The Crotone series: A synthesis and new data
The Crotone series is undoubtedly the best-studied Early Pleistocene succession in the world. Its matchless location and sedimentary conditions contribute to optimal achievements in biostratigraphy, magnetostratigraphy, cyclostratigraphy, and finally chronology. Robust stratigraphic correlations are established between the Semaforo and Vrica areas thanks to field surveys, a cored borehole, and ash mineralogy and geochemistry. The Crotone series covers the time-interval from 2.47 to 1.21 Ma and displays 30 complete glacial–interglacial cycles, from MIS 97 to MIS 37. Insolation cycles are recorded from i-236 to i-116 by combining lithology (sapropels) and palynology (amorphous organic matter and abundance in pollen grains of riparian trees, two indices of anoxic condition development and runoff intensity, respectively). The understanding of Early Pleistocene glacial–interglacial pollen records is clarified as the response of vegetation to the strong interaction between precession and obliquity has been analysed along several successive climatic cycles. Modern pollen records from the Rhône mouth shed light on the conditions of deposition of the sapropels, contributing to specify their intensity and duration.
(Quaternary International. vol. 219, n° 1040-6182, pp. 121-133, 10/06/2010)
PEPS, UCBL, INSU - CNRS, CNRS, LDO, INSU - CNRS, UBO EPE, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, UCLouvain, CEREGE, IRD, INRA, AMU, CdF (institution), INSU - CNRS, CNRS, IAMC-CNR
Climate-driven changes in coastal marine systems of western Europe
Coastal marine systems, the interface between the ocean and terrestrial realms, are among the most important systems on the planet both ecologically and economically because of their crucial role in earth system functioning. Although direct impacts of human activities on physical, chemical and biological components of these systems have been widely documented, the potential influence of climate variability is less well known. Here, we used data from Service d'Observation en Milieu Littoral (SOMLIT), a marine monitoring programme that has since 1997 collected samples at 12 sites located along the French coasts from 42° to 51°N. Applying standardised principal component analysis (PCA), we documented the year-to-year fluctuations in these coastal systems and evaluated the potential influence of climate variability using data on atmospheric circulation (wind intensity and direction), precipitation and temperature. Our study revealed a pronounced sensitivity of these systems to climate variability. As the impact of climate change may become more prominent in the next decades, this study suggests that climate might strongly influence the marine coastal environment and act in synergism with other anthropogenic pressures to alter the state and functioning of biological and ecological systems and the services they provide.
(Marine Ecology Progress Series. vol. 408, n° 0171-8630, pp. 129-148, 03/06/2010)
LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEMAR, IRD, IFREMER, UBO EPE, CNRS, AD2M, SBR, UPMC, CNRS, UPMC, CNRS
The Orinoco turbidite system: Tectonic controls on sea-floor morphology and sedimentation
Because of its location in an active margin context, the sand-rich Orinoco turbidite system is controlled morphologically and tectonically by the compressional structures of the Barbados prism, and as a consequence, the sedimentation system does not exhibit a classic fan geometry. The sea-floor geometry between the slope of the front of the Barbados prism and the slope of the Guyana margin induces the convergence of the turbidite channels toward the abyssal plain at the front of the Barbados accretionary prism. Also, whereas in most passive margins the turbidite systems are commonly organized upstream to downstream as canyon, then channel levee, then lobes, here, because of the control by active tectonics, the sedimentary system is organized as channel levee, then canyons, then channelized lobes. In shallow water, landward of the prism, the system has multiple sources with several distributaries, and progressively downward, the channel courses are more complex with frequent convergences or divergences that are emphasized by the effects of the undulating sea-floor morphologies. Erosional processes are almost absent in the upper part of the turbidite system shallower than 1500 m (4921 ft). Erosion along channels develops mostly between 2000 and 4000 m (6562 and 13,123 ft) of water depth, above the compressional structures of the Barbados prism. Incisions show irregular meandering and sinuous courses in the low-relief segments and less sinuous courses where channels incise the structures. Larger incisions (canyons) are 3 km (1.9 mi) wide and 300 m (984 ft) deep. The occurrence of different phases of successive incisions is responsible for the development of morphologically correlative terraces in both flanks of the canyons. This might be the consequence of two mechanisms: the tectonic activity of the deformation front characterized by progressive uplift and thrusting of recent sediments, and the superimposition of the cycles of the Orinoco turbidite system. Piston-core surveys have demonstrated that turbidite sediments moving through the channel and canyon system and deposited in the abyssal plain are mostly coarse sandy deposits covered by recent pelagic planktonic-rich sedimentation, which indicates that sand deposition slowed down during the postglacial sea level rise.
(AAPG Bulletin. vol. 94, n° 0149-1423, pp. 869-887, 01/06/2010)
IFPEN, BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LGCA, OSUG, UJF, Grenoble INP, INSU - CNRS, IRSTEA, USMB [Université de Savoie] [Université de Chambéry], CNRS, CNRS, GEOSCIENCES, PSL
Bathymétrie littorale par télédétection : méthodes, précision et finalités
Cet article fait le point sur les principales techniques d'inversion bathymétrique en zone littorale par télédétection. Ces techniques exploitent différents types de capteurs (lidar, photographie numérique, vidéo) sur des plateformes atellitaires, aéroportées ou fixes. Les mesures bathymétriques obtenues se distinguent par leur résolution spatiotemporelle, l'emprise spatiale des zones couvertes et leur précision. Ces techniques ont récemment été expérimentées sur des plages sableuses très dynamiques, évoluant rapidement sous l'action des vagues et des courants, ce qui permet d'évaluer leur pertinence vis-à-vis des échelles des différents processus d'intérêt en dynamique sédimentaire littorale. La précision des reconstructions bathymétriques est très variable allant de 0,1 à 0,95 m. Outre le choix de la plateforme d'observation qui détermine les échelles spatiales couvertes et la résolution planimétrique, ce sont les contraintes de mise en oeuvre (météo, coût financier) et la maturité des méthodes qui conditionnent la précision de la mesure réalisée et leur positionnement vis-à-vis de la temporalité des processus et des évolutions morphologiques observés
(pp. 457-468, 01/06/2010)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM, LDO, INSU - CNRS, UBO EPE, CNRS
Long term and recent climate changes recorded in North Atlantic oceanic archives around iceland
This contribution will compile paleoceanographic and paleoclimatic works which, over the last decades, provided major insights in our understanding of the Earth's climate natural variability and the underlying forcing mechanisms. A focus will be made on peri-icelandic marine records which document the climatic pace at different time-scales and are supported by multiproxy evidences. A special attention to the link in between the ocean and the cryosphere will be done.
(11/05/2010)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
The holocene climatic history of the Circum-icelandic oceanic realms
One of the achievements of the IPY was to foster an unprecedented amount of research initiatives aiming at studying recent (Holocene) changes in ocean circulation and climate in the subarctic and arctic domains. Paleo-investigations offer invaluable information on natural environmental changes at decadal to millennial scale, as well as on the processes driving them. We hereby present some recent results based on proxy records from circum Icelandic areas.
(11/05/2010)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Short-term metallothionein inductions in the edible cockle Cerastoderma edule after cadmium or mercury exposure: Discrepancy between mRNA and protein responses
Metallothioneins (MT) are essential metal binding proteins involved in metal homeostasis and detoxification in living organisms. Numerous studies have focused on MT response to metal exposure and showed an important variability according to species, metal, concentration and time of exposure. In this study, the expression of one isoform of MT gene (Cemt1) and associated MT protein synthesis were determined after 1, 3, 9, 24, 72 and 168h of cadmium (Cd) or mercury (Hg) exposures in gills of the cockle Cerastoderma edule. This experiment, carried out in laboratory conditions, revealed that in Cd-exposed cockles, induction of Cemt1 is time-dependent following a "pulse-scheme" with significant upregulation at 24h and 168h intersected by time point (72h) with significant downregulation. MT protein concentration increases with time in gills of exposed cockles in relation with the progressive accumulation of Cd in soluble fraction. On contrary, Hg exposure does not lead to any induction of Cemt1 mRNA expression or MT protein synthesis compared to control, despite a higher accumulation of this metal in gills of cockles compared to Cd. The localization of Hg (85-90%) is in insoluble fraction, whereas MT was located in the cytoplasm of cells. This gives us a first clue to understand the inability of Hg to activate MT synthesis. However, other biochemical processes probably occur in gills of C. edule since the remaining soluble fraction of Hg exceeds MT sequestration ability. Finally, since one of the first main targets of metal toxicity in cells was the mitochondria, some genes involved in mitochondria metabolism were also analyzed in order to assess potential differences in cellular damages between two metal exposures. Indeed, until T(168), no impact on mitochondrial genes was shown following Hg exposure, despite the complete lack of MT response. This result indicated the presence of other effective cellular ligands which sequester the cytosolic fraction of this metal and consequently inhibit metal reactivity. Such competition mechanisms with other cytosolic ligands more sensitive to Hg were particularly argued in the discussion.
(Aquatic Toxicology. vol. 97, n° 0166-445X, pp. 260-267, 01/05/2010)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Biomarker responses in polar cod (Boreogadus saida) exposed to the water soluble fraction of crude oil
In order to mimic the biological effects of an oil spill in Arctic waters, we examined several types of biomarkers (genes, enzymes, metabolites, and DNA damage) in polar cod Boreogadus saida experimentally exposed to the water soluble fractions of crude oil. During 4 weeks of exposure, induction of the studied biomarkers exceeded baseline levels. The mRNA expression of the cytochrome P4501A1 (cyp1a1) gene was the most promising biomarker, with glutathione S-transferase (gst) as a suitable complement. The delayed ethoxyresorufin O-deethylase (EROD) and GST activities and their persistence following 2 weeks of depuration may allow detection of previous exposures in field samples. The composition of PAH metabolites in the bile indicated the bioavailability of different PAH size-classes. Although mRNA expressions of antioxidant defense genes were induced at start of the exposure, with the strongest responses from catalase and cytosolic superoxide dismutase, they were poor for oil monitoring purposes due to their very short response times. Significant DNA damage demonstrated genotoxicity even at low PAH concentrations (<15 μg L−1) and was correlated with benzo(a)pyrene and pyrene metabolites in the bile.
(Aquatic Toxicology. vol. 97, n° 0166-445X, pp. 234-242, 01/05/2010)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Millennial-scale variability in Atlantic water advection to the Nordic Seas derived from Holocene coccolith concentration records
Abundance patterns of coccolith species in two Holocene marine cores retrieved off Norway and northern Iceland are indicative of millennial-scale modulations in the flow of the main (Norwegian Atlantic Current) and secondary (North Iceland Irminger Current) branches of the North Atlantic Drift to the Nordic Seas. Long-term trends in coccolith abundance changes reflect major Holocene steps in Atlantic Water transfer to the Nordic Seas at orbital scale with important constraints on the convective activity of the Nordic Seas that leads to the formation of the precursor water mass of North Atlantic Deep Water. Millennial-scale Holocene episodes of increased advection of Atlantic waters off Norway are associated with enhanced winter precipitation over Scandinavia, increased sea-salt fluxes over Greenland, and strengthened wind over Iceland, thereby suggesting a common atmospheric forcing: the location and intensity of the westerlies and the associated changes in mid-to high-latitude pressure gradients. Our biotic data indicate an opposite pattern of Atlantic water inflow at suborbital scale between the western (Denmark) and eastern (IcelandeScotland) straits of the northern Atlantic throughout the Holocene. This, as supported by present observational and simulated data, further highlights the role of atmospheric oscillations in the recent history of the North Atlantic-Nordic Seas water mass exchanges across the GreenlandeScotland Ridge. Such atmospheric processes are thought to explain the observed coupling between periods of excess export of arctic sea-ice to the Nordic Seas and intervals of maximum inflow of Atlantic water to the Norwegian Sea throughout the last 11 000 years.
(Quaternary Science Reviews. vol. 29, n° 0277-3791, pp. 1276 - 1287, 01/05/2010)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Temporal Dynamics of River Biofilm in Constant Flows
A 15-week experiment was performed in a riverside laboratory flume (with diverted river water) to check variations of river biofilm structure (biomass, algal and bacterial compositions) and function (community gross primary production GPP and respiration) under constant flow while water quality went through natural temporal variations. One major suspended matter pulse coinciding with one river flood was recorded after 10 weeks of experiment. Epilithic biofilm first exhibited a 10-week typical pattern of biomass accrual reaching 33 g ash-free dry matter (AFDM) m–2 and 487 mg chlorophyll-a m–2 and then, experienced a shift to dominance of loss processes (loss of 60% AFDM and 80% chlorophyll-a) coinciding with the main suspended matter pulse. Algal diversity remained low and constant during the experiment: Fragilaria capucina and Encyonema minutum always contribute over 80% of cell counts. DGGE banding patterns discriminated between two groups that corresponded to samples before and after biomass loss, indicating major changes in the bacterial community composition. GPP/R remained high during the experiment, suggesting that photoautotrophic metabolism prevailed and detachment was not autogenic (i.e., due to algal senescence or driven by heterotrophic processes within the biofilm). Observational results suggested that silt deposition into the biofilm matrix could have triggered biomass loss.
(International Review of Hydrobiology. vol. 95, n° 1434-2944, pp. 156-170, 01/05/2010)
LEFE, INEE-CNRS, CNRS, UT3, Comue de Toulouse, CNRS, Toulouse INP, Comue de Toulouse, UPV / EHU, IMFT, UT3, Comue de Toulouse, CNRS, Toulouse INP, Comue de Toulouse, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS