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

德雷克海峡的沙克尔顿断裂带（SFZ）是浮游植物低潮和高潮的分界线。在德雷克海峡以西、极锋以南和南极大陆架以北的南大洋水域，卫星得出的地表叶绿素浓度非常低。叶绿素和中尺度涡旋动能在SFZ以东高于ridge以西。作为国家海洋渔业局南极海洋生物资源计划的一部分，对该地区进行了为期10年的实地调查，证实了该地区存在强烈的水文和叶绿素梯度。一个跨学科的科学家团队假设，水深测量，包括2000米深的SFZ，影响中尺度环流和铁的运输，导致观察到的浮游植物模式。为了解决这一假设，该团队建议检查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，从病毒到浮游动物，铁，锰和铝的浓度和分布，以及SFZ附近的中尺度流动模式。铁浓度和浮游植物特性之间的关系将在微量营养物质中尺度运输的背景下进行研究，以确定观察到的浮游植物生物量变化有多少可归因于铁供应，并确定德雷克海峡以东远洋水域最重要的铁来源。目的是更好地了解南大洋浮游生物生产力和群落结构如何受到水深、中尺度环流和限制性营养分布之间耦合的影响。该研究计划包括对化学物质、浮游生物和水文特性的快速地表调查，并辅以垂直剖面的中尺度站网格、水采样和瓶培养富集实验。锰和铝的分布将被确定，以帮助区分风成、大陆架和上升流的铁来源。浮游植物的生理状态将通过对铁限制效应敏感的主动荧光方法进行监测。色素、碳和氮的质量浓度将通过过滤样品的分析、流式细胞术的细胞大小分布和显微镜的物种鉴定来获得。初级生产和光合作用参数（吸收、量子产率、可变荧光）将在深度剖面、地表调查和富集实验的大量样品上测量。将检查病毒和细菌的丰度，并评估细菌的生产是否受到铁或有机碳来源的限制。所提出的工作将提高我们对控制铁分布的过程和浮游生物群落在南大洋的反应的理解。该提案还包括一个外联部分，包括本科生研究经历（REU），教师体验南极和北极（TEA），以及基于该项目创建一个教育网站和K-12课程模块。

The Shackleton Fracture Zone (SFZ) in the Drake Passage defines a boundary between low and high phytoplankton waters. West of Drake Passage, Southern Ocean waters south of the Polar Front and north of the Antarctic continent shelf have very low satellite-derived surface chlorophyll concentrations. Chlorophyll and mesoscale eddy kinetic energy are higher east of SFZ compared to values west of the ridge. In situ data from a 10-year survey of the region as part of the National Marine Fisheries Service's Antarctic Marine Living Resources program confirm the existence of a strong hydrographic and chlorophyll gradient in the region. An interdisciplinary team of scientists hypothesizes that bathymetry, including the 2000 m deep SFZ, influences mesoscale circulation and transport of iron leading to the observed phytoplankton patterns. To address thishypothesis, the team proposes to examine phytoplankton and bacterial physiological states (including responses to iron enrichment) and structure of the plankton communities from virus to zooplankton, the concentration and distribution of Fe, Mn, and Al, and mesoscale flow patterns near the SFZ. Relationships between iron concentrations and phytoplankton characteristics will be examined in the context of the mesoscale transport of trace nutrients to determine how much of the observed variability in phytoplankton biomass can be attributed to iron supply, and to determine the most important sources of iron to pelagic waters east of the Drake Passage. The goal is to better understand how plankton productivity and community structure in the Southern Ocean are affected by the coupling between bathymetry, mesoscale circulation, and limiting nutrient distributions.The research program includes rapid surface surveys of chemical, plankton, and hydrographic properties complemented by a mesoscale station grid for vertical profiles, water sampling, and bottle incubation enrichment experiments. Distributions of manganese and aluminum will be determined to help distinguish aeolian, continental shelf and upwelling sources of iron. The physiological state of the phytoplankton will be monitored by active fluorescence methods sensitive to the effects of iron limitation. Mass concentrations of pigment, carbon and nitrogen will be obtained by analysis of filtered samples, cell size distributions by flow cytometry, and species identification by microscopy. Primary production and photosynthesis parameters (absorption, quantum yields, variable fluorescence) will be measured on depth profiles, during surface surveys and on bulk samples from enrichment experiments. Viruses and bacteria will be examined for abundances, and bacterial production will be assessed in terms of whether it is limited by either iron or organic carbon sources. The proposed work will improve our understanding of processes controlling distributions of iron and the response of plankton communities in the Southern Ocean. This proposal also includes an outreach component comprised of Research Experiences for Undergraduates (REU), Teachers Experiencing the Antarctic and Arctic (TEA), and the creation of an educational website and K-12 curricular modules based on the project.