Impacts des nanoplastiques et microplastiques sur les premiers stades de vie (gamètes, embryons, larves) de l'huître creuse Crassostrea gigas

For 70 years, mismanaged plastic waste accumulates in the oceans. Risk assessment of this contamination is a major concern, especially regarding micro- and presumably nanoplastics (MNP; <5 mm) which are bioavailable for most marine species. The objective of this thesis was to assess adverse effects of MNP to early life stages of the oyster Crassostrea gigas, a key engineer species in coastal ecosystems. MNP toxicity on oyster young stages depended on the particle size. The high surface area- to - volume ratio of polystyrene nanobeads (nano- PS; 50 nm) promoted their reactivity and interactions with biological membranes of gametes and embryos, leading to an inhibition of the fertilization and embryogenesis success while 0.5 and 2 μm polystyrene beads had any detectable effects. The nano-PS toxicity depended on the particle surface properties (e.g. surface functionalization and charge) which govern their aggregation in seawater and affinity with biological membranes. Furthermore, cationic nano- PS which remained at nanometric scale in seawater, had the highest toxic potential to oyster gametes and embryos. Embryonic exposure to these particles at a non-lethal dose reduced first generation larval performances and modulated larval growth at the second generation in response to the same embryonic exposure. All adverse effects were observed at supposedly unrealistic environmental concentrations (no in situ data exists on NP), suggesting low risk of polystyrene beads to oyster early life stages. Future studies will have to take into account the complexity and reality of MNP in oceans (e.g. polymer and shape diversity, concentrations, contaminants adsorption) to assess effects on bivalve species across generations in order to establish more accurately the risks for coastal environments.Depuis 70 ans, les débris plastiques dont la fin de vie a été négligée par les sociétés humaines s’accumulent dans les océans. L’évaluation des effets engendrés par cette contamination ubiquitaire est une préoccupation majeure, notamment au regard des micro- et potentiels nanoplastiques (MNP ; < 5 mm) du fait de leur biodisponibilité pour la plupart des organismes marins. L’objectif de cette thèse était de déterminer les effets des MNP sur les jeunes stades de vie d’une espèce ingénieure des habitats côtiers, l’huître creuse Crassostrea gigas. Les impacts des MNP sur ces jeunes stades sont apparus dépendants de la taille des particules. Le rapport surface/volume important des nanosphères de polystyrène (nano-PS ; 50 nm) a favorisé les interactions avec les gamètes et embryons, induisant une inhibition de la fécondation et de l’embryogénèse tandis que les microsphères (0,5 et 2 μm) n’ont causé aucun effet phénotypique visible. La toxicité des nano-PS est apparue dépendante de leurs propriétés de surface (e.g groupements chimiques, charge) qui dirigent leur agrégation dans l’eau de mer et les interactions avec les membranes biologiques. Les nano-PS cationiques, qui restent à l’échelle nanométrique dans l’eau de mer, sont à l’origine des effets toxiques les plus marqués. L’exposition embryonnaire à une dose non létale a notamment diminué les performances larvaires et modulé la réponse de la génération suivante à une réexposition embryonnaire. Toutefois, ces effets néfastes sont observés à des concentrations numéraires supposément non-représentatives de l’environnement actuel (la quantité de NP n’étant pas caractérisée en mer à ce jour), suggérant un risque limité des micro- et nanosphères de polystyrène sur les jeunes stades de C.gigas. Les prochaines études devront tenir compte de la complexité et de la réalité des MNP environnementaux (e.g. polymères, formes, contaminants adsorbés, concentrations) sur plusieurs générations de bivalves dans le but d’appréhender plus précisément le risque pour les écosystèmes côtiers

Impacts of micro- and nanoplastics on early life stages of the Pacific oyster Crassostrea gigas

Depuis 70 ans, les débris plastiques dont la fin de vie a été négligée par les sociétés humaines s’accumulent dans les océans. L’évaluation des effets engendrés par cette contamination ubiquitaire est une préoccupation majeure, notamment au regard des micro- et potentiels nanoplastiques (MNP ; < 5 mm) du fait de leur biodisponibilité pour la plupart des organismes marins. L’objectif de cette thèse était de déterminer les effets des MNP sur les jeunes stades de vie d’une espèce ingénieure des habitats côtiers, l’huître creuse Crassostrea gigas. Les impacts des MNP sur ces jeunes stades sont apparus dépendants de la taille des particules. Le rapport surface/volume important des nanosphères de polystyrène (nano-PS ; 50 nm) a favorisé les interactions avec les gamètes et embryons, induisant une inhibition de la fécondation et de l’embryogénèse tandis que les microsphères (0,5 et 2 μm) n’ont causé aucun effet phénotypique visible. La toxicité des nano-PS est apparue dépendante de leurs propriétés de surface (e.g groupements chimiques, charge) qui dirigent leur agrégation dans l’eau de mer et les interactions avec les membranes biologiques. Les nano-PS cationiques, qui restent à l’échelle nanométrique dans l’eau de mer, sont à l’origine des effets toxiques les plus marqués. L’exposition embryonnaire à une dose non létale a notamment diminué les performances larvaires et modulé la réponse de la génération suivante à une réexposition embryonnaire. Toutefois, ces effets néfastes sont observés à des concentrations numéraires supposément non-représentatives de l’environnement actuel (la quantité de NP n’étant pas caractérisée en mer à ce jour), suggérant un risque limité des micro- et nanosphères de polystyrène sur les jeunes stades de C.gigas. Les prochaines études devront tenir compte de la complexité et de la réalité des MNP environnementaux (e.g. polymères, formes, contaminants adsorbés, concentrations) sur plusieurs générations de bivalves dans le but d’appréhender plus précisément le risque pour les écosystèmes côtiers.For 70 years, mismanaged plastic waste accumulates in the oceans. Risk assessment of this contamination is a major concern, especially regarding micro- and presumably nanoplastics (MNP; <5 mm) which are bioavailable for most marine species. The objective of this thesis was to assess adverse effects of MNP to early life stages of the oyster Crassostrea gigas, a key engineer species in coastal ecosystems. MNP toxicity on oyster young stages depended on the particle size. The high surface area- to - volume ratio of polystyrene nanobeads (nano- PS; 50 nm) promoted their reactivity and interactions with biological membranes of gametes and embryos, leading to an inhibition of the fertilization and embryogenesis success while 0.5 and 2 μm polystyrene beads had any detectable effects. The nano-PS toxicity depended on the particle surface properties (e.g. surface functionalization and charge) which govern their aggregation in seawater and affinity with biological membranes. Furthermore, cationic nano- PS which remained at nanometric scale in seawater, had the highest toxic potential to oyster gametes and embryos. Embryonic exposure to these particles at a non-lethal dose reduced first generation larval performances and modulated larval growth at the second generation in response to the same embryonic exposure. All adverse effects were observed at supposedly unrealistic environmental concentrations (no in situ data exists on NP), suggesting low risk of polystyrene beads to oyster early life stages. Future studies will have to take into account the complexity and reality of MNP in oceans (e.g. polymer and shape diversity, concentrations, contaminants adsorption) to assess effects on bivalve species across generations in order to establish more accurately the risks for coastal environments

An International Comparative History of Youth Football in France and the United States (C.1920-C.2000): The Age Paradigm and the Demarcation of the Youth Game as a Separate Sector of the Sport

This thesis contends that the contemporary phenomenon of youth football is the fruit of a variety of historical developments over the twentieth century. The manner in which the junior game evolved as an independent subset of the sport in France and America was certainly exemplary of the idiosyncrasies of national sporting culture, football in particular, the general timeline of each country as well as the place of ‘youth’ in wider society. The present study aims to expand the understanding of the game of football, specifically the youth sector, through a transnational line of enquiry covering the period from circa 1920 to circa 2000. The thesis structure is broadly thematic and chronological. This comparative approach attempts to remain coherent across both countries with a goal of outlining the core issues and major shifts which occurred over the chosen period. Youth football underwent a process of demarcation from the adult or elite game but maintained and furthered specific mechanisms linking the two across sporting, educational, and professional bridges. With the decade of the 1970s serving as a turning point, the youth level achieved a sort of independence while being inextricably fused to the top level. The essence of the growing separation of the youth from the senior level rested on the fundamental notion of ‘age’ as opposed to ‘ability’. The organisation of football around this concept of ‘age’, and the resulting limitation of participation, provided a basis for ‘junior’ football as a distinct entity by the last quarter of the twentieth century. Subsequent divisions extended the differences between age categories and created a full competitive youth spectrum for younger and younger players. The game was, as a result, “juvenilized”. The registration of players and the competitions for which this registration was so important reflected the relevance of ‘age’. Throughout this process, though in different ways and at different speeds in the two countries studied, the youth game was drawn away from its roots in the school and as a pillar of the world of education. After the initial interwar and post-war eras, youth football moved toward the worlds of the club and association. This specialisation of the game was also evident in the rules and the equipment, all of which were progressively adapted for a more pedagogically correct, and perhaps commercially oriented, fit. While the youth game separated from the adult footballing world through age classification, distinct competitive spaces, adapted rules and equipment, that expanding gulf was continually bridged in various ways in order to maintain, develop, and create new links between these two increasingly distinct sectors of the sport. The link with the elite and the professional levels was certainly not new, but from the 1970s onwards it was solidified over time and the relationship grew closer as education moved farther away or, at the least, took a back seat to ‘professional training’. By the close of the twentieth century, this ultimately placed the youth game as distinct from the adult game. Yet, somewhat contradictorily, it was closer than ever to the elite professional domain. As subject to international, professional and commercial forces, the youth game was fused to elite football. These three forces pulled youth football away from their uniquely national idioms and towards a more globalized arena. Harmonizing the experience across national boundaries, a blend of educational, sporting and professional bridges ensured and furthered the connection between the youth and the adult elite player. From the late nineteenth century’s amateur world view – where football and sport were idealized as a means for development of the human being or the vehicle for the transmission of elite social values – the effects of professionalization turned football into an end in itself as a legitimate career. From child’s play to a real métier. By the end of the twentieth century, the youth game stood confidently with one foot in each world

Tire rubber chemicals reduce juvenile oyster (Crassostrea gigas) filtration and respiration under experimental conditions

International audienc

Chemical effects of different types of rubber-based products on early life stages of Pacific oyster, Crassostrea gigas

Rubber products and debris with specific chemical signatures can release their constitutive compounds into the surrounding environment. We investigated the chemical toxicity of different types of new and used rubber products (tires, crumb rubber granulates, aquaculture rubber bands) on early life stages of a model marine organism, Pacific oyster Crassostrea gigas. Leachates obtained from used products were generally less toxic than those from new ones. Leachates from new products induced embryotoxicity at different concentrations: oyster-farming rubber bands (lowest observed effect concentration, LOEC = 1 g L-1) and crumb rubber granulates (LOEC = 1 g L-1) > tires (LOEC = 10 g L-1). Moreover, new oyster-farming rubber bands induced spermiotoxicity at 10 g L-1 (-29% survival) resulting in decreased oyster reproductive output (-17% fertilization yield). Targeted chemical analyses revealed some compounds (2 mineral contaminants, 15 PAHs, 2 PCBs) in leachates, which may have played a role. Rubber used in marine aquaculture (rubber bands) or present at sea as waste (tire, crumb rubber granulates) therefore release hazardous chemical molecules under realistic conditions, which may affect oyster development. Aquaculture development work is necessary to improve practices for eco-safety, as are efforts to limit the contamination of marine environments by terrestrial rubber debris