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<p>Methane released from the subseafloor is significantly attenuated during upward migration, yet the preservation of methane-derived organic carbon (OC) in global deep-sea sediments remains poorly understood. Here, we measured carbon isotopes coupled with temperature-ramped analyses on various methane seepage sediments. Our results reveal a correlation between the radiocarbon (<sup>14</sup>C) content in deep-sea surface sediments and sulfate-methane transition depth. Notably, our findings suggest that a substantial amount of <sup>14</sup>C-depleted OC may originate from deep-seated methane and is efficiently preserved in surface seepage sediments. We propose that the&#xa0;efficient OC preservation is related to microbial-mediated aggregate formation at the seawater-sediment interface, where physical occlusion within coarse-grained matrices reduces oxygen availability and enhances OC stability. We estimate that at least 6 Tg&#xa0;C of methane-derived OC are preserved annually in surface sediments of the global continental slopes. This process may play a non-negligible role in OC preservation in sediments, reducing methane emission into the atmosphere.</p>

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Efficient preservation of old methane-derived organic carbon in deep-sea surface sediments

  • 期刊论文

  • 出版模式：

    开放获取

  • 发表日期：

    2026年6月17日

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  • Rui Bao,
  • Yangli Che,
  • Mingzhi Liu,
  • Naiyu Zhang,
  • Yang Zhou,
  • Lihua Dong,
  • Shen Li,
  • Owen A. Sherwood,
  • Min Yu,
  • Zongheng Chen,
  • Shengxiong Yang,
  • Nan Wang,
  • Longhai Zhu,
  • Jiawang Chen,
  • Mutai Bao,
  • Haoshuai Li,
  • Luonan Chen,
  • Weifeng Wu,
  • Haiyue Ma,
  • David J. Burdige

摘要

Methane released from the subseafloor is significantly attenuated during upward migration, yet the preservation of methane-derived organic carbon (OC) in global deep-sea sediments remains poorly understood. Here, we measured carbon isotopes coupled with temperature-ramped analyses on various methane seepage sediments. Our results reveal a correlation between the radiocarbon (14C) content in deep-sea surface sediments and sulfate-methane transition depth. Notably, our findings suggest that a substantial amount of 14C-depleted OC may originate from deep-seated methane and is efficiently preserved in surface seepage sediments. We propose that the efficient OC preservation is related to microbial-mediated aggregate formation at the seawater-sediment interface, where physical occlusion within coarse-grained matrices reduces oxygen availability and enhances OC stability. We estimate that at least 6 Tg C of methane-derived OC are preserved annually in surface sediments of the global continental slopes. This process may play a non-negligible role in OC preservation in sediments, reducing methane emission into the atmosphere.