"MARS will support managers and policy makers in the practical implementation of the WFD, of related legislation and of the Blueprint to Safeguard Europe’s Water Resources by conducting new research and synthesising existing knowledge concerning effects and management of multiple stressors in surface water and groundwater bodies; by advising the 3rd RMBP cycle and the revision of the WFD; and by developing new integrated tools for diagnosing and predicting multiple stressors in water resource management.The consortium includes 19 research institutes and five water boards and environment agencies. MARS will engage with ongoing and finalised European initiatives addressing related topics, thus acting as an integrating project. Work will be organised at the scales of water bodies, river basins and Europe; at each scale there is a direct link to water managers and decision makers. Nested within the scale structure, we will employ a suite of methods: flume and mesocosm experiments to better understand the effects of selected stressor combinations with a focus on extremes and hydrological stress; linkage of “abiotic” and “biotic” models to predict effects of stressor combinations at a river basin scale; large-scale data analysis employing existing databases, but including additional variables, to gain a Europe-wide overview of stress, status and ecosystem services.MARS will be composed of eight workpackages (WPs). While WP1 will be responsible for overall coordination, WP2 will provide tools, concepts and scenarios for the other WPs. WPs 3-5 will analyse and predict multiple stressor-impact relationships on three scales: water bodies (WP3), river basins (WP4) and Europe (WP5); the results will be synthesised across scales by WP6. WP7 will generate a wiki information system and produce or improve tools addressing the three scales. WP8 will communicate with river basin districts and Common Implementation Strategy (CIS) groups and will advise the WFD revision."