ORCID Profile
0000-0002-7428-8030
Current Organisation
University of Tasmania Institute for Marine and Antarctic Studies
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Publisher: Elsevier BV
Date: 03-2011
Publisher: American Geophysical Union (AGU)
Date: 08-2016
DOI: 10.1002/2016JC011687
Publisher: American Geophysical Union (AGU)
Date: 12-2019
DOI: 10.1029/2019JC015221
Publisher: Elsevier BV
Date: 11-2013
Publisher: Wiley
Date: 06-2022
Publisher: CSIRO Publishing
Date: 2017
DOI: 10.1071/MF16335
Abstract: This review aims to bring into focus the current understanding of hydrothermal systems and plume dynamics, tracers of hydrothermalism and the contribution of iron from hydrothermal vents to the global oceanic iron budget. The review then explores hydrothermal effect on surface ocean productivity. It is now well documented that scarcity of iron limits the production of chlorophyll-producing organisms in many regions of the ocean that are high in macronutrients. However, it is only recently that hydrothermal inputs have gained recognition as a source of Fe to the deep oceans that may potentially affect surface ocean productivity in some regions. A compilation of iron measurements from hydrothermal vents reveals that although hydrothermal studies measuring iron have increased significantly in recent years, there is still a dearth of data below 40°S. New analytical approaches for tracing iron sources, coupled with increasing s ling coverage of the oceans, is quickly improving knowledge of the effect of hydrothermal sources on biogeochemical cycles, a vital component in predicting future climate scenarios.
Publisher: Copernicus GmbH
Date: 21-02-2020
Abstract: Abstract. Dissolved Fe (DFe) s les from the GEOVIDE voyage (GEOTRACES GA01, May–June 2014) in the North Atlantic Ocean were analyzed using a seaFAST-pico™ coupled to an Element XR sector field inductively coupled plasma mass spectrometer (SF-ICP-MS) and provided interesting insights into the Fe sources in this area. Overall, DFe concentrations ranged from 0.09±0.01 to 7.8±0.5 nmol L−1. Elevated DFe concentrations were observed above the Iberian, Greenland, and Newfoundland margins likely due to riverine inputs from the Tagus River, meteoric water inputs, and sedimentary inputs. Deep winter convection occurring the previous winter provided iron-to-nitrate ratios sufficient to sustain phytoplankton growth and lead to relatively elevated DFe concentrations within subsurface waters of the Irminger Sea. Increasing DFe concentrations along the flow path of the Labrador Sea Water were attributed to sedimentary inputs from the Newfoundland Margin. Bottom waters from the Irminger Sea displayed high DFe concentrations likely due to the dissolution of Fe-rich particles in the Denmark Strait Overflow Water and the Polar Intermediate Water. Finally, the nepheloid layers located in the different basins and at the Iberian Margin were found to act as either a source or a sink of DFe depending on the nature of particles, with organic particles likely releasing DFe and Mn particle scavenging DFe.
Publisher: Cambridge University Press (CUP)
Date: 2018
DOI: 10.1017/PASA.2018.9
Abstract: We present a multi-frequency study of the intermediate spiral SAB(r)bc type galaxy NGC 6744, using available data from the Chandra X-Ray telescope, radio continuum data from the Australia Telescope Compact Array and Murchison Widefield Array , and Wide-field Infrared Survey Explorer infrared observations. We identify 117 X-ray sources and 280 radio sources. Of these, we find nine sources in common between the X-ray and radio catalogues, one of which is a faint central black hole with a bolometric radio luminosity similar to the Milky Way’s central black hole. We classify 5 objects as supernova remnant (SNR) candidates, 2 objects as likely SNRs, 17 as H ii regions, 1 source as an AGN the remaining 255 radio sources are categorised as background objects and one X-ray source is classified as a foreground star. We find the star-formation rate (SFR) of NGC 6744 to be in the range 2.8–4.7 M ⊙ ~yr − 1 signifying the galaxy is still actively forming stars. The specific SFR of NGC 6744 is greater than that of late-type spirals such as the Milky Way, but considerably less that that of a typical starburst galaxy.
Publisher: Wiley
Date: 24-04-2021
DOI: 10.1002/LNO.11772
Abstract: Manganese (Mn) is an abundant element in the Earth's crust. However, its concentrations in open ocean seawater are low, where external inputs are scarce. In this study, we report the dissolved Mn and particulate Mn distributions in the Southern Ocean, measured along the GEOTRACES—SR3 transect, from Tasmania (Australia) to Antarctica in the Southern Ocean, during the austral summer 2018. Both dissolved Mn and particulate Mn concentrations were generally low away from localized sources ( 0.3 nmol L −1 and 0.1 nmol L −1 , respectively) along the transect. Our observations of a lower labile particulate fraction than previously measured suggest the Southern Ocean has a unique particulate Mn composition. Low surface dissolved Mn concentrations were attributed to biological uptake and few external sources. Our results suggest biological control of the Mn cycle was higher above the Antarctic continental slope, compared to the rest of the section, and our particulate Mn : P ratios indicated the presence of iron‐stressed diatoms south of the Sub‐Antarctic Front. We suggest low dissolved Mn surface concentrations may (co‐)limit phytoplankton growth in this region. Localized higher dissolved Mn concentrations were observed due to external sources, such as sedimentary and hydrothermal inputs. The presence of an eddy at the same latitude as a hydrothermal plume induced an upwelling of hydrothermally enriched waters up to 1000 m however, no dissolved Mn inputs to the surface waters were observed. We suggest previous dissolved Mn inputs to the surface layer may be obscured by biological uptake.
Publisher: Wiley
Date: 27-04-2020
Publisher: Copernicus GmbH
Date: 04-04-2018
Publisher: American Geophysical Union (AGU)
Date: 08-2023
DOI: 10.1029/2022GB007613
Abstract: Manganese (Mn) is an essential element involved in photosynthesis, yet its concentrations in Southern Ocean open waters are very low, arising from biological uptake and limited external inputs. At southern latitudes, waters overlying the Antarctic shelf are expected to have much higher Mn concentrations due to their proximity to external sources. In this study, we investigated the potential export of Mn‐rich Antarctic shelf waters toward depleted open Southern Ocean waters. Our results showed that while high Mn concentrations were observed over the shelf, biological uptake decreased dissolved Mn concentrations in surface waters north of the South Antarctic Circumpolar Current Front ( .1 nmol kg −1 ), limiting its export. Conversely, mixing between Mn‐rich Antarctic Bottom Waters and Mn‐depleted Lower Circumpolar Deep Waters combined with oxidative and scavenging processes led to a decrease in dissolved Mn concentrations within bottom waters, with distance from the coast. Particulate Mn concentrations also showed a decreasing trend with distance from the coast. A comparison with other Antarctic coastal regions suggests this bottom water Mn removal may be widespread and that East Antarctica may be characterized by lower Mn concentrations compared to other regions. Still, subsurface dissolved Mn maxima (0.3–0.6 nmol kg −1 ) represented a potential reservoir for surface waters. We hypothesize that these high subsurface values result from external sources near the shelf. Overall, these results suggest that the moderate lateral export of trace metal‐enriched waters contributes to the extremely low and potentially limiting Mn concentrations previously reported further north in this Southern Ocean region.
Publisher: Elsevier BV
Date: 09-2016
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/MF13137
Abstract: The Tasman Sea and the adjacent subantarctic zone (SAZ) are economically important regions, where the parameters controlling the phytoplankton community composition and carbon fixation are not yet fully resolved. Contrasting nutrient distributions, as well as phytoplankton biomass, bio ersity and productivity were observed between the North Tasman Sea and the SAZ. In situ photosynthetic efficiency (FV/FM), dissolved and particulate nutrients, iron biological uptake, and nitrogen and carbon fixation were used to determine the factor-limiting phytoplankton growth and productivity in the North Tasman Sea and the SAZ. Highly productive cyanobacteria dominated the North Tasman Sea. High atmospheric nitrogen fixation and low nitrate dissolved concentrations indicated that non-diazotroph phytoplankton are nitrogen limited. Deck-board incubations also suggested that, at depth, iron could limit eukaryotes, but not cyanobacteria in that region. In the SAZ, the phytoplankton community was dominated by a bloom of haptophytes. The low productivity in the SAZ was mainly explained by light limitation, but nitrogen, silicic acid as well as iron were all depleted to the extent that they could become co-limiting. This study illustrates the challenge associated with identification of the limiting nutrient, as it varied between phytoplankton groups, depths and sites.
Publisher: Elsevier BV
Date: 08-2018
Publisher: American Geophysical Union (AGU)
Date: 02-2018
DOI: 10.1002/2017GB005736
Publisher: American Geophysical Union (AGU)
Date: 08-2018
DOI: 10.1029/2018JC013932
Publisher: Elsevier BV
Date: 04-2014
Publisher: Elsevier BV
Date: 09-2016
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C3AY41312H
Abstract: A simplified, automated, low cost, portable, off-line extraction method with high throughput for trace metal analysis in seawater by SF-ICP-MS.
Publisher: Frontiers Media SA
Date: 14-06-2019
Publisher: Elsevier BV
Date: 08-2013
Publisher: Copernicus GmbH
Date: 06-02-2015
Abstract: Abstract. The KEOPS2 project aims to elucidate the role of natural Fe fertilisation on biogeochemical cycles and ecosystem functioning, including quantifying the sources and processes by which iron is delivered in the vicinity of the Kerguelen Archipelago, Southern Ocean. The KEOPS2 process study used an upstream high-nutrient, low-chlorophyll (HNLC), deep water (2500 m), reference station to compare with a shallow (500 m), strongly fertilised plateau station and continued the observations to a downstream, bathymetrically trapped recirculation of the Polar Front where eddies commonly form and persist for hundreds of kilometres into the Southern Ocean. Over the Kerguelen Plateau, mean particulate (1–53 μm) Fe and Al concentrations (pFe = 13.4 nM, pAl = 25.2 nM) were more than 20-fold higher than at an offshore (lower-productivity) reference station (pFe = 0.53 nM, pAl = 0.83 nM). In comparison, over the plateau dissolved Fe levels were only elevated by a factor of ~ 2. Over the Kerguelen Plateau, ratios of pMn / pAl and pFe / pAl resemble basalt, likely originating from glacial/fluvial inputs into shallow coastal waters. In downstream, offshore deep-waters, higher pFe / pAl, and pMn / pAl ratios were observed, suggesting loss of lithogenic material accompanied by retention of pFe and pMn. Biological uptake of dissolved Fe and Mn and conversion into the biogenic particulate fraction or aggregation of particulate metals onto bioaggregates also increased these ratios further in surface waters as the bloom developed within the recirculation structure. While resuspension of shelf sediments is likely to be one of the important mechanisms of Fe fertilisation over the plateau, fluvial and glacial sources appear to be important to areas downstream of the island. Vertical profiles within an offshore recirculation feature associated with the Polar Front show pFe and pMn levels that were 6-fold and 3.5-fold lower, respectively, than over the plateau in surface waters, though still 3.6-fold and 1.7-fold higher respectively than the reference station. Within the recirculation feature, strong depletions of pFe and pMn were observed in the remnant winter water (temperature-minimum) layer near 175 m, with higher values above and below this depth. The correspondence between the pFe minima and the winter water temperature minima implies a seasonal cycle is involved in the supply of pFe into the fertilised region. This observed association is indicative of reduced supply in winter, which is counterintuitive if sediment resuspension and entrainment within the mixed layer is the primary fertilising mechanism to the downstream recirculation structure. Therefore, we hypothesise that lateral transport of pFe from shallow coastal waters is strong in spring, associated with snow melt and increased runoff due to rainfall, drawdown through summer and reduced supply in winter when snowfall and freezing conditions predominate in the Kerguelen region.
Publisher: Copernicus GmbH
Date: 04-04-2018
DOI: 10.5194/BG-2018-147
Abstract: Abstract. Dissolved Fe (DFe) s les from the GEOVIDE voyage (GEOTRACES GA01, May–June 2014) in the North Atlantic Ocean were analysed using a SeaFAST-picoTM coupled to an Element XR HR-ICP-MS and provided interesting insights on the Fe sources in this area. Overall, DFe concentrations ranged from 0.09 ± 0.01 nmol L−1 to 7.8 ± 0.5 nmol L−1. Elevated DFe concentrations were observed above the Iberian, Greenland and Newfoundland Margins likely due to riverine inputs from the Tagus River, meteoric water inputs and sedimentary inputs. Air-sea interactions were suspected to be responsible for the increase in DFe concentrations within subsurface waters of the Irminger Sea due to deep convection occurring the previous winter, that provided iron-to-nitrate ratios sufficient to sustain phytoplankton growth. Increasing DFe concentrations along the flow path of the Labrador Sea Water were attributed to sedimentary inputs from the Newfoundland Margin. Bottom waters from the Irminger Sea displayed high DFe concentrations likely due to the dissolution of Fe-rich particles from the Denmark Strait Overflow Water and the Polar Intermediate Water. Finally, the nepheloid layers were found to act as either a source or a sink of DFe depending on the nature of particles.
Publisher: Elsevier BV
Date: 05-2019
DOI: 10.1016/J.TALANTA.2019.01.047
Abstract: A seawater preconcentration system (seaFAST) with offline sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS) detection was critically evaluated for ultra-low trace elemental analysis of Southern Ocean s les over a four-year period (2015-2018). The commercially available system employs two Nobias PA1 resin columns for buffer cleaning and s le preconcentration, allowing salt matrix removal with simultaneous extraction of a range of trace elements. With a primary focus on method simplicity and practicality, a range of experimental parameters relevant to oceanographic analysis were considered, including reduction of blank levels (over weeks and years), instrument conditioning, extraction efficiencies over different pH ranges (5.8-6.4), and preconcentration factors (~10-70 times). Conditions were optimised for the analysis of ten important trace elements (Cd, Co, Cu, Fe, Ga, Mn, Ni, Pb, Ti and Zn) in open ocean seawater s les, and included initial pre-cleaning and conditioning of the seaFAST unit for one week before each separate analytical sequence a controlled narrow buffer pH of 6.20 ± 0.02 used for extraction and a s le preconcentration factor of 10 for (relatively) concentrated rainwater or sea ice, 40 for typical seawater s les, and up to 67 times for seawater s les collected in the remote open ocean such as the Southern Ocean. Method accuracy (both short - days to weeks - and long term - months to years) were evaluated through extensive analysis of a range of oceanographic standard reference s les including SAFe D1 (n = 20), D2 (n = 3), S (n = 15), GEOTRACES GD (n = 6), GSC (n = 42) and GSP (n = 42), as well as NASS-6 (n = 6). Measured values for oceanographic s les were found to agree with consensus values to within ± 6% for Cd, Cu, Fe, Ni, Pb and Zn. Offsets were noted for Co (labile fraction only no UV oxidation), Mn (difference also noted in other recent studies) and Ti (limited reference values). No consensus values currently exist for Ga. Iron and Mn in Southern Ocean s les were also independently verified via flow injection analysis methods (R
Publisher: Elsevier BV
Date: 08-2015
Publisher: American Geophysical Union (AGU)
Date: 11-2012
DOI: 10.1029/2012GL053478
Publisher: Elsevier BV
Date: 12-2015
Publisher: Copernicus GmbH
Date: 29-07-2015
Abstract: Abstract. Iron availability in the Southern Ocean controls phytoplankton growth, community composition and the uptake of atmospheric CO2 by the biological pump. The KEOPS-2 (KErguelen Ocean and Plateau compared Study 2) "process study", took place around the Kerguelen Plateau in the Indian sector of the Southern Ocean. This is a region naturally fertilised with iron on the scale of hundreds to thousands of square kilometres, producing a mosaic of spring blooms which show distinct biological and biogeochemical responses to fertilisation. This paper presents biogeochemical iron budgets (incorporating vertical and lateral supply, internal cycling, and sinks) for three contrasting sites: an upstream high-nutrient low-chlorophyll reference, over the plateau and in the offshore plume east of the Kerguelen Islands. These budgets show that distinct regional environments driven by complex circulation and transport pathways are responsible for differences in the mode and strength of iron supply, with vertical supply dominant on the plateau and lateral supply dominant in the plume. Iron supply from "new" sources (diffusion, upwelling, entrainment, lateral advection, atmospheric dust) to the surface waters of the plume was double that above the plateau and 20 times greater than at the reference site, whilst iron demand (measured by cellular uptake) in the plume was similar to that above the plateau but 40 times greater than at the reference site. "Recycled" iron supply by bacterial regeneration and zooplankton grazing was a relatively minor component at all sites ( 8 % of new supply), in contrast to earlier findings from other biogeochemical iron budgets in the Southern Ocean. Over the plateau, a particulate iron dissolution term of 2.5 % was invoked to balance the budget this approximately doubled the standing stock of dissolved iron in the mixed layer. The exchange of iron between dissolved, biogenic particulate and lithogenic particulate pools was highly dynamic in time and space, resulting in a decoupling of the iron supply and carbon export and, importantly, controlling the efficiency of fertilisation.
Publisher: American Geophysical Union (AGU)
Date: 31-08-2010
DOI: 10.1029/2009JG001031
Publisher: Copernicus GmbH
Date: 23-06-2015
Abstract: Abstract. This study examined upper-ocean particulate organic carbon (POC) export using the 234Th approach as part of the second KErguelen Ocean and Plateau compared Study expedition (KEOPS2). Our aim was to characterize the spatial and the temporal variability of POC export during austral spring (October–November 2011) in the Fe-fertilized area of the Kerguelen Plateau region. POC export fluxes were estimated at high productivity sites over and downstream of the plateau and compared to a high-nutrient low-chlorophyll (HNLC) area upstream of the plateau in order to assess the impact of iron-induced productivity on the vertical export of carbon. Deficits in 234Th activities were observed at all stations in surface waters, indicating early scavenging by particles in austral spring. 234Th export was lowest at the reference station R-2 and highest in the recirculation region (E stations) where a pseudo-Lagrangian survey was conducted. In comparison 234Th export over the central plateau and north of the polar front (PF) was relatively limited throughout the survey. However, the 234Th results support that Fe fertilization increased particle export in all iron-fertilized waters. The impact was greatest in the recirculation feature (3–4 fold at 200 m depth, relative to the reference station), but more moderate over the central Kerguelen Plateau and in the northern plume of the Kerguelen bloom (~2-fold at 200 m depth). The C : Th ratio of large ( μm) potentially sinking particles collected via sequential filtration using in situ pumping (ISP) systems was used to convert the 234Th flux into a POC export flux. The C : Th ratios of sinking particles were highly variable (3.1 ± 0.1 to 10.5 ± 0.2 μmol dpm−1) with no clear site-related trend, despite the variety of ecosystem responses in the fertilized regions. C : Th ratios showed a decreasing trend between 100 and 200 m depth suggesting preferential carbon loss relative to 234Th possibly due to heterotrophic degradation and/or grazing activity. C : Th ratios of sinking particles s led with drifting sediment traps in most cases showed very good agreement with ratios for particles collected via ISP deployments ( μm particles). Carbon export production varied between 3.5 ± 0.9 and 11.8 ± 1.3 mmol m−2 d−1 from the upper 100 m and between 1.8 ± 0.9 and 8.2 ± 0.9 mmol m−2 d−1 from the upper 200 m. The highest export production was found inside the PF meander with a range of 5.3 ± 1.0 to 11.8 ± 1.1 mmol m−2 d−1 over the 19-day survey period. The impact of Fe fertilization is highest inside the PF meander with 2.9–4.5-fold higher carbon flux at 200 m depth in comparison to the HNLC control station. The impact of Fe fertilization was significantly less over the central plateau (stations A3 and E-4W) and in the northern branch of the bloom (station F-L) with 1.6–2.0-fold higher carbon flux compared to the reference station R. Export efficiencies (ratio of export to primary production and ratio of export to new production) were particularly variable with relatively high values in the recirculation feature (6 to 27 %, respectively) and low values (1 to 5 %, respectively) over the central plateau (station A3) and north of the PF (station F-L), indicating spring biomass accumulation. Comparison with KEOPS1 results indicated that carbon export production is much lower during the onset of the bloom in austral spring than during the peak and declining phases in late summer.
Publisher: Wiley
Date: 13-05-2010
Publisher: Copernicus GmbH
Date: 18-09-2014
DOI: 10.5194/BGD-11-13389-2014
Abstract: Abstract. The KEOPS2 project aims to elucidate the role of natural Fe fertilisation on biogeochemical cycles and ecosystem functioning, including quantifying the sources and processes by which iron is delivered in the vicinity of the Kerguelen Archipelago, Southern Ocean. The KEOPS2 process study used an upstream HNLC, deep water (2500 m), reference station to compare with a shallow (500 m), strongly fertilised plateau station and continued the observations to a downstream, bathymetrically trapped recirculation of the Polar Front where eddies commonly form and persist for hundreds of kilometres into the Southern Ocean. Over the Kerguelen Plateau, mean particulate (1–53 μm) Fe and Al concentrations (pFe = 13.4 nM, pAl = 25.2 nM) were more than 20-fold higher than at an offshore (lower-productivity) reference station (pFe = 0.53 nM, pAl = 0.83 nM). In comparison, over the plateau dissolved Fe levels were only elevated by a factor of ∼2. Over the Kerguelen Plateau, ratios of pMn Al and pFe Al resemble basalt, likely originating from glacial/fluvial inputs into shallow coastal waters. In downstream, offshore deep-waters, higher pFe Al, and pMn Al ratios were observed, suggesting loss of lithogenic material accompanied by retention of pFe and pMn. Biological uptake of dissolved Fe and Mn and conversion into the biogenic particulate fraction or aggregation of particulate metals onto bioaggregates also increased these ratios further in surface waters as the bloom developed within the recirculation structure. While resuspension of shelf sediments is likely to be one of the important mechanisms of Fe fertilisation over the plateau, fluvial and glacial sources appear to be important to areas downstream of the island. Vertical profiles within an offshore recirculation feature associated with the Polar Front show pFe and pMn levels that were 6-fold and 3.5-fold lower respectively than over the plateau in surface waters, though still 3.6-fold and 1.7-fold higher respectively than the reference station. Within the recirculation feature, strong depletions of pFe and pMn were observed in the remnant winter water (temperature-minimum) layer near 175 m, with higher values above and below this depth. The correspondence between the pFe minima and the winter water temperature minima implies a seasonal cycle is involved in the supply of pFe into the fertilized region. This observed association is indicative of reduced supply in winter, which is counterintuitive if sediment resuspension and entrainment within the mixed layer is the primary fertilising mechanism to the downstream recirculation structure. Therefore, we hypothesise that lateral transport of pFe from shallow coastal waters is strong in spring, associated with snow melt and increased runoff due to rainfall, drawdown through summer and reduced supply in winter when snowfall and freezing conditions predominate in the Kerguelen region.
Publisher: Wiley
Date: 24-10-2022
Publisher: University of California Press
Date: 2016
DOI: 10.12952/JOURNAL.ELEMENTA.000130
Abstract: The discovery that melting sea ice can fertilize iron (Fe)-depleted polar waters has recently fostered trace metal research efforts in sea ice. The aim of this review is to summarize and synthesize the current understanding of Fe biogeochemistry in sea ice. To do so, we compiled available data on particulate, dissolved, and total dissolvable Fe (PFe, DFe and TDFe, respectively) from sea-ice studies from both polar regions and from sub-Arctic and northern Hemisphere temperate areas. Data analysis focused on a circum-Antarctic Fe dataset derived from 61 ice cores collected during 10 field expeditions carried out between 1997 and 2012 in the Southern Ocean. Our key findings are that 1) concentrations of all forms of Fe (PFe, DFe, TDFe) are at least a magnitude larger in fast ice and pack ice than in typical Antarctic surface waters 2) DFe, PFe and TDFe behave differently when plotted against sea-ice salinity, suggesting that their distributions in sea ice are driven by distinct, spatially and temporally decoupled processes 3) DFe is actively extracted from seawater into growing sea ice 4) fast ice generally has more Fe-bearing particles, a finding supported by the significant negative correlation observed between both PFe and TDFe concentrations in sea ice and water depth 5) the Fe pool in sea ice is coupled to biota, as indicated by the positive correlations of PFe and TDFe with chlorophyll a and particulate organic carbon and 6) the vast majority of DFe appears to be adsorbed onto something in sea ice. This review also addresses the role of sea ice as a reservoir of Fe and its role in seeding seasonally ice-covered waters. We discuss the pivotal role of organic ligands in controlling DFe concentrations in sea ice and highlight the uncertainties that remain regarding the mechanisms of Fe incorporation in sea ice.
Publisher: Elsevier BV
Date: 08-2010
DOI: 10.1016/J.ACA.2010.07.037
Abstract: Trace elements often limit phytoplankton growth in the ocean, and the quantification of particulate forms is essential to fully understand their biogeochemical cycling. There is presently a lack of reliable measurements on the trace elemental content of marine particles, in part due to the inadequacies of the s ling and analytical methods employed. Here we report on the development of a series of state-of-the-art trace metal clean methods to collect and process oceanic particulate material in open-ocean and sea ice environments, including s ling, size-fractionated filtration, particle digestions and analysis by magnetic sector inductively coupled plasma-mass spectrometry (ICP-MS). Particular attention was paid to the analysis of certified reference materials (CRMs) and field blanks, which are typically the limiting factor for the accurate analysis of low concentrations of trace metals in marine particulate s les. Theoretical detection limits (3 s of the blank) were low for all 17 elements considered, and varied according to filter material and porosity (sub-microg L(-1) for polycarbonate filters and 1-2 microg L(-1) for quartz and polyester filters). Analytical accuracy was verified using fresh water CRMs, with excellent recoveries noted (93-103%). Digestion efficiencies for various acid combinations were assessed using sediment and plankton CRMs. Using nitric acid only, good recoveries (79-90%) were achieved for Mo, Cd, Ba, Pb, Mn, Fe, Co, Ni, Cu, Zn and Ga. The addition of HF was necessary for the quantitative recovery of the more refractory trace elements such as U, Al, V and Cr. Bioactive elements such as P can also be analysed and used as a biomass normaliser. Our developed s ling and analytical methods proved reliable when applied during two major field programs in both the open Southern Ocean and Antarctic sea ice environments during the International Polar Year in 2007. Trace elemental data are presented for particulate s les collected in both suspended and sinking marine material, and also within sea ice cores.
Publisher: American Geophysical Union (AGU)
Date: 06-08-2011
DOI: 10.1029/2010JG001628
Publisher: American Geophysical Union (AGU)
Date: 11-2018
DOI: 10.1029/2018JC014245
Publisher: Wiley
Date: 27-10-2022
Publisher: Wiley
Date: 08-2019
DOI: 10.1002/LOM3.10327
Publisher: Copernicus GmbH
Date: 25-06-2015
Abstract: Abstract. Dissolved Fe (dFe) concentrations were measured in the upper 1300 m of the water column in the vicinity of the Kerguelen Islands as part of the second KErguelen Ocean Plateau compared Study (KEOPS2). Concentrations ranged from 0.06 nmol L−1 in offshore, Southern Ocean waters to 3.82 nmol L−1 within Hillsborough Bay, on the north-eastern coast of the Kerguelen Islands. Direct island runoff, glacial melting and resuspended sediments were identified as important inputs of dFe that could potentially fertilise the northern part of the plateau. A significant deep dFe enrichment was observed over the plateau with dFe concentrations increasing up to 1.30 nmol L−1 close to the seafloor, probably due to sediment resuspension and pore water release. Biological uptake was shown to induce a significant decrease in dFe concentrations between two visits (28 days apart) at a station above the plateau. Our work also considered other processes and sources, such as lateral advection of enriched seawater, remineralisation processes, and the influence of the polar front (PF) as a vector for Fe transport. Overall, heterogeneous sources of Fe over and off the Kerguelen Plateau, in addition to strong variability in Fe supply by vertical or horizontal transport, may explain the high variability in dFe concentrations observed during this study.
Publisher: American Geophysical Union (AGU)
Date: 25-09-2020
DOI: 10.1029/2020JC016286
Publisher: Elsevier BV
Date: 08-2009
Publisher: Elsevier BV
Date: 04-2019
Publisher: Elsevier BV
Date: 11-2016
Publisher: Elsevier BV
Date: 05-2011
Publisher: Wiley
Date: 28-08-2021
DOI: 10.1002/LNO.11923
Abstract: As marine microorganisms and environmental conditions coevolved over geological timescales, metals have been incorporated into all essential metabolic processes. In the modern ocean, metals are present from trace amounts limiting microbial growth to toxic concentrations. Dissolved trace metals are a major bioavailable reservoir. However, the acquisition of metals from marine particles remains largely unexplored. Here, we combined chemical characterization and a comparative metatranscriptomics approach to investigate the availability of nine metals of biological importance on particles collected in the region of Heard Island (Indian sector of the Southern Ocean). Elemental ratios identified particulate matter as a potential source of metals for prokaryotes. The expression of genes for the uptake of metals through various mechanisms demonstrated that particles are a bioavailable reservoir. But genes involved in the control of resistance to metal toxicity, storage, sensing, and regulation were also highly expressed. Our observations suggest that homeostasis associated with a erse prokaryotic community is the overarching mechanism that enhances the trace element processing on particles. These results provide clues that microbial activity on particles is critical in the redistribution of trace elements between different fractions and chemical forms in the ocean.
Publisher: Elsevier BV
Date: 05-2011
Publisher: American Geophysical Union (AGU)
Date: 06-2023
DOI: 10.1029/2022RG000770
Abstract: Antarctic landfast sea ice (fast ice) is stationary sea ice that is attached to the coast, grounded icebergs, ice shelves, or other protrusions on the continental shelf. Fast ice forms in narrow (generally up to 200 km wide) bands, and ranges in thickness from centimeters to tens of meters. In most regions, it forms in autumn, persists through the winter and melts in spring/summer, but can remain throughout the summer in particular locations, becoming multi‐year ice. Despite its relatively limited extent (comprising between about 4% and 13% of overall sea ice), its presence, variability and seasonality are drivers of a wide range of physical, biological and biogeochemical processes, with both local and far‐ranging ramifications for the Earth system. Antarctic fast ice has, until quite recently, been overlooked in studies, likely due to insufficient knowledge of its distribution, leading to its reputation as a “missing piece of the Antarctic puzzle.” This review presents a synthesis of current knowledge of the physical, biogeochemical and biological aspects of fast ice, based on the sub‐domains of: fast ice growth, properties and seasonality remote‐sensing and distribution interactions with the atmosphere and the ocean biogeochemical interactions its role in primary production and fast ice as a habitat for grazers. Finally, we consider the potential state of Antarctic fast ice at the end of the 21st Century, underpinned by Coupled Model Intercomparison Project model projections. This review also gives recommendations for targeted future work to increase our understanding of this critically‐important element of the global cryosphere.
Location: Australia
Location: Australia
No related grants have been discovered for Pier van der Merwe.