Field,Full form,Description,Notes BS,Baltic Sea experiment,Data obtained from the Baltic Sea experiment,"Dataset and additional figures A2-A5 with data from BS only: ""BS_only_Sr_Ca_vs_ultrastructure_data.csv"" and ""BS_only_figures_A2-A5.pdf""" GOM,Gulf of Maine experiment,Data obtained from the Gulf of Maine experiment, T,temperature,Stable water temperature regime of the laboratory tank (°C), OSL,outer shell layer,Outer shell layer of the ventral margin of the shell, oOSL,outer portion of the OSL,"Outer portion of the OSL, dominated by homogeneous ultrastructure", iOSL,inner portion of the OSL,"Inner portion of the OSL, dominated by crossed-acicular ultrastructure", BMU,biomineral unit,Individual building block of the ultrastructure, Sr_Ca,Sr/Ca,Shell Sr/Ca (mmol/mol), GR,growth rate,Individual daily shell growth rate (µm/day), AR,BMU area,Size of the BMUs (µm²),15 % largest BMUs taken into account EL,BMU elongation,"Elongation of the BMUs, estimated by the length/width of an ellipse fitted to each BMU",15 % largest BMUs taken into account d,detrended,Data from which the influence of GR and/or AR and/or EL was mathematically eliminated, _w,weighted,Data for which median values weighted per the number of specimens at each temperature regime were used, _spec,specimen,Data for which medians values for each specimen were used, _nonw,non weighted,Data for which median values for each temperature regime were used, _linalt,linear alternative,Data for which the alternative linear detrending method was applied,"if _linalt is not mentioned, the natural logarithm detrending method was used" PI,prediction interval,Temperature prediction intervals computed from detrended and undetrended Sr/Ca data,"_low and _up denote lower and upper limits of each PI of temperature, respectively (°C)" REG,regression,Regression values obtained from measured Sr/Ca data and used to compute PIs,