3.2 Diversity analysis of bacteria
After analyzing the high-throughput sequencing data, we got 318,431 optimized sequences without chimeras. The dilution curve of the Sobs index reached a plateau, indicating sufficient sequencing data and a wide range of detected microbial species, reflecting microbial diversity.
At the end of the first heatwaves, the Simpson index showed consistency compared to the control group. However, the Shannon index, Chao1 index, and Ace index were slightly higher than those of the control group (Fig. 3). In the second MHWs, each index showed a slight decrease compared to the control group.
Fig. 3. α-diversity analysis of coral-symbiotic bacteria under different treatments. a: Shannon. b: Simpson. c: Chao1. d: Ace.
The PCoA (Principal Coordinate Analysis) results showed that the first two axes accounted for about 69.39% of the variation in microbial community composition among all the samples. PC1 explained 52.74 % of the variation, while PC2 explained 16.65 % (Fig. 4). The three replicate samples within each group exhibited close clustering and high repeatability, and more variation was observed between groups than within groups.
Fig. 4. PCoA analysis of coral symbiotic microbial communities under different treatments.