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

新产量是浮游植物总产量的组成部分，由硝酸盐吸收和N2固定推动。在海洋浮游生物生长的氮限制模型中，新的产量可以用来确定有机物质从表层向深层输出的上限。因此，新产品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。第二个关键因素是向深水出口的新产量。出口和新产量都可以独立变化，需要了解两者，以预测材料从地表水中移除的效率。之前在委内瑞拉东北部的加勒比海盆地进行的时间序列测量记录了与冬季上升期和夏季较低（尽管仍然适中）产量有关的惊人生产力，以及深海化学合成对有机出口总量的可能贡献。因此，该地区是低纬度富营养化海洋边缘地区的一个有用的例子，其中大部分产品到达深水。在这个项目中，来自哥伦比亚大学Lamont-Dougherty地球观测站的研究人员将研究硝酸盐吸收和N2固定对总颗粒输出的相对贡献，以及这些来源在卡里亚科盆地的季节性变化。拟议的工作是正在进行的加勒比地区时序项目的配套工作。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，但在这个项目中进行的工作将集中于新产品的来源、数量和出口效率。直接孵化法将用于测量地表水中硝酸盐吸收和氮固定的季节变化，使用硝酸盐和二氮气体的15n示踪技术以及乙炔还原法固定氮。对这些速率进行两年以上的季节性采样将为估计N2固定的相对重要性提供基础，N2固定是向海洋输入组合氮的潜在重要因素。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，以估计地下碳呼吸。最后，这些速率测量将用于校准基于遥感信息的该地区新生产和出口模型。该模型将明确估计N2固定。这项工作将有助于限制热带边缘在向海洋提供组合氮以及海洋总碳吸收方面的累积作用。

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.