The variability of benthic invertebrate communities in streams is guided by stressors, biotic interactions and dispersal from nearby sites; these drivers interact in a complex way. This project aims at disentangling the role of the individual drivers by analysing temporal (i.e. time series) and spatial variability (near-natural, restored and differently degraded sites) of benthic invertebrate communities in two Long-Term Ecological research (LTER) sites: the Emscher/Boye catchment and the Kinzig catchment. We hypothesise that the interplay of stressors, biotic interactions and dispersal in forming benthic invertebrate communities varies predictably in space and time, depending on the maturity of the stream and the acting stressor: While in near-natural streams community composition will be mainly due to biotic interactions (here focussing on competition) and stressors, stressors will be the main drivers of community composition in degraded streams. During recovery, dispersal will be the main driver of community composition in an initial phase, while stressors and biotic interactions will gain control with increasing time since restoration.

The project will be based on the analyses of time series of up to 20 years in both catchments, which will be continued throughout the project’s lifespan. We will analyse time series on a community metric level to identify short-term changes (≤ 1 year, triggered by extreme events) and long-term trends (up to 20 years) and will link these to abiotic variables using statistical models. We will generate ecological profiles for all benthic invertebrate species that have been found in the Kinzig and Emscher/Boye catchments covering habitat preferences / stressor tolerance, biotic interactions (i.e. competitors) and dispersal abilities. We will compare the environmental profiles of the sites with ecological profiles of the species to identify the niches that have already been occupied in the process of recovery (Emscher/Boye) or following fluctuations in environmental variables and along land use gradients (Emscher/Boye, Kinzig). Results of the time series analysis and the matching of sites’ and species’ profiles will be synthesised into an overall appraisal of the contribution of stressors, biotic interactions and dispersal to community variability in near-natural, degraded and restored sites.

Svenja Gillmann (University of Duisburg-Essen)

Temporal and spatial effects of stressors, biotic interactions and dispersal on riverine benthic invertebrate community variability

Changes in biological communities are mainly driven by stressors (natural and human-induced), biotic interactions and dispersal capacities of the different species. While each of these drivers has been investigated individually, they have never been addressed in concert. To disentangle the role of the three drivers for community variability, this project is focusing on the riverine benthic invertebrates that occur in the Emscher/Boye and Kinzig catchment. During this study it will be investigated how the role of the drivers changes within and between benthic invertebrate communities at near-natural, degraded and restored sites.

Therefore, extensive ecological profiles for all species occurring in the Kinzig and Emscher/Boye catchment will be created, which include niche profiles, comprising habitat preferences and stressor tolerances. By comparing the niche preferences of the different species, biotic interaction profiles will be developed, describing possible biotic interactions such as competition between species. Lastly, the dispersal capacity of the different species will be included in the ecological profiles. Environmental site profiles for each combination of study site and year will be created for both catchments. These will include the respective habitat availability, water quality parameters, time since restoration (if applicable) and distance to recolonization sources. Then, the ecological profiles will be matched to the environmental profiles to identify the niches that have already been occupied in the process of recovery or following fluctuations in environmental variables and along landuse gradients. The resulting data will be used to assess the role of the drivers of community variability in near-natural, differently degraded and restored stream reaches.

Contact: svenja.gillmann@uni-due.de

First Supervisor: Prof. Dr. Daniel Hering (University of Duisburg-Essen, Aquatic Ecology)
Second Supervisor: Prof. Dr. Peter Haase (University Duisburg-Essen, Senckenberg Forschungsinstitut und Naturmuseum)
Mentor: Dr. Mario Sommerhäuser (Emschergenossenschaft und Lippeverband)