Microbial Communities and their Functional Role Associated with the Localised Outbreak of Coral Growth Anomalies in Eastern Arabian Sea.

Growth anomalies of corals are characterized by spherical or irregular-shaped overgrowth of the coral skeleton that can drain the coral's energy and suppress coral growth. A localised outbreak of growth anomalies with a 40% prevalence rate in Turbinaria mesenterina colonies was observed during March 2018 in the study area. To further investigate, we characterised the gross morphology and used 16S rRNA amplicon sequencing to compare the bacterial communities associated with healthy and growth anomalies affected T. mesenterina colonies. Significant changes were observed in the bacterial communities where the Bacteroides group dominant in the healthy corals was replaced by opportunistic groups like Planctomycetes, Verrucomicrobia, Acidobacteria, and Cyanobacteria. Several human pathogens and copiotrophic coral pathogens were detected in the diseased colonies, indicative of an immune-compromised coral by harbouring opportunistic bacteria. The presence of human pathogens and fecal enterobacteria is an indicator of anthropogenically polluted reefs. Functional annotation revealed a major shift in bacterial community governing sulphur and nitrogen cycling that indicates metabolic changes in GA-affected corals. This study reports the first incidence of GA outbreak in the marginal reef of Grande Island and provides information on the pattern and role of the associated microbial community.

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Supplementary information: The online version contains supplementary material available at 10.1007/s12088-024-01410-7.