Oxidative iron species and ocean challenges: a perspective

The idea of using oxidative iron (Fe(6+)) to manage fouling and potentially invasive and pathogenic species in ballast water has merit and is attractive when viewed in the broadest context. Ferrate (Fe(6+)) has potential in ballast water management because it reduces a complex global problem to a single issue, viz.how to dispose of the waste which is predominantly Fe(3+). Waste iron disposal must be considered carefully because iron limits photosynthesis in oligotrophic oceans, alters physiological processes in bacteria and animals, produces reactive oxygen species, causes nitrosative stress and increased availability enhances the virulence of pathogenic bacteria. The case is made that the oxidative iron waste should be recycled rather than discharged into the ocean.