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Gewählte Master / Diploma Thesis:

Lisa-Marie Ziegler (2021): Effects of desiccation on heterotrophic microbial activity in hyporheic sediments.
Master / Diploma Thesis - Institut für Hydrobiologie und Gewässermanagement (IHG), BOKU-Universität für Bodenkultur, pp 67. UB BOKU obvsg FullText

Data Source: ZID Abstracts
Abstract:
Climate change, as well as water abstractions, have altered the flow regime and led to a reduction of the summer flows in running water systems. These environmental conditions promote flow intermittency and cause many formerly perennial streams to become intermittent. Shortened flow periods and water deficits affect heterotrophic microorganisms living in the sediments. Currently, there is little knowledge about the effects of stream intermittency, especially in temperate climate regions. This study investigates the immediate (during the non-flow period) and long-term (during the flow period) effects of flow intermittency on the activity of microbial communities in temperate streams in Burgenland and Styria, Austria. Hyporheic sediments from both perennial and intermittent streams were sampled during different flow conditions. Extracellular enzymatic activities and microbial respiration were used to determine stress responses to desiccation in heterotrophic organisms. Results show no significant immediate or long-term decline in heterotrophic microbial activities in hyporheic sediments of intermittent streams. During the late non-flow period, intermittent streams showed a significantly higher microbial respiration (0.58 μgC/g/h) and phosphatase activity (214.49 nmol/g/h) than perennial streams (0.43 μgC/g/h and 138.35 nmol/g/h respectively). During the flow period, average microbial respiration and enzymatic activities did not differ significantly. The maintenance of the heterotrophic activity is explained by preserving relatively high moisture content, of around 12%, during the non-flow period in the hyporheic zone. Streambed characteristics such as a high organic matter content and fine sediments favour sufficient wet conditions in sediments. This study highlights the importance of the hyporheic zone as a humid refuge habitat for microbes during the non-flowing period, increasing the resilience against drought events.

Beurteilende*r: Weigelhofer Gabriele
1.Mitwirkender: Hein Thomas

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