Contribution des habitats biogéniques marins à la biodiversité côtière

This thesis investigated the influence of biogenic habitats populating the seafloor on coastal marine communities. Using complementary approaches combining a systematic literature review and metaanalyses, and modelling of large-scale community data available around Australia from the Reef Life Survey monitoring programme, its aims are three-fold: (i) an inventory biogenic habitats and their specific traits, (ii) to assess their effects on the diversity, structure, and trophic interactions of associated macro- and megafaunal communities, and (iii) to predict the impact of their loss on local and regional diversity patterns. Beyond identifying major biases in the scientific literature, this work revealed the unique contribution of each biogenic habitats to the support of species-rich communities and to ecosystem heterogeneity. It also highlights how their local co-occurrence shapes a mosaic of complementary habitats, which structures communities and helps mitigate biodiversity collapse under scenarios of decline in certain foundation species. Overall, this thesis emphasises the need to integrate biogenic habitats into global biodiversity assessments, given their fundamental importance and ecosystem-wide influence. It also paves the ways towards a standardised quantification of biogenic habitat roles and the mechanisms that underlie through how they mediate the effect of the environment and anthropic stressors on biodiversity.