Methane sources, sinks and fluxes in a temperate tidal lagoon: The Arcachon Lagoon (SW France)
(Estuarine, Coastal and Shelf Science. vol. 89, n° 0272-7714, pp. 256-266, 10/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LMTG, UT3, Comue de Toulouse, CNRS, COM, INSU - CNRS, CNRS, BOME, MNHN, UPMC, CNRS, LEMAR, IRD, IFREMER, UBO EPE, CNRS, CNRS
Early Holocene Laurentide Ice Sheet deglaciation causes cooling in the high-latitude Southern Hemisphere through oceanic teleconnection
The impact of the early Holocene Laurentide Ice Sheet (LIS) deglaciation on the climate at Southern Hemisphere high latitudes is studied in three transient simulations performed with a global climate model of the coupled atmosphere-ocean-vegetation system. Considering the LIS deglaciation, we quantify separately the impacts of the background meltwater fluxes and the changes in topography and surface albedo. In our model, the meltwater input into the North Atlantic results in a substantial weakening of the Atlantic meridional overturning circulation, associated with absence of deep convection in the Labrador Sea. Northward ocean heat transport by the Atlantic Ocean is reduced by 28%. This weakened ocean circulation leads to cooler North Atlantic Deep Water (NADW). Upwelling of this cool NADW in the Southern Ocean results in reduced surface temperatures (by 1°C to 2°C) here between 9 and 7 ka compared to an experiment without LIS deglaciation. Poleward of the polar front zone, this advective teleconnection between the Southern and Northern hemispheres overwhelms the effect of the "classical" bipolar seesaw mechanism. These results provide an explanation for the relatively cold climatic conditions between 9 and 7 ka reconstructed in several proxy records from Southern Hemisphere high latitudes, such as Antarctic ice cores. ,
(Paleoceanography. vol. 25, n° 0883-8305, pp. PA3204, 10/04/2026)
VU, TECLIM, ELI, UCLouvain, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, CLIM, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
Experimental toxicity and bioaccumulation of cadmium in freshwater periphytic diatoms in relation with biofilm maturity
A study was undertaken to examine cadmium accumulation in freshwater biofilm, its effects on biofilm development and on diatom community structure in laboratory experimental conditions. A suspension of a biofilm originated from the Riou-Mort River (South West France) was inoculated into three experimental units containing clean glass substrates under laboratory conditions. Settling and already developed biofilms were exposed to a Cd concentration of 100 μgL−1. Metal accumulation (total and intracellular metal content) in biofilms, dry weight and ash-free dry mass, diatom cell density and diatom community composition were analyzed. Both total and intracellular Cd accumulated by the biofilm throughout the experiment increased with duration of metal exposure. Biofilms in the course of maturation were showed higher Cd content and less effective development than settled biofilms. However diatom communities in younger biofilms exposed to Cd increased their tolerance to Cd by a highly significant development of Nitzschia palea. In contrast, Cd exposure had different effect in installed biofilm and taxonomic composition. These results indicate that mature biofilm may limit Cd accumulation into its architecture and protect diatom communities from the effects of metals.
(Science of the Total Environment. vol. 408, n° 0048-9697, pp. 552-562, 10/04/2026)
IRSTEA, UR REBX, CEMAGREF, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Viability of differentiated epilithic bacterial communities in the River Garonne (SW France)
Epilithic bacterial community viability was assessed on natural biofilm assemblages from environmentally contrasting locations over a 17-months period to determine if it reflects environmental conditions or conditions within the biofilm assemblage. Vital state was assessed by membrane integrity using LIVE/DEAD® BacLight staining kit. Samples were regularly collected in a large river, up and downstream of a large urban centre. Epilithic biomasses were similar between sites irrespective of the distinct water quality but varied temporarily, peaking up to 48 g AFDM m−2. Bacterial community composition assessed by 16S rDNA based PCR-DGGE significantly differed between sites. Bacterial densities (median of 2.5 × 1011 cell g AFDM−1) were stable whatever the sample origin or biomass. Viable bacterial fractions ranged between 13 and 83% of the total bacterial densities and were correlated with hydrological stability indicators (average of 41.9% during stable water periods, 62.4% during intermediate flow regimes and 50.0% during flow instability) and seasonal parameters. At the river section and epilithic community scales, consistent bacterial densities per unit of biomass could reflect a biofilm assemblage carrying capacity while variable membrane integrity likely integrates changes in the vital state of the community under changing environmental conditions.
(Hydrobiologia. vol. 637, n° 0018-8158, pp. 207-218, 10/04/2026)
CNRS, UR MALY, CEMAGREF, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Testing the Hypothesis of Fire Use for Ecosystem Management by Neanderthal and Upper Palaeolithic Modern Human Populations
Background: It has been proposed that a greater control and more extensive use of fire was one of the behavioral innovations that emerged in Africa among early Modern Humans, favouring their spread throughout the world and determining their eventual evolutionary success. We would expect, if extensive fire use for ecosystem management were a component of the modern human technical and cognitive package, as suggested for Australia, to find major disturbances in the natural biomass burning variability associated with the colonisation of Europe by Modern Humans. Methodology/Principal Findings: Analyses of microcharcoal preserved in two deep-sea cores located off Iberia and France were used to reconstruct changes in biomass burning between 70 and 10 kyr cal BP. Results indicate that fire regime follows the Dansgaard-Oeschger climatic variability and its impacts on fuel load. No major disturbance in natural fire regime variability is observed at the time of the arrival of Modern Humans in Europe or during the remainder of the Upper Palaeolithic (40-10 kyr cal BP). Conclusions/Significance: Results indicate that either Neanderthals and Modern humans did not influence fire regime or that, if they did, their respective influence was comparable at a regional scale, and not as pronounced as that observed in the biomass burning history of Southeast Asia.
(PLoS ONE. vol. 5, n° 1932-6203, pp. e9157, 10/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, PACEA, UB, CNRS, WITS
Rapid climatic variability in the western Mediterranean during the last 25,000 years from the high resolution pollen record ODP 976
(14/12/2009)
LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LCE, CNRS, UFC, UBFC, UHH
Sonochemical Disproportionation of Carbon Monoxide in Water: Evidence for Treanor Effect during Multibubble Cavitation
(Angewandte Chemie International Edition. vol. 48, n° 1433-7851, pp. 9529-9532, 07/12/2009)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSFC, ICSM - UMR 5257, CEA, ENSCM, INC-CNRS, UM, CNRS
Caractérisation de l'activité hydrosédimentaire dans le Système Turbiditique du Var (NO Méditerranée) et de son enregistrement dans l'archive sédimentaire
Le système turbiditique du Var présente la particularité d'être fréquemment parcouru par des écoulements gravitaires. Cela en fait un endroit privilégié pour étudier simultanément les facteurs déclenchant des courants de turbidité, leurs caractéristiques hydrodynamiques, leur contenu particulaire et les dépôts associés. Dans le cadre du projet Européen HERMES (6ème Programme Cadre), nous avons acquis pendant 2 ans dans le canyon du Var et dans la vallée turbiditique (1) des séries temporelles dans la colonne d'eau (30 m et 400 m au dessus du fond) sur la vitesse des courants, la température et le flux particulaire, et (2) des prélèvements répétés par carottage du sédiment de surface. Nos résultats mettent en évidence deux types de transport sédimentaire: (1) des écoulements gravitaires, et (2) des remises en suspension sur le fond par le Courant Nord. L'étude des caractéristiques hydrodynamiques des courants gravitaires permet de préciser nos connaissances sur leur mécanisme de formation. Les courants gravitaires peuvent être initiés par des déstabilisations dans le canyon ou par le plongement en mer de l'eau turbide du fleuve (courant de turbidité hyperpycnal). Ces derniers peuvent être générés lorsque le débit liquide du fleuve franchit un seuil de 306 m3.s-1 à l'embouchure, et à condition que la crue soit étendue à l'ensemble du réseau hydrographique. L'étude combinée des mesures sur les deux années et des faciès sédimentaires dans les dépôts du siècle dernier souligne la prépondérance des courants de turbidité hyperpycnaux, qui représentent 80 % des écoulements gravitaires. De plus, cette étude combinée montre que les écoulements de faible magnitude (résultant de petites instabilités ou de crues annuelles du fleuve) s'arrêtent généralement au débouché de la vallée supérieure et ne déposent du sédiment que sur une terrasse située à 70 m au dessus du fond de la vallée. Les courants gravitaires de grande magnitude (résultant de larges instabilités ou de crues majeures du fleuve) sont fortement érosifs dans la partie du système située avant le pied de pente, et déposent des séquences sédimentaires sur les terrasses, la levée, et localement dans le chenal. Le cadre chrono-stratigraphique établi pour l'étude des séquences sédimentaires permet de mieux contraindre la manière dont ces courants gravitaires sont enregistrés et préservés, à plusieurs échelles de temps.
(07/12/2009)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GM, IFREMER, DRO-EP, IFREMER
A new conceptual model for the deposition process of homogenite: Application to a cretaceous megaturbidite of the western Pyrenees (Basque region, SW France)
The north Pyrenean megaturbidite is a 19–63m exceptional thick bed deposited during the Late Turonian and extending over more than 90km in the Basque region Country (SW France). Its thickness varies from more than 63m to about 19m from east (Mauléon area) to west (Basque coast). It represents a total compacted volume of about 90km3 of carbonates. On the field, rare sedimentary structures are visible in the turbidite bed. They consist of laminar planar lamination and rare cross laminations in the eastern region and antidune-like structures in the western region. Five sites have been sampled with a vertical step of 50cm to 1m. Thin sections have been quantitatively analyzed for counting the terrigeneous fraction, the quartz grain size and the mineral orientation. The deposits fine westward, which suggests a source located in the east of the Mauléon Basin. This is consistent with the quartz grain orientation in the lower part of the megaturbidite. The deposits fine upward from medium sand to clayey-silt. This is consistent with the classical definition of homogenites and suggests that these kinds of deposits are turbidites. These observations also suggest that the term “megaturbidite” is appropriated for these deposits. The sedimentary analysis indicates that the deposit results from a single event. The volume of sediment involved in the process, as well as the quartz grain orientation indicating flow motion in the opposite direction of the initial flow and the antidune-like structure suggest the formation of reflected flows and the formation of standing waves over the complete water column in the Basque flysch sub-basins corresponding to a “Seiche effect”. The origin of the megaturbidite is probably an earthquake-generated collapse on the carbonate platform. This example allows providing a new conceptual model for the process of homogenite deposition. This model explains the deposition of thick, fine-grained, crudely-graded megaturbidites.
(Sedimentary Geology. vol. 222, n° 0037-0738, pp. 263-273, 01/12/2009)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, EGID
Nitrogen isotopic evidence for deglacial changes in nutrient supply in the eastern equatorial Pacific
The Eastern Equatorial Pacific (EEP) is a high nutrient-low chlorophyll region of the ocean. Downcore nitrogen isotope records from the EEP have been previously interpreted as a direct reflection of changes in nutrient consumption. However, the observed changes in sedimentary d 15 N since the last glacial maximum have no coherent relationship with export productivity or an inferred variation in the iron-to-nitrate ratio of the surface waters. Rather, downcore N isotope records in the EEP strongly resemble changes in the extent of water column denitrification as recorded in nearby sedimentary d 15 N records along the western margin of the Americas. This similarity is attributed to the overprinting of the N isotopic composition of nitrate in the EEP through the advection of nitrate westward from the margins in the subsurface. A local nitrogen isotope record of changes in the degree of nutrient consumption is extracted from the bulk sedimentary record by subtracting two different sedimentary d 15 N records of denitrification changes from two new EEP d 15 N records (TR163-22 and ODP Site 1240). The denitrification records used are from 1) the Central American margin (ODP Site 1242) and 2) the South American margin (GeoB7139-2). The degree of consumption in the surface waters declines rapidly from elevated values during the last glacial maximum to a pair of minima around 15 and 11-13 ka, and finally it increases into the Holocene. The derived EEP nitrogen isotope record indicates that the regional peak in export productivity occurred when the supply of nutrients exceeded the apparently high demand. The influx of nutrients during the deglaciation is attributed to the resumption of intense overturning in the Southern Ocean and the release of sequestered CO 2 and nutrient-rich, O 2 poor waters from the deep ocean. This has important implications for understanding the glacial-interglacial scale variation in intermediate water suboxia and water column denitrification.
(Paleoceanography. vol. 24, n° 0883-8305, 01/12/2009)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS