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Trichodesmiumcolonies contain an abundant microbial consortium that is likely to play a role in nutrient cycling within the colony. This study used laboratory cultures ofTrichodesmiumand two genome-sequenced strains of bacteria typical ofTrichodesmium-associated microbes to develop an understanding of the cycling of iron, a potentially limiting micronutrient, withinTrichodesmiumcolonies. We found that the ferric siderophores desferrioxamine B and aerobactin were not readily bioavailable toTrichodesmium, relative to ferric chloride or citrate-associated iron. In contrast, the representative bacterial strains we studied were able to acquire iron from all of the iron sources, implying that naturally occurringTrichodesmium-associated bacteria may be capable of utilizing a more diverse array of iron sources thanTrichodesmium. From the organism-specific uptake data collected in this study, a theoreticalTrichodesmiumcolony was designed to model whole colony iron uptake. The bacteria accounted for most (> 70%) of the iron acquired by the colony, highlighting the importance of determining organism-specific uptake in a complex environment. Our findings suggest that, although they may share the same micro-environment,Trichodesmiumand its colony-associated microbial cohort may differ substantially in terms of iron acquisition strategy.