Aspects de la toxicité et de la biosorption du cadmium chez l'algue Chlorella vulgaris

Not availableL'ATPase plasmalemmique est la première structure active altérée par le cadmium et la fonction de cette enzyme est suffisamment importante pour expliquer une partie de la toxicité du cadmiu

Aspects de la toxicité et de la biosorption du cadmium chez l'algue Chlorella vulgaris

Not availableL'ATPase plasmalemmique est la première structure active altérée par le cadmium et la fonction de cette enzyme est suffisamment importante pour expliquer une partie de la toxicité du cadmiu

Elaboration d'un modèle de chaîne trophique dulçaquicole et application à une étude écotoxicologique du cadmium

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Quel test de toxicité chronique sur invertébrés faut-il choisir pour l’évaluation de la dangerosité des déchets ?

ln this article, the 7-d Ceriodaphnia dubia and 21-d Daphnia magna tests, which can be used for the ecotoxicology assessment of wastes, are presented. The main differences between them are discussed and commented. They show that it would be preferable to use the 7-d C. dubia test than the 21-d D. magna test for the ecotoxicology assessment of wastes. Some results are presented and confirmed this statement.Dans cet article, les tests Ceriodaphnia dubia 7 jours et Daphnia magna 21 jours, utilisables pour l'évaluation de l'écotoxicité des déchets, sont présentés. Les principales différences sont discutées et commentées, et montrent que le test C. dubia 7 jours est préférable au test D. magna 21 jours. Des résultats obtenus sur des lixiviats de déchets viennent confirmer ce fait

Besoins de recherches (en écotoxicologie) en lien avec les politiques publiques

[Departement_IRSTEA]Eaux [TR1_IRSTEA]BELCAInternational audiencePublic policies that intend to protect ecosystems or human health from toxic impairments in the environment need to be as much evidence based as possible. The precautionary principle applies when little or no evidence is available. This is the case for unknown risks from new or non assessed chemicals in the environment. Moving from precaution to prevention where enough evidence is available for sound decisions implies developing research actions or research strategies

Effects of Sublethal Cadmium Exposure on Antipredator Behavioural and Antitoxic Responses in the Invasive Amphipod Dikerogammarus villosus

Amphipods are recognised as an important component of freshwater ecosystems and are frequently used as an ecotoxicological test species. Despite this double interest, there is still a lack of information concerning toxic impacts on ecologically relevant behaviours. The present study investigated the influence of cadmium (Cd), a non-essential heavy metal, on both antipredator behaviours and antitoxic responses in the invasive amphipod Dikerogammarus villosus under laboratory conditions. Amphipod behaviour (i.e. refuge use, aggregation with conspecifics, exploration and mobility) was recorded following a 4-min test-exposure to 500 µg Cd/L with or without a 24-h Cd pre-exposure and in the presence or absence of a high perceived risk of predation (i.e. water scented by fish predators and injured conspecifics). Following behavioural tests, malondialdehyde (MDA) levels, a biomarker for toxic effect, and energy reserves (i.e. lipid and glycogen contents) were assessed. Cd exposures induced (1) cell damage reflected by high MDA levels, (2) erratic behaviour quantified by decreasing refuge use and exploration, and increasing mobility, and (3) a depletion in energy reserves. No significant differences were observed between 4-min test-exposed and 24-h pre-exposed individuals. Gammarids exposed to Cd had a disturbed perception of the alarm stimuli, reflected by increased time spent outside of refuges and higher mobility compared to gammarids exposed to unpolluted water. Our results suggest that Cd exposure rapidly disrupts the normal behavioural responses of gammarids to alarm substances and alters predator-avoidance strategies, which could have potential impacts on aquatic communities

Genotoxic effects and induction of phytochelatins in the presence of cadmium in Vicia faba roots

International audienceThis study investigates different effects in roots of Vicia faba (broad bean) after exposure to cadmium. Genotoxic effects were assessed by use of the well-known Vicia root tip micronucleus assay. Cytotoxic effects were evaluated by determining the mitotic index in root tip cells. Finally, molecular induction mechanisms were evaluated by measuring phytochelatins with HPLC. After hydroponical exposure of V. faba roots to a range of cadmium concentrations and during different exposure times, the results of this approach showed large variations, according to the endpoint measured: after 48 h of exposure, genotoxic effects were found between 7.5 × 10−8 and 5 × 10−7 M CdCl2, and cytotoxic effects were observed between 2.5 × 10−7 and 5 × 10−7 M CdCl2. Statistically significant phytochelatin (PC) concentrations were measured at ≥10−6 M CdCl2 for PC2, and at ≥10−5 M CdCl2 for PC3 and PC4

Assessment of the LuminoTox leachate phase assay as a complement to the LuminoTox solid phase assay: Effect of fine particles in natural sediments

International audienceThe LuminoTox solid phase assay (Lum-SPA), developed to assess the potential ecotoxicity of natural polluted sediments, employs stabilized thylakoids isolated from spinach plant extracts. When thylakoids are exposed to polluted samples, the action of pollutants can interfere with transmission of chlorophyll fluorescence linked to Photosystems I and II, causing a decrease in fluorescence emission. To differentiate between bulk and leachate effects, we developed a complementary assay of the Lum-SPA named the LuminoTox leachate phase assay (Lum-LPA). Twelve natural sediments were selected on the basis of their potential ecotoxicity and different quantities of fines. Results showed that in the Lum-LPA, the IC50s were always lower than those observed in the Lum-SPA. Significant inverse correlations were found between the IC50s obtained with the Lum-SPA and the percentage of fines (silt + clay fraction). In order to identify the cause of the higher ecotoxicity found in the Lum-LPA, we tested the supernatant of the liquid phase recovered after centrifugation (3000g), and it appeared far less toxic than the Lum-LPA filtrates. To confirm the hypothesis that sensitivity in the Lum-LPA could be due to the presence of very fine particles, Photosynthetic Enzyme Complexes (PECs) were exposed to two kinds of clay materials with and without copper (0.6 mg L-1). Similar results were obtained in the Lum-LPA for both cases, revealing the sensitivity of this test to very fine particles

Estimation of deltametrin bio-accumulation kinetics and dynamics of effects on daphnia population

The long-term prediction and estimation of contamination effects on aquatic organisms, at individual or population level, are a real research problem. The models of Dynamic Energy Budget in toxicology (DEBtox) allowed to the possibility of B.I. Camara 2 Baba I. Camara et al. rigorously tackling this type of problem by connecting the period and the concentration exposure to the chemical bio-accumulation dynamics and the damage dynamics that this contaminant will cause on an organism. In this paper, the focus was assessing the long-term impact of deltamethrin effects on daphnia magna growth and reproduction. For this purpose, a chronic 21 day experiment was run in our laboratory to acquire the data adjusting our model. Then, we fitted our DEBtox model by using bayesian inference algorithm developed in the R package deBIn-fer. This bayesian inference method allowed to estimate simultaneously both bio-accumulation parameter values and daphnia growth and reproduction parameter values in contaminated deltamethrin environment. For risk assessment, our statistical analysis showed that deltamethrin effects on reproduction (maximum reproduction rate, cumulative reproduction) and energy allocation (investment rate) are observed when the bio-accumulated deltamethrin exceeded the estimated no-effect concentration NEC = 5.849 ngL −1. Furthermore, variation correlations of physiological parameter values were highlighted in long-term deltamethrin exposure environment

Microplastics enhance Daphnia magna sensitivity to the pyrethroid insecticide deltamethrin: Effects on life history traits

International audienceThe aim of the study was to investigate the influence of microplastics (MPs) on the ecotoxicity of common contaminants of aquatic ecosystems. As a model contaminant, the hydrophobic pesticide deltamethrin (DM) was chosen, and its effects on life history traits of Daphnia magna were studied in the presence or absence of polyethylene MPs. Commercialized DM and MPs obtained as dry powder were used in the experiment. According the manufacturer (Cospheric, Santa Barbara, CA, USA) MPs were spherical (1–4 μm in diameter), had a density of 0.96 g/cm−3 and were without any solvent. Three concentrations of polyethylene MPs were tested (0, 1, 10 mg/L) with two realistic concentrations of DM (0 and 40 ng/L) and a solvent control (acetone). During the 21 d experiment, D. magna neonates were individually exposed to the treatments, and the effects of MPs and DM alone and together were evaluated by assessing survival, number of cumulative molts, days to first brood, number of broods, number of neonates per surviving adult, and body length. Significant detrimental effects on survival were only observed for the two mixture treatments. DM alone (40 ng/L) delayed the days to first brood and reduced the number of neonates per surviving adult, whereas MPs alone (10 mg/L) induced significant reduction in the number of juveniles by surviving adults. The combined exposure to DM and MPs clearly had a synergistic effect on survival, brood number, and number of neonates per surviving female. For example, compared to exposure to 40 ng/L of DM alone, the addition of 1 mg/L of MPs resulted in a 51.1% reduction in number of neonates per surviving female and a 46% reduction in brood number. These results suggest the potential drastic effects of this kind of mixed exposure on daphnid populations, which are key components of freshwater food webs. (C) 2020 Elsevier B.V. All rights reserved