'Frozen solid' is a term often used to describe Antarctica. But that's far from the truth. The southern continent is teeming with life, and its waters are home to a stunning array of life, including sea lilies, giant ribbon worms and sea spiders. 'Frozen in time' might be a better term. But for the first time in millions of years, those unique creatures may soon have new and vicious predators. Scientists say rising temperatures from global warming are allowing shell-cracking crabs to invade Antarctic waters, and sharks may not be far behind. From Boston, Curt Nickisch reports the damage to the pristine ecosystem would be irreversible.

Climate change and its effect on Antarctica have been in the headlines a lot lately: glaciers melting? ice shelves crumbling. But a warmer Antarctic ecosystem could also mean a dramatic change in the kinds of species that populate the region. It's hard for organisms to survive in extremely chilly environments. So scientists consider the ones that do currently thrive in the Antarctic waters marvels of evolution. But now those marvels may be doomed.

Sven Thatje of the University of Southampton in England explains, "The champions of cold adaptation came at the cost of not being very flexible with higher temperatures. The temperature itself will be the final kiss."

Thatje was among several experts who spoke about the biological implications of climate change in Antarctica at the American Association for the Advancement of Science annual meeting in Boston in February.

What worries Thatje and other researchers is how greenhouse gases are warming polar waters. Over the last 50 years, surface temperatures off the Antarctic Peninsula have risen by one degree Celsius, making it one of the Earth's fastest-warming oceans. That may not seem like a big change to us, but it is to many species.

According to University of Rhode Island researcher Cheryl Wilga, there are physiological reasons why predators such as sharks cannot live in extremely cold waters. "Energy and power come at a high cost at low temperatures." And it takes energy to break the shells of many of the species in the Antarctic waters. But when it's just a couple of degrees warmer, predators don't have to be nearly as strong.

Also, in temperatures close to freezing, shell-crushing crabs in particular die from magnesium poisoning. But Wilga says when it's slightly warmer, they do just fine. "King crabs are currently massing in the deep water off the coast of Antarctica, where it's slightly warmer, about four degrees. And as surface waters continue to warm, they will move up into the shallow waters around Antarctica." That, she guesses, will take a few decades, and then sharks may not be that far behind. Researchers don't think sharks will swim to Antarctica, but they're afraid that ships can transport baby sharks in the ballast water they carry, and basically import sharks to the region.

Sharks and crabs would devastate the ecosystems at the bottom of the world, says Richard Aronson, who does research at the Dauphin Island Sea Lab in Alabama. "There are going to be winners and losers of the Antarctic fauna as these predators invade. Brittlestars are going to be hammered; they're just going to be clobbered by invading predators." He predicts that clam-like lampshells would not be in danger.

Still, he says, if warmer water predators move in, the result would be what Aronson considers a major loss in biodiversity. "It's like saying what would we care if we took Michelangelo's David and threw it the dumpster? This is about the way we want this planet to look for future generations." He is calling for a stop to global warming to keep the predators at bay.

There may also be practical implications to keeping Antarctic life the way it is. Currently U.S. scientists are looking at one polar sea organism because it may produce a therapeutic drug that could help fight skin cancer in humans. Researcher Sven Thatje says protecting the Antarctic environment is a worthy cause. "If we lose biodiversity without knowing what's actually out there, it's not only a threat to ourselves, but the world would be a much duller place, and I would not like to live in such a world," he concludes.

But unless things change, that world could be a reality. The Antarctic sea life, which has thrived for millions of years in harsh conditions, may be under... thin ice.