Secondary settlement of cockles Cerastoderma edule as a function of current velocity and substratum: a flume study with benthic juveniles
Some newly-settled bivalve molluscs can experience a second dispersal stage in the water column and colonize areas distant from initial settlement zone ('secondary settlement'). To document mechanisms involved in such a process, experiments were conducted in a recirculating 13-m flume, using juvenile cockles Cerastoderma edule (shell length between 0.8 and 5.7 mm). After 4 h and under current surface velocities of 10, 20 and 24 cm s−1, all juveniles left the plexiglass substratum (site of initial introduction) and 42.4, 58.6 and 76.2% of juveniles, respectively, were retrieved from a downstream sand area (which only represented 7.7% of the total flume surface). Naked-eye observations showed that smaller individuals were borne within the water column, whereas larger individuals tended to roll or slip on the substratum. Byssus threads produced by the juveniles were often seen, sometimes covered in sand grains. These observations were confirmed by finding larger juveniles in the upstream part of the sand area. When sand was replaced by mud, a reduced proportion of cockles was retrieved in the experimental substratum (18.4, 20.0 and 16.4%, respectively). Observations showed that juveniles rarely succeeded in anchoring themselves in mud. When initially introduced on a favourable substratum (medium sand), more than 87% of juveniles were retrieved from that sand array at all flow velocities. This study shows that secondary settlement occurs for juvenile cockles up to 5.7 mm in shell length and depends not only on flow velocity but on substratum type.
(Hydrobiologia. vol. 503, n° 0018-8158, pp. 103 - 116, 01/08/2003)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LIENSs, INSU - CNRS, ULR, CNRS
A decarbonation and preservation method for the analysis of organic C and N contents and stable isotope ratios of low-carbonated suspended particulate material
The aim of this study was to determine a simple routine procedure to preserve, decarbonate and analyse low-carbonated filters of suspended particulate organic matter (POM) for particulate organic carbon and nitrogen content, δ13C and δ15N. Our goal was to analyse these four parameters from a single and entire filter of POM without altering the organic material. First, freezing (-20°C) versus oven-drying (60°C) were compared as the initial preservation step. Afterwards, non-acidified samples were compared to acid-treated samples using 0.12N HCl (diluted HCl rinsing at the end of the filtration) or 12N HCl (filters exposed to HCl fumes for four hours in a dessicator). Regarding the preservation methods, our results indicate that freezing increases the uncertainty of δ15N measurements and, in combination with concentrated HCl treatment, leads to a loss of particulate nitrogen and an alteration of the δ15N signature. Consequently, we recommend drying to preserve filter samples. Regarding acid treatments, we found that (i) diluted HCl would not be sufficient to fully remove the carbonate from our samples, (ii) in contrast, a four-hour exposure of the filters to the HCl fumes was enough to remove all the inorganic carbon, and (iii) the concentrated HCl treatment did not alter the nitrogen measurements (only when drying without freezing is used to preserve the filters). Consequently, we propose that low-carbonated POM filters are preserved by drying and carbonates are removed by exposing the filters to HCl fumes (four hours) for the analysis of particulate organic C and N content and isotope ratios.
(Analytica Chimica Acta. vol. 491, n° 0003-2670, pp. 125–133, 27/06/2003)
LEMAR, IRD, IFREMER, UBO EPE, CNRS, IRD, VUB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CNRS, UBO IFCS, UBO EPE, CHU - BREST, CHRU Brest, IUEM, IRD, INSU - CNRS, UBO EPE, CNRS, LAIEM, UN UFR ST, UN, CNRS
The Sao Tomé deep-sea turbidite system (Southern Brazil Basin): Cenozoic seismic stratigraphy and sedimentary processes
The Sao Tomé deep-sea turbidite system, elongated parallel to the rise of the south Brazilian continental margin, was first interpreted as a channel-levee system resulting from contour-current activity. Study of new seismic data permits the proposal of a stratigraphy for the system and a new interpretation of depositional processes. Three major depositional units have been recognized that are separated by major erosive discontinuities. The basal unit seems to be Paleocene to lower or middle Eocene, and the second one, subdivided into two subunits, is probably upper Oligocene to middle Miocene. Both units show superimposed north-to-south-channelized turbidite systems, with supply provided directly from a channel network that crosses the upper margin in the north. The third unit is upper Miocene(?) to Pliocene or Quaternary and is still under predominantly gravity processes: turbidite processes in the lower and upper subunits, and major mass-flow processes in the median subunit. The sediment sources are located either in the north or in the south, with sediment provided by major deep-sea channels. The base of the upper subunit is well marked by an erosive discontinuity (late Pliocene or Pliocene-Quaternary boundary). Impact of the contour currents is mainly recorded as widespread erosive surfaces (seismic discontinuities) correlated to global hydrological events and transparent or wavy deposits. Because this system contains a significant amount of upper Quaternary sands, it suggests the occurrence of petroleum reservoirs along the rise and the Sao Paulo Plateau in the lower continental slope.
(AAPG Bulletin. vol. 87, n° 0149-1423, pp. 873-894, 01/05/2003)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
The key role of metallothioneins in the bivalve Corbicula Fliuminea during the depuration phase after in situ exposure to Cd and Zn
(Aquatic Toxicology. vol. 63, n° 0166-445X, pp. 89-102, 10/04/2003)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LMBA, UBS, UBO EPE, CNRS
Estimation of potential and limits of bivalve closure response to detect contaminants: a new approach applied to cadmium
(Environmental Toxicology and Chemistry. vol. 22, n° 0730-7268, pp. 914-920, 01/04/2003)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LMBA, UBS, UBO EPE, CNRS
Digenean trematodes moderately alter Hydrobia ulvae population size structure
The mudsnail Hydrobia ulvae, primary host to a number of digeneans, was studied to check whether parasite effects on individual hosts could have repercussion on population size structure and dynamics. Three different mudsnail populations were monitored monthly in Arcachon Bay, south-west France. Arguin is a moderately sheltered oceanic sandflat and a bird reserve, La Canelette is a sheltered sandflat near a harbour and Lette Douce is a sheltered salt marsh. Parasite prevalence differed among the three stations, with no obvious seasonal pattern: 0–16% at Arguin, 0–6% at La Canelette and 1–5% at Lette Douce. Between four and five digenean species were identified, with Haploporidae dominating at Arguin and Notocotylidae dominating at Lette Douce. Prevalence increased with snail shell height. Large snails from Arguin were heavily parasitized, but suddenly disappeared between December 1998 and January 1999. The snail size distribution was consequently modified. To test whether digenean-induced mortality could be involved, a 50-d laboratory experiment was performed. Mudsnails hosting digeneans with rediae (as Haploporidae or Heterophyidae) displayed significantly higher mortality rates than mudsnails hosting sporocysts (as Microphallidae) or healthy mudsnails. The present study demonstrates that digenean parasites induce population structure changes and shorten lifespan of mudsnails, through increasing size-dependent mortality.
(Journal of the Marine Biological Association of the United Kingdom. vol. 83, n° 0025-3154, pp. 297-305, 20/03/2003)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Toward a Better Determination of Turbulent Air–Sea Fluxes from Several Experiments
An accurate determination of turbulent exchanges between the ocean and the atmosphere is a prerequisite to identify and assess the mechanisms of interaction that control part of the variability in the two media over a wide range of spatial and temporal scales. An extended dataset for estimating air-sea fluxes (representing nearly 5700 h of turbulence measurements) has been collected since 1992 during six dedicated experiments performed in the Atlantic Ocean and the Mediterranean Sea. This paper presents the methodology used through the successive experiments to progress in this field. The major developments concern (i) flux instrumentation, with the deployment of a microwave refractometer to get the latent heat flux in most meteorological conditions; (ii) the analysis of airflow distortion effects around the ship structure and sensors through both computational fluid dynamics and physical simulations in a water tank, then the derivation of correction for these effects; (iii) the application of both inertial dissipation and eddy-correlation methods from the various experiments, allowing the authors to assess and discuss flux-determination methods on ships, and particularly bulk parameterization; (iv) the validation and analysis of mesoscale surface flux fields from models and satellites by using ship data, showing some deficiencies in operational model fields from ECMWF, the need of high-quality fluxes to interpret ocean-atmosphere exchanges, and the potential advantage of satellite retrieval methods. Further analysis of these datasets is being performed in a unique database (the ALBATROS project, open to the international scientific community). It will include refinement of airflow distortion correction and reprocessing of earlier datasets, the investigation of fluxes under specific conditions (low wind), and the effect of sea state among others. It will also contribute to further validation and improvements of satellite retrievals in various climatic/meteorological conditions.
(Journal of Climate. vol. 16, n° 0894-8755, pp. 600 - 618, 01/02/2003)
CETP, UVSQ, INSU - CNRS, CNRS, DIRSE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CREATIS, UCBL, CPE, INSA Lyon, INSA, INSERM, CNRS, DGO, UB, JPL, CALTECH, CNRM, INSU - CNRS, CNRS, Comue de Toulouse
Neandertal extinction and the millennial scale climatic variability of OIS 3
Population models seeking climate as a triggering factor for the extinction of Neandertals and the colonisation of Europe by Anatomically Modern Humans are contradictory due to uncertainties in the dating methods, in the cultural attribution of archaeological layers and to the lack of terrestrial continuous and well-dated palaeoclimatic sequences. This is particularly the case for the Iberian Peninsula where Neandertal populations seemto have survived later than in other regions of Europe. A review of the available palaeoclimatic evidence for OIS3 of Iberia reveals that this mainly consists of low resolution, fragmentary, ill-dated and often ill-interpreted records. Correlation between palaeoenvironmental sequences from two IMAGES pollen-rich deep sea cores and archaeological data fromwestern Europe (the electronic archive of the radiocarbon dates is available at QSR website http:// www.elsevier.nl/locate/quascirev) indicates that Aurignacian moderns colonised France and the north of Iberia at the onset of the H4 event. During this cold episode a probable contraction of Neandertal populations is recorded in southern Iberia where no Aurignacian settlements are detected. Such a decline in population density is correlated with the particular desert-steppe-like environments, made up of Artemisia, Chenopodiaceae and Ephedra, characterising the H4 of this area. While reducing the size of Neandertal populations, this inhospitable environment may have favoured their persistence in this region. Mainly exploiting herds of herbivores adapted to Graminees-rich grasslands, the Aurignacian moderns were probably not interested in colonising these arid Mediterranean biotopes, and did that only after the H4 event.
(Quaternary Science Reviews. vol. 22, n° 0277-3791, pp. 769-788, 23/10/2026)
PACEA, UB, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Massive flank failures and tsunamis in the Canary Islands: past, present, future
(pp. 132, 23/10/2026)
GEOLAB, UBP, IR SHS UNILIM, UNILIM, UCA [2017-2020], CNRS, UCA, ULPGC, CSIC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, OASU, UB, INSU - CNRS, ULR, CNRS, INRAE, LGP, UP1, UPEC UP12, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
The "Fleuve Manche" : the sub-marine sedimentary features from the outer shelf to the deep-sea fans
(J. Quat. Res.. vol. 18, pp. 361-391, 23/10/2026)
LT, UPMC, INSU - CNRS, UCP, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS