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Antarctic Octopus Provides Clues To Ice Sheet Collapse

May 10, 2012
Image Credit: University of Liverpool

Brett Smith for Redorbit.com

A joint team of UK and Australian researchers has found that two separate groups of Antarctic octopuses, from the Ross and Weddell seas on different sides of the continent, are almost genetically identical. This suggests that the two seas, which are now separated by the West Antarctic Ice Sheet, were once joined together, possibly a result of the partial collapse of the continental ice sheet.

Researchers analyzed the genes of 450 Turquet’s octopuses collected from 2005 to 2010 during the Census of Antarctic Marine Life. A Turquet´s octopus can grow up to 15 cm in body length and is typically prey for seals and the Patagonian toothfish, or Chilean Sea Bass.

“We expected to find a marked difference between Turquet´s octopuses living in different regions of the ocean, particularly between areas that are currently separated by approximately 10,000km of sea,” said Phill Watts, from the University of Liverpool´s Institute of Integrative Biology. “These creatures don´t like to travel and so breeding between the populations in the Ross and Weddell Seas would have been highly unusual.”

“We found, however, that they were genetically similar, suggesting that at some point in their past these populations would have been in contact with each other, perhaps at a time when the oceans were connected and not separated by the West Antarctic Ice Sheet.  These findings agree with climate models indicating repeated periods in history when the climate was warmer, which would have released water from the ice and increased the sea levels, allowing dispersal of creatures between the Ross and Weddell Seas.”

The research team´s genetic comparisons of other octopuses around Antarctica not separated by the West Antarctic Ice Sheet illustrate the theory that there are genetic variations amongst the different groups.  They found that different factors including ocean depth and currents limited the movement of the octopus in certain areas, allowing for the different populations of octopuses to develop their own unique genetic variations.  This added further evidence that at some point in recent history this particular ice sheet might have collapsed, making the two populations on either side of the ice sheet into one homogeneous group.

“The fact that we found more similarities than we did differences supports the theory that the West Antarctic Ice Sheet could have collapsed in the past,” said study co-author Louise Allcock, from the National University of Ireland, Galway.  “It also provides further evidence that scientists should continue to raise awareness about the impact of climate change on Antarctica today.”

This potential climate change breakthrough comes just after report in the journal Nature said another Antarctic ice shelf could melt quickly over the next century. Scientists at the Alfred Wegener Institute for Polar and Marine Research in Germany calculated that the Fichner-Ronne Ice Shelf near the Weddell Sea is susceptible to warm water being driven toward it by ocean and air currents.

“Our models show that the warmer air will lead to the currently solid sea ice in the southern Weddell Sea becoming thinner and therefore more fragile and mobile in a few decades,” Dr. Frank Kauker, a researcher on the project, said.


Source: Brett Smith for Redorbit.com



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