If global warming continues at the current rate, sharks could inhabit the waters surrounding Antarctica, a frigid place where shell-crushing predators have not been able to survive in more than 40 million years, according to a study by University of Rhode Island Professors Cheryl Wilga and Brad Seibel presented Friday at the annual American Association for the Advancement of Science meeting in Boston.

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 Wilga, an associate professor of biomechanics and evolution.

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

Wilga and Seibel, also a professor of biology, came to the conclusion that sharks’ habitat could extend into Antarctic waters by studying their physiological limitations, including locomotion, feeding habits, metabolism and temperature restraints.

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, Seibel said.

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 Antarctic ecosystem is very unique,” Seibel said. “It doesn’t look like anywhere else and it will lose some of its unique flavor.”

In addition to the general rule that organisms in cold water maintain lower metabolisms and have less energy to expend to contract muscles, sharks that live at different depths have distinct challenges to reaching and surviving the Antarctic habitat.

Sharks that live in the water column are accustomed to warmer temperatures than some benthic sharks, but bottom-dwellers have to contend with the deep trench around Antarctica that stresses their regulatory system maintained by the circulation of two key chemicals: urea and trimethylamine oxide, or TMAO.

Sharks need TMAO to offset the presence of urea, a concentrated form of urine, which is toxic at high levels. In cold and deep water, sharks need more TMAO to survive, but will also die if the level gets too high.

Wilga and Seibel stopped short of saying the reemergence of sharks near the bottom of the world will lead to species extinction, but it would dramatically change the current ecology.

“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.”

ngarcia@projo.com