To compare the heat stress response of experimentally preconditioned corals with naturally acclimatized corals, we collected 6 colonies (WT) from outdoor flow-through tanks at the beginning of September 2018, when ambient water temperatures peaked at 29ºC in Kāneʻohe Bay. We let corals acclimate at 26ºC to reproduce our preconditioning experiment, sub-fragmented them, and then exposed fragments to acute heat stress (32ºC) using the profile and sampling described above.