Collaborative Research: Iron Incorporation into Biogenic Silica

近几十年来的海洋研究日益表明铁化学在海洋生物过程中的重要作用。在海洋的某些地区，铁是稀缺的，它可以限制生物生长，即使其他必需的营养物质，如氮和磷是丰富的。因此，要充分了解和量化海洋中的生物生产力，就必须全面了解铁的所有来源和汇。为这个项目提供资金的研究人员已经产生了令人兴奋的初步数据，表明了一个潜在的巨大的，但尚未量化的除铁途径。硅藻是一种由二氧化硅制成外壳的浮游植物，它们的外壳中含有微量的铁，这使得铁无法快速回收，也无法被地表水中的海洋生物利用。考虑到海洋中许多地方都有大量的硅藻，这可能代表了一种主要的、未经研究的去除机制，它调节了海水中铁的浓度。这项研究可能会改变目前对铁是如何从海洋中去除的理解，它将影响对海水中涉及铁的化学和生物过程的理解。该研究人员还计划通过为地球科学教师提供教育课程，在K-12学校进行推广，并将支持高级化学分析和海洋学方面的研究生培训。基于同步加速器的高分辨率化学技术将允许测定硅藻体内铁结合的浓度和氧化状态。这种分析上的进步创造了一种独特的评估能力，可以将铁封存到生物二氧化硅中，作为从海洋中去除铁的主要途径。在之前的CLIVAR现场活动中收集了来自南大洋太平洋部分的样品，其中的一部分可用于使用近边缘x射线荧光光谱（Fe- nexfs）和亚微米尺度x射线荧光制图进行铁（Fe）的新同步加速器分析，以及各种其他化学表征。通过这些方法，该项目将确定铁作为海洋铁循环中一个新的、不可量化的损失项被封存在生物二氧化硅中的重要性，并研究二氧化硅颗粒通过水柱垂直运输过程中铁的化学配合物的变化。

Ocean research over the last several decades has increasingly shown the great importance of iron chemistry on marine biological processes. In certain areas of the ocean where iron is scarce, it can limit biological growth even though other essential nutrients like nitrogen and phosphorus are abundant. Consequently, to fully understand and quantify biological productivity in the ocean, a complete knowledge of all sources and sinks for iron is essential. The researchers funded for this project have already generated exciting preliminary data that suggest a potentially large, yet, unquantified pathway for iron removal. Diatoms, phytoplankton with shells made of silica, are shown to incorporate traces of iron into their shells, making it unavailable for rapid recycling or use by marine organisms in surface waters. Given the great abundance of diatoms in many parts of the ocean, this could represent a major, unstudied removal mechanism that regulates the concentration of iron in seawater. This research could transform current understanding of how iron is removed from the ocean, and it will impact understanding of both the chemical and biological processes involving iron in seawater. The investigator also plans outreach in K-12 schools by providing educational courses for Earth Science teachers and will support graduate student training in advanced chemical analysis and oceanography. High-resolution synchrotron-based chemical techniques will allow determination of the concentration and oxidation state of iron bound within diatom frustules. This analytical advance has created the ability for unique evaluation of iron sequestration into biogenic silica as a major pathway for iron removal from the ocean. Samples from the Pacific sector of the Southern Ocean have been collected in a previous CLIVAR field campaign and a subset of these are available for new synchrotron analysis of iron (Fe) with Near Edge X-ray Fluorescence Spectroscopy (Fe-NEXFS) and submicron scale X-ray fluorescence mapping, as well as a variety of other chemical characterizations. With these methods, the project will determine the importance of iron sequestered into biogenic silica as a new and unquantified loss term in the oceanic Fe cycle and examine the changing chemical complexes of iron during vertical transport of silica particles through the water column.