Antarctic invasion by crabs and sharks might endanger native marine life

Populations of predatory king crabs are already living in deeper, slightly warmer water," says Aronson. "And increasing ship traffic is introducing exotic crab invaders. When ships dump their ballast water in the Antarctic seas, marine larvae from as far away as the Arctic are injected into the system."

Fast-moving, shell-crushing predators, dominant in most places, cannot operate in the icy waters of Antarctica. The only fish there—the ones with the antifreeze proteins—eat small, shrimp-like crustaceans and other soft foods. The main bottom dwelling predators are slow-moving sea stars and giant, floppy ribbon worms.

Antarctica's coastal waters are warming rapidly. Temperatures at the sea surface off the western Antarctic Peninsula went up 1°C in the last 50 years, making it one of the fastest-warming regions of the World Ocean.

If the crab invasion succeeds, it will devastate Antarctica's spectacular fauna and fundamentally alter its ecological relationships. "That would be a tragic loss for biodiversity in one of the last truly wild places on earth," says Aronson. "Unless we can get control of ship traffic and greenhouse-gas emissions, climate change will ruin marine communities in Antarctica and make the world a sadder, duller place."

         The crustaceans have been found way down on the deep slopes off the Antarctic continental shelf - where the water is slightly warmer than elsewhere.

引自:ScienceDaily (Feb. 4, 2009)

As the upper waters continue to warm, nothing will stop the king crabs from moving up onto the continental shelf and feasting. That will “hammer” the old seafloor communities, said marine scientist Richard Aronson of Dauphin Island Sea Lab and the University of South Alabama.

“We expect the populations of seafloor invertebrates to take a dive,” he added.

“The species in the Antarctic (seafloor) have no defense for shell-crushing predators,” said extreme species researcher Brad Seibel, also of the University of Rhode Island. “I don’t think that anyone was really aware of this issue,” he added.

Sharks are also set to return to the sea floor around Antarctica, with the most likely candidate being the spiny dogfish, which are already abundant off the coast of South America, poised for invasion as soon as the water gets a tad warmer.

According to Wilga, if there’s any shark that can eke out a living first in the warming waters, it is the diminutive and virtually global spiny dogfish.

Though the predator invasion of Antarctica may be unavoidable, it could be moderated if something is done immediately to reduce emissions of global warming greenhouse gases into the atmosphere.

“As global warming proceeds, the deeper water around Antarctica will only get warmer,” said Aronson.

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