Collaborative Research: Nitrous oxide reduction in oxygen minimum zones: an understudied but critical loss term in ocean greenhouse gas cycling

合作研究：最低氧气区的一氧化二氮还原：海洋温室气体循环中一个尚未充分研究但至关重要的损失项

• 批准号: 2341290
• 负责人: Damian Grundle
• 金额: $ 54.58万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-10-01 至 2025-02-28
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2341290&HistoricalAwards=false
• 关键词: Collaborative; Research; Nitrous; oxide; reduction

Nitrous oxide (N2O) is a gas produced by microbes in both aquatic and terrestrial environments, and, like other greenhouse gases, it contributes to global warming. Furthermore, N2O can destroy ozone, a gas responsible for protecting the earth from dangerous ultraviolet radiation. In the ocean, N2O production is largely controlled by the amount of available dissolved oxygen, with more N2O being produced under low oxygen concentrations; however, when no oxygen is available, a scenario referred to as anoxia, microbes in the ocean switch from producing N2O to consuming N2O. In recent years, it has become evident that zones of low oxygen are expanding in some areas of the oceans, and this has raised concern that more N2O will be produced. If this occurs, more N2O will be emitted to the atmosphere, and will lead to further global warming and ozone destruction. Because of this, research has largely focused on understanding how much N2O is produced in the ocean under low oxygen conditions. If, however, anoxic zones also increase in size, this could act to balance out, at least to some degree, the predicted increase in N2O production caused by the expansion of zones where oxygen is present but in low concentrations. This study aims to simultaneously measure N2O production and consumption, in both low oxygen and anoxic zones and identify the microbes responsible for N2O production and consumption. Our results will: 1) lead to a much better understanding of how N2O consumption in anoxic zones could help to balance out an increase in N2O production if low oxygen zones in the ocean continue to expand, 2) help to inform models aimed at predicting oceanic N2O production and emissions to the atmosphere under future ocean conditions, and 3) allow us to better understand the microbes involved in N2O production and consumption. Our study will support a postdoc and undergraduate students who will work at the interface of marine chemistry and community genomics. The PIs plan to specifically consider applications from underrepresented minorities and students at institutions with limited opportunities. The PIs also plan a number of other educational/outreach programs ranging from teacher-training workshops, teacher internships, and academic and public lecture series. The oceanic production of the potent greenhouse and ozone destroying gas nitrous oxide (N2O) increases as dissolved oxygen (DO) concentrations transition from oxic to hypoxic. Marine DO concentrations have decreased globally with climate change and oceanic hypoxic zones have expanded and predicted to continue expanding. This increase is cause for concern that N2O production in the ocean will increase in the future which would lead to higher emissions to the atmosphere. As a result, much research has focused on quantifying the oxygen thresholds that correspond to large increases in N2O production. In contrast, relatively few studies have aimed to quantify the capacity for net N2O consumption, resulting from microbial N2O reduction to N2 under anoxic conditions, to buffer against predicted N2O production increases if anoxic zones expand in conjunction with hypoxic zones. To this end, this study aims to simultaneously quantify N2O production and consumption from oxic-hypoxic-anoxic water column zones, in order to determine the potential for N2O consumption to counteract predicted increases in N2O production. Our field work be conducted in Saanich Inlet, a British Columbian fjord which is an ideal natural laboratory for our study, as it is characterized by a well-established oxycline and anoxic zone. Specifically, we aim to 1) measure bulk N2O concentrations, and, using 15N tracer techniques, quantify N2O production and consumption rates as DO concentrations decrease from oxic to anoxic conditions, 2) quantify the magnitude by which N2O consumption in the anoxic zone balances increased N2O production in the overlying hypoxic region, and 3) definitively link observed N2O production and consumption rates to the microorganisms mediating this process, focusing specifically on distinguishing N2O consumption via denitrifier (NO3- to N2) versus non-denitrifier (N2O to N2 only) taxa. Ultimately, our results will provide quantitative information on N2O consumption rates over fluctuating ocean conditions, thereby helping constrain models of oxygen effects on net N2O production and ocean-to-atmosphere greenhouse gas fluxes. Furthermore, this work will identify the taxonomic breadth of microbes capable of N2O reduction and their linkage to actual N2O reduction rates, thereby providing a quantitative understanding of whether or not the detection of specific bio-signatures is predictive of marine N2O dynamics.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（N2 O）是由水生和陆地环境中的微生物产生的气体，与其他温室气体一样，它有助于全球变暖。此外，N2 O会破坏臭氧，臭氧是一种负责保护地球免受危险的紫外线辐射的气体。在海洋中，N2 O的产生在很大程度上受可用溶解氧的量控制，在低氧浓度下产生更多的N2 O;然而，当没有氧气时，称为缺氧的情况下，海洋中的微生物从产生N2 O转换为消耗N2 O。近年来，很明显，海洋某些地区的低氧区正在扩大，这引发了人们对将产生更多N2 O的担忧。如果发生这种情况，更多的N2 O将被排放到大气中，并将导致进一步的全球变暖和臭氧破坏。因此，研究主要集中在了解在低氧条件下海洋中产生多少N2 O。然而，如果缺氧区的大小也增加，这至少在某种程度上可以起到平衡N2 O产量的预测增加的作用，所述N2 O产量的预测增加是由存在氧气但浓度低的区域的扩张引起的。本研究的目的是同时测量N2 O的生产和消费，在低氧和缺氧区，并确定微生物负责N2 O的生产和消费。我们的结果将：1）导致更好地了解缺氧区的N2 O消耗如何有助于平衡N2 O生产的增加，如果海洋中的低氧区继续扩大，2）有助于为旨在预测未来海洋条件下海洋N2 O生产和向大气排放的模型提供信息，3）使我们能够更好地了解参与N2 O生产和消费的微生物。我们的研究将支持博士后和本科生谁将在海洋化学和社区基因组学的接口工作。PI计划特别考虑代表性不足的少数民族和机会有限的机构的学生的申请。PI还计划了一些其他教育/推广方案，包括教师培训讲习班，教师实习以及学术和公共讲座系列。随着溶解氧（DO）浓度从好氧转变为缺氧，海洋产生的强有力的温室气体和臭氧破坏气体一氧化二氮（N2 O）增加。随着气候变化，全球海洋溶解氧浓度下降，海洋缺氧区扩大，预计将继续扩大。这一增加令人担忧的是，海洋中的N2 O生产将在未来增加，这将导致向大气排放更多。因此，许多研究都集中在量化对应于N2 O产量大幅增加的氧气阈值。相比之下，相对较少的研究旨在量化的能力，净N2 O消耗，导致微生物N2 O还原为N2在缺氧条件下，缓冲预测的N2 O生产增加，如果缺氧区扩大与缺氧区。为此，本研究的目的是同时量化N2 O的生产和消费从缺氧-缺氧水柱区，以确定潜在的N2 O消费，以抵消预测的增加N2 O生产。我们的野外工作将在Saanich Inlet进行，这是一个不列颠哥伦比亚峡湾，是我们研究的理想天然实验室，因为它的特点是一个完善的氧跃层和缺氧区。具体来说，我们的目标是1）测量散装N2 O浓度，并使用15 N示踪技术，量化N2 O的生产和消耗率，因为DO浓度从好氧到缺氧条件下减少，2）量化的幅度，其中N2 O消耗在缺氧区平衡增加的N2 O生产在上覆缺氧区，和3）明确地将观察到的N2 O产生和消耗速率与介导该过程的微生物联系起来，特别关注通过分解器（NO3-至N2）与非分解器（仅N2 O至N2）分类群区分N2 O消耗。最终，我们的研究结果将提供有关波动的海洋条件下N2 O消耗率的定量信息，从而有助于限制氧气对净N2 O生产和海洋-大气温室气体通量的影响模型。此外，这项工作将确定能够减少N2 O的微生物的分类宽度及其与实际N2 O减少率的联系，从而提供对特定生物标志物的检测是否该奖项反映了NSF的法定使命，并被认为值得通过利用基金会的知识价值和更广泛的影响审查进行评估来支持的搜索.