Abstract
Coral reefs around the world are experiencing extensive bleaching and death caused by climate-driven increases in ocean temperature. In order to stem this decline, reef restoration practitioners have focused efforts toward identifying bleaching resistant and/or resilient individuals that can be utilized for restoration as a method of building more resilient reefs. However, the effectiveness of this intervention strategy will depend heavily on our ability to predict where thermally tolerant corals can be sourced based on certain environmental criteria. Exploring this interaction between environment and thermal tolerance will be essential in understanding the mechanisms underlying corals’ responses to thermal stress and how these processes can be applied to coral restoration techniques. In order to investigate the mechanisms underpinning both bleaching resistance and resilience in corals and to what degree these traits are affected by their environment, we collected genotypes of the threatened Caribbean staghorn coral, Acropora cervicornis (n = 38) originally sourced from different environmental regions that had been common-gardened in a nursery grow-out site for one year. Replicate fragments underwent a thermal stress assay to determine if there is a relationship between bleaching resistance/resilience and region of origin. We regularly recorded the photochemical efficiency of symbionts (Fv/Fm) as a proxy of coral health as well as bleaching scores standardized to the Coral Watch health chart. We sampled half of the fragments at the end of the heat stress period and the other half at the end of the recovery period to compare the biological responses shared among corals that are bleaching resistant and/or resilient. We found that corals sourced from warmer, more southern regions had higher resistance and resilience compared to corals from colder, more northern regions. We conclude that corals from these warmer source locations (i.e. Miami-Dade and Monroe counties) could be translocated to cooler environments (i.e. Broward county) while maintaining their thermal tolerance, potentially increasing both resistance and resilience of the entire reef ecosystem. These results support the inference that fixed effects may contribute more to thermal tolerance than acclimatization and provide important implications for reef restoration efforts.