The data sets stem from a study which aimed to investigate the impact of chronic severe hypercapnia on the cellular stress response in the gills of juvenile turbot (Psetta maxima). The experiment was conducted in the so called respirometer, a recirculating aquaculture respirometer system (RARS) which allowed the persistent, stable manipulation of carbon dioxide concentrations. Juvenile turbot (Psetta maxima) where subjected to different levels of environmental hypercapnia (low: ~3000 μatm, medium: ~15000 μatm, high: ~25000 μatm). After eight weeks, fish where sacrificed and gill samples were taken for further histological and transcriptional analysis. For histological investigation of the gills, samples where fixed in 4% phosphate-buffered formalin and examined via a microscope equipped with a digital camera. In order to investigate changes in the transcriptome, a fraction of the gill samples was stored in RNAlater. Relative gene expression analysis was conducted via RT-qPCR, using a Fluidigm chip system. Calibrated normalized relative quantities (CNRQs) where assessed with the QBASE software. This included the evaluation of the most suitable combination of reference genes with the help of the GeNorm algorithm.

In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Gattuso et al, 2019) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation by seacarb is 2020-07-07.