Unique quantitative Symbiodiniaceae signature of coral colonies revealed through spatio-temporal survey in Moorea

One of the mechanisms of rapid adaptation or acclimatizationto environmental changes in coralsis through the dynamics of the composition of their associated endosymbiotic Symbiodiniaceae community. The various species of these dinoflagellatesare characterized by different biological properties, some of which can confer stress tolerance to the coralhost. Compelling evidence indicates that the corals’ Symbiodiniaceae community can change via shufflingand/or switching but the ecological relevance and the governance of these processes remain elusive. Using a qPCR approach to follow the dynamics of Symbiodiniaceae genera in tagged colonies of three coralspecies over a 10–18 month period, we detected putative genus-level switching of algal symbionts, with coralspecies-specific rates of occurrence. However, the dynamics of the corals’ Symbiodiniaceae community composition was not driven by environmental parameters. On the contrary, putative shufflingevent were observed in two coralspecies during anomalous seawater temperatures and nutrient concentrations. Most notably, our results reveal that a suit of permanent Symbiodiniaceae genera is maintained in each colony in a specific range of quantities, giving a unique ‘Symbiodiniaceae signature’ to the host. This individual signature, together with sporadic symbiont switching may account for the intra-specific differences in resistance and resilience observed during environmental anomalies.