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，来自纽约市立大学皇后学院，罗得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生态系统过程的假设，这些假设将浮游生物群落结构的变化与颗粒生产，出口和POC-Po 210-Th 234相互作用联系在一起。他们将使用现场和实验室研究，以及地球化学（Po 210，Th 234示踪剂）和生物（初级生产，沉积物捕集器，浮游生物群落结构）技术的组合，这将导致对这些重要而复杂的上层海洋过程的更好理解，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）。一个重要的重点将是天然放射性核素Po 210，它在海洋环境中具有生物累积性，最近的研究表明，它有希望作为碳输出的示踪剂。这项研究的目的是完善我们的理解的机制，控制出口通量的Po 210，Th 234，和POC从上层水柱的变化，而不是使用这些放射性核素的不平衡，专门估计POC的出口通量。具体而言，该团队将调查POC，Po 210，210 Pb和Th 234与现场沉降颗粒的特定类型和粒度级之间的关系，然后使用受控实验室研究来测试假设并解释现场数据。这将提高我们的理解，并提供一个有价值的比较Po 210和Th 234作为粒子示踪剂。本研究的指导是以下两个关键问题：1）如何变量是POC，PO 210，和Th 234之间的悬浮和沉降颗粒和溶解池的分配响应于透光层浮游生物群落的季节性变化？2)在低通量和高通量条件下，POC，Po 210和Th 234的动员和分解率如何随表层海洋中浮游生物群落产生的材料的包装和出口而变化？实地工作将在Papa海洋站（OSP）时间序列站点进行，在低通量和高通量季节，出口主要是由Salps（2月），桡足类（5月）和植物碎屑（8月）。这个经过充分研究的高营养/低叶绿素站点提供了丰富的必要支持数据和后勤基础设施。这项提议最令人兴奋的成果之一将是实验和现场演示的强烈和一致的关系之间的反硝化食物网和C，Po 210，和Th 234包装，下沉和反硝化率。本研究将阐明真光层生态系统过程在预测中层输出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使用放射性核素示踪剂的信息，包括使用哪种示踪剂的机械理由，何时何地使用每种示踪剂，以及对颗粒C部分Po 210和Th 234进行跟踪的见解。更广泛的影响：该项目与几个国家和国际研究计划有关。这些措施包括：GEOTRACES，其重点是海水中微量元素和同位素的全球海洋分布; IMBER，其重点是海洋生态系统的运作。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。参与机构将提供研究生和/或本科生参与研究的各个方面。

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.