions of years, these strange animals have evolved in splendid isolation at the bottom of the world. The shallow Antarctic waters are cold enough to keep them safe for now, but the seas are gradually getting warmer and more hospitable for predators. Life in Antarctica may soon be a day at the beach -- if you're a crab.

Richard B. Aronson is a senior marine scientist with the Dauphin Island Sea Lab in Alabama.

In cooperation with Science magazine and the American Association for the Advancement of Science. For more information, visit www.sciencemag.org/wpoutlook.

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