A new predictive approach for assessing local human and climate change stressors on coastal marine ecosystems.

The potential impacts of climate-related factors (e.g., heatwaves, temperature spikes) and local human stressors (e.g., dredging) on vulnerable and protected habitats in the Mediterranean coastal marine environment can be comprehensively assessed using an innovative predictive approach. This method integrates results from numerical models and species-specific stressor tolerance curves and thresholds derived from dedicated laboratory experiments. Focusing on the endemic Mediterranean Posidonia oceanica and coralligenous habitats near the port of Civitavecchia on the western coast of Italy, we analyzed the potential disturbance caused by the occurrence of interacting stressors, increasing temperature and turbidity. A new composite index was developed to evaluate potential effects, considering findings from hydrodynamic and sediment transport models, as well as the temperature and turbidity tolerance of the studied habitats. Lower index values indicate a higher risk of habitat regression due to global warming or unsustainable coastal activities (in the absence of mitigation measures, such as an Early Warning System, EWS). Within the Renovate project, adopting an ecosystem approach for compensation and mitigation actions in the coastal marine environment, the new index was applied to assess the effects of dredging activities for the expansion of the port of Civitavecchia. Additionally, it was used to distinguish impacts on the same habitats caused by heatwaves affecting this coastal stretch. This index will contribute to the development of EWS and the formulation and implementation of risk assessment and management plans in coastal areas.