Abstract

Meandrina meandrites is highly susceptible to stony coral tissue loss disease (SCTLD) and is one of the first coral species to die during outbreaks. The normal microflora of M. meandrites is understudied, despite the potentially critical roles they play in nutrient cycling, thermal resilience, and defense against pathogens. This study characterizes the mucosal microbiomes of healthy M. meandrites colonies from the Florida Keys, the Cayman Islands, and Belize, using the V4 region of the 16S rRNA gene. Diseased colonies from the Florida Keys were also sampled before and after antibiotic treatment during separate ex situ SCTLD experiments in order to characterize how the resident microbiomes were impacted. Similar to other coral microbiomes, Alphaproteobacteria and Gammaproteobacteria were the most abundant bacterial classes found across all samples. The most abundant taxa across samples are from the family Terasakiellaceae, which has been previously observed in healthy M. meandrites samples. Both biogeography and health state shaped microbiome composition. The antibiotic treatment stopped disease progression on treated colonies and microbiomes shifted stochastically after antibiotic treatment, suggesting that each colony responds differently to this disruption. The results of this study provide a baseline characterization of the M. meandrites microbiome that can be used to inform coral propagation efforts as well as how antibiotic treatments affect M. meandrites.

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