Molecular limitation on the oceanic CO2 pump: The chelation and bioavailability of iron in surface seawater

2015 New Investigator Award

Award Period: 2015-2017

The aim of this project is to elucidate the chemical structures and the biological origins of strong iron-complexing molecules that bind the bulk of dissolved iron in surface seawater. This is important because complexation by organic compounds controls iron bioavailability and, in turn, iron bioavailability limits primary production in the oceans. The current lack of knowledge of the chemical identity of iron-binding compounds makes it impossible to unravel the biogeochemical controls on iron bioavailability. It also precludes a quantitative understanding of the effects of iron limitation on productivity and carbon sequestration, as well as insights into how these aspects may change as the surface ocean warms and acidifies due to anthropogenic CO2 emissions.

The reason why the nature of iron-complexing agents in seawater is still unknown is fundamentally analytical: How does one identify unknown organic compounds present at 10-12-10-9 M in a high salt solution containing 10-5-10-3 M organic carbon? During the past two years, this project has resulted in the development of a method for measuring metal-complexing agents in seawater. This method takes advantage of the analytical power of ultra-high-performance liquid chromatography (UPLC) coupled to high-resolution Orbitrap-based mass spectrometers. The results will give a first-order understanding of the range of compounds of interest and their likely sources in the oceans.

Educational Impacts

A module in “Chemical Biology II” (CHM 541/QCB 541) will be devoted to the biological production of iron-complexing molecules. The biochemical mechanisms in assembling these often complex molecules will be presented. In addition, undergraduate interns will be involved in the proposed research, which should foster interesting junior projects and senior theses.

Participating Department


Assistant Professor of Chemistry
Oliver Baars
Associate Research Scholar, Department of Geosciences

Mohammad R. Seyedsayamdost, Assistant Professor of Chemistry

Oliver Baars, Associate Research Scholar, Department of Geosciences


Graduate Students

  • Yihan Wu, CHEM