Southern Ocean Experiment (SOFeX): Primary/Bacterial Production and Taxon-Specific Growth and Photosynthetic Responses

南大洋实验（SOFeX）：初级/细菌生产和分类群特异性生长和光合反应

• 批准号: 9911441
• 负责人: Richard Barber
• 金额: $ 32万
• 依托单位: Duke University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-06-01 至 2004-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9911441&HistoricalAwards=false
• 关键词: Southern; Ocean; Experiment; SOFeX; Primary

This is part of a project - the Southern Ocean Iron Experiment (SOFeX) - to seed a small area within the Antarctic Circumpolar Current with iron, to follow this patch of water by measuring the distribution of an inert tracer (SF6) added with the iron, and to assess the chemical and biological responses to this addition. Recent observations have indicated that iron plays a controlling role in the production and export of organic matter in all regions of the Southern Ocean. Furthermore, because the Southern Ocean contains the largest pool of inorganic macronutrients of the world ocean, it has the greatest potential to influence the concentration of atmospheric carbon dioxide by acting as a sink for C02- In order to predict the impact of natural variations in iron supply on carbon partitioning, it is imperative that we understand the complex biological interactions that occur upon iron enrichment. This investigation will measure primary productivity within and outside the iron-enriched patch of water to quantify the direct response of iron to the in situ phytoplankton assemblage on time scales of days. Productivity of three size fractions will be measured: 5gm, 5 but 20 gm, and 20 ~tm. The quantitative taxonomic composition of the three size fractions will be directly determined by high performance liquid chromatography (HPLC). The photosynthesis versus irradiance (P vs E) responses of the same fractions also will be measured for two reasons. First, the P vs E response is a sensitive measure of iron limitation. Secondly, the data will be used to investigate iron/irradiance interactions because it has been hypothesized that phytoplankton adapted to low light require more iron than do those adapted to higher iffadiances (a condition especially important in the Southern Ocean). The taxon-specific growth rates of phytoplankton will also be measured directly using a pigment-labeling technique. Finally, the project will use a new Fast Repetition Rate (FRR) fluorescence technique that will provide P vs E responses in near real-time, allowing the investigators to assess the spatial (both horizontal and vertical) responses of quantum efficiency and bulk photosynthesis along gradients across the enriched patch. Resolving the responses of diatoms relative to other taxa is critical for accurate modeling of the phytoplankton response to varying iron supply because diatom blooms play a pivotal role in the export of carbon to the deep sea.

这是“南大洋铁实验”（SOFeX）项目的一部分，目的是在南极环极流内的一小块区域撒上铁，通过测量添加了铁的惰性示踪剂（SF6）的分布来跟踪这片水域，并评估对这种添加物的化学和生物反应。最近的观察表明，铁在南大洋所有区域的有机物的产生和输出中起着控制作用。此外，由于南大洋拥有世界海洋中最大的无机常量营养素库，因此它作为二氧化碳的汇，对大气二氧化碳浓度的影响潜力最大。为了预测铁供应的自然变化对碳分配的影响，我们必须了解铁富集过程中发生的复杂生物相互作用。本研究将测量富铁水域内外的初级生产力，以量化铁对原位浮游植物组合的直接反应，以天为时间尺度。测定三种粒径馏分的产率：5gm、5 ~ 20gm和20 ~tm。三种大小馏分的定量分类学组成将由高效液相色谱法直接测定。由于两个原因，还将测量相同馏分的光合作用与辐照度（P vs E）响应。首先，P / E响应是铁限制的敏感指标。其次，这些数据将用于研究铁与辐照度的相互作用，因为有人假设，适应低光的浮游植物比适应高辐照度的浮游植物需要更多的铁（这在南大洋特别重要）。利用色素标记技术直接测量浮游植物的分类特异性生长速率。最后，该项目将使用一种新的快速重复率（FRR）荧光技术，该技术将提供近实时的P / E响应，使研究人员能够沿着富集斑块的梯度评估量子效率和整体光合作用的空间（水平和垂直）响应。解决硅藻相对于其他分类群的反应对于准确模拟浮游植物对不同铁供应的反应至关重要，因为硅藻华在向深海输出碳方面起着关键作用。