Changes in coral bacterial communities during a natural bleaching event linked to El Niño in the South China Sea

Abstract

An understanding of the effects of bleaching on coral bacterial communities is necessary to fully understand how the coral holobiont responds to bleaching. In this study, Illumina sequencing and functional predictions were used to identify taxonomic and metabolic shifts of bacterial community in four coral species during a natural bleaching event linked to El Niño. Results showed that there were distinct differences in the coral microbiome of healthy and bleached coral, with large differences between coral species. For Acropora cytherea and Goniastrea minuta, opportunistic bacteria of Flavobacteriales, Rhodobacterales, and Vibrionales were enriched in the bleached coral. Bacterial community of Pocillopora verrucosa and Pocillopora meandrina was completely distinct from other coral species, in the case of both healthy and bleached corals. Enterobacteriales and Flavobacteriales were highly abundant in bleached coral, while Pseudomonadales, Chlorobiales, Oceanospirillales, Bacillales and Clostridiales were the characteristic groups in healthy coral. Predicted metagenome showed that functional metabolism shifts were consistent with taxon responses. The general metabolic functions in bleaching coral exhibited a different response with healthy coral. Bacterial communities displayed coral specific responses, indicating coral species played an important role in determining the microbiome even during bleaching. This study emphasized that bleaching resulting from El Niño induced a shift in coral microbiome and metabolic functions, increasing the susceptibility of coral to disease.