Mass coral bleaching events caused by elevated seawater temperatures have resulted in extensive coral mortality throughout the tropics over the past few decades. With continued global warming, bleaching events are predicted to increase in frequency and severity, causing up to 60% coral mortality globally within the next few decades. Although some corals are able to recover and to survive bleaching, the mechanisms underlying such resilience are poorly understood. Here we show that the coral host has a significant role in recovery and resilience. Bleached and recovering Montipora capitata (branching) corals met more than 100% of their daily metabolic energy requirements by markedly increasing their feeding rates and CHAR (per cent contribution of heterotrophically acquired carbon to daily animal respiration), whereas Porites compressa (branching) and Porites lobata (mounding) corals did not. These findings suggest that coral species with high-CHAR capability during bleaching and recovery, irrespective of morphology, will be more resilient to bleaching events over the long term, could become the dominant coral species on reefs, and may help to safeguard affected reefs from potential local and global extinction.

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.Coral bleaching is primarily caused by elevated seawater temperatures, ultraviolet radiation, or both, resulting in decreased endosymbiotic zooxanthellae or photosynthetic pigments and a pale to white coral colony (e.g., Brown 1997). Bleaching severity and mortality varies among individuals, species, depths, and locations (e.g., Loya et al. 2001). Research on the underlying mechanisms driving variability has focused on zooxanthellar temperature constraints (e.g., Smith et al. 2005) and genetic variation (e.g., Baker 2001) to explain bleaching susceptibility. The few studies that investigated the role of the coral host either examined a single time period (Porter et al. 1989;Grottoli et al. 2004Grottoli et al. , 2006 or were unable to control for seasonal effects over long-term observations of recovery (Fitt et al. 1993(Fitt et al. , 2000. No studies have both distinguished seasonal from bleaching effects on the host and followed these effects over long-term recovery.In healthy corals, photosynthetically fixed carbon is translocated from zooxanthellae to host, providing up to 100% of daily metabolic requirements (Muscatine et al. (Stimson 1987;Porter et al. 1989;Grottoli et al. 2004) and represents a significant energy reserve in corals (Edmunds and Davies 1986;Harland et al. 1993). 1981; Grottoli et al. 2006). Excess is stored in the host as lipids at concentrations of 10-40% of total biomassIn bleached corals, decreased zooxanthellae densities or chlorophyll a (Chl a) levels result in decreased net photosynthesis (Porter et al. 1989;Lesser 1997;Grottoli et al. 2006). Photosynthetically fixed carbon translocated to the host decreases, leaving bleached corals to rely on stor...

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