Increasingly extreme water temperatures caused by climate change continue to have devastating impacts on coral reefs. Corals under thermal stress will bleach, a process in which they lose their photosynthetic symbionts and become vulnerable to disease and mortality. In addition to their symbionts, corals host a diverse bacterial microbiome, which has been previously shown to influence their thermal stress response, pathogen resistance, biogeochemical cycling, and other metabolic processes that allow corals to live in oligotrophic waters. However, how the microbiome interacts with the host when algal symbionts are absent remains unclear. Here, we took advantage of the facultatively symbiotic coral, Oculina arbuscula to explore how microbial communities respond to thermal stress in naturally symbiotic and aposymbiotic colonies. Using 16S ribosomal DNA metabarcoding, we compared microbial community dynamics of coral fragments exposed to cold stress (decreasing from 18˚C to 6˚C) and heat stress (increasing from 18˚C to 32˚C) over 15 days, relative to controls maintained at 18˚C. We found that heat stress elicits a stronger shift in overall microbiome diversity in both symbiotic states, but these effects are divergent. Aposymbiotic colonies showed increased community diversity under heat stress, whereas symbiotic colonies showed a decline, associated with a pronounced increase in the prevalence of Burkholderiaceae. Cold stress led to a decrease of Burkholderiaceae in aposymbiotic colonies and an increase in a variety of other bacterial taxa. While analyses are ongoing, these results will further our understanding of bacterial influences on coral responses to temperatures by disentangling symbiont-coral-bacterial (symbiotic colonies) and coral-bacterial (aposymbiotic colonies) interactions under divergent temperature treatments.