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

南大洋德雷克海峡的沙克尔顿断裂带（SFZ）划定了浮游植物低潮和高潮的分界线。低叶绿素水流经南德雷克海峡，在东部以高叶绿素水出现，最近的证据表明，南南极环极流锋（SACCF）被引导到SFZ以南的南极半岛大陆架上，在那里发生了两种水类型的混合。然后将混合水与铁和浮游植物生物量一起平流。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施肥的反应的理解，以及这些过程如何影响有机碳向海洋内部的输出。假设该地区的水深测量影响中尺度环流和铁的运输，导致浮游植物生物量的观测模式。进一步假设南极环极流（ACC）的位置会影响ACC水流入半岛大陆架的大小，从而调节进入斯科舍海的铁量。为了解决这些假设，将在SFZ附近和南斯科舍海以东进行一次研究巡航。一个用于垂直剖面、水样和瓶培养富集实验的中尺度站网格将补充化学、浮游生物和水文特性的快速地表调查。将测定锰、铝和镭同位素的分布，以追踪铁的来源和估计混合率。浮游植物和细菌的生理状态（包括对铁富集的反应）和浮游生物群落的结构将被研究。主要目的是更好地了解南大洋浮游生物的生产力、群落结构和出口产量如何受到水深、中尺度环流和限制性营养物分布之间耦合的影响。提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，为了预测气候变率的影响，有必要进一步了解调节当前生态系统结构的条件。该项目将促进广泛群体的培训和学习。基金包括支持博士后、研究生和本科生。此外，该项目将为极地科学站网站的内容开发做出贡献，该网站自2001年以来一直是成人教育、家庭教育、部落学校、矫正教育、家庭扫盲计划和一般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.