The responses of harmful dinoflagellate Karenia mikimotoi to simulated ocean acidification at the transcriptional level

•1121 genes were up- and 1369 down-regulated in K. mikimotoi upon ocean acidification (OA).•OA led to down-regulation of carbon concentration mechanism-related factors.•OA up-regulated energy metabolism, boosting growth and enhancing pigment content.•Increased CAT and GR activities helped acclimate to OA.•Up-regulated HSP genes enhanced tolerance of cells to low pH caused by OA.