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
Microplastics exposures of fish: internalization and effects on behavior and growth
Awareness of the presence of microplastics, i.e. plastic particles ranging in size from 1 μm to 5 mm, in marine and freshwaters has recently risen but detection and quantification is challenging. Furthermore, whether they pose a risk to aquatic organisms is not yet clear. Fish, for example, have been demonstrated to ingest microplastics particles but the link between quantification of uptake and impact assessment has not yet been made. In this context, we are exploring methods for particles quantification upon feeding juvenile fish with regular food and microplastics and assess whether exposure impacts behavior and growth. For quantification of uptake, we hypothesized that it is possible to analyze the fish tissue by flow cytometry in combination with viSNE, which allows the 2D clustering of particles with different features according to the fluorescence measured. Exposure experiments were carried out for up to three weeks, using different types of microplastic particles and a wide concentration range. In the flow, when particles were mixed with fish tissue, flow cytometry/viSNE was able to differentiate particles natures, numbers and sizes. About 10% of added particles were internalized by the fish from all particles that floated or settled on the bottom. Particles ingestion resulted in a slight impact on behavior. Yet, floating particles were massively incorporated by the fish and significant numbers remained even after 24h of depuration. Based on this, we are currently exploring if continuous feeding with microparticles contaminated food has consequences on juvenile fish growth. Taken together, our study demonstrates the power and limits of flow cytometry/viSNE for microplastics quantification in a complex biological matrix like fish.The setup could be extended to other types and forms of microplastics in different environmental matrices. Moreover, our study sheds light on ecological consequences that microplastics exposure might have on fish.
(13/05/2018)
EAWAG, UTOX-PCB, LRHLR, HGS, IFREMER, IFREMER, UMR MARBEC, IRD, IFREMER, UM, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Apport d’une étude transcriptomique et comportementale aux connaissances de l’impact des obstacles aquatiques sur les anguillettes migrantes
(Hydroécologie Appliquée, n° 1147-9213, 07/05/2018)
UR EABX, IRSTEA, EDF R&D LNHE, EDF R&D, EDF [E.D.F.], EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
UAV monitoring of 3-year Foredune Partial Recovery from a Severe Winter: Truc Vert Beach, SW France
The recent development of ultra-light civil UAVs and photogrammetric techniques provides new and efficient means to remotely sense the coastal topography at high spatial and temporal resolutions along spatially extensive areas. Truc Vert, SW France, is a high-energy meso-macrotidal beach backed by a preserved high and wide coastal dune system. This coastal dune system, which had been relatively stable over the last 70 years, was severely eroded during the winter of 2013/2014 with 800-m long and up to 8-m high cuspate erosion scarps. Since then, the foredune has been slowly recovering. This 3-year period was characterized, at the early stage, by the destabilisation of the scarped dune by trough blowouts, scarp slumping and filling and seasonal beach berm dynamics. The onset of foredune recovery occurred subsequently, and was characterized by the development of a dune ramp. This ramp provided efficient conduit for beach-dune delivery/exchange of sediment by the end of the study despite the high-energy winter of 2015/2016 drove localized dune erosion. The coastal dune did not fully recover with an approximately 60% average recovery within 3 years, an overall accretion due primarily to incipient foredune formation and foredune growth in height. The timing and magnitude of the incomplete recovery sequence from the UAV surveys provide an outstanding measure of coastal dune resilience to severe storms in this region of the world.
(Journal of Coastal Research. vol. 85, n° 0749-0208, pp. 276-280, 01/05/2018)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS