Long term in situ survey of total dissolved iron concentrations on the MoMAR observatory

Study of the temporal dynamics of faunal assemblages and their habitat at the Lucky strike vent was performed using the TEMPO ecological module on the MoMAR (Monitoring of the Mid-Atlantic Ridge) deep sea observatory. An in situ analyzer (CHEMINI) was implemented onto this structure in order to determine total dissolved iron concentrations associated with an optode and a temperature probe. Hence, we present here the long term in situ analysis of total dissolved iron (6 months, 2013-2014) at the Eiffel Tower edifice. The daily analyzed in situ standard (25μmol.L-1) showed an excellent reproducibility (1.07%, n=522), illustrating the good analytical performances of the CHEMINI, validating the iron concentrations measured by the instrument. CHEMINI was reliable, robust over time for in situ analysis. The averaged total dissolved iron concentrations for the 6 months period remain low ([DFe] = 7.12 ± 2.11 μmol L-1, n = 519), but display some noticeable variations related to the temperature. Indeed, iron and temperature correlated significantly, and frequency spectra indicated a maximal contribution of frequencies around 4-5 days for both variables.