One internship position focusing on the effects of predation and vulnerability of freshwater communities to climate change is available at the RECOVER laboratory in Aix-en-Provence (France). The student will work under the supervision of Marine SAVARIS, Arnaud SENTIS and Martin DAUFRESNE.
Topic:
Predation is a major force in shaping the structure and functioning of freshwater ecosystems through top-down control of prey populations. The strength of predator-prey interactions is temperature-dependent and climate change may therefore alter trophic interactions and cascades through aquatic food webs. Because predators differ in their thermal tolerance, heatwaves may remove thermally sensitive predators while allowing more tolerant predators to persist. The loss of predator may release prey from top-down control, increasing their abundance and cascading effects towards lower trophic levels. By contrast, the persistence of a thermally tolerant predator may maintain predation pressure throughout the community, resulting in contrasting community structure and ecosystem functioning. Understanding how predator thermal sensitivity shapes community responses to warming through contrasting trophic cascades is key to predicting changes in aquatic community dynamics.
Objective:
The aim of this internship is to investigate how predator thermal tolerance shapes freshwater communities during heatwaves and whether heatwaves shift the balance between top-down and bottom-up control.
Tasks:
The intern will:
• Measure the upper thermal limits (CTmax) of selected species representing different trophic levels (fish, macroinvertebrates, zooplankton, phytoplankton).
• Conduct a mesocosm experiment including species for which CTmax has been measured, and apply an experiment with three predation treatments (predator-free control, native predator, non-native predator) exposed to two successive heatwaves.
• Sample the mesocosms to assess changes in the relative abundance, biomass and composition of species before, during, and after the heat wave.
• Analyze the data (R) and interpret community- and ecosystem-level responses in relation to predator identity
• Write a scientific report summarizing the findings.
Candidate competences:
We are seeking a motivated student with a strong interest in experimental ecology, climate change biology, and ecophysiology. Experience or coursework in laboratory or mesocosm experiments, aquatic ectotherm biology, ecological data analysis, statistics (R), and/or food web ecology would be highly valued.
Practical information:
Starting date (flexible): February 2027 Duration: 6 months Location: INRAE, RECOVER laboratory, 3275 route Cézanne, 13182 Aix-en-Provence, France Main advisors: Marine Savaris, Arnaud Sentis and Martin Daufresne
Application:
Deadline for applications: November 8, 2026. Please send your CV and a motivation letter (1 page maximum, in French or English) to:
marine.savaris@inrae.fr, arnaud.sentis@inrae.fr, martin.daufresne@inrae.fr, Informal enquiries are welcome – please contact us by email in French or English.
Key-words:
climate change, heatwaves, predator effects, trophic cascades, thermal tolerance, food webs, trophic ecology, freshwater lakes
References:
Desforges, J.E., Birnie‐Gauvin, K., Jutfelt, F., Gilmour, K.M., Eliason, E.J., Dressler, T.L. et al. (2023). The ecological relevance of critical thermal maxima methodology for fishes. J. Fish Biol., 102, 1000-1016.
He, H., Jin, H., Jeppesen, E., Li, K., Liu, Z., & Zhang, Y. (2018). Fish-mediated plankton responses to increased temperature in subtropical aquatic mesocosm ecosystems: Implications for lake management. Water Research, 144, 304-311.
O’Gorman, E. J., Zhao, L., Kordas, R. L., Dudgeon, S., & Woodward, G. (2023). Warming indirectly simplifies food webs through effects on apex predators. Nature Ecology & Evolution, 7(12), 1983-1992.
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