Predators return

From Boston, at a meeting of the American Association for the Advancement of Science

Antarctica may be the battleground for the next world war. Crabs, sharks, and other predators vanquished from the frigid continent millions of years ago are ready to strike back, researchers say.

Propelled by the fast-warming Southern Ocean, the invaders’ return will hit hardest animals such as brittle stars, which evolved within a food chain of little predation, says Richard Aronson, an ecologist at the Dauphin Island Sea Lab in Alabama.

Beginning about 40 million years ago, temperatures in Antarctic waters plummeted by 10°C, Aronson says. While crabs, sharks, and other bony fish fled to warmer waters, benthic marine animals flourished. Without shell-crushing predators, Antarctic animals developed few defenses, such as thick, ridged shells. “They are ecological throwbacks to an earlier time,” Aronson says.

But many predators are banging on Antarctica’s door. Aronson’s team found that king crabs have inched closer to the shore and now hover half a kilometer from the continental shelf, at depths of around 1,100 meters, where the water has warmed. They could spread to near-shore waters in 50 years, Aronson says. Spiny dogfish, a shark found off South America, may also be ready to pounce. “This is the last stand for pristine marine communities,” he says.