The project will support all experimental and field-based projects of RESIST, by building and maintaining two central experimental systems (ExStreamSIGMA and field flumes), by performing the general field surveys and by centrally organising and performing most of the genetic analyses (DNA, RNA and population genomics). A first series of experiments will be performed with the ExStreamSIGMA outdoor experimental system, for which two possible locations in the Emscher/Rotbach and Kinzig catchments have been identified. Stream water will be pumped directly into up to 64 mesocosms, where multiple stressors can be simultaneously applied in a gradient design. The system will be applied to explore biotic and functional responses across a gradient of drought duration and associated stressors (warming and surface flow cessation), thus testing the responses of organism groups (bacteria to benthic invertebrates; parasites) and of ecosystem functions. The first experiment in Phase II will be restricted to degradation, while the second experiment will include a subsequent recovery phase and associated recolonisation processes. The second experimental system will be replicated field flumes that will be built in cooperation with our partner Emschergenossenschaft/Lippeverband. Water will be diverted from a near-natural stream with a pump benign to drifting organisms into a diversion channel parallel to the stream, from which 12 experimental channels will be directed back to the Rotbach. Four channels will serve as control, four channels will be subjected to a drought of four weeks duration and four channels to a drought of eight weeks duration (with only sub-surface flow). After the stressor phase, the original flow will be re-established to allow for the investigation or recovery patterns. In each of these channel groups (control, four- and eight-week droughts) we will establish a habitat gradient from pure sand bottom to more variable habitat conditions. We will explore the effects of droughts under different hydromorphological conditions on biota from bacteria to invertebrates and on food webs, including biotic recovery. The field studies that commenced in Phase I will be continued in the Emscher/Boye and Kinzig catchments that are both part of the International Long-Term Ecological Research (ILTER) network. While the Emscher/Boye catchment represents one of the most severely stressed river ecosystems in Europe that has been subject to massive restoration efforts, the Kinzig catchment is a ‘standard riverscape’ of Central Europe that experiences several stressors at moderate intensity. Twenty sites in each catchment will be subjected to an intense sampling programme covering a range of environmental data and all organism groups addressed in RESIST: bacteria, fungi, protists, invertebrates, fish and parasites of all these organisms. In addition, the Emscher main stem that is wastewater-free since early 2022 will be sampled in four-monthly intervals. The samples taken in the experimental systems will be subjected to a central metagenomics and metatranscriptomic analysis, and samples from both experiments and the field investigations will be subject to amplicon analyses. Preparation of amplicon samples will be performed in the Genomic Core Facility of the Faculty of Biology (UDE), while sequencing of the generated libraries will be outsourced. All water samples from the field studies will be analysed centrally. The Project Z02 will also include central QA/QC components and will closely interact with INF.