Comparative Effects of Different Disturbances in Coral Reef Habitats in Moorea, French Polynesia

Mélanie L Trapon,Lucie Penin,Morgan S Pratchett

doi:10.1155/2011/807625

Abstract

Degradation and loss of critical coastal habitats has significant ramifications for marine fisheries, such that knowledge of changes in habitat quality and quantity are fundamental to effective ecosystem management. This study explores changes in the structure of coral reef habitats, specifically changes in coral cover and composition, in Moorea, French Polynesia, to assess the independent and combined effects of different disturbances since 1979. During this period, reefs on the north coast have been subject to coral bleaching, severe tropical storms, as well as outbreaks ofAcanthaster. Coral cover varied significantly among years, showing marked declines during some, but not all, disturbances. The greatest rates of coral loss coincided with outbreaks ofA. planci. Moreover, successive disturbances have had differential effects among coral genera, leading to strong directional shifts in coral composition.Acroporais declining in abundance and coral assemblages are becoming increasingly dominated byPocillopora and Porites. Observed changes in the cover and composition of corals are likely to have further significant impacts on the reef fish assemblages. Given that significant disturbances have been mostly associated with outbreaks ofA. planci, rather than climate change, effective ecosystem management may reduce and/or delay impending effects of climate change.

Highlights

Disturbances play an important role in the structure and dynamics of marine communities and are a necessary part of ecosystem dynamics [1,2,3,4]
Coral cover has not exhibited a systematic decline through time, rather live coral increased to >50% on outer reef slopes in 1991, and in 2004, immediately prior to the most recent outbreak of A. planci (Figures 2 and 3)
There is limited data on chronic disturbances affecting the study locations in Moorea, it appears that periodic depletion of live corals is largely explained by the occurrence of acute disturbances (Figures 2 and 3), including bleaching, cyclones, and outbreaks of A. planci, all of which have contributed to significant coral depletion elsewhere throughout the Pacific [7, 12]

Summary

Introduction

Disturbances play an important role in the structure and dynamics of marine communities and are a necessary part of ecosystem dynamics [1,2,3,4]. Moderate levels of disturbance make an important contribution to increasing biodiversity [5]. The loss of reef-building corals is likely to have major impacts on the biodiversity, productivity, and biological functioning of coral reef ecosystems [11, 12]. Changes in the structure and quality of benthic reef habitats are the most important driver of changes in the abundance of reef fishes (including some large piscivorous species), having a greater influence than extractive fisheries [13, 14]

Methods

Results

Conclusion