Natural Fe-binding organic ligands in Fram Strait and over the Northeast Greenland shelf

• Published in: Marine Chemistry
• Main Authors: Ardiningsih, Indah, Krisch, Stephan, Lodeiro, Pablo, Reichart, Gert-Jan, Achterberg, Eric P., Gledhill, Martha, Middag, Rob, Gerringa, Loes J.A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2020
• Subjects: Arctic; Arctic Ocean; Greenland; Nioghalvfjerdsfjorden; Fram Strait; glacier; North Atlantic
• Online Access: https://oceanrep.geomar.de/id/eprint/49596/; https://oceanrep.geomar.de/id/eprint/49596/1/Ardiningsih.pdf; https://oceanrep.geomar.de/id/eprint/49596/7/354863.pdf; https://doi.org/10.1016/j.marchem.2020.103815

Highlights • Fe-binding ligands associated with primary productivity together with ligands from the Arctic Ocean are the main sources of Fe-binding ligands in surface waters of Fram Strait. • Fe-binding ligands are present in a high concentrations in front of the glacier terminus, but the ligands have a relatively low binding capacity, thus less reactive. • Low binding strength coupled with low competing strength of ligands result in a higher inorganic Fe concentration, causing Fe to precipitate or scavenged. Abstract There is a paucity of data on Fe-binding ligands in the Arctic Ocean. Here we investigate the distribution and chemical properties of natural Fe-binding ligands in Fram Strait and over the northeast Greenland shelf, shedding light on their potential sources and transport. Our results indicate that the main sources of organic ligands to surface waters of Fram Strait included primary productivity and supply from the Arctic Ocean. We calculated the mean total Fe-binding ligand concentration, [Lt], in Polar Surface Water from the western Fram Strait to be 1.65 ± 0.4 nM eq. Fe. This value is in between reported values for the Arctic and North Atlantic Oceans, confirming reports of north to south decreases in [Lt] from the Arctic Ocean. The differences between ligand sources in different biogeochemical provinces, resulted in distinctive ligand properties and distributions that are reflected in [Lt], binding strength (log KFe'L′) and competing strength (log αFe'L) of ligands. Higher [Lt] was present near the Nioghalvfjerdsfjorden (79 N) Glacier terminus and in the Westwind Trough (median of [Lt] = 2.17 nM eq. Fe; log KFe'L′ = 12.3; log αFe'L = 3.4) than in the Norske Trough (median of [Lt] = 1.89 nM eq. Fe; log KFe'L′= 12.8; log αFe'L = 3.8) and in Fram Strait (median of [Lt] = 1.38 nM eq. Fe; log KFe'L′ = 13; log αFe'L= 3.9). However, organic ligands near the 79 N Glacier terminus and in the Westwind Trough were weaker, and therefore less reactive than organic ligands in the Norske Trough and in Fram ...