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（N2O）是水生和陆地环境中微生物产生的气体，与其他温室气体一样，它有助于全球变暖。此外，N2O可以破坏臭氧，这是一种负责保护地球免受危险紫外线辐射的气体。在海洋中，N2O的产生在很大程度上受到可用溶解氧的量，而在低氧气浓度下产生了更多的N2O。但是，当没有氧气可用的情况下，一种称为缺氧的方案，海洋中的微生物从生产N2O转变为消耗N2O。近年来，已经很明显的是，低氧区域在海洋的某些地区正在扩大，这引起了人们对将产生更多N2O的担忧。如果发生这种情况，将会将更多的N2O散发到大气中，并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低氧条件下海洋中产生多少N2O。但是，如果缺氧区域的大小也会增加，则至少在某种程度上可以平衡，这是由于存在氧气而但低浓度的区域的膨胀而预测的N2O产生增加。这项研究旨在同时测量低氧和缺氧区域的N2O生产和消费，并确定负责N2O生产和消费的微生物。我们的结果将：1）更好地理解缺氧区域的N2O消耗如何有助于平衡N2O生产的增加，如果海洋中的低氧区域继续扩展，2）有助于告知旨在预测海洋N2O生产并在大气中排放到大气中的海洋生产和对未来海洋的排放的模型，以及3）使我们能够更好地了解N2O的生产和消费n2O的生产和消费。我们的研究将支持将在海洋化学和社区基因组学界面工作的博士后和本科生。 PIS计划特别考虑机构有限的机构中代表性不足的少数民族和学生的申请。 PIS还计划了许多其他教育/外展计划，包括教师培训研讨会，教师实习以及学术和公共讲座系列。随着溶解的氧气（DO）浓度从氧化物到低氧的过渡，有效的温室和臭氧破坏气体一氧化二氮（N2O）的海洋产量增加。随着气候变化的影响，全球海洋DO浓度已降低，海洋低氧区已经扩大并预测将继续扩大。这种增加的原因是人们担心海洋中的N2O生产将来会增加，这将导致对大气的排放更高。结果，许多研究重点是量化与N2O产生大幅增加相对应的氧阈值。相比之下，相对较少的研究旨在量化净N2O消耗的能力，这是由于缺氧条件下的微生物N2O将N2O降低至N2，以防止预测的N2O产生增加，如果缺氧区与低氧区域结合使用。为此，这项研究的目的是同时量化N2O的N2O生产和消耗，以确定N2O消耗的潜力抵消N2O生产的预测增加。我们的现场工作是在不列颠哥伦比亚峡湾的Saanich Inlet进行的，这是我们研究的理想天然实验室，因为它的特征是良好的氧气和缺氧区。具体而言，我们的目的是1）测量大量N2O浓度，并使用15N示踪技术来量化N2O的生产和消耗率，而浓度从耐药物到缺氧条件下降低，2）量化N2O在缺氧区域中N2O消耗的数量量增加了N2O在缺氧区域中增加N2O的N2O生产，并确定了N2O的N2O生产，并确定的N2ORISTOR和3）与32O链接相关，并与3）链接，3）介导此过程，专门针对通过脱氧符（NO3-至N2）与非否认剂（仅N2O至N2）分类单元的N2O消耗区分。最终，我们的结果将提供有关N2O消耗率在波动的海洋条件上的定量信息，从而有助于限制氧对净N2O生产和海洋至大麻温室气体通量的影响模型。此外，这项工作将确定能够减少N2O的微生物的分类广度及其与实际的N2O降低率的联系，从而提供了对特定生物签名的检测是否预测海洋N2O动态的定量理解，这些奖项反映了NSF的法规及其依据，这表明了NSF的正定及其依据，这是在构成的范围内的依据，这是构成的支持。 标准。