Water level fluctuations (WLFs) affect phytoplankton dynamics, water quality, and fish populations in lakes and reservoirs around the world. However, such effects are system-specific and vary due to interactions with other external factors such as solar radiation, air temperature, wind, and external phosphorus loading. Utilizing data from a long-term monitoring program (1990–2016), we developed an approach using cross-tabulation contour and conditional probability analyses to detect the effects of WLFs on the frequency of poor water quality impacting native fish in a large, shallow, hypereutrophic lake. Through the incorporation of long-term inter-annual and seasonal variability in climatic factors and cyanobacterial bloom periodicity, our approach detected non-linear WLF effects whereby both high and low-lake levels were associated with higher probabilities of poor water quality conditions stressful to fish including high pH, high un-ionized ammonia, and low dissolved oxygen. Although lake level management may not prevent poor water quality in any given year due to other external factors such as temperature or wind, we determined that seasonally based intermediate lake levels bracketing the long-term median afforded the best water quality conditions for endangered fish during the summer period when poor water quality is most common.

中文翻译：

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使用长期监测数据检测水位波动对浅水富营养化湖泊中濒危鱼类水质的影响

水位波动 (WLF) 会影响世界各地湖泊和水库中的浮游植物动态、水质和鱼类种群。然而，这种影响是系统特定的，并且由于与其他外部因素（如太阳辐射、气温、风和外部磷负荷）的相互作用而有所不同。利用来自长期监测计划（1990-2016 年）的数据，我们开发了一种使用交叉表等高线和条件概率分析的方法来检测 WLF 对影响大型、浅水、超富营养化湖泊。通过结合气候因素和蓝藻水华周期性的长期年际和季节变化，我们的方法检测到非线性 WLF 效应，即高和低湖泊水位与对鱼类造成压力的不良水质条件的可能性更高，包括高 pH 值、高非离子氨和低溶解氧。尽管湖泊水位管理可能无法防止任何特定年份由于温度或风等其他外部因素导致水质不佳，但我们确定，包含长期中位数的季节性中间湖泊水位为濒危鱼类提供了最佳水质条件。夏季水质差是最常见的时期。