POSTER Session 1

Sentinel-3 OLCI retrievals of CDOM and salinity in Venice Lagoon

Monitoring and understanding coastal and inland water ecosystems is a complex task, influenced by dynamic water fluxes, biogeochemical processes, and impacts from natural phenomena, human activities, and a changing climate. The application of globally developed algorithms for the retrieval of key variables (such as chlorophyll, sediment, and dissolved organic matter) in inland waters is significantly limited by their complex optical properties and pronounced spatial and temporal variability. To address these challenges, a site-specific algorithm has been developed for estimating salinity levels in the Venice Lagoon using colored dissolved organic matter (CDOM) as a proxy. Initially, CDOM was modeled by fitting the in situ remote sensing reflectance (Rrs) band ratio Rrs(665)/Rrs(490) against lab-based CDOM values. This modeled CDOM was then used to estimate salinity based on their inverse relationship. The empirical model demonstrated an improved estimation of CDOM absorption at 412 nm, with a Mean Absolute Percentage Error (MAPE) of 39% for the independent dataset. For satellite retrievals, Sentinel-3 OLCI data were utilized after atmospheric correction using the ACOLITE, POLYMER, and C2RCC processors. A comparison of Rrs derived from these processors with field measurements indicated that ACOLITE outperformed the others. The ACOLITE-based CDOM retrievals correlated well with in situ salinity measurements from a semi-autonomous network of sensors (SAMANET). The established CDOM-salinity relationship yielded salinity estimates with a MAPE of 9.3%. The developed CDOM-salinity model enhances the understanding of lagoon dynamics, crucial to understand the impact of climate change on the Venice Lagoon and its ecosystem.

*Nagendra Jaiganesh Sankara Narayanan, University of Stirling, United Kingdom, https://orcid.org/0000-0001-7350-0602

Andrew Tyler, University of Stirling, United Kingdom

Evangelos Spyrakos, University of Stirling, United Kingdom

Dalin Jiang, University of Stirling, United Kingdom

Debora Bellafiore, Consiglio Nazionale delle Ricerche, Istituto di Scienze Marine (CNR ISMAR), Italy

Francesca De Pascalis, Consiglio Nazionale delle Ricerche, Istituto di Scienze Marine (CNR ISMAR), Italy

Michol Ghezzo, Consiglio Nazionale delle Ricerche, Istituto di Scienze Marine (CNR ISMAR), Italy

Federica Braga, Consiglio Nazionale delle Ricerche, Istituto di Scienze Marine (CNR ISMAR), Italy

Georg Umgiesser, Consiglio Nazionale delle Ricerche, Istituto di Scienze Marine (CNR ISMAR), Italy

Stefan Simis, Plymouth Marine Laboratory, United Kingdom

Adrian Stanica, GeoEcoMar, Romania

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