A trip below the surface at Ribbon Reef has revealed corals able to survive at unexpected depths.

The robotic expedition was made as part of the Seaview Survey by a team from the University of Queensland and shows that the Ribbon Reef—part of Australia's Great Barrier Reef—extends nearly twice as far down as previously thought.

"What's really cool is that these corals still have photosynthetic symbionts that supposedly still harvest the light,"

said Ove Hoegh-Guldberg, leader of the project. "It's interesting to know how they can handle such low light conditions—it's very deep dusk, you can barely make out much at the bottom."

Another mystery posed by these Leptoseris corals is one of reproduction. The mating seasons for corals living in shallower waters are governed by the moon, but with the moon barely distinguishable at depths of 125m there is a chance that the corals rooted in the deep dusk are using another mechanism in their reproductive cycle. "They may be doing very different things to what shallow water corals do," said Hoegh-Guldberg.

Corals in deeper water such as the Leptoseris of the Great Barrier Reef and Lophelia pertusa in the Gulf of Mexico also appear less easily damaged than their shallower counterparts.

The University of Queensland team is currently working to evaluate samples of corals found during the research, some of which may be entirely new to science.