Critères d’évaluation de la dégradation des communautés coralliennes dans la région caraïbe

Abstract

Almost all the coral reefs of the Caribbean region present important signs of alteration. In the French Antilles, about 80 % of the coral communities are more or less damaged. A study has been undertaken in order to describe and understand the dynamics of this recent evolution. The aim of this study was also to detect the ecological descriptors able to characterize the state of health of coral communities by remote sensing. The species richness of coral communities, the most simple indicator of the biodiversity of the studied area, as well as diversity indices, revealed to be descriptors particularly stable and very little reactive to the degradation of the reef community. The coverage rate of the bottom by corals may be very different from one reef to another one or from one area to another one on the same reef. This does not necessarily imply the existence of a difference in the state of health between the communities. The most relevant criteria revealed to be associated with the state of health of coral colonies and the abundance of juvenile recruits. For the other components of the reef benthic community, the most pertinent descriptor was the ratio of the bottom covered with algal turf (healthy reefs) to that occupied by macro-algae (damaged reefs). These ecological descriptors revealed to be easy to estimate in a reproducible manner by observers who are not specialists of reef ecology. This extends the possibilities of monitoring the health of coral reefs through the assistance of non-scientific personnel (staff of the marine reserves, volunteers, etc.).

Detecting the effects of natural disturbances on coral assemblages in French Polynesia: A decade survey at multiple scales

“…Despite the fact that corals are the key component of the reef ecosystem, measuring the effects of disturbances on other target reef communities may offer complementary information to assess changes in coral reef community structure, especially of the cascading effects that follow a major disturbance. For example, surveys of temporal trends of the coral/macroalgae or coral/clionid cover Schönberg and Wilkinson 2001;Bouchon et al 2004), bioeroder organisms (Holmes 1997), or disease incidence and virulence of some marine invertebrates (Harvell et al 1999), may provide complementary indication of reef health. Mortality rates and changes in benthic and fish assemblages following natural disturbances may also be indicative of the intensity of the impacts (Kaufman 1983;Williams 1986;Chabanet et al 1995;Lewis 1998;Lindahl et al 2001).…”