Studying the toxicity of pesticides on soil microbial networks

In soil ecosystems, microorganisms exist in complex and diverse communities where microbial taxa are linked through different types of interactions. Therefore, pesticide application will not only directly affect certain microbial taxa, but will also have indirect effects throughout the community mediated through these interactions. These indirect effects may also influence ecosystem functions and should be accounted for in pesticide risk assessment. My PhD aims to i) investigate the effect of pesticide application at the community level, ii) identify taxa whose response to pesticides may impact soil functions, and iii) distinguish direct and indirect effects mediated through biotic interactions between taxa. In order to unravel these indirect effects, we fragmented soil microbial communities by filtration and compared the response to pesticide application between different fractions. This work sheds light on ecological interactions between microbial taxa in soil and could provide a novel approach for the development of procedures to assess pesticide toxicity at the ecosystem level.


Fig. 1: We have found that indirect effects are widespread throughout the microbial community. Fragmentation augments the community's response to pesticide application, especially for bacterial taxa.

My thesis investigates to what extent the interactions between microorganisms affects a soil microbial community’s response to pesticide application.

Experiment in pictures

Fig. 2: Harvesting the soil to be used in my first experiment from the Sayens site in Bretenière, France.
Fig. 3: Me with my 200 soil microcosms using fragmentation to assess the effect of pesticides on soil microbial communities.

Fig. 4: Extracting DNA from the soil samples from my first and second experiments.
Fig. 5: Extracting inorganic nitrogen from the soil samples to assess how nitrogen cycling is affected by pesticide application.

All you need is one

Fig. 6: This one vial contains DNA from 300 samples and two experiments! The gene for 16S rRNA has been amplified, tagged according to sample, and will be sequenced in order to investigate the effect of pesticide application on the soil prokaryotic community.