Oxygen consumption rate of the corals Goniastrea aspera, Porites lobata, and Pavona frondifera under red soil stress in the Ryukyu Islands, Okinawa, Japan

Abstract

Effects of short-term sedimentation on common coastal coral species, Goniastrea aspera, Porites lobata and Pavona frondifera, from the reef flat southeast of the Ryukyu Islands, Okinawa, Japan were investigated in laboratory experiments using oxygen uptake respirometers. The O2 consumption rate was significantly different among species and between sediment treatments (20 and 200mg l-1 red soil suspension, P<0.05). In dark experiments, Goniastrea showed higher respiration rates (0.020±0.002ml O2 cm-2h-1) than did Pavona (0.017±0.003mL O2 cm-2h-1) and Porites (0.010±0.001ml O2 cm-2h-1). In light experiments, Goniastrea also showed higher O2 consumption rates (0.021±0.003ml O2 cm-2h-1) than did Porites (0.010±0.004ml O2 cm-2h-1) and Pavona (0.007±0.001ml O2 cm-2h-1). Zooxanthellae densities were 6.53±0.13, 3.12±0.05, and 4.37±0.07 (×106cells cm-2; mean±SE, n=8) in Goniastrea, Porites, and Pavona, respectively. Coral respiration rate increased proportionally with zooxanthellae density in Goniastrea and Pavona. High zooxanthellae density may increase the O2 production that contributes to colony respiration; however, in Porites, the relationship between zooxanthellae density and coral respiration rate was not clear. The massive corals, Goniastrea and Porites, are more resistant to sediment stress than is the plate-like coral, Pavona. Goniastrea showed high tolerance and adaptation to stress conditions in all experiments, at all times (12h), with similar trends in both dark and light conditions. Porites was affected only within the first 3h under light conditions, while Pavona was the most affected species. These results help us to understand coral damage caused by red soil sedimentation, as well as coral mortality and potential shifts in community structure related to prolonged or repeated elevated levels of sedimentation on coastal reefs.