Collaborative Research: Iron Incorporation into Biogenic Silica

在过去的几十年里，海洋研究越来越多地表明铁化学对海洋生物过程的重要性。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的生物生产力，必须全面了解铁的所有来源和汇。资助该项目的研究人员已经产生了令人兴奋的初步数据，这些数据表明了一个潜在的大的，但尚未量化的铁去除途径。硅藻是一种浮游植物，其外壳由二氧化硅制成，其外壳中含有微量的铁，使其无法快速回收或被表层沃茨中的海洋生物使用。考虑到海洋许多地方硅藻的大量存在，这可能是一种主要的、未经研究的去除机制，可以调节海水中铁的浓度。这项研究可能会改变目前对铁如何从海洋中去除的理解，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学校开展外联活动，为地球科学教师提供教育课程，并将支持高级化学分析和海洋学方面的研究生培训。高分辨率的同步加速器为基础的化学技术将允许确定的浓度和氧化态的铁结合在硅藻细胞壳。这一分析进展创造了独特的评估能力，铁螯合到生物二氧化硅作为一个主要途径，从海洋中去除铁。来自南大洋太平洋部分的样本已在以前的气候变化和变应性研究实地活动中收集，其中一部分可用于新的同步加速器近边缘X射线荧光光谱分析（Fe-NEXFS）和亚微米尺度X射线荧光绘图，以及各种其他化学表征。通过这些方法，该项目将确定铁螯合到生物硅中的重要性，作为海洋铁循环中一个新的和未量化的损失术语，并检查二氧化硅颗粒通过水柱垂直运输过程中铁的化学复合物的变化。

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.