Marjal dels Moros: a model site for the structural, functional, and socioeconomic assessment of managed Mediterranean marshes

Coastal wetlands deliver critical ecosystem services but remain highly degraded by anthropogenic and climatic pressures. This study presents an integrated structural, functional, and socio-economic assessment of Marjal dels Moros, a managed Mediterranean brackish marsh in eastern Spain, to evaluate restoration effectiveness and inform climate-based management. Six subsites representing well-preserved, altered, and restored conditions were analyzed for water and sediment properties, microbial community composition, and greenhouse gas (GHG) fluxes, alongside a multi-criteria socio-economic evaluation of restoration scenarios. Results revealed strong environmental heterogeneity mostly driven by the hydroperiod and salinity gradients, with restored sites exhibiting intermediate sediment characteristics and reduced proxies of pathogenic bacterial genera. Microbial ordination highlighted hydrological control of methane-cycling guilds, while GHG fluxes showed a clear functional gradient: as such, permanently inundated, nutrient-rich sites emitted high CO₂ and CH₄ fluxes whereas subsites with seasonal drying and higher salinity acted as near-neutral or CH₄-suppressing zones. These patterns confirm that hydroperiod and salinity management shape microbial guilds and carbon dynamics, directly influencing climate regulation services. Socio-economic analysis indicated stakeholder preference for measures enhancing natural hydrology, habitat diversity, and risk reduction, supporting restoration strategies. Findings underscore hydrology-first strategies, integrated monitoring of functional indicators, and inclusive governance as key to achieving ecological integrity, climate mitigation, and socio-economic co-benefits. The proposed framework offers transferable guidance for policy-relevant restoration of Mediterranean coastal wetlands under multi-use pressures.