Here we evaluate the biological response (mortality, growth and net calcification rates) of a marine calcifier, the larvae of the sea urchin Echinus esculentus, to different levels of variability of pCO2/pH imposed in the absence or presence of seagrass and under 4 different pHs, relevant in the context of present natural variability and future ocean acidification.This dataset is included in the OA-ICC data compilation maintained in the framework of the IAEA Ocean Acidification International Coordination Centre (see https://oa-icc.ipsl.fr). Original data were provided by the author of the related paper (see Related to) to the OA-ICC data curator. In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Gattuso et al, 2024) 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 2024-06-14.