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与浮游植物的结合以及调节这一过程的化学、生物和生物化学机制，对于我们理解海洋的生态地球化学功能至关重要。这些微量元素（TE）有可能控制海洋生产力，生态系统结构和全球海洋大区域的常量营养素的利用。大量的努力已经花费在研究细胞微量元素配额的反应，在实验室培养的环境条件下，但测量的细胞微量元素的配额和化学计量在天然生物颗粒材料是罕见的，迫切需要约束和评估生物地球化学模型。国际GEOTRACES计划的发起是为了提高我们对全球海洋中微量元素的浓度和物理化学形态的认识。在这一项目中，毕格罗海洋科学实验室的研究人员将采用大量和微量元素分析技术相结合的方法，测量大西洋表层沃茨中各个浮游植物功能群和各种海洋地球化学梯度的大量颗粒物质中的铝、硅、磷、锰、铁、钴、镍、铜、锌和镉含量。在GEOTRACES北大西洋调查段航行期间，将使用GoFlo瓶、现场泵送和拖曳“鱼”相结合的方法，从表层混合层和深层叶绿素最大层采集样本。代表主要功能群（硅藻、自养鞭毛虫、蓝藻、颗石藻）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。将消化在0.45-μ m聚醚砜膜上收集的不溶性微粒，并采用高分辨率电感耦合等离子体质谱法（ICP-MS）进行分析。以这种方式，浮游植物微量元素组成的自然梯度溶解和颗粒的宏量和微量营养素供应的反应可以解决。此外，将采用三种常用方法更好地表征散装颗粒物质（草酸盐/EDTA冲洗、弱乙酸消化、用TE：Al比校正成石物质），并通过与细胞微量元素的直接SXRF测量进行比较来评价其有效性。硅藻及其硅藻壳的单细胞分析将能够评估锌和镍作为潜在的古海洋学代理，以及确定大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类群依赖偏好，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坚定地致力于为高中和本科生提供研究经验和指导，以及通过在当地组织（例如，图书馆、教堂、民间团体）以及毕格罗的科学咖啡馆项目。

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.