Is there a Western Indian Ocean “Coral Triangle?

The biogeography of shallow marine organisms in the western Indian Ocean (WIO) is poorly known, though there are indications of a peak of biodiversity (species and genus distributions) in the region at the northern end of the Mozambique Channel encompassed by northern Madagascar, northern Mozambique and southern Tanzania. This region is fed by the South Equatorial Current passing close to the northern tip of Madagascar, with some indications of the formation of a gyre around the Comoro Islands and the formation of large eddies that subsequently move southwards in the Mozambique Channel. The region also has the most intricate coastlines of the WIO.

This study was to investigate the oceanography of the region to determine if diversity-promoting processes are active, document levels of diversity as given by species distributions of reef building corals and reef fish, and estimate ecosystem resilience of coral reefs of the region. A historical biogeographic analysis was to be done to determine how past tectonic events and sea level changes may have influenced extant biodiversity. Analyzed together, these data sets can shed light on whether this region does function as a high-diversity hotspot in the western Indian Ocean, analogous to the ‘Coral Triangle’ center of diversity for the Asia-Pacific region. The answers to this will have relevance to regional conservation planning as has been carried out in the East Africa and Western Indian Ocean marine ecoregions, and to long term vulnerability of the region and any peripheral regions dependent on it as a larval source, to climate change.
The goal of this project was to establish diversity-creating and maintaining mechanisms, and related patterns of diversity in the Western Indian Ocean, focusing on coral reef ecosystems.

1.To determine the basic oceanography of the study region and in particular the presence and dynamics of a ‘Comoros gyre’;
2.To determine the biogeography of representative taxa in the region and in relation to peripheral regions;
3.To assess the resilience and current ecological state of coral reefs in the region;
4.To assess the possible influence of historical tectonic and sea level changes on the oceanography and evolutionary history behind current biogeographic patterns;
5.To assess current status and resilience of reefs in relation to oceanography, biogeography and human impacts to lay a platform for an integrated science and management agenda for the study region.

1.Northern Madagascar cruise data outputs, ASCLME. Roman, in preparation.
2.Comoros cruise publication, ASCLME. Roman, in preparation
3.Coral bleaching in the WIO in 2010 – regional anslysis. Obura, Macharia and colleagues. Western Indian Ocean Journal of Marine Science (in review).
4.Coral bleaching in Mayotte in 2010 – maximum impact in the region. Obura and colleagues. Marine Biology (in review).