Stress response in naturally acclimatized corals correspond to experimentally preconditioned corals
In vitro experiments may not always reflect the natural behavior of the organism. To analyze the stress response of naturally acclimatized corals, we collected six Pocillopora acuta colonies living in the outdoor flow-through tanks (WT) at the beginning of September 2019, when water temperatures peaked 29ºC in Kaneohe bay (Fig. S2). We let them acclimate to winter ambient 26ºC to simulate our preconditioning experiment and then exposed them to acute heat stress (32ºC). The correlation of gene expression between WT and PC corals during acute heat stress was surprisingly high (Fig 3, S2) showing that corals react to peaking temperatures in a similar way as to natural temperature profile. It also suggests that during summer, when the risk of extreme weather causing warming events and mass coral bleaching is the highest, corals naturally acclimatize to warm temperatures through modulations in the PCD pathways, which increase their survival chances by slowing down the bleaching rate.