As ocean temperatures continue to rise, coral bleaching episodes are increasing in frequency, leading to a global decline in coral cover. Previous research has shown that coral hosts exposed to thermal challenges exhibit large shifts in gene expression, while gene expression patterns of their algal symbionts remain comparatively unaffected. This work led us to hypothesize that coral hosts are ‘buffering’ their symbionts under thermal challenge, which would explain the muted response. Alternatively, the algal symbiont may simply be transcriptomically unresponsive to thermal stressors that elicit responses in the host. To test our ‘host buffering’ hypothesis, Breviolum psygmophilum algal cells were isolated from the subtropical scleractinian coral Oculina arbuscula and exposed to three temperature treatments: control (maintained at 18°C), heat challenge (heated to 31°C), and cold challenge (cooled to 6°C). After 16 days in temperature ramp treatments, cultures were preserved for transcriptome profiling using TagSeq, which will allow us to characterize gene expression changes in the algal symbiont under thermal challenge in the absence of the coral host. GO enrichment analysis will be used to determine categories of genes that are being differentially regulated, and these patterns will be compared to an existing dataset exploring the response of B. psygmophilum while in hospite under identical thermal challenges. While data analysis is still ongoing, results of this experiment will provide a clearer understanding of the role of the host in determining how algal symbionts respond to thermal challenges.