Helmholtz Centre for Environmental Research-UFZ, Brueckstrasse 3a, D-39114, Magdeburg, Germany.
Helmholtz Centre for Environmental Research-UFZ, Brueckstrasse 3a, D-39114, Magdeburg, Germany; Australian Rivers Institute, Griffith University, 170 Kessels Rd, Nathan, Queensland, 4111, Australia.
Water Res. 2019 Jan 1;148:208-218. doi: 10.1016/j.watres.2018.10.047. Epub 2018 Oct 23.
Dissolved oxygen is a key player in water quality. Stratified water bodies show distinct vertical patterns of oxygen concentration, which can originate from physical, chemical or biological processes. We observed a pronounced metalimnetic oxygen minimum in the low-nutrient Rappbode Reservoir, Germany. Contrary to the situation in the hypolimnion, measurements of lateral gradients excluded the sediment contact zone from the major sources of oxygen depletion for the metalimnetic oxygen minimum. Instead, the minimum was the result of locally enhanced oxygen consumption in the open water body. A follow-up monitoring included multiple chlorophyll a fluorescence sensors with high temporal and vertical resolution to detect and document the evolution of phytoplankton. While chlorophyll fluorescence sensors with multiple channels detected a mass development of the phycoerythrin-rich cyanobacterium Planktothrix rubescens in the metalimnion, this species was overlooked by the commonly used single-channel chlorophyll sensor. The survey indicated that the waning P. rubescens fluorescence was responsible for the oxygen minimum in the metalimnion. We hypothesize that pelagic processes, i.e., either oxygen use through decomposition of dead organic material originating from P. rubescens or P. rubescens extending its respiration beyond its photosynthetic activity, induced the metalimnetic oxygen minimum. The deeper understanding of the oxygen dynamics is mandatory for optimizing reservoir management.
溶解氧是水质的关键因素。分层水体表现出明显的垂直氧浓度模式，这可能源于物理、化学或生物过程。我们在德国低营养 Rappbode 水库中观察到明显的中间层氧最小值。与底层情况相反，侧向梯度的测量排除了沉积物接触带是中间层氧最小值耗氧的主要来源。相反，最小值是由于开阔水体中局部增强的耗氧量所致。后续监测包括多个具有高时间和垂直分辨率的叶绿素 a 荧光传感器，以检测和记录浮游植物的演化。虽然具有多个通道的叶绿素荧光传感器检测到中间层中富含藻红蛋白的蓝藻 Planktothrix rubescens 的大量发育，但这种物种被常用的单通道叶绿素传感器所忽略。调查表明，藻红蛋白丰富的 Planktothrix rubescens 荧光的衰减是中间层氧最小值的原因。我们假设浮游生物过程，即通过分解源自 Planktothrix rubescens 的死有机物质或 Planktothrix rubescens 将其呼吸作用扩展到光合作用之外来利用氧气，导致了中间层氧最小值的产生。深入了解氧气动态对于优化水库管理是必要的。
