Contemplating Chagos – Outpost for coral

Image: The team lifting the SVII out of the water after a successful survey



Earlier this year, the Catlin Seaview Survey team surveyed the remote Chagos Archipelago, located in the Indian Ocean, approximately 300 nautical miles south of the Maldives. This area, known formally as the British Indian Ocean Territory (BIOT), was a remote and striking location, which only a few before us have had the opportunity to survey underwater.



An invaluable scientific reference site


The shallow reef team imaged 29 extended photographic transects, covering over 40 kilometres of coral reef, taking high-definition panoramic images every three seconds. This data consists of over 20,000 images, enough to require months of processing, resulting in a dataset we will use for years to come. The imagery will allow us to develop an estimate of the range of coral cover and habitat types for the marine protected area as a whole. This ‘big-picture’ summary of coral condition will serve as a baseline for comparison to nearly all other tropical coral reef ecosystems.


The Chagos Archipelago is an invaluable scientific reference site for understanding the impacts of global factors such as climate change, primarily because it is one of the only sites in the world nearly completely free from the local human-caused effects of overfishing, sedimentation, eutrophication (damaging nutrient enrichment, as from open sewage discharge), and marine rubbish and other pollution. The image set will also serve as a permanent record of coral condition for comparison to future condition, in this same location. With global warming, this location, like the rest of the planet, will likely be subjected to increased severity of bleaching events over the coming years. Given that this is one of the last outposts of untouched coral cover, we would hope it would be one of the last regions to be impacted. In the great uncontrolled experiment humanity is currently conducting on the planet, the Chagos Archipelago comes as close as we can to an unaffected control.



Exploring the deep


This expedition also included a deep reef survey team, exploring the coral cover in regions and depths that humans have likely never laid eyes on.  Led by Dr Paul Muir, the team collected over 1000 samples for a variety of research projects.  These include a study of global diversity and genetics of one of the main groups of reef corals, the Acropora or staghorn corals, studies on the genetics of Seriatopora hystrix and Pachyseris speciosa, and studies on the taxonomy of a number of other reef corals. The samples will be added to the collections of the Queensland Museum, which maintains the largest Indo-Pacific coral collections in the world. This global collection has been amassed from over 30 years of expeditions using a standard collection method and is the basis for many studies of coral biogeography, taxonomy and ecology.



An isolated outpost of coral health


The overall condition of the reefs in the Chagos range from good to excellent.  It was a healthy reef systems surrounded by virtually non-polluted waters, with abundant coral cover and diverse fish life including large numbers of sharks, which are unfortunately nearly gone in so many reef ecosystems. However, I wonder if it will stay this way for long, given that the Indian Ocean has already shown significant signs of warming, in particular compared to other ocean regions. Time will tell of the value of our images and collections, as the subtle signals of ecosystem change begin to take hold. For now, it is a glorious and isolated outpost of coral health, but there are clouds of change on the horizon.