Methane, Ethylene, and Dissolved Organic Phosphorus Cycling in the Western North Atlantic Ocean

“海洋甲烷悖论”是指在海洋表面沃茨中观测到高浓度的甲烷，尽管这些沃茨含氧良好且硫酸盐含量高，这两个特征通常不利于甲烷的产生。本项目旨在阐明这一悖论的原因。根据初步结果，研究人员确定了溶解有机物的微生物循环刺激甲烷生产的潜力。多糖（碳酸盐，如淀粉）是高分子量溶解有机物（HMWDOM）的主要成分，并且它们可以掺入甲基膦酸酯，这可能允许在表面沃茨中产生甲烷。 当这些HMWDOM多糖被引入海水样本时，研究人员看到甲烷的产生具有异常的稳定碳同位素比，与富含甲烷的矛盾表面沃茨中所见相当。通过对北大西洋西部的痕量气体，HMWDOM膦酸盐和稳定碳同位素测量进行测量，研究人员及其合作者将重新评估初步数据以及这些结果对整个海洋学甲烷循环的影响。教育和外联工作都包括在内。 在教育部分，一名博士后、一名研究生和暑期本科生将参与该项目，而在外联活动方面，提议者计划为高中生编制基础科学和海洋学课程，让一名高中教师参加研究航行，并将研究结果纳入有机地球化学课程，该课程的讲座将在线提供。该项目旨在评估“海洋甲烷悖论”或高硫酸盐、富氧表层沃茨中甲烷过饱和是由溶解有机物的微生物循环造成的可能性。有大量的初步证据支持这一理论。例如，从站ALOHA的样品进行了修订与纯化的高分子量DOM（HMWDOM）多糖，甲烷，乙烯和丙烯的生产受到刺激。HMWDOM多糖包含甲基膦酸酯（MPn）、2-羟乙基膦酸酯（2-HEP）和其他次要膦酸酯，这些物质可能促进甲烷、乙烯和丙烯的产生。碳同位素数据支持这一理论是海洋甲烷悖论背后的过程;从富含HMWDOM多糖的样品中产生的甲烷的d13 C值与与过饱和地表水相关的异常值吻合良好。只有一小部分HMWDOM多糖可以很容易地解释海洋甲烷悖论，这一过程可以很容易地完全修改目前对海洋和大气之间大规模甲烷循环的理解。研究人员将评估初步证据，并通过在北大西洋西部进行成对的痕量气体和HMWDOM膦酸盐以及稳定的碳同位素测量来评估微生物DOM循环理论。

The "marine methane paradox" refers to observations of high concentrations of methane in surface waters of the ocean, even though these waters are well-oxygenated and high in sulfate, both features which generally do not favor the production of methane. This project aims to elucidate on the cause of this paradox. Based on preliminary results, the investigator identified the potential for methane production stimulated by microbial cycling of dissolved organic matter. Polysaccharides (carbonates such as starch) are a major component of high molecular weight dissolved organic matter (HMWDOM) and they can incorporate esters of methylphosphonate, which may be allowing for the production of methane in surface waters. When these HMWDOM polysaccharides were introduced to seawater samples, the researchers saw production of methane with an anomalous stable carbon isotope ratio comparable to what is seen in the paradoxical surface waters enriched in methane. By making measurements of trace gases, HMWDOM phosphonate, and stable carbon isotope measurements in the western North Atlantic Ocean, the investigator and his collaborators will reassess the preliminary data and the implications of these results for the entire oceanographic cycling of methane. Both educational and outreach efforts have been included. For the educational component, a postdoc, a graduate student, and summer undergraduate students will be work on the project, whereas for the outreach activities, the proponent plans to develop curricula on basic science and oceanography for high school students, include a high school teacher in the research cruise, and integrate results into an organic geochemistry course, the lectures of which will be publically available online. This project seeks to evaluate the possibility that the "marine methane paradox", or the super-saturation of methane in high sulfate, well-oxygenated surface waters, is caused by microbial cycling of dissolved organic matter (DOM). There has been a great deal of preliminary evidence to support this theory. For example, samples from station ALOHA were amended with purified high molecular weight DOM (HMWDOM) polysaccharides, and methane, ethylene, and propylene productions were stimulated. HMWDOM polysaccharides incorporate esters of methylphosphonate (MPn), 2-hydroxyethylphosphonates (2-HEP), and other minor phosphonates, which are likely facilitating the production of methane, ethylene, and propylene. Carbon isotope data supports that this theory is the process behind the marine methane paradox; the d13C value of methane produced from HMWDOM polysaccharide enriched samples agrees well with the anomalous value associated with the super-saturated surface water. Only a small fraction of HMWDOM polysaccharides can easily explain the marine methane paradox, and this process could just as easily fully revise the current understanding of large scale methane cycling between the ocean and atmosphere. The researchers will assess the preliminary evidence and evaluate the microbial DOM cycling theory by making paired trace gas and HMWDOM phosphonate, as well as stable carbon isotope measurements in the western North Atlantic Ocean.