Knowledge of the mechanisms by which corals build their aragonitic (calcium carbonate) skeletons is essential for understanding their sensitivity to environmental change, including ocean acidification. Key to the coral calcification process is controlling the carbonate chemistry within an extracellular calcifying fluid where the skeleton is formed. However, studying this fluid has proved challenging due to its small size and isolation underneath the polyp. To date, calcifying fluid chemistry has been quantified via isotopic proxies in the skeleton at seasonal resolution, or in vivo with invasive microsensors. In this talk, I will present a new approach to measure calcifying fluid carbonate chemistry with Raman spectroscopy analyses of the skeleton. This technique provides the first quantification of the aragonite saturation state of the coral calcifying fluid. Further, Raman spectroscopy can be applied at micron-scale resolution in the skeleton, to track sub-daily variability, and even in vivo on the timescale of seconds. I will present the insights that we have already learned from Raman spectroscopy regarding coral calcification and its sensitivity to ocean acidification. In addition, I will discuss potential future applications of Raman spectroscopy to not only corals, but other marine biominerals including calcareous algae, foraminifera, and fish otoliths.
Tom is currently a Postdoctoral Research Associate at the University of Western Australia node of the ARC Centre of Excellence for Coral Reef Studies. He completed his PhD in 2016 at Woods Hole Oceanographic Institution and Massachusetts Institute of Technology. Tom’s research has focused on the sensitivity of corals to ocean acidification and warming, across spatial scales from reef communities to the micro-scale calcifying fluid within coral polyps. Since coming to UWA, Tom has developed a Raman spectroscopy technique for quantifying the aragonite saturation state at which coral skeletons are formed. This novel technique is providing new insights into coral calcification and is paving the way for innovative research approaches aimed at characterizing coral sensitivities to ocean acidification on short (daily) timescale.