Aquatic Sciences Meeting, Albuquerque 2001

SS02 Photochemical Reactions In Surface Waters: A Major Issue in the 21st Century? (Environmental Connections)

Date: Thursday, February 15, 2001, Time: 3:00:00 PM

Location: San Miguel

Barbeau, K, , Dept. of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA, barbeau@chem.ucsb.edu

Butler, A, , Dept. of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA, butler@chem.ucsb.edu

PHOTOLYSIS OF IRON-SIDEROPHORE COMPLEXES IN SEAWATER

Iron is a limiting nutrient for phytoplankton in significant areas of the ocean. Dissolved iron in the upper oceans occurs primarily in the form of complexes with strong organic ligands, which are believed to mediate iron's biological availability and geochemical cycle. A major fraction of the oceanic iron ligand pool is likely to be comprised of siderophores (high affinity iron(III) chelators produced by bacteria) or their breakdown products. We are using structurally-characterized siderophores produced by marine bacteria as model compounds to investigate the potential importance of photolysis as a sink for strong iron chelators in ocean surface waters. We have characterized the photochemical reactivity of common iron-binding functional groups found in marine siderophores (hydroxamate, catechol, and alpha-hydroxycarboxylate moieties). Our findings indicate that hydroxamate groups are photochemically stable, whereas catechol and alpha-hydroxycarboxylate groups exhibit varying degrees of photoreactivity, depending on the presence or absence of Fe(III). Thus, photolysis is likely to be an important loss process for strong iron-binding ligands in the upper ocean. Photochemical reactions of iron-siderophore complexes may also be a significant source of Fe(II) in surface seawater.

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Aquatic Sciences Meeting, Albuquerque 2001

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