Seafloor creatures destroyed by ice action during ice ages

The ice ages made massive changes to the Earth’s landscape

The ice ages made massive changes to the Earth’s landscape. But what was happening below the ice in the oceans?

Research by marine scientists reveals that it was a time of mass destruction as whole communities of animals were wiped out by ice sheets scouring the sea floor.

In the past it has been thought that these ecosystems somehow dodged extinction by recolonising from nearby habitats that escaped obliteration. But researchers at the National Oceanography Centre, Southampton (NOC) and the British Antarctic Survey (BAS) reveal a bleaker scenario.

Dr Sven Thatje, an ecologist at NOC has been working with geoscientists, Dr Claus-Dieter Hillenbrand and Dr Rob Larter at BAS examining one of the harshest environments on Earth – the Antarctic seafloor.

Writing in the October issue of Trends in Ecology & Evolution the scientists provide new evidence that suggests that seafloor organisms were either erased by the advance of ice sheets across the Antarctic continental shelf or starved to death as links in the food chain were broken by the permanent ice cover. There would have been no refuge for shallower living animals further down the continental slope, as huge sediment slides would have buried them. Typically these ecosystems would have been made up of sponges, urchins, sea fan corals, and starfish.

Dr Thatje said: ‘We show that during ice ages seafloor organisms emigrated to the deep sea – below the effects of the sediment slides and ice. From there, organisms may have invaded open marine shelters of the Antarctic shelf, which were not affected by the advance of ice masses. Or these animals may have recolonised the Antarctic shelf from the deep-sea during the warm period following each ice age.

‘Either way it is an impressive feat against the odds as the extreme cold means that these animals respond much more slowly to the destruction of their habitat than elsewhere in the oceans. They have lower metabolic rates that lower their growth and reproductive rates. Elsewhere in the oceans, a brisingid starfish would reproduce annually and live for ten years. In the Antarctic these starfish can reach 100-years-old but reproduce only once every ten years. This means that full community recuperation takes up to hundreds of years.’

Dr Claus-Dieter Hillenbrand explained: ‘Until now it was commonly thought that the destructive action of the ice sheets was not significant enough to eradicate all the fauna and that desolate patches were recolonised from surrounding areas. But our research confirms that the destruction was wholesale with very little surviving. Even today calving icebergs ploughing across the seafloor destroy everything in their path. Imagine the impact of ice sheets during the ice ages that covered a much wider area in a time of lower sea levels.’

The team’s research will lead to a radical rethink of the evolutionary history of Antarctica as the work challenges all the accepted theories. The scientists argue that shallow water animals were retreating to the deep ocean and then returning to recolonise Antartica’s shelf seas. Clues to how these two very different communities could have achieved this may lie in the animals’ DNA.

Sven Thatje continued: ‘Our work means that the text books will need to be rewritten. Our next task is to reconstruct what happened in Antarctica during these periods of climate change and study the genetic and biological links between deep sea and shallow water communities.’

Notes to Editors

For further information contact the National Oceanography Centre, Southampton Press Office – Kim Marshall-Brown, tel: +44 (0)2380 596170 email: kxm@noc.soton.ac.uk or the British Antarctic Survey Press Office – Amanda Lynnes, tel: +44 (0)1223 221414, mob:07740 822229, email: asly@bas.ac.uk

For interviews please contact Sven Thatje – +44 (0)23 8059 6449 or email svth@noc.soton.ac.uk, Claus-Dieter Hillenbrand Claus-Dieter Hillenbrand +44 (0)1223 221340, e-mail hilc@bas.ac.uk Robert Larter +44 (0)1223 221573, e-mail rdla@bas.ac.uk

Picture Editors: Pictures of scenery and of scientists working and diving in Antarctica can be accessed at: ftp://ftp.nerc-bas.ac.uk/pub/photo/sea_floor_creatures/ and are also available from the BAS Press Office as above.

The National Oceanography Centre, Southampton was previously known as the Southampton Oceanography Centre until 1st May 2005. The Centre is the UK’s focus for oceanography and is a partnership between the Natural Environment Research Council and the University of Southampton. For more details visit www.noc.soton.ac.uk

British Antarctic Survey is a world leader in research into global issues in an Antarctic context. It is the UK’s national operator and is a component of the Natural Environment Research Council. It has an annual budget of around £40 million, runs nine research programmes and operates five research stations, two Royal Research Ships and five aircraft in and around Antarctica. More information about the work of the Survey can be found at www.antarctica.ac.uk

Kim Marshall-Brown
Press Officer
kxm@noc.soton.ac.uk
Tel: +44 (0)23 8059 6170
Fax: +44 (0)23 8959 6101

http://www.noc.soton.ac.uk/index.php

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Previously known as Southampton Oceanography Centre, on the 1st May 2005, the centre became the National Oceanography Centre, Southampton. www.noc.soton.ac.uk