Multiple stressor effects on biological quality elements in the Ebro River: Present diagnosis and predicted responses

Multiple abiotic stressors affect the ecological status of water bodies. The status of waterbodies in the Ebro catchment (NE Spain) is evaluated using the biological quality elements (BQEs) of diatoms, invertebrates and macrophytes. The multi-stressor influence on the three BQEs was evaluated using the monitoring dataset available from the catchment water authority. Nutrient concentrations, especially total phosphorus (TP), affected most of the analyzed BQEs, while changes in mean discharge, water temperature, or river morphology did not show significant influences. Linear statistical models were used to evaluate the change of water bodies' ecological status under different combinations of future socioeconomic and climate scenarios. Changes in land use, rainfall, water temperature, mean discharge, TP and nitrate concentrations were modeled according to the future scenarios. These revealed an evolution of the abiotic stressors that could lead to a general decrease in the ecosystem quality of water bodies within the Ebro catchment. This deterioration was especially evidenced on the diatoms and invertebrate biological indices, mainly because of the foreseen increase in TP concentrations. Water bodies located in the headwaters were seen as the most sensitive to future changes.

This project was funded by the European Commission under contract No. 603629 – project GLOBAQUA.We would like to thank the European Commission JRC Green modeler team Dr. Bruna Grizzetti, Dr. Faycal Bouraoui, and Alberto Aloe for providing the latestmodel version and support. Ms. Chiara Dorati has processed land use, irrigation, and climate datasets into suitable model data inputs. Errors in model application remains solely responsibility of the coauthor team. C.G-C is supported by a “Juan de la Cierva” research contract (MINECO, FJCI-2015- 25785). The authors acknowledge the support from the Economy and Knowledge Department of the CatalanGovernment through the Consolidated Research Groups (2014 SGR 291 and 2014 SGR 645). This study was based on data available from the Confederación Hidrográfica del Ebro (CHE, www.chebro.es).