海底冷泉和天然气水合物发育区向海洋释放甲烷是一种常见的自然过程，大部分渗漏甲烷在近海底沉积物中被甲烷缺氧氧化作用(AOM)所消耗，转化形成溶解无机碳(DIC)，形成的大部分DIC通过扩散和对流方式进入海洋，影响深海碳循环。然而，目前这种DIC进入海洋的通量及其对深海的影响并不清楚。本项目拟通过对南海北部冷泉和天然气水合物发育区近海底沉积物孔隙水地球化学进行模拟研究，定量计算冷泉和天然气水合物区海底界面释放的甲烷、溶解有机碳(DOC)和DIC的通量，确定渗漏甲烷在海底浅表层沉积物中的碳循环过程，评估海底冷泉和天然气水合物分解释放甲烷对南海深部碳库的影响，深化对整个南海碳循环系统的认识。该研究将有助于认识现今海底天然气水合物分解和冷泉活动对深海碳库的影响，为探索地质历史时期天然气水合物分解和冷泉活动对海洋碳库的影响提供重要参考。

Methane release is widespread natural process at hydrocarbon seeps and gas hydrate-occurred areas. The releasing methane is mainly consumed by the anaerobic oxidation of methane (AOM) before reaching the seafloor. The abundant dissolved inorganic carbon (DIC) produced by AOM mainly enters the ocean via diffusion and/or advection and possibly plays a role in deep-sea carbon cycling. However, the fluxes and influence of the AOM-derived DIC on the deep ocean are poorly constrained. This proposed study combines pore water geochemistry and numerical simulation to investigate the carbon cycling in the subsurface sediments at hydrocarbon seeps and gas hydrate-occurred areas, the northern South China Sea (SCS). Our aim is to calculate the benthic fluxes of methane, dissolved organic carbon (DOC), and DIC at hydrocarbon seeps and gas hydrate-occurred areas, to quantify methane turnover in the near bottom sediments, to evaluate their impacts on the deep-water carbon reservoir, and to improve our understanding of the carbon cycling at the SCS. This proposal would help to assess the influence of gas hydrate dissociation and submarine seeps on the carbon reservoir of the modern ocean, and to provide important clues to explore their influence from methane release at hydrocarbon seeps and gas hydrate dissociation on the ocean carbon reservoir in the geologic history.