Stratospheric ozone variability continues to modulate biologically harmful UV-B radiation, exerting strong selective pressure on terrestrial green algae. These organisms have evolved protective mechanisms such as the biosynthesis of mycosporine-like amino acids (MAAs), which absorb UV radiation, thereby acting as sunscreen compounds. Here, we integrated ecophysiology and untargeted metabolomics to investigate UV-B-associated photoprotective response across six phylogenetically distinct terrestri