Bridging Scales In Ecotoxicology: From Individual Responses To Community Dynamics In Soil Microarthropods Exposed To Pesticides

Ecotoxicology is a multidisciplinary field that examines the effects of harmful substances on organisms in various environmental compartments, providing essential data for environmental risk assessments and regulations. A key challenge is linking biological responses from molecular to community levels. This thesis explores the sensitivity of soil microarthropods, particularly Collembola, to pesticide exposure, focusing on the mechanistic aspects of toxicity. Research began by evaluating pesticide effects on Folsomia candida through standard toxicity tests, which showed that younger juveniles were more sensitive to insecticides, emphasizing the protective nature of current testing methodologies. Subsequent chapters focused on teflubenzuron, an insecticide affecting chitin synthesis, and its impact on reproductive output. Lipidomics analysis revealed early effects of low concentrations of teflubenzuron, indicating a resource allocation shift. The study extended to the Collembola species Sinella curviseta and Ceratophysella denticulata, demonstrating inter-species variability in susceptibility to teflubenzuron. Metabolite changes linked to chitin synthesis were significantly affected, with a decrease in trehalose levels indicating a stress response. Although S. curviseta showed resilience in reproduction and survival, metabolomic data revealed sensitivity to low internal concentrations of teflubenzuron. F. candida showed higher susceptibility to teflubenzuron, linked to species-specific traits related to vertical stratification in the soil profile, resulting in higher insecticide bioaccumulation levels in soil-dwelling species. To assess more realistic scenarios, teflubenzuron's effects were studied in a soil microcosm with four Collembola species. The insecticide directly influenced the community by reducing the survival and reproduction of Collembola and indirectly by interfering in competition for resources. research on soil microarthropods (Collembola and Acari) examined effects of clopyralid, zeta-cypermethrin, and pyraclostrobin (in commercial formulations), applied individually and sequentially in both field and in laboratory settings. Despite short-term effects observed in field tests, there were no long-term impacts on Collembola populations. In conclusion, this thesis presents a multiscale investigation of soil microarthropod sensitivity to pesticides, focusing on mechanistic insights into Collembola sensitivity across biological levels. It examines the effects of pesticides at the individual level in different species of Collembola, with distinct morphological, ecological, behavioral and physiological traits. Furthermore, it highlights the use of metabolomics in understanding toxicological responses and extends findings to mesocosm and field studies, assessing ecological relevance at community level.