Energy Reserves and Metabolism as Indicators of Coral Recovery from Bleaching

With reduced zooxanthellae, chlorophyll a (Chl a), or both, concentrations, bleached corals rely on some combination of energy reserves (i.e., lipid, carbohydrate, protein) and heterotrophy to survive and recover. To understand the dynamics of energy reserves and metabolism during long-term recovery, Porites compressa and Montipora capitata corals were experimentally bleached in outdoor tanks for 1 month (treatment corals). Additional corals were maintained in separate tanks at ambient temperatures (control corals). Recovery occurred on the reef for 0, 1.5, 4, or 8 months. At 0 months all treatment corals were white in color, with lower Chl a, lipid, carbohydrate, protein, tissue biomass, and photosynthesis than control corals. During recovery, P. compressa replenished energy reserves and tissue biomass at 8 mo, long after photosynthesis and Chl a had recovered at 1.5 and 4 months, respectively. M. capitata replenished energy reserves at 1.5 months, despite decreased Chl a and photosynthesis levels. P. compressa depends on photosynthetically fixed carbon for recovery from bleaching, whereas M. capitata does not. Overall, M. capitata had a faster recovery rate than P. compressa for all measured variables except Chl a concentration. With intensifying bleaching, coral diversity on future reefs may favor species with faster recovery rates.