Abstract
This study investigates the diversity and distribution of intertidal Cystoseira sensu lato (s.l.) species across different protection zones within the "Capo Gallo-Isola delle Femmine" Marine Protected Area (MPA) in the central Mediterranean Sea. Five Cystoseira s.l. species (Cystoseira compressa, C. foeniculacea, Ericaria amentacea, E. brachycarpa and E. crinita) were observed on the intertidal rocky shores, with varied abundances across the MPA's protection zones. Ericaria amentacea was the only species found in all zones, with a much higher cover percentage in the most protected area (zone A). However, its morpho-functional traits showed an inverse trend, with the largest thalli found in the moderately protected zone B and C. The remaining Cystoseira s.l. species were only found in zones B and C probably due to their wider area and greater habitat diversity compared to zone A. The presence of two non-indigenous species, Asparagopsis taxiformis and Caulerpa cylindracea, was observed exclusively in the less protected zones B and C. Our findings highlight the complex interactions between MPA protection levels and Cystoseira s.l. species conservation, with protection having, in some respects, a positive influence on selected Cystoseira s.l. species, indicating the importance of careful consideration in MPA design and management. Furthermore, this study provides a baseline for future monitoring of Cystoseira s.l. populations in light of ongoing environmental changes in the Mediterranean Sea.