PDF(Pubmed)
Abstract：
Coastal environments are a major source of marine methane in the atmosphere. Eutrophication and deoxygenation have the potential to amplify the coastal methane emissions. Here, we investigate methane dynamics in the eutrophic Stockholm Archipelago. We cover a range of sites with contrasting water column redox conditions and rates of organic matter degradation, with the latter reflected by the depth of the sulfate-methane transition zone (SMTZ) in the sediment. We find the highest benthic release of methane (2.2-8.6 mmol m-2 d-1) at sites where the SMTZ is located close to the sediment-water interface (2-10 cm). A large proportion of methane is removed in the water column via aerobic or anaerobic microbial pathways. At many locations, water column methane is highly depleted in 13C, pointing toward substantial bubble dissolution. Calculated and measured rates of methane release to the atmosphere range from 0.03 to 0.4 mmol m-2 d-1 and from 0.1 to 1.7 mmol m-2 d-1, respectively, with the highest fluxes at locations with a shallow SMTZ and anoxic and sulfidic bottom waters. Taken together, our results show that sites suffering most from both eutrophication and deoxygenation are hotspots of coastal marine methane emissions.
摘要：
沿海环境是大气中海洋甲烷的主要来源。富营养化和脱氧有可能扩大沿海甲烷的排放。这里,我们研究了富营养化的斯德哥尔摩群岛中的甲烷动力学。我们涵盖了一系列具有对比水柱氧化还原条件和有机物降解速率的场所，后者反映在沉积物中硫酸盐-甲烷过渡区（SMTZ）的深度上。在SMTZ靠近沉积物-水界面（2-10厘米）的位置，我们发现甲烷的底栖释放量最高（2.2-8.6mmolm-2d-1）。通过需氧或厌氧微生物途径在水柱中除去大部分甲烷。在许多地方,水柱甲烷在13C中高度枯竭，指向大量的气泡溶解。甲烷释放到大气中的计算速率和测量速率分别为0.03至0.4mmolm-2d-1和0.1至1.7mmolm-2d-1，在浅层SMTZ和缺氧和硫化底水的位置通量最高。一起来看,我们的结果表明，富营养化和脱氧最严重的地点是沿海海洋甲烷排放的热点地区。
