Distinct trends in the speciation of iron between the shallow shelf seas and the deep basins of the Arctic Ocean

Abstract

[1] The speciation of iron was investigated in three shelf seas and three deep basins of the Arctic Ocean in 2007. The dissolved fraction (<0.2 mm) and a fraction < 1000 kDa were considered here. In addition, unfiltered samples were analyzed. Between 74 and 83% of dissolved iron was present in the fraction < 1000 kDa at all stations and depth, except at the chlorophyll maximum (42-64%). Distinct trends in iron concentrations and ligand characteristics were observed from the shelf seas toward the central deep basins, with a decrease of total dissolvable iron (

Key role of organic complexation of iron in sustaining phytoplankton blooms in the Pine Island and Amundsen Polynyas (Southern Ocean)

“…While flowing along the continental shelf, the CDW is likely enriched in ligands by both fluxes from the sediments and settling organic matter produced at the sea surface that is degraded and transformed while sinking towards the sea floor. The enrichment of ligand concentrations by sediments has been observed previously in deep waters of the Kerguelen Plateau (Gerringa et al, 2008) and on Arctic shelves (Thuró czy et al, 2011b). In the Ross Sea, Fitzwater et al (2000) attributed high concentrations of particulate Fe to fluxes from the sediments from the continental shelf.…”

“…At stations sampled a few days later (4-5 days) during the bloom (St. 106 and 107, Fig. 3 The Lt/DFe ratio highlights the saturation state of the organic ligands (Thuró czy et al, 2010b(Thuró czy et al, , 2011a(Thuró czy et al, , 2011b; this ratio is consistently 41 in open ocean water samples. A low ratio (close to 1) corresponds to ligands relatively saturated with Fe and indicates a low capacity of the ligands to bind and buffer additional Fe input.…”

“…However it is difficult to assess the effect of lateral turbulent flux on TDFe, therefore this distance represents an indication of the effect and strength of the glacier source on the elevation of TDFe concentrations in this area. This suggests either that particulate Fe can be transported laterally for relatively long distances, as has been seen over the Arctic continental slope (Thuró czy et al, 2011b), or that particulate Fe near the glacier is mainly inorganic while the particulate Fe within the bloom is mostly organic (contained in phytoplankton cells). In the upper 50 m of the water column between the PIG and PIB, organic ligands became increasingly desaturated (ratio Lt/DFe increased, Figs.…”

“…The abundance of Fe in seawater is controlled by a balance between Fe input (via sediment resuspension, seaice and glacial melt, upwelling, atmospheric deposition, and hydrothermal inputs), stabilization processes via organic complexation that keep Fe in the dissolved phase, and by removal processes like (oxidative) precipitation and adsorptive scavenging (Baker and Croot, 2010;Boye et al, 2001;Croot and Johansson, 2000;Gledhill and Van Den Berg, 1994;Lannuzel et al, 2007Lannuzel et al, , 2008Lannuzel et al, , 2010Rue and Bruland, 1997;Klunder et al, 2011;Kuma et al, 1996;Nishioka and Takeda, 2000;Nishioka et al, 2001;Thuró czy et al, 2010bThuró czy et al, , 2011aThuró czy et al, , 2011b.…”

“PRISTINE”, a new high volume sampler for ultraclean sampling of trace metals and isotopes

“…This complete system has been used successfully during several cruises in the Arctic, Antarctic and Northeast Atlantic Ocean with a total of 113 full depth casts. The system proved clean to sample for dissolved Fe , the organic complexation of Fe (Thuróczy et al, 2011), dissolved Al (Middag et al, 2009), dissolved Mn , dissolved Zn , the organic speciation of Zn , dissolved Cd (Baars et al, 2014) and the stable isotopes composition of dissolved Cd (Abouchami et al, 2011;Abouchami et al, 2014;Xue et al, 2013) and Zn .…”