Carbon Cycling in Coastal Marine Systems

Coastal marine systems occupy the dynamic interface between land, atmosphere and open ocean, driving significant exchanges of carbon. In these regions, rivers deliver terrestrial organic and inorganic carbon that fuels primary production, while physical processes such as upwelling and mixing redistribute nutrients and dissolved inorganic carbon (DIC). Phytoplankton convert DIC into organic matter, supporting food webs and sequestering carbon in biomass. Respiration, decomposition and air–sea gas exchange return a portion of this carbon to the atmosphere or deeper ocean layers. Estuarine and continental shelf environments often exhibit pronounced seasonal shifts in carbon fluxes driven by temperature, wind, nutrient delivery and anthropogenic inputs. Coastal sediments can act as long-term carbon sinks, yet perturbations such as eutrophication, ocean acidification and deoxygenation alter the balance between sources and sinks. Understanding the mechanisms governing coastal carbon cycling is essential for accurate global carbon budgets and for informing management strategies aimed at mitigating climate change impacts.

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Carbon Cycling in Coastal Marine Systems publication trend

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

Technical terms

Partial pressure of CO₂ (pCO₂): The concentration of carbon dioxide in seawater expressed as a pressure, used to assess air–sea exchange potential.

Dissolved inorganic carbon (DIC): All inorganic carbon species in water (CO₂, bicarbonate and carbonate ions) available for biological and chemical processes.

Net primary production: The rate at which photosynthetic organisms convert inorganic carbon into organic matter, minus respiratory losses.

Eutrophication: Enrichment of water by nutrients, often from terrestrial runoff, that stimulates excessive primary production and can alter carbon fluxes.

Upwelling: The upward movement of deep, nutrient-rich water to the surface, influencing local carbon and nutrient dynamics.

Air–sea gas exchange: The diffusion of gases such as CO₂ across the interface between the atmosphere and ocean, controlled by concentration gradients and physical conditions.

References

1. Diagnosis of CO2 dynamics and fluxes in global coastal oceans. National Science Review (2019).
2. Spatiotemporal Evolution of Air–Sea CO2 Flux in the South China Sea and Its Response to Environmental Factors. Remote Sensing (2024).
3. Seamounts Enhance the Local Emission of CO2 in the Northern South China Sea. Geophysical Research Letters (2024).