CHARACTERIZATION AND ASSESSMENT OF THE ECOLOGICAL STATUS OF PRIORITY COASTAL MARINE HABITATS: INFLUENCE OF ANTHROPOGENIC PRESSURES AND CHANGE OVER TIME

Coastal marine ecosystems are increasingly exposed to the combined effects of local anthropogenic pressures and global environmental change, making their characterization and ecological assessment particularly challenging. Understanding ecosystem condition requires not only reliable indicators of present-day status, but also a temporal perspective capable of revealing whether observed patterns reflect stability, deterioration, recovery or natural variability. This thesis investigates the ecological status and temporal trajectories of priority Mediterranean coastal marine habitats under contrasting levels and types of anthropogenic pressure. The work integrates habitat characterization, ecological indicators, spatial information and historical datasets, with particular emphasis on the value of combining current assessments with long-term monitoring. The highly urbanized coastline of Genoa represented the main case study for evaluating the condition of Posidonia oceanica meadows, infralittoral rocky reefs and coralligenous assemblages in an area strongly affected by coastal development and currently undergoing major infrastructural transformation. The assessment of these habitats through multiple ecological indices and descriptors, also within the framework of the Marine Strategy Framework Directive, highlighted marked differences in their ecological responses and demonstrated that environmental condition cannot be adequately represented by a single indicator or monitoring scale. The development of the multimetric Marine Litter Index (MariLIn) further contributed to this methodological framework by providing a synthetic tool for evaluating seafloor litter pressure while retaining information on its main components. Comparisons with historical datasets from both urbanized and predominantly natural coastal areas showed that benthic habitats follow complex, spatially heterogeneous and often non-linear trajectories. Protected areas were also found to undergo substantial ecological change, confirming that protection from local pressures does not imply temporal stability and that regional and global drivers may continue to reshape marine communities. Overall, the results demonstrate that ecological status should not be interpreted as a static property of marine ecosystems. Synthetic indices are valuable tools for standardized environmental assessment, but their interpretation should be supported by the analysis of underlying ecological descriptors, spatial context and historical information. Integrating ecological status assessment with long-term monitoring therefore provides a more robust framework for distinguishing persistent changes from short-term variability, interpreting the effects of multiple anthropogenic pressures and supporting adaptive management, impact assessment and the long-term conservation of Mediterranean coastal habitats.