Su Rui, Zhao Dayong, Zhang Xiaomin, Zhang Hongjie, Cheng Junxiang, Xu Ligang, Wu Qinglong L, Zeng Jin
Joint International Research Laboratory of Global Change and Water Cycle, the National Key Laboratory of Water Disaster Prevention, Hohai University, Nanjing 210098, China; Key Laboratory of Lake and Watershed Science for Water Security, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 211135, China.
Joint International Research Laboratory of Global Change and Water Cycle, the National Key Laboratory of Water Disaster Prevention, Hohai University, Nanjing 210098, China.
Water Res. 2025 Apr 15;274:123075. doi: 10.1016/j.watres.2024.123075. Epub 2024 Dec 30.
Flash drought (FD) events induced by climate change may disrupt the normal hydrological regimes of floodplain lakes and affect the plant-microbe mediated dissimilatory nitrate reduction (DNR), i.e., denitrification, anammox and dissimilatory nitrate reduction to ammonium (DNRA), thus having important consequences for nitrous oxide (NO) emissions and nitrogen (N) retention. However, the responses of the DNR pathways in the floodplain lake to the record-breaking FD in 2022 in Yangtze River of China, as well as the underlying microbial mechanisms and feedbacks to climate change remain poorly understood. Here, we collected exposed sediments and Carex cinerascens-associated soils in the littoral wetlands of Poyang Lake during 2022 FD and the dry seasons prior to and after this event. The potential DNR rates and the synergistic metabolism of microbial guilds involved in DNR were investigated using N isotope pairing technique, high-throughput and metagenomic sequencing. We found that the in situ NO fluxes in the littoral wetlands were highest during the flash drought, especially in the exposed sediments. The potential DNRA rates were highest under flash drought conditions, and DNRA dominated the DNR for both exposed sediments (80.4 %) and Carex cinerascens-associated soils (57.5 %). Nutrients (i.e., N and P) and DNRA bacterial communities played a key role in producing the extremely high NO fluxes from exposed sediments, which could be explained by the synergistic metabolism of DNRA bacteria and denitrifiers through the exchange of the key intermediates in DNR. Therefore, the climate change-induced flash drought promoted greater nitrous oxide emissions and N retention in the littoral wetlands of Poyang Lake, producing a greater flux of greenhouse gas emissions and elevating the risk of lake eutrophication. Hence, flash droughts reinforce a positive feedback between climate change and nitrous oxide emission from these aquatic ecosystems.
气候变化引发的骤发干旱（FD）事件可能会扰乱洪泛区湖泊的正常水文状况，并影响植物-微生物介导的异化硝酸盐还原（DNR），即反硝化作用、厌氧氨氧化作用以及异化硝酸盐还原为铵（DNRA），从而对一氧化二氮（N₂O）排放和氮（N）保留产生重要影响。然而，人们对2022年中国长江流域破纪录的骤发干旱期间洪泛区湖泊中DNR途径的响应，以及潜在的微生物机制和对气候变化的反馈仍知之甚少。在此，我们采集了2022年骤发干旱期间以及该事件前后旱季鄱阳湖湖滨湿地中的裸露沉积物和与灰化苔草相关的土壤。使用氮同位素配对技术、高通量测序和宏基因组测序研究了潜在DNR速率以及参与DNR的微生物群落的协同代谢。我们发现，湖滨湿地中的原位N₂O通量在骤发干旱期间最高，尤其是在裸露沉积物中。潜在DNRA速率在骤发干旱条件下最高，并且DNRA在裸露沉积物（80.4%）和与灰化苔草相关的土壤（57.5%）的DNR中均占主导地位。营养物质（即N和P）以及DNRA细菌群落对裸露沉积物中产生极高的N₂O通量起关键作用，这可以通过DNRA细菌和反硝化细菌通过DNR关键中间体的交换进行协同代谢来解释。因此，气候变化引发的骤发干旱促进了鄱阳湖湖滨湿地中一氧化二氮排放增加和氮保留，产生了更大的温室气体排放通量并增加了湖泊富营养化的风险。因此，骤发干旱加强了气候变化与这些水生生态系统一氧化二氮排放之间的正反馈。
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