A unique subseafloor microbiosphere in the Mariana Trench driven by episodic sedimentation

Jiwen Liu, Da-Wei Li, Xinxin He, Ronghua Liu, Haojin Cheng, Chenglong Su, Mengna Chen, Yonghong Wang, Zhongsheng Zhao, Hanyue Xu, Zhangyu Cheng, Zicheng Wang, Nikolai Pedentchouk, David J. Lea-Smith, Jonathan D. Todd, Xiaoshou Liu, Meixun Zhao, Xiao-Hua Zhang

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Abstract

Hadal trenches are characterized by enhanced and infrequent high-rate episodic sedimentation events that likely introduce not only labile organic carbon and key nutrients but also new microbes that significantly alter the subseafloor microbiosphere. Currently, the role of high-rate episodic sedimentation in controlling the composition of the hadal subseafloor microbiosphere is unknown. Here, analyses of carbon isotope composition in a ~ 750 cm long sediment core from the Challenger Deep revealed noncontinuous deposition, with anomalous 14C ages likely caused by seismically driven mass transport and the funneling effect of trench geomorphology. Microbial community composition and diverse enzyme activities in the upper ~ 27 cm differed from those at lower depths, probably due to sudden sediment deposition and differences in redox condition and organic matter availability. At lower depths, microbial population numbers, and composition remained relatively constant, except at some discrete depths with altered enzyme activity and microbial phyla abundance, possibly due to additional sudden sedimentation events of different magnitude. Evidence is provided of a unique role for high-rate episodic sedimentation events in controlling the subsurface microbiosphere in Earth’s deepest ocean floor and highlight the need to perform thorough analysis over a large depth range to characterize hadal benthic populations. Such depositional processes are likely crucial in shaping deep-water geochemical environments and thereby the deep subseafloor biosphere.

Original languageEnglish
Pages (from-to)168-181
Number of pages14
JournalMarine Life Science and Technology
Volume6
Issue number1
Early online date23 Jan 2024
DOIs
Publication statusPublished - Feb 2024

Keywords

  • Deep water sediment
  • Hadal subseafloor
  • Mariana Trench
  • Microbial community
  • Radiocarbon
  • Redox potential

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