Fig. 2

Holobiont physiological health metrics under increasing heat stress. Net photosynthesis, photosynthesis/respiration ratio (P/R ratio; P/R < 1 indicates a net heterotrophic state), photochemical effective efficiency (∆F/Fm′) and health score (health score ≥ 6 indicates normally pigmented corals) are shown over time (T0–T5) under increasing temperatures; DHW are reported for the heat treatment only (DHW = 0 under ambient conditions). Net photosynthesis and P/R ratio were measured at an additional time point (Tp) corresponding to 5 DHW. Mean ± SE is shown over time, with asterisks indicating significantly different physiological responses between ambient and heat treatment at each time point (p < 0.05, adjusted post hoc tests)