Fig. 6.
Variation in heat tolerance across bleaching-susceptible and bleaching-resistant corals from experimental heat stress assay. (A) Temperature measurements (recorded every 15 min) of the controlled experimental heat stress assays (amb = ambient temperature of 27.7 °C), with an arrow indicating when dark-adapted photochemical yield (Fv/Fm) and color score were determined. (B) Respective images of coral fragments during the short-term heat stress. Three-parameter log-logistic dose–response curves were fitted to (C) Fv/Fm measurements (±95% CI) and (D) color score measurements (±95% CI) in response to temperature for M. capitata and P. compressa, where points indicate individual measures for coral genets (n = 10) in each treatment. Dashed vertical lines indicate the mean ED50 for each phenotype (dashed = susceptible, dotted = resistant), with the SE indicated by the shaded regions based on individual curve fits for each coral genet. The ED50s of photochemical yield for each coral/phenotype were 36.1 °C M. capitata (susceptible), 36.6 °C M. capitata (resistant), 37.2 °C P. compressa (susceptible), 37.3 °C P. compressa (resistant). The ED50s of the color scores for each coral/phenotype were 34.2 °C M. capitata (susceptible), 34.5 °C M. capitata (resistant), 34.6 °C P. compressa (susceptible), 34.4 °C P. compressa (resistant).