Sea surface temperatures (SST) and chlorophyll a concentrations (Chl a) in the southern Red Sea have wide variations based on distance from the coast. To understand how these variations can affect the diversity of symbionts hosted by reef-associated organisms, we conducted a study in the central and southern Red Sea to examine the diversity of Symbiodiniaceae hosted by the zooxanthellate zoantharian Palythoa tuberculosa at different distances from the coast: offshore (FBO), midshelf (FBM) and inshore (FBI) of Farasan Banks, and inshore at Thuwal (TI). Genomic DNA was extracted from 198 specimens, followed by amplification of the ribosomal DNA internal transcribed spacer 2 (ITS-2) and noncoding region of the chloroplast plastid minicircle (psbAncr). Durusdinium and six lineages of Cladocopium (Pt-1-a, Pt-1-b, Pt-1-c, Pt-1-d, Pt-3-a, Pt-3-b) were identified based on sequences of the two marker regions. Changes in composition of Symbiodiniaceae lineages were observed from FBI (high SST, high Chl a) to FBO (low SST, low Chl a). Molecular variance analyses showed that distance from coast was the most likely predictor of differences in Cladocopium lineages. Multinomial logistic regression analysis showed a transition among different Cladocopium lineages as SST increased. One Cladocopium lineage, Pt-1-b, demonstrated higher prevalences at high SSTs and increased in prevalences at the same rate as thermotolerant Durusdinium. Additionally, Cladocopium lineage Pt-3-a had a high affinity to low Chl a concentrations. This study demonstrates that environmental variations in SSTs and Chl a concentrations are significant predictors for the diversity of dominant Symbiodiniaceae within individual host P. tuberculosa colonies. We theorize that flexibility with different lineages of Symbiodiniaceae allows generalist P. tuberculosa to live across a wide range of environments in the southern Red Sea.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): URF/1/1389-01-01
Acknowledgements: This work was partially funded by the King Abdullah University of Science and Technology (KAUST) (award URF/1/1389-01-01, Red Sea Research Center funds, and baseline research funds to MLB and TR), JSPS Kakenhi-Kiban B grant entitled “Global evolution of Brachycnemina and their Symbiodinium” to JDR, and Sasagawa Research Foundation funding to HBW (29-751). We wish to thank the captain and crew of the MV Dream Master, the KAUST Coastal and Marine Resources Core Laboratory, A. Gusti (KAUST), Roberto Arrigoni, Darren Coker, Tane Sinclair-Taylor and other members of the KAUST Reef Ecology Lab for fieldwork assistance in the Red Sea. Comments from two reviewers greatly improved an earlier version of this manuscript.