Abstract. Anaerobic ammonium oxidation coupled with iron(III) reduction (Feammox) is a recently discovered pathway of nitrogen removal. However, little is known about the pathways of N transformation via Feammox in the Yellow River wetland. In this study, the difference between Feammox in a natural wetland (site YJW) and a crop rotation wetland (site TEH) was researched using isotope tracing and metagenome techniques. The results revealed that Feammox occurred in TEH but not in YJW. The Feammox rates in the TEH samples were 0.02–0.13 mg N kg⁻¹ d⁻¹ in different depth intervals (0–5 cm, 5–10 cm, 10–20 cm, and 20–30 cm), and the maximum value for TEH occurred in the 5–10 cm depth interval. Iron reducing bacteria play an essential role in Feammox. Rotational tillage reduced the microbial diversity of the iron-reducing bacteria, but it increased the abundance of iron-reducing bacteria at the genus level, and the dominate iron-reducing bacteria responsible for the Feammox process were Anaeromyxobacter and Geobacter. The Feammox rate was less than the denitrification rate (0.55–1.09 mg N kg⁻¹ d⁻¹), an estimated nitrogen loss of 1.1–7.1 t N km⁻² a⁻¹ was associated with the Feammox in the wetland. However, the correlation between the functional genes of the iron-reducing bacteria and the rate remains unclear. Overall, the co-occurrence of ammonium oxidation and iron reduction suggest that Feammox can play an essential role in the pathway of nitrogen removal in the Yellow River wetland.

中文翻译：

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黄河湿地厌氧铵氧化与三价铁还原的氮损失证据

摘要。厌氧氨氧化结合铁 (III) 还原 (Feammox) 是最近发现的脱氮途径。然而，人们对黄河湿地中 Feammox 的 N 转化途径知之甚少。在本研究中，使用同位素示踪和宏基因组技术研究了 Feammox 在自然湿地（站点 YJW）和作物轮作湿地（站点 TEH）中的差异。结果表明，Feammox 发生在 TEH 而不是 YJW 中。TEH 样品中的 Feammox 比率为 0.02–0.13 mg N kg ⁻¹ d ⁻¹在不同深度间隔（0-5 cm、5-10 cm、10-20 cm 和 20-30 cm）中，TEH 的最大值出现在 5-10 cm 深度间隔中。铁还原菌在 Feammox 中起着至关重要的作用。轮耕降低了铁还原菌的微生物多样性，但在属水平上增加了铁还原菌的丰度，而负责 Feammox 过程的主要铁还原菌是厌氧粘杆菌和地杆菌。Feammox 速率小于反硝化速率 (0.55–1.09 mg N kg ⁻¹ d ⁻¹ )，估计氮损失为 1.1–7.1 t N km ⁻² a ⁻¹与湿地的Feammox有关。然而，铁还原菌的功能基因与该速率之间的相关性仍不清楚。总的来说，氨氧化和铁还原的同时发生表明 Feammox 可以在黄河湿地的氮去除途径中发挥重要作用。