Long-term recovery of metabolism, enzyme activity and community abundance after drying and bedform migration in the Spree river 2018/2019

Sandy streambed sediments that had been exposed to either intense drying (90-day without rainfall) or bedform migration (periodically moving ripples) were placed in 250 µm mesh bags to the Spree River in Northeastern Germany on October 22, 2018, to initiate the recovery process from drying or migration stress. Subsamples from the recovering sediments were collected at eight dates within eight months and taken to the laboratory for further analysis. Community respiration and Net Community Production of sediment associated biofilms were measured as dissolved oxygen concentrations from sediment pore water in inundated microcosms. Potential extracellular enzyme activities (Beta-Glucosidase, Xylosidase, Chitinase, Phosphatase, Leucine-Aminopeptidase, Phenol-Oxidase, and Peroxidase) were assessed by measuring fluorescence and absorbance after extraction from sediments. Community abundance was assessed on a heterotrophic (amplified bacterial and fungal gene copies) and on an autotrophic level (Chlorophyll a concentration and diatom cell count). The aim of the experiment was to observe the long-term recovery of microbial communities in lowland streams from drying and bedform migration and to identify if stress effects persisted as legacy after the stress period.