Collaborative Research: Methane efflux from river influenced coastal marine sediments

合作研究：甲烷是一种强烈的温室气体，大气中甲烷的含量正在增加。大量的甲烷存在于沉积物中。因此，了解沉积物释放了多少甲烷是改进甲烷排放量估计的关键第一步。沿海沉积物被认为是甲烷的主要来源，上覆水和潜在的大气。然而，人们对沿海环境中的甲烷通量知之甚少。该项目将测量从沿海沉积物流入墨西哥湾沃茨的甲烷通量。甲烷产生于沉积物中，当微生物分解有机物时，并来自地质来源。然而，从沉积物中释放的甲烷量可以通过微生物减少，微生物在存在氧气的沉积物表面附近氧化甲烷（好氧氧化）和在不存在氧气的沉积物深处氧化甲烷（厌氧氧化）。这项研究的重点是甲烷的有氧氧化是防止其释放到水柱的关键过程的环境。该项目的结果将有助于确定沿海海洋中甲烷释放的重要来源。这项工作是及时的，因为受河流影响的海洋沉积物对人类活动和全球气候变化很敏感。参与这项研究的科学家将把研究结果转化为对碳循环科学家、政策制定者、学生、教师和公众有用的信息。他们将与路易斯安那大学海洋联盟、格鲁吉亚大学和路易斯安那州立大学的教育和推广项目合作，并为本科到研究生水平的科学家提供培训。高沉积速率，如在河流附近发现的沉积速率，可以驱动沉积物中的甲烷流出，底沃茨中甲烷浓度的升高就证明了这一点。观测数据表明，沉积物从河流影响浅水陆架区与低溶解氧浓度的水柱排放更多的甲烷比典型的大陆架沉积物的水柱。该项目将海底通量测量、地球化学和速率分析纳入一个反应-迁移模型，以评估环境对海底过程的影响。科学家小组将使用原位着陆器测量海底氧气和甲烷的通量，以及氧气和硫化物的沉积物微剖面。沉积和混合速率将使用天然存在的放射性同位素来确定。将使用放射性示踪剂确定硫酸盐还原和甲烷氧化速率，并将进行一系列广泛的背景地球化学分析。在路易斯安那州东南海岸的两次巡航中，共有5个地点将成为目标。数据综合将有助于我们更好地理解河流，海洋沉积物和海洋沉积物甲烷释放之间的相互作用。该项目支持早期职业调查员的发展，并将为一名博士后助理，两名研究生，三名研究助理提供培训。这一努力将利用LUMCON REU网站计划，以支持每年至少一名学生。教育目标强调通过推广非正式教育，课堂上的正式教育，以及社区大学生的真实研究经验。许多活动都强调了向科学界、学生、政策制定者和公众传播信息的重要性。该奖项反映了NSF的法定使命，并被认为值得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来支持。

Collaborative Research: Methane efflux from river influenced coastal marine sedimentsMethane is a strong greenhouse gas and the amount of methane in the atmosphere is increasing. Large amounts of methane are present in sediments. Thus, understanding how much methane is released from sediments is a key first step for improving estimates of methane emissions. Coastal sediments are thought to be large sources of methane to the overlying water and potentially the atmosphere. Yet, fluxes of methane from coastal environments are poorly known. This project will measure methane fluxes from coastal sediments into the waters of the Gulf of Mexico. Methane is produced in sediments when microorganisms break down organic matter and from geological sources. However, the amount of methane released from sediments can be reduced by microorganisms that oxidize methane near the sediment surface where oxygen is present (aerobic oxidation) and deep in the sediment where oxygen is not present (anaerobic oxidation). This study focuses on environments where the aerobic oxidation of methane is the key process that prevents its release to the water column. Results from this project will help identify areas of the coastal ocean that are significant sources of methane release. This work is timely, as river-influenced marine sediments are sensitive to anthropogenic activities and global climate change. Scientists involved in this study will translate the findings into useful information for carbon cycle scientists, policy makers, students, teachers, and the public. They will work with education and outreach programs at Louisiana Universities Marine Consortium, University of Georgia, and Louisiana State University, and provide training to scientists from undergraduate to postgraduate levels.High sedimentation rates, like those found near rivers, can drive methane efflux from sediments, as evidenced by elevated methane concentrations in bottom waters. Observational data suggest that sediments from river influenced shallow shelf regions with low dissolved oxygen concentrations in the water column emit more methane to the water column than typical continental shelf sediments. This project combines benthic flux measurements, geochemistry and rate analysis into a reaction-transport model that will evaluate environmental influences on benthic processes. The team of scientists will measure benthic fluxes of oxygen and methane using an in situ lander, and sediment micro-profiles of oxygen and sulfide. Sedimentation and mixing rates will be determined using naturally occurring radioisotopes. Sulfate reduction and methane oxidation rates will be determined using radiotracers and a broad suite of contextual geochemical analysis will be performed. During two cruises off the southeastern coast of Louisiana, a total of 5 sites will be targeted. The data synthesis will help refine our understanding of the interactions between rivers, marine sediments, and methane releases from marine sediments. The project supports the development of an early career investigator and will provide training for one postdoctoral associate, two graduate students, three research assistants. This effort will leverage the LUMCON REU site program to support at least one student per year. The education goals emphasize informal education through outreach, formal education in the classroom, and authentic research experiences for community college students. Many of the activities emphasize the importance of communicating information to the scientific community, students, policy makers, and the general public.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.