Collaborative Research: Testing Linkages Between Plankton Community Structure and Export of C, Po, and Th in the Sub-Arctic NE Pacific: Field and Lab Studies

在这个项目中，一个来自纽约州立大学皇后学院、罗德岛大学和百慕大海洋科学研究所的跨学科研究小组将调查并直接测试有关生态系统过程的假设，这些过程将浮游生物群落结构的变化与东北太平洋亚北极北部的颗粒产生、输出和POC-Po210-Th234相互作用联系起来。他们将利用实地和实验室研究，结合地球化学（Po210、Th234示踪剂）和生物（初级生产、沉积物捕集器、浮游生物群落结构）技术，提高对这些重要而复杂的上层海洋过程的理解，这些过程广泛适用于解释当前和最近的结果（例如VERTIGO、MEDFLUX、HOT、BATS）。一个重要的焦点将放在天然放射性核素Po210上，它在海洋环境中是生物积累的，最近的研究表明它有希望和用途作为碳输出的示踪剂。本研究旨在完善我们对上层水柱Po210、Th234和POC输出通量变异性控制机制的理解，而不是使用这些放射性核素不平衡来单独估计POC输出通量。具体而言，该团队将研究POC、Po210、210Pb和Th234与现场下沉颗粒的特定类型和大小分数之间的关系，然后使用受控实验室研究来验证假设并解释现场数据。这将提高我们的认识，并提供Po210和Th234作为粒子示踪剂的有价值的比较。本研究主要围绕以下两个关键问题展开：1)浮游生物群落中POC、Po210和Th234在悬浮和沉降颗粒与溶解池之间的分配随季节变化的变化程度如何？2)在低通量和高通量条件下，海洋表层浮游生物群落生产的物质的包装和输出对POC、Po210和Th234的动员和分解速率有何影响？实地工作将在Papa海洋站（OSP）时间序列站点进行，在低通量季节和高通量季节，出口主要是海带（2月），桡足类（5月）和植物碎屑（8月）。这个研究充分的高营养/低叶绿素站点提供了丰富的必要的支持数据和后勤基础设施。这一提议最令人兴奋的结果之一将是实验和实地证明浮游食物网与C、Po210和Th234的包装、下沉和再矿化速率之间强有力和一致的关系。本研究将阐明光带生态系统过程在预测中上层出口通量最终命运中的作用。该项目预计将产生可用于指导未来放射性核素示踪剂使用的信息，包括使用哪种示踪剂的机理论证，何时何地使用每种示踪剂，以及对Po210和Th234所追踪的颗粒C分数的深入了解。更广泛的影响：本项目与几个国家和国际研究项目相关。这些包括;GEOTRACES，主要研究海水中微量元素和同位素的全球海洋分布；以及专注于海洋生态系统功能的IMBER。它还将以OSP早期过程研究的结果为基础，包括SUPER（亚北极太平洋生态系统研究）、VERTEX（垂直交换）和加拿大JGOFS研究。参与机构将为研究生和/或本科生参与研究的各个方面提供条件。

In this project, an interdisciplinary research team from CUNY Queens College, University of Rhode Island and the Bermuda Institute of Ocean Sciences will investigate and directly test hypotheses on ecosystem processes that link variability in plankton community structure to particle production, export, and POC-Po210-Th234 interactions in the upper sub-arctic NE Pacific Ocean. They will use field and lab studies, and a combination of geochemical (Po210, Th234 tracers) and biological (primary production, sediment traps, plankton community structure) techniques that will lead to an improved understanding of these important and complex upper ocean processes, which have wide applicability to the interpretation of current and recent results (e.g., VERTIGO, MEDFLUX, HOT, BATS). An important focus will be on the natural radionuclide Po210, which is bioaccumulated in the marine environment, and which recent studies indicate has promise and utility as a tracer of carbon export. This study is designed to refine our understanding of the mechanisms that control variability in export fluxes of Po210, Th234, and POC from the upper water column, rather than using these radionuclide disequilibria to exclusively estimate POC export fluxes. Specifically the team will investigate the relationships between POC, Po210, 210Pb, and Th234 associated with specific types and size-fractions of sinking particles in the field, and then use controlled laboratory studies to test hypotheses and interpret the field data. This will improve our understanding and provide a valuable comparison of Po210 and Th234 as particle tracers. The research is guided by the following two key questions: 1) How variable is the partitioning of POC, Po210, and Th234 between suspended and settling particles and the dissolved pool in response to seasonal variability in the euphotic zone plankton community? 2) How do rates of mobilization and decomposition of POC, Po210, and Th234 vary with the packaging and export of materials produced by the planktonic community in the surface ocean under low and high flux conditions? Field work will be conducted at the Ocean Station Papa (OSP) time series site, during low and high flux seasons when export is dominated by salps (February), copepods (May), and phytodetritus (August). This well-studied high-nutrient/low-chlorophyll site provides a wealth of necessary supporting data and logistical infrastructure. One of the most exciting outcomes from this proposal would be an experimental and field demonstration of strong and consistent relationships between planktonic food webs and the rates of C, Po210, and Th234 packaging, sinking, and remineralization. This study will illuminate the role of euphotic zone ecosystem processes in predicting the eventual fate of export flux in the mesopelagic. The project is expected to yield information that could be used to guide future use of radionuclide tracers, including mechanistic justifications for which tracer to use, when and where to use each tracer, as well as insight into which particulate C fraction Po210 and Th234 are tracing. Broader Impacts: This project is relevant to several national and international research programs. These include; GEOTRACES, whose focus is the global-ocean distribution of trace elements and isotopes in seawater; and IMBER, whose focus in on the functioning of ocean ecosystems. It will also build upon the results of earlier process studies at OSP including SUPER (Subarctic Pacific Ecosystem Research), VERTEX (VERTical EXchange) and the Canadian JGOFS study. The participating institutions will make provision for graduate and/or undergraduate student involvement in all aspects of the research.