In Nannochloropsis oceanica IMET1, transcript knockdown of a cytosolic carbonic anhydrase (CA2 g2018) specifically inhibited by HC resulted in ~45%, ~30% and ~40% elevation of photosynthetic oxygen evolution rate, growth rate and biomass accumulation rate under high CO2 (5% ), respectively. This CA2-knockdown mutant is demonated as M2. To probe mechanistic links underlying the mutant (M2 RNAi-knockdown line of carbonic anhydrase (CA2)) phenotypes, temporal transcriptomic profiles are compared between RNAi-knockdown line of carbonic anhydrase (CA2) and WT, at 12 h and 24h under high CO2 (5%). Overall design: Nannochloropsis oceanica IMET1 wild-type and M2 (RNAi-knockdown line of carbonic anhydrase (CA2)) cells were grown in liquid cultures under continuous light (approximately 80±5 µmol photons m-2 s-1) at 25? and aerated by bubbling with a mixture of 5% CO2 in air. Mid-logarithmic phase algal cells were collected and washed three times with axenic seawater. Equal numbers of cells were re-inoculated in fresh medium and cultured under 5% CO2. Cell aliquots of WT and M2 were collected for RNA isolation after being transferred to the fresh medium conditions for 12h and 24h. Three biological replicates were randomly selected to prepare mRNA-Seq library. In total, 12 samples collected at two time points (12h and 24h) were used for mRNA-Seq library preparation and then submitted to Illumina HiSeq 2000 for sequencing. Please note that [1] each FPKM.txt processed data file contains 3 data columns (one for each replicate) and is linked to the corresponding 'replicate1' sample records, [2] the M2_WT_*FPKM.txt files contain the merged data of each sample group for the indicated time point and are linked as Series supplementary files.