Characterization of an antifreeze protein from the polar diatom Fragilariopsis cylindrus and its relevance in sea ice

► Antifreeze proteins from the sea ice diatom Fragilariopsis cylindrus. ► Differential regulation of protein expression under cold and salt stress. ► Moderate thermal hysteresis and strong recrystallization inhibition, enhanced by salt. ► Ice crystal habit and pitting indicate attachment on multiple planes. ► Strong effect on ice microstructure, relevant in sea ice.