Etude des impacts toxiques des contaminants chimiques du Bassin d'Arcachon sur l'huitre cultivée Crassostrea gigas : Approche in-situ et expérimentale
Le bassin d’Arcachon est une lagune semi-fermée qui concentre de forts enjeux économiques grâce à la pratique de l’ostréiculture. Cette activité est affectée depuis une trentaine d’années par des phénomènes de mortalités estivales, et plus récemment par des surmortalités du naissain. Ces travaux se sont intéressés au rôle des polluants majeurs du bassin d’Arcachon dans ce contexte de crise en étudiant leurs effets sur la biologie de Crassostrea gigas. Une approche in situ a d’abord été adoptée afin d’identifier les contaminants les plus présents dans le milieu naturel. Des opérations de transplantation d’huîtres et des prélèvements de sédiments ont permis de quantifier divers contaminants et d’associer leur présence à des réponses biologiques. Les polluants ainsi identifiés ont ensuite été employés en conditions contrôlées au laboratoire. Trois expérimentations ont été réalisées : la première concerne l’étude des voies de contamination par le tributylétain ; la seconde concerne les effets des pesticides et du cuivre ; la troisième concerne l’effet des HAP sur des huîtres diploïdes et triploïdes. Nos résultats indiquent que les organismes transplantés au coeur de la lagune sont plus exposés aux polluants, en lien avec les caractéristiques hydrodynamiques du système. La plupart des paramètres biologiques étudiés sur le terrain ont par ailleurs montré une saisonnalité liée aux processus de gamétogenèse. Au laboratoire, la plupart des contaminants testés ont induit une réponse adaptative chez les huîtres exposées. Notre étude souligne l’importance de coupler approche de terrain et approche expérimentale pour comprendre le fonctionnement des écosystèmes côtiers.
(19/02/2014)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Facilitative plant interactions and climate simultaneously drive alpine plant diversity
Interactions among species determine local-scale diversity, but local interactions are thought to have minor effects at larger scales. However, quantitative comparisons of the importance of biotic interactions relative to other drivers are rarely made at larger scales. Using a data set spanning 78 sites and five continents, we assessed the relative importance of biotic interactions and climate in determining plant diversity in alpine ecosystems dominated by nurse-plant cushion species. Climate variables related with water balance showed the highest correlation with richness at the global scale. Strikingly, although the effect of cushion species on diversity was lower than that of climate, its contribution was still substantial. In particular, cushion species enhanced species richness more in systems with inherently impoverished local diversity. Nurse species appear to act as a ‘safety net’ sustaining diversity under harsh conditions, demonstrating that climate and species interactions should be integrated when predicting future biodiversity effects of climate change.
(Ecology Letters. vol. 17, n° 1461-023X, pp. 193-202, 01/02/2014)
UdeC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IEU, UZH, UMR AMAP, Cirad, INRA, UM, CNRS, IRD [Occitanie], IRD, WSL
Brown muscle disease: impact on Manila clam Venerupis (=Ruditapes) philippinarum biology.
This study assessed the effect of Brown Muscle Disease (BMD) on Manila clam Venerupis philippinarum fitness. BMD was discovered in 2005. It affects the posterior adductor muscle and leads to clam gaping and eventually death. Three statuses of clams were compared: buried individuals with no signs of BMD (BUR); clams at the surface of the sediment with no signs of BMD (SURF) and clams at the surface of the sediment exhibiting signs of brown muscle disease (BMD). Physiological (condition index), immune (hemocyte parameters) and molecular (gene expressions) parameters collected seasonally were analyzed and compared. Results demonstrated a seasonal pattern in condition index (CI) with peaks in spring/summer and decreases in autumn/winter. At each season, the highest CI was observed in BUR and the lowest CI was observed in BMD. In terms of immune response, phagocytosis rate and capacity were higher in clams with BMD whereas the health status of the clams did not influence the total hemocyte count. Genes involved in the immune system (comp, tnf, inter) were upregulated in clams with BMD. The molecular analysis of gill and posterior muscle showed higher mitochondrial metabolism (cox-1, 16S) in cells of infected clams, suggesting a stronger energetic demand by these cells. Finally, genes involved in oxidative stress response (cat, sod), detoxification (mt) and DNA repair (gadd45) were also overexpressed due to reactive oxygen species production. Most of the studied parameters underlined a cause-effect correlation between Manila clam health status (BUR, SUR, BMD) and physiological parameters. An important stress response was observed in BMD-infected clams at different scales, i.e. condition index, immune parameters and stress-related gene expression.
(Fish and Shellfish Immunology. vol. 36, n° 1050-4648, pp. 510-518, 01/02/2014)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEMAR, IRD, IFREMER, UBO EPE, CNRS
Millimeter-Wave Miniaturized Couplers Integrated on BiCMOS Technology
In this article, we present a new wideband hybrid coupler for millimeter‐wave applications realized in the BiCMOS9MW 130‐nm process from STMicroelectronics. The fabrication of two slightly different couplers demonstrates the wideband performance associated with miniaturized size, thanks to the use of meandered transmission lines and lumped capacitors. The best coupler provides a −10‐dB matching bandwidth of 42% with an insertion loss of 0.6 dB and a phase shift of 88° at 60 GHz. The amplitude imbalance and the phase imbalance stay, respectively, within ±1 dB and ±5° over 27 and 36%. These state‐of‐the‐art results are compared to recently published results obtained with comparable hybrid couplers
(Microwave and Optical Technology Letters. vol. 56, n° 0895-2477, pp. 587-590, 28/01/2014)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEAT, UNS, CNRS, UniCA, ST-CROLLES
Etude pluridisciplinaire d’une perturbation industrielle dans l’estuaire de la Gironde : implications du transport et de la dynamique de dégradation des débris végétaux sur le fonctionnement de la source froide du CNPE du Blayais
Jusqu’à présent, la dynamique des fractions végétales n’avait jamais été étudiée dans les estuaires macrotidaux en raison de leur faible quantité, par rapports aux fortes charges en matières en suspension fines, et du manque de protocoles d’étude et d’échantillonnage adéquats. Les débris végétaux sont toutefois à l’origine de perturbations d’activités économiques qui impliquent la filtration de larges volumes d’eau. L’objectif de cette thèse était ainsi de comprendre la dynamique d’apport et de transit de ces débris végétaux dans l’estuaire de la Gironde par la mise en oeuvre d’un suivi spatio-temporel de leur distribution et de techniques nouvelles pour un tel estuaire hyper-turbide (incubations in-situ litter-bag, caractérisation biogéochimique, identification des sources). Les résultats principaux sont la mise en évidence du contrôle du régime hydrologique sur leur distribution et la détermination des échelles de temps de leur persistance dans l’estuaire de la Gironde.
(24/01/2014)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Amazon River carbon dioxide outgassing fuelled by wetlands
River systems connect the terrestrial biosphere, the atmosphere and the ocean in the global carbon cycle. A recent estimate suggests that up to 3 petagrams of carbon per year could be emitted as carbon dioxide (CO2) from global inland waters, offsetting the carbon uptake by terrestrial ecosystems. It is generally assumed that inland waters emit carbon that has been previously fixed upstream by land plant photosynthesis, then transferred to soils, and subsequently transported downstream in run-off. But at the scale of entire drainage basins, the lateral carbon fluxes carried by small rivers upstream do not account for all of the CO2 emitted from inundated areas downstream. Three-quarters of the world's flooded land consists of temporary wetlands, but the contribution of these productive ecosystems to the inland water carbon budget has been largely overlooked. Here we show that wetlands pump large amounts of atmospheric CO2 into river waters in the floodplains of the central Amazon. Flooded forests and floating vegetation export large amounts of carbon to river waters and the dissolved CO2 can be transported dozens to hundreds of kilometres downstream before being emitted. We estimate that Amazonian wetlands export half of their gross primary production to river waters as dissolved CO2 and organic carbon, compared with only a few per cent of gross primary production exported in upland (not flooded) ecosystems. Moreover, we suggest that wetland carbon export is potentially large enough to account for at least the 0.21 petagrams of carbon emitted per year as CO2 from the central Amazon River and its floodplains. Global carbon budgets should explicitly address temporary or vegetated flooded areas, because these ecosystems combine high aerial primary production with large, fast carbon export, potentially supporting a substantial fraction of CO2 evasion from inland waters.
(Nature. vol. 505, n° 0028-0836, pp. 395-398, 16/01/2014)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GET, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], ULCO, IPGP - UMR_7154, INSU - CNRS, IGN, UR, IPG Paris, CNRS, UPCité, UPCité, BOREA, MNHN, IRD, UPMC, CNRS, NIOZ
Investigating the response of cuproproteins from oysters (Crassostrea gigas) after waterborne copper exposure by metallomic and proteomic approaches
The pacific oyster (Crassostrea gigas), a good model for studying biomineralization and coastal environmental change, was used to study the expression of cuproproteins after waterborne Cu exposure (3 μg Cu L(-1)) similarly to the Arcachon Bay aquatic environment. Cuproproteins in oyster cytosols were analyzed by gel electrophoresis (non-denaturing PAGE and SDS 2-DE), laser ablation inductively coupled plasma mass spectrometry (LA-ICP MS) and electrospray ionization mass spectrometry (ESI-MS). The high molecular weight cuproproteins (identified as extracellular superoxide dismutase [Cu-Zn] (EC Cu/Zn-SOD) and l-ascorbate oxidase) in digestive glands of oysters were differentially expressed after Cu exposure. About 1.7 and 1.2-fold increase of the Cu level in EC Cu/Zn-SOD and l-ascorbate oxidase were, respectively, determined, although EC Cu/Zn-SOD was 1.6-1.9-fold down-regulated in the digestive gland of oysters after Cu exposure. At last, the role of EC Cu/Zn-SOD in protection against Cu exposure was discussed to propose possible mechanisms to better understand Cu homeostasis and/or detoxification mechanisms.
(Metallomics. vol. 6, n° 1756-5901, pp. 338, 15/01/2014)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IPREM, UPPA, INC-CNRS, CNRS
Improved Measurement Accuracy of Probe-Fed mm-Wave Antennas Using the Three Method
In this letter, we present a method to extract the scattering parameters of a microelectronic probe used to feed on-chip or in-package antennas at millimeter-wave frequencies. It is especially important to take into account these losses in the calibration procedure necessary for the extraction of the antenna gain. We are specifically demonstrating that these losses are positively or negatively impacted, depending on the impedance value of the input impedance of the antenna connected to the probe. Theory is detailed and examples are given to illustrate the importance of taking into account those losses with precision. From the S-parameters of the probe and the measurement of the reflection coefficient of the antenna, we can compute the gain from the measured realized gain. An accuracy improvement of 15% is shown for the gain of the presented antenna.
(IEEE Antennas and Wireless Propagation Letters. vol. 13, n° 1536-1225, pp. 103-105, 06/01/2014)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEAT, UNS, CNRS, UniCA, ST-CROLLES
2000years of frequent turbidite activity in the Capbreton Canyon (Bay of Biscay)
Capbreton Canyon extends from 200 m water depth near the Aquitanian coast to 3000 m water depth before abruptly turning northward and merging with the Cap-Ferret systems. The Capbreton Canyon has been disconnected from the Adour River input since 1310 AD. Despite this situation, modern sedimentary activity is evident in the first kilometres from the head. Present sedimentation in the Capbreton Canyon was studied by combined analysis of acoustic data and cores. Cores from the topographic highs document moderate hemipelagic sedimentation and record the global climatic signal of the Bay of Biscay. Within the canyon, at±80 km from the head, on terraces bordering the thalweg at 1600 mwater depth, cores attest to recent turbidite activity.Massive medium sand is restricted to the thalweg floor, where sediment transfer dominates. Fine-grained turbidites are preferentially accumulated on the shallower terraces near the thalweg (the accumulation rate is 3 and 1 cm/year at 75 m and 125 m above the thalweg, respectively). On a higher terrace (225 m), turbidite sequences are absent or too thin to be preserved frombioturbation. The sedimentation rate is lower (approximately 0.17 cm/year) but still 10 times higher than the hemipelagic sedimentation outside the Capbreton Canyon. We demonstrate that frequent turbidity currents (1/year) are currently responsible for very high accumulation of dominantly fine-grained sediments on the terraces that are the nearest from the thalweg. We assume an impact of nepheloid layers on the sedimentation of the highest terraces. Looking for any impact on sediment supply of the disconnection of the Capbreton Canyon head from the Adour River mouth, it appears that the impact on the sedimentation affected the nature of the particles, which are less carbonate-rich, rather than the quantity of sediments. This result suggests that the longshore drift at the canyon head and hydrodynamic events are major factors in the sedimentation of Capbreton Canyon.
(Marine Geology. vol. 347, n° 0025-3227, pp. 136-152, 01/01/2014)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Neutralized Coupling Elements for MIMO Operation in 4G Mobile Terminals
A novel multiple-input-multiple-output (MIMO) dual-antenna system covering the low LTE700 and GSM850/900 communication standards is proposed for mobile terminals. The two-port antenna system is composed of two 3-D coupling elements, placed on the vertices of the short corner of a rectangular FR4 substrate. This rectangular shape emulates the printed circuit board of a modern mobile terminal. To achieve high port-to-port isolation, the neutralization technique is applied. Simulated reflection coefficients, total efficiencies, and envelope coefficient correlation are compared to measured data showing good agreement and competitive performance.
(IEEE Antennas and Wireless Propagation Letters. vol. 13, n° 1536-1225, pp. 141-144, 01/01/2014)
LEAT, UNS, CNRS, UniCA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS