Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, China.
School of Geography, Nanjing Normal University, Nanjing, China.
Glob Chang Biol. 2021 Nov;27(21):5564-5579. doi: 10.1111/gcb.15863. Epub 2021 Sep 3.
Ocean acidification in nitrogen-enriched estuaries has raised global concerns. For decades, biotic and abiotic denitrification in estuarine sediments has been regarded as the major ways to remove reactive nitrogen, but they occur at the expense of releasing greenhouse gas nitrous oxide (N O). However, how these pathways respond to acidification remains poorly understood. Here we performed a N O isotopocules analysis coupled with respiration inhibition and molecular approaches to investigate the impacts of acidification on bacterial, fungal, and chemo-denitrification, as well as N O emission, in estuarine sediments through a series of anoxic incubations. Results showed that acidification stimulated N O release from sediments, which was mainly mediated by the activity of bacterial denitrifiers, whereas in neutral environments, N O production was dominated by fungi. We also found that the contribution of chemo-denitrification to N O production cannot be ignored, but was not significantly affected by acidification. The mechanistic investigation further demonstrated that acidification changed the keystone taxa of sedimentary denitrifiers from N O-reducing to N O-producing ones and reduced microbial electron-transfer efficiency during denitrification. These findings provide novel insights into how acidification stimulates N O emission and modulates its pathways in estuarine sediments, and how it may contribute to the acceleration of global climate change in the Anthropocene.
富氮河口的海洋酸化引起了全球关注。几十年来，河口沉积物中的生物和非生物反硝化作用一直被认为是去除活性氮的主要途径，但它们是以释放温室气体氧化亚氮（N O）为代价的。然而，这些途径如何响应酸化仍然知之甚少。在这里，我们通过一系列缺氧培养，结合 N O 同位素示踪分析、呼吸抑制和分子方法，研究了酸化对河口沉积物中细菌、真菌和化学反硝化作用以及 N O 排放的影响。结果表明，酸化刺激了沉积物中 N O 的释放，这主要是由细菌反硝化作用介导的，而在中性环境中，N O 的产生主要由真菌主导。我们还发现，化学反硝化作用对 N O 产生的贡献不可忽视，但不受酸化的显著影响。机制研究进一步表明，酸化改变了沉积物反硝化作用的关键类群，从 N O 还原型变为 N O 产生型，并降低了反硝化过程中的微生物电子传递效率。这些发现为我们提供了新的见解，即酸化如何刺激 N O 的排放，并调节河口沉积物中 N O 的途径，以及它如何可能导致人类世全球气候变化的加速。
