The Biogeochemistry of Dissolved Iron-ligands in Marine Cyanobacteria and Seawater

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Micronutrient trace metals, such as iron and cobalt, are critical to all life on earth, and their availability in the environment can regulate the primary productivity in a region. In the ocean, up to 99.9% of dissolved iron, and to a lesser extent cobalt, are bound by strong organic binding molecules, known as ligands which control what fraction of these metals is available to organisms. To understand carbon and nutrient cycling in many remote areas of the ocean where trace metals limit primary production, it is important to understand the distribution and cycling of ligands. In this study, a researcher at the Woods Hole Oceanographic Institute will use novel techniques to assess the diversity and composition of natural iron and cobalt binding ligands in laboratory cultures of the globally abundant marine cyanobacteria Prochlorococcus and in seawater samples from the South Pacific Subtropical Gyre. This study will add significantly to the interpretation of iron and cobalt availability, and help to link measurements of elemental metal distributions, ligand concentrations and binding strengths, and assessments of the microbial community. Broader Impacts: Results from the project would be incorporated into graduate level organic geochemistry classes taught by the proponent and be made publically available through the Massachusetts Institute of Technology and Woods Hole Oceanographic Institution websites. One graduate student would be supported and trained as part of this project. It is anticipated that undergraduate students would also have the opportunity to participate in the study during the summer months and learn about organic geochemistry, microbial biogeochemistry, and modeling.