Super-cutting-edge Grand and Advanced Research (SUGAR) Program, Institute for Extra-cutting-edge Science and Technology Avant-garde Research (X-STAR), Japan Agency for Marine-Earth Science and Technology (JAMSTEC).
Marine Biodiversity and Environmental Assessment Research Center (BioEnv), Research Institute for Global Change (RIGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC).
Microbes Environ. 2023;38(2). doi: 10.1264/jsme2.ME22108.
Post-mega-earthquake geochemical and microbiological properties in subseafloor sediments of the Japan Trench accretionary wedge were investigated using core samples from Hole C0019E, which was drilled down to 851 m below seafloor (mbsf) at a water depth of 6,890 m. Methane was abundant throughout accretionary prism sediments; however, its concentration decreased close to the plate boundary decollement. Methane isotope systematics indicated a biogenic origin. The content of mole-cular hydrogen (H) was low throughout core samples, but markedly increased at specific depths that were close to potential faults predicted by logging-while-drilling ana-lyses. Based on isotopic systematics, H appeared to have been abundantly produced via a low-temperature interaction between pore water and the fresh surface of crushed rock induced by earthquakes. Subseafloor microbial cell density remained constant at approximately 10 cells mL. Amplicon sequences revealed that predominant members at the phylum level were common throughout the units tested, which also included members frequently found in anoxic subseafloor sediments. Metabolic potential assays using radioactive isotopes as tracers revealed homoacetogenic activity in H-enriched core samples collected near the fault. Furthermore, homoacetogenic bacteria, including Acetobacterium carbinolicum, were isolated from similar samples. Therefore, post-earthquake subseafloor microbial communities in the Japan Trench accretionary prism appear to be episodically dominated by homoacetogenic populations and potentially function due to the earthquake-induced low-temperature generation of H. These post-earthquake microbial communities may eventually return to the steady-state communities dominated by oligotrophic heterotrophs and hydrogenotrophic and methylotrophic methanogens that are dependent on refractory organic matter in the sediment.
对日本海沟俯冲楔形物海底以下沉积物进行了后特大地震地球化学和微生物特性研究，使用了在水深 6890 米、海底以下 851 米处钻取的 C0019E 岩芯。整个增生楔沉积物中都富含甲烷，但在接近板块边界滑脱面的地方浓度降低。甲烷同位素系统表明其具有生物成因。整个岩芯样品中的分子氢（H）含量都较低，但在与测井分析预测的潜在断层接近的特定深度处明显增加。根据同位素系统，H 似乎是通过地震引起的孔隙水与新鲜破碎岩石表面之间的低温相互作用大量产生的。海底微生物细胞密度基本保持在 10 个细胞/ml 左右。扩增子序列表明，在测试的各个单元中，优势门水平的成员是常见的，其中还包括在缺氧海底沉积物中经常发现的成员。使用放射性同位素作为示踪剂的代谢潜力测定表明，在靠近断层的富含 H 的岩芯样品中存在同型产乙酸菌活性。此外，还从类似的样品中分离到了同型产乙酸菌，包括醋杆菌属（Acetobacterium carbinolicum）。因此，日本海沟俯冲增生楔中的地震后海底微生物群落似乎会间歇性地被同型产乙酸菌群落主导，并可能由于地震引起的低温产生 H 而发挥作用。这些地震后的微生物群落最终可能会回到以沉积物中难降解有机物为基础的寡营养异养菌和氢营养型及甲基营养型产甲烷菌为主导的稳定态群落。
