Climate mediated size variability of diatom Fragilariopsis kerguelensis in the Southern Ocean
(Quaternary Science Reviews. vol. 69, n° 0277-3791, pp. 49-58, 01/06/2013)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Étude des effets et du rôle des herbiers à Zostera noltii sur la biogéochimie des sédiments intertidaux
Cette étude a été menée afin de mieux comprendre l’influence de l’herbier à Zosteranoltii du Bassin d’Arcachon, herbier affecté par une sévère régression depuis les années2000, sur la dynamique biogéochimique des sédiments intertidaux de cette lagune. Dans cet environnement côtier dynamique, il s’agissait de caractériser cette influence sur demultiples échelles spatiales (i.e. de la racine à l'écosystème) et temporelles (i.e. tidale, diurne, saisonnière et interannuelle). Des mesures par voltammétrie in situ de la composition des eaux porales des sédiments intertidaux non végétalisés ont montré que (i) les distributions verticales des espèces réduites variaient avec les marées et que (ii) la dynamique de l’oxygène dissous en réponse aux cycles tidaux et diurnes était contrôlée par l’activité photosynthétique et les migrations verticales du microphytobenthos. L’étude de l’influence de l’herbier sur cette dynamique via des pertes d’oxygène au niveau des racines a été initiée en mesurant les variations des concentrations en oxygène à l’intérieur des lacunes aérifères de ces plantes. L’organisation des lacunes de Zostera noltii est présentée pour la première fois dans cette étude. La distribution verticale de nutriments dans les eaux porales de sédiments végétalisés et de sédiments nus a été caractérisée pendant la période de croissance de l’herbier. La présence de Zostera noltii a induit une zonation verticale marquée de cette distribution qui reflète l’évolution avec la profondeur de l’équilibre entre la production de nutriments résultant de l’exsudation de matière organique labile par les parties souterraines de la plante (source) et le pompage de ces nutriments par les racines (puits). L’existence d’un pompage de carbone inorganique dissous et de silice dissoute par les racines de l’herbier a été mise en évidence. Des mesures d’échanges benthiques d’oxygène dissous sur des sédiments nus et colonisés par Zostera noltii ont permis de caractériser la saisonnalité et l’hétérogénéité spatiale du métabolisme benthique (respiration et production primaire brute) en relation avec les distributions d’herbier et/ou de macrofaune benthique. Dans les sédiments végétalisés, la forte variabilité spatio-temporelle de ce métabolisme benthique était largement contrôlée par la biomasse de feuilles d’herbier. A l’échelle de la lagune, nos calculs ont montré que la regression de l’herbier à Zostera noltii entre 2005 et 2007 a induit une diminution significative des taux de respiration et de production de la zone intertidal de la lagune. L’évolution interannuelle de la biogéochimie de sédiments colonisés par Zostera noltii a été étudiée en 2006 et en 2010/2011 sur une zone située dans une partie du Bassin d’Arcachon particulièrement affectée par le déclin des herbiers (secteur de Cassy). Contrairement aux observations réalisées sur l’herbier bien portant en 2006, l’herbier en déclin augmenterait le relargage de nutriments dans les sédiments via la stimulation de la production d’ammonium ou de la dissolution du phosphore particulaire. La régression des herbiers fournirait un apport significatif de phosphore vers la colonne d’eau de la lagune, d’une magnitude comparable aux apports par les rivières ou à ceux liés au pompage tidal.
(21/05/2013)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Environmental concentrations of irgarol, diuron and S-metolachlor induce deleterious effects on gametes and embryos of the Pacific oyster, Crassostrea gigas
Irgarol and diuron are the most representative "organic booster biocides" that replace organotin compounds in antifouling paints, and metolachlor is one of the most extensively used chloroacetamide herbicides in agriculture. The toxicity of S-metolachlor, irgarol and diuron was evaluated in Pacific oyster (Crassostrea gigas) gametes or embryos exposed to concentrations of pesticides ranging from 0.1× to 1000×, with 1× corresponding to environmental concentrations of the three studied pesticides in Arcachon Bay (France). Exposures were performed on (1) spermatozoa alone (2) oocytes alone and (3) both spermatozoa and oocytes, and adverse effects on fertilization success and offspring development were recorded. The results showed that the fertilizing capacity of spermatozoa was significantly affected after gamete exposure to pesticide concentrations as low as 1× of irgarol and diuron and 10× of metolachlor. The offspring obtained from pesticide-exposed spermatozoa displayed a dose-dependent increase in developmental abnormalities. In contrast, treating oocytes with pesticide concentrations up to 10× did not alter fertilization rate and offspring quality. However, a significant decline in fertilization success and increase in abnormal D-larvae prevalence were observed at higher concentrations 10× (0.1 μg L(-1)) for S-metolachlor and 100× for irgarol (1.0 μg L(-1)) and diuron (4.0 μg L(-1)). Irgarol, diuron and S-metolachlor also induced a dose-dependent increase in abnormal D-larvae prevalence when freshly fertilized embryos were treated with pesticide concentrations as low as concentration of 1× (0.01 μg L(-1) for irgarol or S-metolachlor, and 0.04 μg L(-1) for diuron). The two bioassays on C. gigas spermatozoa and embryos displayed similar sensitivities to the studied pesticides while oocytes were less sensitive. Diuron, irgarol and S-metolachlor induced spermiotoxicity and embryotoxicity at environmentally relevant concentrations and therefore might be a threat to oyster recruitment in coastal areas facing chronic inputs of pesticides.
(Marine Environmental Research. vol. 89, n° 0141-1136, pp. 1-8, 09/05/2013)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Design and validation of an automated method to detect known adverse drug reactions in MEDLINE: a contribution from the EU-ADR project
(Journal of the American Medical Informatics Association. vol. 20, n° 1067-5027, pp. 446-452, 01/05/2013)
GReD, INSERM, UCA [2017-2020], CNRS, GReD, INSERM, UCA [2017-2020], CNRS, GEQA, INRA, INSERM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CHU Nantes, CHU Bordeaux, INSERM, LERTIM
High resolution Holocene record in the southeastern Bay of Biscay: Global versus regional climate signals
(Palaeogeography, Palaeoclimatology, Palaeoecology. vol. 377, n° 0031-0182, pp. 28-44, 01/05/2013)
BIAF, UA, LAM, AMU, INSU - CNRS, CNES, CNRS, MPIC, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, MPE
Sea-surface hydrographical conditions off South Faeroes and within the North-Eastern North Atlantic through MIS 2: the response of dinocysts
The last glacial period, showing the progressive development of large boreal ice sheets, was punctuated by large climatic excursions. These excursions were triggered mainly by atmosphere-ocean-ice coupled dynamics and are thus exemplary case studies of natural climate variability. To characterize the sea-surface palaeohydrographical changes accompanying these oscillations along the European margin, we have integrated new palynological data (dinocysts) acquired on core MD99-2281 (60°N, Faeroe Margin) during Marine Isotope Stage 2 in a latitudinal transect including published cores MD95-2002 (47°N, Celtic Margin) and MD95-2010 (66°N, Vöring Plateau). This transect is superimposed on the modern North Atlantic Drift pathway, but also at the outskirts of glacial European ice sheets, thus ideally located to track sea-ice extent and ice-sheet instabilities through time. The results show a coherent and sensitive response of sea-surface environments to the complex chain of abrupt events that punctuated the end of the last glacial period. The Last Glacial Maximum was marked by large seasonal contrasts of temperatures, whereas Heinrich events (HE) were characterized by a sharp cooling and sea-ice development. A tripartite structure is identified within HE1, with indices of melting at 19k cal a BP, followed by a temperate phase synchronous of a relative stability of ice sheets, and a terminal phase (17.5-15k cal a BP) characteristic of the 'conventional Laurentian' HE1.
(Journal of Quaternary Science. vol. 28, n° 0267-8179, pp. 217-228, 11/04/2013)
LDO, INSU - CNRS, UBO EPE, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, VU, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, CLIM, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, NIOZ
Inferring denudation variations from the sediment record; an example of the last glacial cycle record of the Golo Basin and watershed, East Corsica, western Mediterranean sea
Geophysical data and sampling of the Golo Basin (East Corsica margin) provide the opportunity to study mass balance in a single drainage system over the last 130 kyr, by comparing deposited sediments in the sink and the maximum eroded volume in the source using total denudation proxies. Evaluation of the solid sediments deposited offshore and careful integration of uncertainties from the age model and physical properties allow us to constrain three periods of sedimentation during the last climatic cycle. The peak of sedimentation initiated during Marine Isotopic Stage (MIS) 3 (ca. 45 ka) and lasted until late in MIS 2 (ca. 18 ka). This correlates with Mediterranean Sea palaeoclimatic records and the glaciation in high altitude Corsica. The yield of solid sediment into the Golo Basin drops in the observed present day Mediterranean basins (gauging stations), whereas the palaeo-denudation estimate derived from the sediments over the last glacial period is one to ten times higher than that predicted using cosmogenic or thermochronometer estimates of exhumation. The catchment-wide denudation rate calculated from deposited solid sediment ranges from 47 to 219 mm kyr−1, which is higher than the estimate from palaeosurface ablation in the proximal part of the source (9-140 mm kyr−1) and lower than the distal, narrow, incised channel of the Golo River (160-475 mm kyr−1). This mismatch raises questions about the investigation of denudation at millennial-time scale (kyr) and at higher integrating times (Myr) as a reliable tool for determining the effect of climate change on mountain building and on sedimentary basin models.
(Basin Research. vol. 25, n° 0950-091X, pp. 197-218, 04/04/2013)
GET, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, GM, IFREMER, LDO, INSU - CNRS, UBO EPE, CNRS, [Total Energies. Anciennement : Total, TotalFina, TotalFinaElf], EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Evaluation of the recent morphological evolution of the Gironde estuary through the use of some preliminary synthetic indicators
Drastic evolution of the physical coastal environment are expected in the future under the effect of climate change. They make necessary to better understand the past morphology evolution, especially considering areas that are the habitat for some specific ecosystems. Moreover, because the context of the water framework directive (WFD), EU members need to generate indicators to evaluate the status of estuarine water masses. To satisfy these two obectives, the recent evolution of the Gironde estuary has been studied by the analysis of bathymetry with GIS. The Gironde is the largest estuary of western Europe, and one of the most turbid. In this study, the analysis extents from 1962 to 1994. Results show that the zone of maximum volume of deposited sediment has migrated continuously towards the upstream portion of the estuary, which is coherent with the decrease of summer river flow and the upstream shift of the turbidity maximum toward the riverine sections. In addition, zones with relative stable and unstable morphology were identified, showing rythmic distribution similarly to those previously recognized through the evolution over 160 years (18251984). This seems to be independent from the fluvial regime, but rather related to the interaction between tidal co-oscillations and estuarine morphology, which is not elucidated yet. Finally, some hydro-morpho-sediemntary (HMS) indicators useful to the WFD have been described : distribution of depths, changes on cross section areas, changes of intertidal areas. They are discussed to discriminate the "natural" and "anthropogenic" contribution to morphological changes observed.
(Journal of Coastal Research. vol. 165, n° 0749-0208, pp. 1224-1229, 01/04/2013)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Longshore sediment flux hindcast and potential impact of future wave climate change along the Gironde/Landes Coast, SW France
The West-facing Gironde/Landes Coast, SW France, comprises about 230 km of high-energy, nonengineered, sandy beaches. It extends from the Gironde estuary to the North, and to the Adour estuary to the South. Overall, the coast erodes at a rate of about 1 to 2 m/yr, with localized areas with stronger erosion or with a stable or slow accretive trend. The gradients in longshore sediment transport and the sediment budgets are presumably the most important factor controlling decadal scale evolution of the shoreline along the Gironde/Landes Coast. It is established that the net longshore drift, which is only disturbed at the tidal inlet system of the Arcachon Lagoon and shoreward of the Capbreton Canyon, is oriented southward (Michel, 1997). However, its intensity and longshore variability, as well as how it will evolve in the framework of climate change, are still a matter of debate. This important issue is addressed in this contribution. First, longshore sediment fluxes are hindcasted over the period 1958-2002, using an ERA-40 wind forced wave modelling and the most commonly used empirical longshore drift formulae (Charles et al, 2012). Results are (1) discussed with respect to the existing estimations based on smaller periods and using different datasets; (2) compared the shoreline evolution measured during this period and (3) further analyzed to address the respective contributions of the different representative wave classes (e.g. swell, storm waves, wind waves) to the total longshore drift. Wave projections, based on wind fields from one climate model (ARPEGE-Climat) for several emission scenarios (A2, A1B and B1), are carried out to estimate possible wave climate change in 2061-2100 (compared to a so-called REF scenario covering the 1961-2000 period). It shows that, for instance for the A2 scenario and the summer season, the modal significant wave height is likely to decrease together with a 5° northward rotation of incoming wave incidence. Based on the wave model outputs, longshore sediment fluxes along the Aquitanian coast are computed for the four scenarios. The analysis of the relative sediment flux evolution (A2, A1B and B1 scenarios with respect to present day REF scenario) shows an overall decrease of the southerly longshore drift magnitude. A thorough analysis of the wave components evolution responsible for this decreasing trend is done, as well as an analysis of the longshore drift gradients along the Aquitanian coast. The potential impact of longshore drift evolution on the shoreline evolution at the 2061-20100 is discussed.
(Journal of Coastal Research. vol. 65 (Special Issue), n° 0749-0208, pp. pp. 1785-1790, 01/04/2013)
BRGM, CSIRO, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Refining benthic foraminiferal Mg/Ca-temperature calibrations using core-tops from the western tropical Atlantic: Implication for paleotemperature estimation
[1] Benthic foraminiferal Mg/Ca has been shown to have great potential as a proxy for reconstructing deep water temperatures. However, the exact relationship between Mg uptake in benthic foraminifera and temperature is still ambiguous, and further exploration and refinement is much needed to reduce uncertainties associated with the method. Here, we present new core-top Mg/Ca data from benthic foraminiferal species from the lower part of the thermocline in the western tropical Atlantic (northern Brazilian margin). This area is unusual in that the changes in carbonate chemistry along the transect are very small, making it an ideal region for isolating and studying the role of temperature in the incorporation of Mg into the benthic shells. Our results show that benthic foraminiferal Mg/Ca largely reflects temperature in this area. Our data are combined with previously published data to produce new and improved Mg/Ca calibration equations for a number of benthic foraminiferal species within the Atlantic Ocean. Our study provides the first C. wuellerstorfi Mg/Ca data for the 4-6 °C temperature range and indicates that C. wuellerstorfi Mg/Ca is strongly controlled by temperature. As a result, the newly established C. wuellerstorfi calibration over the entire 0-6 °C temperature range is significantly improved with respect to previously published C. wuellerstorfi calibrations limited to the coldest part between 0 and 4 °C. Other benthic species (Cibicidoides kullenbergi, Globocassidulina subglobosa, Uvigerina peregrina, and Oridorsalis umbonatus) have also been studied, although these results are less conclusive.
(Geochemistry, Geophysics, Geosystems. vol. 14, pp. 929-946, 01/04/2013)
UiB, BCCR, BIO / UiB, UiB, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GLACCIOS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LPG-ANGERS, LPG, UA, UN UFR ST, UN, INSU - CNRS, CNRS