ISOMAR

Sources and Biogeochemical Cycling of Iron Isotopes in Marine Environments

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 Obiettivo del progetto (Objective)

'Iron (Fe) is now recognized as a limiting nutrient in large regions of world’s ocean and changes in the supply of Fe to the upper ocean may lead to climate change by affecting biological productivity and altering rates of carbon sequestration. However, there is a continuing debate over the sources of dissolved Fe to the global ocean. Therefore, it is difficult to predict how climate-driven changes in weathering and coastal hypoxia might impact future Fe delivery to the global ocean. In this project, the applicant aims to apply a promising new technique for measuring Fe isotopes in seawater in order to determine if oceanic Fe sources derived from benthic diagenesis or seafloor hydrothermal systems have characteristic isotope signatures that are distinct from riverine or atmospheric Fe sources. In order to test this hypothesis, the applicant will investigate four contrasted region of the world’s ocean, including (1) seafloor hydrothermal plume from the mid-Atlantic ridge at 5°S (2-3) oxygen minimum zones in the Pacific affected by either hydrothermal input from Loihi Seamount or shelf input from the Peru Margin and (4) Atlantic zonal section affected by variable dust deposition. This study will involve international collaborations with US and EU scientists and the results will be integrated in the context of the Geotraces and InterRidge international programs. The applicant is expecting to return in France in September 2009 to hold a 3-years term position at the European Institute of Marine Studies (IUEM) in France. By providing the necessary resources, this project will strengthen the competitiveness of the host institution in this rapidly evolving research field and will enhance the reintegration of the applicant in the EU scientific community.'

Introduzione (Teaser)

Iron (Fe) is the most important metal element for marine ecosystems since it plays a vital role in photosynthesis and the growth of phytoplankton, for example. Researchers examined how changes in the supply of Fe to the upper ocean could impact on climate change.

Descrizione progetto (Article)

The rationale is that Fe availability in the ocean can affect biological productivity and the rate of carbon sequestration. However, the sources of dissolved Fe have not been fully explored, prompting initiation of the EU-funded 'Sources and biogeochemical cycling of iron isotopes in marine environments' (ISOMAR) project.

The scientists aimed to determine if oceanic sources of Fe, like hydrothermal vents, display isotope signatures different to that of riverine or atmospheric Fe sources. Different isotope signatures may mean different chemical properties.

Team members successfully achieved their first goal, which was to develop a new method to measure Fe isotopes in seawater. In fact, the precision of their novel approach is good enough to measure isotopes in deep seawater, hydrothermal plumes and coastal areas.

Part of the project research also involved a cruise to the Loihi Seamount in Hawaii. The hydrothermal field there is an example of an environment where the biological and chemical oxidation of Fe can occur simultaneously. This makes it an ideal site to study metal sources and biogeochemical cycling.

International collaborations were also initiated to measure Fe isotopes in the Gulf of Alaska and in the Indian River Lagoon in Florida, United States. Results so far suggest that Fe in coastal seawater does have a unique isotope signature in comparison with Fe from rivers.

Initial ISOMAR research results point to Fe isotopes being valuable tracers for oceanic Fe sources. It is hoped that these efforts will help others to better assess the interplay between climate-driven changes and oceanic Fe availability.