Carbonate Chemistry and pH Measurement in Marine Systems

The marine carbonate system comprises a network of chemical equilibria among dissolved inorganic carbon species—including carbon dioxide, bicarbonate and carbonate ions—and is buffered by total alkalinity. Accurate determination of pH and related parameters such as total alkalinity, dissolved inorganic carbon and partial pressure of CO₂ is fundamental to quantifying oceanic uptake of anthropogenic CO₂, assessing ocean acidification trends, and predicting impacts on marine ecosystems. A range of techniques has been developed, from conventional glass electrodes and spectrophotometric indicator methods to advanced optodes, ion-sensitive field-effect transistors and lab-on-chip sensors. Recent progress in autonomous and high-precision platforms allows continuous measurements across spatial and temporal scales, enabling more detailed mapping of pH variability in both open ocean and coastal environments. These advances underpin global monitoring networks and support model validation, informing policy on carbon emissions, conservation of calcifying organisms and resource management in fisheries and aquaculture.

Research from Nature Portfolio

No recent Nature Portfolio content available.

Carbonate Chemistry and pH Measurement in Marine Systems publication trend

The graph below shows the total number of articles in carbonate chemistry and ph measurement in marine systems across all publications each year (not limited to Nature Index journals).

Technical terms

pH: Logarithmic measure of hydrogen ion activity indicating acidity or alkalinity of seawater.

Total Alkalinity (TA): Sum of bases in seawater that buffer acid inputs, primarily bicarbonate and carbonate ions.

Dissolved Inorganic Carbon (DIC): Total concentration of CO₂, bicarbonate and carbonate species in solution.

Partial Pressure of CO₂ (pCO₂): Effective concentration of CO₂ gas equilibrated with seawater, driving air–sea exchange.

Aragonite Saturation State (ΩAr): Ratio indicating the tendency for calcium carbonate mineral aragonite to precipitate or dissolve.

Ion-Sensitive Field-Effect Transistor (ISFET): Solid-state sensor that converts changes in hydrogen ion activity to an electrical signal for pH measurement.

References

1. Technology for Ocean Acidification Research: Needs and Availability. Oceanography (2015).
2. Observing Changes in Ocean Carbonate Chemistry: Our Autonomous Future. Current Climate Change Reports (2019).
3. New Capability in Autonomous Ocean Carbon Observations Using the Autosub Long-Range AUV Equipped with Novel pH and Total Alkalinity Sensors. Environmental Science and Technology (2025).
4. PyCO2SYS v1.8: marine carbonate system calculations in Python. Geoscientific Model Development (2022).
5. The Development and Validation of a Profiling Glider Deep ISFET-Based pH Sensor for High Resolution Observations of Coastal and Ocean Acidification. Frontiers in Marine Science (2019).