Wallenius Anna J, Venetz Jessica, Zygadlowska Olga M, Lenstra Wytze K, van Helmond Niels A G M, Dalcin Martins Paula, Slomp Caroline P, Jetten Mike S M
Department of Microbiology, Radboud Institute for Biological and Environmental Sciences, Radboud University, 6525 AJ Nijmegen, The Netherlands.
Department of Earth Sciences - Geochemistry, Utrecht University, 3508 TA Utrecht, The Netherlands.
FEMS Microbiol Ecol. 2025 Jul 14;101(8). doi: 10.1093/femsec/fiaf075.
Coastal areas contribute over 75% of global marine methane emissions, a proportion predicted to increase with anthropogenic eutrophication and deoxygenation. Prolonged low oxygen and high organic matter input can disrupt the methane cycle, favoring methane production over oxidation. However, factors influencing this imbalance remain unclear. Here, we show that methanogenesis dominates microbial methane cycling in the anoxic sediments of eutrophic coastal marine Lake Grevelingen (The Netherlands) after summer stratification. A shallow sulfate-methane transition zone (SMTZ; 5-15 cm depth) was observed, with high methane concentrations below. Methane was produced in all investigated layers, while methane oxidation was restricted to the narrow SMTZ. Amplicon sequencing, metagenomics, and incubations revealed a metabolically and phylogenetically diverse methanogenic community with niche separation, and methylotrophic methanogenesis prevalent in all layers. Two clades of ANME archaea, ANME-2a/b and ANME-3, were restricted to a narrow zone together with their putative syntrophic sulfate-reducing bacteria, coinciding with the observed methane oxidation activity. Our results suggest that eutrophication and deoxygenation will further contribute to rising methane emissions, tilting the microbial methane cycle toward increased methanogenesis, and decreasing the efficiency of the microbial methane filter.
沿海地区贡献了全球海洋甲烷排放量的75%以上，预计这一比例会随着人为富营养化和脱氧作用而增加。长期的低氧和高有机物输入会扰乱甲烷循环，使甲烷生成超过氧化。然而，影响这种失衡的因素仍不明确。在这里，我们表明，在夏季分层后，荷兰富营养化沿海湖泊格雷夫林根湖的缺氧沉积物中，甲烷生成在微生物甲烷循环中占主导地位。观察到一个浅的硫酸盐-甲烷过渡带（SMTZ；深度5-15厘米），其下方甲烷浓度很高。在所有调查层中都有甲烷产生，而甲烷氧化仅限于狭窄的SMTZ。扩增子测序、宏基因组学和培养实验揭示了一个代谢和系统发育多样的产甲烷群落，具有生态位分离现象，且甲基营养型甲烷生成在所有层中普遍存在。两类厌氧甲烷氧化古菌，即ANME-2a/b和ANME-3，与其假定的共生硫酸盐还原细菌一起局限于一个狭窄区域，这与观察到的甲烷氧化活性相吻合。我们的结果表明，富营养化和脱氧作用将进一步导致甲烷排放量上升，使微生物甲烷循环倾向于增加甲烷生成，并降低微生物甲烷过滤效率。
