CHANGES IN THE ECOLOGICAL STATUS AND NATURAL CAPITAL OF POSIDONIA OCEANICA MEADOWS DUE TO HUMAN PRESSURE AND EXTREME EVENTS

Littorals represent highly dynamic and complex systems which undergo changes imposed by several environmental factors and human-induced disturbances. Among coastal ecosystems, seagrass meadows represent a key habitat and, according to the European Water Framework Directive, the endemic Mediterranean Posidonia oceanica is considered as biological indicators thanks to their susceptibility to pressures and changes. In this work, four P. oceanica meadows in the Portofino Marine Protected Area (NW Mediterranean) are investigated to evaluate the potential effects of different disturbances (i.e., anchoring and a severe sea storm) on them through the study of their conservation status (measured with the Conservation Index, CI) and their natural capital (NC). Results obtained for CI and NC are not always consistent: meadows with high conservation status often showed low NC values. A link between the ability of ecosystems to store NC and develop a complex functioning and the meadows conservation is evident only when ecosystems are subjected to strong disturbances like the sea storm that hit the Ligurian coast on October 2018. The two indices should thus be integrated in monitoring activities because they account for different and complementary aspects of the meadow status.