Natural iron enrichment around the Antarctic Peninsula in the Southern Ocean

Abstract

As part of the US-AMLR program in January-February of 2006, 99 stations in the South Shetland Islands-Antarctic Peninsula region were sampled to understand the variability in hydrographic and biological properties related to the abundance and distribution of krill in this area. Concentrations of dissolved iron (DFe) and total acid-leachable iron (TaLFe) were measured in the upper 150 m at 16 of these stations (both coastal and pelagic waters) to better resolve the factors limiting primary production in this area and in downstream waters of the Scotia Sea. The concentrations of DFe and TaLFe in the upper mixed layer (UML) were relatively high in Weddell Sea Shelf Waters (∼0.6 nM and 15 nM, respectively) and low in Drake Passage waters (∼0.2 nM and 0.9 nM, respectively). In the Brans-field Strait, representing a mixture of waters from the Wed-dell Sea and the Antarctic Circumpolar Current (ACC), concentrations of DFe were ∼0.4 nM and of TaLFe ∼1.7 nM. The highest concentrations of DFe and TaLFe in the UML were found at shallow coastal stations close to Livingston Island (∼1.6 nM and 100 nM, respectively). The ratio of TaLFe:DFe varied with the distance to land: ∼45 at the shallow coastal stations, ∼15 in the high-salinity waters of Bransfield Strait, and ∼4 in ACC waters. Concentrations of DFe increased slightly with depth in the water column, while that of TaLFe did not show any consistent trend with depth. Our Fe data are discussed in regard to the hydrography Correspondence to: M. V. Ardelan (murato@nt.ntnu.no) and water circulation patterns in the study area, and with the hypothesis that the relatively high rates of primary production in the central regions of the Scotia Sea are partially sustained by natural iron enrichment resulting from a northeast-erly flow of iron-rich coastal waters originating in the South Shetland Islands-Antarctic Peninsula region.

The significant inputs of trace elements and rare earth elements from melting glaciers in Antarctic coastal waters

“…The levels of Fe for the reagent blanks (ultra-pure HNO3, CH 3 COOH, NH 3 and ammonium acetate solution, n018) and procedural blanks (n025) were 0.190.04 nM and 0.390.1 nM, respectively. Our total blank level of Fe was similar to the values from other recent studies (0.1Á0.25 nM) that used different analytical methods (Ardelan et al 2010;Milne et al 2010;Lee et al 2011). The detection limit of Fe was 0.14 nM, which was three times the standard deviation of the instrumental blanks.…”

“…The Chelex 100 blank for Fe was B0.36 nM, which falls in the range of blanks from other studies (0.290.08 nM Fe) using the same resin (Ö ztü rk 1995; Ardelan et al 2010). The levels of Fe for the reagent blanks (ultra-pure HNO3, CH 3 COOH, NH 3 and ammonium acetate solution, n018) and procedural blanks (n025) were 0.190.04 nM and 0.390.1 nM, respectively.…”

“…These phases were not retained by the physical filtration process as they are much smaller than the pore size of the packed column (10 mm), and it was therefore considered that they were retained by a surface reaction or binding. The concentrations of dissolved trace elements (including Fe) in water samples were measured using the Chelex 100 resin column method developed by Lewis & Landing (1991), Ö ztü rk (1995), Ö ztü rk et al (2003) and Ardelan et al (2010), and recently improved by Kim (2011) andJeong et al (2012). Briefly, the aqueous samples (100Á 500 mL) were adjusted to pH 5.7Á5.9 using pure CH 3 COOH (99.7%, Junsei Chemical Co., Tokyo, Japan) and NH 3 (28%, Junsei).…”

Iron biogeochemistry across marine systems – progress from the past decade

“…They show that horizontal advection of water from South of the Plateau seems to be the predominant source of apparent particulate and dissolved iron above the plateau, over atmospheric and vertical inputs. Further, Ardelan et al (2010) illustrate natural Fe enrichment processes from the South Shetland Islands-Antarctic Peninsula region.…”

“…We follow the structure of the workshop topics, which were: Natural Fe fertilization (Sect. 2, articles: Ardelan et al, 2010;Chever et al, 2010;Duggen et al, 2010;Ye et al, 2009); artificial Fe fertilization (3: Bucciarelli et al, 2010;Chever et al, 2010); Fe inputs into coastal and estuarine systems (4: Breitbarth et al, 2009); Colloidal iron and organic matter (5); Linking biological processes to iron chemistry (6: Breitbarth et al, 2009;Bucciarelli et al, 2010;Hassler and Schoemann, 2009;Steigenberger et al, 2010); and Iron and Climate Change (7: Breitbarth et al, 2010;Rose et al, 2009). Each section concludes with recommendations for future research.…”