RAPID: Effects of Enhanced Circulation on Vertical Mixing and Algal Blooms In Freshwater Reservoirs

1545624 ObenourJordan湖和世界上许多类似的水库一样，由于藻类过度生长而受损，有害藻华越来越普遍。该湖为30万人提供饮用水，并成为更多人的娱乐景点。有人提议利用强化循环作为抑制淡水和沿海水体中有害藻华形成的一种手段。这项研究代表了一个难得的机会，直接调查如何大规模的增强循环影响混合和藻类动力学（即生长）在一个大的水体。目前，人工混合及其对浮游植物群落结构的影响的表征已限于全湖混合（即分层），这可能是不切实际的较大水体。拟议的研究代表了增强的表层环流如何影响垂直扩散速率和有害赤潮形成潜力的第一个全面表征。该项目利用了独特的大型表层循环器部署，在多个尺度上回答科学和工程问题。总的来说，该项目将有助于深入了解地球工程作为减少有害藻华工具的潜在作用。在这个研究项目中，主要研究人员将进行一系列的实地活动，以确定这些循环器如何影响湖泊内的物理和生物条件。活动将在湖的不同臂中进行，代表处理（存在循环器）和对照（不存在循环器）条件。物理测量将包括用于推断垂直扩散率的温度微结构垂直剖面、用于确定环流范围的近地表流速和风速。生物测量将包括叶绿素（总藻类）和藻蓝蛋白（表示蓝绿色，蓝藻）的垂直分布。监测工作将与北卡罗来纳州水资源部协调，后者将测量一系列常规水质参数，这些参数也将用于本研究。利用这些实地活动的数据，我们将确定风速和人工环流的协同影响如何影响表层内的垂直扩散，这有望成为藻类动态的主要控制因素。我们将进一步测试与混合（自然和人工）如何影响总叶绿素和蓝藻的丰度和垂直分布有关的假设。

1545624ObenourJordan Lake, like many similar reservoirs around the world, is impaired due to excessive algal growth and harmful algal blooms are becoming more prevalent. The lake provides drinking water to 300,000 people, and it serves as a recreational attraction for many more. The use of enhanced circulation has been proposed as a means of suppressing the formation of harmful algal blooms in freshwater and coastal waterbodies. This study represents a rare opportunity to directly investigate how large-scale enhanced circulation affects mixing and algal dynamics (i.e. growth) in a large waterbody.At present, characterization of artificial mixing and its effect on phytoplankton community structure has been limited to whole-lake mixing (i.e. destratification), which may be impractical for larger waterbodies. The proposed research represents the first comprehensive characterization of how enhanced surface-layer circulation affects vertical diffusion rates and HABs formation potential. The project takes advantage of a uniquely large deployment of surface-layer circulators, to answer scientific and engineering questions at multiple scales. Overall, the project will help provide critical insight into the potential role of geoengineering as a tool for the abatement of HABs. For this research project, the principle investigators will perform a series of field activities to determine how these circulators are affecting physical and biological conditions within the lake. Activities will be conducted in different arms of the lake, representing treatment (circulators present) and control (circulators absent) conditions. Physical measurements will include vertical profiles of temperature micro-structure to infer vertical diffusivity, near-surface current velocities to determine extent of circulation, and wind velocities. Biological measurements will include vertical profiles of chlorophyll (total algae) and phycocyanin (indicating blue-green, cyanobacteria algae). Monitoring will be coordinated with the North Carolina Department of Water Resources, who will be measuring a series of conventional water quality parameters that will also be used in this study. Using the data from these field activities, we will determine how the synergistic impacts of wind speed and artificial circulation affect vertical diffusion within the surface layer, which is expected to be a primary control on algal dynamics. We will further test hypotheses related to how mixing (natural and artificial) affects the abundance and vertical distribution of total chlorophyll and cyanobacteria.