Corals found at surprising depths



Australian scientists mapping the Great Barrier Reef have discovered corals at depths never before thought possible, with a deep-sea robot finding specimens in waters nearly as dark as night. A team from the University of Queensland’s Seaview Survey said the unprecedented discovery was made 125 meters below the surface at Ribbon Reef, near the Torres Strait.

Ove Hoegh-Guldberg, chief scientist, said coral was previously known only to exist to depths of 70 meters, adding the finding could expand our understanding of how reefs spawn and grow. “What’s really cool is that these corals still have photosynthetic symibionts that supposedly still harvest the light,” Hoegh-Guldberg said. “It’s interesting to know how they can handle such low light conditions. It’s very deep dusk.”

Researchers were particularly interested in how the coral reproduced at such depths. Shallow corals mate in a synchronized spawning event triggered by the moon, which Hoegh-Guldberg said would be “very hard to see” at 125 meters. “We don’t know the answer to that yet; they may be doing very different things to what shallow-water corals do.”

The deep-water corals were found to have weathered storms on the reef much better than those closer to the surface. The team was also looking at how ocean acidification and warming were affecting deeper reefs.