This dataset contains real-time total dissolved iron concentrations ((Fe(II) + Fe(III); µmol/l) acquired from the EMSO-Azores seafloor observatory from September 2013 to February 2014 (n=332). Data are purchased by the CHEMINI Fe (CF1), a CHEmical MINIaturized analyser dedicated to in situ determination of iron concentrations (every 24 hours, with in situ calibration using a 25 µmol/l iron standard, Vuillemin et al., 2009). The instrument is deployed on TEMPO part of Seamon East environmental monitoring node. The sample inlet is located on a mussel bed at the base of the Eiffel Edifice at 1695m depth.