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Theses

Développement d'outils écotoxicologiques pour l'évaluation de sédiments

Abstract : The development of bioassays for the assessment of the toxic potential of contaminated sediments is in constant evolution. These bioassays are generally used in the context of a battery. However, very few tools exist for the integration of their results for the comparison of sites and the priorization of sediment management actions. It is in this context that this thesis has been prepared. The SED-TOX index of ecotoxic hazard has been developed and validated. To achieve this, we identified the bioassays that would serve as the basis for the development of the Index. It was important that this battery covers a variety of sediment phases (e.g., interstitial water, organic extract, solid-humid phase, and whole sediment), trophic levels (e.g., bacteria, algae, microinvertebrates), toxicity types (i.e., acute and chronic) and levels (i.e., lethal, sublethal) to maximize its sensibility, potential for discrimination and ecological relevance. It was also critical that the Index be applicable to a wide variety of sediment type, whether they originate from marine or freshwater ecosystems. During the bioassay selection process, we noted that, in spite of the large number of tests that can be performed on aqueous sediment extracts (e.g., interstitial water, elutriates, organic extracts), their adequacy for a routine application on organic extracts has not yet been clearly demonstrated. Hence, we have elaborated a protocol for the organic extraction, concentration, and fractionation or sediments, which has been coupled to three genotoxicity assays (SOS ChromotestMC, Mutatox and fluctuation test) in order to propose an effective method for the evaluation of the effects associated with organic contaminants on DNA of exposed organisms. This work has demonstrated that, when applied to sediments taken at various stations along a gradient of organic contamination, the SOS ChromotestMC conducted on the F2 fraction (i.e., containing molecules whose weight varies between 250-800 atomic mass units) was the most sensitive and discriminatory of the three tests examined. The Index was applied to a series of marine samples and to two distinct series of freshwater samples, to examine the following three aspects : Its flexibility: is the Index applicable to diverse types of sediments and to different bioanalytical batteries ? Its discrimination potential: does the Index allow one to distinguish between polluted sites and those that are relatively uncontaminated ? Its predictive potential: how does the Index compare with measures of benthic community perturbations?his work has shown that : a.the Index is applicable to a variety of sediments (i.e., freshwater and marine) and to different test batteries; b.the Index can reveal significative differences between the toxic potential of sediments whose contamination levels vary, that it can be used to derive toxicity levels that will assist in sorting sediment samples according to their hazard potential for aquatic organisms ; the SED-TOX results correlate with indices that are used to gauge the quality of benthos. The identification of significant correlations between the SED-TOX index and indices of benthic quality suggest that the Index can be used for predicting degraded sediment quality in the field. These results also suggest that relatively simple laboratory tests using a variety of effect endpoints can provide information that, when coupled with species and community attributes, has direct relevance to the assessment of ecological hazards by anthropogenic stressors
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Manon Bombardier. Développement d'outils écotoxicologiques pour l'évaluation de sédiments. Ecotoxicologie. Université Paul Verlaine - Metz, 2007. Français. ⟨NNT : 2007METZ043S⟩. ⟨tel-01749030⟩

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