We investigate the uppermost 60 cm of sediment in active pockmarks of a deep-water methane seep site from Vestnesa Ridge offshore NW Svalbard. Using video guided core sampling with a remotely operated vehicle we collected push cores directly from bacterial mats within two active pockmarks, Lunde and Lomvi. Pore water analyses show very shallow sulphate methane transition zones and transport-reaction modelling suggests a considerable amount of dissolved methane passing through the sediment water interface due to upwards advection of an aqueous fluid not previously reported from Vestnesa Ridge. In addition, we show that the amount of methane that bypasses the benthic methane filter greatly increases with higher aqueous fluid advection rate. Recent changes in methane flux are evident from lipid biomarker, seep carbonate, and δ¹³C-organic carbon profiles in both pockmarks. Hydrocarbons at this cold seep site are supplied both by deep thermogenic sources from below the gas hydrate stability zone but also to a significant degree by microbial methanogenesis which dominates the signature in our shallow sediment cores with δ¹³C–CH₄ values as low as −77‰.

我们调查了西北西北部斯瓦尔巴特群岛Vestnesa Ridge的深水甲烷渗漏点的活动麻点中最高的60 cm沉积物。使用带遥控车辆的视频引导岩心采样，我们直接从两个活动麻点Lunde和Lomvi中的细菌垫上收集了推核。孔隙水分析显示出很浅的硫酸盐甲烷过渡带，传输反应模型表明大量溶解的甲烷通过沉积物水界面，这是因为以前没有从Vestnesa Ridge报道的含水流体向上对流。此外，我们显示绕过底栖甲烷过滤器的甲烷量随着较高的含水流体对流速率而大大增加。甲烷通量的最新变化从脂质生物标志物，渗碳碳酸盐和δ可见一斑。两个麻点中的¹³ C-有机碳轮廓。在此冷泉站点烃从天然气水合物稳定区的下方供给既通过深产热源而且还通过微生物甲烷一个显著程度这在我们的浅占主导地位的签名沉积物岩心与δ ¹³ C-CH _4个值低- 77‰。