To survive, organisms must deploy a range of molecular, physiological, and behavioral responses to avoid or counteract harmful environmental conditions. Often these responses to environmental stressors are complex, involving many mechanisms and interactions at cellular and organismal levels. Frequently an organism's response to environmental stressors, whether natural or anthropogenic, will involve changes in gene expression and regulation that consequently will alter physiology, development, or behavior. Moreover, animal origin and past growth conditions (e.g., in the field or laboratory) will change its response altogether. In this work, we present and discuss the differences in response to short-term thermal stress of lab-cultured and field-conditioned Nematostella vectensis. Using ATAC-seq and RNA-seq data, we found that the ability to effectively respond to stress is higher in field-conditioned animals, suggesting that acclimation by these animals prepares them to mount an efficient stress response. Field-conditioned animals had a more concentrated reaction, expressed as enrichment of the DNA repair mechanism pathway, while lab animals had a more diffuse reaction that involved a larger number of differentially expressed genes and enriched pathways including amino acid metabolism. Overall, this work presents the importance of experimentally addressing ecological questions in the field as many molecular mechanisms are altered compared to lab conditions.