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

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.2018年10月22日，将经受强干燥（90天无降雨）或河床形态迁移（周期性移动沙纹）的沙质河床沉积物装入250微米孔径网袋，放置于德国东北部的施普雷河（Spree River）中，以启动其脱离干燥或迁移胁迫的恢复过程。在随后八个月内的八个时间节点采集恢复过程中的沉积物子样本，运送至实验室开展后续分析。通过检测淹没式微宇宙（microcosm）中沉积物孔隙水的溶解氧浓度，测定沉积物附着生物膜（biofilm）的群落呼吸与净群落生产力。针对潜在胞外酶活性（extracellular enzyme activity），包括β-葡萄糖苷酶、木糖苷酶、几丁质酶、磷酸酶、亮氨酸氨基肽酶、酚氧化酶与过氧化物酶，在从沉积物中提取酶后通过荧光与吸光度检测进行评估。群落丰度分别从异养层面（扩增细菌与真菌基因拷贝数）与自养层面（叶绿素a浓度与硅藻细胞计数）进行评估。本实验旨在观测低地溪流微生物群落在经历干燥与河床形态迁移胁迫后的长期恢复过程，并探究胁迫效应在胁迫期结束后是否会以遗留效应的形式持续存在。