We present data from a recent cruise to the Oxygen Minimum Zone off the coast of Mexico. Ship board measurements were performed for Fe(II) and H2O2 and samples were also collected for total Fe analysis. A STOX sensor made it possible to determination ultra-low oxygen concentrations. Previous work revealed a close relationship between Fe(II) and nitrite accumulation in the secondary nitrite maximum (SNM). This relationship suggests that Fe(II) and nitrate reduction may be linked. Southern Mexico is distinct from other regimes in that the Fe(II) maximum is often significantly shallower than the SNM and in some instances coincides with a deep chlorophyll maximum. Comparison of Fe(II) data with O2 measurements show that the complete disappearance of oxygen is required before Fe(II) accumulates. In offshore stations, Fe(II) comprised up to 30% of the total dissolved Fe. In nearshore stations where Fe was much higher, it reached 100% of the total.

Distribution of Fe(II), H2O2 and O2 in the Mexican OMZ: Potential biogeochemical processes causing their occurrence

245th National Meeting (2013)

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