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Impact De La Saisonnalité Et D'une Contamination Pesticide

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Impact De La Saisonnalité Et D'une Contamination Pesticide Impact de la saisonnalité et d’une contamination pesticide environnementale sur des relations biotiques entre la micro-méiofaune et les microalgues d’un biofilm d’eau douce Julie Neury-Ormanni To cite this version: Julie Neury-Ormanni. Impact de la saisonnalité et d’une contamination pesticide environnementale sur des relations biotiques entre la micro-méiofaune et les microalgues d’un biofilm d’eau douce. Ecotoxicologie. Université de Bordeaux, 2019. Français. NNT : 2019BORD0343. tel-03091966 HAL Id: tel-03091966 https://tel.archives-ouvertes.fr/tel-03091966 Submitted on 1 Jan 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. THÈSE PRÉSENTÉE POUR OBTENIR LE GRADE DE DOCTEUR DE L’UNIVERSITÉ DE BORDEAUX ÉCOLE DOCTORALE : « SCIENCES ET ENVIRONNEMENTS » SPÉCIALITÉ : ECOLOGIE EVOLUTIVE ET FONCTIONNELLE DES COMMUNAUTES Par Julie NEURY-ORMANNI Impact de la saisonnalité et d’une contamination pesticide environnementale sur des relations biotiques entre la micro-méiofaune et les microalgues d’un biofilm d’eau douce Sous la direction de : Soizic MORIN Chargée de recherche, Irstea-Bordeaux Directrice de thèse Jacky VEDRENNE Ingénieur d’étude, Irstea-Bordeaux Co-encadrant Irstea – Unité de Recherche Ecosystèmes aquatiques et Changements Globaux Soutenance le 12 Décembre 2019 Membres du jury : Michèle TACKX Professeure, Université Paul Sabatier, Présidente Toulouse Philippe USSEGLIO-POLATERA Professeur, Université de Lorraine Rapporteur Helena GUASCH Professeure, CEAB-CSIC, Espagne Rapporteur Juliette FABURE Maître de conférences, AgroParisTech Examinateur Cédric HUBAS Maître de conférences, MNHN Examinateur Clarisse MALLET Maître de conférences, Université Clermont- Examinateur Auvergne Impact de la saisonnalité et d’une contamination pesticide environnementale sur des relations biotiques entre la micro- méiofaune et les microalgues d’un biofilm d’eau douce Résumé : Les pollutions chimiques sont des facteurs de stress pour le milieu aquatique qui est le réceptacle final des microcontaminants (pesticides, médicaments, métaux). Le biofilm est un microécosystème aquatique dans lequel interagissent des microorganismes aux cycles de vie très courts (bactéries, champignons, microalgues, micro- méiofaune) sur un substrat. Certains facteurs saisonniers (lumière, température) ou liés à l’anthropisation (substances dissoutes dont les polluants toxiques) modifient la composition de microalgues, et impactent également les cycles biologiques de la micro-méiofaune. Ces déterminants environnementaux façonnent diversement les communautés périphytiques au long de l'année, directement et indirectement au sein du réseau complexe d'interactions entre les espèces. Le déséquilibre potentiel entre les composantes susceptibles d'être impactées par des polluants (organismes cibles et non cibles) peut menacer la stabilité structurale et fonctionnelle des biofilms. Dans ces travaux de thèse nous avons étudié les effets de l’imidaclopride (insecticide) et du diuron (herbicide) sur les relations biotiques maintenues entre les microalgues et la micro-méiofaune des biofilms. Ces deux pesticides sont régulièrement détectés dans les rivières françaises. Des tests écotoxicologiques à des concentrations environnementales (5µg.L-1) ont d’abord été réalisés sur des populations monoespèces et des combinaisons de populations de micro-méiofaune (nématodes, chironomes) et de microalgues benthiques (diatomées, algues vertes). La combinaison de stress biotique et chimique a un effet non négligeable sur les individus de notre étude, qu’ils soient producteurs primaires ou consommateurs. En combinant les impacts d’un herbicide et d’un insecticide sur une relation trophique, on peut estimer comment les effets directs de ces pesticides sur leur cible, peuvent indirectement, par le jeu des relations biotiques, affecter les individus des chaînons trophiques supérieurs et inférieurs. De manière à ne pas écarter l’influence structurante des relations trophiques, nous avons abordé la question de variabilité de la communauté périphytique par l’approche des traits morphofonctionnels liés à l’activité trophique. Pour ce faire, une base de données regroupant les traits morphofonctionnels de la micro-méiofaune a été créée, basée sur le modèle de la base des macroinvertébrés d’eau douce d’Usseglio-Polatera et al. (2000). Les conditions abiotiques qui définissent un habitat varient selon la saisonnalité. Des communautés périphytiques ont été soumises aux variations saisonnières puis à une contamination pesticide. Nos résultats ont démontré que les conditions abiotiques et biotiques saisonnières ont un impact plus fort sur la fonctionnalité du biofilm que la contamination pesticide aux concentrations testées. Les traits morphofonctionnels de la micro-méiofaune évoluent selon les conditions abiotiques saisonnières. En cas de contamination pesticide, le peu d’impact mesuré peut s’expliquer par la redondance des traits morphofonctionnels des espèces de la micro-méiofaune sélectionnées par la pression chimique. Ces travaux de thèse confirment l’importance de la complémentarité des échelles d’étude et des combinaisons de facteurs biotiques et abiotiques dans la recherche en écologie et écotoxicologie. Mots clés : Relation trophique, traits fonctionnels, écotoxicologie Seasonality and environmental pesticide concentration impact on biotic relation between microalgae and micro-meiofauna in freshwater biofilm Abstract: Chemical pollutions are stress factors for the aquatic environment, which is the final receptor of microcontaminants (pesticides, pharmaceuticals, metals). Biofilm is an aquatic microecosystem in which short lifecycle microorganisms interact (bacteria, fungi, microalgae, micro-meiofauna) on a substrate. Seasonal (light, temperature) or anthropogenic factors (dissolved substances such as toxic pollutants) modify microalgae composition and also impact micro-meiofauna biological cycles. These environmental determinants diversely shape periphytic community all along the year, directly and indirectly in the complex species interaction network. The potential imbalance between biofilm components, likely to be impacted by pollutants (target and non-target organisms), can threat structural and functional biofilm stability. In these thesis works, we studied imidacloprid (insecticide) and diuron (herbicide) effect on biotic relationships maintained between periphytic microalgae and micro-meiofauna. These two pesticides are frequently detected in French rivers. Ecotoxicological tests at an environmental concentration (5µg.L-1) were firstly realized on monospecies populations and then, on combinations of benthic micro-meiofauna (nematodes, chironomids) and microalgae (diatoms, chlorophytes). Biotic and chemical stress combination showed non-negligible effects on studied species, i.e. primary producers or consumers. By combining herbicide and insecticide impact on trophic relationships, we can estimate how direct pesticide effects on their target indirectly affect other inferior or superior trophic levels. To take into account the structuring influence of trophic relationships, we discussed on periphytic community variability via the morphofunctional trophic activity traits approach. Micro-meiofauna morphofunctional traits database was created following Usseglio-Polatera et al. (2000) works on freshwater macroinvertebrates. Abiotic conditions which define a habitat vary with season. Periphytic communities were submitted to seasonal variations and pesticide contamination. Results demonstrated that abiotic and biotic seasonal conditions have a greater impact on biofilm functionality than pesticide contamination at the concentrations tested. In the case of pesticide contamination, little measured impacts can be explained by morphofunctional traits redundancy of micro-meiofauna species selected by chemical pressure. These thesis works highlight the importance of studying scales complementarity and biotic and abiotic factors combination in ecology and ecotoxicology research. Keywords : Trophic relation, functional traits, ecotoxicology Unité de recherche Ecosystèmes Aquatiques et changements globaux (EABX) Ecologie des communautés végétales aquatiques et impact des pressions multiples (ECOVEA) Irstea, Université de Bordeaux, 50 avenue de Verdun, 351 cours de la Libération, 33610 Cestas 33400 Talence France France Remerciements Je tiens tout d’abord à remercier Philippe Usseglio-Polatera, Helena Guasch, Juliette Faburé, Michèle Tackx, Cédric Hubas et Clarisse Mallet pour avoir accepté d’évaluer mon travail de thèse. Je remercie mon comité de pilotage : Emmanuel Corcket, Christine Dupuy et Nabil Majdi. Les regards extérieurs apportés lors de ces réunions ont été très novateurs pour le déroulement de cette thèse. Nabil Majdi, un grand merci pour toute cette passion partagée de la méiofaune, ton enthousiasme, les méthodo, les colloques, le numéro spécial ‘Freshwater meiofauna’… Et surtout de m’avoir permis de partir en mobilité en Allemagne. Merci à Frédéric Saudubray et Eric Rochard de m’avoir accueillie au sein
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