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Abstract
The critically endangered elkhorn coral, Acropora palmata, is affected by white pox disease (WPX) throughout the Florida Reef Tract and wider Caribbean. This dissertation examines the association of Vibrio bacteria with WPX occurrence in the Florida Keys, USA. The concentration of Vibrio was consistently greater in WPX samples compared to healthy samples across the three years (20122014). In summer 2015, we utilized a high resolution sampling approach (23 times per week) to examine changes in the A. palmata microbiome during WPX onset and progression. Microbial assemblages from new disease lesions ( 24 h) had higher levels of beta diversity (sample-to-sample) and lower levels of evenness and phylogenetic diversity. We also identifed the combination of low wind speed and high seawater temperature as important thresholds that may lead WPX lesion formation. WPX lesions healed rapidly, decreasing in size by ~29% after just 813 d and transitioned close the community composition of the healthy state within days. This suggests the coral and/or the commensal microbiota are resilient to ephemeral Vibrio blooms and that although A. palmata in the Florida Keys develop WPX signs, they may now be resistant to tissue-loss progression due to WPX. We assessed the diversity of 69 Vibrio isolates collected from diseased and apparently healthy A. palmata colonies and the surrounding seawater by multilocus sequence analysis (MLSA) and found no strong association of particular Vibrio species with health status or sample type; however, 86% of total isolates were closely related to Vibrio species with known pathogenicity to corals. Taken together, these results indicate that Vibrio may be part of a non-specific, heterotrophic bloom in WPX disease lesions. Additionally, we sequenced and assembled draft genomes of the 69 Vibrio spp. isolates. The availability of these genomes will provide an important foundation for understanding Vibrio blooming in the coral microbiome.