Complexation by organic ligands dominates the speciation of iron Fe , copper Cu , and other bioactive trace metals in seawater, controlling their bioavailability and distribution in the marine environment. Several classes of high-affinity Fe-binding ligands siderophores have been identified in seawater but the chemical structures of marine Cu-complexing ligands remain unknown.
Immobilized metal-ion affinity chromatography IMAC allows Cu ligands to be isolated from bulk dissolved organic matter DOM in seawater and separated into fractions, which can be characterized independently using electrochemical and spectroscopic techniques.
One-liter samples of 0. Fractions eluted with acidified artificial seawater were desalted and re-suspended in methanol via solid-phase extraction SPE to obtain extracts suitable for ESI-MS analysis. Cu II -IMAC fractionation of unspiked seawater using multiple UV detection wavelengths suggests an optimal fraction size of 2 mL for isolating and analyzing Cu ligands with similar properties.
Organic complexation of dissolved trace metals like iron Fe and copper Cu exerts a major influence on their mobility, toxicity, and bioavailability in the marine environment Florence, ; Sunda, ; Donat and Bruland, ; Kraemer, Several classes of biogenic high-affinity Fe-binding ligands siderophores have been identified in seawater and are thought to facilitate iron uptake in marine bacterioplankton Wilhelm, ; Hutchins et al.
Culturing experiments have shown that marine phytoplankton are also capable of producing strong, extracellular Cu-binding ligands McKnight and Morel, , ; Moffett et al. Some of these exudates are thought to act like chalkophores Semeniuk et al. Although numerous studies have shown that Cu in seawater exists primarily in the form of organic complexes see Donat and Bruland, no marine copper ligands have been positively identified.
