Collaborative Research: Rhizosolenia Mats as a Source of Nitrogen Flux into the Surface Waters of the Pacific Ocean: Fe Stress, NE Excretion and Basin Scale Distribution Patterns

合作研究：丝状菌席作为进入太平洋表层水域的氮通量的来源：铁胁迫、N排泄和流域规模分布模式该项目将通过垂直迁移丝状菌席来量化真光层中的氮循环动态，并将提供关于潜水员可接近深度以下垫层的首次生理数据。这些宏观的硅藻组合下沉到真光区以下，获得硝酸盐，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上的，而不是物理上中介的N的运输。这些脆弱的协会需要专门的收集技术，如潜水和远程操作车辆(ROV)。因此，它们在生物学和生物地球化学方面的重要性在很大程度上被忽视了。其他分类群也垂直迁移，该项目将对整个群落进行首次列举，以了解垂直迁移在海洋氮循环中的更广泛作用。将使用现场视频成像技术对太平洋环流中东部的垫子进行量化。将使用深度特定采样(MOCNESS)来量化剩余的分类群。水下机器人将被用来收集潜水员可到达的深度下的垫子，以便将深垫子与水面垫子进行比较。现有的计算机模型将用这些订正估计数来计算运输/流量。在铁和/或光胁迫下，根霉除了运输氮素外，还可以分泌无机氮和有机氮。这将使用实验室和田间丝核菌进行评估。根据以前的结果，自然界中的海洋根霉似乎是慢性铁胁迫的。然而，铁氧还蛋白可能不会在这些海洋类群中产生，因此可能不是表征远洋根霉中铁胁迫的有效手段。作为我们研究的一部分，我们将评估从太平洋分离的丝核菌的铁胁迫指标。我们的目标是评估根状硅藻的铁配额，证明铁氧还蛋白指数作为大型海洋硅藻铁胁迫的衡量标准的有效性，并通过这些分类群确定氮的排泄率。迁徙模型将通过检查深垫子进行严格测试。这些数据将进一步深入了解微量营养限制与大量营养素的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。将评估整个迁徙社区对北太平洋中部环流东半部生物氮的输入和释放速率。这是理解海洋N循环的基础，并与上层海洋的碳循环和氮循环有直接关系。

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.