Isturitz, Oxocelhaya and Erberua Caves (Pyrénées-Atlantiques, France): geoarchaeological studies
Isturitz, Oxocelhaya and Erberua Caves are located in the foothills of the western Pyrenees. The landscape is hilly and is crossed by a wide valley with a small river, the Arberoue. Downstream, the river disappears into the limestone of Gaztelu Hill: this underground flow created the Erberua Cave. Above this natural tunnel we observe three fossil staged caves: Oxocelhaya, Isturitz and Rocafort. The Gaztelu Caves provide a major European Prehistoric archaeological site. The first recorded data came from the Isturitz Cave (1895), then from the Oxocelhaya Cave (1929) and finally from the Erberua Cave (1973) giving evidence of human occupation during the Mid-Upper Palaeolithic period. These archaeological remains are not uniformly distributed. In Erberua, some of the paintings suggest a Gravettian use of the cave but the works date from the Magdalenian time (Middle and/or Upper). In Oxocelhaya Cave, the settlement may date from Aurignacian time but the art works generally date from the Magdalenian time. In Isturitz Cave, the importance and diversity of the Aurignacian objects are exceptional and prove the permanent nature of this settlement where numerous activities took place. Also during the Gravettian time, an enormous quantity of material is proof of a very important human presence. During the Middle Magdalenian time, the activities are marked in particular by hundreds of portable art, this is why this cave has been described as one of the most important aggregation sites of the Pyrenees. The research team is multidisciplinary and was established in 2011 around twelve main objectives. Our contribution concerns the first two stages and includes speleologists, geologists and karstologists. The first stage was the charting of the numerous listed activities and the second stage will analyze their organization according to the topographic, geological and karstologic specificities of the Gaztelu Hill.
(27/08/2013)
TRACES, EHESS, UT2J, Comue de Toulouse, MCC, Inrap, CNRS, GET, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ADES, UBM, CNRS, Inrap, LEMTA, UL, CNRS
Record of historical mercury trends in sediments from the Laguna del Plata, Córdoba, Argentina
(25/08/2013)
UB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, SPE, CNRS, Bordeaux INP, UBM
Development of a larval bioassay using the calanoid copepod, Eurytemora affinis to assess the toxicity of sediment-bound pollutants
(Ecotoxicology and Environmental Safety. vol. 94, n° 0147-6513, pp. 60 - 66, 01/08/2013)
LEMA, ULH, NU, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS
Equatorial Pacific peak in biological production regulated by nutrient and upwelling during the late Pliocene/early Pleistocene cooling
The largest increase in export production in the eastern Pacific of the last 5.3 Myr (million years) occurred between 2.2 and 1.6 Myr, a time of major climatic and oceanographic reorganization in the region. Here, we investigate the causes of this event using reconstructions of export production, nutrient supply and oceanic conditions across the Pliocene-Pleistocene in the eastern equatorial Pacific (EEP) for the last 3.2 Myr. Our results indicate that the export production peak corresponds to a cold interval marked by high nutrient supply relative to consumption, as revealed by the low bulk sedimentary 15N/14N (δ15N) and alkenone-derived sea surface temperature (SST) values. This ∼0.6 million year long episode of enhanced delivery of nutrients to the surface of the EEP was predominantly initiated through the upwelling of nutrient-enriched water sourced in high latitudes. In addition, this phenomenon was likely promoted by the regional intensification of upwelling in response to the development of intense Walker and Hadley atmospheric circulations. Increased nutrient consumption in the polar oceans and enhanced denitrification in the equatorial regions restrained nutrient supply and availability and terminated the high export production event.
(Biogeosciences. vol. 10, n° 1726-4170, pp. 5663-5670, 01/08/2013)
LOCEAN, IPSL, ENS-PSL, PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, IP Paris, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, URI, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CAU
Iron and sulfur biogeochemical processes involved in mercury mobility and speciation in an artificial aquifer
Although many data are available on the Hg cycle in terrestrial surface aquatic environments, little is known on its behaviour in subsurface and deep aquifers where environmental conditions (anoxia, water saturation) may be favourable to Hg methylation. Bioavailability of Hg, a prerequisite for its methylation by sulphate or iron reducing bacteria, is mainly controlled by physico-chemical conditions and the strong affinity of Hg for organic matter or iron (oxy)hydroxides. This work presents an original experimental setup combining geochemical and microbiological approaches in order to imitate reactions observed in aquifers (i.e., Hg biosorption, solubilisation versus sequestration, speciation, dual effect of iron and sulphate). Two columns were filled in the lower half with sterile sand and in the upper half with a sterile mixture of sand and iron oxides, initially enriched with Hg(II). The water flow was ascendant. Five septa set regularly along the columns enabled water sampling from the different layers of the column without perturbing water flow or in-situ experimental conditions. After an abiotic rinsing period, the system was inoculated with a bacterial consortium and physico-chemical and microbial parameters were monitored in time and space. The inflowing groundwater was supplemented with sulphate (370 g.L-1 MgSO42-) and lactate (830 mg.L-1 sodium lactate) to encourage sulphate-reducing bacteria in the first column (A) and with molybdate (0.40 mmol.L-1) to inhibit sulphate reduction and glucose (10 g.L-1) to favour iron-reducing bacteria in the second column (B). At the end of the experiment (130 days), microbial methylation potentials were evaluated using stable isotope-spiked incubations, diversity using Denaturing Gel Gradient Electrophoresis (DGGE) followed by band sequencing and Fluorescent in situ hybridisation (FISH). Raman spectrometry was carried out to identify neo-mineral formation and selective extractions provided information on Hg distribution between the solid carrier phases. In column A microbial activity assessed by substrate consumption began after 15 days and induced a progressive decrease in the sulphate concentrations at the column outlet and the visual observation of black FeS precipitates (identified as partially oxidized makinawite). When sulphate reduction peaked after 120 days, iron was leached from the column as well as monomethylmercury (MMHg) and Hg. Bacterial diversity did not vary significantly either in time or space, sulphate reducing bacteria were observed with FISH and a sequenced DNA band bore resemblance to Desulfotomaculum reducens. In column B bacterial activity directly induced iron reduction (measured in the outlet as Fe(II)) as well as Hg leaching and MMHg formation. Shewanella sp. was observed with FISH. In both columns methylation potentials averaged 1% and selective extractions showed a shift of Hg from the ferrihydrite towards the organic matrix and newly formed FeS. These results contribute to understanding the interactions between bacteria and geochemical mechanisms controlling Hg fate and behaviour in saturated aquifers.
(28/07/2013)
BRGM, UNIGE, ISTerre, UJF, IFSTTAR, INSU - CNRS, USMB [Université de Savoie] [Université de Chambéry], CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Mercury concentrations in suspended particulate matter, water and mud-sediment un and downstream from old and recent gold mining sites in french Guiana
Although the use of mercury (Hg) for gold mining has been officially banned in French Guiana since 2006, there are still reasons to be wary of its occurrence in river water and its impact on local populations. In fact, gold-mining generates intense soil erosion and high turbidity in the rivers downstream from mining sites. This contributes to Hg pollution and dissemination both via the remobilization of Hg naturally present in the soils and the release of metallic Hg from the gold recovery process. In the affected rivers, Hg transport and speciation is mainly controlled by the suspended particulate matter (SPM) rather than remaining dissolved. The aim of this study is to understand and quantify the fate of this SPM-associated Hg along the Boulanger river affected by old and new gold mining activities. Furthermore we provide recent data (2012) essential to evaluate the efficiency of legal gold mining companies in restoring and re-planting exploited zones to control erosion, river turbidity and SPM transport. Inorganic Hg(II), monomethylmercury (MMHg) and turbidity measurements were measured in water, SPM and mud-sediment collected along the Boulanger River, from the spring down to its confluence with the Orapu River. The intensity of gold-mining in this area has been up and down through the last century and presents contrasting conditions with old and recently exploited areas. Dissolved Hg (HgD) levels were low (1-2 ng.L-1) and consistent with previous data known for the Amazonian area. Dissolved MMHg concentrations represented up to 8% of HgD which is higher than previous results (around 2%). Some relationships occurred between Hg concentrations in mud-sediment and turbidity values which both decreased downstream from the mining sites, then stabilized at 4-5 km further down. Hg contents in the mud-sediment show the impact of old (1.2 ng Hg.L-1) and new gold mining practices (~3 ng Hg.L-1). These concentrations were respectively 2 and 5 times higher than those near the river spring (0.61 ng.L-1). Moreover, Hg contents in sediment of artificial laguna (max measured 1.023 µg.g-1 Dry Matter) were up to 10 times the geochemical background of French Guiana sediment (0.1±0.05 µg.g-1) and did not show significant differences between old and new laguna. This suggests that Hg contents in mining-related particles released have not significantly changed for the so-called new mining. Accordingly, these results show that even though Hg use was banned from French Guiana 6 years ago, present gold mining practices still release significant amounts of Hg into the rivers. Survey intensification in French Guiana river systems should provide a more complete data set, essential to change gold mining practices and to reduce SPM and Hg contamination of the aquatic environment.
(28/07/2013)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Caractérisation et rôle respectif des apports organiques amont et locaux sur l'oxygénation des eaux de la Garonne estuarienne
L’estuaire de la Gironde est le plus grand estuaire macrotidal d’Europe formé par la confluence de la Garonne (où se situe l’agglomération de Bordeaux) et de la Dordogne. L’une de ses principales caractéristiques est la présence d’une zone à forte turbidité (bouchon vaseux) où les processus hétérotrophes (dégradation de la matière organique) sont favorisés et où au contraire les processus autotrophes (production primaire) sont limités par le manque de lumière. Ainsi, des déficits en oxygène pouvant être préjudiciables à la vie aquatique se développent systématiquement dans la zone du bouchon vaseux de la Garonne estuarienne. Ces préoccupations environnementales ont donc conduit à étudier en détail dans le cadre de ce travail de doctorat, les facteurs environnementaux qui provoquent ces hypoxies estuariennes. Dans un premier temps, j’ai réalisé un suivi sur le réseau d’eaux urbaines partiellement séparatif et unitaire de la Communauté Urbaine de Bordeaux, de ses stations d’épurations et déversoirs d’orage afin d’appréhender les apports urbains de matières organique et azotées et de les comparer à ceux en provenance du bassin versant amont. Bien que les deux stations d’épuration réalisent des abattements très significatifs sur la matière organique et l’ammonium, il s’avère que les flux vers le milieu naturel restent importants, notamment durant les périodes estivales, pendant lesquelles des orages peuvent engendrer des déversements d’effluents non traités. Ensuite, des expériences d’incubations ont permis de mettre en évidence le caractère fortement labile de cette matière organique urbaine. Le carbone organique dissous et l’ammonium, contenus dans les eaux usées, sont des composés fortement consommateurs en oxygène. Des expériences de respirométrie ont également permis d’estimer les taux de consommation en oxygène nettement plus importants dans les effluents urbains que dans les eaux de la Gironde. Enfin, l’analyse des données du réseau de mesures en continu de la qualité physico-chimique des eaux MAGEST (MArel Gironde ESTuaire) a démontré que l’estuaire subit dans sa section garonnaise des périodes d’hypoxie lors d’étiages prononcés, la masse d’eau la plus affectée par ces désoxygénations étant celle qui oscille aux alentours de l’agglomération de Bordeaux. Si ces résultats démontrent l’impact significatif de l’agglomération Bordelaise, le traitement statistique des données MAGEST pour la période 2005-2011 montre que les phénomènes de désoxygénation sont accrus en période d’étiage prononcé, en présence du bouchon vaseux et lorsque la température de l’eau est élevée. Dans ces conditions, l’oxygène dissous, déjà présent en faible quantité, peut être rapidement consommé lors d’apports supplémentaires d’eaux urbaines non traitées qui ont lieu pendant de fortes précipitations orageuses. Ce travail démontre également que le type de traitement biologique des eaux usées employé par les stations d’épuration et les capacités de stockage temporaire d’eaux d’orages ont un rôle critique sur les bilans de ces composés rejetés dans le milieu naturel. Enfin, ce travail permet de proposer aux gestionnaires des stratégies de rejets des effluents à court et moyen terme, en fonction des conditions hydrologiques et physico-chimiques du milieu, dans le but de limiter leur impact sur l’oxygénation des eaux estuariennes de la Garonne.
(16/07/2013)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Environmental factors contributing to the development of brown muscle disease and perkinsosis in Manila clams (Ruditapes philippinarum) and trematodiasis in cockles (Cerastoderma edule) of Arcachon Bay
The aim of the present study was to identify environmental factors that could explain the distribution of different pathologies of commercially exploited intertidal bivalves in an Atlantic lagoon, Arcachon Bay. In particular, the role of the salinity gradient as a driver was explored. The Manila clam Ruditapes philippinarum experienced two severe pathologies, perkinsosis, which is due to a protozoan parasite, and brown muscle disease (BMD), the etiological agent of which remains unknown. Perkinsus olseni infection was very low in a small low-salinity area but, at the scale of the entire lagoon, was more influenced by organic matter content in the sediment and by emersion time. BMD prevalence was also 2.6 times higher in the higher organic content area but was also negatively correlated with salinity. The sympatric cockle (Cerastoderma edule) was affected by eight trematode species. These parasites have a complex life cycle that generally involves three free-living host species. The distribution of the different trematode communities was rather patchy within Arcachon Bay with no clear relationship with measured environmental factors. The dominance of particular trematode species could be due to the presence of other hosts involved in their life cycle, making it more difficult to detect a major environmental driver. This survey demonstrated that salinity is not a major factor explaining disease distribution in this temperate lagoon. This result has consequences for the research of 'refuge areas' (free of diseases) or 'hot spots' (heavy infection) for species of high economic value.
(Marine Ecology. vol. 35, n° 0173-9565, pp. 67-77, 08/07/2013)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Holocene climate variations in the western Antarctic Peninsula: evidence for sea ice extent predominantly controlled by changes in insolation and ENSO variability
The West Antarctic ice sheet is particularly sensitive to global warming and its evolution and impact on global climate over the next few decades remains difficult to predict. In this context, investigating past sea ice conditions around Antarctica is of primary importance. Here, we document changes in sea ice presence, upper water column temperatures (0-200 m) and primary productivity over the last 9000 yr BP (before present) in the western Antarctic Peninsula (WAP) margin from a sedimentary core collected in the Palmer Deep Basin. Employing a multi-proxy approach, based on the combination of two biomarkers proxies (highly branched isoprenoid (HBI) alkenes for sea ice and TEX86L for temperature) and micropaleontological data (diatom assemblages), we derived new Holocene records of sea ice conditions and upper water column temperatures. The early Holocene (9000-7000 yr BP) was characterized by a cooling phase with a short sea ice season. During the mid-Holocene (~7000-3800 yr BP), local climate evolved towards slightly colder conditions and a prominent extension of the sea ice season occurred, promoting a favorable environment for intensive diatom growth. The late Holocene (the last ~2100 yr) was characterized by warmer temperatures and increased sea ice presence, accompanied by reduced local primary productivity, likely in response to a shorter growing season compared to the early or mid-Holocene. The gradual increase in annual sea ice duration over the last 7000 yr might have been influenced by decreasing mean annual and spring insolation, despite increasing summer insolation. We postulate that, in addition to precessional changes in insolation, seasonal variability, via changes in the strength of the circumpolar Westerlies and upwelling activity, was further amplified by the increasing frequency/amplitude of the El Niño-Southern Oscillation (ENSO). However, between 3800 and 2100 yr BP, the lack of correlation between ENSO and climate variability in the WAP suggests that other climatic factors might have been more important in controlling WAP climate at this time.
(Climate of the Past. vol. 9, n° 1814-9324, pp. 1431-1446, 01/07/2013)
LOCEAN, IPSL, ENS-PSL, PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, IP Paris, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, NIOZ, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Innovative 4G mobile phone LDS antenna module using plastronics integration scheme
(pp. 2217-2218, 01/07/2013)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS