Species-specific molecular responses of subtropical corals to natural bleaching events: Insights from coral microbiome, metagenome, and metatranscriptome analyses

Climate change-induced marine heatwaves pose significant threats to corals through increased frequency and severity of bleaching events. To effectively conserve coral reef ecosystems, it is crucial to understand the variations in thermal susceptibility among coral species. Our previous studies highlighted the diverse responses of bacterial and zooxanthellae communities, as well as holobiont transcriptomic changes, in three coral species — Montipora peltiformis, Pavona decussata, and Platygyra carnosa—during the natural bleaching event of 2017. However, variations in sampling sites and times limited our capacity to conduct a comprehensive comparison of the molecular mechanisms contributing to species-specific bleaching resilience. To address these knowledge gaps, we investigated the microbiome and metagenomics of five scleractinian corals — Acropora solitaryensis, Duncanopsammia peltata, M. peltiformis, P. decussata, and P. carnosa—using samples collected during the 2022 bleaching event at Bluff Island, Hong Kong. By assessing coral physiological parameters and characterizing bacterial and zooxanthellae communities, this study aims to elucidate the roles of microbiome communities in coral survival and recovery from bleaching. Additionally, we conducted functional analyses of metagenomes and metatranscriptomes to identify the adaptive molecular responses of both coral hosts and symbionts during recovery with different bleaching susceptibility. Our findings provide insights into the molecular mechanisms underlying holobiont resilience, which may determine the fate of subtropical coral species in response to global and regional environmental changes.