Diversité taxinomique et fonctionnelle des habitats benthiques dans l’espace et dans le temps : une perspective régionale et décennale
This thesis takes advantage of long-term monitoring data covering a regional scale to better apprehend the main drivers of the diversity of coastal seafloors. Through consideration of multiple spatial and temporal scales and different facets of community diversity, the main objective of this work was to provide a better predictive understanding of the responses of benthic communities to environmental changes. In particular, this thesis addressed the potential consequences of the on-going homogenisation of the seafloor and the global loss of biogenic habitats, havens of diversity made by foundation species. Through comparison of two such habitats, intertidal seagrass meadows and subtidal maerl beds, with bare sediment devoid of foundation species, this thesis has highlighted the key role of biogenic structures for long-term maintenance of the diversity and functioning of benthic communities. Indeed, these habitats mediate the dynamics and responses of benthic communities to environmental conditions, ensure a greater stability of their spatial structures at regional scale, and appeared essential for the long-term maintenance of the ecological functions benthic invertebrates are associated with. This work also highlighted that foundation species may affect benthic communities through different mechanisms, and that has implications on the structure and vulnerability of these communities. Lastly, this thesis emphasized a strong spatial and temporal stability of community richness despite important underlying changes in composition and thereby stressed the need to better characterise these compositional variations to guide conservation. These variations contributed, for instance, to an unexpectedly high taxonomic and functional richness of bare sediment at regional scale, similar to those of biogenic habitats, despite being locally depauperate. Overall, broad-scale monitoring programs are fundamental assets to bridge local empirical and theoretical ecological knowledge to the broader scales at which society manage and benefits from natural ecosystems.
Conservation REBENT Monitoring Numerical ecology Biogenic habitats β diversity Trait-based approach Community trajectory Scales Biotic homogenization