Flexible Symbiotic Associations of With Five Typical Coral Species in Tropical and Subtropical Reef Regions of the Northern South China Sea.

The coral symbiont plays important roles in the adaptation of coral to environmental changes. However, coral- symbiotic associations are not well-understood in the South China Sea (SCS) whilst considering environmental factors and host taxa. In this study, next-generation sequencing of the internal transcribed spacer region 2 (ITS2) marker gene was used to explore the symbiotic associations between and five typical coral species across tropical and subtropical reef regions of the SCS. The results showed that sp., , , and exhibited distinct compositions between tropical and subtropical reef regions, whereas had stable compositions. More heterogeneous compositions among different coral species were observed in the tropical region, but there were no statistically significant differences in compositions among different coral species in subtropical reef regions. There was a correlation between the compositions and environmental factors, except for the composition of . subclades D1, D2, C71, C71a, C21, C3b, and C161 were primarily explained by the seawater temperature, nitrate, ammonia, and phosphate. Several host-specific subclades (e.g., C15, C15.6, and C91) were observed in as well. The findings of this study demonstrate the relationship of diversity with coral hosts and the environment are helpful for elucidating the adaptation of corals to global climate change and anthropogenic disturbance.