BEIJING, Feb. 19 (Xinhuanet) -- It's been 40 million years since Antarctic waters were warm enough for sharks to lurk around and feed on polar prey, but rising ocean temperatures from global warming could eventually bring the toothy predators back, media reported Tuesday quoting scientists as saying.

    If sharks reenter Antarctic waters, the entire polar ecosystem will be severely altered, with the ferocious predators easily preying on a wide assortment of slow-moving, soft-bodied organisms that dominate the sea floor of the cold-water environment, said Cheryl Wilga, an associate professor of biomechanics at the evolution at University of Rhode Island.

    “Sharks and crabs are the biggest predators of benthic [bottom dwelling] invertebrates and the entire environment will change," Wilga said. 

    Sharks generally thrive in warm, tropical waters and have a high metabolic rate because they must swim constantly to aerate their gills.

    "Temperatures around the world’s coldest continent range from 28 degrees Fahrenheit, or minus-1.8 Celsius, to 5 degrees Celsius," said Brad Seibel, professor at the University of Rhode Island.

    Some sharks off the tip of South America can already survive in waters from 7 to 10 degrees C, making the transition to Antarctic waters possible in about 50 years if the current rate of ocean warming remains steady, Seibel said.

    The consequences of sharks being introduced back into this distinctive benthic ecosystem -- which is home to many primitive organisms including shrimp, ribbon worms and brittle stars --- is aggressive predation of animals not accustomed to defending themselves against strong, fast-moving animals.

    “The water only needs to remain above freezing within a few degrees year round for it to become habitable to some sharks,” Wilga said. “At the rate we’re going, that could happen this century.”

    (Agencies)