Scientists Discover Deep-sea Corals off Barrier Reef

Scientists conducting mapping surveys on the Great Barrier Reef have come across deep-sea corals at depths that surprise researchers. A team from the University of Queensland's Seaview Survey announced the unprecedented discovery 125 meters (410 feet) below the surface at Ribbon Reef, near the Torres Strait and at the edge of the Australian continental shelf. A new exploration by a remote-operated submersible has found the reef's deepest coral yet. Coral reefs are made of colonies of polyps which secret a rocklike exoskeleton. The polyps have a symbiotic relationship with algae that provide them nutrients using photosynthesis. Because this process requires light, coral reefs thrive in clear, relatively shallow water. The Great Barrier Reef's corals typically peter out in the Great Barrier Reef around the 330-foot (100-meter) level. At greater depths, the corals are replaced by non-light-dependent sponges and sea fans. Researchers were particularly interested in how the coral reproduced at such depths. Ove Hoegh-Guldberg, chief scientist on the project, told AFP that coral had previously only been shown to exist to depths of 70 meters and the finding could bring new understanding about how reefs spawn and grow. Shallow corals mate in a synchronized spawning event triggered by the moon which Hoegh-Guldberg said would be "very hard to see" at 125m. "What's really cool is that these corals still have photosynthetic symibionts that supposedly still harvest the light," Hoegh-Guldberg told AFP. "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." The deep water corals had been found to have weathered storms on the reef much better than those closer to the surface and he said the team was also looking at how ocean acidification and warming was impacting deeper reefs. Hoegh-Guldberg said the team had been lucky to be able to dispatch the diving robot -- unusually calm conditions had allowed their ship to stop on the windward side of the reef where large waves typically prevent access. "No one's ever seen these places. It's pretty rare on the planet today," he said.