A. anophagefferens also displayed a larger requirement for vitamin B1 compared to B12 in culture but a lower requirement for vitamin B1 compared to B12 during blooms Unlike B12, vitamin B1 is used in many different metabolic pathways and alternative compounds found in seawater that are not present in synthetic growth medium may be substituted by field populations. The biosynthesis of vitamins is complex and includes many precursor macromolecules While no algae possess the pathways to biosynthesize B12 Helliwell et al. (2011), Bertrand and Allen (2012), and Croft et al. (2006) suggested that organisms that possess genes encoding for the synthesis of some of the precursors of B1 but not the entire molecule may also be able to utilize other partially assemble B1 from their environment and complete synthesis intracellulary.