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Variabilité interspécifique et intraspécifique des indices physiologiques chez les diatomées toxiques du genre Pseudo-nitzschia : influence du cycle de vie

Abstract : In the diatom Pseudo-nitzschia, some species produce a neurotoxin called domoic acid responsible for amnesic shellfish poisoning in humans following the consumption of contaminated molluscs. In the Bay of Seine (English Channel), the variability of bloom toxicity is linked to differences in the Pseudo-nitzschia species diversity. The aim of this thesis was to characterize the ecophysiological diversity within the genus Pseudo-nitzschia in order to better understand the physiological parameters influencing differences in toxicity and bloom phenology among the main Pseudo-nitzschia species of the Bay of Seine. Growth, domoic acid production, elemental intracellular quotas, photosynthetic parameters and kinetic parameters for nitrate, phosphate, and silicic acid uptake were studied in four Pseudo-nitzschia species: P. australis, P. pungens, P. fraudulenta et P. delicatissima. The intraspecific variability was characterized with a multi-strain approach and also considering the effect of cell size on the studied physiological parameters. The results highlight the importance of the intraspecific variability in the physiology of the four species, in part due to cell size reduction linked to Pseudo-nitzschia life cycle. Delineate the intraspecific diversity allowed to characterize different physiological traits for each species. This work brings new information on the physiological conditions favorable to domoic acid production and on the role of nutrients in controlling Pseudo-nitzschia species diversity during blooms.
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Aurore Sauvey. Variabilité interspécifique et intraspécifique des indices physiologiques chez les diatomées toxiques du genre Pseudo-nitzschia : influence du cycle de vie. Biologie végétale. Normandie Université, 2018. Français. ⟨NNT : 2018NORMC266⟩. ⟨tel-02159407⟩

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