Collaborative Research: Plankton Community Structure and Iron Distribution in the Southern Drake Passage and Scotia Sea

南大洋德雷克航道的沙克尔顿断裂带(SFZ)界定了低浮游植物水域和高浮游植物水域之间的边界。通过德雷克海峡南部的低叶绿素水向东表现为高叶绿素水，最近的证据表明，南极绕极洋流锋(SACCF)被引导到SFZ以南的南极半岛陆架上，在那里发生了水类型的混合。然后，随着铁和浮游植物生物量的增加，混合水被平流到场外。因此，SFZ是一个理想的自然实验室，可以提高对浮游生物群落对天然铁肥的反应的了解，以及这些过程如何影响有机碳向海洋内陆的输出。该地区的水深测量假设会影响中尺度环流和铁的运输，从而导致观察到的浮游植物生物量的模式。南极绕极流(ACC)的位置进一步被假设为影响ACC水流入半岛陆架的大小，从而调节进入斯科舍海的铁量。为了解决这些假设，将在SFZ附近和向东的斯科舍海南部进行一次研究巡航。用于垂直剖面、水样和瓶子培养浓缩实验的中尺度站网将补充对化学、浮游生物和水文特性的快速表面调查。将确定锰、铝和镭同位素的分布，以追踪铁的来源并估计混合速度。将研究浮游植物和细菌的生理状态(包括对富铁的反应)和浮游生物群落的结构。主要目标是更好地了解南大洋浮游生物生产力、群落结构和出口产量如何受到水深测量、中尺度环流和限制营养物质分布之间的耦合的影响。拟议的工作代表了一种跨学科的方法，以解决导致在SFZ附近发生的Chl-a突然转变的基本物理、化学和生物过程。鉴于最近有迹象表明南大洋正在变暖，重要的是促进对调节目前生态系统结构的条件的了解，以便预测气候变化的影响。该项目将在广泛的群体中促进培训和学习。包括资助博士后、研究生和本科生的资金。此外，该项目将有助于极地科学站网站内容的开发，该网站自2001年以来一直是成人教育、家庭教育、部落学校、惩教教育、家庭扫盲方案和普通公众的教师和学生的资源。

The Shackleton Fracture Zone (SFZ) in Drake Passage of the Southern Ocean defines a boundary between low and high phytoplankton waters. Low chlorophyll water flowing through the southern Drake Passage emerges as high chlorophyll water to the east, and recent evidence indicates that the Southern Antarctic Circumpolar Current Front (SACCF) is steered south of the SFZ onto the Antarctic Peninsula shelf where mixing between the water types occurs. The mixed water is then advected off-shelf with elevated iron and phytoplankton biomass. The SFZ is therefore an ideal natural laboratory to improve the understanding of plankton community responses to natural iron fertilization, and how these processes influence export of organic carbon to the ocean interior. The bathymetry of the region is hypothesized to influence mesoscale circulation and transport of iron, leading to the observed patterns in phytoplankton biomass. The position of the Antarctic Circumpolar Current (ACC) is further hypothesized to influence the magnitude of the flow of ACC water onto the peninsula shelf, mediating the amount of iron transported into the Scotia Sea. To address these hypotheses, a research cruise will be conducted near the SFZ and to the east in the southern Scotia Sea. A mesoscale station grid for vertical profiles, water sampling, and bottle incubation enrichment experiments will complement rapid surface surveys of chemical, plankton, and hydrographic properties. Distributions of manganese, aluminum and radium isotopes will be determined to trace iron sources and estimate mixing rates. Phytoplankton and bacterial physiological states (including responses to iron enrichment) and the structure of the plankton communities will be studied. The primary goal is to better understand how plankton productivity, community structure and export production in the Southern Ocean are affected by the coupling between bathymetry, mesoscale circulation, and distributions of limiting nutrients. The proposed work represents an interdisciplinary approach to address the fundamental physical, chemical and biological processes that contribute to the abrupt transition in chl-a which occurs near the SFZ. Given recent indications that the Southern Ocean is warming, it is important to advance the understanding of conditions that regulate the present ecosystem structure in order to predict the effects of climate variability. This project will promote training and learning across a broad spectrum of groups. Funds are included to support postdocs, graduate students, and undergraduates. In addition, this project will contribute to the development of content for the Polar Science Station website, which has been a resource since 2001 for instructors and students in adult education, home schooling, tribal schools, corrections education, family literacy programs, and the general public.