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24, chemin de Borde Rouge -Auzeville - CS52627 31326 Castanet Tolosan cedex - France

Last update: May 2021




Centre Alpin sur les Réseaux Trophiques et Ecosystèmes Lacustre

PhD position in Biodiversity, Ecology and Environment

CARRTEL laboratory, INRAE, University of Savoie Mont Blanc (USMB)

19 February 2023

PhD position in Biodiversity, Ecology and Environment
Title: Characterization of nitrogen and phosphorus cycling in alpine lakes using stable isotopes

Project description: 

Context. The observed global greening of oligotrophic mountain lakes defies current knowledge on lake eutrophication processes1. Greening is an increased algal production that occurs mainly in the littoral (near shore) and in the benthic zones, despite overall low nutrient availability in the water column. One of the main hypotheses to explain such greening is that mountain lakes currently undergo changing nutrient sources, cycling and/or stoichiometry in response to global change. Solving this puzzle requires to identify and understand key biogeochemical processes driving mountain lake nutrient status. Most notably, the biogeochemical cycling of nitrogen (N) and phosphorus (P) in mountain lakes needs to be assessed: when present in excess, these nutrients are responsible for excessive plant and algal growth in freshwaters2 and N:P stoichiometry dictates the taxonomic composition of lake biota3. 

Objectives and methods. The main objective is to investigate N and P cycling in mountain lakes of the French Alps undergoing different anthropogenic (e.g., tourism, huts, pastoralism) and environmental (e.g., glacier melt, permafrost thaw) pressures. To achieve this objective, the candidate will study the isotopic composition (15N, 18O and Δ17O) of nitrate (NO3-) and ammonium (NH4+)4, which are the most readily available N forms to sustain primary productivity, as well as the isotopic composition (18O) of phosphate (PO43-)5, the main dissolved form of P in aquatic systems. Isotopic analyses will be conducted on samples from the selected lakes’ inlets, water column, biota (plankton, biofilms, macrophytes) and sediments. These measurements will be coupled to ancillary parameters (e.g., pH, temperature, conductivity, dissolved oxygen levels, chlorophyll-a, turbidity) and laboratory experiments (e.g., sediments incubation). 

More specifically, the candidate will: 

  • Plan, organize and lead several field campaigns to sample the selected alpine lakes during key periods for N and P biogeochemical cycles (e.g., snowmelt (early summer), peak biomass (late summer), deoxygenation (winter)). 
  • Coordinate and participate in laboratory work, including chemical and isotopic analyses on samples from a large array of environmental matrices (e.g., water, sediments, ice, plankton, biofilms, macrophytes) as well as sediments incubation experiments. 
  • Lead statistical analyses and interpretation work on the collected results. 
  • Disseminate novel findings through peer-reviewed scientific articles and participate in scientific conferences. 

Location and collaborations. The project will take place at the CARRTEL laboratory in Savoie, France ( CARRTEL is a research laboratory part of the National Institute for Research in Agriculture, Food and Environment (INRAE) and of the University of Savoie Mont Blanc (USMB). CARRTEL hosts about 40 permanent scientists dedicated to the study of lacustrine ecosystems and their watersheds, and is based out of Thonon and Bourget Technolac. The candidate will be based in Bourget Technolac (bikeable distance from the city of Chambéry). In addition to CARRTEL where the candidate will perform most of its work, collaboration will take place with scientists at IGE and LECA in Grenoble, France, at ETH Zurich in Zurich, Switzerland, and with various French stakeholders including National Parks and Conservancy Funds. 

Timeline: The candidate is expected to start in October 2023 for a duration of 3 years. 

Requirements: Motivated candidates should hold a Master’s Degree in Ecology, Environmental Sciences, Analytical Chemistry, Planetary Sciences or equivalent. Candidates should have one or multiple experiences working in the field, preferably in alpine settings, and in laboratory. Previous experience working with stables isotopes is not required but would be a plus. Extreme attention to details, autonomy, ability to work under pressure and strong interpersonal skills are necessary for this position. Excellent English communication skills, including reading, speaking, and writing are required. Knowledge of French or a willingness to learn is important. A strong interest in environmental issues concerning alpine ecosystems, a good command of a programming language and statistical tools, and skiing/mountaineering skills would be additional assets. 

Contact to apply: The candidates should apply before June 1st 2023 by sending a single PDF file containing a resume, cover letter, Master’s degree grades and diploma, and contact information for potential referees to both Ilann Bourgeois ( and Jean-Christophe Clément ( An oral interview will be then be scheduled with a shortlist of candidates

  1. Vadeboncoeur et al. (2021) BioScience DOI: 10.1093/biosci/biab049 
  2. Conley et al. (2009) Science DOI: 10.1126/science.1167755 
  3. Lepori et al. (2014) Freshwater Biology DOI: 10.1111/fwb.12370 
  4. Kendall et al. (2007) Stable Isotopes in Ecology and Environmental Science (Ch.12), 2nd edition, Blackwell Publishing, p. 375-449. 
  5. Tamburini et al. (2012) ES&T DOI: 10.1021/es300311h