HR: 15:10h
AN: B23G-07    [Abstracts]
TI: The Distribution and Stabilisation of Dissolved Fe in Deep-sea Hydrothermal Plumes
AU: * Bennett, S A
EM: saroban@noc.soton.ac.uk
AF: National Oceanography Centre, Southampton, University of Southampton, European Way, Southampton, SO14 3ZH, United Kingdom
AU: Achterberg, E P
AF: National Oceanography Centre, Southampton, University of Southampton, European Way, Southampton, SO14 3ZH, United Kingdom
AU: Connelly, D P
AF: National Oceanography Centre, Southampton, University of Southampton, European Way, Southampton, SO14 3ZH, United Kingdom
AU: Statham, P J
AF: National Oceanography Centre, Southampton, University of Southampton, European Way, Southampton, SO14 3ZH, United Kingdom
AU: Fones, G R
AF: National Oceanography Centre, Southampton, University of Southampton, European Way, Southampton, SO14 3ZH, United Kingdom
AU: Fones, G R
AF: University of Portsmouth, Burnaby Building, Burnaby Road, Portsmouth, PO1 3QL, United Kingdom
AU: German, C R
AF: National Oceanography Centre, Southampton, University of Southampton, European Way, Southampton, SO14 3ZH, United Kingdom
AU: German, C R
AF: Woods Hole Oceanographic Institution, Woods Hole Road, Woods Hole, MA 02543, United States
AB: Iron (Fe) is an essential micronutrient for oceanic phytoplankton, yet the debate over its sources and sinks persists. Dissolved Fe(II) in hydrothermal vent fluids is enriched ca. 10⁶-fold over open ocean values, but as vent-fluids enter the base of the water column, abundant polymetallic particulate phases are formed: predominantly Fe-rich sulfides and Fe oxyhydroxides. More recently in hydrothermal plumes, deviation from first order Fe oxidation kinetics has suggested the occurrence of organically stabilised dissolved Fe. Such stabilisation could have implications on the hydrothermal Fe flux to the deep-ocean. To study Fe stabilisation in non-buoyant hydrothermal plumes, we have investigated the plume system at 5°S, Southern Mid-Atlantic Ridge, for dissolved Fe concentrations and Fe-complexing ligands. Six CTD stations were occupied for this study that intercepted non-buoyant plumes. Along-axis flow dominated the dispersion of plume material within the ridge segment and, 2.5 km down-plume from the nearest vent-site, high concentrations of dissolved Fe (20 nM) were still present. These high levels of "dissolved" Fe could be due to the presence of Fe colloids and/or organic Fe complexes. With the use of Competitive Ligand Exchange- Cathodic Stripping Voltammetry (CLE-CSV), we have detected stabilised dissolved Fe complexes within this "dissolved" Fe fraction, on the edges of a plume. We calculate that such a stabilised Fe fraction in hydrothermal plumes, 2.9 to 5.6 times greater than deep-ocean dissolved Fe concentrations (0.7 nM), could be sufficient to provide 10-20% of the global deep-ocean dissolved Fe budget.
DE: 0409 Bioavailability: chemical speciation and complexation
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0450 Hydrothermal systems (1034, 3017, 3616, 4832, 8135, 8424)
DE: 0489 Trace element cycling (4875)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting