Natural copper-binding ligands in the Arctic Ocean. The influence of the Transpolar Drift (GEOTRACES GN04)

• Published in: Frontiers in Marine Science
• Main Authors: Arnone, Veronica, Santana-casiano, J. Magdalena, González-dávila, Melchor, Planquette, Helene, Sarthou, Geraldine, Gerringa, Loes J. A., González, Aridane G.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Frontiers Media SA 2023
• Subjects: copper; copper-binding ligands; voltammetric method; Arctic Ocean; Transpolar Drift; amundsen basin; Arctic; Barents Sea; Fram Strait; makarov basin; Nansen Basin; Nordic Seas; Sea ice
• Online Access: https://archimer.ifremer.fr/doc/00869/98126/107415.pdf; https://archimer.ifremer.fr/doc/00869/98126/107416.docx; https://doi.org/10.3389/fmars.2023.1306278; https://archimer.ifremer.fr/doc/00869/98126/

The Arctic Ocean is a unique biogeochemical environment characterized by low salinity surface waters, extensive sea-ice coverage, high riverine inputs, large shelf extension and the long residence time of deep waters. These characteristics determine the distribution of dissolved bio-essential trace metals, such as copper (Cu), and the dissolved organic-binding ligands capable of complexing it. This work reports the concentrations and conditional stability constants of dissolved Cu-binding ligands (LCu and log KcondCu2+L) measured in samples from the Polarstern (PS94) expedition, as part of the international GEOTRACES program (cruise GN04). Full-depth profile stations from the Barents Sea, Nansen Basin, Amundsen Basin and Makarov Basin were analysed by competitive ligand exchange-adsorptive cathodic stripping voltammetry (CLE-AdCSV). The basins and water masses presented a wide range of LCu concentrations (range: 1.40 – 7.91 nM) and log KcondCu2+L values (range: 13.83 – 16.01). The highest variability of Cu-binding ligand concentrations was observed in surface waters (≤200 m), and mean concentrations increased from the Barents Sea and Nansen Basin (2.15 ± 0.31 nM and 1.93 ± 0.35 nM, respectively) to the Amundsen (3.84 ± 1.69 nM) and Makarov Basins (4.40± 2.03 nM). The influence of the Transpolar Drift (TDP) flow path was observed in the Amundsen and Makarov Basins, especially on Cu-binding ligand concentrations (LCu range: 3.96 – 7.91 nM). In contrast, deep waters (>200 m) showed no significant differences between basins and water masses in terms of LCu concentrations (range: 1.45 – 2.78 nM) and log KcondCu2+L (range: 14.02 – 15.46). The presence of strong Cu-binding ligands (log KcondCu2+L>13) in surface waters stabilises the excess of dissolved copper (dCu) transported in the TPD and favours its export to the Fram Strait and Nordic Seas.