Institute of Hydrobiology and Aquatic Ecosystem Management, Department of Water, Atmosphere and Environment, University of Natural Resources and Life Sciences, Vienna, Gregor Mendel Straße 33, A-1180 Vienna, Austria; WasserCluster Lunz - biologische Station, Lunz am See, Dr. Carl Kupelwieser Prom. 5, A-3293 Lunz/See, Austria.
Institute of Hydrobiology and Aquatic Ecosystem Management, Department of Water, Atmosphere and Environment, University of Natural Resources and Life Sciences, Vienna, Gregor Mendel Straße 33, A-1180 Vienna, Austria; WasserCluster Lunz - biologische Station, Lunz am See, Dr. Carl Kupelwieser Prom. 5, A-3293 Lunz/See, Austria.
Sci Total Environ. 2021 May 10;768:145200. doi: 10.1016/j.scitotenv.2021.145200. Epub 2021 Jan 22.
Sudden instream releases of water from hydropower plants (hydropeaking [HP]) can cause abrupt temperature variations (thermopeaking [TP]), typically on a daily/sub-daily basis. In alpine rivers, hydropeaking and thermopeaking waves usually overlap, which leads to a multiple stressor of flow velocity pulses and temperature alteration. Periphytic communities could give important insights into the effects of combined thermo- and hydropeaking (THP) in stream ecosystems. Thus, the study's first aim was to assess the combined effects of thermo-hydropeaking on structural (composition, biomass) and functional (photosynthesis, enzyme activity) properties of periphyton. The second aim was to assess the interaction between periphytic algae and the heterotrophic communities (bacteria) and determine how biotic and abiotic factors explain the variability of bacterial enzymatic activities in the periphyton. We assessed the effects of repeated cold and warm thermo-hydropeaking for 24 days on periphyton, by manipulating discharge and temperature in six experimental flumes directly fed by an Alpine stream. Our study revealed that THP had structural and functional effects on periphyton in oligotrophic streams, where the effects depending on the direction of the temperature change (cold/warm) and on the morphological setting (pool/riffle). The results showed that even a short-term increase in flow velocity and temperature decrease could induce better growth conditions for diatoms. Additionally, an increase in the interaction between periphytic algae and bacteria during thermo-hydropeaking was also shown, this coupling being more pronounced in pool than in riffle sections. Our results clearly showed that riffle sections develop less periphytic algal biomass and activity and therefore, THP can reduce biomass availability for primary consumers in large areas of impacted streams. These findings highlight the importance of mitigation measures, focusing on establishing heterogeneous stream bed areas, with frequent pool and riffle sequences.
水力发电站的突流水释放（水击波[HP]）会导致水温的突然变化（热击波[TP]），通常是在每日/亚日的基础上。在高山河流中，水击波和热击波通常会重叠，这导致流速脉冲和温度变化的多重胁迫。周丛生物群落可以为研究流生态系统中热-水击波（THP）的综合效应提供重要的见解。因此，本研究的第一个目标是评估热-水击波对周丛生物的结构（组成、生物量）和功能（光合作用、酶活性）特性的综合影响。第二个目标是评估周丛藻类和异养群落（细菌）之间的相互作用，并确定生物和非生物因素如何解释周丛生物中细菌酶活性的变异性。我们通过在直接由高山溪流供应的六个实验水槽中操纵流量和温度，对周丛生物进行了为期 24 天的重复冷温和热-水击波处理，评估了其对周丛生物的影响。我们的研究表明，THP 对贫营养溪流中的周丛生物具有结构和功能效应，这些效应取决于温度变化的方向（冷/暖）和形态设置（池/急流）。结果表明，即使是短期增加流速和降低温度也可以为硅藻提供更好的生长条件。此外，还表明在热-水击波期间周丛藻类和细菌之间的相互作用增加，这种耦合在池区比在急流区更为明显。我们的研究结果清楚地表明，急流区的周丛生物藻生物量和活性较低，因此，THP 可以减少受影响溪流大面积内初级消费者的生物量供应。这些发现强调了缓解措施的重要性，这些措施侧重于建立具有频繁池区和急流区序列的异质河床区。
