Biogeochemical Processes along the Lower Amazon River Continuum

这项研究解决了二氧化碳从河流到大气的运动，这种现象被称为脱气。最近对河流排放的修正估计表明，它是全球碳循环的重要组成部分。但是，究竟有多少气体排放发生，以及哪些因素控制了气体排放的速度，人们仍然知之甚少，特别是在大型热带河流的低潮区。大多数对气体排放的测量都是在海洋的上游进行的，海洋学研究也仅限于近海地区。这留下了一个重大的知识缺口，在上游测量站和海洋研究船在海上接收信号的近海站点之间，很少或根本没有可用的数据。这个以亚马逊河为重点的项目，将对河流碳循环的功能以及最终对全球循环的影响提供更深入的了解。为该项目开发的耦合模型将提供给决策者，用于评估不断变化的亚马逊流域的更广泛的水资源问题。该项目将支持培训一名研究生和一名从未被充分代表的少数民族中招募的本科生。这项研究将结合河船考察、遥感和建模来检验一个假设，即在整个下游河流和羽流内部，溶解的二氧化碳水平仍高于大气饱和度。在这种情况下，当充分考虑淡水和低盐度水域时，亚马逊河的羽流将成为大气中二氧化碳的净来源。气体、溶解和微粒碳浓度随潮汐变化的假设将通过对潮汐循环的详细测量来评估。为了深入了解调节有机物分解和能量产生的生物机制，微生物代谢的蛋白质组学特征和溶解有机物的超高分辨率质谱表征相结合将被采用。最后，一个详细的水动力学模型，包括生物过程和流域水文模型的输入，将用于提供整个项目的综合。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This research addresses the movement of CO2 from rivers to the atmosphere, a phenomenon referred to as outgassing. Recently revised estimates of riverine outgassing suggest that it is a significant component of the global carbon cycle. But precisely how much outgassing occurs and what factors control the rates of outgassing remain poorly understood, especially in the lower, tidal reaches of large tropical rivers. Most measurements of outgassing are made far upstream of the ocean, and oceanography studies are restricted to zones that are offshore. This leaves a major knowledge gap, with little or no data available for extensive river reaches between upstream gauging station and offshore sites where oceanographic research vessels pick up the signal at sea. This project, with a focus on the Amazon River, will provide greater insights into how riverine carbon cycles function, and ultimately their influence on global cycles. The coupled models developed for the project will be available to policy makers for use in evaluating broader water resource issues of the changing Amazon basin. The project will support the training of one graduate student and an undergraduate student recruited from an underrepresented minority. This research will use a combination of river boat expeditions, remote sensing, and modeling to test the hypothesis that dissolved CO2 levels remain above atmospheric saturation along the entire lower river and in the inner reaches of the plume. Under those conditions the Amazon River plume would act as a net source of CO2 to the atmosphere when freshwaters and low salinity waters are fully considered. The hypothesis that gaseous, dissolved, and particulate concentrations of carbon vary consistently with the tide will be evaluated through detailed measurements over tidal cycles. To obtain insights into the biological mechanisms regulating organic matter decomposition and energy production a combination of proteomic signatures of microbial metabolism and dissolved organic matter characterization by ultra-high-resolution mass spectrometry will be employed. Finally, a detailed hydrodynamic model, that includes biological processes and inputs from a basin hydrology model, will be used to provide synthesis across the project.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.