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. Some coastal habitats, like Posidonia oceanica meadows, are considered as biological indicators thanks to their susceptibility to pressures and changes, according to the European Water Framework Directive. In this work, several P. oceanica meadows in the Portofino Marine Protected Area (North-western Italy) are analysed to evaluate potential effects of impacts on coastal ecosystems. The aims of this study are: 1) to analyse the ecological status of P. oceanica by means of the Conservation Index (CI), able to get information about how the meadows react to disturbance events and about their potential recovery ability; 2) to quantify the Natural Capital (NC) value of P. oceanica through emergy analysis, a biophysical approach able to quantify resources directly or indirectly used up to generate or maintain an ecological system; it represents a measure of overall functioning; 3) to assess changes in NC value and ecological status due to anthropogenic impacts and extreme meteorological disturbances (e.g. anchoring and sea-storms, respectively); 4) to estimate the effects of anchoring restriction measures. Results obtained for CI and NC revealed similar trends: meadows with high ecological status showed the highest NC values alike, thus proving the existence of a link between the ability of ecosystems to store NC and develop a complex functioning and the meadows state of health. Moreover, both measures highlighted how natural or anthropogenic impacts affect conditions of the ecosystem, showing changes when the system is exposed to disturbance.