Figure 4.

Secondary electron images of S. siderea corallites (left column) and septae (right column) produced under pCO₂-temperature treatments of 426 ppm-v/28.1 °C (A,B), 424 ppm-v/31.9 °C (C,D), 888 ppm-v/28.0 °C (E,F), and 940 ppm-v/31.8 °C (G,H). Corallites are less infilled owing to thinner septae under conditions of elevated pCO₂. Secondary electron images of the coral septae (right column) also reveal that elevated pCO₂ decreases septal rugosity, apparently by reducing the prominence of the corals’ aragonite nucleation sites, their so-called centers-of-calcification.