Abstract Suspended Particulate Matter (SPM) plays a central role in coastal marine ecosystems, influencing light availability, primary production, and transport of sediments, nutrients, and pollutants. Monitoring its variability is essential for understanding the impacts of both natural and anthropogenic pressures on coastal regions. In this study, nine years (2016–2025) of data from the Ocean and Land Colour Instrument (OLCI) aboard Sentinel‐3 were used to analyze SPM variability and trends across European and Mediterranean coastal waters at 300 m resolution. Monthly SPM composites were generated using a semi‐analytical model, and processed using time series decomposition (Census X‐11) and non‐parametric trend analysis. A continental‐scale climatology was generated, and high temporal variability was observed along the coasts, and in shelf seas such as the Irish Sea and the North Sea, where seasonal river discharge and resuspension events occur. Statistically significant trends were detected in several regions: declines in the Severn Estuary (−3.27%yea) and English Channel (−3.6%yea), and increases in the Northern North Sea (+3.51%yea), Gulf of Gabes (+6.52%yea), Abu Qir port, Egypt (+8.20%yea), and northwestern Black Sea (+4.01%yea). Case studies linked these trends to potential drivers including dredging and land reclamation (Abu Qir port), warfare‐related disturbances (Kakhovka Dam breach), and regional hydrodynamic or anthropogenic pressures. These findings are relevant to European marine policy frameworks, supporting efforts to establish robust indicators of coastal water quality. This study highlights the value of satellite observations for environmental monitoring and coastal management across European and Mediterranean waters.
Subirade et al. (Fri,) studied this question.