California Sea Grant College Program

Iron is arguably the most important micronutrient in the marine environment due to its involvement in many vital physiological processes, such as photosynthesis, oxygen transport, electron transfer and nitrogen fixation. However, the availability of iron is hampered by its poor solubility and tendency to form biologically inaccessible colloidal and oxo-polymeric species. This lack of availability is more pronounced in the oceanic environment where the solubility of iron(III) is even lower than in most terrestrial environments and where the majority of soluble iron is complexed by organic ligands that dominate its speciation. Consequently, iron has been shown to limit microorganisms in large areas of the ocean.