Iron, which is necessary for the sustenance of life, is scarce in the ocean. National Science Foundation (NSF)-supported researchers found that light helps transform the mineral into a form that can be easily taken up by phytoplankton and other microorganisms. They report their findings in the September 27 issue of the journal Nature.

"This discovery helps us better understand one of the essential links in the ocean's food chain," said Donald Burland, acting director of NSF's Chemistry Division. "It may also have implications for global climate change, since living organisms are important in the absorption and release of carbon dioxide from the oceans."

Iron and other trace metals are important biochemical ingredients in the production of plankton, the most abundant organisms in seawater, which are at the bottom of the aquatic food chain. But iron is rare in surface seawater, and scientists believe it occurs almost entirely in complex molecules in which the iron is strongly bound by organic ligands presumed to be of biological origin. Bacteria produce small molecules called siderophores to help them obtain iron from their environments, and this process may contribute to the pool of tightly bound iron complexes.

"We determined that iron bound to the oceanic siderophores react to light," said chemist Alison Butler of the University of California at Santa Barbara. "This photochemical reaction helps transform the iron complexes into a form that enables marine organisms to more easily acquire the essential iron."

The sun's energy turns the molecules into more loosely bound configurations of iron and oxygen atoms, Butler explained. This enables bacteria, p
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Contact: Amber Jones
aljones@nsf.gov
703-292-80703
National Science Foundation
26-Sep-2001