Tuesday, August 12, 2008

Seals find secrets of deep Antarctic

SCIENTISTS are uncovering the deepest secrets of the freezing Antarctic waters by enlisting elephant seals to carry probes to places never before reached by humans.

The seals’ diving ability is being used to collect data from far beneath the ice shelves of the Antarctic coastlines as well as from the open sea.

The creatures can reach depths of 6,500ft, so revealing information about the ocean’s greatest mysteries. Scientists from the British Antarctic Survey (BAS) and St Andrews University attached miniaturised sensors to about 80 seals, then proceeded to track them.

“The sensors are so good that they can record water temperature, salinity and pressure – even tell us what the animal was doing,” said Iain Staniland, a seal and penguin expert at BAS.

The seals were tagged at the islands of South Georgia, Kerguelen and Macquarie in the Southern Ocean, and at the western coast of the Antarctic Peninsula. Data from the seals were then transmitted back to land via satellite when they surfaced.

“The Southern Ocean is the hardest place in the world to obtain oceanographic data, especially during the winter,” said Mike Meredith, head of the atmosphere and ocean group at BAS. “The seals collected data from deep seas we couldn’t ordinarily access due to remoteness and harsh environments.”

The project’s success has led researchers to tag other marine creatures, such as penguins, fur seals and even albatrosses.

“We are designing very small, light tags to fix to birds so we can gather information on the Antarctic climate,” said Staniland. Such data are vital for understanding the processes that keep Antarctica frozen, and for measuring its responses to phenomena such as climate change. One theory is that the Antarctic stays cold because of a circumpolar current, whose low temperature cools the air above, so effectively insulating the continent.

In recent years, however, some regions, such as the Antarctic Peninsula, have shown signs of warming, and many ice shelves have been breaking up. The data collected by elephant seals could show if warmer currents are disrupting the polar circulation.

The research has also provided intriguing insight to the lives of one of the Antarctic’s most elusive mammals. Elephant seals only come ashore for short periods – once in September-October (to breed), then again in January (to moult). The other nine months are spent entirely at sea – mostly underwater.

Fascinatingly, elephant seals often take catnaps while drifting 1,500ft or more beneath the ice or waves. Scientists believe they have evolved this ability because they have to sleep, yet to do so on the surface puts them at risk of attack by killer whales and sharks. Researchers such as Staniland believe the seals’ most astonishing feature, though, is their ability to recover from a deep dive and head back underwater in just a couple of minutes.

“Diving builds up lactic acid in their muscles and empties their blood of oxgyen, but they reverse that within a few minutes and dive again,” he said. “It is a truly amazing feat.”

However, the diving ability of elephant seals may be rivalled by certain species of whale, in particular Cuvier’s beaked whale. In waters off Italy, this creature was recently found to be capable of reaching a depth of 6,200ft. While this is no deeper than the maximum of the elephant seals, the whale has shown itself able to stay down there for up to 85 minutes.

Original here

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