Abstract：
Hydraulic mixing of stratified reservoirs homogenizes physicochemical gradients and microbial communities. This has potential repercussions for microbial metabolism and water quality, not least in dams and hydraulically controlled waters. A better understanding of how key taxa respond to mixing of such stratified water bodies is needed to understand and predict the impact of hydraulic operations on microbial communities and nutrient dynamics in reservoirs. We studied taxa transitions between cyanobacteria and sulfur-transforming bacteria following mixing of stratified water columns in bioreactors and complemented the experimental approach with a biogeochemical model. Model predictions were consistent with experimental observations, suggesting that stable stratification of DO is restored within 24 h after episodic and complete mixing, at least in the absence of other more continuous disturbances. Subsequently, the concentration of S2- gradually return to pre-mixing states, with higher concentration at the surface and lower in the bottom waters, while the opposite pattern was seen for SO42-. The total abundance of sulfate-reducing bacteria and phototrophic sulfur bacteria increased markedly after 24h of mixing. The model further predicted that the rapid re-oxygenation of the entire water column by aeration will effectively suppress the water stratification and the growth of sulfur-transforming bacteria. Based on these results, we suggest that a reduction of thermocline depth by optimal flow regulation in reservoirs may also depress sulfur transforming bacteria and thereby constrain sulfur transformation processes and pollutant accumulation. The simulation of microbial nutrient transformation processes in vertically stratified waters can provide new insights about effective environmental management measures for reservoirs.
摘要：
分层储层的水力混合使物理化学梯度和微生物群落均匀化。这对微生物代谢和水质有潜在的影响，尤其是在水坝和水力控制水域。需要更好地了解关键分类单元如何响应此类分层水体的混合，以了解和预测水力操作对水库中微生物群落和养分动态的影响。我们研究了生物反应器中分层水柱混合后蓝细菌和硫转化细菌之间的分类群转变，并用生物地球化学模型补充了实验方法。模型预测与实验观察一致，表明DO的稳定分层在间歇和完全混合后24小时内恢复，至少在没有其他更多连续干扰的情况下。随后，S2的浓度逐渐恢复到预混合状态，表面浓度较高，底部水域浓度较低，而SO42-则相反。混合24h后，硫酸盐还原细菌和光养硫细菌的总丰度显着增加。该模型进一步预测，通过曝气对整个水柱进行快速复氧将有效抑制水分层和硫转化菌的生长。基于这些结果,我们认为，通过优化储层中的流量调节来降低温跃层深度也可能会抑制硫转化细菌，从而限制硫转化过程和污染物的积累。模拟垂直分层水域微生物养分转化过程可以为水库有效的环境管理措施提供新的见解。
