Fig. 1.

Experimental design. Colonies/genotypes (n = 5 genets/treatment) of S. pistillata holobionts (i.e., Stylophora pistillata, Symbiodinium microadriaticum A1, bacterial microbiome) were exposed to two different thermal stress experiments. Note that, for reasons of visual clarity, the x-axes are not linear. (A) A short-term thermal stress experiment was carried out with the CBASS. These thermal treatments included constant temperature at 27 °C (baseline), ramping up to 29.5 °C, 32 °C, or 34.5 °C in 3 h, a 3 h hold at target temperatures (“response” sampling point T1), ramping down to 27 °C over 1 h, and a “recovery” sampling point (T2) 11 h later. (B) The long-term thermal stress experiment using the RSS included constant temperature at 27 °C (baseline), ramping up to 29.5 °C, 32 °C, or 34.5 °C over 4 d, a 7 d temperature hold (“response” sampling point T1; except for the 34.5 °C treatment in which sampling was done after 2 d due to high levels of bleaching), ramping down to 27 °C in 1 d, and a recovery sampling point (T2) 2 d later. Note that the long-term heat stress experiments correspond to 2.8 (29.5 °C), 6.3 (32 °C), and 4.7 (34.5 °C) degree heating weeks (DHW) (77). Ramets of the same five genotypes were sampled for each treatment at each time point. The color coding used throughout the paper is: blue: 27 °C (control), yellow: 29.5 °C, orange: 32 °C, and red: 34.5 °C.