We investigated the validity of Autonomous Reef Monitoring Structures (ARMS) as monitoring tools for hard bottoms across a wide geographic and environmental range. We deployed 36 ARMS in the northeast Atlantic, northwest Mediterranean, Adriatic and Red Sea at 7-17 m depth. After 12-16 months, community composition was inferred from photographs, in six plate-faces for each ARMS. Overall, we found a highly significant effect of sea region, site (within seas), and plateface on community composition. Plate-faces thus represent distinct micro-habitats and provide pseudo-replicates, increasing statistical power. Within each sea region taken individually , there was also a highly significant effect of site and plate-face. Because strong effects were obtained despite the fusion of taxonomic categories at high taxonomic ranks (to ensure comparability among biogeo-graphic provinces), ARMS photo-analysis appears a promising monitoring tool for each sea region. We recommend keeping three ARMS per site and analyzing more numerous sites within a sea region to investigate environmental effects.

The understanding of ecosystem services is essential to support sustainable use and preservation of ecosystems. Coralligenous habitats, main contributors of the Med iterranean marine biod iversity, are yet und erstud ied in term of services provid ed. This stud y presents an original small-scale approach to investigate the services provided by coralligenous habitats of a French stud y area consisting of two marine sites (Marseille and Port-Cros sites) in order to cover two contrasted anthropogenic pressure despite the small-scale. Our results are based on the opinions of 43 experts who ranked 15 services in terms of existence and level of importance for human well-being: supporting ecological functions were consid ered the most important, then provisioning and cultural services. Regulating services were consid ered uncertain d ue to a lack of knowled ge. The small-scale approach highlighted a need for a referential frame to determine the existence of services (e.g. geographical and temporal scales, benefits and beneficiaries levels).