Abstract Concentrations of total dissolved inorganic carbon (DIC) in freshwater ecosystems are controlled by terrestrial inputs and a myriad of in situ processes, such as aquatic metabolism. Dissolved CO 2 is one of the components of DIC, and its dynamics are also regulated by chemical equilibrium with the DIC pool, so‐called carbonate buffering. Although its importance is generally recognized, carbonate buffering is still not consistently accounted for in freshwater studies. Here, we review key concepts in freshwater carbonate buffering, perform simulation experiments, and provide a case study of an alkaline river to illustrate calculations of DIC from CO 2 . These analyses demonstrate that carbonate buffering can alter common interpretations of CO 2 data, including carbon–oxygen coupling through production and respiration. As direct measurements of dissolved CO 2 are increasingly common, accounting for CO 2 equilibria with DIC is critical to understanding its role in carbon cycling within most freshwater systems.
Shangguan et al. (2025) studied this question.