Effects of hypoxia on the fish and crustacean fauna in the Gironde Estuary (France)
The Water Framework Directive (WFD) requires the improvement of water quality in the EU and the assessment of the transitional waters ecological status considering the fish component of the ecosystem. In the WFD, the dissolved oxygen (DO) is considered as one of the physico-chemical quality elements that support the biology and have to be monitored. Estuaries are particularly essential to fish as refuge area, habitats for reproduction, nursery grounds and migration routes but they are impacted by multiple anthropogenic disturbances. Hypoxic threshold is largely characterized by a DO content of 2 mg L-1 whereas the median lethal concentration is about 2.45 mg L-1 for aquatic organisms. Since 2005, this parameter is monitored in the Gironde Estuary thanks to the continuous monitoring MAGEST network that has recorded several summer borderline hypoxic situations (DO close to 2 mg L-1) and a 7 days-long hypoxic event (DO < 2.45 mg L-1) in July 2006 with a minimum measured value of 1.22 mg L-1. Biological responses to hypoxia depend on the period, intensity and extent of these events. Shads, Alosa fallax and Alosa alosa, and some shrimp developmental stages, are among the most sensitive species to hypoxia in the Gironde Estuary. A behavioral study was performed on shad juvenile and allowed to establish the DO threshold that could impact their downstream migration occurring from July to early October. Water temperatures in summer 2006 are the highest recorded in the period 2005-2012 with values higher than 28°C. Almost 43% of conditions (DO thresholds at 20°C and 25°C) are critical to shad juveniles during their migration period in 2006. More than 940 hours reached critical values including 460 hours that would result in the death of individuals. Although the fish taxa appear to be more sensitive towards hypoxia, the crustacean taxa show also a strong sensitivity in the early ontogenic stage and on eggs-bearing females. Because shrimp is a major component of the estuarine food web, this taxon appears as a promising indicator of ecosystem dysfunction.
(pp. 1, 05/05/2014)
UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
A hidden renewal model for monitoring aquatic systems biosensors
This article proposes a method to model signals of oysters' openings over time using a four-state renewal process. Two of them are of particular interest and correspond to instants when the animals are open or closed. An estimator of the cumulative jump rate of the renewal process is provided. It relies on observations of the jumps between the four states. Here these measures are not available but the observed signal is assumed to take ranges of real values according to this underlying process. A procedure to estimate a probability density function that summarizes the information of the signal is explained. This leads to estimation of the hidden renewal process and of its cumulative jump rate for each oyster. We propose to classify these estimated functions for a group of oysters in order to discriminate these animals according to their health status. Such a diagnosis is essential when using these animals as biosensors for water quality assessment.
(Environmetrics. vol. 25, n° 1180-4009, pp. 189-199, 01/05/2014)
IMB, UB, Bordeaux INP, CNRS, CQFD, IMB, UB, Bordeaux INP, CNRS, Inria, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LMBA, UBS, UBO EPE, CNRS
First Discovery of Channel-Levee Complexes In A Modern Deep-Water Carbonate Slope Environment
New high-quality high-resolution seismic data along the western slope of the Great Bahama Bank reveals a present-day channel-levee complex developed in a pure carbonate setting. This complex grew over two buried complexes separated by erosion surfaces, suggesting both the continuity of downslope gravity-driven processes along this carbonate slope, and channel migration through avulsion, processes similar to what happens along siliciclastic slopes. Complex morphology and geometry are similar to analogs described in siliciclastic systems, but the size of the presented carbonate complex is smaller by a factor of ten. Integrating high-resolution seismic and core studies shows that this complex was built by the stacking of gravityflow deposits, including turbidites. It presently is inactive and buried by deposits from hemipelagic fallout or low-energy density processes channeled by the gully network; Recent sediments are reworked by along-slope bottom currents dominated by internal tides. The discovery of these channel-levee complexes has implications both on the conceptual models describing the behavior of carbonate slope systems and on hydrocarbon exploration by enhancing the reservoir-bearing potential of carbonate slopes.
(Journal of Sedimentary Research. vol. 84, n° 1527-1404, pp. 1139-1146, 01/05/2014)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Sources and historical record of tin and butyl-tin species in a Mediterranean bay (Toulon Bay, France)
(Environmental Science and Pollution Research. vol. 21, n° 0944-1344, pp. 6640-6651, 01/05/2014)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ISA, UCBL, INC-CNRS, CNRS, PROTEE, UTLN, LASEM, CERCRID, UL2, UJM, UJM EPE, CNRS
Holocene glacial discharge fluctuations and recent instability in East Antarctica
Antarctica holds the largest ice sheet in the world, the East Antarctic Ice Sheet (EAIS), and plays a significant role in both local and global climate through the interactions between ice sheets, ocean, sea ice, and atmosphere. Our understanding of East Antarctica Holocene climate variability relies mainly on ice cores that however do not document glacial discharge history. Here, we present the first high resolution δ 18 O diatom record derived from two marine sediment cores retrieved on the East Antarctic continental shelf to reconstruct glacial discharge off Adélie Land and George V Land (AL-GVL) over the last 11,000 years from decadal to centennial resolution. Our results suggest multi-centennial glacier advances and retreats until 2000 cal yr BP, followed by a period of relative instability marked by two major glacial retreats centered at ∼1700 cal yr BP and ∼1980 CE. We suggest that the multi-centennial oscillations during the Early/Mid-Holocene reflect glacier fluctuations in response to long-term local seasonal insolation and short-term solar variability. We also propose that δ 18 O diatom variability over the last 2000 years was the result of a recent change in the AL-GVL region to increasing atmospheric influence, linked to ENSO intensification and teleconnections strengthening between low and high latitudes.
(Earth and Planetary Science Letters. vol. 394, n° 0012-821X, pp. 38-47, 01/05/2014)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LOCEAN, IPSL, ENS-PSL, PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, IP Paris, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS
New Wideband Miniature Branchline Coupler on IPD Technology for Beamforming Applications
In this paper, we present a new wideband miniature branchline coupler as a key circuit to be integrated in 60-GHz packaged beamforming networks for phased-array antennas. First, the integrated passive device (IPD) technology from STMicroelectronics is investigated in the mm-wave range through the simulation, fabrication, and measurements of a microstrip line and a simple hybrid coupler. Then, a novel coupler topology with emphasis on miniaturization and broadband operation is theorized. Analytical equations are derived and a 60-GHz coupler is optimized on IPD technology. Measurement results are discussed and compared with state-of-the art publications. The whole 57-66-GHz bandwidth is efficiently covered with the three following performance: -10-dB impedance matching, ±1-dB amplitude imbalance, and ±5° phase imbalance. As an application example, the novel coupler is integrated into a 4 × 4 Butler matrix suitable for an array-antenna demonstrating stateof-the art performance in terms of insertion loss and phase error. The measurement of different samples shows low variation of the IPD process because of very good reproducibility making it a suitable candidate for circuits operating in the 60-GHz band.
(IEEE Transactions on Components, Packaging and Manufacturing Technology. vol. 4, n° 2156-3950, pp. 911-921, 01/05/2014)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEAT-CNRS-UMR7248, UNS, CNRS, UniCA, ST-TOURS
Quantification of MTE in surface sediments of Morbihan Coast (South Brittany, France): A preliminary approach for determination of sources and dynamics
(27/04/2014)
GEOARCHI, UBS, UBO EPE, IBSHS, UBO EPE, LGO, UBS, IFREMER, UBO EPE, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LDO, INSU - CNRS, UBO EPE, CNRS
Caractérisation de la contamination des systèmes aquatiques par les psychotropes : développement d'une méthode de référence incluant une démarche multifactorielle de hiérarchisation
Les résidus de médicaments font partie des polluants dits « émergents » pour lesquels il n’existe actuellement pas de réglementation quant à leur présence dans l’environnement. Afin d’anticiper un risque éventuel pour l’Homme et les milieux aquatiques il est, entre autres, nécessaire de réaliser un état des lieux de la contamination des systèmes aquatiques par ce type de micropolluants. Dans ce contexte, disposer de données de mesures de qualité (traçables et comparables) constitue un prérequis indispensable pour décider au mieux des politiques à conduire dans ce domaine. L’étude des psychotropes présente un enjeu important d’autant plus qu’il s’agit de molécules abondamment consommées.Les travaux conduits lors de cette thèse avaient deux objectifs principaux. Le premier était de caractériser l’occurrence environnementale de composés psychotropes. Le second objectif était de proposer des outils métrologiques permettant d’assurer l’exactitude, la traçabilité, la comparabilité mais également la représentativité des résultats de mesure.Dans un premier temps, une méthode multi-résidus par SPE-LC-MS² a été développée pour une sélection de composés psychotropes et d’autres médicaments de consommation courante. Les limites de quantification de la méthode étaient de l’ordre du ng.L-1. Cela a permis de caractériser leur occurrence dans différents cours d’eau et rejets de station d’épuration en France. En parallèle, une approche par échantillonnage intégratif a été développée et déployée dans différents sites. Cette stratégie complémentaire a permis d’établir les niveaux d’occurrence des 68 psychotropes et traceurs sélectionnés et de conduire une démarche de hiérarchisation dans le but d’établir une liste restreinte de composés d’intérêt. Enfin, une méthode de référence associant la dilution isotopique à la spectrométrie de masse (DI-MS) a été développée pour l’analyse de 24 psychotropes dans les eaux de surface. Elle se caractérise par des incertitudes élargies (k=2) inférieures à 10%. La mise en oeuvre de cette méthode dans des études environnementales a permis de mettre en évidence l’importance de la contribution de l’incertitude liée à l’échantillonnage par rapport à l’incertitude totale de mesure.
(18/04/2014)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
ECHIBIOTEB : Outils innovants d’échantillonnage, d’analyses chimiques et biologiques pour le suivi des traitements avancés des eaux usées et des boues
(pp. 1, 02/04/2014)
UR MALY, IRSTEA, INERIS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Statistically assessing the correlation between salinity and morphology in cysts produced by the dinoflagellate Protoceratium reticulatum from surface sediments of the North Atlantic Ocean, Mediterranean–Marmara–Black Sea region, and Baltic–Kattegat–Skagerrak estuarine system
Recent studies have correlated dinoflagellate resting cyst morphology to salinity and density variations in the water column, suggesting that morphology can be used for paleoceanographic reconstructions. However, the univariate statistics used by these studies are appropriate only where morphology is related to a single variable. Density is a function of salinity and temperature, so more advanced statistical methods are needed to understand which parameters affect morphology. In this study based on surface (coretop) sediments, a set of environmental variables (sea-surface salinity, temperature, nitrate, and phosphate) was simultaneously correlated to morphological variations seen in resting cysts produced by the dinoflagellate Protoceratium reticulatum (= Operculodinium centrocarpum sensu Wall and Dale). Approximately 3200 measurements were obtained from the North Atlantic Ocean and used to generate a working model based on the Akaike information criterion. Hierarchical partitioning was then applied to establish the independent and joint effects for each predictor variable. Results from these analyses showed that while salinity constitutes the dominant variable affecting process length in the cysts of P. reticulatum in the North Atlantic, it is not the sole explanatory variable and that multicollinearity exists. Temperature and nutrients also showed a significant relationship to the morphology, requiring multiple regression to construct a representative model. The applicability of the North Atlantic working model was finally evaluated by comparing the results to data from the Mediterranean, Marmara, and Black seas, and Baltic-Kattegat-Skagerrak estuarine system. This comparison showed regional differences in morphological-environmental correlation. While salinity constitutes the most important explanatory factor in both the North Atlantic and Baltic-Skagerrak system, this is not so for the Mediterranean-Black Sea region where temperature is the dominant variable. It is concluded that a predictive salinity model based on P. reticulatum cyst morphology has at best a regional application.
(Palaeogeography, Palaeoclimatology, Palaeoecology. vol. 399, n° 0031-0182, pp. 202-213, 01/04/2014)
UGent, GEOTOP, EPM, UdeM, UQAT, UQAR, UQAM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS