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Scleractinian coral communities of the inner Seychelles 10 years after the 1998 mortality event

  • Monday, 12 May 2014 10:06
Harris, A., Wilson, S., Graham, N. and Sheppard, C.  2014. AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS

Abstract

1. The size structure and taxonomic composition of coral communities in the inner (Granitic) Seychelles were studied 10 years after a thermal stress-induced mass mortality event.
2. A survey of the abundance, population size structure and community composition of hard corals across 21 sites from three different geomorphological reef types on the Seychelles Bank provided high resolution data for discriminating coral communities based on diversity, taxonomic composition, colony abundance, surface area and size frequency distributions.
3. Results emphasize the severely impoverished and depauperate nature of inner Seychelles hard coral
communities, which had lower generic diversity (40 genera recorded), and lower abundance (3.3 colonies m2) of hard corals (excluding juveniles) than other coral reef regions of the Indian Ocean for which comparable data are currently available.
4. Analysis of coral communities indicated that management had no appreciable effect on juvenile or adult coral abundance at this point in time, and that low juvenile density (9.9 colonies m2) may severely limit recovery of many individual reefs in the inner Seychelles.
5. While some sites were found to have appreciable coral cover (>20%), others, including long-standing protected areas with no fishing, are now in an advanced state of erosion and framework collapse with very low juvenile coral replenishment and negligible available hard substratum suitable for coral settlement.
6. Some of these reefs may have passed the threshold of viable recovery, now being in a self-reinforcing, non-coral dominated erosional phase.
7. These findings indicate variable coral community condition, with many sites showing little sign of recovery. If persistence of live hard coral is a management goal, the existing protected areas within the Seychelles Bank may require review to ensure protection of sites with high recovery potential, while a suite of other management tools should be implemented in the remaining areas.