Oral Presentation Society for Freshwater Science 2025 Annual Meeting

Are European urban streams healthy? What do diatoms say (118408)

Salomé FP Almeida 1 , António Chen 1 , Rafael Schmitt 1 2 , Ana R Calapez 2 , Marcos Dias 2 , Dirk S Schmeller 3 , Rayan Bouchali 3 , Nadia Piscopo 4 , Luigi Esposito 4 , Marie AE Forio 5 , Peter Goethals 5 , Anne Moen 6 , Silje H Henni 6 , May Linn Bokma Mørch 6 , Maria João Feio 2
  1. University of Aveiro, Campus de Santiago, Biology Department and GeoBioTec Research Centre, 3810-193, Aveiro, Portugal
  2. University of Coimbra, MARE/ARNET, Department of Life Sciences/FCTUC, 3004-517, Coimbra, Portugal
  3. Université de Toulouse, Centre de Recherche sur la Biodiversité et l´Environnement (CRBE), CNRS, IRD, Toulouse INP, Université Toulouse 3 - Paul Sabatier (UT3), 31062, Toulouse, France
  4. University of Naples Federico II, Department of Veterinary Medicine and Animal Production, 80137 , Naples, Italy
  5. Ghent University, Aquatic Ecology Research Unit, 9000 , Ghent, Belgium
  6. University of Oslo, Institute of Health and Society, Department of Public Health Science, 0318 , Oslo, Norway

The world population living in cities is growing thus increasing degradation of ecosystems. Urban streams and rivers are highly impacted suffering from physical, chemical, and morphological alterations, promoting biological and ecological imbalances. Because degraded streams will also have an impact on human well-being, environmental sustainability must be promoted. Cities from Europe were studied (Coimbra - Portugal, Benevento - Italy, Toulouse - France, Ghent – Belgium, and Oslo - Norway) covering a climatic gradient and different environmental and social-cultural conditions. In each city, 18 stream sites spanning an urbanization gradient were selected using the categorical variables scored from 1 (best condition) to 5 (most degraded): urbanization, stream connectivity, riparian zone, morphological condition and water pollution. As the dominant primary producers in streams, and widely recognized bioindicators, diatoms (unicellular or colonial algae) were used to assess the ecological quality of 92 stream sites.  Diatom communities were significantly different among the five cities (Permanova: Pseudo-F=6.56, p=0.001). Several taxa (Navicula lanceolata, Navicula gregaria, Meridion circulare, Reimeria uniseriata, Hannea arcus) were more abundant in Oslo, clearly differentiating it from the other cities (CAP ordination with 92% correctly classified sites). According to the pre-classification based on field inspection this segregation was partially explained by geographic location (higher latitude) and lower water pollution in Oslo. The other four cities were arranged along a latitudinal gradient from Ghent, to Toulouse, followed by Coimbra and finally Benevento. The biological quality based on diatoms (Indice de Poluossensibilité Spécifique - IPS) revealed a degradation gradient in each city that wasn’t significantly different between cities. All sites of the five cities were affected by urbanization, but further analysis is necessary to determine the most influential environmental factors, in order to effectively guide recovery measures.