Coral mortality increases wave energy reaching shores protected by reef flats: Examples from the Seychelles

Sheppard, C., Dixon, D. J., Gourlay, M., Sheppard, A. and Payet, R. (2005) Coral mortality increases wave energy reaching shores protected by reef flats: Examples from the Seychelles. Estuarine Coastal And Shelf Science, 64 2-3: 223-234. doi:10.1016/j.ecss.2005.02.016


Author Sheppard, C.
Dixon, D. J.
Gourlay, M.
Sheppard, A.
Payet, R.
Title Coral mortality increases wave energy reaching shores protected by reef flats: Examples from the Seychelles
Journal name Estuarine Coastal And Shelf Science   Check publisher's open access policy
ISSN 0272-7714
Publication date 2005-01-01
Sub-type Article (original research)
DOI 10.1016/j.ecss.2005.02.016
Volume 64
Issue 2-3
Start page 223
End page 234
Total pages 12
Editor D. S. McLusky
S. D. Sulkin
E. Wolanski
Place of publication London
Publisher Academic Press Ltd Elsevier Science Ltd
Collection year 2005
Language eng
Subject C1
290899 Civil Engineering not elsewhere classified
770499 Other
0905 Civil Engineering
Abstract In the granitic Seychelles, many shores and beaches are fringed by coral reef flats which provide protection to shores from erosion by waves. The surfaces of these reef flats support a complex ecology. About 10 years ago their seaward zones were extensively covered by a rich coral growth, which reached approximately to mean low water level, but in 1998 this was largely killed by seawater warming. The resulting large expanses of dead coral skeletons in these locations are now disintegrating, and much of the subsequent modest recovery by new coral recruitment was set back by further mortalities. A mathematical model of wave energy reaching shorelines protected by coral reef flats has been applied to 14 Seychelles reefs. It is derived from equations which predict: (1) the raised water level, or wave set-up, on reef flats resulting from wave breaking, which depends upon offshore wave height and period, depth of still water over the reef flat and the reef crest profile, and (2) the decay of energy from reef edge to shoreline that is affected by width of reef flat, surface roughness, sea level rise and 'pseudo-sea level rise' created by increased depth resulting from disintegration of coral colonies. The model treats each reef as one entity, but because biota and zonation on reef flats are not homogenous, all reefs are divided into four zones. In each, cover by both living and dead biota was estimated for calculation of parameters, and then averaged to obtain input data for the model. All possible biological factors were taken into account, such as the ability of seagrass beds to grow upwards to match expected sea level rise, reduction in height of the reef flat in relation to sea level as zones of dead corals decay, and the observed 'rounding' of reef crests as erosion removes corals from those areas. Estimates were also made of all these factors for a time approximately a decade ago, representing a time before the mass coral mortality, and for approximately a decade in the future when the observed rapid state of dead coral colony disintegration is assumed to have reached an end point. Results of increased energy over the past decade explain observations of erosion in some sites in the Seychelles. Most importantly, it is estimated that the rise in energy reaching shores protected by fringing reefs will now accelerate more rapidly, such that the increase expected over the next decade will be approximately double than that seen over the past decade. (c) 2005 Elsevier Ltd. All rights reserved.
Keyword shores
coral reefs
sea level rise
coral mortality
erosion
wave energy
Seychelles
Set-up
Climate-change
Indian-ocean
Fish Communities
El-nino
Attenuation
Morphology
Recovery
Impacts
Future
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Civil Engineering Publications
2006 Higher Education Research Data Collection
 
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Citation counts: TR Web of Science Citation Count  Cited 113 times in Thomson Reuters Web of Science Article | Citations
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Created: Wed, 15 Aug 2007, 16:01:31 EST