Microbial Community Diversity Within Sediments from Two Geographically Separated Hadal Trenches.

Area of Science:

• Marine microbiology
• Deep-sea ecology
• Biogeochemistry

Background:

• Hadal ocean sediments (>6,000m) harbor unique microbial communities influenced by extreme pressure and organic matter.
• Geographical isolation may lead to distinct microbial populations in different hadal trenches.
• Understanding hadal microbial biogeography is crucial for deep-sea ecosystem research.

Purpose of the Study:

• To compare microbial community composition in sediments from the Mariana and Kermadec trenches.
• To evaluate microbial biogeography and connectivity at hadal depths.
• To assess the impact of incubation conditions on microbial community representation.

Main Methods:

• Comparative analysis of microbial consortia in surficial sediments from two hadal trenches.
• DNA sequencing to determine microbial community composition.
• Microbial isolation and incubation under in situ pressures and static conditions.

Main Results:

• Sediment microbial communities were distinct between the Mariana and Kermadec trenches.
• Kermadec Trench sediments showed higher abundances of organic matter-degrading taxa.
• Mariana Trench and deeper sediments were enriched in taxa that break down recalcitrant material.
• Sequence-abundant taxa at 97% similarity were not trench-specific, indicating potential connectivity.
• Most isolates under in situ pressure were piezophiles, dominating incubated native sediments.

Conclusions:

• Hadal sediment microbial populations exhibit connectivity despite geographical isolation.
• Microbial communities and lineages vary significantly by trench and sediment depth.
• Current high-pressure incubation methods may not fully capture in situ microbial diversity and function.
• Revised protocols are needed for accurate study of high-pressure microbial ecosystems.