In the Middle of the Indian Ocean

Dom and I are lucky enough to currently be at sea in the middle of the Indian Ocean on this year’s Bertarelli Foundation expedition to the Chagos Archipelago – known as the British Indian Ocean Territory. Chagos has the world’s largest no-take marine protected area and I have been involved in research here on Chagos’ reefs for the last 5 years. This year’s multi-disciplinary expedition team includes scientists from the Zoological Society of London, Stanford University, Bangor University, University of Western Australia and the University of Oxford. The team’s priorities include tagging of pelagic animals such as sharks and manta rays, maintenance of the array system to gather information on the movement of these pelagic populations in and around the archipelago, and monitoring the health of the reef ecosystem with a particular focus on the coral bleaching event that is predicted this year.

Chagos Reef Team 2016
The reef team! Left to right: Luke (crew member), Dan Bayley, Heather Koldewey, Hans Dejong, Rob Dunbar, Dominic Andradi-Brown, Ronan Roche and Catherine Head

The reef team’s work is focusing on reporting the affects of coral bleaching on the reef life here. Coral bleaching is when the coral cells expel their symbiotic zooxanthellae, which are single-celled algae that live inside the coral cells and photosynthesise providing the coral with energy and in return the zooxanthellae gain a secure environment to live. This bleaching is known to be a stress response to increases in sea surface temperature, caused by El Nino climate patterns and exuberated by human-induced global climate change. Wide spread bleaching has been reported in the archipelago in the past, most severely in 1998 and 2005 which resulted in the die-off of many corals. Importantly though Chagos reefs are so resilient, due to the lack of direct human impacts, that they recovered quicker than any other reefs in the Indian Ocean. More recently the archipelago experienced bleaching last year, which our surveys suggest has caused mortality to many of the table corals (Acropora), and as expected the reef is now beginning to bleach again this year.

Healthy Reef at Brothers
A still mostly healthy reef largely unaffected by the bleaching to date (Brothers Reef, Chagos)

As part of the reef team Dom and I have been quantifying the 3D structure of the reef itself and to see if this has any relationship with the number of bottom-dwelling reef fish, such as damselfish. We do this by filming quadrates of the reef that will later be converted into 3D models using a specially developed pipeline, designed by Grace Young in the ORC group. We also put out GoPro cameras on the quadrate locations to record the fish life, so we can compare the two.

Dom undertaking reef complexity surveys

In addition we have been undertaking surveys to quantify the health of the reef and the extent of bleaching. One of the positive things we are seeing is high numbers of coral juveniles, giving hope for the recovery of Chagos reefs.

High numbers of juvenile coral recruits on the reef