Robot finds reefs in unexplored deep sea waters in Australia

An international team, led by James Cook University, says the findings were a first for this depth of the Reef.

"These reefs occur in an area known as the mesophotic zone, or 'twilight zone' because of the lower light levels found there. They have been virtually unexplored because the reefs occur well below the depths accessible to most scuba divers," Tom Bridge, who led the team, said.

The last few years have seen an increasing interest in deep water reefs around the world, however this was the first investigation of such habitats on the Great Barrier Reef, say the biologists.

They used a recently developed robot, an Autonomous Underwater Vehicle (AUV), to investigate the reef and seabed communities up to 150 metres deep along a 500 km length of the Great Barrier Reef.

The biologists examined three sites offshore from Cairns, Townsville and Mackay.
Bridge said the sites, which were located on the edge of the continental shelf, outside the outermost mapped reefs, all contained diverse coral communities comprised of a unique combination of corals.

"Some corals were members of species commonly encountered on shallow-water reefs, while others represented types rarely seen by scuba divers. Bathymetric maps of the GBR shelf-edge suggest that these deep reef habitats may be widespread in the Great Barrier Reef Marine Park, however the vast majority of them are currently unexplored.

"Understanding more about the ecology of these habitats is important due to their unique biodiversity, but also because they may provide important refuges for coral reef species from climate change impacts such as coral bleaching.

"There is growing evidence that some deeper reefs are buffered from these sorts of disturbances. Therefore, it is important to know more about them and to use that knowledge to better protect the biodiversity of the Great Barrier Reef," Bridge said.

The biologists say the AUV also collected a variety of other environmental data including multibeam swath bathymetry, conductivity depth, turbidity and chlorophyll.

The findings have been published in the latest edition of the 'Marine Ecology Progress Series' journal.