Measurement of inorganic carbon and photosynthesis in seawater by pCO2 and pH analysis

An infrared carbon dioxide analyzer was used to measure the pCO2 of air in equilibrium with seawater. From the pCO2 and pH of the seawater, the amount of bicarbonate plus carbonate ion could be calculated. These values were also obtained by acidifying the seawater and measuring the amount of carbon dioxide that was released. These methods provide accurate measurements of the concentrations of inorganic carbon which are available for photosynthesis by marine plants. For example, these techniques showed that Iridaea cordatum used bicarbonate ion rather than CO2 during photosynthesis at high pH.