The main objective of this work is to understand distribution patterns and coexistence of benthic species in marine ecosystems using a metacommunity approach. Metacommunity frameworks explicitly couple local and regional dynamics to disentangle their respective influence both on the abundance of the populations and on the global structure of the communities. They seem to be relevant to the case of the benthic fauna since benthic stages (i.e. juveniles and adults) have their own local dynamics, and since the pelagic stage (i.e. larvae) ensure dispersal at the regional scale. The design of a benthic invertebrate metacommunity model and the exploration of its properties highlighted the importance of local interactions and dispersal of larvae on the coexistence of species. Results underlined that dispersal increases local diversity while local interactions between individuals (inter- and intraspecific) are primordial to maintain populations at intermediate levels of abundance. Theoretical patterns were then compared to empirical patterns of the group of Annelid polychaetes in the Gulf of Lions (North Western Mediterranean Sea, France), using spatial data of species abundance, in order to identify the main deterministic factors leading to their observed diversity in this area. Results suggested that meso-scale hydrodynamics is a potential factor influencing the distribution of populations at local scale, creating a structured network of import and export areas. Finally, an extended data analysis was achieved for several polychaete metacommunities sampled in other regions of the Southern European Seas (Mediterranean and Black Seas). Inferences performed on the rank-abundance relationships suggest that the global distribution of polychaetes species cannot be attributed to neutral processes, but rather to niche processes where biotic interaction dynamics structure the communities. Key-words: metacommunity, ecological modelling, population dynamics, benthic invertebrates, polychaetes, larval dispersal, connectivity.

Key-words: metacommunity, ecological modelling, population dynamics, benthic invertebrates, polychaetes, larval dispersal, connectivity.