The presence and localization of organic matrix associated with the aragonite phase in the fibers of blue coral Heliopora coerulea skeletons were studied by in situ microRaman mapping spectra, with a spatial resolution of ~0.3 μm. Spatial variations in the amounts and chemical compositions of the fibers were imaged. The results showed that the amide I and the α-helix of amide III were perpendicular to the c-axis of fibers' growth, whereas the β-turns/sheet of amide III was in the parallel conformation. Visible S-S and C-S bonds were consistent with the XANES results, which indicated the existence of organic sulfur in coral skeletons. Regular cyclic changes between aragonite and organic matrix refined a stepping growth mode of the fibers' biomineralization. An inorganic PO(4) bond was detected and exhibited the same concentration variation trends as the v(4) aragonite bands. Instead of providing an ocean P proxy on the subseasonal to centennial scale by LA-ICPMS, the possibility was raised of producing high resolution surface ocean phosphorus records on daily environmental variation via P/Ca variation cycles determined from Raman mapping data.
© 2011 American Chemical Society