Fig. 1

Anatomical differences in coral microbiomes. Coral mucus, tissue, and skeleton microbiomes differ in richness, composition, and response to host vs. environmental factors based on 16S rRNA gene sequence data. a Microbial community richness (observed OTUs) in coral mucus (teal), tissue (orange) and skeleton (purple), assessed at an even depth of 1000 reads per sample. P-values reflect Tukey’s HSD. b Principal coordinates plot of coral-associated microbial communities (Unweighted UniFrac; n = 614). Reads were rarefied to 1000 reads per sample. Coral compartments show significant differences in community composition (Adonis R² = 0.028; permutational p < 0.001). The percent variation explained by the principal coordinates is indicated at the axes. Boxplots of the second PC elucidate differences among compartments. P-values reflect Tukey’s HSD. c Relative influence of host and environmental factors on microbiome composition (Weighted UniFrac, Adonis adjusted R²) in each compartment. Darker cells for a compartment indicate that it is more strongly influenced by that trait than the other compartments (Adonis adjusted R² values z-score normalized within columns). Cell values reflect adjusted R², which penalizes R² for each factor downward to allow for fair comparison among factors with varying degrees of freedom. Asterisks indicate a significant effect of that factor (Adonis permutational p < 0.05) on the microbiome in that compartment, following stringent Bonferroni correction across all traits and compartments. While both host and environmental factors influenced all compartments, host factors tended to influence coral tissue and skeleton more strongly than mucus, whereas host environment more influenced mucus microbiomes. All values in the table, plus other combinations of rarefaction depth and multivariate dissimilarity measure are presented in Supplementary Data 4