2nd year PhD student
Tél. : *************
E-mail : nicolas.bienville@lsce.ipsl.fr
Research
The isotopic composition of atmospheric oxygen (δ17O and δ18O of air O2) is an important tool in the study of paleoclimate from ice cores because it provides information on the past intensity of the low-latitude hydrological cycle and global biospheric productivity on the same time scale as climate variations recorded in polar ice. However, the link between oxygen isotopic composition and the low-latitude hydrological cycle on the one hand and global biospheric productivity on the other is currently only performed at the qualitative level and not quantitatively. Indeed, the δ18O of O2 and the δ17O of O2 are complex tracers that involve the different biological processes of consumption (respiration, photorespiration) and production of O2 (photosynthesis). In order to quantitatively interpret these tracers and improve the dating of ice cores with the δ18O of O2, it is necessary to know the isotopic fractionations associated with the different biological processes. To this end, we have developed two first prototypes of multiplexed, controlled and instrumented biological chambers to study oxygen fractionation in biological processes implemented by terrestrial plant species (set of 6 closed-circuit ‘terrariums’ chambers using the Microcosmes platform of the Ecotron Montpellier) and by aquatic species (set of 6 closed aquariums using the CEREEP Ecotron platform). The measurement of the isotopic composition of oxygen is carried out with an innovative optical spectroscopy instrument allowing the continuous measurement of the concentration and isotopic composition of oxygen. The aim of this thesis is to exploit and valorize the recently developed multiplexed and instrumented biological chamber systems to quantify the oxygen isotopic fractionation associated with biological processes for a wide range of different plant species and for different climatic conditions in order to use these coefficients to reconstruct, in particular, the variations of biological productivity fluxes (photosynthesis) in the past. The planned work program is described below. It involves skills in ecophysiology, isotope geochemistry and instrumentation and relies on complementary collaborations and expertise at LSCE (isotope geochemistry, climate, instrumentation) and in ECOTRONS (ecophysiology, instrumentation)
Publications
Financing
- Scholarship grant from CNRS : 80PRIME2023
Outreach
Finalist of Paris Saclay competition MT180
Teaching
- TD Climate Sciences – CentraleSupélec 2024
- TD Planetary boundaries and biodiversity – CentraleSupélec 2025