State Key Laboratory of Estuarine and Coastal Research, Yangtze Delta Estuarine Wetland Ecosystem Observation and Research Station, Ministry of Education & Shanghai, East China Normal University, Shanghai 200241, China.
Key Laboratory of Geographic Information Science of the Ministry of Education, School of Geographic Sciences, East China Normal University, Shanghai 200241, China.
Environ Sci Technol. 2024 Mar 19;58(11):4989-5002. doi: 10.1021/acs.est.3c10691. Epub 2024 Mar 5.
Global warming and acidification, induced by a substantial increase in anthropogenic CO emissions, are expected to have profound impacts on biogeochemical cycles. However, underlying mechanisms of nitrous oxide (NO) production in estuarine and coastal sediments remain rarely constrained under warming and acidification. Here, the responses of sediment NO production pathways to warming and acidification were examined using a series of anoxic incubation experiments. Denitrification and NO production were largely stimulated by the warming, while NO production decreased under the acidification as well as the denitrification rate and electron transfer efficiency. Compared to warming alone, the combination of warming and acidification decreased NO production by 26 ± 4%, which was mainly attributed to the decline of the NO yield by fungal denitrification. Fungal denitrification was mainly responsible for NO production under the warming condition, while bacterial denitrification predominated NO production under the acidification condition. The reduced site preference of NO under acidification reflects that the dominant pathways of NO production were likely shifted from fungal to bacterial denitrification. In addition, acidification decreased the diversity and abundance of -type denitrifiers, which were the keystone taxa mediating the low NO production. Collectively, acidification can decrease sediment NO yield through shifting the responsible production pathways, partly counteracting the warming-induced increase in NO emissions, further reducing the positive climate warming feedback loop.
全球变暖与酸化是由人为 CO2 排放大量增加所导致的，预计会对生物地球化学循环产生深远影响。然而，在变暖与酸化条件下，河口及海岸带沉积物中氧化亚氮（N2O）的产生机制仍鲜有研究。本研究采用一系列缺氧培养实验，研究了变暖与酸化对沉积物 N2O 产生途径的响应。结果表明，变暖显著刺激了反硝化和 N2O 产生，但酸化会降低 N2O 产生速率以及反硝化速率和电子传递效率。与单独变暖相比，变暖与酸化的联合作用使 N2O 产生降低了 26±4%，这主要归因于真菌反硝化的 N2O 得率下降。变暖条件下，真菌反硝化是 N2O 产生的主要途径，而酸化条件下，细菌反硝化则主导了 N2O 产生。酸化条件下 N2O 的位选择性降低表明，N2O 产生的主要途径可能从真菌反硝化向细菌反硝化转移。此外，酸化降低了 -型反硝化菌的多样性和丰度，这些菌是介导低 N2O 产生的关键类群。综上，酸化可通过改变相关产生途径降低沉积物 N2O 得率，部分抵消了变暖引起的 N2O 排放增加，从而进一步减少正的气候变暖反馈循环。
