Differences in Symbiodiniaceae communities and photosynthesis following thermal bleaching of massive corals in the northern part of the South China Sea.

Although many achievements have been made in studies on the relationship between Symbiodiniaceae and coral bleaching, there is little information on the responses of Symbiodiniaceae to coral thermal bleaching in the South China Sea (SCS). In this study, Symbiodiniaceae communities and the effective quantum yield (Ф PSII) of healthy and bleached massive corals from the SCS were compared. The results indicated that the Symbiodiniaceae communities and Ф PSII values showed coral bleaching-dependent variations. Specifically, the relative abundances of the rare putatively thermally tolerant Durusdinium sp. (D1) and the Symbiochlorum hainanensis increased significantly in the bleached corals. In addition, bleached Porites lutea was mainly associated with the putatively thermally tolerant Cladocopium sp. (C15 and C91) and exhibited the highest Ф PSII value compared with other bleached corals. These results highlight that the rare putatively thermally tolerant algae and coral species-specific algae may be important for understanding thermal bleaching of corals. • A snapshot of Symbiodiniaceae communities and photosynthesis following thermal bleaching of massive corals in the SCS. • Symbiodiniaceae communities and Ф PSII values showed coral bleaching-dependent variations. • The abundance of Durusdinium sp. (D1) and Symbiochlorum hainanensis were significantly increased in bleached corals. • Porites lutea showed smallest decrease in Ф PSII and hosted coral specific Cladocopium sp. (C15 and C91). [ABSTRACT FROM AUTHOR]