The project will support all experimental and field-based projects of the CRC, by maintaining two central experimental systems, by performing the general field surveys and by centrally organising and performing amplicon, metagenomic and metatranscriptomic laboratory analyses.

A series of experiments in the AquaFlow indoor flume system will be used to test for short-term stressor increase and release effects under controlled conditions. The AquaFlow system facilitates experiments with replicated flow channels. Two preparatory experiments will test the variability of results and the effect of substrate type to set a basis for the data interpretation of the main experiments. The main experiments will last for nine days; in replicated treatments the effects of current velocity, temperature increase, salinization and the combination of both stressors on organism groups from bacteria to benthic invertebrates and their parasites will be tested. Samples of different media will be taken daily.

A second series of experiments will be performed with the ExStream outdoor experimental system that will be set up in both, the Emscher and Kinzig catchments. Stream water will be pumped directly into up to 128 circular mesocosms, where multiple stressors can be simultaneously applied in a full factorial design as well as using a gradient design, with four to eight replicates per treatment or treatment combination each. The system will first be used to explore biotic and functional responses to salinity gradients and alterated flow regime in the field. Subsequently, the effects of three stressors (temperature increase, salinization and current modification) on organism groups from bacteria to fish and their parasites and on ecosystem functions will be tested. The duration of the total experiment with recovery phase is 60 days.

Field studies will be performed in the Emscher/Boye and Kinzig catchments that are both part of the International Long-Term Ecological Research (LTER) 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. We will continue yearly benthic invertebrate sampling at sites, for which time series already exist. Additionally, 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 the CRC: bacteria, fungi, protists, invertebrates, fish and parasites of all these organisms.

The samples taken in the AquaFlow and ExStream 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 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 closely interact with Z-INF.