Linking small scale hydromorphology to biofilm’s biodiversity and functioning to explain restoration success

Dams alter streams' hydromorphology, leading to habitat degradation and impacting biodiversity and ecological processes. Thus, dam removal aims to restore streams to a reference state. However, many ecological processes are mediated by biofilms, microbial communities associated with the streambed, which are influenced by physical processes occurring at spatial scales smaller than those targeted for restoration. This raises the question of whether restoration succeeds in restoring small-scale hydromorphology and if this results in a recovery of microbial diversity and functioning. Using a space-for-time substitution approach, we sampled 3 reaches of a 2^nd-order stream in Germany: a dammed reach (impacted), a reference reach, and a restored one. We quantified biofilms’ functioning (DOC and NO₃^- uptake) and diversity (16S sequencing), and we measured small-scale hydromorphology (turbulent kinetic energy (TKE) and flow velocity (FV)). TKE and FV were lower in the impacted than in the reference reach. DOC uptake was higher in the impacted than the reference reach, while NO₃^- uptake did not differ. The microbial community differed significantly. Restoration effectively improved hydromorphology; on average, TKE and FV returned to the reference’s site levels. The microbial community's composition also recovered. An increase in TKE likely contributed to the partial recovery of DOC uptake; however, DOC uptake did not reach reference levels. Our findings suggest restoring biofilm’s biodiversity and functionality may only be possible by restoring also the small-scale hydromorphology.

Presentation Preference: Oral

Primary Presenter: Julia Pasqualini, Helmholt Centre for Environmental Research-UFZ (julia.pasqualini@ufz.de)

Authors:

Julia Pasqualini, Helmholtz Centre for Environmental Research - UFZ  (julia.pasqualini@ufz.de)

Christine Anlanger, University of Kaiserslautern-Landau (RPTU), Institute for Environmental Sciences / Helmholtz Centre for Environmental Research - UFZ  (christine.anlanger@ufz.de)

Patrick Fink, University of Cologne, Institute for Zoology / Helmholtz Centre for Environmental Research - UFZ  (patrick.fink@ufz.de)

Markus Weitere, Helmholtz Centre for Environmental Research - UFZ  (markus.weitere@ufz.de)

Andreas Lorke, University of Kaiserslautern-Landau (RPTU), Institute for Environmental Sciences  (a.lorke@rptu.de)

Clara Mendoza-Lera, University of Kaiserslautern-Landau (RPTU), Institute for Environmental Sciences  (clara.mendozalera@gmail.com)

Mario Brauns, Helmholtz Centre for Environmental Research - UFZ  (mario.brauns@ufz.de)