Institute of Ecology and Environment, State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resource & Hydropower, Sichuan University, Chengdu, Sichuan, China; Department of Mechanical Engineering and St. Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN, 55455, USA.
Department of Mechanical Engineering and St. Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN, 55455, USA.
Environ Pollut. 2021 Jun 1;278:116822. doi: 10.1016/j.envpol.2021.116822. Epub 2021 Feb 25.
Hydrodynamic conditions often affect the eutrophication process and play a key role in algal growth in reservoirs. A promising approach for controlling algal blooms in reservoirs is to create adverse hydrodynamic conditions by implementing reservoir operation strategies. However, research on this method is still nascent and does not support practical applications due to the lack of quantitative hydrodynamic thresholds. In this paper, field observations of algal growth from April 2015 to August 2016 were conducted, and a three-dimensional (3D) model that couples hydrodynamics and water temperatures for the Zipingpu Reservoir was established. Low flow velocities (V) and low Reynolds numbers (Re) in the Longchi tributary are favorable for dinoflagellate growth and accumulation, which can explain why dinoflagellate blooms are more likely to occur in the tributary. A temperature of 18-22 °C is considered a precondition for Peridiniopsis penardii blooms, suggesting that freshwater dinoflagellate species may prefer lower temperatures than marine dinoflagellate species. Shallow mixing layer depth (Z) is conducive to Peridiniopsis penardii gathering in the upper water layers and promotes growth. The shallow euphotic layer depth (Z) was speculated to promote the dominance of this species by stimulating its heterotrophy and inhibiting other algal autotrophy. Furthermore, a boundary line analysis was introduced to characterize the relationships between algal biomass and hydrodynamic indicators. Thus, the thresholds for V, Re, and Z/Z were determined to be 0.034 m s, 6.7 × 10, and 1.7, respectively. Either accelerating horizontal flow to exceed the thresholds of V and Re or facilitating vertical mixing to exceed the threshold of Z/Z can prevent dinoflagellate blooms. Therefore, the summarized hydrodynamic threshold system is suggested to be an effective standard for controlling dinoflagellate blooms in the reservoir. Moreover, this study can provide a useful reference for understanding the mechanism of freshwater dinoflagellate blooms.
水动力条件通常会影响富营养化过程，并在水库藻类生长中起关键作用。通过实施水库运行策略来创造不利的水动力条件是控制水库藻类水华的一种有前景的方法。然而，由于缺乏定量水动力阈值，该方法的研究仍处于起步阶段，无法支持实际应用。本文通过 2015 年 4 月至 2016 年 8 月的藻类生长实地观测，并建立了一个耦合水动力和水温的紫坪铺水库三维（3D）模型。龙池支流的低流速（V）和低雷诺数（Re）有利于甲藻的生长和积累，这可以解释为什么甲藻水华更容易在支流中发生。18-22°C 的水温被认为是柏氏菱形藻水华的前提条件，这表明淡水甲藻物种可能比海洋甲藻物种更喜欢较低的温度。浅混合层深度（Z）有利于柏氏菱形藻在上层水体中聚集，并促进其生长。浅透光层深度（Z）被推测通过刺激其异养和抑制其他藻类自养来促进该物种的优势。此外，引入了边界线分析来描述藻类生物量与水动力指标之间的关系。因此，确定 V、Re 和 Z/Z 的阈值分别为 0.034 m/s、6.7×10 和 1.7。无论是加速水平流动以超过 V 和 Re 的阈值，还是促进垂直混合以超过 Z/Z 的阈值，都可以防止甲藻水华的发生。因此，总结的水动力阈值系统被建议作为控制水库中甲藻水华的有效标准。此外，本研究可以为了解淡水甲藻水华的机制提供有用的参考。
