Carbon Dynamics in Marine and Terrestrial Systems

Carbon in the terrestrial and marine realms circulates through interconnected reservoirs, including the atmosphere, vegetation, soils, rivers, continental shelves and deep-sea sediments. On land, photosynthetic uptake by plants converts atmospheric carbon dioxide into organic carbon stored in biomass and soils. Erosion, runoff and fluvial transport mobilise a portion of this material into river networks, where oxidation and sedimentation processes determine whether it returns rapidly to the atmosphere or is preserved for longer timescales. In the coastal zone, riverine carbon meets marine production, and the balance between biological uptake, remineralisation and burial in continental margin sediments shapes the ocean’s role as a long-term carbon sink. Hydrodynamic sorting, mineral protection and microbial degradation mediate the retention or release of carbon across diverse environments. Continental shelves and fjords accumulate large stocks of organic and inorganic carbon, while deep-sea sediments act as the ultimate long-term repository. Understanding these processes and their sensitivity to climatic variability, land-use change and human management is essential for predicting feedbacks in the global carbon cycle and informing mitigation strategies.

Research from Nature Portfolio

Recent studies have quantified how fluvial transit time and mineral association regulate particulate organic carbon (POC) oxidation and preservation during river transport. Using field measurements and simple turnover models, researchers demonstrated that longer sediment transit enhances POC oxidation but that attachment to mineral surfaces reduces degradation rates, thereby influencing the net carbon flux delivered to depositional sinks. The work also highlights how lateral erosion into floodplains can augment downstream POC export, suggesting that river management practices which stabilise channels may inadvertently reduce carbon drawdown potential. In a foundational contribution, bomb-radiocarbon tracers applied to leaf-wax biomarkers revealed that a large fraction of terrestrial organic matter can reside in continental reservoirs for millennia before reaching the marine record. This age structure not only distorts high-resolution palaeoenvironmental reconstructions but also indicates the existence of vast, reactive carbon stocks whose release could accelerate under future environmental change.

Carbon Dynamics in Marine and Terrestrial Systems publication trend

The graph below shows the total number of articles in carbon dynamics in marine and terrestrial systems across all publications each year (not limited to Nature Index journals).

Technical terms

Organic carbon (OC): Carbon bound within organic compounds derived from living or once-living organisms.

Particulate organic carbon (POC): Solid organic carbon particles transported in suspension by water or wind.

Hyperpycnal flow: A river discharge denser than ambient seawater, forming a turbidity current that rapidly transports sediment and organic matter into deep marine settings.

Radiocarbon (14C): A radioactive isotope of carbon used to determine the age and residence time of organic material.

Hydrodynamic sorting: The process by which flowing water segregates particles by size, shape or density, influencing sediment composition and associated carbon content.

References

1. The Modern Ocean Sediment Archive and Inventory of Carbon (MOSAIC): version 2.0. Earth System Science Data (2023).
2. Fluvial organic carbon cycling regulated by sediment transit time and mineral protection. Nature Geoscience (2021).
3. Millennial soil retention of terrestrial organic matter deposited in the Bengal Fan. Scientific Reports (2018).
4. Controls on the abundance, provenance and age of organic carbon buried in continental margin sediments. Earth and Planetary Science Letters (2021).
5. Marine Sedimentary Carbon Stocks of the United Kingdom’s Exclusive Economic Zone. Frontiers in Earth Science (2021).