Potential ecotoxicological effects of elevated bicarbonate ion concentrations on marine organisms

Recently, a novel method for carbon capture and storage has been proposed, which converts gaseous CO₂ into aqueous bicarbonate ions (HCO₃^-), allowing it to be deposited into the ocean. This alkalinization method could be used to dispose large amounts of CO₂ without acidifying seawater pH, but there is no information on the potential adverse effects of consequently elevated HCO₃^- concentrations on marine organisms. In this study, we evaluated the ecotoxicological effects of elevated concentrations of dissolved inorganic carbon (DIC) (max 193 mM) on 10 marine organisms. We found species-specific ecotoxicological effects of elevated DIC on marine organisms, with EC50-DIC (causing 50% inhibition) of 11-85 mM. The tentative criteria for protecting 80% of individuals of marine organisms are suggested to be pH 7.8 and 11 mM DIC, based on acidification data previously documented and alkalinization data newly obtained from this study. Overall, the results of this study are useful for providing baseline information on ecotoxicological effects of elevated DIC on marine organisms. More complementary studies are needed on the alkalinization method to determine DIC effects on seawater chemistry and marine organisms.