Nanomaterials as carriers of persistent organic pollutants : risk assessment for the aquatic environment using small invertebrates and model fish
Presence and effects of micro- (< 5mm) and nanomaterials (<100 nm, NM) in the environment are a current issue of concern. Aquatic ecosystems with high pollution pressure already present a cocktail of chemicals, where micro- and NMs can act as sponges for these pollutants due to their high surface to volume ratio and hydrophobic surface. This phenomenon can alter the bioavailability of the pollutants present in the aquatic ecosystem, especially for hydrophobic compounds and, therefore, modulate their toxicity to aquatic organisms. Therefore, in the present Thesis the following objectives were established: (1) To assess the potential bioavailability and toxicity of polystyrene nanoplastics (NPs), and of microplastics (MPs) alone and with sorbed polycyclic aromatic hydrocarbons (PAHs) to brine shrimp larvae and zebrafish; (2) To determine sorption capacity of PAHs to MPs and graphene oxide NMs (GNMs); (3) To assess the potential bioavailability and toxicity of GNMs alone and with sorbed PAHs to zebrafish.Exposure to pristine MPs did not cause any significant impact on brine shrimp larvae and zebrafish embryo survival, while some treatments containing elevated concentrations (mg/L) of MPs with sorbed benzo(a)pyrene (B(a)P) and B(a)P alone resulted in acute toxicity. In addition, both sizes of MPs were successful vectors of B(a)P to brine shrimp and zebrafish embryos. Results indicated that small MPs (0.5 µm) showed higher maximum sorption capacity for B(a)P than larger MPs (4.5 µm). In the case of a complex and environmentally relevant PAH mixture, as that formed in the water accommodated fraction (WAF) of a crude oil, a relatively limited sorption to 4.5 µm MPs, driven by the hydrophobicity and initial concentration of each PAH, was observed. In adult zebrafish, MPs did not act as PAH vehicle after 21-day exposure to MPs with sorbed PAHs. Only fish exposed to MPs for 21 days presented changes in the transcription level of biotransformation metabolism-related gene cyp1a in the liver, along with a significant increase in the prevalence of liver vacuolisation. 21 days of exposure to NPs, but not to MPs, caused oxidative stress in adult zebrafish. Ingestion of NPs was observed in the developing organisms (brine shrimp and zebrafish). In embryos, fluorescent NPs were specially localised in the eyes, yolk sac and tail, showing their capacity to translocate and spread into the embryo body.For GNMs, graphene oxide (GO) showed a higher sorption capacity for B(a)P than MPs. For the PAH mixture of the WAF, sorption to GO was also higher than to MPs. In embryos exposed to different GNMs alone and with PAHs, no significant mortality was recorded for any treatment. Nevertheless, malformation rate increased significantly in embryos exposed to the highest concentrations (5 or 10 mg/L) of GO, reduced GO alone and with sorbed B(a)P. According to chemical analysis of adult fish tissues, bioavailability of PAH sorbed to GO for fish was lower than in the case of PAHs alone. Only biochemical responses and genes related to biotransformation metabolism were altered in the liver of fish exposed to B(a)P for 3 days. Transcription level of genes related to oxidative stress were not altered. On the contrary, the gills of fish exposed to GO with sorbed B(a)P and to B(a)P for 3 days and co-exposed to GO and WAF for 21 days showed significantly higher oxidative stress than control fish. A common neurotoxic effect was caused in all fish treated for 21 days. Finally, adult fish exposed to GO presented GO ingestion and liver vacuolisation, but absence of GO translocation to the adult tissue was reported. The present work shows evidences of the capacity of MPs with sorbed PAHs to cause sublethal effects (1) and to carry PAHs (2) in brine shrimp and zebrafish. Finally, GO was greater carrier of PAHs to zebrafish than MPs (3) due to its higher sorption capacity (2), exerting oxidative stress and neurotoxicity as the main sublethal effects in adult zebrafish.
(22/12/2020)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Currently used pesticides and their mixtures : what are the risks to non-target aquatic organisms? Laboratory and in situ approaches.
Pesticides have enabled humankind to protect its crops from pests, intensifying thus the crop yields to sustain the growing population. However, pesticides often end up in aquatic water bodies, e.g. via field runoff, where they may harm non-target organisms. The environmental concentrations of pesticides are often considered safe for aquatic ecosystems although they might induce sublethal changes in exposed organisms. Moreover, the organisms are generally not dealing with only one pesticide issued from a nearby field but with a complex mixture of various chemical compounds, interacting amongst themselves, and creating a toxic cocktail with unknown and hardly predictable impacts. These compounds, each with different environmental fate, eventually degrade and form more or less toxic and persistent metabolites aggravating the complexity of the mixtures.This dissertation thesis summarizes the state-of-the-art in pesticide mixture toxicity research and is composed of five research articles dealing with sublethal effects of selected pesticides on non-target aquatic species. Vulnerable embryo-larval stages of two model organisms: freshwater zebrafish (Danio rerio) and euryhaline bivalve Pacific oyster (Magallana gigas) were used to assess the sublethal toxicity of especially environmental concentrations (detected in selected European water bodies) of commonly used herbicide S metolachlor with its two metabolites metolachlor oxanilic acid and metolachlor ethanesulfonic acid, insecticide imidacloprid, and fungicide propiconazole, alone and in a mixture. A complementary in situ approach was carried out to evaluate a real impact on early-life stages of the Pacific oyster in Arcachon Bay in France, a final recipient of various substances including pesticides from respective watersheds.First, zebrafish embryo-larval stages were observed to be highly sensitive to environmentally relevant concentrations of propiconazole and to a lesser extent also to imidacloprid. In contrast, S-metolachlor and its metabolites had almost no effect on their development, neurobehavioral functions, or gene expression except for altered genes implicated in the thyroid system. A mixture of these compounds exhibited a concentration addition effect on zebrafish development. These observations imply that the development of freshwater fish may be at risk with current agricultural practice.Second, a study with Pacific oyster embryos and larvae revealed very low toxicity of propiconazole and imidacloprid on their development and locomotion patterns. Few effects caused by these compounds were observed at the molecular level, as well as the effects caused by the mixture. The environmental concentration of the mixture induced developmental malformations in oyster larvae, however, those exposed in situ in Arcachon Bay did not show higher proportions of abnormal larvae suggesting that the water quality of Arcachon Bay is sufficient for oyster development. Nevertheless, oyster larvae exposed in the inner part of Arcachon Bay showed different gene expression levels than larvae from the reference site located near the ocean entrance, which may indicate consequences of a potential long term impact.These results documented that embryo-larval stages of zebrafish and Pacific oysters are relevant tools for the assessment of low concentrations of pesticides and pesticides in a mixture, and that laboratory studies complemented with field research are useful for (eco)toxicity assessment and of high ecological relevance.
(17/12/2020)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Variation de l’intensité de la facilitation avec la salinité et l’aridité dans les dépressions salines continentales de Tunisie.
L’objectif de ce travail de thèse est de clarifier le débat de la littérature d’écologie des communautés sur les variations d’interactions plante-plante le long de gradients de stress hydrique. Nous nous sommes focalisés sur l’importance du type de stress (ressources vs. non-ressources) et la méthode utilisée (observationnelle vs. expérimentale) pour quantifier les interactions biotiques. Les dépressions salines continentales (Sebkhas) de Tunisie se caractérisant par l’existence d’un gradient marqué de salinité dans des contextes climatiques contrastés est un excellent système modèle pour clarifier ce débat notamment en séparant les effets de la salinité de ceux du stress hydrique.Dans une première étape, nous avons effectué une étude observationnelle à l’échelle de la zone aride tunisienne afin d’identifier les conséquences des interactions possibles existant entre la topographie et le climat et déterminant les variations de stress salin et hydrique et donc la structure, la composition des communautés végétales et le fonctionnement des écosystèmes. Nous avons mis en place un dispositif de terrain croisant un traitement de position topographique (avec quatre habitats) et un traitement de stress hydrique (avec deux situations climatiques, le climat faiblement aride et le climat fortement aride) avec quatre répétitions à l’échelle régionale. Nous avons également effectué deux expérimentations, une première sur les l’effet des voisins par la méthode observationnelle avec transplantation de trois espèces dominantes dans l’ensemble des traitements et une sur l’effet de la méthode (observationnelle vs. expérimentale) avec transplantation de trois Poaceae dans les deux habitats les moins salés.L’étude observationnelle a clairement montré que la salinité est le facteur direct majeur déterminant la composition, la diversité et la structure des communautés, ainsi que la productivité des écosystèmes et leur fertilité. L’aridité a des effets moindres plus subtiles et son effet ne peut être comparé spatialement que dans l’habitat le moins salé entre les zones très et faiblement arides.La première étude expérimentale a montré que le stress salin (facteur direct non de ressource) entrainait un collapse de la facilitation et que ce collapse s’accentuait avec l’aridité croissante, aussi bien temporellement que spatialement. Nous n’avons pas trouvé de retour de la compétition en situation d’aridité extrême comme le prédit la littérature. Ceci est sans doute due à la stratégie faiblement compétitrice des Chaméphytes dominants les habitats les plus salés. La seconde étude expérimentale a montré qu’avant la saison sèche estivale les interactions de court-terme mesurées par la méthode expérimentale (removal method) sont négatives alors que les interactions de long-terme, mesurées par combinaison des méthodes observationnelle et expérimentale sont positives, confirmant nos hypothèses et la littérature. Cependant, après la saison sèche estivale les interactions de court-terme deviennent positives, alors que les interactions de long-terme collapsent par disparition de l’effet tampon du sol végétalisé sur l’humidité.Ces résultats sont cruciaux car ils montrent que dans ce système aride et à important stress salin le collapse de la facilitation est le processus majeur expliquant la structure, la diversité et le fonctionnement des écosystèmes et ce aussi bien le long des gradients de salinité que lorsque que le stress hydrique augmente. D’autre part la combinaison des méthodes observationnelle et expérimentale nous a permis de démontrer que l’augmentation de la facilitation prédite par le SGH lors d’une augmentation modérée de stress hydrique n’est qu’une réponse des plantes à l’effet négatif croissant de l’environnement abiotique, contrairement à l’augmentation de la compétition dans les environnements non stressés et celui de la facilitation des environnements très à moyennement stressés, qui sont des processus d’origine biotique.
(14/12/2020)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Processus sédimentaires actuels et évolution morphologique associée du canyon de Capbreton : description, observation et modélisation.
Le canyon sous-marin de Capbreton, au sud-est du golfe de Gascogne, forme une profonde incision à travers le plateau et le talus continental. Son activité sédimentaire est abondamment décrite et documentée, cependant, de nombreuses questions subsistent concernant le détail des processus affectant le transfert des sédiments de l’amont vers l’aval. Cette étude est basée sur l'analyse et la comparaison de relevés bathymétriques répétés, entre 1998 et 2018, à des profondeurs allant de 10 à 1500 m. Cette rare série temporelle met en évidence une évolution morphologique rapide, répondant à son activité actuelle. Elle est marquée par l'alternance entre des périodes de remplissage et d'érosion à l'axe du canyon, et un dépôt continu de sédiments dans la tête du canyon au cours des 20 dernières années. Le creusement du talweg est induit par l'érosion liée au recul de knickpoints migrant régulièrement vers l'amont du système. Il est également démontré que l'obstruction partielle des chenaux, dans les méandres serrés, précède l'initiation de nouveaux knickpoints. L'étude, complétée par l'analyse de données de courantomètres ADCP, de séries temporelles météorologiques et de prélèvements sédimentaires, met en évidence le lien entre les conditions météorologiques et l’hydrodynamique du canyon. Pour la première fois dans le canyon de Capbreton, plusieurs forts courants de turbidités ont été enregistrés (1 m/s en vitesse locale et 6,5 m/s en vitesse de front estimée), des ondes quasi-inertielles ont été mises en évidence. Il est démontré que les tempêtes sont l'un des principaux facteurs déclenchant ces courants, qui tous deux contrôlent fortement la dynamique sédimentaire du canyon. La modélisation numérique nous permet de discuter de l'alimentation du canyon à partir des écoulements générés à sa tête. Les courant simulés indiquent qu'un apport de sédiments fins est nécessaire pour générer des écoulements le long du canyon. Les sédiments grossiers (sables) et leurs dépôts se déposent rapidement et ne progressent que par la récurrence des évènements.
(11/12/2020)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Streamlining Data and Service Centers for Easier Access to Data and Analytical Services: The Strategy of ODATIS as the Gateway to French Marine Data
The past few decades have seen a marked acceleration in the amount of marine observation data derived using both in situ and remote sensing measurements. For example, high-frequency monitoring of key physical-chemical parameters has become an essential tool for assessing natural and human-induced changes in coastal waters as well as their consequences on society. The number and variety of data acquisition techniques require efficient methods of improving data availability. The challenge is to make ocean data available via interoperable portals, which facilitate data sharing according to Findable, Accessible, Interoperable, and Reusable (FAIR) principles for producers and users. Ocean DAta Information and Services (ODATIS) aims to become a unique gateway to all French marine data, regardless of the discipline (e.g., physics, chemistry, biogeochemistry, biology, sedimentology). ODATIS is the ocean cluster of the Data Terra research infrastructure for Earth data, which relies on a network of data and service centers (DSC) supported by the major French oceanic research organizations (CNRS, CNES, Ifremer, IRD, SHOM; Marine Universities). ODATIS, through its components, is involved in European and international initiatives such as Copernicus, SeaDataCloud, and EMODnet. The first challenge of ODATIS is to catalog all open ocean and coastal data and facilitate data collection and access (discovery, visualization, extraction) through its web portal. A specific task is to develop tools for handling large amounts of data and generate products for policymakers, practitioners, and academics. This study presents the strategy used by ODATIS to implement the FAIR and CoreTrustSeal requirements in each of its DSCs and promote adherence within the scientific community (the main data producer) regarding the upload and/or usenof data and suggestion of new products. A second challenge is to cover the enduser needs ranging from proximity to the producer to cross-analysis of data from all Earth compartments. This involves defining and organizing a classification of DSCs in the network, which will be developed within the framework of the French Data Terra research infrastructure, the only framework capable of providing the necessary IT and human resources.
(Frontiers in Marine Science. vol. 7, n° 2296-7745, 11/12/2020)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Etude de la dynamique instationnaire des vagues et des circulations associées en milieu littoral
Les littoraux dominés par l'action des vagues sont soumis à des forçages hydrodynamiques très intenses et sujets à de forts aléas naturels, tels que l'érosion côtière et la submersion marine. Il est ainsi essentiel de mieux comprendre l'impact des événements extrêmes à la côte. Pour cela, nous avons d'abord comparé les méthodes existantes pour reconstruire la surface libre des vagues à partir de la mesure in situ de pression au fond. Les méthodes classiquement utilisées ne permettent pas de correctement reproduire la hauteur et la forme des vagues extrêmes. A l'inverse, des méthodes non-linéaires récemment développées permettent de bien les reproduire et constituent donc un outil performant pour la mesure in situ des vagues extrêmes en zone littorale. Afin de mieux comprendre la dynamique des circulations induites par les vagues le long de caps rocheux, des mesures in situ haute-fréquences ont été collectées durant 3 semaines (Octobre 2018) sur la plage de la Petite Chambre d'Amour (PCA) à Anglet (France). Une analyse détaillée montre que les schémas de circulation varient selon le climat de houle. Pour des houles obliques très énergétiques, un courant de cap intense, modulé par la marée, et s'étendant à O(100) m au large est mesuré. L'intensité de ce courant est sujet à des fluctuations horaires, amplifiant son intensité jusqu'à 2-3 fois sa valeur moyenne. Le modèle hydrodynamique XBeach est utilisé pour mieux appréhender la structure spatio-temporelle des courants de cap à PCA. Le modèle calibré et validé confirme que ces courants couvrent de larges échelles spatiales et suggère un fort couplage hydrodynamique de part et d'autre du cap. Notre étude expérimentale et de modélisation indique que les courants de cap de déflection agissent comme des conduits permanents pouvant transporter au large des matières en surface ainsi que des sédiments.
(04/12/2020)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Heterotrophic Foraminifera capable of inorganic nitrogen assimilation
Nitrogen availability often limits biological productivity in marine systems, where inorganic nitrogen, such as ammonium is assimilated into the food web by bacteria and photoautotrophic eukaryotes. Recently, ammonium assimilation was observed in kleptoplast-containing protists of the phylum foraminifera, possibly via the glutamine synthetase/glutamate synthase (GS/GOGAT) assimilation pathway imported with the kleptoplasts. However, it is not known if the ubiquitous and diverse heterotrophic protists have an innate ability for ammonium assimilation. Using stable isotope incubations (N-15-ammonium and C-13-bicarbonate) and combining transmission electron microscopy (TEM) with quantitative nanoscale secondary ion mass spectrometry (NanoSIMS) imaging, we investigated the uptake and assimilation of dissolved inorganic ammonium by two heterotrophic foraminifera; a non-kleptoplastic benthic species, Ammonia sp., and a planktonic species, Globigerina bulloides. These species are heterotrophic and not capable of photosynthesis. Accordingly, they did not assimilate C-13-bicarbonate. However, both species assimilated dissolved N-15-ammonium and incorporated it into organelles of direct importance for ontogenetic growth and development of the cell. These observations demonstrate that at least some heterotrophic protists have an innate cellular mechanism for inorganic ammonium assimilation, highlighting a newly discovered pathway for dissolved inorganic nitrogen (DIN) assimilation within the marine microbial loop.
(Frontiers in Microbiology. vol. 11, n° 1664-302X, pp. 604979, 03/12/2020)
LPG, UA, UN UFR ST, UN, INSU - CNRS, CNRS, IFREMER, EPFL, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, EPS - UC Davis, UC Davis, UC, CEOAS, OSU
Coupling historical map and sedimentological archives to rebuild the Belle-Henriette lagoon paleoenvironment
This work exposes the paleoenvironmental evolution of the Belle-Henriette lagoon and suggests a hypothesis about the infilling of the former Golfe des Pictons, in western France. Nowadays known as the Marais poitevin, this marsh is the second biggest wetland in France, covering nearly 100,000 ha. A transect composed of five sediment cores was collected in 2019 using both a Beeker gravity corer and a vibracore corer, starting from the sandy barrier to the center of the lagoon. High-resolution elemental analyses of sediment cores were done using an Avaatech XRF core scanner, and X-radiographs were taken using a Scopix system. Grain size analyses were measured at a resolution of 1 cm using a Malvern 2600 laser diffraction particle size analyzer. Dating was derived from sedimentary profiles of 137Cs and 210Pb, measured on an aliquot of 2 g dried sediment using a low background, welltype γ spectrometer (Canberra). Historical maps were extracted from the Bibliothèque François-Mitterrand and from departmental archives. Nearly fifty maps were studied to understand the composition of each detected layer and to reconstruct the historical landscape of the western part of the Marais poitevin. This work gives clues about the creation of this marsh during the last few centuries, by the infilling of the former Golfe des Pictons and the evolution of the Lay river (former St. Benoist) estuary. We also expose the creation of the Belle-Henriette lagoon during the last decade by the progradation of several coastal spits.
(02/12/2020)
CReAAH, UM, UR, UR2, CNRS, UFR HHAA, UN, MC, LARA, UN, CReAAH, UM, UR, UR2, CNRS, UFR HHAA, UN, MC, OSUNA, UA, UN UFR ST, UN, IFSTTAR, INSU - CNRS, Cnam, CNRS, IMT Atlantique, IMT, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LETG - Nantes, UNICAEN, NU, EPHE, PSL, UBO EPE, UR2, CNRS, IGARUN, UN
Microcharcoal calibration in recent marine sediments: implications to reconstruct paleofire regimes on African continent
(01/12/2020)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Fire regime changes in the Mediterranean climate region during the last 8500 last years using microcharcoal preserved in marine sediments from the Gulf of Lion
(01/12/2020)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LOCEAN-VOG, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité