The Ecotox team gathers different disciplines belonging to environmental sciences: pedology, physico-chemistry, microbial ecology, biogeochemistry, biology and ecology. Before joining ECOSYS in 2015, it was created in 2006 as a research unit named Pessac for “Physicochemistry and Ecostoxicology of Contaminated SoilS of Agrosystems” by merging the Soil Science unit from Versailles (Environment and Agronomy INRA division) and the “Xénobiotiques et Environnement” team from the “Phytopharmacie et Médiateurs Chimiques” unit (Plant Health and Environment INRA division). The team rules the technical plateaux of ECOSYS in inorganic analytical chemistry and the soil fauna breeding in biology, the long-term field experiment “42 parcelles” located in Versailles since 1936 (Fig. 17), and hosts the platform Biochem-Env also opened for external use (ANAEE-France project) (Appendix 2). The research activities of the Ecotox team are part of the master plans of the EA and SPE divisions. Its issue is threefold: evaluate the toxicity of contaminants for soil living organisms, evaluate and prevent the risks of contaminants for the environment, and evaluate the sustainability of soil ecosystems to maintain their functions under anthropic pressures.
Studies are focused on soils of agroecosystems taking into account the contaminant inputs originating either from land management or surrounding human activities. Indeed, the short or long-term impacts of anthropic activities modify the composition and properties of soils, thus the dynamics and localization of contaminants and then the exposition of organisms.
The context of our studies is mainly diffuse organic and /or mineral contaminations where total contents of contaminants in agricultural soils are often at low doses corresponding to sub-lethal effects for organisms, but they are generally chronically or recurrently spread on soils.
This implies to take into account the presence of mixture of contaminants but also multiple expositions for organisms. The studied organisms play part to soil functions contributing to ecosystem services, with a focus on soil microorganisms, annelids oligochaetes and carabidees. The spatial scale of our studies covers the soil constituents and their organization resulting from pedogenetic processes and/or man’s actions (what we can call the pedologic traits), to the scale of the soil profile, the parcel and those of landscape. Depending on the scientific questions or the socio- environmental issues to be addressed, the contaminants are pesticides or antibiotic residues and/or mineral trace elements. In the continuation of the Pessac project before ECOSYS (2008-2015), researches in the Ecotox team until 2018 aimed at linking the fate of the contaminants in the soil to both their effect on soil organisms and to the modifications in soil functioning This was mainly done using the concept of bioavailability to link chemical to biological approaches (Fig. 18). Results are used to discuss and validate soil ecotoxicity indicators.
Compared to classical and normative approaches of ecotoxicology, our approach was in rupture and based on innovative points of view, meaning: i) working with networks of experimental sites exhibiting a gradient of in situ contamination instead of spiking substrates ; ii) exploiting the natural variability of such soil panels instead of working with artificial substrates iii) involving mixture of contaminants rather than working one by one contaminant ; iv) discussing the results on the basis of bioavailability instead of in terms of total contents in soil contaminants ; v) developing tests using biological parameters in relation with routes of contaminant exposition and relevant realistic environmental doses instead of high doses ; vi) integrating the different levels of biological organization using a combination of representative soil organisms instead of using a unique and standardized biological model ; vii) considering soil organisms not only as targets of contamination but also as actors with a role in the fate of the contamination to tackle interactions ; and finally viii) go beyond the taxonomical approaches by developing trait based approaches in order to go to functional outputs.
Our research questions were directed towards either understanding processes or integration of processes and were distributed in two research lines: dynamic of the interactions between contaminants and soil organisms, and contribution of ecotoxicology to the multi-criteria evaluation of the soil functions. These two research lines, however, did not establish in an actual way structures of animation, - the animation within the team having worked by project-, but they grouped the set of the questions approached during the last five-year related to 2 components of the risk assessment: 1) the organism exposure assessment, and 2) the evaluation of the effects of the contaminants on the organisms and their functions. The studies were realized in complement and in synergy with the works developed in the Soil team concerning the fate of contaminants and were part of the ECOSYS transversal axis “regulating of environmental compartment quality”.
➢ The studies on the exposure assessment concerned the research line (RL) 1 with the purpose to feed the research line 2, and had main tackled issues to both enhance knowledge of the biophysico-chemical determinism of the fate of contaminants in soils, and to confront causal theory of bioavailability to observations. Linking the presence of contaminants in soils to their effects on soil organisms was done looking for the best indicators of exposure or effects, also requiring the identification of the confounding factors influencing these indicators. The tackled issue concerning bioavailability included quantification of contaminant bioaccumulation in soil organisms to tentatively establish relationship with their availability. Several ways to take into account bioavailable pools of contaminants and not only their total contents were also explored to quantify the exposition. This involved to take into account the chemical speciation of trace elements, and the transformation of organic products towards metabolites by photo-activation or biochemical reactions.
➢ The studies on the evaluation of the effects of the contaminants on the organisms and their functions concerned both experimental approaches to better understand mechanisms or processes, and modeling approaches to predict the effect of contaminants at different biological scales from infra-individual, to individual, population or community. These works concerned more specifically the research line (RL) 2 building on the results produced in the research line 1. The main tackled issues were assessing the differences of sensitivity to contaminants between soil organisms within communities, characterizing soil disfunctioning in the presence of contaminants, identifying mechanisms contributing to resilience in contaminated soils (tolerance acquisition, functional redundancy, or recolonization…), and finally assessing the impact of the landscape structure on the exposition of non-target soil organism to contaminants.
In the following, we review the main results linked to our research projects, with the keywords describing the researches led in the last five-year term: ecotoxicology, soil, relationship fate-effect, bioavailability, exposition, indicators, pedologic traits, edaphic organisms, pesticides, metallic trace elements, antibiotics.
Two major evolutions in our approaches can be highlighted over the past period: the introduction of more ecology in ecotoxicology, and the will to integer several levels of complexity to better understand the relationship between the fate of contaminants and their effects on soil functions. The recent recruitment of a young researcher (Colette Bertrand) with the new objective to focus on landscape ecotoxicology is the product of a lot of thinking with the other teams of ECOSYS in order to integrate this complexity at the different scales: biological, time and space. If experimentation is still the skills of the Ecotox team, modeling is a way being invested and will still require efforts in recruitment to go further on collaborations on our biological models. The team has also invested in owning its biological models which is time consuming and require specific skills precious to keep on the long term. The hosting of the Biochem-Env platform, that has developed this last few years and is dedicated to the biochemical characterization of the environment, can be an opportunity to develop specific indicators turned to our specific questions.