The slow hydration / de-hydration kinetics of carbon dioxide at ambient temperatures and pressures are well known to ocean chemists.  Johnson (1982) reported the rate constant for the hydration reaction in seawater as a function of temperature.  More recently, Zeebe and Wolf-Gladrow (2001), have compiled a comprehensive model of these kinetics, which illustrate the strong impact of pH on reaction rate in addition to the temperature effects.  In our recent studies of CO2 dissolution in seawater as part of an ocean CO2 sequestration scenario, we have observed a significant under-estimation of the total CO2 concentrations when pH alone is used in close proximity to the CO2 source.  We attribute this under-estimation of total CO2 to slow CO2 hydration kinetics which allows a major fraction of the dissolved CO2 to remain unreacted until long after it has passed by the pH electrode and hence is undetectable.  For similar reasons, we anticipate analogous errors when measuring the total CO2 concentrations at close proximity to sea-floor CO2 vents on the flanks of undersea volcanoes.  More recently, measurements of CO2 hydration kinetics at low temperature but elevated pressures (such as would be encountered at these liquid CO2 sequestration sites or CO2 vents on the flanks of seafloor volcanoes), have suggested that pressure may be inducing slightly enhanced reaction rates which could partially mitigate the problem.  In order to test this hypothesis, we have begun a systematic study of CO2 hydration rates in the deep ocean using MBARI's advanced ROV technology.