Coastal lagoons at the global scale occupy an area equivalent to 13% of continental coastlines and play a crucial role in multiple biogeochemical processes and their productivity. In these ecosystems, management choices are often suboptimal, partly due to insufficient understanding of the role of lagoons in the social and economic well-being of the communities that depend on them. The multidisciplinary approach utilized in this study to assess the ecosystem services associated with the Orbetello Lagoon enabled the determination of the value this habitat holds concerning the functioning of anthropogenic activities adjacent to the lagoon. To this end, the ecosystem services provided by the Orbetello Lagoon were defined, described, and quantified in 3.8 Mil of euro. To ascertain the specific ecosystem services, it was necessary to quantify the Natural Capital and Natural Flows that regulate the lagoon, following a protocol for the collection and organization of existing knowledge about the area and identifying knowledge gaps. The density of the benefit flow, amounting to 50.000 €/year/m² closely depends on high cultural services and is influenced by regulating ones. Once the ecological and economic value of the Orbetello Lagoon was established, a bibliographic review was conducted to investigate the possible repercussions of major drivers related to climate change on ecosystem services.

This study investigated the combined effects of climate change-related salinity extremes and nanoparticle pollution on the seagrass Posidonia oceanica and the macroalga Caulerpa prolifera. Both species were exposed, individually and in co-occurrence, to different salinity regimes (34; 38 and 42 g kg⁻¹) and to the emerging contaminant nano-TiO₂ (0.7 mg L⁻¹, environmentally relevant concentration, and 5.0 mg L⁻¹, high-stress exposure). Biochemical and physiological responses were assessed at baseline (T0) and after 3, 6, and 12 days of exposure, followed by a 12-day recovery phase to evaluate post-stress resilience. This multifactorial design enabled the evaluation of interactive and cumulative effects of salinity shifts associated with climate change and nanoparticle contamination. Results showed that P. oceanica was particularly sensitive to nano-TiO₂ at a concentration of42 g kg⁻¹. Reduced photosynthetic performance was associated with enhanced oxidative stress and limited recovery capacity, suggesting potential long-term impacts on meadow persistence and ecosystem functioning. In contrast, C. prolifera exhibited higher tolerance and recovery efficiency, potentially gaining a competitive advantage under climate-induced environmental variability and increasing the risk of seagrass decline and community shifts in coastal ecosystems. These biochemical markers of early stress do not necessarily reflect direct population effects, particularly in long-lived foundation species such as Posidonia oceanica.