Extreme climatic events, such as flooding and drought, can abruptly modify the amplitude of the river level of a river, promoting new environmental conditions and impacting aquatic communities. Furthermore, an increasing frequency of extreme droughts in dammed rivers is expected because dams homogenize the flood pulse and decrease the river level. In this study, we evaluated the effects of extreme river-level oscillations on the benthic macroinvertebrate communities in a floodplain river. We analysed 47 years of river-level data and 17 years of benthic macroinvertebrate data. Our findings indicated that (1) extreme river-level oscillations promoted environmental conditions that were distinct from the regular oscillation; moreover, environmental characteristics were more heterogeneous in extreme oscillations than regular oscillations; (2) extreme oscillations were associated with a decreased richness, density, and diversity of benthic macroinvertebrates, promoting the dominance of tolerant taxa. Furthermore, in the studied river, a large hydroelectric power plant was built 19 years ago, which (3) decreased the river-level downstream, accentuating the occurrence of extreme drought, which has become more common after damming. We emphasize the importance of long-term biological monitoring considering the more frequent occurrence of extreme river-level oscillations in response to factors such as dam building and climate change.

中文翻译：

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河水振荡对河漫滩系统中大型无脊椎动物群落的影响

诸如洪水和干旱之类的极端气候事件可能会突然改变河流的河平面振幅，从而促进新的环境条件并影响水生社区。此外，由于大坝使洪水脉动均匀化并降低了河流水位，因此预计大坝河流中极端干旱的频率会增加。在这项研究中，我们评估了极端河平面振荡对洪泛河底栖大型无脊椎动物群落的影响。我们分析了47年的河平面数据和17年的底栖大型无脊椎动物数据。我们的发现表明：（1）极端的河流水位波动促进了不同于常规波动的环境条件；此外，在极端振荡中，环境特征比常规振荡更不均匀。（2）极端振荡与底栖大型无脊椎动物的丰富度，密度和多样性降低相关，从而促进了宽容类群的优势。此外，在研究过的河流中，建于19年前的大型水力发电厂（3）降低了下游河平面，加剧了极端干旱的发生，在筑坝后这种现象变得更加普遍。考虑到对大坝建设和气候变化等因素的响应，极端河流水位振荡的发生更加频繁，因此我们强调进行长期生物监测的重要性。（3）降低了下游河平面，加剧了极端干旱的发生，在筑坝后这种情况变得更加普遍。考虑到对大坝建设和气候变化等因素的响应，极端河流水位振荡的发生更加频繁，因此我们强调进行长期生物监测的重要性。（3）降低了下游河平面，加剧了极端干旱的发生，在筑坝后这种情况变得更加普遍。考虑到对大坝建设和气候变化等因素的响应，极端河流水位振荡的发生更加频繁，因此我们强调进行长期生物监测的重要性。