Performance of the VLT Planet Finder SPHERE II. Data analysis and results for IFS in laboratory
Aims. We present the performance of the Integral Field Spectrograph (IFS) of SPHERE, the high-contrast imager for the ESO VLT telescope designed to perform imaging and spectroscopy of extrasolar planets, obtained from tests performed at the Institut de Planetologie et d'Astrophysique de Grenoble facility during the integration phase of the instrument. Methods. The tests were performed using the instrument software purposely prepared for SPHERE. The output data were reduced applying the SPHERE data reduction and handling software, adding an improved spectral deconvolution procedure. To this aim, we prepared an alternative procedure for the spectral subtraction exploiting the principal component analysis algorithm. Moreover, a simulated angular differential imaging procedure was also implemented to estimate how the instrument performed once this procedure was applied at telescope. The capability of the IFS to faithfully retrieve the spectra of the detected faint companions was also considered. Results. We found that the application of the updated version of the spectral deconvolution procedure alone, when the algorithm throughput is properly taken into account, gives us a 5 sigma limiting contrast of the order of 5 x 10(-6) or slightly better. The further application of the angular differential imaging procedure on these data should allow us to improve the contrast by one order of magnitude down to around 7x10(-7) at a separation of 0.3 arcsec. The application of a principal component analysis procedure that simultaneously uses spectral and angular data gives comparable results. Finally, we found that the reproducibility of the spectra of the detected faint companions is greatly improved when angular differential imaging is applied in addition to the spectral deconvolution.
(Astronomy & Astrophysics - A&A. vol. 576, n° 0004-6361, 01/04/2015)
GSFC, IPAG, OSUG, UJF, Grenoble INP, INSU - CNRS, IRSTEA, USMB [Université de Savoie] [Université de Chambéry], CNRS, INSU - CNRS, CNES, CNRS, OAPD, INAF, LAM, AMU, INSU - CNRS, CNES, CNRS, ObsGE, UNIGE, LAGRANGE, UNS, INSU - CNRS, UniCA, CNRS, UniCA, LESIA, UPMC, INSU - CNRS, CNRS, PSL, UPD7, CNRS, MPIA, TUM, CRAL, ENS de Lyon, UCBL, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CFHT, INSU - CNRS, NRC, CNRS, UH
Potential denitrification rates are spatially linked to colonization patterns of nosZ genotypes in an alluvial wetland
Through denitrification, attached bacterial communities reduce water nitrogen loads during transport from land to river. In an in situ colonization experiment, spatial and temporal dynamics in composition of bacterial communities and denitrification activity were studied in bacterial biofilms in an alluvial aquifer. Mesh bags with glass beads were installed in different wells in an alluvial aquifer affected by surface water fluxes from an adjacent river and biofilms were sampled throughout the 15-month experiment. By combining structural (PCR-DGGE using nosZ genes) and functional (Denitrification Enzyme Activity measurements) descriptors, the denitrifiers community structure of biofilms and their functional responses were studied. Denitrifiers bacterial community composition developed on beads linked to denitrification capability were correlated with the modeled load of dissolved organic carbon coming from the river and dissolved oxygen concentration, which were set by the river channel water flow through the aquifer.
(Ecological Engineering. vol. 80, n° 0925-8574, pp. 191-197, 18/03/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Decadal Changes in South Pacific Sea Surface Temperatures and the Relationship to the Pacific Decadal Oscillation and Upper Ocean Heat Content: Decadal Changes in South Pacific SST
Decadal changes in Pacific sea surface temperatures (SST) and upper ocean heat content (OHC) remain poorly understood. We present an annual average composite coral Sr/Ca-derived SST time-series extending back to 1791 from Fiji, Tonga and Rarotonga (FTR) in the Pacific Decadal Oscillation (PDO) sensitive region of the Southwest Pacific. Decadal SST maxima between 1805 and 1830 C.E. indicate unexplained elevated SSTs near the end of the Little Ice Age. The mean period of decadal SST variability in this region has a period near 25 years. Decades of warmer (cooler) FTR SST co-occur with PDO negative (positive) phases since at least ~1930 C.E. and positively correlate with South Pacific OHC (0-700m). FTR SST is also inversely correlated with decadal changes in equatorial Pacific SST as measured by coral Sr/Ca. Collectively, these results support the fluctuating trade wind-shallow meridional overturning cell mechanism for decadal modulation of Pacific SSTs and OHC.
(Geophysical Research Letters. vol. 42, n° 0094-8276, pp. 2358-2366, 01/03/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Modeling water quality in an urban river using hydrological factors – Data driven approaches
Contrasting seasonal variations occur in river flow and water quality as a result of short duration, severe intensity storms and typhoons in Taiwan. Sudden changes in river flow caused by impending extreme events may impose serious degradation on river water quality and fateful impacts on ecosystems. Water quality is measured in a monthly/quarterly scale, and therefore an estimation of water quality in a daily scale would be of good help for timely river pollution management. This study proposes a systematic analysis scheme (SAS) to assess the spatio-temporal interrelation of water quality in an urban river and construct water quality estimation models using two static and one dynamic artificial neural networks (ANNs) coupled with the Gamma test (GT) based on water quality, hydrological and economic data. The Dahan River basin in Taiwan is the study area. Ammonia nitrogen (NH3–N) is considered as the representative parameter, a correlative indicator in judging the contamination level over the study. Key factors the most closely related to the representative parameter (NH3–N) are extracted by the Gamma test for modeling NH3–N concentration, and as a result, four hydrological factors (discharge, days w/o discharge, water temperature and rainfall) are identified as model inputs. The modeling results demonstrate that the nonlinear autoregressive with exogenous input (NARX) network furnished with recurrent connections can accurately estimate NH3–N concentration with a very high coefficient of efficiency value (0.926) and a low RMSE value (0.386 mg/l). Besides, the NARX network can suitably catch peak values that mainly occur in dry periods (September–April in the study area), which is particularly important to water pollution treatment. The proposed SAS suggests a promising approach to reliably modeling the spatio-temporal NH3–N concentration based solely on hydrological data, without using water quality sampling data. It is worth noticing that such estimation can be made in a much shorter time interval of interest (span from a monthly scale to a daily scale) because hydrological data are long-term collected in a daily scale. The proposed SAS favorably makes NH3–N concentration estimation much easier (with only hydrological field sampling) and more efficient (in shorter time intervals), which can substantially help river managers interpret and estimate water quality responses to natural and/or manmade pollution in a more effective and timely way for river pollution management.
(Journal of Environmental Management. vol. 151, n° 0301-4797, pp. 87-96, 01/03/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Influences of major flood sediment inputs on sedimentary and geochemical signals archived in a reservoir core (Upper Loire Basin, France)
(CATENA. vol. 126, n° 0341-8162, pp. 75 - 85, 01/03/2015)
GéHCO, UT, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GEDI, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
Toxicity of sediment-bound pollutants in the Seine estuary, France, using a Eurytemora affinis larval bioassay
Coastal urbanisation exposes surrounding estuarine environments to urban-related contaminants such as polycyclic aromatic hydrocarbons (PAHs), polychlorobiphenyls (PCBs) and pesticide mixtures. Hydrophobic contaminants can adsorb on estuarine sediments. They can subsequently be released on a massive scale in the aquatic environment due to artificial or natural phenomena (e.g. dredging, tides), thereby threatening living organisms. The contamination of sediment is a significant ecological issue in the Seine estuary, France. However, few relevant methods have been developed to assess sediment toxicity and its ecological impacts in a cost-effective way. In this context, we aimed to assess the toxicity of natural sediments from the Seine estuary on the development of the calanoid copepod Eurytemora affinis using a previously developed larval bioassay. This assay involves direct exposure of nauplii to elutriates of sediments for six days. Sediments were collected along the Seine estuary from six polluted sites and one reference site. Pollutants in this estuary included PAHs, PCBs and OCPs (organochlorine pesticides). Nauplius survival was significantly more affected by exposure to all contaminated sediment elutriates, than by exposure to sediment from Yville-sur-Seine (the reference site), whereas nauplius growth was significantly reduced after exposure to contaminated sediment elutriates from four of the six contaminated sites. We identified two distinct site clusters, one including both the sand-rich and the least polluted sediments (Oissel, Quillebeuf-sur-Seine, Caudebec-en-Caux) and the other including both the clay- and silt-rich, and the most polluted sediments (La Bouille, Poses, Pont de Normandie). As expected, survival was significantly more impacted after exposure to elutriates from the second cluster than from the first. This work enables (i) assessment of the toxicity of natural sediments in the Seine estuary and (ii) validation of the larval bioassay previously developed using sorbed sediment with model molecules.
(Ecotoxicology and Environmental Safety. vol. 113, n° 0147-6513, pp. 169-175, 01/03/2015)
LEMA, ULH, NU, SEBIO, INERIS, URCA, ULH, NU, URCA, CNRS, GABI, INRA, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Differential effects of contrasting phenotypes of a foundation legume shrub drive plant-plant interactions in a Mediterranean mountain
QuestionsAre variable effects of different phenotypes of foundation plant species on subordinates across contrasting habitat conditions (with varying stress and disturbance levels) due to either varying environmental conditions or heritable differences in traits between phenotypes? To evaluate the contribution of environmental effects we quantified the effects of contrasting phenotypes of a foundation legume shrub on their subordinate species across exposure (drought stress) and grazing conditions. LocationA sub-alpine xerophytic community of western Mount Lebanon, Lebanon. MethodsFor two phenotypes of the spiny cushion shrub Onobrychis cornuta, a facilitative phenotype that occurs in concave topographies (mesic soil) and a competitive phenotype that occurs in convex topographies (xeric soil), we quantified cushion traits, environmental conditions and subordinate plant species abundances (within and outside the cushions) for the two phenotypes in northern (low stress) and southern (high stress) exposures, and with and without grazing. Relative interaction index (RII) for subordinate species richness and abundance was calculated in the eight treatment combinations and a correspondence analysis (CA) was conducted on species composition. ResultsDrought stress exacerbated phenotypic effects in southern exposure, with loose phenotypes being more facilitative and tight phenotypes more competitive than in northern exposure. This was related to both changes in cushion traits of the two phenotypes and to an increase in the pool of subordinate species sensitive to cushion effects. In contrast, grazing increased cushion positive effects of both phenotypes through the occurrence of indirect facilitation, with loose phenotypes becoming more facilitative and tight phenotypes less competitive. This was due both to changes in cushion traits of the two phenotypes and to their shared spiny phenotype limiting grazing effects. ConclusionsBecause increasing stress from northern to southern exposure did not increase competitive effects of either phenotype, and because the cessation of grazing did not cancel out differences in facilitative effects between phenotypes, neither drought stress nor grazing disturbance appeared to be the main drivers of the observed phenotypic effects on subordinate species across habitats. We conclude that differences in phenotypic effects of this legume shrub are very likely due to heritable differences in traits between phenotypes.
(Journal of Vegetation Science. vol. 26, n° 1100-9233, pp. 373--384, 01/03/2015)
BioGeCo, INRA, UB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IMBE, AU, AMU, CNRS, AMU, IRD, AU
Forecasted coral reef decline in marine biodiversity hotspots under climate change
Coral bleaching events threaten coral reef habitats globally and cause severe declines of local biodiversity and productivity. Related to high sea surface temperatures (SST), bleaching events are expected to increase as a consequence of future global warming. However, response to climate change is still uncertain as future low-latitude climatic conditions have no present-day analogue. Sea surface temperatures during the Eocene epoch were warmer than forecasted changes for the coming century, and distributions of corals during the Eocene may help to inform models forecasting the future of coral reefs. We coupled contemporary and Eocene coral occurrences with information on their respective climatic conditions to model the thermal niche of coral reefs and its potential response to projected climate change. We found that under the RCP8.5 climate change scenario, the global suitability for coral reefs may increase up to 16% by 2100, mostly due to improved suitability of higher latitudes. In contrast, in its current range, coral reef suitability may decrease up to 46% by 2100. Reduction in thermal suitability will be most severe in biodiversity hotspots, especially in the Indo-Australian Archipelago. Our results suggest that many contemporary hotspots for coral reefs, including those that have been refugia in the past, spatially mismatch with future suitable areas for coral reefs posing challenges to conservation actions under climate change.
(Global Change Biology, n° 1354-1013, pp. Epub ahead of print, 01/03/2015)
Ecosym, UM1, UM2, IFREMER, CNRS, CESAB, FRB, CRIOBE, UPVD, EPHE, PSL, CNRS, DMI, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LabEX CORAIL, IRD, UAG, EHESS, EPHE, PSL, IFREMER, UR, UPF, UNC, UA, JCU
Study of the present state and of recent temporal changes in the benthic macrofauna composition of Gulf of Lions soft-bottoms macrobenthic communities, NW Mediterranean
My main aims consisted in: (1) assessing the present state and recent (1998-2010)changes in benthic macrofauna composition of the Gulf of Lions soft-bottom communities through the long term comparison of 91 stations; (2) testing the current paradigm regarding the control of those communities by climatic parameters through a 10-year monitoring of 4 stations located in the Bay of Banyuls-sur-Mer; (3) assessing the influence of Rhône River inputs on the composition of benthic macrofauna through the sampling, of 5 stations , under 4 hydrological regimes; and (4) updating the ecological quality status of Gulf of Lions benthic habitats. My results have shown the persistence ofthe same 3 communities between 1998 and 2010, the strong influence of both the NAO and the Rhône River on benthic macrofauna composition in the whole Gulf. They also showed a control of benthic macrofauna by climatic oscillations with the WeMO contributing most especially during wintert ime. Moreover, the stations most impacted by Rhône River inputs were located close to its mouth. They are negatively affected during floods and positively affected during dry periods. Lastly, Ihave updated the sensitivity/tolerance levels of Mediterranean species and confirmed the existence of major discrepancies in the results derived from different biotic indices used, although all tested indices indicated an overall stability in the ecological quality status of benthic habitats between 1998 and 2010.
(26/02/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Développement d'échantillonneurs passifs de type POCIS pour l'évaluation de la contamination en pesticides des eaux de bassins versants languedociens
Malgré une sensible baisse des ventes depuis quelques années, la France reste le premier utilisateur européen de phytosanitaires. Ceci n’est pas sans conséquences sur l’environnement et les organismes non visés par ces produits. De nombreuses études ont permis d’une part de mieux comprendre les phénomènes de transfert des pesticides dans les compartiments eau-air sols et d’autre part de mettre en évidence leur contamination. Les données concernant l’eau sont plus nombreuses du fait de son statut de réceptacle ultime des pollutions.et des normes établies par les textes réglementaires. La Directive Cadre européenne sur l’Eau (DCE) adoptée en 2000 vise à atteindre le bon état chimique et écologique des eaux d’ici 2015 avec une obligation de résultats. Le bon état chimique dépend du respect des normes de qualité environnementales (NQE) établies notamment pour 24 pesticides. En 2012, 5% des points de mesure en cours d’eau et 19% des points de mesure en eaux souterraines ne respectent pas ces NQE.Le Languedoc Roussillon est depuis de nombreuses années la première région viticole de France et souffre d’une pression phytosanitaire importante. En 2014, un rapport de l’Agence Régionale de Santé (ARS) fait même état de l’utilisation encore récente de pesticides interdits (simazine, terbuthylazine…) depuis le début des années 2000. L’ARS a de plus affirmé que la plupart des cas de non-conformité avérés pouvaient être rattachés à la présence d’activité agricole dans le bassin versant du captage.Remédier à ces contaminations passe par le suivi de la qualité des eaux et la caractérisation de la pollution. Les outils actuels s’avèrent ne pas être toujours représentatifs de cette pollution ;de nouveaux outils sont donc mis au point. L’étude présentée ici porte sur l’utilisation de l’échantillonnage passif de type POCIS (Polar Organic Chemical Integrative Sampler) pour le suivi de la contamination en pesticides de trois bassins versants languedociens : Paulhan,Puissalicon, Roujan.Dans un premier temps, l’étude des limites possibles du dispositif POCIS a été faite pour évaluer son applicabilité dans les conditions d’exposition imposées par le terrain. Le comportement des molécules au sein de l’outil a été étudié pour une meilleure compréhension des phénomènes de diffusion qui s’y produisent. Ces études ont mené à la mise en place de calibrations en laboratoire en conditions contrôlées. [...] La mise en place des dispositifs POCIS sur les trois sites d’études a mis en évidence la prédominance de pesticides utilisés en viticulture et a montré tout l’intérêt de l’outil d’un point de vue qualitatif. La comparaison de l’outil avec l’échantillonnage automatisé montre des disparités entre concentration réelle et concentration estimée via le POCIS. Ce dernier reste à améliorer d’un point de vue quantitatif pour obtenir un échantillonneur fiable et robuste pour ce type de milieu d’exposition.
(23/02/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS