Collaborative Research: Determining the Elemental Composition of Natural Plankton Cells in the Eastern Equatorial Pacific using Synchrotron X-Ray Fluorescence Microscopy

纽约州立大学石溪分校、南卡罗来纳大学和俄勒冈州立大学的研究人员将使用基于同步加速器的x射线荧光显微镜（SXRF）——一种细胞特异性分析技术，来测量硅、磷、硫、铁、锰、镍和锌的元素浓度。结合野外采集的生物、化学和物理数据，研究结果将用于确定以下内容：(1)在东赤道太平洋（EEP）巡航期间，野外采集的植物和原生浮游动物的元素化学计量学如何沿着铁供应梯度变化；(2)实验室培养和船上操作对EEP完整浮游生物群落铁供应的化学计量学响应。EEP微型浮游生物的铁：碳吸收比率将使用放射性同位素测量。综合起来，这些信息将允许将细胞元素化学计量学与细胞铁配额和生长速率联系起来的假设得到解决。pi还将评估能够摄取富含铁的微浮游生物的细胞是否比必须直接从溶解相中获取铁的细胞更能维持较高的细胞铁。将确定有压细胞和鞭毛细胞元素组成的差异，并确定原生动物作为沿铁供应梯度的再生铁来源的重要性。结果将纳入耦合物理-生物地球化学模型参数化，用于EEP。就更广泛的影响而言，pi将确保向海洋科学界其他感兴趣的用户提供SXRF技术。为此，他们还计划建立和测试样品制备协议，并开发用户友好的定量软件，以增加样品产量。作为该项目的一部分，将培训两名研究生。本科生和高中生将通过REU项目与石溪大学环境分子科学中心合作参与研究。预计将为当地高中制作讨论本研究结果的互动教育节目，并为教师培训讲习班做出贡献。

Researchers at the State University of New York-Stony Brook, the University of South Carolina, and Oregon State University will use synchrotron based x-ray fluorescence microscopy (SXRF), a cell-specific analytical technique, to measure elemental concentrations of silicon, phosphorus, sulfur, iron, manganese, nickel and zinc. Along with biological, chemical, and physical data collected in the field, results will be used to determine the following: (1) how the elemental stoichiometries of field collected phyto- and protozooplankton change along gradients of iron supply during a cruise through the eastern equatorial Pacific (EEP); and (2) the stoichiometric responses to iron supply in laboratory cultures and in shipboard manipulations of intact plankton communities from the EEP. The iron:carbon uptake ratios in EEP picoplankton will be measured using radioisotopes. Combined, this information will allow the hypotheses that link cellular elemental stoichiometries to cellular iron quotas and growth rates to be addressed. The PIs also will evaluate if cells that can ingest iron-rich picoplankton are better able to maintain higher cellular iron than cells which must acquire iron directly from the dissolved phase. Differences between the elemental compositions of ballasted and flagellated cells will be determined and the importance of protozoa as a source of recycled iron along gradients in iron supply will also be ascertained. Results will be incorporated into coupled physical-biogeochemical models parameterized for use in the EEP.In terms of broader impacts, the PIs will ensure that the SXRF technique is made available to other interested users in the ocean sciences community. To this end, they also plan to establish and test protocols for sample preparation and develop user-friendly quantification software to increase sample output. Two graduate students will be trained as part of this project. Undergraduate students and high school student will be involved in the research via the REU program in association with Stony Brook's Center of Environmental Molecular Science. It is anticipated that interactive educational programs discussing results from this study will be produced for local high schools and contribute to a teacher training workshop.