Researchers have uncovered how animals in Antarctica managed to survive glacial periods thousands of years ago when sea-ice encroached on their habitats.

DNA evidence indicates that sea creatures used a variety of techniques, from surviving in the deep sea, to retreating into pools of unfrozen seawater. Scientists hope that by looking back in time it will help predict the likely impact of global warming on the Southern Ocean.

Natural climate cycles have caused massive glaciations on 40,000 and 100,000 year cycles over the past five million years. At times of maximum glaciation, sea-ice extended out into the Southern Ocean blocking sunlight from the surface waters, preventing phytoplankton from photosynthesising and hence cutting the food chain off at its source.

Additionally, massive glaciers and ice-sheets extended far out onto the continental shelf, scoring the sea-floor and destroying the habitat of many animals.

Biologists have never understood how animals in the seas surrounding Antarctica survived these Pliocene-Pleistocene glacial cycles. Was all the fauna of the Southern Ocean destroyed? Were animals able to seek refuge in the deep sea and recolonise from there? Or did marine animals seek refuge outside of the Southern Ocean and recolonise Antarctica from other Oceans?

In a paper published in Trends in Ecology & Evolution, researchers at National University of Ireland Galway and LaTrobe University in Australia provide the answer.

Dr Louise Allcock, a zoologist from National University of Ireland Galway’s Ryan Institute, explains. “We found the answer in the DNA of animals that are found in the Southern Ocean today. I’ve been studying Antarctic octopuses for many years and looking at the patterns of variation in their DNA.
For more, read this week's Galway City Tribune.