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

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