| Resum: |
Mediterranean rivers are highly vulnerable to anthropogenic pressures and hydrological variability, making them priority systems for ecological monitoring. The Besòs River Basin, situated within the densely urbanized Barcelona Metropolitan Region, is heavily impacted by human activities. This study assessed faunal richness and environmental quality across the basin using six years of data (2019-2024) recorded by the Observatori RIVUS, from eleven monitoring stations. Species richness was quantified for total, protected, and invasive alien species, while ecological status was evaluated through physicochemical, hydromorphological, and biological indicators. Multivariate analyses revealed clear longitudinal gradients in biodiversity and environmental quality. Stations located in the upper and upper-middle sections supported higher species richness and better ecological status, whereas the ones located in the middle and lower sections showed eutrophication, organic pollution, elevated conductivity, and a higher presence of invasive species. While avifauna dominated all stations, the other groups of fauna also highlighted key ecological gradients. The headwater station B0_LB0 emerged as a reference site, showing the highest ecological quality and distinct faunal composition, while B7_LB19 exhibited the lowest ecological condition, followed by stations located in the mid-lower and lower sections, including B8, B9, and B10_LB22. These findings demonstrated that long-term, integrative ecological monitoring provides a consistent framework for assessing the status of the river basins in the Mediterranean region. The study highlights the good condition of the well-preserved headwaters, the need to prioritize conservation efforts in the middle and lower reaches, and the importance of urban basins as a key focus for restoration initiatives. |
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