Sources of New Production and the Degredation of Organic Matter in a Tropical Margin Influenced by Seasonal Upwelling

新的生产量是由硝酸盐吸收和氮气固定所推动的浮游植物总生产量的组成部分。在海洋浮游生物生长的氮限制模型中，新的产量可以用来定义有机物质从表层向深层出口的上限。因此，新的生产量是确定海洋在二氧化碳等生物活性物质垂直通量中的作用的重要起点。第二个关键因素是出口到深度的新产量。出口和新生产都可以独立变化，需要了解两者，以预测从地表水中清除物质的效率。委内瑞拉东北部附近的Cariaco盆地以前的时间序列测量记录了与冬季上升期和夏季产量较低(尽管仍然适中)有关的惊人生产力，以及深层化学合成可能对有机出口总量的贡献。因此，该区域是低纬度富营养化海洋边缘区域的一个有用的例子，在该区域，许多产品进入深水。在这个项目中，来自哥伦比亚大学Lamont-Dougherty地球天文台的研究人员将研究Cariaco盆地硝酸盐吸收和氮气固定对总颗粒物输出的相对贡献，以及这些来源如何随季节变化。拟议的工作是正在进行的加勒比时间系列项目的配套工作。虽然后一项核心工作将提供基本的后勤、物理和化学以及生产力测量，但该项目开展的工作将侧重于新产品的来源、数量和出口效率。直接培养法将用15N示踪技术测量地表水体中硝酸盐吸收和氮气固定的季节变化，包括硝酸盐和双氮气的示踪技术以及乙炔还原固定氮气的方法。在两年内对这些速率进行季节性采样，将为估计氮固定的相对重要性提供基础，氮固定是结合氮向海洋的潜在重要输入。除了沉积物捕集器的比较外，还将使用最近开发的13C稀释法来测量出口的总体效率，以估计次表层碳呼吸。最后，这些速度测量将被用来根据遥感信息校准该地区新的生产和出口模型。该模型将明确估计氮气的固定。这项工作将有助于限制热带边缘在向海洋供应结合氮以及在海洋总碳吸收中的累积作用。

ABSTRACTOCE-0118867New production is that component of total phytoplankton production fueled by nitrate uptake and the fixation of N2. In a nitrogen-limited model of ocean plankton growth, new production can be used to define an upper limit for the export of organic material from the surface to deeper layers. Thus, new production is an important starting point to determine the ocean's role in the vertical flux of bio-active materials such as carbon dioxide. A second critical factor is the amount of new production that is exported to depth. Both export and new production can vary independently and both need to be understood to predict how efficiently material will be removed from surface waters. Previous time series measurements in the Cariaco Basin off northeast Venezuela recorded prodigious productivity associated with the winter upwelling period and lower (although still moderate) production in summer as well as the possible contribution of chemosynthesis at depth to the total organic export. Thus, the region is a useful example of a low-latitude eutrophic-ocean margin region in which much of the production reaches deep water. In this project, researchers from the Lamont-Dougherty Earth Observatory of Columbia University will study the relative contribution of nitrate uptake and N2 fixation to total particulate export and how these sources vary seasonally in the Cariaco Basin. The proposed work is a companion effort with the ongoing CARIACO Time-Series Project. While the latter core effort will provide the basic logistics, physical and chemical and productivity measurements, the work undertaken in this project will focus on the source, amount and export efficiency of new production. Direct incubation methods will be used to measure the seasonal changes in nitrate uptake and N2 fixation in surface waters using both 15 N tracer techniques for nitrate and di-nitrogen gas as well as the acetylene reduction for N2 fixation. Seasonal sampling of these rates over two years will provide a basis for estimating the relative importance of N2 fixation, a potentially important input of combined nitrogen to the ocean. In addition to sediment trap comparisons, the overall efficiency of export also will be measured with a recently developed 13C dilution method for estimating sub-surface carbon respiration. Finally, these rate measurements will be used to calibrate a model of new production and export in the region based on remotely sensed information. The model will explicitly estimate N2 fixation. This work will help to constrain the cumulative role of tropical margins in the supply of combined nitrogen to the ocean as well as in total-ocean carbon uptake.