Nitrogen Cycling in the Upwelling Waters of the Equatorial Pacific Region

赤道太平洋水域营养物质的上涌提高了浮游生物生物量和大面积的初级产量，并可能占全球新产量的很大一部分。在上升流轴的南北几百公里范围内，硝酸盐持续存在于光带中，人们提出了几种假设来解释浮游植物明显无法充分利用它的原因。这个项目假设放牧控制着浮游植物的生物量，养分的循环提供了浮游植物对氮的大部分需求。这项研究将利用过去几年在马尾藻海和JGOFS北大西洋水华实验中应用的新技术来测试放牧/再生假设，这是美国JGOFS赤道太平洋项目的一部分。这一假设暗示了含氮养分的特定模式和分布、它们的利用和再生，以及营养物和悬浮和下沉颗粒物中天然N同位素丰度。该项目与Jim McCarthy（9022411）合作，由两个主要部分组成：1)高精度（必要时为纳摩尔灵敏度）和高空间分辨率的营养物质浓度测量；2)低水平和高灵敏度示踪剂对其生物吸收和转化的研究。这项研究的结果将构成对赤道太平洋区域“新”氮和“再生”氮的相对重要性的评估。将查明调节生产的主要机制，并评估“新”生产对颗粒通量和碳固存的贡献程度。

The upwelling of nutrients in Equatorial Pacific waters enhances plankton biomass and primary production over a large area and may account for a significant fraction of the global new production. Nitrate persists in the euphotic zone in an area a few hundred kilometers north and south of the upwelling axis and several hypotheses have been advanced to account for the apparent inability of the phytoplankton to fully utilize it. This project hypothesizes that grazing controls phytoplankton biomass and that recycling of nutrients provides much of the phytoplankton nitrogen requirement. This study will utilize new techniques which have been applied over the last few years in the Sargasso Sea and the JGOFS North Atlantic Bloom Experiment to test the grazing/regeneration hypothesis as part of the U.S JGOFS Equatorial Pacific program. This hypothesis implies specific patterns and distributions of nitrogenous nutrients, their utilization and regeneration, and natural N isotope abundance in nutrients and suspended and sinking particulate material. This project is collaborative with Jim McCarthy (9022411) and consists of two major components: 1) nutrient concentration measurements of high precision (nanomolar sensitivity where necessary) and high spatial resolution; 2) low level and high sensitivity tracer studies of their biological uptake and transformations. The results of this study will constitute an assessment of the relative importance of "new" and "regenerated" nitrogen in the Equatorial Pacific region. The principal mechanisms regulating production will be identified, and the extent to which "new" production contributes to particle flux and carbon sequestration will be assessed.