Hydropower generation, a renewable source of electricity, has been linked to elevated methylmercury (MeHg) concentrations in impoundments and aquatic biota. This study investigates the impact of water level fluctuations (WLF) on MeHg concentrations in water, sediment, and fish. Using a set of controlled microcosm experiments emulating the drawdown/refill dynamics and subsequent sediment exposure to air experienced in reservoirs, we demonstrate that less frequent WLFs, and/or increased exposure of sediment to air, can lead to elevated MeHg concentrations in sediment, and total mercury (THg) and MeHg concentrations in water. In examining the effects of WLF frequency (two-day, weekly, and monthly), the monthly treatment displayed the highest THg and MeHg water levels, while the weekly treatment was characterized by the highest MeHg levels in the sediment. Our work supports emerging evidence that longer duration between WLF creates a larger surface area of sediment exposed to air leading to conditions conducive to higher MeHg concentrations in sediments and water. In contrast, THg, MeHg, and fatty acid trends in fish were largely inconclusive characterized by similar among-treatment effects and minimal temporal variability over the course of our experiment. This result could partly be attributed to overall low mercury levels and simple “worm-forage fish” food web in our experiment. To elucidate the broader impacts of water fluctuations on aquatic chemistry and biota, other factors (e.g., longer WLF cycles, dissolved organic matter, temperature, more complex food webs) which modulate both methylation rates and food web dynamics must be considered.

水力发电是一种可再生电力，与蓄水池和水生生物群中的甲基汞 (MeHg) 浓度升高有关。本研究调查了水位波动 (WLF) 对水、沉积物和鱼类中甲基汞浓度的影响。使用一组受控的微观实验模拟水库中经历的下降/再填充动力学和随后的沉积物暴露于空气中，我们证明较少频率的 WLF 和/或沉积物暴露于空气中的增加会导致沉积物中 MeHg 浓度升高，并且水中的总汞 (THg) 和甲基汞浓度。在检查 WLF 频率（两天、每周和每月）的影响时，每月处理显示最高的 THg 和 MeHg 水位，而每周处理的特点是沉积物中的甲基汞含量最高。我们的工作支持新出现的证据，即 WLF 之间的较长时间会产生更大的暴露在空气中的沉积物表面积，从而导致有利于沉积物和水中更高的甲基汞浓度的条件。相比之下，鱼类中的 THg、MeHg 和脂肪酸趋势在很大程度上是不确定的，其特点是在我们的实验过程中具有相似的处理间效应和最小的时间变异性。这一结果可能部分归因于我们实验中的整体低汞水平和简单的“蠕虫饲料鱼”食物网。为了阐明水波动对水生化学和生物群的更广泛影响，其他因素（例如，更长的 WLF 周期、溶解的有机物质、温度、