Bacterial scavenging of Mn and Fe in a mid- to far-field hydrothermal particle plume

The horizontally advected plumes which originate from buoyant hydrothermal fluid discharges and subsequently mix with entrained ambient sea water have been detected hundreds of kilometres from their vent sources by distinctive chemical hydrothermal tracers such as 3 He, Mn and Fe (refs 1–6). Non-conservative plume tracers, such as Mn and Fe, undergo dynamic oxidation–precipitation reactions as the plume is advected away from the vent sources 1,4,7,8 . Although some of these transformations may be mediated by microbial activity 9,10 , hydrothermal plumes have largely escaped microbiological examination beyond tens of metres from their vent origins 11,12 . Microbe–metal interactions in a hydrothermal plume were specifically addressed during our recent expedition (Vent–Plume '85) to the southern Juan de Fuca Ridge (SJFR). The early results, reported here, provide strong evidence of major microbiological influence over Mn scavenging and particulate-Mn distributions.