The transport of metal-binding humic substances and dissolved iron from a hydrothermal vent site (TAG, North Atlantic)
To investigate the organic ligand pool supporting hydrothermal-derived DFe at a slow-spreading ridge, samples were collected during the HERMINE (GEOTRACES GPrA07) cruise around the TAG vent site in March 2017. Here we present the concentrations of dissolved metal-binding HS and compare results to DFe transport along the detailed transect. High-resolution sampling around the vent consisted of 5 stations in the first 2 km, followed by a 75 km transect of 4 additional stations following the plume using L-ADCP data. In the upper 2800 m at the vent site, HS concentrations represented typical open ocean values. In contrast, within the rising and non-buoyant plume, HS concentrations were much more variable and included the highest and lowest concentrations of the water column, but all at iron-binding equivalents well below (~1-20%) DFe concentrations. However, by 10 km away, DFe concentrations fell to within the range of iron-binding equivalents of the HS, suggesting a sizeable proportion of transported DFe (~40-100%) could be accounted for by complexation with HS.
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