This datafile summarizes data collected for a meta-analyses by literature searches using WoS. Collected data concerned the maximum photosynthetic rates (Vmax) and half-saturation concentrations of CO2 (Km) for photosynthesis in marine phytoplankton, including the standard deviations (Vmax.SD and Km.SD) and number of replicates for these parameters (N). Distinct units are provided (units.Vmax and units.Km). Maximum photosynthetic rates were based on oxygen evolution (O2evol) or carbon fixation (Cfix) as provided in the datafile (O2evol.Cfix). In the latter case, a photosynthetic quotient of 1 was used. Units for Vmax were converted to umol O2 (mg chla)-1 h-1, if required data to do this was provided (e.g. cellular chlorophyll-a content). When only standard errors (SE) were provided, the standard deviations (SD) were calculated by SD=SE*sqrt(n), where n is the number of replicates. When uptake kinetics were provided but not fitted parameters, we performed a Michaelis Menten model to the data to retrieve Vmax and Km. Data was collected for different CO2 treatments with distinct CO2 partial pressure. Treatment values are reported in the datafile based on CO2 (CO2.ppm), pH and and Dissolved Inorganic Carbon concentration (DIC), and were annotated to control or elevated CO2 treatments (CO2_treatment). The data file furthermore reports the original reference (Reference) and its year (Year), highest phytoplankton taxonomic group (Group), Genus, Species and Strain names, as well as habitate (Niche) and light level (Light) where values report Photosynthetic Active Radiation in [umol photons m-2 s-1].