Marine barite accumulated in deep-sea sediments is widely used for paleoclimatere constructions. However, the mechanisms that drive barite formation are still poorly known. In this study, I propose to investigate the relationship between barite precipitation and the decay of organic matter by combining approaches at different scales. First, the spring phytoplankton bloom from the Scottish Sea Loch (Scotland) will be monitored over time using sediment traps for collecting the particulate matter. Special attention will be given to record the possible Ba depletion in seawater at the end of the spring bloom as has been reported by Stecher and Kogut (1999), while during the post-bloom period, I will focus on studying the relationship between the release of labile particulate Ba following the decay of labile organic matter and barite precipitation. In vitro experiments will also help understanding the prerequisites necessary for barite formation. Finally, the study of a transect along a productivity gradient in the North Pacific (sediment traps, large volume in situ pumps) will allow to investigate barite formation within an open ocean site, thus constituting a good reference for comparing the results obtained in the in situ (Loch) and in vitro experiments.
These investigations are designed to bring insight on the mechanisms of barite formation within the water column. For a researcher career, I believe that a PhD degree needs to be completed by further investigation that can expand ones skills and area of action. I would like to dissect further the mechanisms (still unknown) that drive barite formation. I would like to gain further experience in field experiments conducted in oceanography (sampling using sediment traps, in situ pumps ), in in vitro experiments, and in the use of the ICP/MS that constitutes the most accurate technique for trace elements analysis. The experience I acquired at the LSCE lnstitute (France) and at WHOI (USA) will be useful to successfully conduct this work. I will join the Department of Geology and Geophysics at the university of Edinburgh whose scientific contribution in(paleo)oceanography is well established among the international community. In addition, I will have the opportunity to interact with other groups with recognised expertise in marine geochemistry. In summary, this is an exciting project of research and the gained experience will certainly help me to attract national and/or international funding to develop my own program of research and to establish a research team.