Collaborative Proposal: Assessment of the Colloidal Iron Size Spectrum in Coastal and Oceanic Waters

生物可利用铁可以说是影响海洋初级生产力的分布和组成，进而影响海洋碳输出量的最重要的营养物质。铁以多种形式存在于世界各地的海洋中，胶体或不溶性相构成了溶解铁的重要部分。然而，目前对这些相的尺寸和物理/化学性质知之甚少。为了更好地了解铁循环的这一关键部分，研究人员将使用新的分析化学方法来定量分离样品中存在的胶体铁大小，并测量陆架和海洋沃茨中这些胶体部分的组成。这项研究的结果将有助于完善未来的研究，以更好地将海洋环境中铁的来源和命运联系起来。一名博士后研究员将担任该项目的首席研究员，提供独特的专业发展机会。此外，该项目每年将支持一名本科生的教育和研究培训，研究人员将对K-12学生和教师开展外展活动。铁的胶体相可能是储存铁的生物来源，是将铁剥离成沉降颗粒物的主要运输工具（将其从远洋生物圈中移除），或者更可能的是，这些作用的动态平衡随着铁输入的来源和特征而波动。目前调查海洋胶体物质的方法涉及使用单一截止滤波器操作性地定义本体胶体相，这是基于很少或没有证据的实际决定。更有问题的是，这些方法使胶体相均匀化，模糊了几乎可以肯定是与其大小和组成特征相关的胶体物质的反应谱。在这项研究中，研究人员将使用流场-流分馏耦合多角度激光散射来测量胶体尺寸谱的均匀性或唯一性，以及这些相的物理/化学特性。这些发现将对海洋生态学和海洋地球化学领域产生广泛的影响，并最终对海洋-大气耦合和气候变化的模拟研究产生影响。

Bioavailable iron is arguably the most important nutrient for shaping the distribution and composition of marine primary productivity and, in turn, the magnitude of ocean carbon export. Iron exists in many phases throughout the world's oceans, and colloidal, or non-soluble, phases comprise a significant fraction of dissolved iron. However, the size and physical/chemical character of these phases is presently poorly understood. To better understand this key part of iron cycling, researchers will use new analytical chemistry methods to quantitatively separate the colloidal iron sizes present in a sample and measure the composition of these colloidal portions in shelf and oceanic waters. Results from this study will help hone future studies to better link the source and fate of iron in the marine environment. A postdoctoral researcher will serve as a principal investigator on the project, providing a unique professional development opportunity. In addition, the project will support the education and research training of one undergraduate student each year, and the researchers will conduct outreach activities to K-12 students and teachers.The colloidal phase of iron may serve as a biological source of stored iron, a primary conveyance for stripping iron into sinking particulate matter (removing it from the pelagic biosphere), or, more likely, a dynamic balance of these roles that fluctuates with the source and character of iron input. The current methods to investigate marine colloidal matter involve operationally defining the bulk colloidal phase using single cutoff filters, a practical decision based on little or no evidence. More problematic, these methods homogenize the colloidal phase, obscuring what almost certainly is a reactivity spectrum of colloidal species tied to their size and compositional character. In this study, the researchers will use Flow Field-Flow Fractionation coupled to Multi-Angle Laser Light Scattering to make measurements of the uniformity or uniqueness of the colloidal size spectrum, and the physical/chemical character of these phases. The findings will have broad implications to the fields of marine ecology and biogeochemistry and, ultimately, to modeling studies of ocean-atmospheric coupling and climate change.