Measurements of photosynthetic activity from melt water from sea-ice cores taken in different sea-ice cover regimes ('type' column) taken on different dates over the study period. All 'measurement' were taken in triplicate, with the average also provided here. The primary measurement was ambient and maximum fluorescence yields (F, F_m). Rapid light curves (RLCs) were measured to allow for the calculation of the slope of the light-limited portion of the RLC (α; mol é/mol photons) and the maximum of the relative electron transfer rate (ETR_max; µmol é/m²/s). The 'station' relating to the sampled core is provided to allow the user to associate these data to the environment in which the species count data were determined.