Yeah, "coral recruits" are the larvae of parent colonies. They noted that the finding did not extend to the parent, which reacted negatively.Sorry. I guess we both skimmed over it and missed some parts.
"To date, only one study has manipulated pH over a diurnal cycle mimicking ecologically relevant pH shifts (daytime pH = 8.00, night-time pH = 7.77) to examine short-term (3–6 day) effects on coral recruits [20]. Although this study [20] did not report the pH variability occurring naturally in the organism's habitat, they found that in some instances coral recruits responded positively to both daily fluctuations in pH and to OA"