Biogeochemistry of Sedimentary Organic Matter

Sedimentary organic matter forms the foundation of benthic food webs and constitutes a major reservoir in the global carbon cycle. This pool derives from a mixture of terrestrial plant debris, marine planktonic matter and in situ microbial synthesis. Following deposition, organic molecules undergo physical, chemical and biological alteration—collectively termed diagenesis—governed by factors such as redox state, sedimentation rate and mineral association. Labile compounds, including proteins and simple carbohydrates, are rapidly remineralised by bacteria and archaea, whereas more refractory fractions may persist for centuries. The interplay between organic inputs, microbial turnover and mineral protection controls the burial efficiency of carbon and modulates the cycling of nitrogen, phosphorus and trace elements. Understanding these processes is critical for predicting sedimentary responses to environmental change, for reconstructing past climates and for managing coastal and deep-sea ecosystems under anthropogenic pressure.

Research from Nature Portfolio

Recent studies have applied combined biochemical and sedimentological approaches to quantify spatial variability in organic matter composition. In central Indian Ocean sediment cores, measurements of total organic carbon alongside protein, carbohydrate and lipid contents reveal depth-dependent shifts in macromolecular assemblages. Protein fractions correlate positively with total organic carbon and negatively with lipid and carbohydrate pools, suggesting selective degradation pathways. Moreover, lipids show strong association with fine-grained clays, indicating a protective mineral-organic interaction that enhances preservation. Ratios of protein to carbohydrate exceed unity throughout much of the profile, implying sustained benthic productivity and the importance of organic-mineral binding in modulating long-term carbon burial.

Biogeochemistry of Sedimentary Organic Matter publication trend

The graph below shows the total number of articles in biogeochemistry of sedimentary organic matter across all publications each year (not limited to Nature Index journals).

Technical terms

Total organic carbon (TOC): The total amount of carbon bound in organic compounds within a sediment sample, often used as a measure of organic matter abundance.

Lability: The susceptibility of organic matter to biological breakdown and microbial utilisation, distinguishing readily degradable from more persistent fractions.

Biomarker: A molecular indicator, such as specific fatty acids or pigments, used to trace the source, transformation and fate of organic matter.

Diagenesis: The suite of physical, chemical and biological processes that alter sediments and their organic constituents after initial deposition.

Mineral-organic binding: The association of organic molecules with mineral surfaces, which can protect organic matter from enzymatic degradation and enhance long-term preservation.

References

1. Composition and vertical distribution of organic matter in Central Indian Ocean sediment cores. Scientific Reports (2024).
2. Distribution and lability of land-derived organic matter in the surface sediments of the Rhône prodelta and the adjacent shelf (Mediterranean Sea, France): a multi proxy study. Biogeosciences (2011).
3. Effects of Field Simulated Marine Heatwaves on Sedimentary Organic Matter Quantity, Biochemical Composition, and Degradation Rates. Biology (2022).
4. Biogeochemical and oceanographic conditions provide insights about current status of an Antarctic fjord affected by relatively slow glacial retreat. Anais da Academia Brasileira de Ciências (2023).