ORCID Profile
0000-0002-5144-7799
Current Organisation
University College London
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Oceanography | Analytical Chemistry | Chemical Oceanography | Environmental Chemistry (incl. Atmospheric Chemistry) | Chemical Oceanography | Biological Oceanography | Climate Change Processes | Separation Science | Analytical chemistry | Biochemistry And Cell Biology Not Elsewhere Classified | Separation Science | Analytical Spectrometry | Atmospheric Aerosols | Physical Oceanography | Other Chemical Sciences | Biological oceanography | Chemical oceanography | Bacteriology | Analytical spectrometry | Instrumental methods (excl. immunological and bioassay methods) | Analytical Spectrometry | Separation science | Oceanography | Biological Oceanography | Glaciology | Analytical Chemistry Not Elsewhere Classified | Gene Expression | Environmental Chemistry (Incl. Atmospheric Chemistry) | Analytical Biochemistry
ANZSRC Socio-Economic Objective (SEO)
Physical and Chemical Conditions of Water in Marine Environments | Expanding Knowledge in the Earth Sciences | Chemical sciences | Physical and chemical conditions | Effects of Climate Change and Variability on Antarctic and Sub-Antarctic Environments (excl. Social Impacts) | Living resources (flora and fauna) | Atmospheric Processes and Dynamics | Aquaculture Rock Lobster | Atmospheric Composition (incl. Greenhouse Gas Inventory) | Biological sciences | Climate change | Living resources (incl. impacts of fishing on non-target species) | Horticultural Crops not elsewhere classified | Oceanic processes (excl. climate related) | Other | Marine Air Quality | Antarctic and Sub-Antarctic Air Quality | Scientific instrumentation | Water Services and Utilities | Climate and Climate Change not elsewhere classified | Expanding Knowledge in the Environmental Sciences |
Related Links
Publications
Distribution of dissolved and particulate metals in Antarctic sea ice
Publisher: Elsevier BV
Date: 03-2011
Evaluation of aerosol iron solubility over Australian coastal regions based on inverse modeling: implications of bushfires on bioaccessible iron concentrations in the Southern Hemisphere
Publisher: Springer Science and Business Media LLC
Date: 26-08-2020
DOI: 10.1186/S40645-020-00357-9
Abstract: Mineral dust is the major source of external micro-nutrients such as iron (Fe) to the open ocean. However, large uncertainties in model estimates of Fe emissions and aerosol-bearing Fe solubility (i.e., the ratio of labile Fe (L Fe ) to total Fe (T Fe )) in the Southern Hemisphere (SH) h ered accurate estimates of atmospheric delivery of bioavailable Fe to the Southern Ocean. This study applied an inverse modeling technique to a global aerosol chemistry transport model (IMPACT) in order to optimize predictions of mineral aerosol Fe concentrations based on recent observational data over Australian coastal regions (110°E–160°E and 10°S–41°S). The optimized (a posteriori) model did not only better capture aerosol T Fe concentrations downwind from Australian dust outbreak but also successfully reproduced enhanced Fe solubility (7.8 ± 8.4%) and resulted in much better agreement of L Fe concentrations with the field measurements (1.4 ± 1.5 vs. 1.4 ± 2.3 ng Fe m –3 ). The a posteriori model estimates suggested that bushfires contributed a large fraction of L Fe concentrations in aerosols, although substantial contribution from missing sources (e.g., coal mining activities, volcanic eruption, and secondary formation) was still inferred. These findings may have important implications for the projection of future micro-nutrient supply to the oceans as increasing frequency and intensity of open biomass burning are projected in the SH.
Effect of dissolved iron (II) and temperature on growth of the Southern Ocean phytoplankton species Fragilariopsis cylindrus and Phaeocystis antarctica
Publisher: Springer Science and Business Media LLC
Date: 24-09-2023
The role of bacterial and algal exopolymeric substances in iron chemistry
Publisher: Elsevier BV
Date: 07-2015
Seasonality of phytoplankton growth limitation by iron and manganese in subantarctic waters
Publisher: Wiley
Date: 06-2022
Zinc requirement for two phytoplankton strains of the Tasman Sea
Publisher: CSIRO Publishing
Date: 2017
DOI: 10.1071/MF15323
Abstract: Zinc has been proposed as a limiting, or co-limiting, micronutrient for phytoplankton. In the Tasman Sea, extremely low zinc concentrations have been reported, raising the possibility there of limitation of phytoplankton growth by zinc. The pennate diatom Nitzschia closterium (CS-1) and the coccolithophorid Emiliania huxleyi (CS-812) were cultured in two low zinc concentrations (Zn2+ = 1.5 pmolL–1 and Zn2+ = 1.5 nmolL–1) mimicking conditions found in coastal and pelagic Tasman Sea. To monitor phytoplankton health and productivity, the maximum quantum yield (Fv/Fm), growth rate and cell size were analysed. These parameters showed that both strains were able to adapt and still grow. Short-term uptake experiments revealed an effect on Zn biological transport, with consequences for its bioavailability. When grown at low Zn2+ concentrations, E. huxleyi showed an induction of a two-transporter system, highly dependent on photosynthetic energy for Zn uptake. N. closterium was able to survive without inducing a higher-affinity Zn transporter. Its Zn uptake was also highly dependent on cellular energy and the ability to potentially access labile complexed forms of Zn. This strategy, thus, represented an advantage over E. huxleyi. Results are discussed in the context of the conditions found in the Tasman Sea.
The likelihood of observing dust-stimulated phytoplankton growth in waters proximal to the Australian continent
Publisher: Elsevier BV
Date: 05-2013
Dissolved iron in the North Atlantic Ocean and Labrador Sea along the GEOVIDE section (GEOTRACES section GA01)
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.
Supplementary material to "Dry season aerosol iron solubility in tropical northern Australia"
Publisher: Copernicus GmbH
Date: 17-06-2016
Glacial and hydrothermal sources of dissolved iron(II) in Southern Ocean waters surrounding Heard and McDonald Islands
Publisher: Wiley
Date: 27-04-2020
Supplementary material to "Dissolved iron in the North Atlantic Ocean and Labrador Sea along the GEOVIDE section (GEOTRACES section GA01)"
Publisher: Copernicus GmbH
Date: 04-04-2018
Primary productivity induced by iron and nitrogen in the Tasman Sea: An overview of the PINTS expedition
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.
Zinc cycling in the Tasman Sea: Distribution, speciation and relation to phytoplankton community
Publisher: Elsevier BV
Date: 05-2016
The influence of iron and light on net community production in the Subantarctic and Polar Frontal Zones
Publisher: Copernicus GmbH
Date: 02-2011
Abstract: Abstract. The roles of iron and light in controlling biomass and primary productivity are clearly established in the Southern Ocean. However, their influence on net community production (NCP) and carbon export remains to be quantified. To improve our understanding of NCP and carbon export production in the Subantarctic Zone (SAZ) and the northern reaches of the Polar Frontal Zone (PFZ), we conducted continuous onboard determinations of NCP as part of the Sub-Antarctic Sensitivity to Environmental Change (SAZ-Sense) study, which occurred in January–February 2007. Biological O2 supersaturation was derived from measuring O2/Ar ratios by equilibrator inlet mass spectrometry. Based on these continuous measurements, NCP during the austral summer 2007 in the Australian SAZ was approximately 43 mmol O2 m−2 d−1. NCP showed significant spatial variability, with larger values near the Subtropical front, and a general southward decrease. For shallower mixed layers ( m), dissolved Fe concentrations and Fe sufficiency, estimated from variable fluorescence, correlated strongly with NCP. The strong correlation between NCP and dissolved Fe may be difficult to interpret because of the correlation of dissolved Fe to MLD and because the concentration of iron may not be a good indicator of its availability. At stations with deeper mixed layers, NCP was consistently low, regardless of iron sufficiency, consistent with light availability also being an important control of NCP. Our new observations provide independent evidence for the critical roles of iron and light in mediating carbon export from the Southern Ocean mixed layer.
Electrochemical evaluation of iron-binding ligands along the Australian GEOTRACES southwestern Pacific section (GP13)
Publisher: Elsevier BV
Date: 02-2020
Sustained Upwelling of Subsurface Iron Supplies Seasonally Persistent Phytoplankton Blooms Around the Southern Kerguelen Plateau, Southern Ocean
Publisher: American Geophysical Union (AGU)
Date: 08-2018
DOI: 10.1029/2018JC013932
Determination of aluminium in natural water samples
Publisher: Elsevier BV
Date: 04-2007
DOI: 10.1016/J.ACA.2007.02.048
Abstract: The atmospheric deposition of terrestrial dust into the ocean is an important factor in controlling Earth's climate. Aluminium can be used as a tracer for the magnitude and location of dust transported from the land to surface ocean. The element is ideal for this purpose since its primary input is via aeolian dust deposition and it has a short surface water residence time. The accurate determination of dissolved aluminium in seawater is difficult due to the complexity of the matrix and the trace (nanomolar) concentrations at which the metal exists. This paper presents a critical review of the different s ling and analytical methods for the determination of the concentration of aluminium in natural waters, with particular focus on techniques successfully applied to shipboard analysis of seawater.
Mercury in the Southern Ocean
Publisher: Elsevier BV
Date: 07-2011
Reversed phase high performance liquid chromatographic determination of dissolved aluminium in open ocean seawater
Publisher: Wiley
Date: 11-2012
High lability Fe particles sourced from glacial erosion can meet previously unaccounted biological demand: Heard Island, Southern Ocean
Publisher: Frontiers Media SA
Date: 14-06-2019
Atmospheric Trace Metal Deposition from Natural and Anthropogenic Sources in Western Australia
Publisher: MDPI AG
Date: 07-05-2020
Abstract: Aerosols from Western Australia supply micronutrient trace elements including Fe into the western shelf of Australia and further afield into the Southern and Indian Oceans. However, regional observations of atmospheric trace metal deposition are limited. Here, we applied a series of leaching experiments followed by total analysis of bulk aerosol s les to a unique time-series of aerosol s les collected in Western Australia to determine atmospheric concentrations and solubilities of Fe and V, Mn, Co, Zn, and Pb. Positive matrix factorisation analysis indicated that mineral dust, biomass burning particulates, sea salt, and industrial emissions were the major types of aerosols. Overall, natural sources dominated Fe deposition. Higher atmospheric concentrations of mineral dust (sixfold) and biomass burning emissions were observed in warmer compared to cooler months. The fraction of labile Fe (0.6–6.0%) was lower than that reported for other regions of Australia. Bushfire emissions are a temporary source of labile Fe and may cause a peak in the delivery of its more easily available forms to the ocean. Increased labile Fe deposition may result in higher ocean productivity in regions where Fe is limiting, and the effect of aerosol deposition on ocean productivity in this region requires further study.
Pelagic Iron Recycling in the Southern Ocean: Exploring the Contribution of Marine Animals
Publisher: Frontiers Media SA
Date: 29-03-2018
Preliminary investigation into the stimulation of phytoplankton photophysiology and growth by whale faeces
Publisher: Elsevier BV
Date: 08-2013
Sourcing the iron in the naturally fertilised bloom around the Kerguelen Plateau: Particulate trace metal dynamics
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.
Dissolved iron in the North Atlantic Ocean and Labrador Sea along the GEOVIDE section (GEOTRACES section GA01)
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.
Critical evaluation of a seaFAST system for the analysis of trace metals in marine samples
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
Atmospheric Trace Metal Deposition near the Great Barrier Reef, Australia
Publisher: MDPI AG
Date: 15-04-2020
Abstract: Aerosols deposited into the Great Barrier Reef (GBR) contain iron (Fe) and other trace metals, which may act as micronutrients or as toxins to this sensitive marine ecosystem. In this paper, we quantified the atmospheric deposition of Fe and investigated aerosol sources in Mission Beach (Queensland) next to the GBR. Leaching experiments were applied to distinguish pools of Fe with regard to its solubility. The labile Fe concentration in aerosols was 2.3–10.6 ng m−3, which is equivalent to 4.9%–11.4% of total Fe and was linked to combustion and biomass burning processes, while total Fe was dominated by crustal sources. A one-day precipitation event provided more soluble iron than the average dry deposition flux, 0.165 and 0.143 μmol m−2 day−1, respectively. Scanning Electron Microscopy indicated that alumina-silicates were the main carriers of total Fe and s les affected by combustion emissions were accompanied by regular round-shaped carbonaceous particulates. Collected aerosols contained significant amounts of Cd, Co, Cu, Mo, Mn, Pb, V, and Zn, which were mostly (47.5%–96.7%) in the labile form. In this study, we provide the first field data on the atmospheric delivery of Fe and other trace metals to the GBR and propose that this is an important delivery mechanism to this region.
Trace elements and nutrients in wildfire plumes to the southeast of Australia
Publisher: Elsevier BV
Date: 06-2022
Iron budgets for three distinct biogeochemical sites around the Kerguelen Archipelago (Southern Ocean) during the natural fertilisation study, KEOPS-2
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.
Lithogenic Particle Flux to the Subantarctic Southern Ocean: A Multi‐Tracer Estimate Using Sediment Trap Samples
Publisher: American Geophysical Union (AGU)
Date: 09-2022
DOI: 10.1029/2022GB007391
Abstract: Mineral dust is a key source of essential micronutrients, particularly iron (Fe), for phytoplankton in the Southern Ocean. However, observations of dust deposition over the Southern Ocean are sparse, hindering assessments of its influence on marine biogeochemistry. We present a time series (2010–2019) of lithogenic particle flux estimates using sediment trap s les collected at 1,000 m depth at the subantarctic Southern Ocean Time Series (SOTS) site. Lithogenic flux was estimated using in idual Fe, aluminium (Al), titanium, and thorium concentrations in sediment trap particles less than 1 mm in size. These tracers showed good agreement with one another, and their average was investigated as a proxy for mineral dust deposition. This multi‐tracer average lithogenic flux exhibited strong seasonality, peaking in late spring and summer. No significant Fe enrichment was observed compared to the average upper continental crust, indicating that lithogenic material dominates particulate Fe flux at SOTS. Similar Fe:Al ratios in our s les compared to those reported in marine aerosols off southern Australia, coupled with particle trajectory analysis, suggested Australian dust constitutes the primary lithogenic source to SOTS sinking particles. Lead enrichment in our s les also highlighted an anthropogenic contribution to sinking particles, which might represent an additional aeolian source of more bio‐available Fe to subantarctic waters. This study contributes a new long‐term estimate of lithogenic particle fluxes and aeolian deposition over the subantarctic Southern Ocean. These estimates may enhance model representation of trace metal contribution to biogeochemical processes in the Southern Ocean.
Constraining the Contribution of Hydrothermal Iron to Southern Ocean Export Production Using Deep Ocean Iron Observations
Publisher: Frontiers Media SA
Date: 10-03-2022
DOI: 10.3389/FMARS.2022.754517
Abstract: Hydrothermal iron supply contributes to the Southern Ocean carbon cycle via the regulation of regional export production. However, as hydrothermal iron input estimates are coupled to helium, which are uncertain depending on whether helium inputs are based on ridge spreading rates or inverse modelling, questions remain regarding the magnitude of the export production impacts. A particular challenge is the limited observations of dissolved iron (dFe) supply from the abyssal Southern Ocean ridge system to directly assess different hydrothermal iron supply scenarios. We combine ocean biogeochemical modelling with new observations of dFe from the abyssal Southern Ocean to assess the impact of hydrothermal iron supply estimated from either ridge spreading rate or inverse helium modelling on Southern Ocean export production. The hydrothermal contribution to dFe in the upper 250 m reduces 4–5 fold when supply is based on inverse modelling, relative to those based on spreading rate, translating into a 36–73% reduction in the impact of hydrothermal iron on export production. However, only the spreading rate input scheme reproduces observed dFe anomalies & nM around the circum-Antarctic ridge. The model correlation with observations drops 3 fold under the inverse modelling input scheme. The best dFe scenario has a residence time for hydrothermal iron that is between 21 and 34 years, highlighting the importance of rapid physical mixing to surface waters. Overall, because of its short residence time, hydrothermal Fe supplied locally by circum-Antarctic ridges is most important to the Southern Ocean carbon cycle and our results highlight decoupling between hydrothermal iron and helium supply.
Carbon export in the naturally iron-fertilized Kerguelen area of the Southern Ocean based on the234Th approach
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.
Southern Ocean iron fertilization by baleen whales and Antarctic krill
Publisher: Wiley
Date: 13-05-2010
Sourcing the iron in the naturally-fertilised bloom around the Kerguelen Plateau: particulate trace metal dynamics
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.
Enhanced Deposition of Atmospheric Soluble Iron by Intrusions of Marine Air Masses to East Antarctica
Publisher: American Geophysical Union (AGU)
Date: 11-07-2022
DOI: 10.1029/2022JD036586
Abstract: Bio‐essential iron can relieve nutrient limitation and stimulate marine productivity in the Southern Ocean. The fractional iron solubility of aerosol iron is an important variable determining iron availability for biological uptake. However, estimates of dissolved iron (dFe iron 0.2 μm) and the factors driving the variability of fractional iron solubility in pristine air masses are largely unquantified. To constrain inputs of fractional iron solubility to remote East Antarctic waters, dFe, total dissolvable iron (TDFe), trace elements and refractory black carbon were analyzed in a 9‐year‐old snow pit (2005–2014) from a new ice core site at Aurora Basin North (ABN) in Wilkes Land, East Antarctica. Extremely low annual dFe deposition fluxes were estimated (0.2 × 10 −6 g m −2 y −1 ), while annual TDFe deposition fluxes (70 × 10 −6 g m −2 y −1 ) were comparable to other Antarctic sites. TDFe is dominantly sourced from mineral dust. Unlike coastal Antarctic sites where the variability of fractional iron solubility in modern snow is explained by a mixture of dust and biomass burning sources, dFe deposition and fractional iron solubility at ABN (ranging between 0.1% and 6%) is enhanced in episodic high precipitation events from synoptic warm air masses. Enhanced fractional iron solubility reaching the high elevation site at ABN is suggested through the mechanism of cloud processing of background mineral dust that modifies the dust chemistry and increases iron dissolution during long‐range transport. This study highlights a complex interplay of sources and processes that drive fractional iron solubility in pristine air masses.
The GESAMP atmospheric iron deposition model intercomparison study
Publisher: Copernicus GmbH
Date: 09-11-2018
Abstract: Abstract. This work reports on the current status of the global modeling of iron (Fe) deposition fluxes and atmospheric concentrations and the analyses of the differences between models, as well as between models and observations. A total of four global 3-D chemistry transport (CTMs) and general circulation (GCMs) models participated in this intercomparison, in the framework of the United Nations Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP) Working Group 38, “The Atmospheric Input of Chemicals to the Ocean”. The global total Fe (TFe) emission strength in the models is equal to ∼72 Tg Fe yr−1 (38–134 Tg Fe yr−1) from mineral dust sources and around 2.1 Tg Fe yr−1 (1.8–2.7 Tg Fe yr−1) from combustion processes (the sum of anthropogenic combustion/biomass burning and wildfires). The mean global labile Fe (LFe) source strength in the models, considering both the primary emissions and the atmospheric processing, is calculated to be 0.7 (±0.3) Tg Fe yr−1, accounting for both mineral dust and combustion aerosols. The mean global deposition fluxes into the global ocean are estimated to be in the range of 10–30 and 0.2–0.4 Tg Fe yr−1 for TFe and LFe, respectively, which roughly corresponds to a respective 15 and 0.3 Tg Fe yr−1 for the multi-model ensemble model mean. The model intercomparison analysis indicates that the representation of the atmospheric Fe cycle varies among models, in terms of both the magnitude of natural and combustion Fe emissions as well as the complexity of atmospheric processing parameterizations of Fe-containing aerosols. The model comparison with aerosol Fe observations over oceanic regions indicates that most models overestimate surface level TFe mass concentrations near dust source regions and tend to underestimate the low concentrations observed in remote ocean regions. All models are able to simulate the tendency of higher Fe concentrations near and downwind from the dust source regions, with the mean normalized bias for the Northern Hemisphere (∼14), larger than that of the Southern Hemisphere (∼2.4) for the ensemble model mean. This model intercomparison and model–observation comparison study reveals two critical issues in LFe simulations that require further exploration: (1) the Fe-containing aerosol size distribution and (2) the relative contribution of dust and combustion sources of Fe to labile Fe in atmospheric aerosols over the remote oceanic regions.
The interplay between regeneration and scavenging fluxes drives ocean iron cycling
Publisher: Springer Science and Business Media LLC
Date: 31-10-2019
DOI: 10.1038/S41467-019-12775-5
Abstract: Despite recent advances in observational data coverage, quantitative constraints on how different physical and biogeochemical processes shape dissolved iron distributions remain elusive, lowering confidence in future projections for iron-limited regions. Here we show that dissolved iron is cycled rapidly in Pacific mode and intermediate water and accumulates at a rate controlled by the strongly opposing fluxes of regeneration and scavenging. Combining new data sets within a watermass framework shows that the multidecadal dissolved iron accumulation is much lower than expected from a meta-analysis of iron regeneration fluxes. This mismatch can only be reconciled by invoking significant rates of iron removal to balance iron regeneration, which imply generation of authigenic particulate iron pools. Consequently, rapid internal cycling of iron, rather than its physical transport, is the main control on observed iron stocks within intermediate waters globally and upper ocean iron limitation will be strongly sensitive to subtle changes to the internal cycling balance.
Modern sampling and analytical methods for the determination of trace elements in marine particulate material using magnetic sector inductively coupled plasma-mass spectrometry
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.
Pyrogenic iron: The missing link to high iron solubility in aerosols
Publisher: American Association for the Advancement of Science (AAAS)
Date: 03-05-2019
Abstract: Air pollution creates high Fe solubility in pyrogenic aerosols, raising the flux of biologically essential Fe to the oceans.
Distributions of dissolved and particulate iron in the sub-Antarctic and Polar Frontal Southern Ocean (Australian sector)
Publisher: Elsevier BV
Date: 11-2011
Dust and pyrogenic iron boost phytoplankton blooms in sub-Antarctic waters of the Tasman Sea
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-7809
Abstract: & & Although it is commonly accepted that atmospheric deposition of Fe particles can fertilise phytoplankton, there is yet no clear evidence on how such a fertilisation effect takes place. Several studies have attempted to link in idual dust events with surface chlorophyll responses but generally, they do not find a clear correspondence between dust deposition and its impact on chlorophyll. In this work, we use a biogeochemical model to show that the atmospheric deposition of Fe in high-latitude seas, rather than creating instantaneous phytoplankton responses, replenish the upper mixed layer of the ocean during the pre-bloom period, from winter to early summer. The Fe accumulated at the surface boosts the phytoplankton bloom of the following summer, resulting in surface chlorophyll accumulations of up to 3 times larger than the years without atmospheric deposition. We used this mechanism to explain the strong inter-annual variability of the phytoplankton bloom in sub-Antarctic iron-limited waters east of Australia. Putting together more than a 15-years-long record of ocean colour observations and atmospheric aerosols reanalysis we uncovered a strong correlation (r& sup& & /sup& & .6) between the dust that crossed the region during the pre-bloom period and the magnitude of the surface chlorophyll bloom. Interestingly, the correlation increased when taking into account pyrogenic aerosols in addition to dust. Our study presents the first observational link between Climate Change-enhanced droughts and wildfires, atmospheric aerosols and primary production of iron-limited waters.& &
High temporal resolution observations of spring fast ice melt and seawater iron enrichment in East Antarctica
Publisher: American Geophysical Union (AGU)
Date: 06-08-2011
DOI: 10.1029/2010JG001628
Antarctic slush-ice algal accumulation not quantified through conventional satellite imagery: beware the ice of March
Publisher: Copernicus GmbH
Date: 11-11-2015
Abstract: Abstract. Our current knowledge of broad-scale patterns of primary production in the Southern Ocean is derived from satellite ocean-colour estimates of chlorophyll a (Chl a) in the open ocean, typically in spring-summer. Here, we provide evidence that large-scale intra-ice phytoplankton surface aggregation occur off the coast of Antarctica during austral autumn, and that these "blooms" are largely undetected in satellite ocean-colour time series (which mask the ice-covered ocean). We present an analysis of (i) true-colour (visible) satellite imagery in combination with (ii) conventional ocean-colour data, and (iii) direct s ling from a research vessel, to identify and characterise a large-scale intra-ice algal occurrence off the coast of East Antarctica in early autumn (March) 2012. We also present evidence of these autumn "blooms" in other regions (for ex le, Princess Astrid Coast in 2012) and other years (for ex le, Terra Nova Bay in 2015) implying regular and widespread occurrence of these phenomena. The occurrence of such undetected algal accumulations implies that the magnitude of primary production in the Southern Ocean is currently underestimated.
The Biogeochemical Role of Baleen Whales and Krill in Southern Ocean Nutrient Cycling
Publisher: Public Library of Science (PLoS)
Date: 03-12-2014
Biological uptake, water mass mixing and scavenging prevent transport of manganese-rich waters from the Antarctic shelf
Publisher: Wiley
Date: 27-10-2022
Southern Ocean Phytoplankton Stimulated by Wildfire Emissions and Sustained by Iron Recycling
Publisher: American Geophysical Union (AGU)
Date: 03-06-2202
DOI: 10.1029/2021GL097538
Abstract: Large ash plumes emitted by the 2019–2020 Australian wildfires were associated with a widespread phytoplankton bloom in the iron‐limited Pacific sector of the Southern Ocean. In this study, we used satellite observations and aerosol reanalysis products to study the regional phytoplankton community response to wildfire emissions. The bloom was stimulated by pyrogenic iron fertilization and coincided with elevated cellular pigment concentrations, increased photochemical efficiency, and apparent community structural shifts. Physiological anomalies were consistent with previously observed phytoplankton responses to iron stress relief and persisted for up to 9 months. Supported by a regional iron budget, we conclude that the bloom was sustained by iron recycling and episodic inputs of pyrogenic and dust‐borne mineral iron. The continuous regeneration of iron was likely facilitated by the bloom's large size, mitigating edge dilution effects, as well as enhanced bioavailability of pyrogenic and mineral iron due to atmospheric and chemical processing during long‐range transport.
Nutrient Cycling: Are Antarctic Krill a Previously Overlooked Source in the Marine Iron Cycle?
Publisher: Elsevier BV
Date: 10-2016
DOI: 10.1016/J.CUB.2016.08.044
Abstract: Iron limits phytoplankton growth in large areas of the Southern Ocean. A new study shows that Antarctic krill play a crucial role in the recycling of iron in the iron-limited waters.
The autonomous clean environmental (ACE) sampler: A trace‐metal clean seawater sampler suitable for open‐ocean time‐series applications
Publisher: Wiley
Date: 08-2019
DOI: 10.1002/LOM3.10327
The Neodymium Isotope Fingerprint of Adélie Coast Bottom Water
Publisher: American Geophysical Union (AGU)
Date: 16-10-2018
DOI: 10.1029/2018GL080074
Abstract: Adélie Land Bottom Water (ALBW), a variety of Antarctic Bottom Water formed off the Adélie Land coast of East Antarctica, ventilates the abyssal layers of the Australian sector of the Southern Ocean as well as the eastern Indian and Pacific Oceans. We present the first dissolved neodymium (Nd) isotope and concentration measurements for ALBW. The summertime signature of ALBW is characterized by ε Nd = −8.9, distinct from Ross Sea Bottom Water, and similar to Weddell Sea Bottom Water. Adélie Land Shelf Water, the precursor water mass for wintertime ALBW, features the least radiogenic Nd fingerprint observed around Antarctica to date (ε Nd = −9.9). Local geology around Antarctica is important in setting the chemical signature of in idual varieties of Antarctic Bottom Water, evident from the shelf water signature, which should be considered in the absence of direct wintertime observations.
Modern preconcentration methods for the determination of selenium species in environmental water samples
Publisher: Elsevier BV
Date: 07-2004
High variability in dissolved iron concentrations in the vicinity of the Kerguelen Islands (Southern Ocean)
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.
Supplementary material to "Antarctic slush-ice algal accumulation not quantified through conventional satellite imagery: Beware the ice of March"
Publisher: Copernicus GmbH
Date: 11-11-2015
Glacial and Hydrothermal Sources of Dissolved Iron (II) in Southern Ocean Waters Surrounding Heard and McDonald Islands
Publisher: American Geophysical Union (AGU)
Date: 25-09-2020
DOI: 10.1029/2020JC016286
Iron availability influences nutrient drawdown in the Heard and McDonald Islands region, Southern Ocean
Publisher: Elsevier BV
Date: 04-2019
Origin, transport and deposition of aerosol iron to Australian coastal waters
Publisher: Elsevier BV
Date: 05-2020
Homeostasis drives intense microbial trace metal processing on marine particles
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.
Iron fractionation in pack and fast ice in East Antarctica: Temporal decoupling between the release of dissolved and particulate iron during spring melt
Publisher: Elsevier BV
Date: 05-2011
Atmospheric inputs of volcanic iron around Heard and McDonald Islands, Southern ocean
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1EA00054C
Abstract: Increased atmospheric Fe loading and solubility was attributed to emissions from Heard Island volcano (Kerguelen plateau), emphasizing the need for models to consider volcanoes as a source of aeolian Fe to remote oceanic regions.
Zinc marine biogeochemistry in seawater: a review
Publisher: CSIRO Publishing
Date: 2012
DOI: 10.1071/MF11286
Abstract: The interest in trace element biogeochemistry has arisen from the well demonstrated iron hypothesis that revealed the central role that iron exerts on oceanic primary and associated biogeochemical cycles. The essentiality of zinc for key biological enzymes, coupled with a nutrient-like vertical distribution with low dissolved concentrations in many marine surface waters, provided motivation to study zinc in marine systems. Laboratory studies have confirmed the importance of zinc to sustain phytoplankton growth and its influence on the composition of the phytoplankton community. However, mixed results were obtained in the field, which suggest a more subtle effect of zinc on oceanic phytoplankton growth than iron. As a consequence, consensus on its biological role, mechanisms at play or regional versus global relevance is currently lacking and highlights the need for new conceptual models of zinc in marine systems. The recent GEOTRACES program is generating new data approaches to discuss and understand further zinc behaviour in the ocean.
Detection, dispersal and biogeochemical contribution of hydrothermal iron in the ocean
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.
Widespread And Unprecedented Phytoplankton Blooms Triggered By 2019–2020 Australian Wildfires
Publisher: Copernicus GmbH
Date: 28-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-9414
Abstract: & & Droughts and climate-change-driven warming lead to more frequent and intense wildfires, arguably contributing to the severe 2019& #8211 Australian wildfires. The environmental and ecological impacts of the fires include loss of habitats and the emission of substantial amounts of atmospheric aerosols. Aerosol emissions from wildfires can lead to the atmospheric transport of macronutrients and bio-essential trace metals such as nitrogen and iron, respectively. Previous works suggested that the oceanic deposition of wildfire aerosols can relieve nutrient limitations and, consequently, enhance marine productivity, but direct observations are lacking. Here we use satellite and autonomous biogeochemical Argo float data to evaluate the effect of 2019& #8211 Australian wildfire aerosol deposition on phytoplankton productivity. We find widespread and long-lasting phytoplankton blooms in the Southern Ocean downwind of Australia. Aerosol s les originating from the Australian wildfires contained a high iron content, and atmospheric trajectories show that these aerosols were likely to be transported to the bloom regions, suggesting that the blooms resulted from the fertilization of the iron-limited waters of the Southern Ocean.& &
The origin of lithogenic sediment in the south-western Ross Sea and implications for iron fertilization
Publisher: Cambridge University Press (CUP)
Date: 26-02-2016
DOI: 10.1017/S095410201600002X
Abstract: Summer iron (Fe) fertilization in the Ross Sea has previously been observed in association with diatom productivity, lithogenic particles and excess Fe in the water column. This productivity event occurred during an early breakout of sea ice via katabatic winds, suggesting that aeolian dust could be an important source of lithogenic Fe required for diatom growth in the Ross Sea. Here we investigate the provenance of size-selected dust deposited on sea ice in McMurdo Sound, south-western (SW) Ross Sea. The isotopic signature of McMurdo Sound dust (0.70533 87 Sr/ 86 Sr .70915 and -1.1 ε Nd (0) .45) confirms that dust is locally sourced from the McMurdo Sound debris bands and comprises a two-component mixture of McMurdo Volcanic Group and southern Victoria Land lithologies. In addition, the provenance of lithogenic sediment trapped in the water column was investigated, and the isotopic signature (ε Nd (0)=3.9, 87 Sr/ 86 Sr=0.70434) is differentiated from long-range transported dust originating from South America and Australia. Elevated lithogenic accumulation rates in deeper sediment traps in the Ross Sea suggest that sinking particles in the water column cannot simply result from dust input at the surface. This discrepancy can be best explained by significant upwelling and remobilization of lithogenic Fe from the sea floor.
Trace metals Cd, Co, Cu, Ni, and Zn in waters of the subantarctic and Polar Frontal Zones south of Tasmania during the 'SAZ-Sense' project
Publisher: Elsevier BV
Date: 2013
Understanding the variability in the iron concentration of Antarctic krill
Publisher: Wiley
Date: 19-05-2016
DOI: 10.1002/LNO.10322
Pre-concentration of thorium and neodymium isotopes using Nobias chelating resin: Method development and application to chromatographic separation
Publisher: Elsevier BV
Date: 09-2019
DOI: 10.1016/J.TALANTA.2019.03.086
Abstract: The isotopes of thorium (Th) and neodymium (Nd) are used as tracers in oceanography, and are key parameters in the international GEOTRACES program. The very low concentrations of Th and Nd as well as the reactive nature of Th isotopes makes the analysis of seawater s les a complex process. Analysis requires time-consuming pre-concentration from over 5 L of seawater. We describe a method to simultaneously pre-concentrate dissolved Th and Nd from acidified seawater s les using the Nobias
Suitability of high-volume aerosol samplers for ultra-trace aerosol iron measurements in pristine air masses: blanks, recoveries and bugs
Publisher: Copernicus GmbH
Date: 08-04-2016
DOI: 10.5194/AMT-2016-12
Abstract: Abstract. Atmospheric inputs of soluble iron (Fe) to the global ocean are an important factor determining marine primary productivity and nitrogen fixation. To investigate soluble aerosol Fe and fractional Fe solubility, marine aerosol s ling has been conducted from a number of platforms including aerosol towers, ship and buoy platforms. A number of these studies have used commercially available high-volume aerosol s lers to collect aerosols from large volumes of air. These s lers are attractive for s ling air from low Fe air masses since they can rapidly concentrate large volumes improving detection limits. Here we investigate the use of a high-volume s ler from the Cape Grim Baseline Air Pollution Station (CGBAPS), Tasmania, Australia to s le aerosol Fe from baseline Southern Ocean air-masses. The study followed the United States Environmental Protection Agency (EPA) standard for the s ling of ambient air using high-volume s ler, and the recommendations and protocols from GEOTRACES community for s ling, s le preparation and digestion of trace element aerosols. Analysis and inspection of exposure blank (one month exposure) filters for Fe, and other metals, revealed significant contamination resulting from passive deposition of local soil, plants and insects. The results of the study suggest that high-volume aerosol s lers may not be suitable for low concentration air masses over the Southern Ocean without some mechanism to hermetically seal the s ler when the baseline s ling criteria are not met.
Manganese biogeochemistry in the Southern Ocean, from Tasmania to Antarctica
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.
Dry season aerosol iron solubility in tropical northern Australia
Publisher: Copernicus GmbH
Date: 14-10-2016
DOI: 10.5194/ACP-16-12829-2016
Abstract: Abstract. Marine nitrogen fixation is co-limited by the supply of iron (Fe) and phosphorus in large regions of the global ocean. The deposition of soluble aerosol Fe can initiate nitrogen fixation and trigger toxic algal blooms in nitrate-poor tropical waters. We present dry season soluble Fe data from the Savannah Fires in the Early Dry Season (SAFIRED) c aign in northern Australia that reflects coincident dust and biomass burning sources of soluble aerosol Fe. The mean soluble and total aerosol Fe concentrations were 40 and 500 ng m−3 respectively. Our results show that while biomass burning species may not be a direct source of soluble Fe, biomass burning may substantially enhance the solubility of mineral dust. We observed fractional Fe solubility up to 12 % in mixed aerosols. Thus, Fe in dust may be more soluble in the tropics compared to higher latitudes due to higher concentrations of biomass-burning-derived reactive organic species in the atmosphere. In addition, biomass-burning-derived particles can act as a surface for aerosol Fe to bind during atmospheric transport and subsequently be released to the ocean upon deposition. As the aerosol loading is dominated by biomass burning emissions over the tropical waters in the dry season, additions of biomass-burning-derived soluble Fe could have harmful consequences for initiating nitrogen-fixing toxic algal blooms. Future research is required to quantify biomass-burning-derived particle sources of soluble Fe over tropical waters.
Biological Uptake, Water Mass Mixing and Scavenging Limit the Transport of Manganese‐Rich Waters From the East Antarctic Shelf
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.
The Sensitivity Analysis on GNSS-R Soil Moisture Retrieval
Publisher: IEEE
Date: 21-11-2021
Dissolved iron and iron(II) distributions beneath the pack ice in the East Antarctic (120°E) during the winter/spring transition
Publisher: Elsevier BV
Date: 09-2016
The GEOTRACES Intermediate Data Product 2017
Publisher: Elsevier BV
Date: 08-2018
Biogeochemical iron budgets of the Southern Ocean south of Australia: Decoupling of iron and nutrient cycles in the subantarctic zone by the summertime supply
Publisher: American Geophysical Union (AGU)
Date: 12-2009
DOI: 10.1029/2009GB003500
Insights Into the Biogeochemical Cycling of Iron, Nitrate, and Phosphate Across a 5,300 km South Pacific Zonal Section (153°E–150°W)
Publisher: American Geophysical Union (AGU)
Date: 02-2018
DOI: 10.1002/2017GB005736
Size fractionation of iron, manganese and aluminium in Antarctic fast ice reveals a lithogenic origin and low iron solubility
Publisher: Elsevier BV
Date: 04-2014
Hydrothermal contribution to the oceanic dissolved iron inventory
Publisher: Springer Science and Business Media LLC
Date: 14-03-2010
DOI: 10.1038/NGEO818
Developing standards for dissolved iron in seawater
Publisher: American Geophysical Union (AGU)
Date: 13-03-2007
DOI: 10.1029/2007EO110003
Iron biogeochemistry in Antarctic pack ice during SIPEX-2
Publisher: Elsevier BV
Date: 09-2016
Advances in the offline trace metal extraction of Mn, Co, Ni, Cu, Cd, and Pb from open ocean seawater samples with determination by sector field ICP-MS analysis
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.
Multiple sources of soluble atmospheric iron to Antarctic waters
Publisher: American Geophysical Union (AGU)
Date: 03-2016
DOI: 10.1002/2015GB005265
Physical speciation and solubility of iron from baleen whale faecal material
Publisher: Elsevier BV
Date: 08-2017
Fractional iron solubility of atmospheric iron inputs to the Southern Ocean
Publisher: Elsevier BV
Date: 12-2015
Earth, Wind, Fire, and Pollution: Aerosol Nutrient Sources and Impacts on Ocean Biogeochemistry
Publisher: Annual Reviews
Date: 03-01-2021
DOI: 10.1146/ANNUREV-MARINE-031921-013612
Abstract: A key Earth system science question is the role of atmospheric deposition in supplying vital nutrients to the phytoplankton that form the base of marine food webs. Industrial and vehicular pollution, wildfires, volcanoes, biogenic debris, and desert dust all carry nutrients within their plumes throughout the globe. In remote ocean ecosystems, aerosol deposition represents an essential new source of nutrients for primary production. The large spatiotemporal variability in aerosols from myriad sources combined with the differential responses of marine biota to changing fluxes makes it crucially important to understand where, when, and how much nutrients from the atmosphere enter marine ecosystems. This review brings together existing literature, experimental evidence of impacts, and new atmospheric nutrient observations that can be compared with atmospheric and ocean biogeochemistry modeling. We evaluate the contribution and spatiotemporal variability of nutrient-bearing aerosols from desert dust, wildfire, volcanic, and anthropogenic sources, including the organic component, deposition fluxes, and oceanic impacts.
A mesoscale phytoplankton bloom in the polar Southern Ocean stimulated by iron fertilization
Publisher: Springer Science and Business Media LLC
Date: 10-2000
DOI: 10.1038/35037500
Abstract: Changes in iron supply to oceanic plankton are thought to have a significant effect on concentrations of atmospheric carbon dioxide by altering rates of carbon sequestration, a theory known as the 'iron hypothesis'. For this reason, it is important to understand the response of pelagic biota to increased iron supply. Here we report the results of a mesoscale iron fertilization experiment in the polar Southern Ocean, where the potential to sequester iron-elevated algal carbon is probably greatest. Increased iron supply led to elevated phytoplankton biomass and rates of photosynthesis in surface waters, causing a large drawdown of carbon dioxide and macronutrients, and elevated dimethyl sulphide levels after 13 days. This drawdown was mostly due to the proliferation of diatom stocks. But downward export of biogenic carbon was not increased. Moreover, satellite observations of this massive bloom 30 days later, suggest that a sufficient proportion of the added iron was retained in surface waters. Our findings demonstrate that iron supply controls phytoplankton growth and community composition during summer in these polar Southern Ocean waters, but the fate of algal carbon remains unknown and depends on the interplay between the processes controlling export, remineralisation and timescales of water mass subduction.
Dry season aerosol iron solubility in tropical northern Australia
Publisher: Copernicus GmbH
Date: 17-06-2016
DOI: 10.5194/ACP-2016-419
Abstract: Abstract. Marine nitrogen fixation is co-limited by the supply of iron and phosphorus in large areas of the global ocean. Up to 75 % of marine nitrogen fixation may be limited by iron supply due to the relatively high iron requirements of planktonic diazotrophs (Berman-Frank et al., 2001). The deposition of soluble aerosol iron can initiate nitrogen fixation and trigger toxic algal blooms in nitrate-poor tropical waters. There is a large variability in estimates of soluble iron, related to the mixing of aerosol iron sources. Most studies assume that mineral dust represents the primary source of soluble iron in the atmosphere. However, seasonal biomass burning in tropical regions is a potential source of aerosol iron that could explain the large variability of soluble iron in those regions. To investigate aerosol iron sources to the adjacent tropical waters of Australia, the fractional solubility of aerosol iron was determined during the Savannah Fires in the Early Dry Season (SAFIRED) c aign at Gunn Point, Northern Territory, Australia during the dry season in 2014. The source of particulate matter less than 10 µm (PM10) aerosol iron was a mixture of mineral dust, fresh biomass burning aerosol, sea spray and anthropogenic pollution. The mean soluble and total aerosol iron concentrations were 40 and 500 ng m−3 respectively. Fractional Fe solubility was relativity high for the majority of the c aign and averaged 8 % but dropped to 3 % during the largest and most proximal fire event. Fractional Fe solubility and proxies for biomass burning (elemental carbon, levoglucosan, oxalate and carbon monoxide) were unrelated throughout the c aign. An explanation of the lack of correlation between fractional Fe solubility and elemental carbon at the biomass burning source is due to the physical properties of elemental carbon, i.e., fresh elemental carbon aerosols are initially hydrophobic, however they can disperse in water after aging and coating with water soluble species in the atmosphere. Combustion aerosols are thought to have a high factional Fe solubility, which can increase during atmospheric transport from the source. Although, biomass burning derived particles may not be a direct source of soluble iron, they can act indirectly as a surface for aerosols iron to bind during atmospheric transport and subsequently be released to the ocean upon deposition. In addition, biomass burning derived aerosols can indirectly impact the fractional solubility of mineral dust. Fractional Fe solubility was highest during dust events at Gunn Point, and could have been enhanced by mixing with biomass burning derived aerosols. Iron in dust may be more soluble in the tropics compared to higher latitudes due to the presence higher concentrations of biomass burring derived reactive organic species in the atmosphere, such as oxalate, and their potential to enhance the fractional Fe solubility of mineral dust. As the aerosol loading is dominated by biomass burning emissions over the tropical waters in the dry season, additions of biomass burning derived soluble iron could have harmful consequences for initiating nitrogen fixing toxic algal blooms. Future research is required to quantify biomass burning derived particle sources of soluble iron over tropical waters.
Distribution of dissolved iron in Antarctic sea ice: Spatial, seasonal, and inter-annual variability
Publisher: American Geophysical Union (AGU)
Date: 31-08-2010
DOI: 10.1029/2009JG001031
Latex-Coated Polymeric Monolithic Ion-Exchange Stationary Phases. 1. Anion-Exchange Capillary Electrochromatography and In-Line Sample Preconcentration in Capillary Electrophoresis
Publisher: American Chemical Society (ACS)
Date: 07-12-2004
DOI: 10.1021/AC048748D
Abstract: A sulfonated methacrylate monolithic polymer has been synthesized inside fused-silica capillaries of diameters 50-533-microm i.d. and coated with 65-nm-diameter fully functionalized quaternary ammonium latex particles (AS18, Dionex Corp.) to form an anion-exchange stationary phase. This stationary phase was used for ion-exchange capillary electrochromatography of inorganic anions in a 75-microm-i.d. capillary with Tris erchlorate electrolyte and direct UV detection at 195 nm. Seven inorganic anions (bromide, nitrate, iodide, iodate, bromate, thiocyanate, chromate) could be separated over a period of 90 s, and the elution order indicated that both ion exchange and electrophoresis contributed to the separation mechanism. Separation efficiencies of up to 1.66 x 10(5) plates m(-1) were achieved, and the monoliths were stable under pressures of up to 62 MPa. Another latex-coated monolith in a 250-microm-i.d. capillary was used for in-line preconcentration by coupling it to a separation capillary in which the EOF had been reversed using a coating of either a cationic polymer or cationic latex particles. Several capillary volumes of s le were loaded onto the preconcentration monolith, and the analytes (inorganic anions) were then eluted from the monolith with a transient isotachophoretic gradient before being separated by electrophoresis in the separation capillary. Linear calibration curves were obtained for aqueous mixtures of bromide, nitrite, nitrate, and iodide. Recoveries of all analytes except iodide were reduced significantly when the s le matrix contained high levels of chloride. The preconcentration method was applied to the determination of iodide in open ocean water and provided a limit of detection of 75 pM (9.5 ng/L) calculated at a signal-to-noise ratio of 3. The relative standard deviation for migration time and peak area for iodide were 1.1 and 2.7%, respectively (n = 6). Iodide was eluted as an efficient peak, yielding a separation efficiency of 5.13 x 10(7) plates m(-1). This focusing was reproducible for repeated analyses of seawater.
The GEOTRACES Intermediate Data Product 2014
Publisher: Elsevier BV
Date: 12-2015
Effect of natural iron fertilization on carbon sequestration in the Southern Ocean
Publisher: Springer Science and Business Media LLC
Date: 04-2007
DOI: 10.1038/NATURE05700
Abstract: The availability of iron limits primary productivity and the associated uptake of carbon over large areas of the ocean. Iron thus plays an important role in the carbon cycle, and changes in its supply to the surface ocean may have had a significant effect on atmospheric carbon dioxide concentrations over glacial-interglacial cycles. To date, the role of iron in carbon cycling has largely been assessed using short-term iron-addition experiments. It is difficult, however, to reliably assess the magnitude of carbon export to the ocean interior using such methods, and the short observational periods preclude extrapolation of the results to longer timescales. Here we report observations of a phytoplankton bloom induced by natural iron fertilization--an approach that offers the opportunity to overcome some of the limitations of short-term experiments. We found that a large phytoplankton bloom over the Kerguelen plateau in the Southern Ocean was sustained by the supply of iron and major nutrients to surface waters from iron-rich deep water below. The efficiency of fertilization, defined as the ratio of the carbon export to the amount of iron supplied, was at least ten times higher than previous estimates from short-term blooms induced by iron-addition experiments. This result sheds new light on the effect of long-term fertilization by iron and macronutrients on carbon sequestration, suggesting that changes in iron supply from below--as invoked in some palaeoclimatic and future climate change scenarios--may have a more significant effect on atmospheric carbon dioxide concentrations than previously thought.
Size-fractionated labile trace elements in the Northwest Pacific and Southern Oceans
Publisher: Elsevier BV
Date: 09-2011
Supplementary material to "Suitability of high-volume aerosol samplers for ultra-trace aerosol iron measurements in pristine air masses: blanks, recoveries and bugs"
Publisher: Copernicus GmbH
Date: 08-04-2016
Widespread phytoplankton blooms triggered by 2019–2020 Australian wildfires
Publisher: Springer Science and Business Media LLC
Date: 15-09-2021
DOI: 10.1038/S41586-021-03805-8
Abstract: Droughts and climate-change-driven warming are leading to more frequent and intense wildfires
Fast and sensitive determination of aluminium with RP-HPLC using an ultra-short monolithic column
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1AY05192J
Biogeochemical observations during the winter–spring transition in East Antarctic sea ice: Evidence of iron and exopolysaccharide controls
Publisher: Elsevier BV
Date: 08-2009
Quantifying Lithogenic Inputs to the Southern Ocean Using Long-Lived Thorium Isotopes
Publisher: Frontiers Media SA
Date: 22-04-2020
A preliminary model of iron fertilisation by baleen whales and Antarctic krill in the Southern Ocean: Sensitivity of primary productivity estimates to parameter uncertainty
Publisher: Elsevier BV
Date: 2016
Impact of the natural Fe-fertilization on the magnitude, stoichiometry and efficiency of particulate biogenic silica, nitrogen and iron export fluxes
Publisher: Elsevier BV
Date: 11-2016
PHYTOPLANKTON SELENIUM REQUIREMENTS: THE CASE FOR SPECIES ISOLATED FROM TEMPERATE AND POLAR REGIONS OF THE SOUTHERN HEMISPHERE1
Publisher: Wiley
Date: 30-04-2012
DOI: 10.1111/J.1529-8817.2012.01153.X
Abstract: A series of laboratory culture experiments was used to investigate the effect of selenium (Se, 0-10 nM) on the growth, cellular volume, photophysiology, and pigments of two temperate and four polar oceanic phytoplankton species [coccolithophore Emiliania huxleyi (Lohmann) W. W. Hay et H. P. Mohler, cyanobacterium Synechococcus sp., prymnesiophyte Phaeocystis sp., and three diatoms-Fragilariopsis cylindrus (Grunow) Kriegar, Chaetoceros sp., and Thalassiosira antarctica G. Karst.]. Only Synechoccocus sp. and Phaeocystis sp. did not show any requirement for Se. Under Se-deficient conditions, the growth rate of E. huxleyi was decreased by 1.6-fold, whereas cellular volume was increased by 1.9-fold. Se limitation also decreased chl a (2.5-fold), maximum relative electron transport rate (1.9-fold), and saturating light intensity (2.8-fold), suggesting that Se plays a role in photosynthesis or high-light acclimation. Pigment analysis for Antarctic taxa provided an interesting counterpoint to the physiology of E. huxleyi. For all Se-dependent Antarctic diatoms, Se limitation decreased growth rate and chl a content, whereas cellular volume was not affected. Pigment analysis revealed that other pigments were affected under Se deficiency. Photoprotective pigments increased by 1.4-fold, while diadinoxanthin:diatoxanthin ratios decreased by 1.5- to 4.9-fold under Se limitation, supporting a role for Se in photoprotection. Our results demonstrate an Se growth requirement for polar diatoms and indicate that Se could play a role in the biogeochemical cycles of other nutrients, such as silicic acid in the Southern Ocean. Se measurements made during the austral summer in the Southern Ocean and Se biological requirement were used to discuss possible Se limitation in phytoplankton from contrasting oceanographic regions.
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