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

可以说，生物可利用铁是影响海洋初级生产力的分布和组成，进而决定海洋碳输出量的最重要的营养物质。铁存在于世界海洋的许多相中，胶体相或不溶相构成了溶解铁的很大一部分。然而，目前人们对这些相的大小和物理/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本中存在的胶体铁大小，并测量陆架和海洋水域中这些胶体部分的组成。这项研究的结果将有助于磨练未来的研究，以更好地联系海洋环境中铁的来源和命运。一名博士后研究员将担任该项目的首席研究员，提供一个独特的专业发展机会。此外，该项目将支持每年一名本科生的教育和研究培训，研究人员将向K-12学生和教师开展外展活动。铁的胶体相可以作为储存铁的生物来源，作为将铁剥离成下沉颗粒物(将其从远洋生物圈中清除)的主要运输工具，或者更有可能是这些角色的动态平衡，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包括使用单一截止滤光器在操作上确定大块胶体相，这是一个基于很少或根本没有证据的实际决定。更有问题的是，这些方法将胶体相均质化，几乎可以肯定的是，胶体物种的反应光谱与其大小和组成特征有关。在这项研究中，研究人员将使用流场-流动分离与多角度激光光散射相结合来测量胶体粒度光谱的一致性或唯一性，以及这些相的物理/化学性质。这些发现将对海洋生态学和生物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型研究产生影响。

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.