Measurements of organic complexation of iron during the CARUSO-EISENEX experiment

• Main Authors: Boyé, Marie, Nishioka, Jun, Croot, Peter L, Laan, Patrick, Timmermans, Klaas R, de Baar, Hein J W
• Format: Dataset
• Language: English
• Published: PANGAEA 2005
• Subjects: ANT-XVIII/2; Date/Time of event; DEPTH; water; EisenEx; Elevation of event; European Iron Enrichment Experiment in the Southern Ocean; Event label; GOFLO; Go-Flo bottles; Iron; colloidal; dissolved; conditional complex stability; inorganic; dissolved organic/dissolved inorganic ratio; soluble; Iron-binding ligand; Latitude of event; Longitude of event; Polarstern; PS58/007-6; PS58/009-7; PS58/011-7; PS58/014-7; PS58/038-6; PS58/041-3; PS58/045-3; PS58/046-2; PS58/048-2; PS58/049-4; PS58/061-2; PS58/088-8; PS58/091-2; PS58/092-2; PS58/107-8; PS58 EISENEX; South Atlantic; Southern Ocean
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.770166; https://doi.org/10.1594/PANGAEA.770166

The speciation of strongly chelated iron during the 22-day course of an iron enrichment experiment in the Atlantic sector of the Southern Ocean deviates strongly from ambient natural waters. Three iron additions (ferrous sulfate solution) were conducted, resulting in elevated dissolved iron concentrations (Nishioka, J., Takeda, S., de Baar, H.J.W., Croot, P.L., Boye, M., Laan, P., Timmermans, K.R., 2005, Changes in the concentration of iron in different size fractions during an iron enrichment experiment in the open Southern Ocean. Marine Chemistry, doi:10.1016/j.marchem.2004.06.040) and significant Fe(II) levels (Croot, P.L., Laan, P., Nishioka, J., Strass, V., Cisewski, B., Boye, M., Timmermans, K.R., Bellerby, R.G., Goldson, L., Nightingale, P., de Baar, H.J.W., 2005, Spatial and Temporal distribution of Fe(II) and H2O2 during EisenEx, an open ocean mescoscale iron enrichment. Marine Chemistry, doi:10.1016/j.marchem.2004.06.041). Repeated vertical profiles for dissolved (filtrate < 0.2 µm) Fe(III)-binding ligands indicated a production of chelators in the upper water column induced by iron fertilizations. Abiotic processes (chemical reactions) and an inductive biologically mediated mechanism were the likely sources of the dissolved ligands which existed either as inorganic amorphous phases and/or as strong organic chelators. Discrete analysis on ultra-filtered samples (< 200 kDa) suggested that the produced ligands would be principally colloidal in size (> 200 kDa-< 0.2 µm), as opposed to the soluble fraction (< 200 kDa) which dominated prior to the iron infusions. Yet these colloidal ligands would exist in a more transient nature than soluble ligands which may have a longer residence time. The production of dissolved Fe-chelators was generally smaller than the overall increase in dissolved iron in the surface infused mixed layer, leaving a fraction (about 13-40%) of dissolved Fe not bound by these dissolved Fe-chelators. It is suggested that this fraction would be inorganic colloids. The ...