Polyp bail-out induction
To induce the polyp bail-out response in Pocillopora acuta , a hyperosmotic environment was established by gradual addition of high-salinity seawater (48‰). In experiment I, seawater salinity increased from 35‰ to ~43‰ after 12 h and to ~46‰ after 24 h in the treatment group. Morphologically, no obvious signs of a stress response were seen at 12 h in the treatment group. Polyp bail-out was observed at 24 h, at which 30 – 50% of the polyps were found detached from the skeleton (Fig. 2). For the control group (salinity change < 0.5‰), no sign of polyp bail-out or other stress response was observed at any time during the experiment (Fig. 2).