Figure 1: Superoxide produced by bleached and pigmented colonies of field-based corals.

(a) Representative FeLume trace showing superoxide concentrations millimetres above the surface of a Porites lobata colony that had both bleached and pigmented sections. Superoxide data were collected over time by positioning the sample tubing at a static location over the bleached section of the coral for several minutes, and then moving the tubing to a single location over the pigmented section for a similar amount of time. Chemiluminescence signals were converted to superoxide concentrations by first subtracting out signals of an aged filtered seawater baseline (not shown), and then corrected signals were converted to concentrations using the daily calibration curve. The specific coral-derived signal (dashed arrow) was then determined by subtracting the signal obtained at the coral surface from the seawater signal obtained 5–15 cm away from the coral. The average superoxide concentrations between bleached and pigmented sections are not significantly different, as revealed by a two-sample t-test (P>0.05). Once the tubing was removed from the coral surface, superoxide concentrations rapidly declined back to background seawater (SW) levels (solid arrow). Finally, the addition of SOD, which selectively degrades superoxide, confirmed that chemiluminescence signals were attributable to superoxide. Superoxide concentrations are reported as average±s.d. of the temporal signal. (b) Superoxide levels measured for bleached and pigmented colonies of each coral species corrected for background SW concentrations. Circles indicate peak superoxide levels measured for each specimen. For M. capitata, superoxide concentrations at the surface of the colony were lower than the background SW, resulting in a negative SW-normalized superoxide concentration. Average species-specific superoxide levels not connected by the same letter (indicated on the x-axis below the bars) are significantly different (P<0.05). Error bars indicate s.d., n=2 (F. scutaria bleached), n=2 (F. scutaria pigmented), n=10 (M. capitata bleached), n=8 (M. capitata pigmented), n=13 (P. compressa bleached), n=9 (P. compressa pigmented), n=9 (P. damicornis bleached), n=9 (P. damicornis pigmented), n=13 (P. lobata bleached) and n=16 (P. lobata pigmented).