Modèles ecologiques pour l'extrapolation des effets écotoxicologiques enregistrés lors de biotests in situ cheZ Gammarus

[Departement_IRSTEA]Eaux [TR1_IRSTEA]BELCAInternational audienceEvaluating the effects of chemical contamination on populations and ecological communities still constitutes a challenging necessity in environmental management. However the toxic effects of contaminants are commonly measured by means of organism-level responses. Linking such effects measures with ecological models is a promising way to apprehend population-level impacts. In this way, population models are currently increasingly used in predictive risk assessment procedures, but their use in environmental diagnostic framework remains limited due to their lack of ecological realism. The present study with the crustacean amphipod Gammarus fossarum, a sentinel species in freshwater monitoring, combines a dual field and laboratory experimental approach with a population modelling framework. In this way, we developed an ecologically-relevant periodic matrix population model for Gammarus. This model allowed us to capture the population dynamics in the field, and to understand the particular pattern of demographic sensitivities induced by Gammarus life-history phenology. The model we developed provided a robust population-level assessment of in situ-based effects measures recorded during a biomonitoring program on a French watershed impacted by past mining activities. Thus, our study illustrates the potential of population modelling when seeking to decipher the role of environmental toxic contamination in ecological perturbations

Effects of metals on feeding rate and digestive enzymes in Gammarus fossarum: an in situ experiment

International audienceThe feeding activity and afterward the assimilation of the products resulting of the food digestion, allow organisms to obtain energy useful for growth, maintenance and reproduction. These biological parameters may be studied to assess the impact of contaminants on the energy metabolism of organisms, which could induce potential effects at an individual level. The studied species was an amphipod Gammarus fossarum, which has a high ecological relevance since it is widespread in European streams and plays a major role in the breakdown of leaf litter. Thus some G. fossarum were transplanted in four sites of a river characterized by metal contamination (Amous River, France). The following parameters were studied: digestive enzymes activities (esterase, β-glucosidase, β-galactosidase, amylase and endoglucanase), feeding rate, metal bioaccumulation and survival. Results showed a strong relationship between digestive enzymes activities, feeding rate and metal contents

Effect of water quality and confounding factors on digestive enzyme activities in Gammarus fossarum

International audienceThe feeding activity and subsequent assimilation of the products resulting from food digestion allow organisms to obtain energy for growth, maintenance and reproduction. Among these biological parameters, we studied digestive enzymes (amylase, cellulase and trypsin) in Gammarus fossarum to assess the impact of contaminants on their access to energy resources. However, to enable objective assessment of a toxic effect of decreased water quality on an organisms’ digestive capacity, it is necessary to establish reference values based on its natural variability as a function of changing biotic and abiotic factors. To limit the confounding influence of biotic factors, a caging approach with calibrated male organisms from the same population was used. This study applied an in situ deployment at 23 sites of the Rhone basin rivers, complemented by a laboratory experiment assessing the influence of two abiotic factors (temperature and conductivity). The results showed a small effect of conductivity on cellulase activity and a significant effect of temperature on digestive enzyme activity but only at the lowest temperature (7 °C). The experimental conditions allowed us to define an environmental reference value for digestive enzyme activities to select sites where the quality of the water impacted the digestive capacity of the organisms. In addition to the feeding rate, this study showed the relevance of digestive enzymes as biomarkers to be used as an early warning tool to reflect organisms’ health and the chemical quality of aquatic ecosystems

Influence of biotic and abiotic factors on metallothionein level in Gammarus pulex

International audienceDetection and assessment of the impact of pollution on biological resources imply increasing research on early-warning markers such as metallothioneins in metal exposure. Metallothioneins are cytosolic, low-molecular-weight proteins, involved principally in essential metal homeostasis and non-essential metal detoxication. Metallothionein synthesis could be influenced by abiotic (season) or biotic (reproduction process) factors directly or indirectly by its effect on metal bio-accumulation (i.e., sex, weight). In view of using metallothioneins as metal-exposure biomarkers in Gammarus pulex, this study attempts to define the effect of several factors (sex, weight/size and season) on the level of this protein. Metallothionein levels recorded in individuals over a large range of weights indicate a negative correlation between them. Inversely in our conditions, no difference was observed between male and female organisms. During field study, metallothionein level changes were observed with the highest levels in autumn and winter periods. The highest metallothionein levels were observed after the reproduction period, perhaps with the metabolic needs of biologically available essential metal such as zinc

Application of multi-marker approach for assessment of stress syndrome in transplanted mussels Dreissena polymorpha

Zebra mussels Dreissena polymorpha were transferred for 14, 28, 60 and 120 days from their reference site (C) to sites with agricultural pollution (A), industrial pollution from the alcohol industry (I1), or manufactured wastes (I2). The aim for that was to determine their ability to reflect various types of stressful conditions. General temporal patterns of mussels were confirmed by Centroid grouping and Discriminant Function analysis of the battery of their biochemical markers. After 14 days of transplantation, mussels demonstrated most prominent inter-site differences. In site A, a decreasing of the activity of oxidative defense enzymes took place, demonstrating weak stress response. In both sites I, increased levels of lipid peroxidation, metallothioneins and ethoxyresorufin-O-deethylase indicated oxidative injury, pollution by heavy metals, and persistent organic compounds, respectively. Low cholinesterase activity was detected in both C and B sites, showing the pollution by agricultural discharges. Prolonged exposure to polluted environment provoked the endocrine disruption (high levels of vitello­genin-like proteins), oxidative stress and decrease of glutathione and metallothionein concentrations, especially in the industrial sites

Variation temporelle des activités enzymatiques digestives et taux d'alimentation chez le gammare G. fossarum exposé en milieux contaminés

International audienceThe aim of this study was to use digestive enzyme activities in Gammarus fossarum as biomarkers during active biomonitoring. Standardised gammarids were transplanted for 7 days to five sites in the Riou Mort watershed contaminated by polymetallic pollution. This experiment was conducted on seven different dates from February 2009 to June 2010. Feeding rates were tracked, along with amylase, cellulase and trypsin activities. We found that feeding rate and digestive capacity were reduced in the most polluted site, “Joany,” in comparison with the reference site “Up.Lot”. The results suggested that trypsin was more sensitive than the other two carbohydrases. In the four other sites, seasonal differences were observed during the 2 yr but no clear pattern can be established. This study highlights the ability of G. fossarum to demonstrate environmental disturbances and suggests the use of a caging process in certain seasons. Caging organisms and feeding ad libitum is advantageous, as it reduces inter-individual variability and removes dependence on the native food fluctuations. However, confounding factors other than temperature were present, and the interpretation of digestive enzyme activities is complex

Concentrations métalliques et réponses biologiques in situ : Validation de l'utilisation de la dreissène en surveillance active sur le bassin de l'Orge

L'analyse approfondie de l'imprégnation chimique de sites-atelier et des impacts de cette multi-contamination sur les écosystèmes aquatiques soumis à une pression urbaine est un objectif fort de la phase 5 du PIREN-Seine. Cette analyse suppose l'application in situ de différentes méthodes de mesure (chimiques et biologiques), à coordonner entre les équipes de recherche du PIREN-Seine impliquées. En 2007, nous avons cherché à valider la faisabilité d'une étude approfondie sur un des sites atelier, un petit bassin très urbanisé, le bassin versant de l'Orge. Il s'agissait donc de déployer, de façon concertée, des échantillonneurs intégratifs qui permettent une estimation moyenne de la contamination dissoute biodisponible (Tusseau-Vuillemin et al. 2004), de transplanter des dreissènes encagées, et de suivre durant cette campagne sur une durée de un mois, la contamination du milieu par des prélèvements ponctuels réguliers. Les objectifs de cette campagne étaient plus particulièrement de valider les méthodologies d'étude d'un site par échantillonnage intégratif et prélèvements ponctuels de vérifier la résistance des dreissènes à la transplantation sur l'Orge de fournir un aperçu de la contamination métallique des eaux de l'Orge et de ses affluents, et des différentes réponses biologiques (biomarqueurs et bioaccumulation) sur la dreissène

Energy Metabolism and Pesticides: Biochemical and Molecular Responses to Copper in Roach Rutilus rutilus

Copper (Cu) is a trace element which is essential to life, especially in cellular biochemi- cal reactions (including cellular respiration) and acts as a cofactor for many enzymes. [...

Etude du transfert trophique de nanomatériaux et des conséquences sur les organismes

Le projet TRONANO visait à acquérir des données sur l’écotoxicité de différentes nanoparticules (NP) et résidus de dégradation de nanomatériaux en étudiant leur impact sur des biofilms et des macroinvertébrés d’eau douce via une exposition par l’eau ou la nourriture respectivement. Trois catégories de nanomatériaux commercialisés, avant ou après dégradation ont été étudiés : des produits de dégradation de NPs manufacturées à base de TiO2 (Tlite®) et de CeO2 (nanobyk®), du TiO2 nu (rutile) et des NPs d’or fonctionnalisées. Le projet visait à répondre à plusieurs questions relatives au danger de bioaccumulation et d’effet toxique. Nous avons mis en oeuvre des expositions en laboratoire de biofilms diatomiques et de macroinvertébrés, crustacé (G. fossarum), insecte (C.riparius), gastéropode prosobranche (P. antipodarum) à différentes NPs altérées ou non, via un apport de nourriture naturelle (biofilms, feuilles) ou de nourriture commerciale. Des méthodologies de mesure d’exposition (dosage et détection des NPs dans le biote) d’une part et des mesures d’effet (analyses métabolomiques, caractérisation de gènes chez G. fossarum et dans le biofilm diatomique) d’autre part ont été développées. Suite à ces expositions, relativement longues (jusqu’à 6 semaines pour le gastéropode) comparativement à ce qui est couramment réalisé en laboratoire, nous avons cherché à détecter les réponses des organismes en mettant en oeuvre des mesures à différentes échelles d’organisation biologique, moléculaire, cellulaire ou au niveau individu (trait de vie). En fonction des nanomatériaux étudiés nos résultats mettent en évidence un possible transfert de la contamination depuis la nourriture vers les organismes. Cette contamination s’est accompagnée d’effets biologiques, avec des réponses moléculaires et biochimiques détectables sur les biofilms et les invertébrés. En particulier les NPs d’or chargées positivement conduisent à des réponses moléculaires et histologiques significatives pour les biofilms et les gammares. En conséquence l’évaluation de l’impact potentiel de ces AuNPs sur la croissance ou la reproduction des organismes, suite à des expositions sur de plus longues périodes apparait nécessaire pour une évaluation du risque pertinente. De la même manière, l’exposition trophique aux NP de CeO2, de TiO2 rutile et de RDN de Tlite® conduit à des perturbations de certaines activités enzymatiques du métabolisme digestif et de défense au stress oxydant. Ces perturbations/ acclimatations dépendent des invertébrés et des activités mesurées. Néanmoins malgré des expositions que l’on peut qualifier de chroniques (21 jours pour G. fossarum, 42 jours pour P. antipodarum et 7 jours pour C. riparius), aucun des traits de vie (survie, croissance, reproduction, alimentation) couramment mesurés chez ces espèces pour étudier la toxicité de substances n’a été affecté. Ces résultats conduisent à conclure à un faible danger environnemental de ce type de nanomatériaux