Collaborative Research: ETBC: Amazon iNfluence on the Atlantic: CarbOn export from Nitrogen fixation by DiAtom Symbioses (ANACONDAS)

合作研究：ETBC：亚马逊对大西洋的影响：DiAtom Symbioses 固氮产生的碳输出 (ANACONDAS)

• 批准号: 1133277
• 负责人: JOAQUIM GOES
• 金额: $ 19.47万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-02-01 至 2014-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1133277&HistoricalAwards=false
• 关键词: Collaborative; Research; ETBC; Amazon; iNfluence

The investigators hypothesize that large tropical river plumes with low N: P ratios provide an ideal niche for diatom-diazotroph assemblages (DDAs). They suggest that the ability of these organisms to fix N2 within the surface ocean is responsible for significant C export in the Amazon River plume. Their previous observations in the Amazon River plume helped reveal that blooms comprised of the endosymbiotic N2-fixing cyanobacterium Richelia and its diatom hosts (e.g. Hemiaulus) were a significant source of new production and carbon export. The previous work focused largely on the sensitivity of DDAs to external forcing from dust and riverine inputs, so the ecology of these organisms and the fate of their new production were largely unstudied. It is now known that DDAs are responsible for a significant amount of CO2 drawdown in the Amazon River plume, and floating sediment traps at 200 m measured 4x higher mass fluxes beneath the plume than outside the plume. This led the researchers to hypothesize that this greater export is due either to aggregation and sinking of DDAs themselves or to grazing of DDAs by zooplankton.In this study the researchers will undertake a suite of field, satellite and modeling studies aimed at understanding the ecology and tracing the fate of C and N fixed by DDAs and other phytoplankton living in the plume. By examining C and silicate (Si) export from offshore surface waters, through the upper oceanic food web, the mesopelagic, and down to the deep sea floor, they will quantify the impact of the Amazon River on biological processes that control C sequestration and the implications of these regional processes on C, N and Si budgets. The study will go beyond previous research because they will quantify 1) the distribution, nutrient demands, and activity of DDAs in the context of phytoplankton species succession, 2) the sensitivity of the CO2 drawdown to the mix of phytoplankton, 3) the grazing and aggregation processes contributing to the sinking flux, 4) the composition of this flux, and 5) the proportion of this material that reaches the seafloor. This effort truly represents a measure of C sequestration and pump efficiency. Ecological modeling will be used to place observational results from field studies and satellites into the context of the larger Atlantic basin with tropical climate variability on interannual and longer time scales.Intellectual Merit: The PIs have identified a potentially significant but poorly understood, ecosystem-controlled, climate-sensitive C sequestration pathway that seems to violate the expectation of an inefficient open-ocean biological pump. Since primary production fueled by allochthonous sources of N such as N2 fixation can drive a net, biologically mediated transfer of C from the atmosphere to the ocean, C sequestration by DDAs in the Amazon River plume is a regionally significant process. Because DDAs have been found in other tropical river systems, they may represent a globally significant, yet previously overlooked biological pump mechanism.Broader Impacts: The Amazon River has captured the public's imagination more than any other river. This study aims to take advantage of such high profile earth science to promote science literacy among all our citizens. This project will support graduate and postdoctoral education, undergraduates through training cruises, and ocean science education of K-12 teachers and undergraduates through the COSEE-West, the Mid Atlantic COSEE and the COSEEOS programs. The results of this research will be made available to other scientists through peer reviewed publications, public databases, and an ANACONDAS website, as well as to the general public through the SFSU RTC-Bay Area Discovery Museum Program.

研究人员假设，具有低氮磷比的大型热带河流羽流为硅藻-重氮营养盐组合（DDAs）提供了理想的生态位。他们认为，这些生物在海洋表面固定N2的能力是亚马逊河羽流中大量输出C的原因。他们之前对亚马逊河羽流的观察帮助揭示了由内共生的固氮蓝藻Richelia及其硅藻宿主（如Hemiaulus）组成的水华是新生产和碳输出的重要来源。以前的工作主要集中在DDAs对来自灰尘和河流输入的外部强迫的敏感性上，因此这些生物的生态学及其新生产的命运在很大程度上没有得到研究。现在我们知道，dda对亚马逊河羽流中大量的二氧化碳减少负有责任，在200米的漂浮沉积物陷阱中，羽流下方的质量通量比羽流外部高4倍。这使得研究人员假设，这种更大的出口要么是由于DDAs本身的聚集和下沉，要么是浮游动物对DDAs的捕食。在这项研究中，研究人员将进行一系列实地、卫星和模型研究，旨在了解生态，并追踪由DDAs和生活在羽流中的其他浮游植物固定的C和N的命运。通过研究从近海地表水、上层海洋食物网、中上层海洋直至深海的碳和硅酸盐（Si）输出，他们将量化亚马逊河对控制碳封存的生物过程的影响，以及这些区域过程对碳、氮和硅收支的影响。这项研究将超越以往的研究，因为它们将量化1)浮游植物物种演代背景下dda的分布、营养需求和活性，2)二氧化碳减少对浮游植物混合的敏感性，3)有助于下沉通量的放牧和聚集过程，4)该通量的组成，以及5)到达海底的这种物质的比例。这一努力真正代表了碳封存和泵效率的衡量标准。生态模型将用于将实地研究和卫星的观测结果置于年际和更长时间尺度上具有热带气候变化的更大的大西洋盆地的背景下。知识价值：pi已经确定了一个潜在的重要途径，但知之甚少，生态系统控制，气候敏感的碳封存途径，似乎违反了低效的开放海洋生物泵的预期。由于由异源氮（如N2固定）推动的初级生产可以驱动碳从大气到海洋的净、生物介导的转移，亚马逊河羽流中DDAs对碳的固存是一个区域性的重要过程。由于在其他热带河流系统中也发现了dda，它们可能代表了一种具有全球意义但以前被忽视的生物泵机制。更广泛的影响：亚马逊河比其他任何河流都更能吸引公众的想象力。这项研究的目的是利用地球科学的高知名度来促进所有公民的科学素养。该项目将通过COSEE- west、中大西洋COSEE和COSEEOS项目支持研究生和博士后教育、本科生培训，以及K-12教师和本科生的海洋科学教育。这项研究的结果将通过同行评审的出版物、公共数据库和ANACONDAS网站向其他科学家公布，并通过旧金山州立大学rtc -湾区发现博物馆计划向公众公布。