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

北大西洋西部的甲烷、乙烯和溶解有机磷循环

• 批准号: 1634080
• 负责人: Daniel Repeta
• 金额: $ 71.7万
• 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: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1634080&HistoricalAwards=false
• 关键词: Methane; Ethylene; Dissolved; Organic; Phosphorus

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.

“海洋甲烷悖论”是指在海洋表层水中观察到高浓度的甲烷，尽管这些水域氧化良好且硫酸盐含量高，这两个特征通常不利于甲烷的产生。该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产生甲烷的潜力。多糖（碳酸盐，如淀粉）是高分子量溶解有机物 (HMWDOM) 的主要成分，它们可以结合甲基膦酸酯，从而可能在地表水中产生甲烷。 当这些 HMWDOM 多糖被引入海水样品中时，研究人员发现产生的甲烷具有异常的稳定碳同位素比率，与富含甲烷的反常地表水中所见的情况相当。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进行测量，研究人员和他的合作者将重新评估初步数据以及这些结果对甲烷整个海洋循环的影响。教育和外展工作都已包括在内。 对于教育部分，一名博士后、一名研究生和暑期本科生将参与该项目，而对于外展活动，支持者计划为高中生开发基础科学和海洋学课程，其中包括一名高中教师在研究巡航中，并将结果整合到有机地球化学课程中，该课程的讲座将在网上公开发布。该项目旨在评估“海洋甲烷悖论”，即高硫酸盐、氧化良好的地表水中甲烷过饱和，是由溶解有机物 (DOM) 的微生物循环引起的可能性。有大量的初步证据支持这一理论。例如，来自 ALOHA 站的样品用纯化的高分子量 DOM (HMWDOM) 多糖进行了修改，并刺激了甲烷、乙烯和丙烯的产生。 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，这些酯可能促进甲烷、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 d13C 值与与过饱和地表水相关的异常值非常吻合。只有一小部分 HMWDOM 多糖可以轻松解释海洋甲烷悖论，而这个过程也可以轻松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。研究人员将通过配对痕量气体和 HMWDOM 膦酸盐以及北大西洋西部的稳定碳同位素测量来评估初步证据并评估微生物 DOM 循环理论。

项目成果

Phosphonate cycling supports methane and ethylene supersaturation in the phosphate‐depleted western North Atlantic Ocean

磷酸盐循环支持北大西洋西部磷酸盐耗尽的甲烷和乙烯过饱和

• DOI: 10.1002/lno.11463
• 发表时间: 2020-05
• 期刊: Limnology and Oceanography
• 影响因子: 4.5
• 作者: Sosa, Oscar A.;Burrell, Timothy J.;Wilson, Samuel T.;Foreman, Rhea K.;Karl, David M.;Repeta, Daniel J.
• 通讯作者: Repeta, Daniel J.