Erosion vs. Recovery of Coral Reefs after 1998 El Niño: Chagos Reefs, Indian Ocean

Sheppard, Charles; Spalding, Mark; Bradshaw, Clare; Wilson, Simon

doi:10.1639/0044-7447(2002)031[0040:evrocr]2.0.co;2

Cited by 67 publications

(83 citation statements)

References 23 publications

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“…There was no significant impact on species richness due to loss in live coral cover per se (r 2 ϭ 0.13). Consistent with studies of other forms of disturbance, this finding suggests that loss in physical structure is the main driving force in species richness declines on coral reefs after disturbance (23)(24)(25), and explains why the short-term impacts of bleaching on fish assemblages may appear to be negligible (9)(10)(11). Furthermore, because changes in species richness were correlated linearly with the extent of habitat complexity loss, there is no evidence of a threshold level of structural complexity below which species richness was maintained.…”

Section: Resultssupporting

confidence: 73%

Dynamic fragility of oceanic coral reef ecosystems

Graham

Wilson

Jennings

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

585

497

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As one of the most diverse and productive ecosystems known, and one of the first ecosystems to exhibit major climate-warming impacts (coral bleaching), coral reefs have drawn much scientific attention to what may prove to be their Achilles heel, the thermal sensitivity of reef-building corals. Here we show that climate change-driven loss of live coral, and ultimately structural complexity, in the Seychelles results in local extinctions, substantial reductions in species richness, reduced taxonomic distinctness, and a loss of species within key functional groups of reef fish. The importance of deteriorating physical structure to these patterns demonstrates the longer-term impacts of bleaching on reefs and raises questions over the potential for recovery. We suggest that isolated reef systems may be more susceptible to climate change, despite escaping many of the stressors impacting continental reefs.biodiversity ͉ climate change ͉ coral bleaching ͉ resilience ͉ reef fish G lobal warming is causing reef corals around the world to expel their photosynthetic symbionts, resulting in ''bleaching'' and extensive coral mortality (1-3). Widespread impacts of bleaching are predicted (4), although empirical data on the long-term effects on other components of the ecosystem are lacking. Of particular interest are reef fish, which support local fisheries and tourism (5), and are crucial for the resilience of coral reefs (6-8). Existing studies of the indirect effects of bleaching mediated coral mortality on reef fish assemblages have been short-term and indicated limited change (9-11); however, the longer-term implications of coral loss may be much more substantial (12). Long-term responses may result from changes in the physiological condition of species following coral loss (13) or through processes such as the breakdown of the physical matrix of the remaining reef structure.The global mass bleaching event of 1998 was devastating in the western Indian Ocean, where the El Niño event interacted with the Indian Ocean dipole (14), resulting in 75-99% loss of live coral (15). The Seychelles suffered particularly badly; live coral was reduced by Ͼ90% across the entire range of the inner islands (2, 16), with no apparent depth refuge. With widely accepted predictions of all reef regions of the world suffering similar large-scale degradation through bleaching in coming decades (1, 2), the study of such locations provides a unique opportunity to understand longer-term impacts on other components of the ecosystem, with implications for resilience and the persistence of vulnerable species.We surveyed coral and fish communities at 21 sites across the inner islands of the Seychelles in 1994 (17) and 2005. Over 50,000 m 2 of three distinct coral reef habitats were surveyed: fringing reefs with carbonate framework, coral growth on a granitic substrate, and patch reefs on a sand, rock, or rubble base (17). The study specifically aimed to assess changes in benthic variables after the 1998 bleaching event and relate these to changes in the ...

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Section: Resultssupporting

confidence: 73%

Dynamic fragility of oceanic coral reef ecosystems

Graham

Wilson

Jennings

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

585

497

View full text Add to dashboard Cite

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“…This includes the apparent submergence of three sandy islets previously observed at Blenheim atoll in the north [7] and island growth and fusion of six sandy islets at Egmont Atoll [1]. Regional sea surface temperature increases have reduced live coral cover through bleaching across several of the reef platforms, most notably the 1998 warming event associated with the El Nino Southern Oscillation [8]. Coral recovery has subsequently been observed and from a geomorphic perspective, this event would have resulted in short term accretion through a pulse of detrital carbonate sediment supply.…”

Section: Introductionmentioning

confidence: 99%

A Geospatial Appraisal of Ecological and Geomorphic Change on Diego Garcia Atoll, Chagos Islands (British Indian OceanTerritory)

Hamylton

East

2012

Remote Sensing

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This study compiled a wide range of modern and historic geospatial datasets to examine ecological and geomorphic change at Diego Garcia Atoll across a 38-year period . This remarkable collection of spatially referenced information offered an opportunity to advance our understanding of the nature and extent of environmental change that has taken place with the construction of the military airbase at Diego Garcia. Changes assessed included movements of the lagoon rim shorelines, changes in the terrestrial vegetation on the lagoon rim and amendments to the bathymetry of the lagoon basin through dredging activities. Data compiled included detailed shoreline and vegetation maps produced as part of the H.M.S. Vidal Indian Ocean Expedition (1967), three Ikonos satellite images acquired in 2005 that collectively covered the complete Atoll area, a ground truthing field dataset collected in the northern section of the lagoon for the purpose of seafloor mapping (2005), observational evidence of shoreline erosion including photographs and descriptions of seawater inundations and bathymetric soundings from five independent surveys of the lagoon floor (1967, 1985, 1987, 1988 and 1997). Results indicated that much of the change along the lagoon rim is associated with the expansion of the inner lagoon shoreline as a result of the construction of the military airbase, with an estimated increase in land area of 3.01 km 2 in this portion of the atoll rim. the lagoon, particularly in the vicinity of the Main Passage. As no previous record of benthic character exists, a complete benthic habitat map of the atoll was derived through classification of the three IKONOS satellite images. Management implications arising from this overall appraisal of geomorphic and ecological change at Diego Garcia included the need for ongoing monitoring of shoreline change at a representative set of sites around the atoll rim, monitoring of the water flow regime through the northern channels between the open ocean and the lagoon basin and an ongoing mapping campaign to record periodic changes in the character of the benthic surface ecology.

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“…Lasagna et al (2008) observed that the abundance of bare rock, sand and rubble derived from dead coral breakage was the result of the loss of 3D structure in Maldivian coral reefs and that this substrate smoothing is known to represent an im pediment to coral recruitment (Loch et al 2002). This loose material can limit coral recruitment (Lasagna et al 2009), as coral larvae preferentially settle on encrusting calcareous algae (Heyward and Negri 1999) and frequently avoid rubble as a settlement substratum (Sheppard et al 2002). The loss of complex physical structure can result in local extinctions, substantial reduction in species richness and reduced taxonomic distinctness associated with di verse productive coral reefs (Graham et al 2006).…”

Section: Discussionmentioning

confidence: 99%