Collaborative Research: Multiyear autonomous measurement of N-loss in the ETNP ODZ

合作研究：ETNP ODZ 中 N 损失的多年自主测量

• 批准号: 1851361
• 负责人: Mark Altabet
• 金额: $ 59.08万
• 依托单位: University of Massachusetts, Dartmouth
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-03-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1851361&HistoricalAwards=false
• 关键词: Collaborative; Research; Multiyear; autonomous; measurement

Several regions of the deep ocean naturally contain almost no oxygen. Because of this lack of oxygen, microbes living in these regions live in ways that differ from those in oxygenated waters consuming nitrate ions instead of oxygen for respiration. Use of nitrate for microbial respiration results in the production of nitrogen gas which is called denitrification. The resulting removal of nitrate has consequences for the whole ocean as nitrogen is an important nutrient controlling plant growth; however, whereas plants can use nitrogen in the form of nitrate, they cannot, with a few exceptions, use nitrogen gas. There remains a number of uncertainties regarding how much denitrification occurs in the ocean, what controls it, and how it varies in time and space. Traditional studies of ocean denitrification have been limited by the time ships can be at sea and the relatively small proportion of the ocean they can observe. Our project plans to remedy this problem by using vehicles called floats that can operate autonomously in the ocean for three years or more as they drift with currents over hundreds of kilometers. We will outfit ten floats with sensors to measure oxygen and nitrogen gas which will be placed throughout the oxygen-depleted region of the Pacific Ocean to the west of Mexico. This is the largest such region in the ocean from which we have two years of results from a prototype float which validated our approach. This study may well transform our understanding of ocean denitrification and ultimately benefit society as a whole through greater confidence in predictions of the ocean's nitrogen cycle and capacity to fix carbon dioxide under current and future conditions. Application and further development of float systems using commercially available technology will directly benefit successor studies, and more broadly showcase the use of water-following platforms to tackle difficult oceanographic problems. Advances from this study are expected to carry over to other disciplines including ocean biogeochemical modeling. Outreach activities, support for an early career scientist, and student training are included in the project. For the outreach activities, the investigators plan to tie into well-established after-school programs serving underrepresented populations in Massachusetts and established opportunities for public presentations using float related display materials at the University of Washington. Oxygen deficient zones (ODZs), despite constituting a small fraction of total oceanic volume, play important roles in regulating global ocean carbon and nitrogen cycles including hosting 30 to 50% of the global loss of fixed nitrogen. Unfortunately, current uncertainty in ODZ nitrogen loss derives from substantial temporal and spatial variability in rates that remain under-sampled by ship-based measurements. While local regulation of nitrogen loss by oxygen and organic matter availability are well accepted, temporal/spatial variability in the nitrogen flux is likely a result of the influence of physical forcings such as remote ventilation, seasonal variability, and mesoscale eddies. Understanding how the impact of physical forcings on nitrogen loss as mediated through oxygen and organic flux will be required to fully understand the causes and consequences of any future ODZ expansion. To improve our understanding of ODZ nitrogen loss, we will carry out a multiyear, autonomous float-based observational program to address outstanding questions regarding bioavailable nitrogen loss in ODZs. As the largest ODZ and region of our pilot deployments, our operation area will be the Eastern Tropical N. Pacific (ETNP) where our study will determine over a multi-year period, in-situ nM-level oxygen and biogenic nitrogen on float profiles spanning geographic gradients in oxygen and surface productivity. For the first time, our study will also determine in situ nitrogen loss rates from changes in nitrogen concentration during 1 to 2 week Lagrangian float drifts along a constant density surface. A pilot 2 yr float deployment in the ETNP documents our ability to do so. Critically, our float-based approach more closely matches the frequency and distribution of observations to the expected variability in biogenic nitrogen production as compared to prior work and will dramatically increase the data density for this region by acquiring 500 profiles/drifts for nitrogen and 1000 profiles for nM oxygen.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.

深海的几个地区自然没有氧气。 由于缺乏氧气，生活在这些地区的微生物的生活与消耗硝酸盐离子而不是氧气的氧化水的方式不同。 使用硝酸盐用于微生物呼吸会导致氮气的产生，这称为反硝化。 由于氮是控制植物生长的重要营养，因此硝酸盐的去除对整个海洋都有后果。但是，尽管植物可以以硝酸盐的形式使用氮，但除了少数例外，它们不能使用氮气。关于海洋中发生了多少反硝化，控制量以及它如何在时空变化的情况下，仍然存在许多不确定性。 海洋反硝化研究的传统研究受到时间船的限制，并且可以观察到的海洋比例相对较小。 我们的项目计划通过使用称为浮子的车辆来解决这个问题，这些车辆可以在海洋中自主运行三年或更长时间，因为它们在数百公里的水流中漂移。 我们将用传感器装备十个浮子，以测量氧气和氮气，这些气体将放置在整个墨西哥西部的太平洋耗氧区域。 这是海洋中最大的此类地区，我们从该原型浮动的原型效果两年，从而证实了我们的方法。 这项研究很可能会通过对海洋对氮循环的预测更大的信心以及在当前和未来条件下修复二氧化碳的能力的预测，从而改变我们对海洋反硝化的理解，并最终使社会成为整体上的社会。 使用市售技术的应用和进一步开发浮动系统将直接受益于继任研究，并更广泛地展示使用辅助平台来解决困难的海洋学问题。这项研究的进步预计将延续到包括海洋生物地球化学建模在内的其他学科。 宣传活动，对早期职业科学家的支持以及学生培训包括在该项目中。 对于外展活动，调查人员计划将在马萨诸塞州提供代表性不足的人口不足的课后计划与公众介绍的机会联系在一起，并在华盛顿大学使用相关的展示材料为公众演讲提供了机会。 氧不足区域（ODZ）尽管构成了一小部分总海洋量，但在调节全球海洋碳和氮气周期中起着重要作用，包括托管固定氮损失的30％至50％。不幸的是，ODZ氮损失的当前不确定性源于速率的实质性和空间变异性，这些速率的速率差异不足，而这些变化仍然不足。虽然氧气和有机物的可用性对氮损失的局部调节是公认的，但氮通量的时间/空间变异性可能是物理强迫的影响，例如远程通风，季节性变异性和中尺度涡流的影响。了解物理强迫对通过氧气和有机通量介导的氮损失的影响如何充分了解任何未来ODZ扩张的原因和后果。为了提高我们对ODZ氮损失的理解，我们将执行一个基于自主浮点的观察计划，以解决有关ODZ中有关生物利用氮损失的出色问题。 作为我们飞行员部署的最大的ODZ和地区，我们的运营区将是东部热带N. Pacific（ETNP），我们的研究将在多年期间确定在多年内，位于氧气和表面生产率中的浮动地理位置梯度上的浮力梯度上的原位NM NM级别的氧和生物氮。我们的研究还将首次确定1至2周的拉格朗日浮子在恒定密度表面漂移1至2周的氮浓度的变化。 ETNP中2年浮动部署的飞行员记录了我们这样做的能力。至关重要的是，与先前的工作相比，我们基于浮点的方法更加紧密地与生物氮产生的预期变异性的频率和分布相匹配，并且将通过获得500个氮的含量/1000个奖励，这表明NSF的构建元素是通过deem deem deem deem deem deem dee eytiqual ofertional offiles and dee emportial of dee emportial of dee emportial of dee emportial。更广泛的影响审查标准。