Isotopic and Elemental Ratios from Porites Corals Collected Along a Natural pH Gradient

Friday, 19 December 2014: 8:45 AM
Stewart Fallon, The Australian National University, Acton, Australia and Katharina Fabricius, Australian Institute of Marine Science, Townsville, Australia
Porites coral cores have been collected along a pH gradient from unique volcanic CO2 seeps in Milne Bay Province, Papua New
Guinea. The CO2 gas bubbles emerging from the reefs provide local ocean acidification conditions similar to those predicted for the middle to the end of this century, and beyond. We have measured δ18O, δ13C, Δ14C, Sr/Ca, Mg/Ca, Li/Mg, Ba/Ca from four coral cores collected along the pH gradient. One coral core was collected from what we consider a control site. Volcanic CO2 bubbling through the seawater
in Milne Bay is free of radiocarbon, resulting a unique signal that is preserved in the coral skeleton. We have measured the radiocarbon content of the coral skeleton back through time from sites heavily impacted by CO
and ”control” sites not impacted by CO2 seeps. Three impacted sites show an increase of CO2 into the DIC by
4%, 10% and 14%. Variations outside of temperature/freshwater appear to be influencing the other isotopic and elemental ratios.