Nico Fröhberg, together with Katja Schmidt, Sandra Pöhle, Ignacio Pedre, Maren Walter, Jonathan Mette, Sebastian Fuchs, Dieter Garbe-Schönberg, Charlotte Kleint and Andrea Koschinsky, recently published a study titled “From source to sink: complex dual role of the Kairei hydrothermal plume in deep ocean trace metal cycling at the Central Indian Ridge” in the journal Geochimica et Cosmochimica Acta.
Hydrothermal vents release large amounts of trace metals, but how much of this actually reaches the open ocean depends on processes during plume mixing that remain poorly constrained. Based on samples from RV Sonne cruise SO301 (November 2023 to January 2024) as part of the KABA project, the study follows the plume of the Kairei hydrothermal field from the vent fluids through the buoyant and non-buoyant plume to a background station 56 km away. The non-buoyant plume was sampled with the newly developed autonomous MARUM trace metal rosette for contamination-free hydrocasts. The results show that Kairei is a significant source of Fe, Mn, Co and to a lesser degree Ga to the deep Indian Ocean, while the plume acts as a sink for rare earth elements, vanadium and especially cadmium, with near-complete removal of Cd at plume depth despite its strong enrichment in the vent fluids. Size fractionation revealed that most Fe near the vent is carried as small particles and colloids that are removed quickly, while the soluble fraction is exported further. Copper and nickel showed more complex behavior, with depletion close to the vent and a later release of Cu in the far field. The comparatively low H2S/Fe ratio of the Kairei fluids likely favors greater metal transport into the water column than at more sulfide-rich systems.
Check it out here: https://doi.org/10.1016/j.gca.2026.09.018
