Éditeur(s) : HAL CCSD Springer Verlag (Germany)
Résumé : International audience
Mass bleaching events resulting in coral mortality are among the greatest threats to coral reefs, and are projected to increase in frequency and intensity with global warming. Achieving a better understanding of the consistency of the response of coral assemblages to thermal stress, both spatially and temporally, is essential to determine which reefs are more able to tolerate climate change. We compared variations in spatial and taxonomic patterns between two bleaching events at the scale of an island (Moorea Island, French Polynesia). Despite similar thermal stress and light conditions, bleaching intensity was significantly lower in 2007 (approximately 37 % of colonies showed signs of bleaching) than in 2002, when 55 % of the colonies bleached. Variations in the spatial patterns of bleaching intensity were consistent between the two events. Among nine sampling stations at three locations and three depths, the stations at which the bleaching response was lowest in 2002 were those that showed the lowest levels of bleaching in 2007. The taxonomic patterns of susceptibility to bleaching were also consistent between the two events. These findings have important implications for conservation because they indicate that corals are capable of acclimatization and/or adaptation and that, even at small spatial scales, some areas are consistently more susceptible to bleaching than others.
ISSN: 0167-6369

hal-00905944
https://hal.archives-ouvertes.fr/hal-00905944
DOI : 10.1007/s10661-012-2923-3

Éditeur(s) : HAL CCSD Cambridge University Press (CUP)
Résumé : International audience
This study provides a baseline describing natural small scale variability of Symbiodinium density in the sentinel coral Acropora globiceps during the summer, under non-bleaching conditions. Spatial scales investigated range from the colony scale (1-10 cm, i.e. among branches of the same colony) to the reef scale (1-10 km, i.e. among stations distributed over several locations and depths), at Moorea Island, French Polynesia. The coral-Symbiodinium symbiosis is a key process in scleractinian coral physiology, and Symbiodinium density provides an easy-to-measure and inexpensive biomarker of this symbiosis health. Spatial variability of three major environmental factors: light intensity, sedimentation and water motion was also assessed to evaluate their potential link with Symbiodinium density. Density of Symbiodinium did not significantly differ within colonies or among colonies within a station. However, a marked depth gradient was observed, showing increasing density with increasing depth and decreasing light intensity. These observations provide an interesting reference for forthcoming comparisons with disturbed conditions, such as bleaching events.
ISSN: 0025-3154

hal-00905942
https://hal.archives-ouvertes.fr/hal-00905942
https://hal.archives-ouvertes.fr/hal-00905942/document
https://hal.archives-ouvertes.fr/hal-00905942/file/Ladriereetal2014.pdf
DOI : 10.1017/S0025315413001252