NMR Relaxometry of Scleractinian Coral Skeletons and Environmental Changes

In the framework of the European Project CoralWarm [1,2], the pore-volume structure of the skeletons of scleractinian corals from Mediterranean Sea have been analyzed with the aim to determine parameters from NMR Relaxometry useful to relate porosity and pore-size distribution to environmental conditions. The final goal is to relate structure variations to climate change. Mercury intrusion porosimetry shows wide ranges of pore radius, but the high Hg pressure could cause particle compression and rupture. The definition of a method to determine porosity and pore-size distribution in a non-invasive, non-destructive way can be of great interest. In a recent paper [3] we have demonstrated that NMR Relaxometry of clean coral skeletons, saturated with water, is an efficient tool for pore-volume structure characterization. The data obtained from CPMG sequence were inverted by UpenWin software [4] to get T2 distributions. Parametric and non-parametric statistical test have been performed on two parameters extracted from T2 distributions: the cut-off time (relaxation time in between two peaks, or the tail and the peak) and the micro-porosity (fraction of signal with relaxation times below the cut-off). Also, a multivariate analysis has been performed to check the sensitivity of microporosity to variations of mass and growing temperature. The results demonstrate that the NMR parameters so determined are good tools to check the sensitivity of the corals to the environmental changes. Acknowledgements: the research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013) / ERC grant agreement n° 249930 –CoralWarm: Corals and global warming: the Mediterranean versus the Red Sea; the authors wish to thank the CoralWarm team members for corals sampling and cleaning. [1] ERC, IDEAS Project CoralWarm - Corals and global warming: the Mediterranean versus the Red Sea, http://www. coralwarm.eu.; [2] E. Caroselli et al., Zoology, 114, 255-264 (2011); [3] P. Fantazzini et al., Environmental Science & Technology, in press, DOI:10.1021/es402521b; [4] UpenWin, a software to invert multi-exponential data, commercialized by the University of Bologna, www.unibo.it/Portale/Servizi+ImpreseUpenWin.htm.