I have a strong interest in the research field of paleo-limnology and stable isotope biogeochemistry. In my PhD project, I will ground-truth a new proxy for paleo-limnological studies: the diatom-bound nitrogen (N) isotope proxy.
First, I will investigate whether this N in the diatom frustule undergoes isotopic fractionation during diagenesis (degradation) processes. For this purpose, I will perform isotopic analyses of the N bound to subfossil diatoms in sediment traps, surface sediments, and downcore sediment materials from a varved lake in Sweden (Lake Nylandssjön), as well as degradation experiments using diatom cultures.
Second, I will investigate whether this proxy can be used to determine the past N sources of lakes (natural or anthropogenic), and to reconstruct the past environmental conditions of these lakes and their watershed. Thus, I will retrieve sediment cores in lakes and measure the δ15N of the diatom-bound N. Finally, I will compare the data obtained with existing data on these lakes (monitoring data, paleoecological data) in order to evaluate the relevance of this new proxy for paleo-limnological reconstructions.
This work combined with that of Saeed Ebrahimnezhad will provide a comprehensive knowledge of the diatom-bound N isotope proxy, and thus allows its use in paleo-ecological studies in both lacustrine and marine environments.
Jules Millet
Biogeochemistry / University Basel
Bernoullistrasse 30
CH-4056 Basel
Tel. +41 (0)61 207 36 29
email: jules.millet-at-unibas.ch
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