Collaborative Research: Iron Incorporation into Biogenic Silica

过去几十年的海洋研究日益显示出铁化学在海洋生物过程中的重要作用。在某些缺铁的海洋区域，铁可能会限制生物生长，尽管氮和磷等其他基本营养物质很丰富。因此，为了充分了解和量化海洋中的生物生产力，全面了解铁的所有来源和汇是至关重要的。为该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，这些数据表明了一条潜在的大而未量化的除铁途径。硅藻，即贝壳由二氧化硅制成的浮游植物，被证明在贝壳中加入了微量的铁，使其无法快速回收或供表层水域的海洋生物使用。鉴于海洋中许多地方都有大量的硅藻，这可能代表着一种主要的、未被研究的去除机制，它调节了海水中铁的浓度。这项研究可能会改变目前对如何从海洋中去除铁的理解，并将影响对海水中涉及铁的化学和生物过程的理解。调查员还计划在K-12学校为地球科学教师提供教育课程，并将支持研究生在高级化学分析和海洋学方面的培训。基于同步加速器的高分辨率化学技术将能够确定硅藻小锥体中结合的铁的浓度和氧化状态。这一分析进展创造了独特评估生物源二氧化硅中铁的固存作为从海洋中除铁的主要途径的能力。在上一次CLIVAR实地考察中收集了南大洋太平洋部分的样品，其中一部分样品可用于用近边X射线荧光光谱仪对铁(Fe)进行新的同步加速器分析和亚微米尺度X射线荧光测绘，以及各种其他化学特征。利用这些方法，该项目将确定生物成因二氧化硅中的铁作为海洋铁循环中一种新的、未量化的损失项的重要性，并研究二氧化硅颗粒在水柱中垂直输送过程中铁的化学络合物的变化。

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.