Mixotrophy in the bloom-forming genus Phaeocystis and other haptophytes

•Phaeocystis globosa cells contained bacteria, suggesting mixotrophy.•Mixotrophy in P. globosa supported by gene-based prediction model.•Additional prediction for mixotrophy in P. antarctica and 23 other haptophytes.•Mixotrophy seems widespread across all major lineages of the haptophytes.•Mixotrophy may support haptophyte blooms at low nutrient conditions.