Molecular analyses from previous bleaching experiments showed the correlation of HSP70 (heat shock protein 70), and PCD genes Bcl-2, BI-1, BAK, and BAX expression with bleaching, and demonstrate the involvement of caspases – apoptotic proteases - in the process (Kvitt et al., 2016; Pernice et al., 2011; Tchernov et al., 2011). Transcriptomic studies in acclimatized corals focused mostly on the longer-term changes in gene expression profiles and found differences in the expressions of e.g. heat shock family proteins, genes involved in oxidative stress, and various pleiotropic cell signaling and transcription factors such as NFkB inhibitor (NFKBI)(Bay & Palumbi, 2015; Bellantuono, Granados-Cifuentes, Miller, Hoegh-Guldberg, & Rodriguez-Lanetty, 2012; Palumbi, Barshis, Traylor-Knowles, & Bay, 2014; Thomas et al., 2018). The early phase acute heat stress response and the role of PCD in acclimatization and acquired thermal resilience in corals is not well understood but may be important as a short-term response that protects the long-term persistence of corals (Drury, 2020).