Chrysochromulina mactra is a marine haptophyte microalga belonging to the genus Chrysochromulina, class Prymnesiophyceae. The epithet mactra, meaning kneading trough or trough-shaped vessel, describes a morphological feature of the organism — likely the shape of a scale element or cellular structure visible through electron microscopy. Within Chrysochromulina, fine-scale ultrastructural characters of the cell surface and appendages are the primary basis for species identification, making high-resolution electron microscopy essential for taxonomic work. C. mactra has been recorded from Norwegian coastal marine environments, a region that has historically served as a major source of newly described haptophyte species due to focused research programs and the ecological richness of Norwegian fjord and shelf waters. These environments are influenced by cold North Atlantic currents and seasonal nutrient dynamics that support productive phytoplankton communities in which nanoplankton species like C. mactra play significant roles. As a member of Prymnesiophyceae, the species possesses chloroplasts with chlorophylls a and c and fucoxanthin-type pigments, enabling photosynthetic carbon fixation. The coiling haptonema is a diagnostic feature of Chrysochromulina distinguishing it from related genera including Prymnesium and Haptolina. C. mactra has not been formally assessed under IUCN criteria and is listed as Not Evaluated. As with most marine nanoplankton, its population status and extinction risk cannot be meaningfully quantified with current survey methods.