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

这是一个项目-南大洋铁实验（SOFeX）-的一部分，在南极绕极流内的一小块区域内播种铁，通过测量加入铁的惰性示踪剂（SF6）的分布来跟踪这片水域，并评估对这种加入的化学和生物反应。最近的观察表明，铁在南大洋所有区域的有机物生产和输出中起着控制作用。此外，由于南大洋含有世界海洋中最大的无机宏量营养素池，因此它最有可能通过充当CO2的汇来影响大气二氧化碳的浓度。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时发生的复杂的生物相互作用。这项调查将测量初级生产力内和外的富铁补丁的水，以量化的直接响应铁的原位浮游植物组合的时间尺度天。将测量三个粒度级的生产率：5gm、5 but 20 gm和20 μ m。将通过高效液相色谱法（HPLC）直接测定三种大小级分的定量分类组成。由于两个原因，也将测量相同组分的光合作用与辐照度（P与E）的响应。首先，P与E反应是铁限制的敏感措施。其次，这些数据将被用来调查铁/辐照度的相互作用，因为它已经假设，浮游植物适应低光需要更多的铁比那些适应较高的iffadiances（一个条件，特别是在南大洋）。 浮游植物的特定类群的生长速率也将直接使用色素标记技术进行测量。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与E响应，使研究人员能够评估量子效率的空间（水平和垂直）响应和整体光合作用沿着梯度穿过丰富的补丁。解决硅藻相对于其他类群的响应是至关重要的浮游植物对不同铁供应的响应的准确建模，因为硅藻水华在向深海输出碳中起着至关重要的作用。

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.