Coral Recovery From Bleaching in Alphonse and Bijoutier

Mortality of corals in the Alphonse group following the 1998 bleaching event was somewhat less than in the high islands of the Mahegroup. Overall mortality of corals on fore reef slopes was around 90%in shallow water and around 70-80% on vertical slopes, in comparison to values around 95 and 99% in the inner islands. Although mortality of Acroporas was nearly total, several small surviving colonies were found at a range of depths including very shallow seagrasses. In contrast with the high islands, many partially surviving Pocilloporaverrucosa colonies were found. The major survivors were Helioporacoerula (rare in the inner islands), Porites head species (probablylutea), Porites cylindrica,Porites nigrescens, Astreoporamyriophthalma, Hydnophora microconos, and Favid corals. Coral diversity was lower than in the high islands and no iploastreas or Gonioporas were seen in the Alphonse group, although these were found at every site in the high islands. Survival of corals was very high, roughly 80%, inside the Alphonse lagoon, also higher than equivalent habitats in the Inner Islands. Although the tiny human population is insufficient to cause eutrophication, evidence of high natural nutrient sources was seen. Strong upwelling is the cause of significant algae abundance in deep waters, while the lagoons at Alphonse and Saint Francois (but not Bijoutier, which lacks a lagoon) have green water which affects surrounding reefs and promotes algae growth, apparently as the result of recycling of nutrients from sea grass decomposition. Areas not affected by such sources, such as Bijoutier, are predominantly overgrown by encrusting pink calcareous algae, creating the surfaces needed for new coral settlement.

Bibliographic Details

Main Author:	Goreau, T.J.
Format:	Journal Contribution biblioteca
Language:	English
Published:	GCRA 1998-12
Subjects:	Coral reefs,
Online Access:	http://hdl.handle.net/1834/276
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