Award: OCE-2103067

Coral bleaching is increasing on reefs worldwide due to rising sea surface temperatures associated with climate change, which disrupts the symbiosis between the coral and their energy-generating algal symbionts. This dramatic heat stress response turns the normally colorful corals bright white, and yet during these heat stress events not all corals undergo bleaching. The physiological costs of symbiont loss are substantial, and even though both bleached and unbleached phenotypes immediately adjacent to each other are experiencing heat stress during a heatwave, bleached corals can have reduced survival relative to non-bleached colonies of the same species. This project collected samples of the Hawaiian rice coral, Montipora capitata, throughout the 2020 heating event and thereafter in 2021. This now extends the biobank of coral tissue biopsies and physiological analyses we initiated in 2015 through repeated thermal stress events and intervening recovery periods. Our results indicate that corals that previously bleached continued to be more pale throughout the timeseries. We assessed the response of previously bleached and unbleached colonies from tissue samples collected in July 2019 prior to the heatwave and in Dec 2019 following the heatwave. We characterized the coral holobiont, which includes that endosymbiont community, microbial community, gene expression, and DNA methylation (an epigenetic assessment of gene expression regulation). Our comparison of samples prior to and post-bleaching show a legacy of the bleaching phenotype through shifts in symbiont communities, impacted host gene expression, and variable host DNA methylation. Together, this indicates that environmental history and the phenotypes generated in prior heatwave events will have implications for the response capacity of corals as heatwaves continues to increase in frequency in the future. The multi-omic approaches used in this project are not only applicable to corals and invertebrates, but to the wider epigenetics, gene expression, and microbial fields. The code and data shared freely from this project can be used and adapted by other fields as well. Further this work supported a PhD student?s training, dissertation, and generation of freely available data and analytical code. Last Modified: 07/07/2022 Submitted by: Hollie M Putnam