Diversity of free-living and symbiotic Symbiodinium in the coral reefs of Sanya, South China Sea

摘要

Unicellular photosynthetic dinoflagellates from the genus Symbiodinium are found either free-living or in hospite with a wide variety of marine invertebrate hosts including scleractinian corals. The linkages between free-living and endosymbiotic Symbiodinium remain largely unstudied and constitute a major gap in knowledge. In this study, the diversity of free-living Symbiodinium spp. and those associated with scleractinian corals from coral reefs in Sanya CRNR, South China Sea were determined by Symbiodinium-specific primers for the hypervariable region of the chloroplast 23S domain V (cp23S-HVR). The results illustrated that the free-living Symbiodinium spp. were highly spatially heterogeneous with high diversity related to clades A, B, C, D, F, G and H. However, the reef corals mainly hosted only one symbiont type of either clades C or D, and few species could harbour both concurrently. Surprisingly, Symbiodinium spp. in scleractinian corals were totally different from free-living forms in adjacent waters. These results suggest that the corals did not recruit Symbiodinium spp. from adjacent waters and the exchange of Symbiodinium spp. between corals and waters is limited in this region.