Collaborative Research: Quantifying nitrous oxide sources across an oxygen gradient in the northern Benguela upwelling system

合作研究：量化本格拉北部上升流系统氧气梯度中的一氧化二氮来源

• 批准号: 2113937
• 负责人: Karen Casciotti
• 金额: $ 77.62万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2113937&HistoricalAwards=false
• 关键词: Collaborative; Research; Quantifying; nitrous; oxide

Nitrous oxide is a potent greenhouse gas that also contributes to ozone destruction in the upper atmosphere. Sources of nitrous oxide to the atmosphere involve the activity of microbes (bacteria and archaea) in the ocean, particularly where oxygen is scarce. Although marine environments low in dissolved oxygen occur in both the Atlantic and Pacific oceans, much of what is known about microbial nitrous oxide production in the ocean is based on data from the Eastern Tropical Pacific. Substantially less research has focused on the Eastern Tropical Atlantic, such as the northern Benguela Upwelling System (nBUS), where high nitrous oxide fluxes have been observed. The lack of measurements, combined with a limited understanding of the microbial pathways that lead to nitrous oxide production, creates uncertainty in predictions about future ocean emissions of nitrous oxide. Therefore, the overall project goal is to quantify nitrous oxide cycling rates and determine microbial pathways across an oxygen gradient in the world’s most productive upwelling system – the nBUS. The project will support training of two graduate students and a postdoctoral researcher. The PIs and graduate students will participate in the African Regional Graduate Network in Oceanography (RGNO) Discovery Camp in Namibia, Africa, thus the proposed research is fully nested in broader impacts activities. Further, the PI will host a graduate student from the University of Namibia, Africa at Florida State University to transfer knowledge regarding methods used in microbial ecology, bioinformatics and statistical analyses in years two and three. This project has two specific objectives, with the first being to determine the spatial distribution of nitrous oxide production rates and mechanisms using 15N tracers and natural abundance isotope and isotopomer analyses. The second objective is to determine the relationship between dissolved oxygen concentrations and microbial community structure, microbial function and metabolic activities that lead to nitrous oxide production, resolving the active microbial pathways that lead to the observed isotopic data from the first objective. The relative contributions of different pathways to nitrous oxide accumulation will be tested through a combination of 15N tracer experiments, natural abundance isotope and isotopomer analyses, and 16S rRNA gene, metagenome and metatranscriptome sequencing. The proposed work will model the distributions of nitrous oxide bulk and site-specific isotope ratios using nitrate and nitrite isotope measurements as inputs and will test the rates and environmental controls determined in incubation experiments to assess consistency with the longer-term isotopic measurements. The molecular data will also inform the interpretation of the isotopic data, further resolving nitrous oxide source mechanisms and activity.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

一氧化二氮是一种强效温室气体，也会破坏高层大气中的臭氧。大气中一氧化二氮的来源涉及海洋中微生物（细菌和古细菌）的活动，特别是在氧气稀缺的地方。溶解氧存在于大西洋和太平洋中，关于海洋中微生物一氧化二氮产生的大部分知识都是基于东热带太平洋的数据，很少有研究关注这一点。热带大西洋东部，例如本格拉北部上升流系统（nBUS），观测到一氧化二氮通量较高。由于缺乏测量，加上对导致一氧化二氮产生的微生物途径了解有限，造成了预测的不确定性。因此，整个项目的目标是量化一氧化二氮的循环速率，并确定世界上生产力最高的上升流系统中氧气梯度的微生物路径。该项目将支持培训两名研究生和一名博士后研究员，PI 和研究生将参加非洲纳米比亚的非洲区域海洋学研究生网络 (RGNO) 探索营，因此拟议的研究完全嵌套在更广泛的范围内。此外，项目负责人将在第二年和第三年接待来自非洲纳米比亚大学的研究生，以传授有关微生物生态学、生物信息学和统计分析方法的知识。目标，第一个目标是使用 15N 示踪剂和自然丰度同位素和同位素异构体分析确定一氧化二氮生成速率的空间分布和机制，第二个目标是确定溶解氧浓度与微生物群落结构、微生物功能和代谢之间的关系。导致一氧化二氮产生的活动，解决导致从第一个目标观察到的同位素数据的活性微生物途径。将测试不同途径对一氧化二氮积累的相对贡献。通过结合 15N 示踪剂实验、自然丰度同位素和同位素异构体分析以及 16S rRNA 基因、宏基因组和宏转录组测序，拟议的工作将使用硝酸盐和亚硝酸盐同位素测量值作为输入来模拟一氧化二氮本体和位点特异性同位素比率的分布。并将测试孵化实验中确定的速率和环境控制，以评估与长期同位素测量的一致性。还为同位素数据的解释提供信息，进一步解决一氧化二氮的来源机制和活动。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。