Center for Water and Ecology, State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, 100084, Beijing, China.
Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China.
Chemosphere. 2021 Apr;269:128702. doi: 10.1016/j.chemosphere.2020.128702. Epub 2020 Oct 30.
Biogeochemical hotspots of nitrogen cycling such as ammonia oxidation commonly occur in riparian ecosystems. However, the responses of ammonia-oxidizing archaea (AOA) and bacteria (AOB) to water-level fluctuations (WLF) in riparian zones remain unclear. In this study, two patterns of WLF (gradual waterlogging and drying) were investigated in a 9-month column experiment, and the abundances and activities of AOA and AOB were investigated. The recovery evaluation revealed AOB abundance had not returned to the initial level at the end of the experiment, while AOA abundance had recovered nearly completely. AOA outnumbered AOB at almost all depths, and AOA showed higher resistance and adaptation to WLF than AOB. However, higher microbial abundance was not always linked to the larger contribution to nitrification. Changes in environmental parameters such as moisture and dissolved oxygen caused by WLF instead of ammonia-oxidizing microorganism (AOM) abundance might play a key role in regulating the expression of amoA gene and thus the activity of ammonia oxidizers. In addition, the community structure of AOM evolved over the incubation period. The composition of AOA species in sediment changed in the same way as that in soil, and the Nitrosopumilus cluster showed strong resistance to WLF. Conversely, waterlogging changed the community structure of AOB in soil while drying had no significant effect on the AOB community structure in sediment. This study suggests that the ammonia oxidizers will respond to WLF and eventually affect N fate in riparian ecosystems considering the coupling with other N transformation processes.
氮循环的生物地球化学热点，如氨氧化作用，通常发生在河岸生态系统中。然而，氨氧化古菌（AOA）和细菌（AOB）对河岸带水分波动（WLF）的响应仍不清楚。在这项研究中，通过 9 个月的柱状实验，研究了两种 WLF 模式（逐渐渍水和干燥），并调查了 AOA 和 AOB 的丰度和活性。恢复评估表明，实验结束时 AOB 的丰度尚未恢复到初始水平，而 AOA 的丰度已几乎完全恢复。在几乎所有深度，AOA 的数量都超过了 AOB，AOA 对 WLF 的抵抗力和适应性都高于 AOB。然而，较高的微生物丰度并不总是与硝化作用的较大贡献相关。WLF 引起的环境参数（如水分和溶解氧）的变化，而不是氨氧化微生物（AOM）丰度的变化，可能在调节 amoA 基因的表达以及氨氧化菌的活性方面发挥关键作用。此外，AOM 的群落结构在孵育期间发生了演变。沉积物中 AOA 物种的组成与土壤中的组成方式相同，而 Nitrosopumilus 类群对 WLF 表现出很强的抵抗力。相反，渍水改变了土壤中 AOB 的群落结构，而干燥对沉积物中 AOB 群落结构没有显著影响。本研究表明，考虑到与其他氮转化过程的耦合，氨氧化菌将对 WLF 做出响应，并最终影响河岸带生态系统中的氮命运。
