Chlorodendrophyceae are a class of green microalgae that have recently been discovered to form intracellular inclusions of stable amorphous calcium carbonate (ACC) that can be highly enriched in strontium. These mineral inclusions are called micropearls and are the result of a traditionally overlooked biomineralization process that is not yet fully understood. By adopting a multidisciplinary approach, the present work provides new insights into the micropearl formation process and its physiological role. Experiments performed with laboratory cultures of Tetraselmis chui suggest that micropearls must play an essential role in the species forming them and show that their formation requires high calcium and strontium uptake by the cells. Analysis of T. chui complete genome and transcriptome has allowed to identify for the first time a series of proteins that could be potentially involved in the micropearl formation process, including several calcium and bicarbonate transport proteins as well as carbonic anhydrases. Finally, this work evidences the high potential of micropearl-forming species to be used as bioremediation agents targeting strontium-90 contamination in aquatic environments.