Long-term recovery of Caribbean corals from bleaching

Mass coral bleaching events are increasing in frequency and intensity and are predicted to occur annually in the coming decades. However, it remains poorly understood how quickly Caribbean corals can recover from bleaching. To explore the responses to heat stress and subsequent recovery in Caribbean corals, three species (Porites divaricata, Porites astreoides, and Orbicella faveolata) were experimentally bleached in outdoor flow-through tanks for 15 days then allowed to recover on the reef for 1.5 and 11 months. At each interval on the reef, endosymbiont concentrations, energy reserves (i.e., total soluble lipid, soluble animal carbohydrate, soluble animal protein), calcification, and stable carbon and nitrogen isotope values of the animal host (δ13Ch, δ15Nh) and endosymbiotic algal fractions (δ13Ce, δ15Ne) were measured in treatment and control fragments of each species. Despite variations in bleaching recovery strategies among the coral species, all corals recovered within one year. Specifically, bleached P. divaricata catabolized lipids and decreased calcification in response to lower endosymbiont concentrations. In contrast, both P. astreoides and O. faveolata maintained energy reserves despite lower endosymbiont concentrations, yet both decreased calcification rates after bleaching. Overall, these findings indicate that these corals are capable of surviving and recovering from a mild bleaching event within one year. Though these finding indicate that P. astreoides and O. faveolata may be resilient through single isolated bleaching events under annual bleaching, many Caribbean coral reefs may still experience a decline over the coming decades.