Monthly and annually proxy and growth parameter from a core of Porites australiensis from Lizard Island between 1938 - 2018

Here we address this question using seasonally and annually resolved boron proxies (11B/10B and B/Ca) of calcifying fluid (cf) pHcf and carbonate ion concentrations ([CO]cf) preserved in a long-lived Porites coral from the Great Barrier Reef (GBR).

From 1939 to 2013 we find that the coral pHcf closely followed the decline in seawater pH of ∼0.1 units, but at a reduced rate of ∼60%, indicative of biological buffering. Of the decline in pHcf ∼82% is attributed to OA and ∼17% to the ∼0.5 °C long-term warming observed over this period. This long-term warming induced change in pHcf is consistent with the much larger seasonally modulated changes in pHcf where ∼4 to 6 °C seasonal changes in temperatures are accompanied by relatively large antithetic ∼0.1 changes in pHcf.