Photooxidation also caused a change in morphology (formation of cracks) for PP-fibers b , but not PP-needles c and PET-fibers b (Table , column 7). We conclude that the decrease in ice nucleation ability caused by photooxidation cannot be explained by just a change in morphology observed with SEM as there was no observed relationship between the change in ice nucleation activity and change in morphology. These results also underscore the need for surface-sensitive analytical techniques to explain the relationship between photooxidation and ice nucleation ability of microplastics. Related, Teska et al.