National study proposes functional indicator to strengthen river health assessment in Portugal
A study coordinated by Verónica Ferreira, researcher at the University of Coimbra and member of MARE — Marine and Environmental Sciences Centre and ARNET - Aquatic Research Network, shows that official river health assessments in Portugal can be significantly improved by incorporating indicators of ecological functioning. The team proposes the use of organic matter decomposition as a complementary tool to the structural indicators currently applied.
Published in Freshwater Biology, the study involved 23 researchers from MARE and ARNET, representing five regional research units from MARE associated with the University of Coimbra, University of Évora, ISPA – University Institute, ARDITI – Madeira and the Faculty of Sciences of the University of Lisbon. This broad collaboration highlights the scientific cohesion and collaborative capacity of the MARE network, bringing together teams from across the country to advance understanding of how Portuguese rivers function under reference conditions.s.
The researchers measured the decomposition of leaf litter and wood in 37 least‑disturbed streams across mainland Portugal and Madeira, complemented by a review of 61 previous studies from Portugal and the Azores. The results reveal substantial natural variability in decomposition rates, influenced by factors such as organic matter type, the presence of shredding macroinvertebrates, water temperature, hydrological regime, season and water chemistry.
According to Verónica Ferreira, “understanding this natural variability is essential to detect deviations that may indicate disturbance, often before changes become visible in aquatic communities”.
The study recommends standardising decomposition measurement methods, including organic matter type, invertebrate access and incubation season. Such standardisation will support the definition of reference ranges and facilitate the integration of decomposition as a functional indicator within monitoring programmes, strengthening the implementation of the EU Water Framework Directive.
The authors emphasise that incorporating functional indicators can enhance early detection of ecological change, support management decisions and contribute to a more complete and realistic assessment of Portuguese river ecosystems.
Text by Zara Teixeira
Image 1: Leaf‑litter bags and wood strips. João Canning-Clode e Patrício Ramalhosa
Image 2: Leaf litter after 28 days in a stream. Sónia Serra e Raquel Calapez
Image 3: Field work. Mafalda Gama