Figure 1 Corals exposed to sublethal temperature (29°C) for 3 days become more resilient to following acute heat stress (32°C ). A) Graphical depiction of preconditioning experiment layout. C – control corals, NPC – non-preconditioned corals, PC – preconditioned corals. B) Bleaching rate of PC and NPC corals upon acute heat stress expressed as symbiont to host cell signal ratio based on confocal fluorescence microscopy. Graph shows that PC corals are more resilient to thermal stress and bleach with significantly slower pace than NPC corals. NPC corals are depicted with grey dashed line, PC with black solid line. Graph shows mean values with standard error bars. Two-way ANOVA (microscopy_signal ~ time * conditioning, p = 0.000) was used to test the influence of conditioning to the bleaching rate. * marks significantly different values in Tukey’s post hoc test ( p ≦ 0.001), n = 6. C) PC and NPC coral fragments after 5-day long heat stress exposure compared to control coral. D) Confocal fluorescence microscopy image of control (left) and bleached (right) coral. Host cells (GFP) are depicted in green, algal cells (chlorophyll) in red.
Figure 2