Collaborative Research: Rhizosolenia Mats as a Source of Nitrogen Flux into the Surface Waters of the Pacific Ocean: Fe stress, N excretion and basin-scale distribution patterns

合作研究：根扶桑菌垫作为进入太平洋表层水体的氮通量来源：铁应力、氮排泄和盆地尺度分布模式本项目将通过垂直迁移根扶桑菌垫来量化绿化带的氮循环动力学，并将提供潜水员可达深度以下的根扶桑菌垫的第一个生理数据。这些宏观的硅藻组合沉到光带以下获取硝酸盐，将其储存在液泡中，然后返回表面进行光合作用。这种新的生产完全基于生物，而不是物理介导的氮转运。这些脆弱的关联需要专门的收集技术，如水肺和远程操作车辆（rov）。因此，它们的生物学和生物地球化学重要性在很大程度上被忽视了。其他分类群也垂直迁移，本项目将对整个群落进行首次枚举，以了解垂直迁移在海洋氮循环中的更广泛作用。现场视频成像技术将用于量化北太平洋中东部环流中的垫。深度特定（MOCNESS）采样将用于量化剩余的分类群。ROV将用于收集潜水员可到达深度以下的垫层，以便将深层垫层与表层垫层进行比较。将使用现有的计算机模式，根据这些订正估计数计算输送/通量率。除运输氮外，在铁和/或光胁迫下根瘤菌垫还可以排泄无机氮和有机氮。这将使用实验室和现场根瘤菌进行评估。根据以往的研究结果，海洋根瘤菌垫在自然界中表现出长期的铁胁迫。然而，铁氧还蛋白（一种常见且方便的细胞铁状态原位标记物）可能在这些海洋分类群中不产生，因此可能不是表征开放海洋根管菌铁胁迫的有效手段。作为我们研究的一部分，我们将评估这一指标在太平洋分离的根管菌中的铁胁迫。我们的目标是评估根状螺杆状硅藻的铁配额，记录铁氧还蛋白指数作为大型海洋硅藻铁胁迫的有效性，并确定这些分类群的N排泄率。一个迁移模型将通过检查深垫得到严格的检验。这些数据将进一步深入了解微量营养素限制与宏量营养素获取和同化之间的协同关系，这是现代生物海洋学的一个重要发展主题。将评估整个迁徙群落对北太平洋中部环流东半部生物氮的进口和释放率。这是理解海洋氮循环的基础，并与上层海洋的碳和氮循环直接相关。

Collaborative research: Rhizosolenia mats as a source of nitrogen flux into the surface waters of the Pacific Ocean: Fe stress, N excretion and basin scale distribution patternsThis project will quantify nitrogen cycling dynamics in the euphotic zone by vertically migrating Rhizosolenia mats, and will provide the first physiological data on mats below diver accessible depths. These macroscopic diatom assemblages sink below the euphotic zone to acquire nitrate, store it in their vacuole, and then return to the surface for photosynthesis. This new production is based entirely on a biologically, rather than physically mediated transport of N. These fragile associations require specialized collection techniques such as SCUBA and remotely operated vehicles (ROVs). As a result, their biology and biogeochemical importance has been largely overlooked. Other taxa also vertically migrate, and this project will conduct the first enumeration of this entire community in order to understand the broader role of vertical migration in oceanic nitrogen cycling.In-situ video imaging techniques will be used to quantify mats in the eastern central N. Pacific gyre. Depth specific (MOCNESS) sampling will be used to quantify the remaining taxa. A ROV will be used to collect mats below diver accessible depths in order to compare deep mats with surface mats. An existing computer model will be used to calculate transport/flux rates with these revised estimates. In addition to transporting N, Rhizosolenia mats under Fe and/or light stress may excrete both inorganic and organic nitrogen. This will be evaluated using both laboratory and field Rhizosolenia. Based on previous results, oceanic Rhizosolenia mats in nature appear to be chronically Fe-stressed. However, ferredoxin, a common and convenient in situ marker of cellular Fe status, may not be produced in these oceanic taxa and thus may not be a valid means of characterizing Fe stress in open ocean Rhizosolenia. As part of our research, we will evaluate this indicator for Fe stress in Rhizosolenia isolated from the Pacific Ocean. Our goals are to assess the Fe quotas of rhizosolenid diatoms, document the validity of the ferredoxin index as a measure of Fe stress in large oceanic diatoms, and determine N excretion rates by these taxa. A migration model will be rigorously tested by examining deep mats. These data will provide additional insight into the synergistic relationship between trace nutrient limitation and macronutrient acquisition and assimilation, an important developing theme of modern biological oceanography. The rates of biological N import and release for the eastern half of the central N. Pacific gyre by the entire migrating community will be assessed. This is a fundamental to understanding oceanic N cycles, and has direct relevance for both carbon and nitrogen cycling in the upper ocean.