Ocean Acidification - Category 1: Calibration and Application of the Boron Isotope Seawater-pH Indicator in Deep-water Corals
DESCRIPTION: This project funded the validation of boron isotopes, trace metal composition and stable isotopes in deep-sea corals from museum collections, and their application to quantify ocean acidification in recent history.
OUTCOMES: GRA Jesse Farmer calibrated modern specimens for the boron isotope/pH proxy and found that surface skeleton samples broadly correlate with pH as expected from the theoretical basis of the boron isotope proxy. However, intra-skeletal B isotope variability is larger than can be explained by seawater-pH variations alone, hinting at significant vital effects that preclude direct reconstruction of anthropogenic ocean acidification. Complementary carbon and oxygen isotopes are correlated, which supports the presence of kinetic/pH vital effects, which may be the cause of the observed boron isotope variability. Although the main goal of quantifying anthropogenic ocean acidification was not achieved with these corals, the B isotope results provide a new and important dataset for refining the interpretation of the boron isotope pH proxy in corals.