Colonies of the marine cyanobacterium Trichodesmium optimize dust utilization by selective collection and retention of nutrient-rich particles

Trichodesmium, a globally important, N₂-fixing, and colony-forming cyanobacterium, employs multiple pathways for acquiring nutrients from air-borne dust, including active dust collection. Once concentrated within the colony core, dust can supply Trichodesmium with nutrients. Recently, we reported a selectivity in particle collection enabling Trichodesmium to center iron-rich minerals and optimize its nutrient utilization. In this follow-up study we examined if colonies select Phosphorus (P) minerals. We incubated 1,200 Trichodesmium colonies from the Red Sea with P-free CaCO₃, P-coated CaCO₃, and dust, over an entire bloom season. These colonies preferably interacted, centered, and retained P-coated CaCO₃ compared with P-free CaCO₃. In both studies, Trichodesmium clearly favored dust over all other particles tested, whereas nutrient-free particles were barely collected or retained, indicating that the colonies sense the particle composition and preferably collect nutrient-rich particles. This unique ability contributes to Trichodesmium's current ecological success and may assist it to flourish in future warmer oceans.