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.

一氧化二氮是一种潜在的温室气体，也导致高层大气中的臭氧破坏。一氧化二氮对大气的来源涉及海洋中微生物（细菌和古细菌）的活性，尤其是在氧气稀缺的地方。尽管在大西洋和太平洋中都出现了低溶解氧的海洋环境，但海洋中微生物氧化二氮的许多已知是基于东部热带太平洋的数据。研究的重点大大减少了东部热带大西洋，例如北部的宾格拉上升流系统（NBUS），在那里观察到了高一氧化二氮通量。缺乏测量，加上对导致一氧化二氮产生的微生物途径的有限理解，在对一氧化二氮的未来海洋排放的预测中造成了不确定性。因此，总体项目目标是量化一氧化二氮的循环速率，并确定世界上最有生产力的上升流入系统中的氧气梯度（NBUS）中的微生物途径。该项目将支持两名研究生和一名博士后研究员的培训。 PIS和研究生将参加非洲纳米比亚的非洲海洋学区域研究生网络（RGNO）探索营，因此拟议的研究完全嵌入了更广泛的影响活动中。此外，PI将接待佛罗里达州立大学纳米比亚大学的一名研究生，以转移有关二和三年中微生物生态学，生物信息学和统计分析中使用的方法的知识。该项目有两个特定的目标，首先是使用15N示踪剂以及自然丰度同位素和同位素分析来确定一氧化二氮的生产率和机制的空间分布。第二个目标是确定溶解的氧浓度与微生物群落结构，微生物功能和代谢活性之间的关系，从而导致一氧化二氮的产生，从而解决了从第一个目标导致观察到的同位素数据的活性微生物途径。不同途径对一氧化二氧化物积累的相对贡献将通过15n示踪剂实验，自然抽象同位素和同位素分析以及16S rRNA基因，元基因组和元文字组测序的组合进行测试。所提出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对一氧化二氧化二氧化二氧化二氮的分布进行建模，并将测试在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。分子数据还将为同位素数据的解释提供信息，进一步解决一氧化二氮源机制和活动。该奖项反映了NSF的法定任务，并通过使用基金会的智力优点和更广泛的影响来审查标准，通过评估来诚实地支持支持。