The archipelago, also known as British Indian Ocean Territory (BIOT), lies in the centre of the Indian Ocean between 5 and 7 degrees south, and consists of five coral reef atolls. The central feature of the archipelago is the Great Chagos Bank, the world’s largest coral atoll.
There are some 50 islands scattered across the Chagos atolls, but most are awash at low tide, and with the exception of the southernmost island of Diego Garcia, which currently serves as a US naval support facility, all of the islands have been uninhabitated for at least 30 years.
Coupled with the extreme geographical remoteness of the archipelago, this lack of human interference in the atolls makes Chagos one of few oceanic locations in the world with no major human impacts. The archipelago’s exhibits the highest expanses of unexploited coral reef in the Indian Ocean, as well as some of the region’s richest and most diverse tropical marine habitats.
The aim of the research expedition has been twofold. Firstly, the team has worked to improve environmental understanding and management of the Chagos Archipelago for the BIOT Administration. Part of this aim has been the development of ways to secure and further the archipelago’s conservation given the region’s political and geographical constraints. Secondly, the team has worked to improve existing knowledge of how a relatively unimpacted system of coral reefs and islands works, including better understanding of the biogeographical role of the Chagos Archipelago within the Indian Ocean.
Chagos reefs were heavily impacted by the mass coral bleaching which occurred in 1998, attributed to unseasonably high sea surface temperatures throughout the Indian and Pacific Oceans following a major El Nino event. Along with many other reef environments in east Africa and the western Indian Ocean region, Chagos reefs suffered severe mortality following this bleaching episode.
The frequency and severity of reef bleaching are forecast to increase dramatically as a result of global climate change, and there is now a critical need for increased understanding of the ways in which coral reefs may be responding to this unprecedented thermal stress.
The expedition is studying how the region’s reefs have recovered from this mortality event, as well as other, smaller bleaching episodes that have occurred since 1998.
In the absence of human impacts, the Chagos reefs seem to have recovered remarkably well, with many sites regaining their status as thriving reef communities. Some sites however, have been unable to recover from bleaching stress, and others still show evidence of repeated bleaching and mortality events in more recent years.
The results of this expedition will provide a fascinating reference study for Blue Ventures’ ongoing marine research in the more heavily exploited reef environments of Andavadoaka, Madagascar.