Sclerosponge as archive of pCO2 in the past oceans

Sclerosponges produce calcareous skeletons. In this study, we examined whether the chemical composition of sclerosponge skeletons (boron concentration and isotope ratios) reflects seawater pH and carbonate ion concentration. As a result, pH estimated from the boron isotope ratio was nearly consistent with seawater pH, suggesting that sclerosponge can be utilized as a new archive of seawater pH. However, the carbonate ion concentration estimated by boron concentration and isotope ratios was higher than seawater value, indicating that it is difficult to estimate carbonate ion concentration based on sclerosponges.