Figure 2.

Acropora sp.: (a, b) polarized light microscopy (PLM) images and (c) a component map with a black mask where the Ca signal is undetectable and pixels colored according to the mineral phase spectroscopically observed. In this and all other component maps in this work, red pixels are ACC-H₂O, green pixels are ACC, and blue pixels are aragonite. The component spectra used to obtain all component maps are shown in Figure S1. (d) Average PEEM image overlaid with the component map, with both black mask and pure blue aragonite removed. (e, f) One region of interest, boxed in panels c and d, magnified here to show the precise locations of both intra- and extraskeletal amorphous pixels. Extraskeletal particles are no farther than 2 μm outside the skeleton’s surface (yellow line in panels d and f), are mostly amorphous, and are assumed to be inside the calicoblastic epithelium. Intraskeletal amorphous pixels in panel d extend several micrometers inside the yellow line. See Figure S2 for more images of this area.