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Status and Recovery of the Coral Reefs of the Chagis Archipelago, British Indian Ocean Territory

  • Saturday, 20 September 2008 23:00
Harris, A. and Sheppard, C. - CORDIO Status report 2008

Abstract

Surveys of reef benthos and hard coral recruits were carried out between February and March 2006 at 19 reef sites in 5 atolls of the archipelago. Results showed that all atolls appear to have shown strong recovery in terms of benthic cover after the 1998 bleaching and mortality event.

Surveys of reef benthos and hard coral recruits were carried out between February and March 2006 at 19 reef sites in 5 atolls of the archipelago. Results showed that all atolls appear to have shown strong recovery in terms of benthic cover after the 1998 bleaching and mortality event. Reef benthos composition varied greatly between survey sites, and highly significant differences in reef composition were recorded between different atolls, and between different depths at all atolls, showing considerable unevenness in recovery.

New coral recruitment is also strong, such that even the lowest of the Chagos recruit densities are an order of magnitude higher than the rates of
recruitment of new corals documented at reefs in South Asia, the central Indian Ocean, and the East African Coast. Chagos recruitment is 6 m-2 to 28 m-2 compared to other reported values of 0.4-0.6 recruits m-2 elsewhere.

Despite observations of several subsequent shallow water bleaching events including a substantial, recent localised coral mortality at Egmont atoll within the previous year, evidence of archipelago-wide recovery ofreef habitats as notable as this remains unrecorded elsewhere in the Indian Ocean. Significant gaps remain in current understanding of the number and scale of bleaching episodes that have taken place since
the 1998 mass mortality event. Given the critical biogeographical role of Chagos in the Indian Ocean marine ecosystem, and the importance of the archipelago as a reference site for studying environmental change in the absence of direct anthropogenic interference, greater levels of long-term monitoring and ecological research are needed to better understand the responses and trajectory of recovery of the region’s coral reef communities.