A method for culturing a protist of the Aurantiochytrium mangrovei genus. The genus is characterized genetically and by virtue of the lipid profile thereof. The method makes it possible to obtain a high biomass yield and a lipid, and more particularly docosahexaenoic acid (DHA), enrichment of the protists thus cultured. The development of a culture medium allows the production, at high cell density, of a DHA-rich protest of the Aurantiochytrium mangrovei genus. The medium is chemically defined at low sodium ion (Na+) and chloride ion (Cl−) content.