Spatiotemporal heterogeneity in lowland streams: A benthic macroinvertebrate perspective

In lowland streams, spatiotemporal heterogeneity of habitat structures and flow together shape the physical environment that affects biota on different scales. However, it is still unclear on which scale these key factors have the strongest effect on benthic macroinvertebrates. At the same time there is an urgent need to improve the ecological quality of lowland streams in terms of biodiversity. Therefore, this thesis aimed at identifying the relevant scales of spatiotemporal heterogeneity for benthic macroinvertebrates in lowland streams. To this purpose, species specific ranges of conditions, thresholds and requirements were studied to test the hypothesis that moderate spatial and temporal heterogeneity at the meso- and micro-scale carries the highest macroinvertebrate diversity in lowland streams and to determine the optimal conditions for characteristic running water species to improve future restoration efforts. The results presented in this thesis unraveled the key components of spatiotemporal heterogeneity in lowland streams from a benthic macroinvertebrate perspective at different scales, showing that the interactions between flow and complex habitat structures shape macroinvertebrate communities through the persistence of macroinvertebrates and their habitat on a microhabitat scale. In lowland streams moderate dynamic flow, the presence of complex habitat structures and a mixture of more and less durable habitat patches are key to providing benthic macroinvertebrates with resources, oxygen, food and shelter. The interplay of these key components results in a continuously evolving spatially heterogeneous environment suitable for a wide array of species. This way, complex habitat structures enable highly biodiverse and resilient macroinvertebrate assemblages, despite dynamic discharge patterns.