N2 production rates limited by nitrite availability in the Bay of Bengal oxygen minimum zone
N2 production rates limited by nitrite availability in the Bay of Bengal oxygen minimum zone
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DOI：
10.1038/ngeo2847
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发表时间：
2017-01-01
影响因子：
18.3
通讯作者：
Canfield, D. E.
中科院分区：
文献类型：
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作者：
Bristow, L. A.;Callbeck, C. M.;Canfield, D. E.
海洋中三分之一或更多的固定氮以N-2的形式流失，是通过开阔海洋最低氧区的厌氧微生物过程去除的。在过去的几十年里，这些区域已经扩大，进一步的人为扩张可能会加速氮的流失。然而，在孟加拉湾，尽管氧气水平低于常规方法的检测水平（1至2 μ M），但没有迹象表明氮损失。在这里，我们量化了与N-2产生相关的微生物基因的丰度，测量了采样海水与同位素标记的氮化合物孵育中的氮转化，并分析了水柱中这些过程的地球化学特征。我们发现，孟加拉湾支持厌氧氨氧化微生物种群，介导低，但显着的N损失。然而，与其他氧气最小区域不同，我们使用高灵敏度氧气传感器进行的测量表明，孟加拉湾的氧气浓度持续在10至200 nM范围内。我们建议，这种氧支持亚硝酸盐氧化，从而限制了亚硝酸盐的厌氧氨氧化或反硝化。如果这些微量的氧气被移除，孟加拉湾氧气最小区沃茨的氮损失可能会加速到全球性的意义。
A third or more of the fixed nitrogen lost from the oceans as N-2 is removed by anaerobic microbial processes in open ocean oxygen minimum zones. These zones have expanded over the past decades, and further anthropogenically induced expansion could accelerate nitrogen loss. However, in the Bay of Bengal there has been no indication of nitrogen loss, although oxygen levels are below the detection level of conventional methods (1 to 2 mu M). Here we quantify the abundance of microbial genes associated with N-2 production, measure nitrogen transformations in incubations of sampled seawater with isotopically labelled nitrogen compounds and analyse geochemical signatures of these processes in the water column. We find that the Bay of Bengal supports denitrifier and anammox microbial populations, mediating low, but significant N loss. Yet, unlike other oxygen minimum zones, our measurements using a highly sensitive oxygen sensor demonstrate that the Bay of Bengal has persistent concentrations of oxygen in the 10 to 200 nM range. We propose that this oxygen supports nitrite oxidation, thereby restricting the nitrite available for anammox or denitrification. If these traces of oxygen were removed, nitrogen loss in the Bay of Bengal oxygen minimum zone waters could accelerate to global significance.