Ecotoxicology

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 INRAE division) and the “Xénobiotiques et Environnement” team from the “Phytopharmacie et Médiateurs Chimiques” unit (Plant Health and Environment INRAE 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 AgroEcoSystem 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.

• RL1. Exposure assessment

• RL2. Evaluation of the effects of the contaminants on the organisms and their functions

Conclusions

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.

Scientific stategy and project

The project of the Ecotoxicoloy team aims to be realistic while being ambitious, by taking into account the following facts:

1)     The previous five-year term researches allowed us to move forward on numerous issues in ecotoxicology while introducing new perspectives of questionings. The team is now mature to propose new keys for answering scientific questions linked to ecotoxicology and to propose in continuity a plan to go further on our previous project.

2)     But we will have to deal with several departures in mobility of researchers and technicians, actual or in preparation. This will perturb the intended synergy of skills originally thought when creating the Pessac unit in 2006 and that was effective within the Ecotox team the last few years. Indeed, the intention was to group skills of pedologists, chemists, biochemists, microbiologists, ecologists, and ecotoxicologists to tackle soil ecotoxicological questions. The successive or scheduled departures, however, force us to redefine our questions taking into account the potential loss of skills, unless these will not be renewed.

3)     Saying that, the context could be found, however, as favorable for a renewal of our scientific questions, with regard to the Saclay project. Indeed, beyond a physical moving, the related scientific project carry us towards a dynamic of scientific communities where the ecotoxicology has a place to be taken. Furthermore, the next merging of INRA-IRSTEA will also bring to us a well-structured community in aquatic ecotoxicology that justifies even more to keep a nice construction in soil ecotoxicology

With that in mind, we aimed at developing a systemic approach of the effects of contaminants on the environment following our former approach of studying the relationship fate-effects (Fig. 28). We propose to go further on towards functions driven by the soil organisms and integer the long term (introducing the notions of adaptation tolerance and resilience), and to take into account the externalities that are the plants, the climate and the features of the landscape thus completing our previous scheme.

Two research lines were identified to structure our questions: 1) the soil as a regulator of the exposition to contaminants in agroecosystems and 2) from ecotoxicology to agro-ecotoxicology; from which we sorted four flagships corresponding to our engaged projects in the short term:

1)     The exposome quantification in order to integrate the sum of the environmental expositions during the life of an organism, such a notion being enable us to approach the relationship between environment and health,

2)     A better knowledge of the mixture effects of contaminants to increase our ability to predict ecotoxicity in conditions close to reality where soils are multicontaminated. If methodology to address mixture effects is available, yet some knowledge gaps like the co-exposure patterns need to be filled particularly in the soil environment.

3)     The importance of the interactions between organisms to better understand the impacts of contaminants on the soil functions.

4)     The evaluation of the ecosystem capacity for resilience and to sustain their functions by studying attenuation, adaptation or redundancy process.

These four topics concern the biological scales from individual (or infra-individual) to populations or communities. The context of the research questions is the global change (including land use changes and climate changes), and covers different spatial scales of studies, from local ones to those of landscape.

The scientific challenge of the research line 1 “the soil as a regulator of the exposition to contaminants in agroecosystems” and the corresponding flagships 1 and 2 aims at understanding and modeling the complex influences of the soil matrix on the exposition on organisms. We intend to specifically tackle the issue of the ambivalent role of organic matter, either native or added organic matter. Indeed, organic matter is both a ligand for contaminants and a food source for organisms thus acting at the same time as ‘poison and antidote’. To address the mixture effects of contaminants, we have to i) assess if and how combined exposure occur in field conditions as well as ii) define appropriate ecotoxicological indicators to report combined effects when various contaminants have different modes of actions and iii) explore the possibility of integrating the bioavailable pools of contaminants or the various ways of exposure in the predictive modeling of the mixture effects. One main output is to precise if the knowledge on individual contaminants can be enough useful to predict the impacts on soil organisms or on soil functions when in mixtures with other contaminants, through either in situ, ex situ, or in silico studies. The approaches used will imply coupling ex situ experiments with modeling and the use of « organism centered » bio-essays mimicking soil ecological functions. Typology in silico and predictive modeling as challenges will required to reinforce collaborations with toxicologists and modelers. The ongoing projects allowing us to go further on these researches are AFES, BIOMENC, DYNAMIQUES, GRACE, MAGIC, CONNEXION.

The scientific challenge of the research line 2 “from ecotoxicology to agro-ecotoxicology” and the corresponding flagships 3 and 4 aims at answering the questions on the long-term impacts of the contaminants on the organisms and their functions, with the methodological challenge to evaluate the consequences at sublethal doses, and while integrating the notion of resilience in such studies. We aim to focus on the choice of the indicators. Indeed, we face to a change in paradigm from the usual « toxic effect to assess », to the findings of « marker of adaptative processes». This will involve integrating proxy at the individual scales to predict effects at the population level. This will also include hierarchizing processes involved in the community responses on the long term, between functional redundancy, recolonization of the areas, or adaptation. One approach will consist in looking for indicators taken into account perturbations in the interaction networks between edaphic organisms. This will allow us to treat also the consequences of a loss in biodiversity on the resilience of the ecosystems to other stress, and in particular those linked to climate changes, and thus finally to deal with multi-stress approaches. Finally, the spatial integration of the processes aims to help us understanding how the landscape features influence the fate and the impact of contaminants on non-target organisms, but also which components of the landscape could be used to improve the resilience of the organism functioning at the community level towards contaminants. The ongoing projects allowing us to go further on these researches are DYNAMIQUES, GRACE, MAGIC, PING, research project of Colette Bertrand newly recruited, CONNEXION, ADSORB.

Furthermore, our discussions and actual reflections go to apply our ecotoxicological approaches to questions about the continuum soil-water-sediment. One of the objectives is to assess if a soil threshold that we can actually define is able to effectively protect the water and sediment qualities, but several questions  around the one Health concept particularly in the context of Saclay moving can be addressed when looking at the continuum soil-water-sediment. The ongoing project linking to this is the last Life project ADSORB.

Contribution of Ecotoxicology to the structuring themes of ECOSYS (in yellow) through interactions with the Soil and/or Eco&Phy teams