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

Abstract:

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 CO₂ 
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.