GEOTRACES Atlantic Section: Characterization of phytoplankton trace metal quotas and their contribution to the particulate metal pool in the upper ocean

微量元素Mn、Fe、Co、Ni、Cu和Zn进入浮游植物，以及调节这一过程的化学、生物和生化机制，对我们理解海洋的生物地球化学功能至关重要。这些微量元素（TE）具有控制海洋生产力、生态系统结构和全球海洋大片地区大量营养素利用的潜力。在实验室培养中，研究细胞微量元素配额对环境条件的响应已经花费了大量的努力，但是对天然生物颗粒材料中细胞微量元素配额和化学计量的测量很少，并且迫切需要约束和评估生物地球化学模型。发起国际GEOTRACES计划是为了提高我们对全球海洋中微量元素的浓度和物理和化学形态的认识。在这个项目中，毕格罗海洋科学实验室的研究人员将使用大量和微量分析元素技术相结合的方法，测量大西洋表层水生物地球化学梯度中单个浮游植物功能群和大块颗粒物的Al、Si、P、Mn、Fe、Co、Ni、Cu、Zn和Cd的含量。在GEOTRACES北大西洋调查部分巡航期间，将使用GoFlo瓶、原位泵送和拖曳“鱼”的组合从表层混合层和深层叶绿素最大层收集样本。代表主要功能群（硅藻、自养鞭毛虫、蓝藻、球石藻）的单个浮游植物细胞将用同步加速器x射线荧光分析（SXRF）进行分析。采用高分辨率电感耦合等离子体质谱法（ICP-MS）对0.45- Ìm聚醚砜膜上收集的颗粒物进行消化和分析。通过这种方式，可以解决浮游植物微量元素组成对自然梯度的响应，在溶解和颗粒的宏微量营养素供应。此外，将应用三种常用的方法来更好地表征大块颗粒物质（草酸/EDTA冲洗，弱乙酸消化，用TE:Al比校正岩石物质），并通过与直接SXRF测量细胞微量元素的比较来评估它们的有效性。硅藻及其小体的单细胞分析将有助于评估Zn和Ni作为潜在的古海洋学代用物，以及确定常量营养素和微量营养素之间的协同和拮抗关系，以及特定微量营养素的分类依赖偏好，解决几个核心GEOTRACES目标。更广泛的影响：这项研究的更广泛的影响包括为高中生和本科生提供研究经验和指导，以及通过在当地组织（如图书馆、教堂、公民团体）和毕格罗大学的cafede Scientifique项目向公众进行宣传。

Incorporation of the trace elements Mn, Fe, Co, Ni, Cu and Zn into phytoplankton, and the chemical, biological and biochemical mechanisms which regulate this process, are of central importance to our understanding of the biogeochemical functioning of the oceans. These trace elements (TE) have the potential to control ocean productivity, ecosystem structure and the utilization of macronutrients in large regions of the global ocean. Significant effort has been expended to study the response of cellular trace element quotas to environmental conditions in laboratory cultures, but measurements of cellular trace element quotas and stoichiometries in natural biogenic particulate material are rare and sorely needed to constrain and evaluate biogeochemical models. The international GEOTRACES program was initiated to advance our knowledge of the concentrations and physical and chemical speciation of trace elements in the global ocean. In this project, researchers at the Bigelow Laboratory for Ocean Sciences will measure the Al, Si, P, Mn, Fe, Co, Ni, Cu, Zn and Cd contents of individual phytoplankton function groups and bulk particulate matter across biogeochemical gradients in the surface waters of the Atlantic Ocean using a combination of bulk and microanalytical elemental techniques. Samples will be collected from the surface mixed layer and deep chlorophyll maximum layer during the GEOTRACES North Atlantic Survey Section cruise using a combination of GoFlo bottles, in situ pumping and a towed ¡®fish¡¯. Individual phytoplankton cells representing major functional groups (diatoms, autotrophic flagellates, cyanobacteria, coccolithophores) will be analyzed with synchrotron x-ray fluorescence analysis (SXRF). Particulate matter collected on 0.45-¦Ìm polyethersulfone membranes will be digested and analyzed with high resolution inductively coupled plasma mass spectrometry (ICP-MS). In this way, the response of phytoplankton trace element composition to natural gradients in dissolved and particulate macro- and micronutrient supply can be resolved. Additionally, three methods commonly used to better characterize bulk particulate matter (oxalate/EDTA rinse, weak acetic acid digestion, correction for lithogenic material with TE:Al ratios) will be applied and their effectiveness evaluated through comparisons with direct SXRF measurements of cellular trace elements. Single-cell analyses of diatoms and their frustules will enable evaluation of Zn and Ni as potential paleoceanographic proxies, as well as determination of synergistic and antagonistic relationships among macronutrients and micronutrients and taxa-dependent preferences for specific micronutrients, addressing several core GEOTRACES objectives. Broader Impacts: The broader impacts of this study include a strong commitment to providing research experiences and mentorship to high school and undergraduate students as well as outreach to the general public through presentations at local organizations (e.g., libraries, churches, civic groups) and via the Caf¨¦ Scientifique program at Bigelow.