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)界定了低浮游植物水域和高浮游植物水域之间的边界。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的卫星获取的表面叶绿素浓度非常低。与脊线以西相比，SFZ以东的叶绿素和中尺度涡动动能较高。作为国家海洋渔业局南极海洋生物资源计划的一部分，对该地区进行的为期10年的调查的现场数据证实，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，会影响中尺度的循环和铁的运输，从而导致观察到的浮游植物模式。为了解决这一假设，该团队建议研究浮游植物和细菌的生理状态(包括对铁丰富的反应)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。将在微量营养物质的中尺度运输的背景下研究铁浓度与浮游植物特性之间的关系，以确定所观察到的浮游植物生物量的变化在多大程度上可归因于铁的供应，并确定德雷克海峡以东的中上层水域的最重要的铁来源。该研究的目标是更好地了解水深测量、中尺度环流和限制营养物质分布之间的耦合如何影响南大洋的浮游生物生产力和群落结构。该研究计划包括对化学物质、浮游生物和水文特性的快速表面调查，以及用于垂直剖面、水样和瓶子培养浓缩实验的中尺度站网。将确定锰和铝的分布，以帮助区分风成铁源、大陆架铁源和上升铁源。浮游植物的生理状态将通过对铁限制的影响敏感的主动荧光方法进行监测。通过对过滤后的样品进行分析，通过流式细胞仪分析细胞大小分布，通过显微镜鉴定物种，可以获得色素、碳和氮的质量浓度。初级生产力和光合作用参数(吸收、量子产量、可变荧光)将在深度剖面上、在地面调查期间和在浓缩实验的大样本上测量。将检查病毒和细菌的丰度，并根据细菌产量是否受到铁或有机碳源的限制来评估细菌产量。拟议的工作将提高我们对控制铁分布的过程和南大洋浮游生物群落的反应的理解。该提案还包括一个外展部分，包括本科生研究经历(REU)、南极和北极体验教师(TEA)，以及根据该项目创建一个教育网站和K-12课程单元。

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.