Sea fan (red gorgonian)

Photo: clairebayon · CC BY-NC

The red gorgonian is one of the defining organisms of the Mediterranean mesophotic zone, forming dense fans at 20 to 60 m depth that can be centuries old and over 1 m across. They are filter feeders, orientating their planar fans perpendicular to current flow to maximise zooplankton capture. Mass mortality events linked to marine heat waves (notably 1999 and 2003) have affected populations across the Mediterranean, making the Calanques' wall populations — partly shielded by localised cold-water upwelling — particularly valuable.