Carbon dioxide stripping in aquaculture. Part 1: Terminology and reporting

The removal of carbon dioxide gas in aquacultural systems is much more complex than for oxygen or nitrogen gas because of liquid reactions of carbon dioxide and their kinetics. Almost all published carbon dioxide removal information for aquaculture is based on the apparent removal value after the CO2(aq) + HOH ⇔ H2CO3 reaction has reached equilibrium. The true carbon dioxide removal is larger than the apparent value, especially for high alkalinities and seawater. For low alkalinity freshwaters (<2000 μeq/kg), the difference between the true and apparent removal is small and can be ignored for many applications. Analytical and reporting standards are recommended to improve our understanding of carbon dioxide removal.

► The true CO2 removal rate is equal to the decrease in total carbonate concentration.
► The apparent removal rate is equal to the decrease in CO2 after re-equilibration.
► The true removal is larger for high alkalinities and seawater.
► The difference between the two removals is small for low alkalinities in freshwater.