Approche multi-proxys de la réponse des plages sableuses ouvertes aux événements de tempêtes, en incluant les phases de récupération
Cette thèse présente une étude de la dynamique des plages sableuses ouvertes dominées par la houle, au travers d’une base de données originale, couvrant une période de 29 mois, et composée de 150 levés DGPS couvrant 750m de linéaire côtier, donnant accès à la morphodynamique du site de Biscarrosse à différentes échelles de temps. Dans un premier temps, l’analyse du jeu de données à l’échelle des événements (tempêtes et successions de tempêtes appelées clusters) nous a permis de montrer que la réponse des plages sableuses aux clusters ne résulte pas de la somme des impacts induits par chaque tempête d’un cluster. Ainsi, l’effet cumulé des clusters, rapporté sur d'autres sites dans la littérature, n’est ici pas vérifié. L'impact de l’enchainement des tempêtes a également été étudié et il en résulte que lors d’un cluster, un changement des conditions hydrodynamique, à savoir, une augmentation des hauteurs de vagues et/ou du niveau d’eau, est nécessaire pour que la tempête suivante ait un impact érosif significatif sur le système. Dans un second temps, nous avons étudié la dynamique saisonnière du système plage/dune, que ce soit la saison hivernale ou estivale, dans le but de mettre en relief les principaux processus impliqués à cette échelle. Nos travaux montrent que la réponse hivernale de la plage ne dépend pas uniquement des conditions énergétiques et du profil pré-hivernal de la plage, mais également du séquençage des événements, comme lors d'un cluster. Mes travaux confirment également la nécessité de prendre en compte de nombreux paramètres dans l’étude de la dynamique hivernale des littoraux sableux : les conditions hydrodynamiques, le séquençage des évènements érosifs mais également reconstructifs, en particulier le ré-engraissement post-évènement, les transports sédimentaires cross-shore et longshore, ainsi que la position de la barre interne et des courants d’arrachements. La saison estivale est, quant-à-elle, marquée par la reconstruction de berme. Elle semble être liée à la fois aux conditions hydrodynamiques et aux caractéristiques des barres sableuses. L’étude de deux étés et deux hivers successifs a ainsi permis d’identifier les interactions entre les saisons et l’impact de la saison hivernale sur l’estivale, et l’influence de la dynamique événementielle sur la dynamique saisonnière. Elle a aussi permis de mettre en relief l’impact de l’urbanisme et des stratégies d’aménagement dans la réponse du système, à différentes échelles de temps.
(06/12/2018)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Invasive Aquatic Plants as Ecosystem Engineers in an Oligo-Mesotrophic Shallow Lake
Exotic hydrophytes are often considered as aquatic weeds, especially when forming dense mats on an originally poorly colonized environment. While management efforts and research are focused on the control and on the impacts of aquatic weeds on biodiversity, their influence on shallow lakes' biogeochemical cycles is still unwell explored. The aim of the present study is to understand whether invasive aquatic plants may affect the biogeochemistry of shallow lakes and act as ecosystem engineers. We performed a multi-year investigation (2013-2015) of dissolved biogeochemical parameters in an oligo-mesotrophic shallow lake of southwest of France (Lacanau Lake), where wind-sheltered bays are colonized by dense mats of exotic Egeria densa Planch. and Lagarosiphon major (Ridl.) Moss. We collected seasonal samples at densely vegetated and plant-free areas, in order to extrapolate and quantify the role of the presence of invasive plants on the biogeochemistry, at the macrophyte stand scale and at the lake scale. Results revealed that elevated plant biomass triggers oxygen (O 2), dissolved inorganic carbon (DIC) and nitrogen (DIN) stratification, with hypoxia events frequently occurring at the bottom of the water column. Within plants bed, elevated respiration rates generated important amounts of carbon dioxide (CO 2), methane (CH 4) and ammonium (NH 4 +). The balance between benthic nutrients regeneration and fixation into biomass results strictly connected to the seasonal lifecycle of the plants. Indeed, during summer, DIC and DIN regenerated from the sediment are quickly fixed into plant biomass and sustain elevated growth rates. On the opposite, in spring and autumn, bacterial and plant respiration overcome nutrients fixation, resulting in an excess of nutrients in the water and in the increase of carbon emission toward the atmosphere. Our study suggests that aquatic weeds may perform as ecosystem engineers, by negatively affecting local oxygenation and by stimulating nutrients regeneration.
(Frontiers in Plant Science. vol. 9, n° 1664-462X, pp. 14, 03/12/2018)
Bordeaux INP, UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BOREA, UNICAEN, NU, MNHN, IRD, SU, CNRS, UA
Advances in micropaleontology: 60th anniversary special volume
(Revue de Micropaléontologie. vol. 61, n° 0035-1598, pp. 111-112, 01/12/2018)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Interactive effects of contamination and trematode infection in cockles biochemical performance
Anthropogenic activities, especially those involving substances that pollute the environment can interfere with bivalve populations, as well as parasitism, a fundamental ecological interaction often neglected. In marine environments, organisms are concomitantly exposed to pollutants and parasites, a combination with synergistic, antagonistic or additive effects representing a potential threat to aquatic communities sustainability. In the present study, Cerastoderma edule (the edible cockle)–Himasthla elongata (trematode) was used as host–parasite model. Cockles are worldwide recognized as good sentinel and bioindicator species and can be infected by several trematodes, the most abundant macroparasites in coastal waters. Tested hypotheses were: 1) cockles exposed to increasing parasite pressure will present greater stress response; 2) cockles exposure to arsenic (single concentration test: 5.2 μg L−1) will change parasite infection success and cockles stress response to infection. Arsenic was used for being one of the most common pollutants in the world and stress response assessed using biochemical markers of glycogen content, metabolism, antioxidant activity and cellular damage. Results showed that intensity of parasite pressure was positively correlated to biochemical response, mainly represented by higher metabolic requirements. Contamination did not affect parasite infection success. Compared to arsenic, trematode infection alone exerted a stronger impact: higher glycogen storage, metabolism and cellular damage and antioxidant activity inhibition. In interaction, parasitism and arsenic reduced hosts metabolism and cellular damage. Therefore, to a certain extent and in a contamination scenario, cockles may benefit from trematode infection, working as a protection for the pollutant accumulation in the organisms, reducing overall ROS production, which can consequently led to less toxic effects. These findings highlighted the deleterious effects of trematode infection in their hosts and showed the importance of including parasitology in ecotoxicological studies.
(Environmental Pollution. vol. 243, n° 0269-7491, pp. 1469-1478, 01/12/2018)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Late Holocene record from a Loire River incised paleovalley (French inner continental shelf): Insights into regional and global forcing factors
(Palaeogeography, Palaeoclimatology, Palaeoecology. vol. 511, n° 0031-0182, pp. 12-28, 01/12/2018)
LPG-ANGERS, LPG, UA, UN UFR ST, UN, INSU - CNRS, CNRS, LPG, UA, UN UFR ST, UN, INSU - CNRS, CNRS, LETG, UNICAEN, NU, UA, EPHE, PSL, UBO EPE, UR2, CNRS, IGARUN, UN, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Protocoles de suivi stationnel des herbiers à zostères pour la Directive Cadre sur l'Eau (DCE) Zostera marina - Zostera noltei
(pp. 42 pages + annexes, 01/12/2018)
LERAR, COAST, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEMAR, IRD, IFREMER, UBO EPE, CNRS, PatriNat, MNHN, CNRS, AFB, LERBN, COAST, IFREMER, LIENSs, INSU - CNRS, ULR, CNRS
Gold nanoparticle trophic transfer from natural biofilm to grazer fish
Nanoparticle (NP) trophic transfer is reported as an important exposure route for organisms in aquatic ecosystems. This study focused on gold nanoparticle (AuNP, PEG-coated, 10 nm diameter) transfer using an experimental benthic food chain which included two trophic levels: natural river biofilm and grazer fish Hypostomus plecostomus. AuNP biofilm accumulation was assessed via water AuNP concentrations and total biofilm mass. An extended range of six AuNP concentrations in water (0, 0.0048, 0.048, 0.48, 4.8, and 48 mg Au L−1) was set. A dose-dependent relation between gold concentrations in water and natural river biofilm was observed after a 48-h exposure. This pointed out the high propensity of natural biofilms to accumulate gold. Additionally, total biofilm mass appeared to influence AuNP accumulation at the highest exposure levels. This first step enables the set-up of the transfer experiment in which grazer fish were exposed for 21 days to natural biofilms, previously contaminated by low AuNP concentrations in water (NP0.1: 0.48 and NP1: 4.8 mg Au L−1). Gold was quantified in eight fish organs, and histology was observed. Gold was transferred from biofilms to fish; bioaccumulation was organ- and exposure level-dependent. Interestingly, the brain showed significant gold accumulation at the highest exposure level (NP1). Histological observations indicated distinct inflammatory responses in fish liver, spleen, and muscle. The overall results suggest the potential hazards of subchronic nanoparticle exposure in aquatic organisms.
(Gold Bulletin : The journal of gold science, technology and applications. vol. 51, n° 2364-821X, pp. 163-173, 01/12/2018)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ICMCB, UB, INC-CNRS, CNRS, BIC, UB, INSERM, CNRS, IRSN/PRP-ENV/SERIS/LECO, IRSN/PRP-ENV/SERIS, IRSN
Distribution of living benthic foraminifera in the northern Chukchi Sea
(arktos. vol. 4, n° 2364-9453, 01/12/2018)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, NIOZ
Dinoflagellate fossils: Geological and biological applications
(Revue de Micropaléontologie. vol. 61, n° 0035-1598, pp. 235-254, 01/12/2018)
LGO, UBS, IFREMER, UBO EPE, CNRS, CR2P, MNHN, SU, CNRS, LPPP, INSU - CNRS, CNRS, DYNECO, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LERBN, COAST, IFREMER
Timing des variations du courant circum-Antarctique (ACC) dans le secteur Kerguelen pendant la dernière déglaciation
(29/11/2018)
LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, CLIMAG, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UNIL