Benthic Biogeochemical Dynamics in Marine Sediments

Marine sediments host complex interactions among biological, chemical and physical processes that regulate the cycling of carbon, nutrients and trace elements at the seafloor. Microbial degradation of organic matter drives oxygen consumption and redox transitions while anaerobic pathways such as sulphate reduction, methanogenesis and denitrification become dominant in deeper layers. Variation in organic matter reactivity, sediment permeability and hydrodynamic forcing produces marked spatial and temporal heterogeneity. High-energy settings such as mega-rippled sands and hadal trenches exhibit intensified oxygen fluxes, reflecting rapid early diagenesis and benthic–pelagic coupling under contrasting productivity regimes. Continental margin and coastal sediments act as critical interfaces for nutrient regeneration and carbon burial, influencing global biogeochemical budgets, climate feedbacks and strategies for coastal management. Emerging high-resolution measurement techniques have revealed transient hypoxia and dynamic oxygen penetration not captured by conventional monitoring, underscoring the need to reconcile fine-scale processes with large-scale models of sedimentary diagenesis.

Research from Nature Portfolio

Recent studies have shown that the deepest oceanic trenches serve as dynamic hotspots for early diagenesis, with benthic oxygen uptake up to ten times higher than adjacent abyssal plains. Variability in respiratory activity reflects both surface productivity and local deposition of organic detritus, leading to a heterogeneous distribution of microbial remineralisation. These findings redefine the role of hadal environments in global carbon turnover and challenge previous assumptions of the deep sea as uniformly low in biogeochemical activity.

Benthic Biogeochemical Dynamics in Marine Sediments publication trend

The graph below shows the total number of articles in benthic biogeochemical dynamics in marine sediments across all publications each year (not limited to Nature Index journals).

Technical terms

Benthic: Pertaining to the lowest ecological region of a body of water, including the sediment surface and subsurface layers.

Diagenesis: The suite of physical, chemical and biological alterations that occur in sediments after their initial deposition.

Early diagenesis: Initial stages of diagenetic processes, often characterised by rapid microbial decomposition and redox shifts near the sediment–water interface.

Organic matter reactivity: The susceptibility of deposited organic compounds to microbial degradation under benthic conditions.

Diffusive oxygen uptake (DOU): The flux of dissolved oxygen from overlying water into sediments, driven by concentration gradients.

Hypoxia: A state of low dissolved oxygen concentration (<63 µmol L–1) in water or sediment porewaters, limiting aerobic processes.

Benthic–pelagic coupling: The exchange of nutrients, gases and organic matter between the water column and the ocean floor.

References

1. Regional and Global Patterns of Apparent Organic Matter Reactivity in Marine Sediments. Global Biogeochemical Cycles (2023).
2. Coastal marine megaripple fields are metabolic hotspots with highly dynamic oxygen exchange. Limnology and Oceanography Letters (2023).
3. Hidden seafloor hypoxia in coastal waters. Limnology and Oceanography (2024).
4. Sediment oxygen consumption: Role in the global marine carbon cycle. Earth-Science Reviews (2022).
5. Hadal trenches are dynamic hotspots for early diagenesis in the deep sea. Communications Earth & Environment (2021).
6. Modelling Marine Sediment Biogeochemistry: Current Knowledge Gaps, Challenges, and Some Methodological Advice for Advancement. Frontiers in Marine Science (2018).