Vertically distinct microbial communities in the Mariana and Kermadec trenches

Area of Science:

• Marine microbiology
• Deep-sea ecology
• Oceanography

Background:

• Hadal trenches (>6,000 m) are hypothesized to harbor distinct microbial communities.
• Factors like high pressure, organic matter funneling, and isolation may drive this uniqueness.
• Previous studies suggest hadal zones harbor unique biodiversity.

Purpose of the Study:

• To test the hypothesis of unique microbial biodiversity in hadal trenches.
• To analyze microbial communities in the bottom waters of the Kermadec and Mariana trenches.
• To understand the drivers of microbial community structure in deep-sea trenches.

Main Methods:

• Analysis of microbial communities in bottom water samples from two hadal trenches.
• Estimation of microbial protein production to assess activity under pressure.
• Investigation of growth and survival of isolates under simulated deep-sea conditions.

Main Results:

• Microbial protein production indicates active populations adapting to hydrostatic pressure with increasing depth.
• Microbial community structure is significantly influenced by depth, trench of collection, and size fraction.
• Identified cosmopolitan hadal taxa (e.g., Marinimicrobia, Rhodobacteraceae) and ubiquitous genera.
• Gammaproteobacteria differences between trenches suggest some may originate from shallower waters.

Conclusions:

• Hadal trench microbiomes are shaped by both specialized hadal taxa and ubiquitous surface-related genera.
• Evidence suggests some microbial taxa may exist as inactive fractions in the hadal zone.
• The study highlights the complex interplay of factors structuring deep-sea microbial communities.