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Title: Reef regeneration at Alphonse Atoll, western Indian Ocean following the 1997-98 ocean warming event
Author: Hagan, Annelise Baugh
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2004
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Following the 1997-98 ocean warming event, extensive coral bleaching and mortality occurred world-wide. Alphonse Atoll in the Southern Seychelles (7°1’S; 52°44’E) is a suitable site for the investigation of reef recovery after bleaching due to its manageable size (11.28 km2) and its geographical isolation, making it a natural laboratory unaffected by anthropogenic impacts. One year after the bleaching event, scleractinian cover had greatly reduced (10% cover) but macroalgal cover had increased (up to 27% cover). This high level of macroalgae did not persist, and over time, scleractinian cover increased, reaching a maximum of 23% cover by 2003. Despite the increased percentage scleractinian cover 1998-2003, there was no associated increase in coral diversity, with much of the increase being attributed to colonisation by opportunist species of Pocillopora and Acropora spp. Coverage of calcareous algae increased greatly following the bleaching event, from a maximum of 10% cover in 1998 to 40% cover in 2003.  Rubble comprised one third of the benthos in 1998 and remained at this level throughout the 5 year monitoring period. Depth and aspect significantly influenced the benthic communities. A ‘phase shift’ from a ‘hard’ reef community to a ‘soft’ reef community, reported elsewhere, has not occurred at Alphonse but an altered coral community exists in the post-bleaching period. Large skeletons (1-3 m diameter) of Porites spp., Lobophyllia spp., colonised by Pocillopora spp. and to a lesser extent Acropora spp., suggest that the Alphonse fore-reef slope may be in an interim phase of development, through which the coral community must pass before regaining the high levels of coral coverage and diversity.  Recruitment patterns, from local refugia versus long-distance dispersal, are discussed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available