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Aldabra atoll, Seychelles

Main Contributors:

Albert Norström

Other Contributors:


The Aldabra atoll in the southern Seychelles has undergone a shift from scleractinian to softcoral dominance. Following mass-bleaching in 1997-1998, the Aldabra reef suffered large-scale mortality, as did most shallow reef communities in the western Indian Ocean. Prior to the mass-bleaching event of 1998, soft corals comprised only 3 % of the reef. Annual monitoring of the Aldabra atoll reefs since 1998 indicate no signs of recovery of hard corals. The only organism group that has been exhibiting significant changes in abundance are soft corals. Soft corals become the dominant benthic category (28 % cover) in the shallow coral communities by 2004. An interesting aspect of this regime shift is that Aldabra atoll has escaped most direct human impacts, due to its isolated geographic position and its status as a UNESCO world heritage site.

Type of regime shift

Ecosystem type

  • Marine & coastal

Land uses

  • Conservation

Spatial scale of the case study

  • Local/landscape (e.g. lake, catchment, community)

Continent or Ocean

  • Indian Ocean


  • Indian Ocean


  • Seychelles

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Key References

  1. Norström AV, Nyström M, Lokrantz J, Folke C. 2009. Alternative states on coral reefs: beyond coral-macroalgal phase shifts. Marine Ecology-Progress Series 376, 295-306
  2. Stobart B, Teleki K, Buckley R, Downing N, Callow M. 2005. Coral recovery at Aldabra Atoll, Seychelles: five years after the 1998 bleaching event. Philosophical Transactions of the Royal Society B 363, 251-255


Albert Norström. Aldabra atoll, Seychelles. In: Regime Shifts Database, Last revised 2011-03-03 10:12:00 GMT.
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