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: 2049517
• 负责人: Laura Lapham
• 金额: $ 54.31万
• 依托单位: University of Maryland Center for Environmental Sciences
• 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 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2049517&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和大气之间的碳交换影响了从近几十年到地质过去的大气CO2水平。海洋表层藻类是DOC的最大来源，其对海洋碳循环的影响受到广泛关注。然而，DOC的贡献，从其他来源，如河流，热液喷口，甲烷渗漏及其对海洋生态和化学的影响还没有得到很好的理解。不同来源的DOC在生物利用和年龄方面存在差异，这影响了DOC在海洋盆地中的储存和分布。位于沿着大陆边的甲烷渗漏特别重要，因为它们可能将全球大量储存在海底以下的碳作为天然气和天然气水合物转移到海洋。本计画将调查位于俄勒冈州外海的海伯利脊溶解有机碳的产量、通量、组成及生物利用潜力。海伯利脊是一个突出的甲烷渗漏点，有大量的天然气水合物积聚，是海洋观测站倡议电信电缆阵列在胡安·德富卡构造板块上的一个节点，提供连续不断的实时区域海洋学数据。我们将对甲烷，DOC和其他材料进行采样和化学表征，以提供有关材料起源（深与浅）的信息，它们如何被化学改变，在何种程度上它们可以喂养深海生物，或有助于DOC在海洋中的长期储存。在为期7天的海洋考察期间，将利用遥控潜水器Jason或载人潜水器Alvin收集的沉积物岩心和底层水样本进行实验和分析。此外，该项目将在海底放置螺旋驱动的泵，持续对流体进行大约一年的采样，从而使我们能够监测甲烷和DOC从海底排出到海洋的运动，并限制甲烷渗漏处向海洋释放碳的过程。该项目将资助来自马里兰州社区学院和位于马萨诸塞州东南部低收入城市中心的一所学院的一名研究生和几名本科生。我们将通过一系列公共电视视频向公众传播项目调查结果。本研究将探讨甲烷衍生溶解有机碳（DOC）的生产，通量和反应性甲烷（CH4）渗漏在海伯林岭，近海俄勒冈州。本研究将解决四个基本问题，以确定在海洋碳循环中的重要性，甲烷衍生的DOC：（1）有多少甲烷衍生的化石DOC渗漏贡献给海洋？(2)在甲烷厌氧氧化过程中，甲烷衍生碳在多大程度上被纳入DOC？(3)渗漏DOC释放到深海中时是生物可利用的还是不可吸收的？(4)DOC到水柱的通量如何随时间变化？我们将采用跨学科的战略，包括原位取样，实验室孵化，和一个全面的分析地球化学计划。海波海脊南部海洋观测站倡议区域电缆阵列的数据将用于提供实地和实验数据的背景。有机和无机化学物种的组成和丰度沿着孔隙水、散装沉积物和水柱C池的稳定和放射性碳同位素组成，将用于识别DOC来源，并量化以平流率范围为特征的冷渗漏通量。调查的核心将是为期7天的海卫二脊研究巡航，收集沉积物，孔隙流体和水柱样本，并部署OsmoSampler进行连续的时间序列流体采样。该奖项反映了NSF的法定使命，并已被认为是值得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的支持。