Development of low Nitrogen:Phosphorus ratios in the euphotic zone - the Phosphorus side of the story

富光带中低氮磷比的发展——故事中磷的一面

• 批准号: 1737240
• 负责人: Andrew Juhl
• 金额: $ 141.76万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-01-01 至 2023-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1737240&HistoricalAwards=false
• 关键词: Development; low; Nitrogen; Phosphorus; ratios

This research will study the processes that cause the relative biological availability of nitrogen (N) and phosphorus (P) in the upper ocean to change as water moves from the coast to offshore in the northern Gulf of Mexico. Both N and P are required nutrients. Consequently, the ratio of N to P in the upper ocean has important consequences for plant growth and the marine food web structure. Typically, as water moves offshore bioavailable N declines faster than bioavailable P. While processes that alter either element will affect the N to P ratio, previous research has focused mainly on the N side of the relationship, examining cycling and the selective removal of different forms of N from the water by marine microorganisms. This project will focus instead on the less-studied P side of the N to P ratio in the upper ocean. It will use shipboard experiments to quantify microbiological processes that maintain P availability in the upper ocean, even as N availability declines. Given that low N availability relative to P limits plant growth in most of the ocean's sunlit surface waters, understanding how this chemical ratio develops as water moves offshore is of fundamental importance for the study of marine ecosystems worldwide. Educational impact will include at least seven students' direct participation in the research, providing hands-on and cross-disciplinary training, as well as practical experience at sea. Two middle school teachers will also participate in the oceanographic cruises. They will incorporate field results and personal experiences into lesson plans and teachers' workshops. The project will also develop public outreach activities that focus on the unique value of marine ecosystems of the Gulf of Mexico.This project will test the hypothesis that the decline in the ratio of bioavailable N to P in surface water as it moves offshore develops from preferential phosphorus retention as opposed to removal of biologically-available forms of nitrogen. As part of the research associated with this central hypothesis, the project will quantitatively compare the relative importance of different phosphorus-retention mechanisms during two oceanographic cruises in the northern Gulf of Mexico. Previous observations of spatial changes in N and P availability are common. The researchers will track discrete water masses with Lagrangian drifters for time course sampling, and use physical oceanographic measurements to quantify potential N to P ratio changes contributed by vertical and horizontal mixing. Shipboard incubation experiments will quantify and compare rates for the key microbiological processes thought to affect phosphorus retention in the upper ocean. This focus on potential P-retention processes rather than N loss as an explanation of commonly observed declines in surface ocean N to P ratio represents a unique contribution to the complete understanding of the complex feedback mechanisms between nutrient cycles and marine ecosystem function.

这项研究将研究导致氮（N）和磷（P）在上层海洋的相对生物有效性的变化，随着水从海岸到近海在墨西哥湾的北方的过程。N和P都是必需的营养素。 因此，海洋上层的氮磷比对植物生长和海洋食物网结构具有重要影响。通常情况下，随着水移动离岸生物可利用的N下降速度比生物可利用的P。虽然改变任一元素的过程会影响N与P的比例，以前的研究主要集中在N方面的关系，检查循环和选择性去除不同形式的N从水中的海洋微生物。该项目将侧重于海洋上层氮磷比中研究较少的磷方面。它将使用船上实验来量化微生物过程，即使在氮可用性下降的情况下，微生物过程也能维持上层海洋的磷可用性。鉴于相对于P的低N可用性限制了大多数海洋阳光照射的表面沃茨中的植物生长，因此了解这种化学比率如何随着水向近海移动而发展对于研究全球海洋生态系统具有根本重要性。教育影响将包括至少七名学生直接参与研究，提供实践和跨学科培训，以及海上实践经验。两名中学教师也将参加海洋考察。他们将把实地结果和个人经验纳入课程计划和教师讲习班。该项目还将开展以墨西哥湾海洋生态系统的独特价值为重点的公众宣传活动，该项目将检验一种假设，即地表水中生物可利用氮与磷的比例随着离岸移动而下降，这是由于优先保留磷而不是去除生物可利用形式的氮。 作为与这一中心假设有关的研究的一部分，该项目将在墨西哥湾北方进行的两次海洋学考察期间，对不同磷滞留机制的相对重要性进行定量比较。 以前的观察，在氮和磷的可用性的空间变化是常见的。 研究人员将使用拉格朗日漂流器跟踪离散水团进行时间过程采样，并使用物理海洋学测量来量化垂直和水平混合造成的潜在氮磷比变化。 船上培养实验将量化和比较被认为影响上层海洋磷滞留的关键微生物过程的速率。这种关注潜在的P-保留过程，而不是N的损失作为一种解释，通常观察到的海洋表面N-P比下降代表了一个独特的贡献，营养循环和海洋生态系统功能之间的复杂的反馈机制的完整理解。

项目成果

Iterative spatial leave-one-out cross-validation and gap-filling based data augmentation for supervised learning applications in marine remote sensing

• DOI: 10.1080/15481603.2022.2107113
• 发表时间: 2022-08
• 期刊: GIScience & Remote Sensing
• 影响因子: 6.7
• 作者: Andy Stock;A. Subramaniam

Quantifying Per-Cell Chlorophyll a in Natural Picophytoplankton Populations Using Fluorescence-Activated Cell Sorting

使用荧光激活细胞分选定量天然超微型浮游植物种群中的每细胞叶绿素 a

• DOI: 10.3389/fmars.2022.850646
• 发表时间: 2022
• 期刊: Frontiers in Marine Science
• 影响因子: 3.7
• 作者: Bock, Nicholas;Subramaniam, Ajit;Juhl, Andrew R.;Montoya, Joseph;Duhamel, Solange
• 通讯作者: Duhamel, Solange