Collaborative Research: Investigating the Source and Flux of Dissolved Organic Carbon Released from Methane Seeps to the Deep-ocean

合作研究：调查甲烷渗漏释放到深海的溶解有机碳的来源和通量

• 批准号: 2048357
• 负责人: Jeffrey Seewald
• 金额: $ 44.89万
• 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: 2021
• 资助国家: 美国
• 起止时间: 2021-04-01 至 2025-03-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2048357&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; Source; Flux

Dissolved organic carbon (DOC) is a key component of the ocean’s food web and carbon cycle, and carbon exchanged between oceanic DOC and the atmosphere has influenced atmospheric CO2 levels on timescales ranging from recent decades to the geologic past. Production by marine algae in the surface ocean is the largest source of DOC and its effects on the ocean carbon cycle are widely appreciated. However, the contribution of DOC from additional sources such as rivers, hydrothermal vents, and methane seeps and their impact on ocean ecology and chemistry are not well understood. Each source differs in terms of its biological utilization and age, which affects the storage and distribution of DOC among the ocean basins. Methane seeps located along continental margins are particularly significant because they may transfer globally significant quantities of carbon stored below the seafloor as natural gas and gas hydrate to the oceans. This project will investigate the production, flux, composition and potential for biological utilization of DOC at Hydrate Ridge, located offshore Oregon. Hydrate Ridge is a prominent methane seep with massive accumulations of gas hydrate and a node of the Ocean Observatories Initiative telecommunications cabled array on the Juan De Fuca tectonic plate, which provides a continuous stream of real-time regional oceanographic data. We will sample and chemically characterize methane, DOC, and other materials to provide information about where the materials originated (deep vs shallow), how they have been chemically altered, to what extent they may feed deep ocean organisms, or contribute to the long term storage of DOC in the ocean. Experiments and analysis will be conducted using sediment cores and bottom water samples collected using either the remotely operated vehicle Jason or the human occupied vehicle Alvin during a 7-day ocean expedition. Additionally, this project will place osmotically-driven pumps on the seafloor to continuously sample fluids for approximately one year, thereby allowing us to monitor the movement of methane and DOC expelled from the seafloor to the ocean and constrain processes that regulate the release of carbon to the oceans at methane seeps. This project will support one graduate student and several undergraduates from a community college in Maryland and a college located in a lower-income urban center in southeastern Massachusetts. We will disseminate project findings to the public with a series of videos for public TV. This study will investigate the production, flux and reactivity of methane-derived dissolved organic carbon (DOC) from methane (CH4) seeps at Hydrate Ridge, Offshore Oregon. The study will address four fundamental questions to determine the significance of CH4-derived DOC within the ocean carbon cycle: (1) How much CH4-derived fossil DOC do seeps contribute to the oceans? (2) To what extent is CH4-derived C incorporated into DOC during anaerobic oxidation of CH4? (3) Is seep DOC bioavailable or recalcitrant when released into the deep ocean? (4) How does the flux of DOC to the water column vary over time? We will employ an interdisciplinary strategy that includes in situ sampling, laboratory incubations, and a comprehensive analytical geochemistry program. Data from the Ocean Observatories Initiative Regional Cabled Array at Southern Hydrate Ridge will be used to provide context for field and experimental data. The composition and abundance of organic and inorganic chemical species along with the stable and radiocarbon isotope composition of pore water, bulk sediment, and water column C pools will be used to identify DOC sources and quantify fluxes from cold seeps characterized by a range of advection rates. The centerpiece of the investigation will be a 7-day research cruise to Hydrate Ridge to collect sediments, pore fluids, and water column samples, and deploy OsmoSamplers for continuous time series fluid sampling. The results will form the foundation for estimating the contribution of CH4-derived DOC to the oceanic DOC pool.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.

溶解有机碳 (DOC) 是海洋食物网和碳循环的关键组成部分，海洋 DOC 与大气之间的碳交换在近几十年到过去地质时期的时间尺度上影响着大气中的二氧化碳水平。表层海洋是 DOC 的最大来源，其对海洋碳循环的影响已得到广泛认可，然而，河流、热液喷口和甲烷渗漏等其他来源对 DOC 的贡献及其对海洋的影响。每个来源的生物利用和年龄都不同，这影响了海洋盆地中 DOC 的储存和分布，这些甲烷渗漏尤其重要，因为它们可能会在全球范围内转移大量的 DOC。该项目将研究位于俄勒冈州近海的水合物岭 (Hydrate Ridge) 的 DOC 的生产、通量、成分和生物利用潜力。胡安德富卡构造板块上大量天然气水合物的堆积和海洋观测计划电信电缆阵列的节点，提供了连续的实时区域海洋学数据流，我们将对甲烷、DOC 和其他物质进行采样和化学表征。提供有关这些材料的来源（深海与浅海）、它们如何发生化学变化、它们可以在多大程度上喂养深海生物或有助于 DOC 在海洋中长期储存的信息。在为期 7 天的海洋探险中，该项目将使用远程操作车辆 Jason 或人类驾驶车辆 Alvin 收集的沉积物岩心和底部水样本进行研究。此外，该项目将在海底放置渗透驱动泵，以连续采样大约一年的流体。年，从而使我们能够监测从海底排放到海洋的甲烷和 DOC 的运动，并限制在甲烷渗漏处调节碳向海洋释放的过程。该项目将为一名研究生和几名本科生提供支持。马里兰州的社区学院和马萨诸塞州东南部低收入城市中心的一所学院将通过一系列公共电视视频向公众传播项目研究结果。这项研究将调查甲烷衍生的生产、通量和反应性。俄勒冈州近海水合物岭渗出的甲烷 (CH4) 中溶解的有机碳 (DOC) 该研究将解决四个基本问题，以确定源自 CH4 的 DOC 在海洋碳循环中的重要性：(1) 有多少源自 CH4 的化石。 DOC 对海洋有贡献吗？ (2) CH4 厌氧氧化过程中，CH4 衍生的 C 在多大程度上融入 DOC？(3) 渗漏 DOC 释放到深海时是可生物利用的还是难降解的？ DOC 的通量随时间变化？我们将采用跨学科策略，包括原位采样、实验室孵化和来自海洋的综合​​分析地球化学数据。南部水合物岭的观测站计划区域电缆阵列将用于提供现场和实验数据的背景，包括有机和无机化学物质的组成和丰度，以及孔隙水、大量沉积物和水柱 C 的稳定和放射性碳同位素组成。池将用于识别 DOC 来源并量化以一系列平流速率为特征的冷泉通量，调查的核心内容将是前往水合物岭收集沉积物的为期 7 天的研究航行，孔隙流体和水柱样本，并部署 OsmoSampler 进行连续时间序列流体采样。结果将为估计 CH4 衍生的 DOC 对海洋 DOC 库的贡献奠定基础。该奖项反映了 NSF 的法定使命，并被认为是值得的。通过使用基金会的智力优势和更广泛的影响审查标准进行评估来获得支持。