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)，这是一种细胞特有的分析技术，来测量硅、磷、硫、铁、锰、镍和锌的元素浓度。结合实地收集的生物、化学和物理数据，结果将被用来确定以下内容：(1)实地采集的浮游植物和原生动物的基本化学计量学如何在穿越赤道东太平洋(EEP)期间随铁供应的梯度变化；以及(2)在实验室培养和来自EEP的完整浮游生物群落的船上操作中对铁供应的化学计量响应。将使用放射性同位素测量EEP微微浮游生物中铁和碳的摄取率。结合起来，这些信息将使将细胞元素化学计量与细胞铁配额和生长速度联系起来的假设得以解决。PI还将评估能够摄取富含铁的微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能够更好地保持更高的细胞铁含量。将确定压载细胞和鞭毛细胞的元素组成之间的差异，并将确定原生动物作为回收铁的来源在铁供应中的梯度的重要性。结果将被纳入耦合的物理-生物地球化学模型中，以便在EEP中使用。在更广泛的影响方面，PIS将确保向海洋科学界的其他感兴趣的用户提供SXRF技术。为此，他们还计划制定和测试样品制备方案，并开发用户友好的量化软件，以增加样品产量。作为该项目的一部分，两名研究生将接受培训。本科生和高中生将通过与石溪环境分子科学中心合作的REU计划参与这项研究。预计将为当地高中制作讨论这项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.