Chagos Archipelago

British Indian Ocean Territory (BIOT)
Chagos Archipelago

For our final Global Reef Expedition Mission, we traveled to the Chagos Archipelago, also known as the British Indian Ocean Territory (BIOT), a small island chain in the middle of the Indian Ocean. Chagos is home to some of the most remote, and pristine, coral reefs on Earth – 95% of which have yet to be explored.

In March and April of 2015, we conducted coral reef surveys and high-resolution mapping on many reefs surrounding the small islands of the Chagos Archipelago, including those around Victory Bank, Salomon Islands, Eagles Islands, Blenheim Reef, Danger Island, and Speakers Bank. In 2010, the British government developed the Chagos Marine Reserve, encompassing all these islands and reefs, making it the largest no-take marine protected area on Earth at the time it was established. 

BIOT Inset Map
Courtesy of Wikipedia Commons*
(Click-thru on map image to expand.)


The purpose of this research mission was to collect detailed information about the reef communities found in this remote location. The team of scientists identified and recorded population information on coral, reef fishes, algae, and invertebrates. They also identified any threats to the coral reef ecosystem, making note of any coral diseases they saw, coral bleaching, or  predation by crown-of-thorns starfish.

Bleaching reef in BIOT
Coral reefs in the Chagos Archipelago began to bleach during our research mission in 2015.

Because of its remote location, Chagos is the perfect place to study global issues that threaten the long-term survival of coral reefs. A major component of the Global Reef Expedition is to determine the resilience of coral reef communities to climate change and ocean acidification. Scientists on the Global Reef Expedition monitored ocean chemistry and looked for impacts ocean acidification may have had on the corals in the Chagos Archipelago. They also examined the diversity and efficiency of symbiotic algae that live within corals to determine if some species of coral, or their symbiotic communities, are better able to cope with rising ocean temperatures. Scientists from the Woods Hole Oceanographic Institute looked at the variation of ocean temperature over the past few centuries by studying some of the oldest and largest corals on the reef.



Another component of the mission was to use satellite imagery and on-site ground-truthing to create extremely high-resolution habitat and bathymetric maps of our study sites. Combined with photos and video footage, these maps will be some of the most detailed coral reef maps available and will be added to our online World Reef Map for anyone to see and use.

Our Findings

What we found when the expedition began were reefs teeming with life, a diverse assemblage of corals, and lots of fish. The reefs of the Chagos Archipelago were truly exceptional; they had some highest coral cover and fish biomass recorded on the Global Reef Expedition. These reefs also had more fish per square meter than in any of the 15 countries we studied on the Global Reef Expedition, the largest coral reef survey and mapping expedition in history. Unfortunately, towards the end of our two month research mission, we witnessed the beginning of what would become a catastrophic mass global bleaching event, illustrating that negative human impacts reach even the most isolated and well-protected coral reefs on Earth. 

BIOT Coral Reef
The Chagos Archipelago had the highest fish density and the second highest fish biomass of all reefs surveyed on the Global Reef Expedition.

A comprehensive summary of our findings can be found in the Global Reef Expedition: Chagos Archipelago Final Report. The data contained in this report is the last data collected in the Chagos Archipelago before the bleaching event caused mass coral mortality on the reefs. This report has been shared with government agencies, conservation organizations, and scientists interested in the health of coral reefs in the Chagos Archipelago. The report contains valuable baseline data on the state of the reef, and can directly help with ongoing management and conservation of coral reefs in the marine reserve. 

Global Reef Expedition: Chagos Archipelago Final Report

The Global Reef Expedition: Chagos Archipelago Final Report  presents the Foundation’s findings from the Global Reef Expedition mission to the Chagos Archipelago in 2015.



Global Reef Expedition Final Report: Chagos Archipelago (5 MB PDF)

Mission Team

Representatives from Woods Hole Oceanographic Institution (WHOI), Nova Southeastern University, and the Chagos Conservation Trust joined our core science team on this mission, along with scientists from Scripps Institution of Oceanography, AGRRA, University fo the Philippines, National Museum of Marine Biology and Aquarium in Taiwan, the University of Miami, NOAA, the Univerisity of Hawaii, and James Cook University. 

Meet the team

* By TUBS [GFDL or CC BY-SA 3.0], via Wikimedia Commons