A preliminary study toward an index based on coralligenous assemblages for the ecological status assessment of Mediterranean French coastal waters

► This method evaluated the quality of coralligenous habitat and costal waters according to WFD. ► 38 field stations were described using composition, functional and structural metrics. ► Coralligenous Assemblage index (CAI) was linked to human pressures. ► Sludge percent, bryozoa and builder species percent cover were selected for CAI design. ► CAI was positively and significantly linked to anthropization.