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Nuttens A.,CNRS Interdisciplinary Laboratory for Continental Environments | Gross E.M.,CNRS Interdisciplinary Laboratory for Continental Environments
Environmental Toxicology and Chemistry | Year: 2017

Sucrose as a carbon source in axenic tests affects plant growth and physiology. The high sucrose concentration in Organisation for Economic Co-operation and Development (OECD) guideline 238 for the submerged growing aquatic plant Myriophyllum spicatum might modify pollutant effects, thus impairing environmental risk assessment. In a factorial design experiment with axenic M. spicatum exposed to 3 sucrose concentrations (no, low, and high) with or without cadmium, growth, dry matter content, content in pigments or phenolic compounds, and elemental stoichiometry of carbon (C), nitrogen (N), and phosphorus (P) were measured. The results show that sucrose is crucial for growth but can be used at lower concentrations than currently considered. Sucrose-treated plants had higher dry matter content and C content but lower contents of chlorophyll and N. Cadmium affected the content in chlorophyll, phenolic compounds, and elemental stoichiometry. Interactive effects were observed on length growth, C and N content, and the C:N and N:P molar ratios. Remarkably, cadmium led to increased shoot length at low, but not at high, sucrose concentration. This contrasting effect might result from differences in osmotic potential caused by sucrose. Overall, the results suggest a strong effect of sucrose concentration on the growth and physiology of M. spicatum and modifications of the response to cadmium. Further studies should establish the lowest sucrose level needed to account for realistic environmental risk assessment based on the axenic OECD 238. Environ Toxicol Chem 2017;36:969–975. © 2016 SETAC. © 2016 SETAC

Mondy C.P.,Eawag - Swiss Federal Institute of Aquatic Science and Technology | Usseglio-Polatera P.,CNRS Interdisciplinary Laboratory for Continental Environments
Science of the Total Environment | Year: 2013

The full accomplishment of the European Water Framework Directive objectives has required from EU members three successive steps: (i) the evaluation of their water body ecological status, (ii) the risk assessment of different anthropogenic pressure categories and (iii) the implementation of appropriate management and restoration programs.We aimed at designing an innovative retrospective ecological risk assessment (ERA) tool working for most of the French wadeable rivers in a context of multiple anthropogenic pressures (step ii). This tool, including conditional tree forest (CTF) models, was built on combinations of benthic macroinvertebrate trait-based metrics for each of sixteen anthropogenic pressure categories.For eleven pressure categories, CTF models have given good impairment risk assessment (i.e. AUC. ≥. 0.70), even at moderate risk level and in a multi-pressure context. The four other models have provided poorer but promising results (AUC. =. 0.67. ±. 0.02).Identifying the potential weight of individual anthropogenic pressures that lead to biotic assemblage impairment in streams under multiple pressure scenario, is a key step for managers to implement appropriate stream restoration programs. Simultaneously considering the whole complexity of bio-ecological adaptations within biotic assemblages subjected to human pressures provides a functional diagnostic tool both (i) ecologically relevant and (ii) efficient for ERA. © 2013 Elsevier B.V.

Parat C.,University of Pau and Pays de l'Adour | Pinheiro J.P.,CNRS Interdisciplinary Laboratory for Continental Environments
Analytica Chimica Acta | Year: 2015

This work presents the development of a new probe (ISIDORE probe) based on the hyphenation of a Donnan Membrane Technique device (DMT) to a screen-printed electrode through a flow-cell to determine the free zinc, cadmium and lead ion concentration in natural samples, such as a freshwater river. The probe displays many advantages namely: (i) the detection can be performed on-site, which avoids all problems inherent to sampling, transport and storage; (ii) the low volume of the acceptor solution implies shorter equilibration times; (ii) the electrochemical detection system allows monitoring the free ion concentration in the acceptor solution without sampling. © 2015 Elsevier B.V.

Duval J.F.L.,CNRS Interdisciplinary Laboratory for Continental Environments | Duval J.F.L.,University of Lorraine
Physical Chemistry Chemical Physics | Year: 2013

A theory is proposed for the dynamics of metal uptake by a spherical microorganism whose peripheral structure consists of a charged bioactive surface surrounded by a soft (ion-permeable) charged layer. The formalism explicitly considers the concomitant steady-state conductive diffusion transport of metals from bulk medium to the bioactive surface and the kinetics of intracellular metal internalisation described by a Michaelis-Menten mechanism. The spatial distribution of metals at the microorganism/solution interphase is derived from an explicit solution of the Nernst-Planck equation with differentiated metal diffusion coefficients inside and outside the microorganism soft surface layer. The metal concentration profile involves the interphasial electrostatic potential distribution governed by the Poisson-Boltzmann equation accounting for the dielectric permittivity gradient across the soft layer/solution interface. The resulting metal uptake flux is rationalized in terms of dimensionless metal-biosurface affinity and the ratio between limiting uptake flux and limiting conductive diffusion flux. Both parameters depend on background electrolyte concentration, microorganism soft surface composition and geometry via their connection to a Boltzmann surface term and a factor expressing the electrostatically-driven retardation or acceleration of metal diffusion. Illustrations demonstrate how metal transport dynamics impacts biouptake depending on electrolyte concentration and on the key bio-physico-chemical properties of the biointerphase. The mathematical framework is then applied to practical situations where a swarm of charged microorganisms deplete metals under steady-state transport conditions. Several depletion kinetic regimes are evaluated as a function of medium salinity and microorganism electrostatic features. Expressions of their characteristic timescales are derived and analogies with equivalent electrochemical circuits are formulated. © the Owner Societies 2013.

Zimmermann R.,Leibniz Institute of Polymer Research | Dukhin S.S.,New Jersey Institute of Technology | Werner C.,Leibniz Institute of Polymer Research | Werner C.,TU Dresden | Duval J.F.L.,CNRS Interdisciplinary Laboratory for Continental Environments
Current Opinion in Colloid and Interface Science | Year: 2013

During the past decade, much attention has been devoted to the use of electrokinetic phenomena for addressing both charging mechanism and structure of multi-responsive soft polymeric layers whose thickness may range from few tens of nanometers to several microns. In particular, major progress was achieved in the quantitative reconstruction of streaming current data collected over a wide range of physico-chemical conditions using recent theories for electrohydrodynamics of soft diffuse planar interphases. In this article, we review the basics of the methodology adopted for deciphering the mechanisms governing the charging of electric double layers at soft planar films in connection with their structure that may vary according to pH, salt concentration or temperature depending on the responsive character of the system. It is demonstrated how the combination of streaming current, surface conductivity and swelling measurements allows for a comprehensive understanding of the interrelated protolytic, hydrodynamic, electrostatic and structural properties of polymer layers. We discuss the benefits and limits of the approach on the basis of studies carried out on uncharged, moderately charged and highly charged soft polymeric films supported by hard charged carriers. In a final part, the basic processes governing the peculiar electrokinetic properties of soft planar polyelectrolyte multilayers under lateral flow conditions are described. © 2013 Elsevier Ltd.

Maul A.,CNRS Interdisciplinary Laboratory for Continental Environments
Risk Analysis | Year: 2014

Microbial risk assessment is dependent on several biological and environmental factors that affect both the exposure characteristics to the biological agents and the mechanisms of pathogenicity involved in the pathogen-host relationship. Many exposure assessment studies still focus on the location parameters of the probability distribution representing the concentration of the pathogens and/or toxin. However, the mean or median by themselves are insufficient to evaluate the adverse effects that are associated with a given level of exposure. Therefore, the effects on the risk of disease of a number of factors, including the shape parameters characterizing the distribution patterns of the pathogen in their environment, were investigated. The statistical models, which were developed to provide a better understanding of the factors influencing the risk, highlight the role of heterogeneity and its consequences on the commonly used risk assessment paradigm. Indeed, the heterogeneity characterizing the spatial and temporal distribution of the pathogen and/or the toxin contained in the water or food consumed is shown to be a major factor that may influence the magnitude of the risk dramatically. In general, the risk diminishes with higher levels of heterogeneity. This scheme is totally inverted in the presence of a threshold in the dose-response relationship, since heterogeneity will then have a tremendous impact, namely, by magnifying the risk when the mean concentration of pathogens is below the threshold. Moreover, the approach of this article may be useful for risk ranking analysis, regarding different exposure conditions, and may also lead to improved water and food quality guidelines. © 2014 Society for Risk Analysis.

Vasseur P.,CNRS Interdisciplinary Laboratory for Continental Environments | Bonnard M.,University of Reims Champagne Ardenne
Current Zoology | Year: 2014

Pollutant dynamics and bioavailability greatly differ in soil and aquatic systems. Therefore, specific approaches and models are needed to assess the impact of soil contamination to terrestrial ecosystems. Earthworms among other soil invertebrates have received more attention because of their ecological importance. They represent a dominant part of the soil biomass and are soil engineers regulating important soil processes, notably fertilization. The release in soils of pollutants known for their persistence and/or their toxicity is a concern. Exposure of terrestrial species to pollutants that may alter genomic function has become an increasing topic of research in the last decade. Indeed, genome disturbances due to genetic and epigenetic mechanisms may impair growth, as well as reproduction and population dynamics in the long term. Despite their importance in gene expression, epigenetic mechanisms are not yet understood in soil invertebrates. Until now, pollutant-induced changes in genome expression in natural biota are still being studied through structural alteration of DNA. The first biomarker relating to genotoxicant exposure in earthworms from multi-contaminated soils reported is DNA adducts measurements. It has been replaced by DNA breakage measured by the Comet assay, now more commonly used. Functional genomic changes are now being explored owing to molecular "omic" technologies. Approaches, objectives and results are overviewed herein. The focus is on studies dealing with genotoxicity and populational effects established from environmentally-relevant experiments and in situ studies. © 2014 Current Zoology.

Mondy C.P.,CNRS Interdisciplinary Laboratory for Continental Environments | Usseglio-Polatera P.,CNRS Interdisciplinary Laboratory for Continental Environments
Freshwater Biology | Year: 2014

Functional homogenisation of ecological communities (i.e. communities composed mainly of generalist species) is a major concern and has been often considered as a non-random effect of anthropogenic stress, with generalist taxa being preferentially selected under increasing stress. However, the degree of specialisation of a given taxon for a particular resource (a convenient proxy for studying functional homogenisation) is often described simply as 'uses the resource' or 'does not', despite there being an obvious continuum of degrees of specialisation by species for many different resources. Moreover, the non-randomness of the relationship between resource specialisation by the species making up a community and anthropogenic stress has been rarely tested. In this study, a framework based on fuzzy-coded traits is proposed to calculate a new continuous index of potential specialisation for a variety of taxa in a wide range of ecosystems. The use of this index is illustrated using 10 Eltonian and 11 Grinnellian traits of stream macroinvertebrate assemblages. We tested (i) the significance of the relationships between the average degree of specialisation among the taxa of a community and two types of anthropogenic stress (acidification and organic contamination) at the local scale and (ii) the non-randomness of these relationships. Stress gradients explained, through non-random effects, a rather high proportion of the variability observed in the degree of taxon specialisation, with significant relationships for eight of the 21 traits studied with regard to acidification and for 18 of the 21 traits with regard to organic contamination. Although most of these relationships described functional homogenisation (i.e. decreasing specialisation with increasing stress), increasing specialisation with increasing stress was demonstrated for a few Eltonian traits. We confirmed the importance of indicators of functional homogenisation calculated at the community level when studying the loss of biodiversity due to anthropogenic stress. The assessment of ecological specialisation seems to be a very promising strategy for understanding the effects of habitat impairment on community and ecosystem processes. Moreover, we show that the intensity of functional homogenisation depends on a trade-off between 'direct' and 'indirect' effects of stressors, and we consider that more attention should be paid to the mechanisms by which anthropogenic stressors act on taxa. © 2013 John Wiley & Sons Ltd.

Schnitzler A.,CNRS Interdisciplinary Laboratory for Continental Environments
Landscape and Urban Planning | Year: 2014

In Europe today, relatively pristine forest areas are very rare, with only 1.4% of the landscape identified as untouched forest and another 3.3% as having minimal intervention. In response to the small, isolated nature of these forests, ideas have emerged around the re-creation of a "new European wilderness" as a nature conservation strategy. Indeed, since the end of the 19th century, traditional land use practices have been in steady decline throughout many of Europe's rural landscapes, particularly in mountainous regions and areas with poor soils and harsh climates. These very recent ecosystems have been identified as "emerging," "novel" or "feral," but given enough time these areas could grow into mature forests. A conservation strategy based upon letting ecosystems evolve out of human control is, as one might expect, a controversial one for Europeans. Indeed, many people enjoy the diverse and small-scale structured landscape shaped by milennia of sustainable practices by farmers, and their loss is usually seen negatively. In this essay I argue the necessity for such a re-wilding strategy and provide examples in unmanaged forests and natural successions of the Mediterranean basin, temperate Europe and floodplains with regard to the ecological benefits that they may bring to in terms of wildlife and social values. Advocating such a perspective may have broader value in diminishing the self-centred tendencies of modern societies in how they manage ecosystems. © 2014.

Rotureau E.,CNRS Interdisciplinary Laboratory for Continental Environments
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2014

In aqueous systems, interactions of metal ions with colloidal interphases are considered as a key feature for analyzing trace metal speciation, mobility, lability and bioavailability. Among colloidal matters of interests, clay minerals play a major role in metal complexes formation and sorption. The aim of this study is to analyze the dynamic speciation of metal in the presence of clay as colloidal ligand. This work is achieved by means of two complementary electroanalytical techniques: Absence of Gradients and Nernstian Equilibrium Stripping (AGNES) is used for the direct determination of the free metal in solution and stripping chronopotentiometry at scanned deposition potential (SSCP) is applied for the dynamic speciation analysis. The measured response of SSCP reflects the flux properties (limiting transport or kinetic fluxes) of metallic species and allows the determination of thermodynamic constants and analytical lability features of metal complexes. In addition to that, one of the main interests of using such a technique lies in the fact that analyses are achieved in metal concentrations of environmental relevance (from millimolar to nanomolar). For anisotropic and chemically heterogeneous particles such as clay particles, this study demonstrates the possibility to obtain useful information as the determination of diffusion coefficients of particles as well as the description of dynamic behavior of metal species as a function of physicochemical conditions of the suspension. In this regard, this study shows that the sorption of cadmium by clays can be described as a chemically homogeneous and labile system along a large range of pH whereas lead sorption shows some heterogeneity aspects, while remaining SSCP-labile. © 2013 Elsevier B.V.

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