Microbial Ecology of Deep Subsea Sediments
Summary
Deep subsea sediments harbour a vast and dynamic biosphere in which microorganisms persist under high pressure, low temperature and extreme energy limitation. These communities occupy stratified layers that range from organic-rich surface muds to deeply buried, oligotrophic clay- and carbonate-rich horizons. Within these layers, diverse bacteria and archaea carry out key biogeochemical transformations, including anaerobic oxidation of methane, sulphate reduction, fermentation and metal cycling. Microbial activity is closely coupled to sediment porewater chemistry and mineralogy, with gradients of electron donors and acceptors determining community composition and metabolic pathways. In many settings, chemolithoautotrophic microbes fix CO₂ using energy from hydrogen, reduced sulphur species or iron, forming the base of subsurface food webs. Other taxa derive energy from the breakdown of organic matter delivered by marine snow or advected from continental margins. Recent advances in high-resolution sediment coring, in situ geochemical sensors and community metagenomics have revealed unexpected metabolic versatility, the presence of novel candidate phyla and extreme longevity of deep subsurface cells. These findings extend our understanding of the global carbon cycle, as deep sediments can act both as sinks for organic carbon and as sources of greenhouse gases. Improved knowledge of subsea microbial processes also informs strategies for bioremediation, hydrocarbon recovery and assessment of subseafloor mineral stability in response to climate change and deep-sea mining activities.
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Microbial Ecology of Deep Subsea Sediments publication trend
The graph below shows the total number of articles in microbial ecology of deep subsea sediments across all publications each year (not limited to Nature Index journals).
Technical terms
Sub-seafloor biosphere: The ecosystem of microorganisms living within sediments beneath the ocean floor.
Chemolithoautotrophy: Metabolism in which microbes obtain energy by oxidising inorganic compounds and fix carbon dioxide as a carbon source.
Turbidite: A deposit formed by sediment-laden currents flowing down continental slopes, carrying particles and microbes into deep basins.
Hadal trenches: The deepest parts of the ocean (>6,000 m), characterised by high pressure, low temperatures and unique microbial communities.
Metagenomics: Analysis of collective genetic material from environmental samples to characterise community composition and metabolic potential.
References
- A review of prokaryotic populations and processes in sub-seafloor sediments, including biosphere:geosphere interactions. Marine Geology (2014).
- Earthquake-induced redistribution and reburial of microbes in the hadal trenches. The Innovation Geoscience (2023).
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