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Ancient climate secrets raised from ocean depths

remote-1.jpgLaunching the ABE from Southern Surveyor. Image credit – CSIRO

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.

remote-3.jpgFossil corals collected at the Sisters Seamount, Huon Marine Reserve, at a depth of 1450m. The large coral in the centre is a fossil of Desmophyllum dianthus, a solitary species. It is growing on a fossil specimen of the reef building coral Solenosmilia variabilis. Image credit – CSIRO

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.

Dr Thresher says over the coming year the samples will be examined to determine when these newly discovered reefs existed and if their extinction can be related to long-term climate patterns.

‘The voyage was a success despite some of the roughest conditions ever experienced by the team, particularly in deploying the ABE.’ 

remote-2.jpgThe reef community at 2250m depth in the Tasman Fracture Zone Marine Reserve. The large organism in the foreground is a gorgonian coral, while the smaller organisms attached to the rock around it are gorgonshead corals and deep-sea stalked barnacles. In the background can be seen a glass sponge (the object growing out on a stalk). Image credit – Woods Hole Oceanographic Institute ABE Program