Ocean Acidification Dynamics and Coastal Biogeochemistry

Ocean acidification arises from the uptake of anthropogenic CO₂ by seawater, causing shifts in carbonate chemistry that lower pH and reduce the saturation state of calcium carbonate minerals. In coastal zones, this process is modulated by river–ocean exchanges, upwelling of nutrient-rich waters, redox reactions in sediments and biological production and remineralisation. The buffering capacity of seawater hinges on total alkalinity, which in turn is influenced by weathering inputs, carbonate dissolution and biogeochemical cycling. Complex interactions between physical mixing, nutrient fluxes and acid–base chemistry give rise to spatiotemporal variability in pH, dissolved inorganic carbon and mineral saturation, with pronounced seasonal and depth-dependent patterns. These changes affect calcifying organisms, alter trace metal availability and can exacerbate hypoxia, thereby reshaping coastal ecosystems and the services they deliver to human societies.

Research from Nature Portfolio

Long-term observational studies have yielded one of the longest continuous records of coastal acidification to date, revealing a steady decline in surface pH at a subtropical eastern boundary current site over 37 years. Seasonal temperature and inorganic carbon cycles were found to imprint a distinct annual rhythm on pH, while proximity to upwelling zones modulates CO₂ uptake rates, highlighting regional deviations from global model predictions. Advances in high-resolution climatologies have combined extensive CO₂ observations with Earth system models to reconstruct surface pH and Revelle factor trends from pre-industrial times to future scenarios. This work has uncovered pronounced geographic differences in buffer capacity and projections of aragonite saturation trajectories, thereby refining regional adaptation strategies. In estuarine waters, synergistic interactions between nutrient-driven hypoxia, redox chemistry and weak buffering have been shown to generate mid-depth pH minima, intensifying acidification and carbonate dissolution in large bay systems.

Ocean Acidification Dynamics and Coastal Biogeochemistry publication trend

The graph below shows the total number of articles in ocean acidification dynamics and coastal biogeochemistry across all publications each year (not limited to Nature Index journals).

Technical terms

pH: Negative logarithm of hydrogen ion activity, indicating seawater acidity.

Total alkalinity (TA): Sum of proton-accepting ions in seawater that buffer against pH change.

Dissolved inorganic carbon (DIC): Combined concentration of aqueous CO₂, bicarbonate and carbonate ions.

Aragonite saturation state (Ωarag): Ratio of carbonate ion concentration to its solubility product, indicating calcification potential.

Revelle factor: Sensitivity of CO₂ uptake to changes in DIC, reflecting buffer capacity.

Upwelling: Wind-driven ascent of deep, nutrient-rich, low-pH water to the surface.

References

1. A decade-long cruise time series (2008–2018) of physical and biogeochemical conditions in the southern Salish Sea, North America. Earth System Science Data (2024).
2. A 37-year record of ocean acidification in the Southern California current. Communications Earth & Environment (2023).
3. Surface ocean pH and buffer capacity: past, present and future. Scientific Reports (2019).
4. Redox reactions and weak buffering capacity lead to acidification in the Chesapeake Bay. Nature Communications (2017).
5. Amplified Subsurface Signals of Ocean Acidification. Global Biogeochemical Cycles (2023).
6. Physiological responses of scallops and mussels to environmental variability: Implications for future shellfish aquaculture. Marine Pollution Bulletin (2023).