ENSO and interdecadal climate variability over the last century documented by geochemical records of two coral cores from the South West Pacific
The south west Pacific is affected by climatic phenomena such as ENSO (El Niño Southern Oscillation) or the PDO (Pacific Decadal Oscillation). Near-monthly resolution calibrations of Sr/Ca, U/Ca and d18Oc were made on corals taken from New Caledonia and Wallis Island. These geochemical variations could be linked to SST (sea surface temperature) and SSS (sea surface salinity) variations over the last two decades, itselves dependent on ENSO occurrences. On the other hand, near-half-yearly resolution over the last century smoothes seasonal and interannual climate signals, but emphasizes low frequency climate variability.
(Advances in Geosciences. vol. 6, n° 1680-7340, pp. 27, 09/01/2006)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, PALEOTROPIQUE
cDNA cloning and gene expression of ribosomal S9 protein gene in the mollusk Corbicula fluminea: A new potential biomarker of metal contamination up-regulated by cadmium and repressed by zinc
Biological indicators can be used to assess polluted sites, but their success depends on their specificity. The aim of the present study was to identify a specific cadmium biomarker of the freshwater bivalve Corbicula fluminea. Differential display technique was used to identify new molecular indicators for cadmium exposure. Gene expression of C. fluminea transplanted into a cadmium- and zinc-contaminated river was compared to gene expression of bivalves from a reference site. One differentially expressed band was identified, and the entire cDNA sequence coding for the ribosomal protein S9 (rpS9) was cloned. The rpS9 gene expression was studied by real-time reverse transcription-polymerase chain reaction. After controlled cadmium (15 microg/L) and/or zinc (1 mg/L) laboratory contaminations of the bivalves, this gene was shown to be up-regulated by cadmium and down-regulated by zinc. A 48-d transplantation of animals into a polymetallic field contamination in the Lot river basin (Midi-Pyrénées region, France) showed that rpS9 gene regulation was correlated with the fluctuating cadmium and zinc water contents. To our knowledge, the existence of a gene that is up-regulated by cadmium and repressed by zinc is demonstrated here for the first time.
(Environmental Toxicology and Chemistry. vol. 25, n° 0730-7268, pp. 527, 01/01/2006)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Modélisation du courant sagittal induit par les vagues au-dessus des systèmes barre/baïne de la côte aquitaine (France)
Modelling of a rip current induced by waves over a ridge and runnel system on the Aquitanian Coast, France. The spectral wave driver SWAN is coupled with the time- and depth-averaged (2DH) coastal area model MORPHODYN. This coupled model is used to simulate the rip current induced by breaking waves over ridge and runnel systems on the French Aquitanian Coast. Simulations lead to a description of the rip current characteristics and the physical mechanisms leading to its formation. The rip current is controlled by the local bathymetry, the tide level and offshore wave conditions. The presence of this rip current is favoured by shore-normal incidence and long-period swells. During low-energy conditions, the maximum rip current velocity occurs at midtide. For higher energy conditions, the maximum rip velocity sweeps to high tide. The residual forcing notion enables to explain and to highlight this tidal modulation and the rip current formation mechanisms
(Comptes Rendus. Géoscience. vol. 338, n° 1631-0713, pp. 711-717, 01/01/2006)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Modélisation du festonnage des barres sableuses d'avant-côte : application à la côte aquitaine, France
Modeling of crescentic pattern development of nearshore bars: Aquitanian Coast, France. Nearshore crescentic bars play key role in nearshore morphodynamics. These bars are observed all along the Aquitanian Coast, with a mean wavelength of about 700 m. A non-linear stability analysis is undertaken to simulate the development of crescentic patterns. Results show that self-organization mechanism can lead alone to the development of these alongshore rhythmic features. Simulated wavelengths are in agreement with observations on the Aquitanian Coast.
(Comptes Rendus. Géoscience. vol. 338, n° 1631-0713, pp. 795-801, 01/01/2006)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IMB, UB, Bordeaux INP, CNRS
A surface complexation model for cadmium and lead adsorption onto diatom surface
This work is devoted to the physico-chemical study of cadmium and lead interaction with diatom–water interfaces for two marine planktonic (Thalassiosira weissflogii = TW, Skeletonema costatum = SC) and two freshwater periphytic species (Achnanthidium minutissimum = AMIN, Navicula minima = NMIN) by combining adsorption measurements with surface complexation modeling. Reversible adsorption experiments were performed at 20 °C after 3 h of exposure as a function of pH, metal concentration in solution, and ionic strength. While the shape of pH-dependent adsorption edge is similar among all four diatom species, the constant-pH adsorption isotherm and maximal binding capacities differ. These observations allowed us to construct a surface complexation model for cadmium and lead binding by diatom surfaces that postulates the constant capacitance of the electric double layer and considers Cd and Pb complexation with mainly carboxylic and, partially, silanol groups. Parameters of this model are in agreement with previous acid–base titration results and allow quantitative reproduction of all adsorption experiments.
(Journal of Geochemical Exploration. vol. 88, n° 0375-6742, pp. 110-113, 01/01/2006)
LMTG, UT3, Comue de Toulouse, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Spatial distribution of zooplankton size spectra on the French continental shelf of the Bay of Biscay during spring 2000 and 2001
During two cruises in springtime (18 March to 13 April 2000 and 27 March to 4 June 2001), the whole French continental shelf of the Bay of Biscay was sampled to obtain an overview on the zooplankton community size structure. A laboratory optical plankton counter (OPC-1L) was used to process plankton net tow samples and estimate abundance, biovolume, and general characteristics of size spectra. In a second step, biomass estimates were extrapolated from size by using a conversion factor. Both biomass and abundance estimates show spatial patterns with a clear coastal-open sea gradient for both years. The coastal area was characterized by the highest biomasses and abundances per volume. A first analysis of the zooplankton community size spectra was made by using the slope of the normalized biomass size spectrum. Different spatial patterns of zooplankton size spectra were highlighted for spring 2000 and 2001. The highest slopes were found for the coastal zone, showing a large ratio of small organisms, although this was less marked in the springtime 2000. Stations characterized by high proportions of large organisms were located in majority in the north of the bay and at the shelf break. A second analysis using the size probability distributions of organisms revealed a nearly permanent nonlinearity of probability distributions. This implied the community structure was not in an equilibrium state during spring and this nonlinearity could be locally related to dominant species dynamics.
(Journal of Geophysical Research. Oceans. vol. 111, n° 2169-9275, 22/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LOPB, INSU - CNRS, CNRS
SYNCARID CRUSTACEANS FROM THE MONTCEAU LAGERSTÄTTE (UPPER CARBONIFEROUS; FRANCE)
Key aspects of the morphology, autecology, systematics and taphonomy of the crustacean syncarids from the Montceau Lagerstätte (Upper Carboniferous, Stephanian B; France) are presented. Palaeocaris secretanae is the most abundant faunal element of the Montceau biota and shows striking morphological similarities with Palaeocaris typus from the Mazon Creek Lagersta¨tte (Westphalian D; Illinois, USA). Palaeocaris secretanae was a shrimp-like animal with a short head (no head shield), large mandibles, 14 trunk segments (the first one being reduced) and a fan-like caudal termination. Both the body and the appendage design indicate abilities for crawling on the substratum (slender endopods) and for escape reaction (uropodal fan, pleonal flexibility), although swimming activities may have been reduced (trunk appendages with small flap-like exopods). Details of the appendages involved in feeding, e.g. mandibles and maxillipeds, indicate poor ability for predation but point to an omnivorous detritus feeding mode. Poorly developed respiratory organs (small cylindrical epipods) suggest a relatively low level of locomotory activity. The field of vision may have been large and panoramic (stalked eyes). Rows of pores on 12 trunk segments are interpreted as possible sensory organs used for current detection. Females were brooding eggs (clusters of eggs preserved along anteroventral trunk). Microprobe analysis indicates that siderite is the major component of the nodules. Four events played a key-role in the three-dimensional preservation of syncarids: (1) rapid burial, (2) minimal decomposition, (3) phosphatic mineralization shortly after the animal's death and (4) nodule formation around the carcass. Palaeocaris secretanae is morphologically close to Recent syncarids such Anaspides tasmaniae (freshwater streams, Australia) in its general body plan and detailed anatomy, e.g. mouth parts, indicating morphological stasis in syncarids over more than 200 million years.
(Paleontology. vol. 49, pp. 647-672, 22/02/2026)
PEPS, UCBL, INSU - CNRS, CNRS, LDO, INSU - CNRS, UBO EPE, CNRS
Monitoring the maximum turbidity zone and detecting fine-scale turbidity features in the Gironde estuary using high spatial resolution satellite sensor (SPOT HRV, Landsat ETM+) data
This study concerns the quantification of suspended particulate matter in the highly turbid estuarine waters of the Gironde, France, from high spatial resolution remotely sensed data, SPOT (Satellite Pour l'Observation de la Terre) High Resolution Visible (HRV), Landsat Enhanced Thematic Mapper Plus (ETM+). The methodology is based on calibration relationships established between the remote sensing reflectance (R-rs) signal and suspended particulate matter concentration (SPM), from in situ optical measurements. These relationships are valid in the long term as R-rs ratios between near-infrared (NIR) and visible wavebands are relatively independent of the particle grain-size and mineralogy. Consequently, they can be applied to satellite images, even if no simultaneous in situ measurements are carried out concurrently with the satellite overpass. Selected satellite sensor data are corrected for atmospheric effects using radiative transfer code, then converted into surface water SPM concentrations according to the established calibration relationships. Resulting SPM maps are presented for different river flow and tidal conditions. These maps are used to locate the maximum turbidity zone and observe its tidal and seasonal movements. The high spatial resolution of SPOT HRV and Landsat ETM+ satellite sensor data also shows detailed turbidity features in the estuary, resulting from re-suspension phenomena over banks and turbulent currents.
(INTERNATIONAL JOURNAL OF REMOTE SENSING. vol. 27, pp. 2303-2321, 22/02/2026)
LOV, OOVM, UPMC, INSU - CNRS, CNRS, UPMC, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
3D-fluorescence spectroscopic analysis of HPLC fractionated estuarine fulvic and humic acids
Six estuarine fulvic (FA) and humic acids (HA) were fractionated with reversed-phase high performance liquid chromatography in a water/acetonitrile gradient, with fluorescence detection. Differences between FA and HA chromatograms pointed to a higher incidence of hydrophobic components in the latter. Excitation-emission matrix fluorescence diagrams of most fractions were similar to those of the bulk samples indicating that, in spite of their distinct polarities, the complexity and main spectral characteristics of the materials persisted. A primary group of fluorophores, which are present in most of the fractions, seems to be at the origin of the fluorescence properties of both kinds of HS. A bathochromic shift of the bulk solutions spectra in relation to the fraction emissions was attributed to a greater proximity of these fluorophores, possibly due to the formation of aggregates. Generally, the results reinforced concepts that humic macromolecules consist of assemblages of structurally similar building blocks. \textcopyright 2006 Sociedade Brasileira de Qu\'imica.
(Journal of the Brazilian Chemical Society. vol. 17, n° 0103-5053, pp. 113--124, 22/02/2026)
UCS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Metallothionein gene expression and protein levels in triploid and diploid oysters Crassostrea gigas after exposure to cadmium and zinc.
Quantitative real-time polymerase chain reaction (PCR) was used to compare for the first time the differential expression of metallothionein (MT) isoform genes, together with biosynthesis of the total MT proteins, in the gills of triploid and diploid juvenile Pacific oyster Crassostrea gigas in response to cadmium (Cd) and zinc (Zn) exposure. Oysters were exposed to Cd (0.133 mM), Zn (15.3 mM), and Cd1Zn for 14 d. Results showed similar response capacities to metal exposures in the two populations. No significant difference was revealed in terms of MT gene expression, MT protein synthesis, and Cd accumulation. However, triploid oysters bioaccumulated Zn 30% less efficiently than diploid oysters. Among the three MT isoform genes, CgMT2 appeared to be more expressed than CgMT1, whereas CgMT3 appeared to be anecdotal (106 times lower than CgMT2). CgMT2 and CgMT1 gene expression levels were increased sevenfold in the presence of Cd, whereas Zn appeared to have no effect. A twofold increase in MT protein levels occurred in response to Cd exposure. Discrepancies between mRNA and protein levels suggest that in C. gigas MT are regulated at the transcriptional level, as well as at the translational level.
(Environmental Toxicology and Chemistry. vol. 25, n° 0730-7268, pp. 412-418, 22/02/2026)
LEESA, UB, IFP, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEMAR, IRD, IFREMER, UBO EPE, CNRS