Easy come, easy go: The vulnerability of mineral-associated organic matter in dynamic redox environments

We often think of organo-mineral interactions as long-term mechanisms protecting carbon from microbial attack. However, the mineral phases most effective as sorbents for organic matter may also be particularly vulnerable to dissolution—especially iron. Microbially-driven iron redox cycling may be widespread across terrestrial and aquatic ecosystems—from Iowa cornfields to tropical forests. Iron reduction frequently occurs within microsites of bulk aerobic soils. Consequently, iron-associated organic matter may vulnerable to release and rapid decomposition in dynamic redox environments. Positive correlations between short-range-ordered iron and carbon concentrations may reflect transient associations, not necessarily long-term stabilization—as supported by new isotopic evidence.