Adult diploid and triploid Pacific oysters were exposed to environmental conditions present during marine heatwaves. Treatments included elevated seawater temperature (single stressor 30C), elevated seawater temperature followed by aerial emersion (multiple stressor 30C + 44C for 6h), and a control (20C, submerged). RNA was extracted from flash frozen ctenidium (gill) tissue samples and sequenced using the QuantSeq 3-prime mRNA-Seq (Tag-seq) protocol (v.015UG009V0251, Lexogen, Vienna, Austria).