Effect of salinity and temperature on the determination of dissolved iron-binding organic ligands in the polar marine environment

Genovese, Cristina; Grotti, Marco; Ardini, Francisco; Wuttig, Kathrin; Vivado, Davide; Cabanes, Damien; Townsend, Ashley T.; Hassler, Christel; Lannuzel, Delphine

doi:10.1016/j.marchem.2021.104051

Cited by 4 publications

(3 citation statements)

References 82 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Elevated concentrations of Lt are observed when SA and NN are used, whereas increased Log K FeL values were recorded for studies using TAC (Figure 6D, irrespective of high values recorded during the ENRICH survey). Such observations have also been made in the Arctic (Ardiningsih et al, 2021b) and conditional stability constants have been noted to only provide a rough estimate of binding strength (Gerringa et al, 2021) which varies with salinity, temperature, and pH, depending on the selected method (Genovese et al, 2022). Therefore, understanding whether trends between Fe-binding ligands and environmental variables are linked to true seasonal supply mechanisms or analytical variability will be crucial to complexation studies going forward.…”

Section: The Mertz Region and Southern Ocean Ligand Collectionmentioning

confidence: 96%

Identifying potential sources of iron-binding ligands in coastal Antarctic environments and the wider Southern Ocean

et al. 2022

Self Cite

View full text Add to dashboard Cite

The availability of iron (Fe) to marine microbial communities is enhanced through complexation by ligands. In Fe limited environments, measuring the distribution and identifying the likely sources of ligands is therefore central to understanding the drivers of marine productivity. Antarctic coastal marine environments support highly productive ecosystems and are influenced by numerous sources of ligands, the magnitude of which varies both spatially and seasonally. Using competitive ligand exchange adsorptive cathodic stripping voltammetry (CLE-AdCSV) with 2-(2-thiazolylazo)-p-cresol (TAC) as a competing artificial ligand, this study investigates Fe-binding ligands (FeL) across the continental shelf break in the Mertz Glacier Region, East Antarctica (64 - 67°S; 138 - 154°E) during austral summer of 2019. The average FeL concentration was 0.86 ± 0.5 nM Eq Fe, with strong conditional stability constants (Log KFeL) averaging 23.1 ± 1.0. The strongest binding ligands were observed in modified circumpolar deep water (CDW), thought to be linked to bacterial Fe remineralisation and potential siderophore release. High proportions of excess unbound ligands (L’) were observed in surface waters, as a result of phytoplankton Fe uptake in the mixed layer and euphotic zone. However, FeL and L’ concentrations were greater at depth, suggesting ligands were supplied with dissolved Fe from upwelled CDW and particle remineralisation in benthic nepheloid layers over the shelf. Recent sea-ice melt appeared to support bacterial production in areas where Fe and ligands were exhausted. This study is included within our newly compiled Southern Ocean Ligand (SOLt) Collection, a database of publicly available Fe-binding ligand surveys performed south of 50°S. A review of the SOLt Collection brings attention to the paucity of ligand data collected along the East Antarctic coast and the difficulties in pinpointing sources of Fe and ligands in coastal environments. Elucidating poorly understood ligand sources is essential to predicting future Fe availability for microbial populations under rapid environmental change.

show abstract

Section: The Mertz Region and Southern Ocean Ligand Collectionmentioning

confidence: 96%

Identifying potential sources of iron-binding ligands in coastal Antarctic environments and the wider Southern Ocean

et al. 2022

Self Cite

View full text Add to dashboard Cite

show abstract

“…It is also important to note that the metal speciation we measure in the laboratory at room temperature and with buffered pH may not best represent in situ speciation. For example, sea ice and brine samples come from a wide range of temperature and salinity conditions, and speciation measurements made under typical conditions can be different from those in the natural environment (Hassler et al, 2013;Genovese et al, 2022). Microscale processes that are not reflected by bulk phycosphere (the micrometer scale region immediately surrounding a phytoplankton cell), such as pH and oxygen concentrations, can also be very different from bulk seawater on which we perform our analyses, resulting in different organic and inorganic speciation (Liu et al, 2020).…”

Section: Moving Forward: Understanding Bioavailabilitymentioning

confidence: 99%

New Insights into the Organic Complexation of Bioactive Trace Metals in the Global Ocean from the GEOTRACES Era

Whitby,

Park,

Shaked

et al. 2024

Oceanog

View full text Add to dashboard Cite

The GEOTRACES program has greatly expanded measurements of dissolved trace metal concentrations across ocean basins, but to understand the behavior and cycling of metals and their impacts on primary productivity, we must understand the chemical forms in which they are present in the environment. Organic ligands play a central role in the speciation and cycling of trace metals in the marine environment, controlling their chemical reactivity and bioavailability. Here, we present an overview of the contributions the GEOTRACES program has made to understanding ocean metal speciation through advancing our knowledge of the distribution, sources, and sinks of metal-binding organic ligands across the global ocean, particularly for iron. Detailed assessments and intercalibration of the speciation methods most commonly applied have allowed integration of metal-binding ligand measurements across datasets. Work to characterize specific ligand groups within the wider pool of dissolved organic matter, along with their sources and sinks, is starting to unravel the role of metal-binding organic ligands in global biogeochemical cycles. Recent advances in complementary analytical techniques using liquid chromatography and mass spectrometry present a molecular picture of metal speciation and bioavailability—and also pose new questions. Moving forward, we need to address knowledge gaps in our understanding of how metal speciation and complexation relates to bioavailability in order to recognize the impacts of ocean metal distributions and cycling on marine productivity and the global carbon cycle.

show abstract

“…In this September samples, we detected a strong ligand concentration of 4.6 nM and a strong binding capacity, logK cond CuL,Cu 2+ , of 15.0, supporting current understanding of SoG estuarine circulation, where offshore NE Pacific water between 100 and 200 m travels into the SoG's intermediate water year-round through Juan de Fuca and Haro Strait. While variations in salinity and equilibration times can impact comparisons between trace metal speciation studies (Buck and Bruland, 2005;Genovese et al, 2022), deep SoG waters and P4 have comparable salinities (ie., 31.8-34.5 psu for P4 and 30.4 in 100 m Sept) and equilibration times (i.e., > 8 hours for P4 and >12 hours for 100 m Sept).…”

Section: Analytical Window Comparisonmentioning

confidence: 99%

Seasonal dissolved copper speciation in the Strait of Georgia, British Columbia, Canada

et al. 2022

View full text Add to dashboard Cite

The Strait of Georgia (SoG) is a semi-enclosed, urban basin with seasonally dependent estuarine water circulation, dominantly influenced by Northeast Pacific waters and the Fraser River. To establish a baseline and understand the fate and potential toxicity of Cu in the SoG, we determined seasonal and spatial depth profiles of dissolved Cu (dCu) speciation, leading to estimates of the free hydrated copper (Cu2+) concentrations, as a proxy for Cu toxicity. The concentration of dCu was largely controlled by conservative mixing of the ocean and freshwater endmembers in the SoG. In all samples, ligand concentrations exceeded dCu, by a ratio greater than 1.5, resulting in the complexation of 99.98% of the dCu by strong binding organic ligands. The concentrations of Cu2+ were less than 10-13.2 M, significantly lower than the well-established Cu toxicity threshold (10-12 M Cu2+) for microorganisms. Our results indicate that ambient Cu-binding ligands effectively buffer Cu2+ concentrations within the Strait of Georgia, posing no threat to marine life. In almost 90% of the samples, the ligands were best classified as a single ligand class, with a logKCuL,Cu2+cond between 12.5 and 14.1. The concentrations of these single class ligands were greatest in warm, low salinity, nutrient depleted waters, suggesting that either terrestrially sourced ligands dominate dCu speciation in the SoG, or freshwater sources in the SoG establish the conditions that promote the production of Cu binding ligands in its surface waters. The remaining 10% of the samples were from the euphotic zone, where we detected a stronger ligand class, L1, of logKCuL1,Cu2+cond between 13.5 and 14.3, and a weaker ligand class, L2, of logKCuL2,Cu2+cond between 11.5 and 12.3. In these surface samples, logKCuL1,Cu2+cond and logKCuL2,Cu2+cond were positively correlated with temperature, while L2 concentrations were positively correlated with chromophoric dissolved organic matter of terrestrial origin. This study is the first to perform hierarchal clustering of a trace metal speciation dataset and enabled the distinction of 6 clusters across season, depth, and region of the SoG, highlighting the influence of freshwater and open ocean ligand sources, conservative mixing dynamics, and particulate Cu concentrations on dCu speciation within estuarine basins.

show abstract

Effect of salinity and temperature on the determination of dissolved iron-binding organic ligands in the polar marine environment

Cited by 4 publications

References 82 publications

Identifying potential sources of iron-binding ligands in coastal Antarctic environments and the wider Southern Ocean

Identifying potential sources of iron-binding ligands in coastal Antarctic environments and the wider Southern Ocean

New Insights into the Organic Complexation of Bioactive Trace Metals in the Global Ocean from the GEOTRACES Era

Seasonal dissolved copper speciation in the Strait of Georgia, British Columbia, Canada

Contact Info

Product

Resources

About