Reconstruction of the late-Holocene changes in the Sub-Arctic Front position at the Reykjanes Ridge, north Atlantic
Changes in the dynamics of the North Atlantic subpolar gyre are involved in the modulation of the northward salinity and heat transport in the northern North Atlantic via the North Atlantic Current (NAC). Variations in the strength of the East Greenland Current (EGC) can influence the gyre dynamics by impacting deep convection in the Labrador Sea. Oxygen isotope data of three planktonic foraminiferal species (surface water Neogloboquadrina pachyderma dextral coiling and Globigerina bulloides; thermocline recorder Globorotalia inflata) from a site located close to the present Sub-Arctic Front at the Reykjanes Ridge suggest significant strengthening or shifting of the Sub-Arctic Front throughout the late Holocene. The oxygen isotope based inferences are supported by Mg/Ca-derived temperature reconstructions from Neogloboquadrina pachyderma dextral coiling, alkenone-derived sea surface temperature and other paleoclimatic proxy data. The late-Holocene strengthening/shift of the Sub-Arctic Front appears caused by an increasingly more defined and fresher EGC. The proposed subpolar gyre changes may modulate the northward heat transport, and explain the geographically different long-term climatic trends in the North Atlantic during the late Holocene, i.e. a cooling of the EGC-influenced regions and a warming of the NAC-influenced areas from c. 4 to 5 ka. This mechanism cannot, however, explain the simultaneous occurrence of millennial-scale events at c. 5.6, 3.9, 2.7, 1.3 ka and the ‘Little Ice Age’ in both areas. Noteworthy is the steadily increasing amplitude of these cold events at the Reykjanes Ridge, likely induced by drift ice and/or EGC-influence culminating in the ‘Little Ice Age’. A widespread pronounced warming at 2.0 ka seems to represent the ‘Roman Warm Period’ and reflects the warmest period of the late Holocene.
(The Holocene. vol. 22, n° 0959-6836, pp. 877-886, 19/03/2012)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
New data on the Silurian-Devonian palaeontology and biostratigraphy of Bolivia
In order to precisely establish the bio- and chronostratigraphic position of several levels of the Silurian-Devonian succession of Bolivia, with respect to the International Time Scale, additional Silurian and Devonian localities belonging to the Eastern Cordillera and the Interandean Zone areas have been recently revised and sampled, both for macrofossils and palynomorphs. Specifically, the localities are Nunumayani, and Muruhuta from the late Silurian-early Devonian time interval. Correlations with other fossiliferous localities are discussed, namely Huacallani and Rumicorral. A new outcrop yielding Middle Devonian tabulate corals at Pisacavina is described; its faunal content is described, and compared with the historical coral collection. As a result, it appears clearly that the Silurian-Devonian Bolivian fauna needs a thorough revision, as well as the selection of stratigraphically significant macrofossils. Besides macrofossils, the analysis of palynomorph assemblages is significant in establishment of both intra-Bolivian and international correlations before any reliable biogeographic reconstruction is done. This paper records the first discovery of a plant of the genus Protolepidodendron from the Devonian of Bolivia. An ostracod assemblage from Pisacavina is described, illustrated, and discussed for the first time; it suggests an Early Devonian or an Eifelian age. Newly described taxa include the coral Parastriatopora boliviana sp. nov., and the chonetoidean brachiopods Sanjuanetes glemareci sp. nov., and Kentronetes giae sp. nov.
(Bulletin of Geosciences. vol. 87, n° 1214-1119, pp. 269-314, 08/03/2012)
LDO, INSU - CNRS, UBO EPE, CNRS, IRSNB / RBINS, AMNH, GR, UR, INSU - CNRS, CNRS, CR2P, MNHN, UPMC, CNRS
Submarine slide initiation and evolution offshore Pointe Odden, Gabon — Analysis from annual bathymetric data (2004–2009)
Time serial bathymetric data acquired between 2004 and 2009 are used to evaluate the morphological evolution of the coastal area offshore Pointe Odden, located on the Mandji Island (Gabon). Data analysis highlights the alternation between fast sedimentation periods at shallow water depth related to intense longshore drift and catastrophic erosional events. Because of sediment overloading and slope oversteepening, small-scale instabilities are generated (successive slide scars, channel formation and growth by retrogressive erosion). However, when critical stability conditions are reached, large failures occur (2005 submarine slide). Geotechnical measurements and sedimentological analyses on the study area suggest that flow liquefaction would be the triggering mechanism of the 2005 event. Moreover, our analysis shows that the associated slide scar is rapidly filled by compensation and that failure morphology could disappear from the seafloor in about 15–20 years.
(Marine Geology. vol. 299-302, n° 0025-3227, pp. 43-50, 01/03/2012)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Contribution of changes in opal productivity and nutrient distribution in the coastal upwelling systems to late Pliocene/early Pleistocene climate cooling
The global late Pliocene/early Pleistocene cooling (~3.0-2.0 million years ago, Ma) concurred with extremely high diatom and biogenic opal production in most of the major coastal upwelling regions. This phenomenon was particularly pronounced in the Benguela Upwelling System (BUS), off Namibia, where it is known as the Matuyama Diatom Maximum (MDM). Our study focuses on a new diatom silicon isotope (δ30Si) record covering the MDM in the BUS. Unexpectedly, the variations in δ30Si signal follow biogenic opal content, whereby the highest δ30Si values correspond to the highest biogenic opal content. We interpret the higher δ30Si values during the MDM as a result of a stronger degree of silicate utilization in the surface waters caused by high productivity of mat-forming diatom species. This was most likely promoted by weak upwelling intensity dominating the BUS during the Plio/Pleistocene cooling combined with a large silicate supply derived from a strong Southern Ocean nutrient leakage responding to the expansion of Antarctic ice cover and the resulting stratification of the polar ocean 3.0-2.7 Ma ago. A similar scenario is hypothesized for other major coastal upwelling systems (e.g. off California) during this time interval, suggesting that the efficiency of the biological carbon pump was probably sufficiently enhanced in these regions during the MDM to have significantly increased the transport of atmospheric CO2 to the deep ocean. In addition, the coeval extension of the area of surface water stratification in both the Southern Ocean and the North Pacific, which decreased CO2 release to the atmosphere, led to further enhanced atmospheric CO2 drawn-down and thus contributed significantly to late Pliocene/early Pleistocene cooling.
(Climate of the Past Discussions [Climate of the Past Preprints]. vol. 8, n° 1814-9340, pp. 669-694, 01/03/2012)
LOCEAN, IPSL, ENS-PSL, PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, IP Paris, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, CAU, GEOMAR, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Silicic acid flux to the ocean from tidal permeable sediments: A modeling study
Sandy sediments of tidal beaches are poor in reactive substances because they are regularly flushed by significant flow caused by tidal forcing. This transport process may significantly affect the flux of reactive solutes to the ocean. A two dimensional model coupling the Richards equation that describes the flow in permeable sediments and the conservation equation of the silicic acid was developed to simulate the evolution of the silicic acid concentration into a variably saturated porous media submitted to tidal forcing. A detailed algorithm of drainage zone under tidal forcing and numerical methods needed to solve it are properly presented. Flux to the ocean has been estimated. The silicic acid concentration displays a permanent lens with low silicic acid concentration at the top of the tidal zone. This lens that results from the tidal forcing, presents weak variations of area during the tidal cycle. Silicic outflux to the ocean increases with increasing beach slope, hydraulic conductivity and tidal range. Simulations reveal that the total silicic acid flux to the ocean from the coastal marine sands can be considered as significant compared to the flux supplied by the rivers. These results may alter the previously published global budget of the silicic acid to the ocean.
(Computers & Geosciences. vol. 43, n° 0098-3004, pp. 52-62, 28/02/2012)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BACCHUS, Inria, UB, CNRS, IMB, UB, Bordeaux INP, CNRS, MC2, Inria, UB, CNRS
Calibration of sorption and biodegradation of micropollutants in a biokinetic model: New experimental protocol and first results
An innovative experimental strategy is proposed to calibrate sorption and biodegradation modelling parameters. The protocol was based on batch experiments simulating the different conditions occurring in a full-scale activated sludge reactor. The studied conditions were the redox condition (aerobic, anoxic) and the substrate condition (no other substrate, carbon and nitrogne substrate, only nitrogen substrate). Thanks to the monitoring of dissolved and sorbed concentrations of micropollutant, robust mass balances could be performed. We succeeded in determining easily modelling parameter values associated to each condition. An application of the strategy is presented for a beta blocker (atenolol). We will apply this procedure to the other studied substances (other pharmaceuticals, alkylphenols, polycyclic aromatic hydrocarbons and pesticides).
(pp. 1, 26/02/2012)
UR MALY, IRSTEA, UM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Present deep-submarine canyons activity in the Bay of Biscay (NE Atlantic)
Present sedimentation in three canyons of the Bay of Biscay (Audierne, Blackmud and Capbreton) is studied by the combined analysis of cores and current meter data collected over a 7 month period. At the current meter mooring locations, interface cores were collected to characterize the recent sedimentation processes. In the two canyons located in the Northern part of the Bay of Biscay (Audierne and Blackmud), there is no evidence of recent sedimentary deposits. Canyons are by-passing or erosive areas. In the southern part of the Bay of Biscay (Capbreton), recent turbidite are deposited. In the three canyons, current meters recorded energetic currents with velocities showing alternating upslope and downslope motions, and a period corresponding to the semi-diurnal component M2. These currents are supposed to be related to deep internal tides. The high speed of the current (1 m/s) in Audierne and Blackmud is consistent with the lack of preservation of recent sediments on the canyon floors. In Capbreton Canyon, the magnitude of currents is less and recent turbidites are preserved. In addition to periodical current motion, small magnitude gravity event corresponding to a low-concentration turbulent surge or a high-concentration nepheloid layer initiated during a storm was recorded during the mooring period. These results suggest that deep-sea canyons in the Bay of Biscay have behaviour at present varying between by passing or erosion areas and sediment trapping. These examples suggest that sediments are moved up and down by low-energy, tide-initiated hydrodynamic events during most of the time. During higher magnitude, short-duration gravity events, the sediments are transferred down canyon towards the deep sea.
(Marine Geology. vol. 295-298, n° 0025-3227, pp. 113-127, 15/02/2012)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, SHOM, LDO, INSU - CNRS, UBO EPE, CNRS
EVOLUTION OF HARD X-RAY SOURCES AND ULTRAVIOLET SOLAR FLARE RIBBONS FOR A CONFINED ERUPTION OF A MAGNETIC FLUX ROPE
(The Astrophysical Journal. vol. 746, n° 0004-637X, pp. 17, 10/02/2012)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LESIA, UPMC, INSU - CNRS, CNRS, PSL, UPD7, CNRS, ULiège
Behavioural indicators of welfare in farmed fish.
Behaviour represents a reaction to the environment as fish perceive it and is therefore a key element of fish welfare. This review summarises the main findings on how behavioural changes have been used to assess welfare in farmed fish, using both functional and feeling-based approaches. Changes in foraging behaviour, ventilatory activity, aggression, individual and group swimming behaviour, stereotypic and abnormal behaviour have been linked with acute and chronic stressors in aquaculture and can therefore be regarded as likely indicators of poor welfare. On the contrary, measurements of exploratory behaviour, feed anticipatory activity and reward-related operant behaviour are beginning to be considered as indicators of positive emotions and welfare in fish. Despite the lack of scientific agreement about the existence of sentience in fish, the possibility that they are capable of both positive and negative emotions may contribute to the development of new strategies (e.g. environmental enrichment) to promote good welfare. Numerous studies that use behavioural indicators of welfare show that behavioural changes can be interpreted as either good or poor welfare depending on the fish species. It is therefore essential to understand the species-specific biology before drawing any conclusions in relation to welfare. In addition, different individuals within the same species may exhibit divergent coping strategies towards stressors, and what is tolerated by some individuals may be detrimental to others. Therefore, the assessment of welfare in a few individuals may not represent the average welfare of a group and vice versa. This underlines the need to develop on-farm, operational behavioural welfare indicators that can be easily used to assess not only the individual welfare but also the welfare of the whole group (e.g. spatial distribution). With the ongoing development of video technology and image processing, the on-farm surveillance of behaviour may in the near future represent a low-cost, noninvasive tool to assess the welfare of farmed fish.
(Fish Physiology and Biochemistry. vol. 38, n° 0920-1742, pp. 17-41, 04/02/2012)
CCMAR, UAlg, NOFIMA, Tecnologia & Ricerca, CNPS, UP11, CNRS, IO-PAN, PAN, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ARU, UAB, IMR, UiB
Calage de la sorption et de la biodégradation de micropolluants dans un modèle biocinétique : nouveau protocole expérimental et premiers résultats
An innovative experimental strategy is proposed to calibrate sorption and biodegradation modelling parameters. The protocol was based on batch experiments simulating the different conditions occurring in a full-scale activated sludge reactor. The studied conditions were the redox condition (aerobic, anoxic) and the substrate condition (no other substrate, carbon and nitrogne substrate, only nitrogen substrate). Thanks to the monitoring of dissolved and sorbed concentrations of micropollutant, robust mass balances could be performed. We succeeded in determining easily modelling parameter values associated to each condition. An application of the strategy is presented for a beta blocker (atenolol). We will apply this procedure to the other studied substances (other pharmaceuticals, alkylphenols, polycyclic aromatic hydrocarbons and pesticides).
(pp. 1, 01/02/2012)
UR MALY, IRSTEA, UM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS