In contravention of our second hypothesis, pCO2 did not exacerbate (or conversely, diminish) the effects of thermally-induced Symbiodinium loss. This contrasts with a previous study that found that ocean-acidification exacerbated thermally-induced visual paling in corals (Anthony et al., 2008), although this study did not perform Symbiodinium counts and therefore could not determine if the paling was primarily due to symbiont loss or to loss of host pigments, which can also be thermally induced (ref : Dove et al. 2008 or Takahashi et al).