The diversity of symbiodiniaceae hosted by Palythoa tuberculosa found at the edge of the South China Sea

Abstract

The Symbiodiniaceae genera composition hosted by the zooxanthellate zoantharian Palythoa tuberculosa is well documented in some parts of the Indo-Pacific region. Nevertheless, there are limited studies when it comes to the South China Sea (SCS), and no reports from the northern half of this region are available. This study examined Symbiodiniaceae diversity hosted by P. tuberculosa around Dongsha Atoll, in the north of the SCS. Samples of P. tuberculosa were collected inside and outside of the atoll. Phylogenetic analyses were conducted using sequences of the conservative internal transcribed spacer region 2 of rDNA (ITS2) and the hypervariable non-coding region of the chloroplast psbA gene (psbAncr). Cladocopium was the dominant Symbiodiniaceae genus found in Dongsha, with only one Durusdinium-hosting P. tuberculosa colony found within the atoll. psbAncr results showed three Cladocopium lineages previously recorded in Okinawa (lineages 1, 2 and 3 sensu Noda et al., 2017). An experiment was set up outside the atoll to compare temperature fluctuations caused by internal waves, and the host-symbiont relationships found on spurs (n = 27, depth = 5.95 ± 0.23 m) and within grooves (n = 27, depth = 8.11 ± 0.47 m). Our results showed that there were no significant differences of Cladocopium lineages among the P. tuberculosa found at spurs and grooves despite significant differences in water temperature (p < 0.001). Our results show that P. tuberculosa is flexible with Cladocopium lineages hosted, and that the internal wave regime at Dongsha Atoll apparently did not affect the host-symbiont relationship, at least in the spurs and grooves.