Evidence for oceanic oxygen depletion in the face of cooling in the early Pleistocene
Future climate change is predicted to significantly impact ocean circulation and, potentially, to reduce ocean oxygenation. Paradoxically, the transition from the warm Pliocene, often held as an analog for a future, warmer Earth, to the cool Pleistocene appears to accompany a decrease in intermediate water oxygenation. The Plio-Pleistocene cooling begins with the onset of major Northern Hemisphere glaciation, around 3.0-2.7 million years ago (Ma). High latitude cooling and extension of the polar ice caps led to cooling of the deep ocean and shoaling of the thermocline. The transition culminated in the cooling of the whole surface ocean and establishment of strong zonal and meridional atmospheric circulation from 2.0 Ma. A compilation of high-resolution nitrogen isotope records from the eastern equatorial Pacific, North Pacific, and the Arabian Sea and a global multi-site survey, indicates that regional intensification of oxygen minimum zones (OMZs) and expansion of water column denitrification accompanied the cooling and circulation changes at ~2.0 Ma. Large-scale open ocean suboxia intensified with the inception of a modern polar frontal system, despite lower temperatures and thus higher initial oxygen contents of the mode waters themselves. This likely reflects the increased importance of aged mode waters as the principle conduit of nutrients and oxygen to the OMZs. These results stress how climate-related changes in circulation may complicate our ability to predict ocean biogeochemical changes on a changing Earth.
(. vol. 41, pp. 0214, 01/12/2011)
URI, PALEOPROXUS, LOCEAN, IPSL, ENS-PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CAU
Impact of toxicant exposure on the proteomic response to intertidal condition in Mytilus edulis
Intertidal blue mussels display physiological adaptations to emersion-submersion cycle that can be impacted by response to chemicals. In order to study the interference of cellular response to pollutants on intertidal physiology, we analysed proteomic (2-DE) responses in gills of mussels exposed for 14 days to regular emersion (intertidal condition) or continuous submersion (subtidal condition) and to a mixture (B[a]P/ phenantrene) of polycyclic aromatic hydrocarbons (PAHs). Antioxidant activities were measured as general stress markers. In clean context, emersion generated several over-expressions of proteins mainly involved in cytoskeleton, chaperoning, energetic metabolism and transcription regulation. Mussels exposed to PAHs showed equivalent accumulation levels of contaminants in both physiological conditions but an increased GST activity specifically in intertidal context, highlighting the high degree of stress underwent in this group, as well as over-expressions of Cu/Zn SOD and stress proteins in subtidal context. Presence of contaminants partly impacted the response to emersion: cytoskeletal rearrangements and energetic adjustments were mostly maintained whereas stress response was dramatically altered. These findings highlight the potential adverse effects of toxicants on physiological adjustments linked to air-exposure, thus suggesting to take into account in the evaluation of environmental risk the multiplicity of stresses that wild animals are likely to encounter.
(Comparative Biochemistry and Physiology - Part D: Genomics and Proteomics. vol. 6, n° 1744-117X, pp. 357-369, 01/12/2011)
SEBIO, INERIS, URCA, ULH, NU, URCA, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UNIROUEN, NU, INSERM, DC2N, UNIROUEN, NU, INSERM
High-latitude obliquity as a dominant forcing in the Agulhas current system
The Agulhas Current transport of heat and salt from the Indian Ocean into the South Atlantic around South Africa (Agulhas leakage), can affect the Atlantic meridional overturning circulation (AMOC) and, thus, influence global climate. However, efforts to elucidate forcing mechanisms connecting the Agulhas leakage with the upstream dynamics of the current have been hampered by a lack of climate records extracted from the area where the Agulhas current originates. We determine 800-kyr sea surface temperature (SST) and salinity (SSS) records from the "precursor" region of the Agulhas current and show that these records contain strong 100-kyr and 41-kyr cycles. This latter obliquitydriven cycle is nearly in phase with changes in the annual mean insolation and air temperature at high southern latitudes. In contrast, our SST and SSS records did not reveal precession-driven cycles, which is surprising given the lowlatitude location of the upstream Agulhas current. Together, this indicates that the dynamics of the Agulhas current system is mainly controlled by high latitude obliquity through its influence on the position of the Southern Hemisphere subtropical front (STF) and its associated westerlies. Our study demonstrates that obliquity may drive an important part of the 100 kyr cycles observed in the system rather than precession. Our results also suggest that a stronger Agulhas current, associated with a northward shift of the wind system dur-
(Climate of the Past. vol. 7, n° 1814-9324, pp. 1285 - 1296, 26/11/2011)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, CEA, CNRS
Impacts of habitat contamination on the health of declining American and European eel populations
This research project is a joint initiative of researchers from Québec and France. Its general objective is to examine the relationships between pollution, both inorganic and organic, and the health of Atlantic eels in the Gironde and the St Lawrence estuaries.
(pp. 1, 13/11/2011)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IRSTEA, UR EPBX, CEMAGREF
ECHIBIOTEB : Outils innovants d’Échantillonnage, d’analyses CHImiques et BIOlogiques pour le suivi de Traitements avancés des Eaux usées et des Boues
Le projet ECHIBIOTEB s’inscrit dans un cadre de recherche industrielle et s’intègre principalement dans l’axe thématique n°5 de l’appel à projets ECOTECH. Il fait suite au projet AMPERES (Projet ANR PRECODD 2005, Analyse de micropolluants prioritaires et émergents dans les rejets et les eaux superficielles) et complète l'évaluation des filières de procédés avancés de traitement des eaux et des procédés de traitement des boues étudiées dans le projet ARMISTIQ (Projet Convention ONEMA-Cemagref 2010). Plus précisément, il prévoit le développement et/ou l'amélioration des connaissances sur des outils et techniques innovantes d'échantillonnage et de mesures chimiques et biologiques pour la caractérisation de la qualité des eaux urbaines et des boues avant et après traitement. Les outils innovants mis en oeuvre sont des échantillonneurs intégratifs pour améliorer la représentativité et la sensibilité des résultats d'analyses des micropolluants, des méthodologies de screening (GC-2D-TOF, SPME/GC/TOF et SPME/LC/TOF) pour identifier de nouvelles molécules et produits de dégradation, des biotests in vitro et in vivo pour prendre en compte les effets biologiques des mélanges, une démarche "effect-directed analysis" (EDA) pour isoler et permettre l'identification de nouvelles molécules actives, et des tests pour la caractérisation in situ de la matière organique dissoute susceptible de moduler la toxicité des micropolluants. Le projet s’intéresse au traitement complémentaire des eaux usées issues des procédés secondaires, d'une part, aux procédés intensifs compacts (oxydation à l’ozone, aux rayons UV, adsorption sur charbon actif, osmose inverse) plutôt applicables aux collectivités de taille importante ou à forte pression foncière, et d'autre part, aux procédés extensifs autonomes et de taille moins ramassée (zones humides, écoulement sur milieu filtrant dans le sol naturel ou rapporté), procédés souvent rencontrés dans les petites collectivités, mais envisageables en sortie de traitement secondaires de boues activées conventionnelles de moyenne taille. Le choix des procédés étudiés de traitement de boues s'est porté sur le compostage (avec digestion anaérobie en amont), plutôt adapté aux grandes collectivités, et la rhizofiltration caractéristique de petites stations. La mise en oeuvre d'un panel aussi large d'outils innovants est en soi originale et devrait permettre d'améliorer les connaissances sur leurs domaines d'application comparés et leur complémentarité. Au terme du projet, des guides de bonne exploitation des différents outils innovants pour la caractérisation des procédés de traitement des eaux et des boues seront disponibles. Nous proposerons aussi des stratégies de déploiement de ces outils et d'interprétation des données issues de ces technologies innovantes pour faciliter les schémas de gestion et la prise de décision par les industriels et les collectivités territoriales vis à vis de l’implémentation de la DCE. L'application particulièrement novatrice de ces outils à des procédés avancés de traitement des eaux devrait permettre d'établir une liste (non exhaustive) de nouveaux composés indésirables et d’anticiper les législations futures. Au terme du projet, un bilan de la comparaison de l'efficacité des procédés (eaux et boues) étudiés sera dressé (en lien avec le projet ARMISTIQ) et une méthodologie de diagnostic des performances des procédés de traitement des eaux usées et des boues vis à vis des micropolluants sera proposée.
(pp. 1, 08/11/2011)
UR MALY, CEMAGREF, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, INERIS, UP11, IRSTEA
Du terrain aux modèles numériques : modélisation des jökulhlaups du système fluviatile Þjórsá-Tungnaá (Sud-Islande)
(01/11/2011)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IRSTEA, CSIRO ESRE, CSIRO, OASU, UB, INSU - CNRS, ULR, CNRS, INRAE, LGO, UBS, IFREMER, UBO EPE, CNRS
Impacts morpho-sédimentaires des jökulhlaups fini-pléistocènes et holocènes du système fluviatile Þjórsá-Tungnaá (Sud-Islande)
(01/11/2011)
OASU, UB, INSU - CNRS, ULR, CNRS, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LGO, UBS, IFREMER, UBO EPE, CNRS, ADES, UBM, CNRS, IRSTEA, CSIRO ESRE, CSIRO
Failure processes and gravity-flow transformation revealed by high-resolution AUV swath bathymetry on the Nice continental slope (Ligurian Sea)
The continental slope offshore Nice is a natural laboratory to investigate submarine landslides and gravity-flow processes. Using EM300 bathymetry data (spatial resolution of 25 m), about 250 scars with volume less than 8 × 108 m3 were identified. The AUV bathymetric data (spatial resolution of 2 m) revealed a greater number of scar-related failures with two main morphologies: some scars are affected by retrogressive processes of erosion, suggesting failures were triggered a long time ago, while other scars exhibit no evidence of post-failure erosion, suggesting they could have been triggered recently. Downslope from the scars, there are scattered blocks, on average 5-m high and 40-m wide, and well-developed asymmetrical waves, on average 2-m high and 20-m in wavelength. Such evolution could be evidence for the transformation of the remobilized deposits into cohesive flows then turbulent flows. Such transformation took place over a distance of less than 6-8 km.
(Submarine mass movements and their consequences. Advances in Natural and Technological Hazards Research series. vol. 31, pp. 451-461, 12/10/2011)
GEOAZUR 6526, IRD, UPMC, UNS, INSU - CNRS, UniCA, CNRS, GM, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Orbital timing of the Indian, East Asian and African boreal monsoons and the concept of a 'global monsoon',
Our understanding of monsoon circulation timing's at the orbital scale is currently a matter of debate. Here, we compare previous and recently published results of Indian, East Asian, West African and East African monsoon variability. We note different timings between the East African, West African, Indian and East-Asian monsoon systems for the most recent 45 ka, where the age models are constrained by AMS dating. On this basis, we construct different orbital forcing "reference curves" and apply them to the 200 ka time period for the different monsoon systems. Our results indicate that the 'global monsoon' concept at the orbital scale is a misnomer. We find real regional differences in the timing of the monsoon response to orbital forcing and differences in the weight of precession and obliquity in the monsoon records. This work highlights the necessity of studies aimed at understanding the underlying physics of these regional response patterns. This is crucial to a better understanding of monsoon dynamics and improved climate model simulations and comparisons with proxy data
(Quaternary Science Reviews. vol. 30, n° 0277-3791, pp. 3705-3715, 10/10/2011)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GEOAZUR 6526, IRD, UPMC, UNS, INSU - CNRS, UniCA, CNRS
Effects of uranium uptake on transcriptional responses, histological structures and survival rate of the crayfish Procambarus clarkii
This work aims to investigate the accumulation levels and effects (transcriptional responses, histopathology and survival rate) associated with a wide range of dissolved uranium (U) concentrations (0, 0.03, 0.6, 4 and 8. mg/L of U) on adult male crayfish Procambarus clarkii during 4 (T4) and 10 (T10) days of exposure. The follow-up of the crayfish mortality showed that P. clarkii was highly resistant to U. Increasing waterborne U concentrations led to increasing bioaccumulation in key crayfish organs and increasing histological damages. U distribution in tissues was also evaluated using transmission electron microscopy and showed the presence of a detoxified form of U in the gill's epithelium in the shape of flakes. Expression levels of mitochondrial genes (cox1, atp6 and 12S gene) and genes involved in oxidative stress (sod(Mn) and mt) were examined together with the housekeeping gene 18S. atp6 and mt genes of P. clarkii were cloned and sequenced before analysis. Significant correlations were observed between U bioaccumulation and the down-regulation of both cox1 and sod(Mn) genes. This work provides a first U toxicogenomic and histopathological pattern of P. clarkii, identify U biomarkers and associate gene expression endpoints to accumulation levels. It also provides new insights into the mechanisms involved in U stress. © 2011.
(Ecotoxicology and Environmental Safety. vol. 74, n° 0147-6513, pp. 1800--1807, 01/10/2011)
IRSN/DEI/SECRE/LRE, IRSN/DEI/SECRE, IRSN, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS