Nitrite oxidation exceeds reduction and fixed nitrogen loss in anoxic Pacific waters
Nitrite oxidation exceeds reduction and fixed nitrogen loss in anoxic Pacific waters
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DOI：
10.1016/j.marchem.2020.103814
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发表时间：
2020-08-20
期刊：
影响因子：
3
通讯作者：
Ward, Bess B.
中科院分区：
文献类型：
--
作者：
Babbin, Andrew R.;Buchwald, Carolyn;Ward, Bess B.
缺氧沃茨中氮基异化代谢的多样性随着对海洋缺氧区（ODZ）的进一步研究而不断增加。尽管亚硝酸盐（NO2-）的微生物氧化已经知道了超过世纪，但对所涉及的途径和微生物的研究通常是在亚硝酸盐氧化为硝酸盐需要分子氧（O-2）的假设下进行的。到目前为止，厌氧NO2-氧化仅在厌氧氨氧化细菌中得到了最终证明，尽管与NO2-还原为N-2相比，在其代谢中NO2-仅作为有限的汇。在这里，使用直接的实验技术优化复制原位缺氧条件下，我们表明，NO（2）（-）氧化是大量的，广泛的，并在整个东热带太平洋ODZs一致。无论具体的氧化剂，NO2-氧化速率是一个数量级大于同步N-2生产率，这些区域是已知的，不能单独用厌氧氨氧化速率解释。缺氧沃茨中NO2-氧化速率高于还原速率是矛盾的，但有助于解释在ODZ边缘但不在ODZ核心内的浅缺氧沃茨中厌氧氨氧化速率如何高于反硝化速率（σ（θ）< 26.4）。此外，亚硝酸盐氧化可能是调和全球固定氮损失预算感知不平衡的关键。
The diversity of nitrogen-based dissimilatory metabolisms in anoxic waters continues to increase with additional studies to the marine oxygen deficient zones (ODZs). Although the microbial oxidation of nitrite (NO2-) has been known for over a century, studies of the pathways and microbes involved have generally proceeded under the assumption that nitrite oxidation to nitrate requires dioxygen (O-2). Anaerobic NO2- oxidation until now has been conclusively shown only for anammox bacteria, albeit only as a limited sink for NO2- in their metabolism compared to the NO2- reduced to N-2. Here, using direct experimental techniques optimized for replicating in situ anoxic conditions, we show that NO(2)(- )oxidation is substantial, widespread, and consistent across the ODZs of the eastern tropical Pacific Ocean. Regardless of the specific oxidant, NO2- oxidation rates are up to an order of magnitude larger than simultaneous N-2 production rates for which these zones are known, and cannot be explained by anammox rates alone. Higher rates of NO2- oxidation over reduction in anoxic waters are paradoxical but help to explain how anammox rates can be enhanced over denitrification in shallow anoxic waters (sigma(theta) < 26.4) at the edge of the ODZs but not within the ODZ core. Furthermore, nitrite oxidation may be the key to reconciliation of the perceived imbalance of the global fixed nitrogen loss budget.