A survey of Fe-isotope fractionation in the marine biogeochemical cycle

• Applicant: Professor Dr. Michael Staubwasser, since 7/2007
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2005 to 2009
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 14926700

Sources of soluble Fe to the ocean are poorly quantified and the marine biogeochemical cycle of Fe is poorly understood despite the importance of Fe for plankton production and the global carbon cycle. We propose to use the novel Fe isotope system to characterise this cycle. This is now possible because Fe isotopes fractionate in a characteristic way during many of the principal biogeochemical processes. Our previous study of sedimentary reactive Fe shows a systematic isotopic trend during early marine diagenesis and suggests that the dissolved Fe escaping back into the sea has a unique and very light isotopic composition. In the simple case of two fluxes, continental Fe and diagenetically modified Fe, the isotopic composition of seawater should reflect the respective mixing proportions. In addition, the Fe isotopic composition of process reactant and product depends on the completeness of a given reaction and may therefore indicate to what extent a particular biogeochemical process takes place. We seek to investigate marine Fe isotope fractionation in the full marine biogeochemical cycle of Fe. Much of the study will be done in the Baltic Sea, which comprises all principal aspects of the marine Fe cycle and is dominated by only two sources of dissolved Fe. The high Fe load of the Baltic Sea will keep sample sizes manageable and support method development. Fe isotope fractionation will be investigated during estuarine mixing, marine particle formation and marine diagenesis and in the water column with the aim to develop a toolbox applicable to the open ocean.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Professor Dr. Friedhelm von Blanckenburg, until 7/2007