The return of the last of three Antarctic marine science research vessels marks the culmination of one of Australia's most ambitious International Polar Year projects, a census of life in the icy Southern Ocean known as the Collaborative East Antarctic Marine Census (CEAMARC).

Australia's Aurora Australis and collaborating vessels L'Astrolabe (France) and Umitaka Maru (Japan) have returned from the Southern Ocean, their decks overflowing with a vast array of ocean life including a number of previously unknown species collected from the cold waters near the East Antarctic land mass.

While the French and Japanese ships have been examining the mid and upper ocean environment over the past two months, Aurora Australis had her eyes fixed on the ocean floor, using both traditional and innovative sampling equipment to capture the diversity of life.

Aurora Australis voyage leader Dr Martin Riddle says that their expedition uncovered a remarkably rich, colourful and complex range of marine life in this previously unknown environment.

"Some of the video footage we have collected is really stunning – it's amazing to be able to navigate undersea mountains and valleys and actually see what the animals look like in their undisturbed state," he said.

"In some places every inch of the sea floor is covered in life. In other places we can see deep scars and gouges where icebergs scour the sea floor as they pass by. Gigantism is very common in Antarctic waters – we have collected huge worms, giant crustaceans and sea spiders the size of dinner plates.

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"This survey establishes a point of reference to monitor the impact of environmental change in Antarctic waters. For example, ocean acidification, caused by rising atmospheric carbon dioxide levels, will make it harder for marine organisms to grow and sustain calcium carbonate skeletons.

"It is predicted that the first effects of this will be seen in the cold, deep waters of Antarctica. Our results provide a robust benchmark for testing these predictions."

CEAMARC Project Leader Dr Graham Hosie said that researchers are only beginning to understand the complex biodiversity that lies beneath the surface of the Southern Ocean and its importance in local, regional and global ecosystems.

"This research will help scientists understand how communities have adapted to the unique Antarctic environment. Our work also has wider applications, for example understanding fish community composition and structure is particularly important to explain the impacts of commercial trawling.

"Specimens collected will be sent to universities and museums around the world for identification, tissue sampling and bar-coding of their DNA. Not all of the creatures that we found could be identified and it is very likely that some new species will be recorded as a result of these voyages."

CEAMARC is part of the international Census of Antarctic Marine Life, coordinated by the Australian Antarctic Division, which will see some 16 voyages to Antarctic waters during this, the International Polar Year (2007-2009).

The Census of Antarctic Marine Life will survey the biodiversity of Antarctic slopes, abyssal plains, open water, and under disintegrating ice shelves. The census aims to determine species biodiversity, abundance and distribution and establish a baseline dataset from which future changes can be observed.

Video available at: http://www.aad.gov.au/MediaLibrary/asset/mediaitems/ml_394975880439815_see_ocean_floor_footage.mp4