The effects of hydrogen peroxide on metabolism in the coral Goniastrea aspera

Coral metabolism reflects the physiological condition of a coral colony. We studied coral metabolism using a continuous-flow, complete mixing (CFCM) experimental system. Small-size Goniastrea aspera coral colonies were incubated in the CFCM system with and without hydrogen peroxide (H2O2) added to the supplied seawater (0 µM H2O2 for 12 days; 0, 0.3, 3.0, and 30 µM H2O2 for 3 days, for each treatment) Without addition of H2O2, coral metabolism, including photosynthesis (gross primary productivity) and calcification, was relatively stable and there were no significant metabolic changes, suggesting that, without H2O2 added to the CFCM system, the corals did not suffer significant stress from the experimental system over a 12-day incubation period. When H2O2 was added, large decreases in photosynthesis and calcification were observed. The non-parametric Mann–Whitney U-test showed that there were statistically significant differences in photosynthesis after addition of 3.0 µM and 30 µM H2O2, compared with the control. We also found statistically significant differences in net calcification after addition of 30 µM H2O2. Thus, the incubation experiments suggest that higher H2O2 concentrations in seawater clearly influence coral metabolism. However, the results also suggest that the current seawater H2O2 level in Okinawa is not likely to pose significant acute effects on the metabolic activities of corals.