Fig. 4: Schematic figure of benthic iron cycling.

Illustration of the production of ascorbate-extractable Fe (FeA) and microbially extractable Fe (FeM), which is labile and potentially bioavailable Fe, at the oxic-anoxic interface in fjord sediments. These sediments are unique to other marine sediments, as glacial input provides huge quantities of Fe(III) and Fe(II) bearing minerals to the sediment surface.