Deep Reef Discoveries

The Catlin Seaview Survey announced that its exploration of the Great Barrier Reef and the Coral Sea, to depths well beyond the reach of scuba divers, has discovered healthy coral habitats. The expedition is revealing new insights into the state of the iconic Great Barrier Reef, especially the deep reef that is almost totally unexplored by scientists. Speaking from the research boat where he is leading the Deep Reef Survey, Dr Pim Bongaerts, of the University of Queensland’s Global Change Institute, said, “The Holmes and Flinders Reefs in the Coral Sea are renowned for having been badly damaged. Yet we have found their deep reef zone is hardly disturbed at all. In fact the most striking thing is the abundance of coral on the deep reef. What has blown me away is to see that even 70-80 metres down, there are significant coral populations.” Professor Ove Hoegh-Guldberg, Chief Scientist for the Catlin Seaview Survey, said that a recent report from The Australian Institute of Marine Science (AIMS) showing that the Great Barrier Reef has lost half its coral cover in the last 27 years was a study of the situation in the shallow reef. “Our work in the deep reef is already casting a new light on our understanding. Up until now our knowledge was limited to the shallow reefs accessible by scuba diving. In reality, that provided us with an incomplete picture. Now, using ROVs (Remote Operated Vehicles), we are able to get below 30 metres and down to 100 metres, revealing a wholly different picture which now includes the deep reef environment,” Ove commented.

The Deep Reef Survey team has completed four of its ten planned surveys at areas along the lengths of the 2,300 kilometre reef system and its outlying atolls. It has already produced five specimens for further analysis, which may prove to be new species, and it expects to collect many more.

Dr. Carden C. Wallace, a world expert on corals at the Museum of Tropical Queensland, said she is struck by what the Catlin Seaview Survey is finding. “Up to now we’ve had only a very small number of specimens from deep reefs, mostly dredged samples, totalling about 20. Yet already, the Catlin Seaview Survey has collected more than 1,000 deep coral specimens (below 40 m) during these early stages of the Catlin Seaview Survey – with collections still ongoing. It is not only that they are finding abundant communities at depth, but some of these turn out to be quite diverse. Using the ROV vehicles to film and collect samples at this scale is simply unprecedented in Australian waters.

The discovery of wide areas of healthy deep reef raises the possibility that they could provide a refuge for corals that are under stress in the shallow reef.

Dr Pim Bongaerts said, “This mesophotic layer, just beneath shallow reefs, could provide coral recruits for the upper levels of the reef, providing a potential for them to help in the recovery of areas heavily damaged by climate change-related impacts. At the moment we know little about the extent of larval movements between the shallow and deep reef, but we are seeing species that exist in both zones.” He continued, “Deep reefs are unique eco systems, that have been hidden away and unexplored, yet they are very much part of Australia’s natural heritage.
 “There are clear differences we’re observing. Corals are much flatter, more plate-like than the branching and domed shapes seen nearer the surface. This is the coral responding to the reduced light conditions and spreading out to maximize their exposure to light. So far below the surface, the light is blue because all other parts of the spectrum have been filtered out. It is a monochrome world until you turn on strong lights to reveal amazing, beautiful, fantastic colours,” Dr. Bongaerts concluded.

About the survey

The Catlin Seaview Survey, which launched in September, has embarked on a mission to create a baseline study of both shallow and deep reefs around the world. Its shallow reef survey is using a unique 360-degree camera system to document wide areas of the reef and ROV vehicles to record the deep reef. Further experiments and long-term monitoring of deep reefs will also be undertaken. Its baseline study will provide a global record of reef systems as a reference point for future studies and monitoring of changes in coral habitats that are imperiled by climate change. Dr Pim Bongaerts added: “It is surprising in this day and age, that below some of the most well known reefs which are so popular with divers, there is an almost entirely unexplored world and as a result an enormous amount of science to be done.” Anyone can get a flavour of the expedition experience by taking a user-controlled ‘virtual dive’ onto the reef on the expedition’s website and via the Street View feature of Google Maps. The virtual dive allows people to use their own keyboard controls to explore the reef for themselves.