Physical and biogeochemical variability in the Gulf of La Spezia (Eastern Ligurian Sea, Italy): insights from a new high-resolution coastal observatory

Coastal marine shallow sites exhibit high biological richness and diversity while experiencing substantial fluctuations in seawater physical and chemical variables. The complexity of coastal processes and dynamics, exacerbated by the climate change effects, are making difficult to predict the fate of marine coastal systems. High-resolution observatories enable big data acquisition through continuous monitoring, improve the real-time detection of oceanic changes, especially at local scale, and provide essential data for marine system predictions and early warning capabilities for maritime activities. However, comprehensive long-term, high-resolution datasets in coastal areas are still limited. Smart Bay Santa Teresa underwater observatory, a new high-resolution system located in the Eastern Ligurian Sea, provided physical and biogeochemical data continuously from 2021 to 2024. Physical data confirmed a warming trend of 0.045 °C per year in the study area, consistent with global climate change patterns, and increased frequency and intensity of Marine Heatwaves, especially in 2022–2023. Biogeochemical data revealed an enriched carbonate environment, despite the short-term perturbations, and a shift of biogenic and thermal control of the carbonate system through seasons favoring biogenic carbonate development (i.e. mussels' reefs). Interestingly, the balance between CO2 stock and release, derived from biogenic calcification, revealed that the area as an active carbon sink, especially in winter and spring. The ecological value and biodiversity of the coastal marine ecosystems coexisting with highly anthropogenic areas make the site ideal to monitor the interacting effects of global warming, local hydrodynamics, and seasonal biogeochemical processes through integrated monitoring approaches.