Increasingly, cold-water pollution (CWP) is being recognised as a significant threat to aquatic communities downstream of large, bottom-release dams. Cold water releases typically occur during summer when storage dams release unseasonably cold and anoxic hypolimnetic waters, which can decrease the temperature of downstream waters by up to 16°C. Depending on the release duration, these hypothermic conditions can persist for many months. The capacity of ectothermic species to tolerate or rapidly adjust to acute temperature changes may determine the nature and magnitude of the impact of CWP on affected species. This study assessed the impacts of an acute reduction in water temperature on the physiological function and locomotor performance of juvenile silver perch (Bidyanus bidyanus) and examined their capacity to thermally compensate for the depressive effects of low temperatures via phenotypic plasticity. Locomotor performance (Ucrit and Usprint) and energetic costs (routine and maximum metabolic rate) were measured at multiple points over a 10-week period following an abrupt 10°C drop in water temperature. We also measured the thermal sensitivity of metabolic enzymes from muscle samples taken from fish following the exposure period. Cold exposure had significant depressive effects on physiological traits, resulting in decreases in performance between 10% and 55%. Although there was partial acclimation of Ucrit (~35% increase in performance) and complete compensation of metabolic rate, this occurred late in the exposure period, meaning silver perch were unable to rapidly compensate for the depressive effects of thermal pollution. The results of this study have substantial implications for the management of cold water releases from large-scale dams and the conservation of native freshwater fish species, as this form of thermal pollution can act as a barrier to fish movement, cause reduced recruitment, ecological community shifts and disruptions to timing and success of reproduction.

中文翻译：

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冷水污染对鱼类的影响能否通过热塑性来减轻？

冷水污染 (CWP) 越来越多地被认为是对大型底泄水坝下游水生群落的重大威胁。冷水排放通常发生在夏季，当时蓄水坝会释放不合时宜的寒冷和缺氧的低浓度水，这会使下游水的温度降低多达 16°C。根据释放持续时间，这些低温条件可以持续数月。变温物种耐受或快速适应急性温度变化的能力可能决定 CWP 对受影响物种的影响的性质和程度。本研究评估了水温急剧降低对幼银鲈 (Bidyanus bidyanus) 生理功能和运动性能的影响，并检查了它们通过表型可塑性热补偿低温抑制作用的能力。在水温突然下降 10°C 后，在 10 周内多点测量运动性能（Ucrit 和 Usprint）和能量消耗（常规和最大代谢率）。我们还测量了暴露期后从鱼身上采集的肌肉样本中代谢酶的热敏感性。冷暴露对生理特征有显着的抑制作用，导致性能下降 10% 到 55%。尽管 Ucrit 部分适应（性能提高约 35%）和代谢率完全补偿，但这发生在暴露期的后期，这意味着银鲈无法快速补偿热污染的抑制作用。这项研究的结果对大型水坝的冷水排放管理和本地淡水鱼类物种的保护具有重大意义，因为这种形式的热污染可以成为鱼类运动的障碍，导致补充减少，生态群落繁殖时机和成功的变化和中断。