Role of complex trophic interactions in biogeochemical cycles


In the ocean, trophic interactions between individuals are still mainly represented in a predator-prey pattern. However, meta-analyses of taxonomic co-occurrences, made possible by advances in molecular biology, suggest that many planktonic organisms are involved in complex interactions ranging from facultative predation to symbiosis to mutualism. While these relationships appear to be the rule rather than the exception in the ocean, research efforts are focused on a few emblematic examples. In CHIBIDO, we are trying to identify new interactions and are particularly interested in mixotrophic organisms (both phototrophic and phagotrophic), the trophic mode of the majority of dinoflagellates, and in diazotrophs that often live in symbiosis with other organisms. To better understand the role of trophic interactions on biogeochemical cycles (especially nitrogen and carbon), it is necessary to couple tools.

The team is internationally recognised for its expertise in the use of 13 C and 15 N stable isotopes to quantify oceanic fluxes. In recent years, it has coupled this approach with new tools (e.g. nanoSIMS or flow cytometry sorting) that make it possible to visualise and quantify fluxes between the environment and organisms and/or between organisms.