Projet Life Intégré Marha. Suivis des habitats de récifs intertidaux des Fucales et champs de Blocs. Bilan d’activités de l’Ifremer pour le volet côtier

This document constitutes the final report of the Life Marha project dedicated to intertidal reefs. The carried out study focus on two habitats: (i) Mediolittoral boulder fields, that revealed significant changes in benthic communities from 2020 onward. Several indicator species declined or disappeared, while southern species proliferated. These shifts, particularly in the upper mediolittoral zone, appear linked to rising temperatures and conditions favoring algal blooms, suggesting a transition toward a new ecological state. (ii) Intertidal fucoid algae, monitored using Pléiades imagery at two morphologically contrasting sites. The semi-automated processing chains implemented enable reliable mapping suitable for large-scale, spatio-temporal monitoring of brown algal populations in intetidal area. The simple and robust methodology ensures reproducible spatio-temporal analyses across multiple sites.