Unknown Corals of the Deep

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Corals are some of the most beautiful things to be found under the sea, blossoming in clusters like gardens off tropical coasts worldwide. Easily the grandest display is to be found in Australia with the Great Barrier Reef, and it seems that the reef may contain even more diversity than was once thought. The latest surveys have found Australian corals thriving at depths far greater than was ever before thought possible.

The Ribbon Reef lies near the Torres Strait at the edge of the Australian continental shelf, and certain parts of it are normally very difficult to get to. The University of Queensland’s Seaview Survey has been fastidiously charting the waters off the Australian coast with a diving robot, and were extremely fortunate to be able to use an unusually calm day to explore the windward side of the reef – normally a perilous exercise due to huge waves and cyclones. Exploring the depths of the reef, they found a huge surprise.

While deepwater corals are known in other parts of the world, their appearance in the waters here was a surprise. At a depth of 125 metres, in dark waters where very little sunlight ever reaches, they found corals. Corals which had only been recorded at depths of 70 metres previously, giving Ove Hoegh-Guldberg, the chief scientist of the team, reason to suspect that the finding may be able to give a deeper understanding of how coral reefs spawn and grow.

Hoegh-Guldberg is also quoted as saying, “What’s really cool is that these corals still have photosynthetic symbionts that supposedly still harvest the light,” which is especially remarkable because the waters in which these corals have been found are so inky and dark that human divers would have trouble seeing without artificial illumination. As well as photosynthesis, shallow water corals have reproductive cycles which are synchronised by the phases of the moon. With so little moonlight being able to penetrate to the depths at which these corals live, their spawning patterns are presently a complete mystery. It could be that these corals lead a lifestyle very different to their shallow water brethren.

The deepwater corals have also fared far better in the storms which have caused massive damage to the shallower parts of the reef. The team are now investigating how conditions such as ocean acidification and global warming are affecting these deeper reef dwellers.

The Seavew Survey has proven to be extremely successful so far, with a number of specimens which they’re currently investigating. Some species they’ve found are thought to be previously unknown in Australia, and others may even be newly discovered species. Hoegh-Guldberg summed up the team’s discoveries quite succinctly with the statement, “We are yet to discover many corners of the Earth.” Indeed we are. It’s exciting to know that there’s still more for us to discover about our planet!

Image credit: InvaderXan/flickr