Regulation of nitrous oxide production in low-oxygen waters off the coast of Peru
Regulation of nitrous oxide production in low-oxygen waters off the coast of Peru
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DOI：
10.5194/bg-17-2263-2020
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发表时间：
2020-04-22
期刊：
影响因子：
4.9
通讯作者：
Ward, Bess B.
中科院分区：
文献类型：
--
作者：
Frey, Claudia;Bange, Hermann W.;Ward, Bess B.
缺氧区(ODZ)是天然一氧化二氮(N2O)净产生和排放的主要场所。为了了解N2O产生量随全球变化的变化，需要了解主要微生物途径(硝化和反硝化)对N2O产生量的个别贡献及其调节。在秘鲁近海的ODZ，采用N-15示踪实验，结合定量聚合酶链式反应(QPCR)和功能基因芯片分析，分别以古细菌amoA和NIRS为硝化和反硝化的标记基因，研究了N2O产生对氧气和有机物的敏感性。反硝化作用的N2O产生量最高，平均值为8.7nmoL L~(-1)d(-1)，而在缺氧-好氧界面下，反硝化作用的N2O产生量最高，为118nmolL~(-1)d(~(-1))。氨氧化产生N2O的最高值为0.16+/-0.003 nmoL·L~(-1)d(-1)，出现在氧浓度为10~30 mU·mol·L~(-1)的上跃层，与古AMOA转录本/基因的最高值相吻合。混合生成N2O(即一个N原子来自NH(4)(+)，另一个来自其他底物，如NO2)是优势物种，占NH4+产生的N2O总量的70%-85%，无论氨氧化速率或O-2浓度如何。不同基质对N2O产生的氧响应不同，但产量和产量一般在10 mU·moL·L-1·O-2以下最高。颗粒有机物的添加使反硝化产生的N2O增加了5倍，这表明在颗粒有机物输出较高的时期，N2O的产生增加了。测得氧化亚氮的产生率高达2.1%，但氧化亚氮的总体贡献仍比反硝化低一个数量级。因此，这些发现表明，在以有机碳供应为燃料的低氧条件下，反硝化是最重要的N2O产生过程，这意味着海洋总N2O来源对海洋脱氧作用的响应是正反馈。
Oxygen-deficient zones (ODZs) are major sites of net natural nitrous oxide (N2O) production and emissions. In order to understand changes in the magnitude of N2O production in response to global change, knowledge on the individual contributions of the major microbial pathways (nitrification and denitrification) to N2O production and their regulation is needed. In the ODZ in the coastal area off Peru, the sensitivity of N2O production to oxygen and organic matter was investigated using N-15 tracer experiments in combination with quantitative PCR (qPCR) and microarray analysis of total and active functional genes targeting archaeal amoA and nirS as marker genes for nitrification and denitrification, respectively. Denitrification was responsible for the highest N2O production with a mean of 8.7 nmol L-1 d(-1) but up to 118 +/- 27.8 nmol L-1 d(-1) just below the oxic-anoxic interface. The highest N2O production from ammonium oxidation (AO) of 0.16 +/- 0.003 nmol L-1 d(-1) occurred in the upper oxycline at O-2 concentrations of 10-30 mu mol L-1 which coincided with the highest archaeal amoA transcripts/genes. Hybrid N2O formation (i.e., N2O with one N atom from NH(4)(+)and the other from other substrates such as NO2) was the dominant species, comprising 70 %-85% of total produced N2O from NH4+, regardless of the ammonium oxidation rate or O-2 concentrations. Oxygen responses of N2O production varied with substrate, but production and yields were generally highest below 10 mu mol L-1 O-2. Particulate organic matter additions increased N2O production by denitrification up to 5-fold, suggesting increased N2O production during times of high particulate organic matter export. High N2O yields of 2.1% from AO were measured, but the overall contribution by AO to N2O production was still an order of magnitude lower than that of denitrification. Hence, these findings show that denitrification is the most important N2O production process in low-oxygen conditions fueled by organic carbon supply, which implies a positive feedback of the total oceanic N2O sources in response to increasing oceanic deoxygenation.