Developmental carryover effects of ocean warming and acidification in corals from a potential climate refugium, the Gulf of Aqaba.

Coral reefs are degrading from the effects of anthropogenic activities, including climate change. Under these stressors, their ability to survive depends upon existing phenotypic plasticity, but also transgenerational adaptation. Parental effects are ubiquitous in nature, yet empirical studies of these effects in corals are scarce, particularly in the context of climate change. This study exposed mature colonies of the common reef-building coral from the Gulf of Aqaba to seawater conditions likely to occur just beyond the end of this century during the peak planulae brooding season (Representative Concentration Pathway 8.5: pH -0.4 and +5°C beyond present day). Parent and planulae physiology were assessed at multiple time points during the experimental incubation. After 5 weeks of incubation, the physiology of the parent colonies exhibited limited treatment-induced changes. All significant time-dependent changes in physiology occurred in both ambient and treatment conditions. Planulae were also resistant to future ocean conditions, with protein content, symbiont density, photochemistry, survival and settlement success not significantly different compared with under ambient conditions. High variability in offspring physiology was independent of parental or offspring treatments and indicate the use of a bet-hedging strategy in this population. This study thus demonstrates weak climate-change-associated carryover effects. Furthermore, planulae display temperature and pH resistance similar to those of adult colonies and therefore do not represent a larger future population size bottleneck. The findings add support to the emerging hypothesis that the Gulf of Aqaba may serve as a coral climate change refugium aided by these corals' inherent broad physiological resistance.