In Italy, the “Environmental Accounting in Italian Marine Protected Areas” (EAMPA) research program assessed the natural capital within Marine Protected Areas (MPAs). The program did not include the midlittoral rocky habitats, where several brown algae of the complex Cystoseira sensu lato thrive, representing ecosystem engineers. Among these, Ericaria amentacea is a sensitive species undergoing decline across the Mediterranean. In this study, the value of E. amentacea stands was assessed in two MPAs (Portofino MPA-PFN and Ciclopi Islands MPA-CIC) during two phenological stages: (quiescent and vegetative). Results showed no significant differences between MPAs, while temporal differences were significant. Indeed, integrating the separate contributions of the perennial cauloid and deciduous fronds allowed a more refined assessment of the effective value of E. amentacea canopies and an estimate of their flows. During the vegetative phase, when branch grow (flows), the value concentrates in the canopy (PFN: quiescent phase 1.64E+12 sej/m2, vegetative phase 6.21E+12 sej/m2; CIC: quiescent phase 1.28E+12 sej/m2, vegetative phase 2.96E+12 sej/m2). These findings highlight the role of this habitat as a biodiversity hotspot.
