Dynamics of Dipsastraea pallida-symbiont association following bleaching events across the northern Persian Gulf and Gulf of Oman

Abstract

Reef-building corals are in obligate symbiosis with dinoflagellates of the family Symbiodiniaceae. The partnership, however, is prone to breakdown as a result of thermal stress, which leads to coral bleaching. According to the Adaptive Bleaching Hypothesis, corals’ recovery from bleaching is profoundly influenced by forming stable associations with thermotolerant algal strains during bleaching. Consequently, the knowledge of the diversity of host-symbiont associations during this period is substantial. Since the extent of symbiont shuffling varies among different host taxa, we investigated the diversity of dominant Symbiodiniaceae in association with the scleractinian coral Dipsastraea pallida before and after massive bleaching events of 2017 in the Persian Gulf and 2018 in the Gulf of Oman. We observed a flexible association between D. pallida and five lineages of Symbiodiniaceae (i.e., ITS2-types A1.4, C3, C39, D1a, D5) with a clear regional pattern. However, the pattern of these associations was changed following bleaching events, with the complete replacement of Cladocopium-C39 by Durusdinium-D1a in the Gulf of Oman, and increased proportion of Durusdinium-D1a and disappearance of Symbiodinium-A1.4 in the northeastern Persian Gulf. In the westernmost Persian Gulf, on the other hand, a stable D. pallida-Cladocopium-C3 partnership was observed. These findings convey the potential of D. pallida to shift the prevalence of its symbiont communities within a population in response to bleaching, which may reflect symbiont shuffling and/or differential mortality and partly explain the predominance of Dipsastraea corals in the Persian Gulf and Gulf of Oman.