Premières observations de la dynamique hydro-sédimentaire de l'estuaire Maroni (Guyane)
En comparaison aux estuaires des zones tempérées, les estuaires tropicaux entourés par la mangrove sont moins connus et documentés. Dans le cadre du projet EFHEMAR financé par l’Office de l’Eau de la Guyane (2016-2018), les premières données hydromorpho-sédimentaires de l’estuaire du Maroni ont été collectées, dans le but de réaliser une description actualisée de l’estuaire, ainsi que dans le but d’alimenter un modèle en cours de développement. L’analyse des enregistrements de marée indique que l’estuaire, au moins pour sa partie aval, est convergent, avec une amplification du marnage au moins jusqu’à Crique-Vache , situé à 8 km de l’embouchure. Les courants de marée mesurés suivent les oscillations semi-diurnes de flot et de jusant ; en saison sèche ils induisent des remises en suspension de sédiments fins en amont de l’estuaire ; en saison humides ils sont complètement dominés par l’écoulement fluvial. Les mesures de salinité montrent de forts contrastes saisonniers en termes de stratification, contrôlée par le régime fluvial. En saison sèche l’estuaire est partiellement mélangé aussi bien à marée haute qu’à marée basse. En saison humide, un coin salé est bien identifié à marée haute, mais à marée basse le gradient salin est expulsé de l’estuaire. L’analyse des premières mesures de turbidité montre que des contrastes forts existent aussi en termes de concentration en matière en suspension, avec un estuaire très turbide en saison sèche, et des eaux plus claires en saison humide. Un "bouchon vaseux" semble persister près de l’embouchure en saison humide, tandis qu’en surface les eaux douces fluviales arrivent chargées en matières en suspension plus récentes.
(pp. 293-300, 31/05/2018)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEEISA, IFREMER, UG, CNRS, Cerema Direction Eau Mer et Fleuves, Cerema, Cerema Equipe-projet HA, Cerema, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS
UHAINA : A parallel high performance unstructured near-shore wave model
UHAINA is a new phase-resolving free surface wave model for coastal engineering 21 problems. It is based on the most advanced and recent contributions in coastal 22 modelling from the french institutes EPOC, IMAG, IMB, and INRIA BSO. It solves a 23 non-classical version of the depth-integrated fully-nonlinear and weakly-dispersive 24 equations of Green-Naghdi, which allows an efficient numerical implementation. 25 UHAINA relies on libraries developed at the INRIA BSO center, such as AeroSol for 26 its hydrodynamic core, and PaMPA and SCOTCH to handle data management for 27 distributed memory parallel computation. The use of these libraries, in particular 28 AeroSol, offers a wide range of possibilities including arbitrary high-order finite 29 element discretizations, hybrid meshes (structured and unstructured), as well as an 30 advanced programming environment specially designed by the purpose of performance 31 and HPC. These properties will lead in the coming years to the release of a new efficient 32 and robust open source wave modelling platform, available for a large community of 33 users and very suitable for practical coastal applications.
(. vol. 15, pp. 47-56, 29/05/2018)
CARDAMOM, IMB, UB, Bordeaux INP, CNRS, Inria, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CAGIRE, LMAP, UPPA, CNRS, Inria, LMAP, UPPA, CNRS, IMAG, UM, CNRS, IMB, UB, Bordeaux INP, CNRS
Étude comparative des méthodes de reconstruction du champ de vagues à partir de la mesure de pression : Application à la plage de La Salie
La reconstruction du champ de vagues basée sur la théorie linéaire, communément appelée méthode de la fonction de transfert, décrit assez bien les caractéristiques moyennes des vagues. Elle est couramment utilisée pour déterminer les paramètres statistiques des vagues mais sous-estime la hauteur des plus grosses vagues. Cependant, bien estimer ces vagues énergétiques est primordial pour l'étude des risques côtiers lors d'évènements extrêmes. La reconstruction linéaire nécessite l'application d'une fréquence de coupure du spectre d'énergie qui induit une perte d'information. Des techniques empiriques qui essaient de combler artificiellement le spectre d'énergie n'améliorent que très peu les plus grosses vagues. Récemment, des formules simples à implémenter permettant des reconstructions linéaires et non-linéaires ont été développées. Nous présentons et comparons dans cet article différentes méthodes de reconstruction du champ de vagues à partir de la pression mesurée au fond lors d'une campagne de mesure réalisée sur la plage de La Salie en avril 2017. Notre étude est centrée sur des vagues très non-linéaires et faiblement dispersives. Une analyse vague à vague met en évidence la capacité de la reconstruction non-linéaire faiblement dispersive à reproduire la hauteur et l'asymétrie des plus grosses vagues contrairement à la formule linéaire couramment utilisée en ingénierie côtière. Mots-clés : Théorie linéaire, non-linéarité, capteurs de pression, reconstruction du champ de vagues.
(29/05/2018)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, DMA, ENS-PSL, PSL, CNRS
Evolution of the Performances of Radar Altimetry Missions from ERS-2 to Sentinel-3A over the Inner Niger Delta
Radar altimetry provides unique information on water stages of inland hydro-systems. In this study, the performance of seven altimetry missions, among the most commonly used in land hydrology (i.e., European Remote-Sensing Satellite-2 (ERS-2), ENVIronment SATellite (ENVISAT), Satellite with Argos and ALtika (SARAL), Jason-1, Jason-2, Jason-3 and Sentinel-3A), are assessed using records from a dense in situ network composed of 19 gauge stations in the Inner Niger Delta (IND) from 1995 to 2017. Results show an overall very good agreement between altimetry-based and in situ water levels with correlation coefficient (R) greater than 0.8 in 80% of the cases and Root Mean Square Error (RMSE) lower than 0.4 m in 48% of cases. Better agreement is found for the recently launched missions such as SARAL, Jason-3 and Sentinel-3A than for former missions, indicating the advance of the use of the Ka-band for SARAL and of the Synthetic-aperture Radar (SAR) mode for Sentinel-3A. Cross-correlation analysis performed between water levels from the same altimetry mission leads to time-lags between the upstream and the downstream part of the Inner Niger Delta of around two months that can be related to the time residence of water in the drainage area.
(Remote Sensing, n° 2072-4292, 25/05/2018)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GET, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, LEGOS, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS
Platinum biogeochemical cycles in coastal environments
Platinum (Pt) is a Technology-Critical Element (TCE) and an emerging contaminant increasingly released into all Earth compartments, but its environmental occurrence, distribution, and dynamics are under- documented. The present research combines laboratory observations and field monitoring studies on Pt biogeochemistry in coastal systems (Atlantic Ocean and northwestern Mediterranean Sea), including its distribution between seawater, particles, and living organisms. Exposure experiments with oysters facing a wide range of exposure levels provide the first Pt accumulation kinetics in marine bivalves, supporting uptake of Pt from seawater in line with field observations. At environmentally-relevant Pt levels (50 and 100 ng.L-1), the positive linear relation between exposure and Pt accumulation in tissues justifies the use of oysters as integrative sentinels for seawater Pt contamination. At relatively high Pt levels (10,000 ng.L-1), deleterious physiological effects (e.g. increased oxidative stress and energetic stock mobilization) occurred in oysters. Field observations at contrasting sites have provided regional background Pt concentrations in seawater in the Atlantic and Mediterranean coasts (0.05 ng.L-1 and 0.08 ng.L-1, respectively) and bioconcentration factors for phytoplankton (~ 104), and bivalves (oysters and mussels ~ 103). Spatial distribution of Pt levels in seawater, plankton and bivalves suggest higher contamination along the northwestern Mediterranean coast, especially in semi-enclosed, industrialized/urbanized systems (Toulon Bay and Genoa Harbor). Historical records in sediments (~ 1900 - 2010) and bivalves (1980 to present) from the Gironde watershed and the Toulon Bay showed past Pt contamination due to industrial (metallurgic, oil-refining, coal) activities, whereas the strong recent increase in Pt contamination originates from emerging Pt sources, e.g. car catalytic converters, hospital effluents, and sewage. High temporal resolution observation of Pt partitioning, together with environmental master variables (O2, Salinity, Chl-a, nutrients etc.), suggests that in coastal systems, biogeochemical processes including phytoplankton production and degradation may play an important role in Pt behavior and fate.
(24/05/2018)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Les premiers stades de médaka japonais (Oryzias latipes) sont plus sensibles à l’imidaclopride que les les premiers stades de poissons zèbres (Danio rerio)
(22/05/2018)
LRHLR, HGS, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UNIL, UniMe, EAWAG
Contamination en microplastiques dans l’estuaire de la Seine
(22/05/2018)
LEESU, ENPC, UPEC UP12, LERN, COAST, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Increasing densities of an invasive polychaete enhance bioturbation with variable effects on solute fluxes
AbstractBioturbation is a key process affecting nutrient cycling in soft sediments. The invasive polychaete genus Marenzelleria spp. has established successfully throughout the Baltic Sea increasing species and functional diversity with possible density-dependent effects on bioturbation and associated solute fluxes. We tested the effects of increasing density of M. arctia, M. viridis and M. neglecta on bioturbation and solute fluxes in a laboratory experiment. Benthic communities in intact sediment cores were manipulated by adding increasing numbers of Marenzelleria spp. The results showed that Marenzelleria spp. in general enhanced all bioturbation metrics, but the effects on solute fluxes varied depending on the solute, on the density and species identity of Marenzelleria, and on the species and functional composition of the surrounding community. M. viridis and M. neglecta were more important in predicting variation in phosphate and silicate fluxes, whereas M. arctia had a larger effect on nitrogen cycling. The complex direct and indirect pathways indicate the importance of considering the whole community and not just species in isolation in the experimental studies. Including these interactions provides a way forward regarding our understanding of the complex ecosystem effects of invasive species.
(Scientific Reports. vol. 8, n° 2045-2322, 16/05/2018)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Impact of three pesticides on Gomphonema gracile's fatty acids
Fatty acids are essential elements for the structure of biological membranes and for the storage of metabolic energy. They are used as a source of energy by metabolism at each trophic level, making fatty acids biochemically and physiologically important compounds (Neves et al. 2015). In the trophic chain, many fatty acids are only synthesized by microalgae and bacteria before being transferred via herbivorous invertebrates to fish and ultimately to humans (Arts et al. 2001). For example, highly unsaturated fatty acids (HUFA) such as eicosapentaenoic acid (EPA; C20:5n3), can not be synthesized de novo or in insufficient proportions by animals (Saito and Aono 2014). That is why fatty acid analysis is commonly used to study trophic interactions in food chains. Generally, microalgae with a high proportion of EPA, such as diatoms, are an excellent source of food for animals but the concentrations of these different fatty acids can vary according to the stage of growth of the organism and according to different environmental parameters including pesticide exposure (Brett et al. 2006, Robert et al. 2007, Burns et al. 2011, Filimonova et al. 2016). Moreover, for several years, the intensive use of pesticides caused many problems to the environment, making pesticides major pollutants of aquatic ecosystems (Aydinalp and Porca 2004). The aim of this study is to investigate the impact of 3 pesticides on diatom's fatty acids. To address this issue, a model freshwater diatom (Gomphonema gracile) was exposed to three herbicides, with three different cellular targets, at environmentally relevant and higher concentrations (diuron and S-metolachlor, C1= 1 µg/L and C2= 10 µg/L; glyphosate, C1= 5 µg/L and C2= 50 µg/L). After a 1-week exposure, fatty acid compositions of diatoms were determined by gas chromatography. In comparison with control samples the percentage of 1) polyunsaturated fatty acids (PUFA) decreased with S-metolachlor contamination (C2); 2) saturated fatty acid (SFA) and monounsaturated (MUFA) decreased with diuron and glyphosate exposure (C2). The decrease of PUFA is a direct impact and can be explained by the mode of action of S-metolachlor which inhibits elongases. Concerning diuron and glyphosate, the decrease of SFA and MUFA can reflect an indirect effect, which can be explained by the mode of action of these two pesticides which respectively blocks electron transfer in photosynthesis, and inhibits the synthesis of aromatic aminoacids.
(pp. 1, 13/05/2018)
UR EABX, IRSTEA, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Low Cost Diode as Selector Device for Embedded Phase Change Memory in Advanced FD-SOI Technology
This paper presents a new diode selector for embedded Phase Cahnge Memory (PCM) in advanced FD-SOI technology. It has been developed to achieve a very low cost selector device but still very efficient to meet PCM specifications. This new device takes advantages of CMOS in FD-SOI: buried oxide (BOX), shallow trench isolation (STI) and high k metal gates allow very low leakages between cells, thus offering great potential for designing embedded memory arrays of up to several Mbit. The selector can drive 300μA at 2V through the memory cell with 2.5V applied on gates together with a limited leakage current of less than 10pA/cell. The effective cell area of under 0.025μm 2 is very competitive as compared to a MOS selector, offering a size reduction of around 60% for the same drinving current. Therefore, the new diode on FD-SOI devices is a great solution for a PCM selector due to its low cost and high density.
(13/05/2018)
ST-ROUSSET, IM2NP, AMU, UTLN, CNRS, INL - DE, INL, ECL, UCBL, CPE, INSA Lyon, INSA, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ST-CROLLES