Diatoms and biomarkers evidence for major changes in sea ice conditions prior the instrumental period in Antarctic Peninsula
The Antarctic Peninsula (AP) has been identified as one of the most rapidly warming region on Earth. Satellite monitoring currently allows for a detailed understanding of the relationship between sea ice extent and duration and atmospheric and oceanic circulations in this region. However, our knowledge on oceaneiceeatmosphere interactions is still relatively poor for the period extending beyond the last 30 years. Here, we describe environmental conditions in Northwestern and Northeastern Antarctic Peninsula areas over the last century using diatom census counts and diatom specific biomarkers (HBIs) in two marine sediment multicores (MTC-38C and-18A, respectively). Diatom census counts and HBIs show abrupt changes between 1935 and 1950, marked by ocean warming and sea ice retreat in both sides of the AP. Since 1950, inferred environmental conditions do not provide evidence for any trend related to the recent warming but demonstrate a pronounced variability on pluri-annual to decadal time scale. We propose that multi-decadal sea ice variations over the last century are forced by the recent warming, while the annual-to-decadal variability is mainly governed by synoptic and regional wind fields in relation with the position and intensity of the atmospheric low-pressure trough around the AP. However, the positive shift of the SAM since the last two decades cannot explain the regional trend observed in this study, probably due to the effect of local processes on the response of our biological proxies.
(Quaternary Science Reviews. vol. 79, n° 0277-3791, pp. 99-110, 01/11/2013)
LOCEAN, IPSL, ENS-PSL, PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, IP Paris, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ULaval, INSU - CNRS, CNRS
Early morphofunctional plasticity of microglia in response to acute lipopolysaccharide
Within the central nervous system (CNS) the traditional role of microglia has been in brain infection and disease, phagocytosing debris and secreting factors to modify disease progression. This led to the concept of “resting” versus “activated” microglia. However, this is misleading because multiple phenotypic and morphological stages of microglia can influence neuronal structure and function in any condition and recent evidence extends their role to healthy brain homeostasis. The present work was thus aimed at reappraising the concept of morphofunctional activity of microglia in a context of peripheral acute immune challenge, where microglial activity is known to be modified, using the new state-of-the-art techniques available. To do so, mice were injected peripherally with lipopolysaccharide, a potent inducer of cerebral inflammation, and we assessed early cytokines production, phenotype, motility and morphology of microglial cells. Our results showed that LPS induced a widespread inflammatory response both peripherally and centrally, as revealed by the quantification of cytokines levels. We also found an alteration of microglial motility that was confirmed by in vivo studies showing an overall reduction of microglial processes length in the hippocampus of LPS-treated animals. Finally, analysis of various surface receptors expression revealed that LPS did not significantly impact microglial phenotype 2 h after the injection but rather induced an increase of CD11b+/CD45high cells. These latter may be at the vasculature, at the CNS vicinity, or may have invaded the CNS.
(Brain, Behavior, and Immunity. vol. 34, n° 0889-1591, pp. 151-158, 01/11/2013)
NutriNeuro, INRA, UB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Anthropogenic sources and biogeochemical reactivity of particulate and dissolved Cu isotopes in the turbidity gradient of the Garonne River (France)
High precision MC-ICP-MS Cu isotope measurements were performed on suspended particulate matter (SPM) and filtered water sampled along the turbidity gradient of the fluvial Gironde Estuary (Garonne Branch), following a summer lasting period of low freshwater discharge. High Cu concentrations (up to ~ 200 μg/g) in particulate organic carbon (POC)-rich (up to ~ 14%) particles upstream from the Maximum Turbidity Zone (MTZ) coincide with the most negative δ65Cu values (down to − 0.39‰). This suggests the preferential uptake of light Cu isotopes by phytoplankton or anthropogenic contamination from CuSO4 fungicides related to intensive wine farming in the area (δ65Cu = − 0.37‰ for vineyard soils). Suspended particulate matter samples in the MTZ exhibit lower Cu concentrations (~ 35 μg/g) and heavier isotopic compositions (δ65Cu = − 0.20‰ in average), as recorded by other samples from the Gironde Watershed. Along the fluvial estuary, dissolved Cu is mostly enriched in heavy isotopes (up to δ65Cu = + 0.21‰), but negative signatures down to δ65Cu = − 0.66‰ occur near the city of Bordeaux. Release of dissolved Cu was attributed to the mineralization of organic matter with a total addition of ~ 600 ng/L in the fluvial estuary. Continuously decreasing amounts of dissolved Cu added with distance suggest that the observed Cu release evolved towards completion in the MTZ and contributed to negative values for dissolved Cu isotopes, as modeled by a Rayleigh process. Urban wastewater effluents probably also contribute to both (i) the dissolved Cu addition (10–20%) in the MTZ and (ii) negative Cu isotope signatures. Further work is necessary to assess the respective roles of anthropogenic sources and biogeochemical fractionation processes. Accordingly, the present study provides new insights into the potential of Cu isotopes for fingerprinting sources and mechanisms involved in the biogeochemical cycle of Cu in temperate aquatic environments impacted by anthropogenic activities.
(Chemical Geology. vol. 359, n° 0009-2541, pp. 125-135, 01/11/2013)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ULB
Recent discovery of Paranthura japonica Richardson, 1909 (Crustacea: Isopod: Paranthuridae) in European marine waters (Arcachon Bay, Bay of Biscay)
The Asiatic isopod Paranthura japonica Richardson, 1909 was collected in 2007 in Arcachon Bay (SW France), where the species occurs in a variety of habitats, both in the intertidal and at shallow depths. This species, native to the Sea of Japan, may have been accidentally introduced in Arcachon Bay with oyster transfers or as fouling on ship hulls.
(BioInvasions Records. vol. 2, n° 2242-1300, pp. 215-219, 27/09/2013)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
A bioturbation classification of European marine infaunal invertebrates
Bioturbation, the biogenic modification of sediments through particle reworking and burrow ventilation, is a key mediator of many important geochemical processes in marine systems. In situ quantification of bioturbation can be achieved in a myriad of ways, requiring expert knowledge, technology, and resources not always available, and not feasible in some settings. Where dedicated research programmes do not exist, a practical alternative is the adoption of a trait‐based approach to estimate community bioturbation potential (BPc). This index can be calculated from inventories of species, abundance and biomass data (routinely available for many systems), and a functional classification of organism traits associated with sediment mixing (less available). Presently, however, there is no agreed standard categorization for the reworking mode and mobility of benthic species. Based on information from the literature and expert opinion, we provide a functional classification for 1033 benthic invertebrate species from the northwest European continental shelf, as a tool to enable the standardized calculation of BPc in the region. Future uses of this classification table will increase the comparability and utility of large‐scale assessments of ecosystem processes and functioning influenced by bioturbation (e.g., to support legislation). The key strengths, assumptions, and limitations of BPc as a metric are critically reviewed, offering guidelines for its calculation and application.
(Ecology and Evolution. vol. 3, pp. 3958-3985, 17/09/2013)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UGent
Evaluation of the deleterious effects of heavy metals and pesticides on early life stages and gametes of the Pacific Oyster, Crassostrea gigas : application to the pollution context of the Arcachon Bay
The coastal areas are subject to multiple anthropogenic pressures including chemical pollution that can pose a real risk to the sustainability of aquatic species. The Arcachon Bay, macrotidal lagoon located on the French Atlantic coast, is the important ecosystem for oyster farming. But for several years, the oyster farms face lower recruitment and high mortality of oyster spat. Chemical contamination of the environment as a factor that may contribute to the observed effects on oysters has so far not been investigated.The present thesis aimed at evaluating through different approaches, of the potential toxicity of heavy metals and pesticides representative of the Arcachon Bay contamination on the early life stages of the Pacific oyster, Crassostrea gigas. Embryotoxicity, genotoxicity and expression levels of eleven targeted genes were studied. Firstly, different pesticides (S-metolachlor, irgarol, and diuron) and metals (copper and cadmium) were separately tested to determine their spectrum of effects. It were shown that exposure of gametes and embryos of oyster to environmental concentrations of pesticides and copper increased developmental abnormalities and DNA damage, and reduced fertilization success and affected offpring quality. Cadmium, meanwhile, showed no embryotoxic and genotoxic effects at the concentrations found in the Arcachon Bay. Metabolites of metolachlor, metolachlor ESA and metolachlor OA, are found in the Arcachon Bay at higher concentrations than their parent compound. The results showed that these metabolites were less embryotoxic and genotoxic on oyster embryos and spermatozoa than metolachor. Significant changes in expression of genes involved in antioxidant defense were observed for oyster larvae exposed to metolachlor and metolachlor ESA. Toxicity of mixtures of pesticides representative of the Arcachon Bay contamination with and without copper was then evaluated. Exposures of oyster embryos to these mixtures lead to development defects, DNA damage and changes in the expression of genes involved mainly in oxidative stress responses. Finally, mapping of toxicity of sediments from the Arcachon Bay was conducted for four seasons of 2011 with the oyster embryo-larvae assay. Sediments collected from Arguin exhibited low toxicity, regardless any season. In contrast, sediments from Le Tès showed higher toxicity in spring and summer seasons compared to winter season.From this work, it can be hypothesized that chemical contamination of the Arcachon Bay represents a threat for oyster reproduction and development.
(17/09/2013)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
A Compilation of Silicon, Rare Earth Element and Twenty-One other Trace Element Concentrations in the Natural River Water Reference Material SLRS-5 (NRC-CNRC)
The natural river water certified reference material SLRS-5 (NRC-CNRC) was routinely analysed in this study for major and trace elements by ten French laboratories. Most of the measurements were made using ICP-MS. Because no certified values are assigned by NRC-CNRC for silicon and 35 trace element concentrations (rare earth elements, Ag, B, Bi, Cs, Ga, Ge, Li, Nb, P, Rb, Rh, Re, S, Sc, Sn, Th, Ti, Tl, W, Y and Zr), or for isotopic ratios, we provide a compilation of the concentrations and related uncertainties obtained by the participating laboratories. Strontium isotopic ratios are also given. Le matériau de référence certifié d'eau de rivière naturelle SLRS-5 (NRC-CNRC) est analysé régulièrement comme contrôle qualité par dix laboratoires français étudiant les éléments majeurs et en trace dans les solutions naturelles. La plupart des mesures sont réalisées par ICP-MS. Le silicium et 35 éléments en trace (terres rares, Ag, B, Bi, Cs, Ga, Ge, Li, Nb, P, Rb, Rh, Re, S, Sc, Sn, Th, Ti, Tl, W, Y et Zr) ne sont pas certifiés par NRC-CNRC. Aucun rapport isotopique n'est disponible. Nous proposons, pour ces éléments, des valeurs moyennes et leurs incertitudes associées obtenues par les différents laboratoires participants. Le rapport isotopique de Sr est aussi mesuré.
(Geostandards and Geoanalytical Research. vol. 37, n° 1639-4488, pp. 449-467, 16/09/2013)
CRPG, INSU - CNRS, UL, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GR, UR, INSU - CNRS, CNRS, UAG, INSU - CNRS, UM, CNRS, DRCP, CEA-DES (ex-DEN), CEA, LISA (UMR_7583), INSU - CNRS, UPD7, UPEC UP12, CNRS, LEGOS, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, GET, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, HSM, IRD, UM2, INSU - CNRS, CNRS, LGE, UPD7, IPG Paris, LEGOS, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS
Stochastic modelling using large data sets : applications in ecology and genetics
There are two main parts in this thesis. The first one concerns valvometry, which is here the study of the distance between both parts of the shell of an oyster, over time. The health status of oysters can be characterized using valvometry in order to obtain insights about the quality of their environment. We consider that a renewal process with four states underlies the behaviour of the studied oysters. Such a hidden process can be retrieved from a valvometric signal by assuming that some probability density function linked with this signal, is bimodal. We then compare several estimators which take this assumption into account, including kernel density estimators.In another chapter, we compare several regression approaches, aiming at analysing transcriptomic data. To understand which explanatory variables have an effect on gene expressions, we apply a multiple testing procedure on these data, through the linear model FAMT. The SIR method may find nonlinear relations in such a context. It is however more commonly used when the response variable is univariate. A multivariate version of SIR was then developed. Procedures to measure gene expressions can be expensive. The sample size n of the corresponding datasets is then often small. That is why we also studied SIR when n is less than the number of explanatory variables p.
(16/09/2013)
IMB, UB, Bordeaux INP, CNRS, CQFD, IMB, UB, Bordeaux INP, CNRS, Inria, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Water monitoring of emerging pesticides in France : Organization of a screening study from prioritization to measurements
The Water Framework Directive (WFD) has set up a European list of 41 Priority Substances (PS) which have to be regularly monitored in European waters. Moreover, it requires Member States to establish national lists of substances to be monitored at river basin level. Despite these provisions, it is widely recognised by the scientific community that several substances of emerging concern are currently overlooked and as a result they are not adequately monitored by national authorities. As part of the implementation of the National Action Plan on Micropollutants in the Aquatic Environment (October 2010), the French Ministry of Ecology decided to implement an innovative and comprehensive approach to improve national monitoring programmes under the WFD. This includes the setting-up of a watch list of substances to be investigated at the national level in order to acquire missing information about the level of exposure of emerging contaminants in the aquatic environment and allow regular updating of the list of River Basin-Specific Pollutants to be regularly monitored. Concurrently, an Action Plan on Drug Residues in Water, co-led by the Ministries of Ecology and Public Health, was published in May 2011. This action plan supports prioritisation of pharmaceuticals for which screening studies are needed in view of the implementation of emission reduction measures.
(02/09/2013)
INERIS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ISA, UCBL, INC-CNRS, CNRS, LPTC, UB, CNRS
Export of 13C-depleted dissolved inorganic carbon from a tidal forest bordering the Amazon estuary
Tidal wetlands play a significant role in the coastal carbon cycle and exchange material with the atmosphere and coastal ocean. Here, we report on changes in dissolved inorganic carbon speciation and isotopic composition throughout a 24 h cycle (2 tidal cycles) in Feb. 2007 in a channel connecting the Amazon estuary to the basin of a tidal forest. At this site, tropical forest soils are inundated at high tide by estuarine freshwater, and temporal concentration changes in the channel reflect exchanges between the forest and estuary. Our data show an export of dissolved inorganic carbon (DIC) in the form of excess CO2 and, to a much lesser extent, CH4. However, the tidal forest traps suspended sediments. Mixing plots of DIC versus conductivity showed that the DIC originated from the tidal forest soil, with a negligible contribution from the local watershed. Evolution of the isotopic signature of DIC reveals a 13C-depleted source (-56.9 ± 3.3‰), presumably originating from a dominant methanogenic pathway of carbon mineralization followed by almost complete CH4 oxidation in the organic clay-rich freshwater soil.
(Estuarine, Coastal and Shelf Science. vol. 129, n° 0272-7714, pp. 23-27, 01/09/2013)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GET, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], ULCO, BOREA, MNHN, IRD, UPMC, CNRS