Isochrysis sp.'s responses to temperature (2 vs. 6 °C), light (55 vs. 160 µmol photons m-2 s-1) and pCO2 (400 vs. 1000 µatm)

We assessed the responses of solitary cells of Arctic Isochrysis sp. (Strain PS78) grown under a matrix of temperature (2°C vs. 6°C), light intensity (55 vs. 160 μmol photons m-2 s-1) and CO2 partial pressures (pCO2; 400 vs. 1000 μatm). Before the experiments, the strain (isolated during Polarstern cruise PS78 in 2011) was kept as stock culture at 1° in 0.2 µm sterile-filtered Arctic seawater (Salinity 33), enriched with vitamins and trace metals according to F/2 medium (Guillard & Ryther, 1962). Nitrate and phosphate were added in concentrations of 100 and 6 µmol L-1, respectively. Experiments were conducted between May 2016 and September 2017 at the Alfred-Wegener-Institute, using standardized media and continuous light exposition. Next to acclimation parameters (growth rates, particulate and dissolved organic carbon and nitrogen, chlorophyll a content), we measured physiological processes in-vivo (electron transport rates and net photosynthesis) using fast-repetition rate fluorometry and membrane-inlet mass spectrometry.