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Scientists aboard the research vessel, Southern Surveyor, return to Hobart today with a collection of coral samples and photographs taken in the Southern Ocean at greater depths than ever before.

Using a remotely operated submersible vehicle the international research team captured images of life found on deep-sea pinnacles and valleys up to three kilometres beneath the Ocean’s surface.

During a three-week voyage, scientists from CSIRO’s Wealth from Oceans National Research Flagship and the US collaborated to retrieve examples of live and fossilised deep-ocean corals from a depth of 1650 metres near the Tasman Fracture Zone, south-east of Tasmania.

“These corals are evidence of an extinct coral reef,” says the voyage’s Chief Scientist, CSIRO Marine and Atmospheric Research’s Dr Ron Thresher. “Our sampling came up with some very old fossil corals of the type we are now seeing live and forming extensive reefs at depths of 800-1300 metres. This suggests that the reef extended much deeper in the past, but how long ago or why it died out, we don't know yet,” he says.

The composition of deep-sea corals is used to determine past ocean conditions, such as temperature, salinity and the mixing of surface and deep-water layers, over tens to hundreds of thousands of years.