Résumé
Biodiversity is declining, and habitat degradation is now commonplace. Coral ecosystem degradation is usually characterized by coral mortality from natural and anthropogenic stressors. This decrease in coral cover causes a substantial increase in macroalgal cover which, in turn, limits the recovery of coral populations and thus modifies fish and invertebrate communities. Thus, areas experiencing perturbations often exhibit declines in adult populations, leading to a higher rate of species loss than in pristine habitats, and the persistence of species in the area becomes reliant on the rescue effects of recruitment. Yet, we do not know if the decline of marine organisms is due to increased mortality of adult reef organisms or due to a decrease in the degraded reef's recruitment potential, which could decline if 1) its properties have changed sufficiently to decrease its inherent attractiveness to planktonic larvae; 2) larval ability to locate preferred microhabitats has decreased; or 3) newly settled individuals' ability to survive to recruitment has decreased. We will test the effects of alternate reef states on the attraction, settlement, and subsequent survival of marine invertebrate and fish larvae. We will present the first results acquired in French Polynesia (ANR Project and CRISP Program). For example, a series of laboratory, in situ and biochemical experiments was conducted to test how marine larvae respond to water-borne chemical cues originating from different reef states (degraded vs un-degraded habitat). This was followed by testing if the auditory signals originating from different reef states impact the selection of reef state by fish and invertebrates larvae.