Whole-Ecosystem Experiments Reveal Varying Responses of Phytoplankton Functional Groups to Epilimnetic Mixing in a Eutrophic Reservoir
Whole-Ecosystem Experiments Reveal Varying Responses of Phytoplankton Functional Groups to Epilimnetic Mixing in a Eutrophic Reservoir
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DOI：
10.3390/w11020222
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发表时间：
2019-01
期刊：
影响因子：
3.4
通讯作者：
M. Lofton;R. McClure;Shengyang Chen;John C. Little;C. Carey
中科院分区：
文献类型：
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作者：
M. Lofton;R. McClure;Shengyang Chen;John C. Little;C. Carey
水柱混合会影响湖泊和水库中上层浮游植物的群落组成。先前的研究表明，低度混合有利于蓝细菌，而增加混合有利于绿藻和硅藻。然而，当在整个生态系统规模上激活表生混合器时，群落优势的这种转变并不能始终如一地实现，这可能是因为浮游植物群落的反应是通过对其他生态系统过程的混合效应来介导的。我们使用气泡羽流扩散器系统在小型饮用水水库中进行了两次表层混合实验。我们测量了混合之前、期间和之后的物理、化学和生物变量，并将结果与未混合的参考储层进行比较。我们观察到蓝细菌（从 0.8 ± 0.2 到 2.4 ± 1.1 μg L−1，p = 0.008）、隐植物（从 0.7 ± 0.1 到 1.9 ± 0.6 μg L−1，p = 0.003）和绿藻（从 3.8 到 4.4 μg L−1，p = 0.003）的生物量显着增加。 0.15）在我们的第一次混合事件之后，可能是由于上游沉积物夹带的总磷增加。第二次混合事件后，浮游植物生物量没有变化，但浮游植物群落组成从丝状形态的类群转变为更小、更圆的类群。我们的结果表明，在预测浮游植物群落对表湖混合的反应时，应考虑整个生态系统动力学和浮游植物形态特征。
Water column mixing can influence community composition of pelagic phytoplankton in lakes and reservoirs. Previous studies suggest that low mixing favors cyanobacteria, while increased mixing favors green algae and diatoms. However, this shift in community dominance is not consistently achieved when epilimnetic mixers are activated at the whole-ecosystem scale, possibly because phytoplankton community responses are mediated by mixing effects on other ecosystem processes. We conducted two epilimnetic mixing experiments in a small drinking water reservoir using a bubble-plume diffuser system. We measured physical, chemical, and biological variables before, during, and after mixing and compared the results to an unmixed reference reservoir. We observed significant increases in the biomass of cyanobacteria (from 0.8 ± 0.2 to 2.4 ± 1.1 μg L−1, p = 0.008), cryptophytes (from 0.7 ± 0.1 to 1.9 ± 0.6 μg L−1, p = 0.003), and green algae (from 3.8 to 4.4 μg L−1, p = 0.15) after our first mixing event, likely due to increased total phosphorus from entrainment of upstream sediments. After the second mixing event, phytoplankton biomass did not change but phytoplankton community composition shifted from taxa with filamentous morphology to smaller, rounder taxa. Our results suggest that whole-ecosystem dynamics and phytoplankton morphological traits should be considered when predicting phytoplankton community responses to epilimnetic mixing.