Aquatic ecosystems are subject to multiple anthropogenic pressures mainly land use, hydromorphological modifications, enrichments in nutrients and organic matter and, chemical pollution. Nowadays, studying the links between pressures and the responses of communities takes rarely into account the effect of chemical contamination at large scale and also the fraction of bioavailable contamination and toxicity. Active biomonitoring, based on caging of control organisms in aquatic environments, has recently enabled the evaluation and the quantification of bioavailable contamination and toxicity in numerous sites distributed nationally. These new datasets offered us the opportunity to evaluate the role and the effect of chemical toxic contamination on the known relationships between pressures and ecological impacts. The thesis work focused on four objectives: the construction of a conceptual framework to quantify the effect of pressures on bioavailable contamination for metals and organic pollutants and, the evaluation of the impact of chemical toxicity on the known relationships between stressors and the ecological status and finally, the identification of associations between chemical toxicity and the modalities of biological traits of communities in a multi-pressure context. With structural equation modeling, we determined the dominant pressures on bioavailable contamination at the national scale. Metallic bioavailable contamination increased with land use, industry density, wastewater treatment plant density, pressures on the stream hydromorphological functioning and bioavailability factors (descending order) and, it decreased with the increase of riverside vegetation. The dominant pressures on polycyclic aromatic hydrocarbons (PAHs) are mainly punctual sources and vectors of contamination, unlike polychlorinated biphenyls (PCBs) with dominant diffuse sources. With bivariate and multivariate analyses, we evaluated that chemical toxicity had an aggravating role on certain relationships between the ecological status and stressors (nutrients and organic matter and, hydromorphology). With a co-inertia analysis, we identified the associations of stressors, including chemical toxicity, with biological traits of communities. The stressors were associated to modalities of resistance like ovoviviparity. Finally, all the datasets and these approaches enabled a presentation of a pressure-impact framework with active biomonitoring, that is useful for understanding the dominant pressures in order to propose management of aquatic ecosystems.

Funding

100% Irstea

Valorisation

Oral Communication “Multi-Stressor’s Effects on Contamination and Toxicity in French Streams Using Ecotoxicological Indicators based on Caged Gammarids”, “Symposium for European Freshwater Sciences (SEFS)”, Session “Ecotoxicology and stress responses”, Croatie, (30 Juin– 5 Juillet 2019)

References

• Besse, J. P., Coquery, M., Lopes, C., Chaumot, A., Budzinski, H., Labadie, P., & Geffard, O. (2013). Caged Gammarus fossarum (Crustacea) as a robust tool for the characterization of bioavailable contamination levels in continental waters: towards the determination of threshold values. Water Res, 47(2), 650-660. doi:10.1016/j.watres.2012.10.024
• Villeneuve, B., Piffady, J., Valette, L., Souchon, Y., & Usseglio-Polatera, P. (2018). Direct and indirect effects of multiple stressors on stream invertebrates across watershed, reach and site scales: A structural equation modelling better informing on hydromorphological impacts. Science of the Total Environment, 612, 660-671. doi:10.1016/j.scitotenv.2017.08.197

Cite the thesis

Noëlle Sarkis. Intégration des indicateurs écotoxicologiques dans les modèles multi-échelles et multi-pressions pour améliorer la compréhension des liens pressions-impacts à l’échelle des bassins. Ecologie, Environnement. Université de Lyon, 2021. Français. ⟨NNT : 2021LYSE1279⟩. ⟨tel-03887722⟩

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