Collaborative Research: What Happens to Terrestrial Organic Matter in the Ocean? Solving the Mystery Behind an Iconic Question

合作研究：海洋中的陆地有机物会发生什么？

• 批准号: 1851309
• 负责人: Valier Galy
• 金额: $ 59.9万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-08-01 至 2025-01-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1851309&HistoricalAwards=false
• 关键词: Collaborative; Research; What; Happens; Terrestrial

The Amazon River is one of the largest and most important rivers in the world. It not only carries water through the Amazon rain forests, it also carries mud - lots of mud. This mud settles when the river joins the ocean, forming the Amazon delta. Waves and wind re-suspend some of this mud, which forms mud banks that slowly move from the coast of Brazil, to French Guiana, Suriname, and Guyana. Not only do these mud banks shape the coastlines of these areas, but they also serve as a storage for carbon that had been removed from the atmosphere by the Amazon rainforest, dropped to the forest floor and washed into the river, ultimately transported on particles of mud into the Amazon delta. Normally, this represents a transfer of carbon from the atmosphere to the sediment and rock record, hiding it away for thousands to millions of years and participating in the natural regulation of atmospheric carbon dioxide concentration. However, the Amazon's special case of mud banks that travel hundreds of miles along the coast has long been believed to stir up this carbon and release most of it back to the atmosphere. This idea has held for decades, but if wrong, may have a large impact on our understanding of the ocean's carbon cycle. This research will use new science and technology to change the way we look at river carbon cycling in the ocean by sampling the mud banks, ocean waters, and Amazon River waters more thoroughly than has been previously done, with the aim to understand and quantify the storage of land-derived carbon in marine mudbank sediments offshore the Amazon River. This research will serve as the core of two Ph.D. dissertations and will interface with the Woods Hole Partnership Educational Program (PEP) to provide under-represented minority college students an opportunity to gain practical experience in marine and environmental sciences. The project will also be incorporated into the Saint Petersburg Science Fest, an event that brings several thousand school children to University of South Florida campus during one weekend every autumn to showcase different research projects and initiatives.Twenty years ago, John Hedges posed a seminal question pertaining to the role of the ocean in the carbon cycle: "what happens to terrestrial organic matter in the oceans?" That question was set upon a conundrum - because riverine organic matter is highly degraded, it should be expected to suffer minimal respiration in the ocean, yet by most accounts continental margins seem to be incinerators of terrestrial organic matter. However, much of this paradigm was originally built upon biogeochemical studies of the Amazon sub-aqueous delta and the mobile fluidized mudbanks along the Guianas coast. However, preliminary state of the art characterizations of organic carbon in Amazon River and mudbank sediments suggest that a fraction of terrestrial organic carbon is actually not refractory and as such is rapidly and efficiently oxidized in the ocean, whereas another fraction is refractory and is in fact quantitatively preserved in marine sediments. Overall, the data suggest an underestimation of burial efficiency in the realm of 50-100%. This proposal focuses on gaining a transformative mechanistic and quantitative understanding of the fate of terrestrial organic carbon in the coastal ocean offshore of the Amazon River. This will be done through i) sampling the marine province offshore of the Guianas coast (the Guianas mudbanks) as well as the Amazon River delta, using a shallow-draft research vessel and ii) using novel state of the art geochemical analysis of organic carbon - in particular ramped oxidation and compound specific radiocarbon analysis - and elemental composition to demonstrate the selective nature of terrestrial organic carbon oxidation and provide new estimates of burial efficiency of this system - with implications for the global inventory of terrestrial organic carbon in the ocean.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.

亚马逊河是世界上最大和最重要的河流之一。它不仅输送水穿过亚马逊雨林，还输送泥土——大量的泥土。当河流与海洋汇合时，这些泥浆就会沉淀下来，形成亚马逊三角洲。海浪和风使部分泥浆重新悬浮，形成泥滩，慢慢从巴西海岸移动到法属圭亚那、苏里南和圭亚那。这些泥滩不仅塑造了这些地区的海岸线，而且还储存了亚马逊雨林从大气中吸收的碳，这些碳掉落到森林地面并冲入河流，最终通过颗粒物运输。泥浆流入亚马逊三角洲。通常，这代表碳从大气转移到沉积物和岩石记录中，将其隐藏数千至数百万年，并参与大气二氧化碳浓度的自然调节。然而，亚马逊地区沿海岸绵延数百英里的泥滩的特殊情况，长期以来一直被认为会激起这些碳并将其大部分释放回大气中。这个想法已经存在了几十年，但如果错误，可能会对我们对海洋碳循环的理解产生重大影响。这项研究将利用新的科学技术，通过比以前更彻底地对泥滩、海水和亚马逊河水域进行采样，改变我们看待海洋河流碳循环的方式，目的是了解和量化亚马逊河沿岸海洋泥滩沉积物中陆地来源碳的储存。 这项研究将作为两个博士学位的核心。论文并将与伍兹霍尔合作教育计划（PEP）对接，为代表性不足的少数族裔大学生提供获得海洋和环境科学实践经验的机会。该项目还将纳入圣彼得堡科学节，该活动每年秋天的一个周末都会吸引数千名学童来到南佛罗里达大学校园，展示不同的研究项目和举措。二十年前，约翰·赫奇斯提出了一个开创性的问题关于海洋在碳循环中的作用：“海洋中的陆地有机物会发生什么？” 这个问题是基于一个难题而提出的——因为河流有机物高度退化，预计它在海洋中受到的呼吸作用应该是最小的，但根据大多数说法，大陆边缘似乎是陆地有机物的焚化炉。然而，这种范式的大部分最初是建立在对亚马逊水下三角洲和圭亚那海岸沿线的流动流化泥滩的生物地球化学研究的基础上的。 然而，亚马逊河和泥滩沉积物中有机碳的初步表征表明，一部分陆地有机碳实际上不耐火，因此在海洋中快速有效地氧化，而另一部分则耐火，实际上是耐火的。大量保存在海洋沉积物中。总体而言，数据表明埋藏效率被低估了 50-100%。该提案的重点是对亚马逊河沿岸海洋中陆地有机碳的命运获得变革性的机制和定量理解。这将通过 i) 使用浅吃水研究船对圭亚那海岸（圭亚那泥滩）和亚马逊河三角洲近海的海洋省进行采样，以及 ii) 使用最先进的有机碳地球化学分析来完成- 特别是斜坡氧化和化合物特定放射性碳分析 - 和元素组成，以证明陆地有机碳氧化的选择性性质并提供该系统埋藏效率的新估计 - 对全球陆地有机碳清单的影响该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。