Figure 2. Indicators of physio-chemical conditions at the site of calcification in corals in the four pH treatments.

(a) Aragonite crystal morphology imaged by scanning electron microscopy. Scale bar, 5 μm. pH treatment indicated above each image. (b) Calcifying fluid pH in corals under light and dark conditions at seawater pH 7.2 and pH 8.0. Data are means±s.e.m. CF=calcifying fluid; SW=seawater surrounding the colonies.