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
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
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
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
Use of passive samplers (POCIS and SPMD) for chemical and biological monitoring of wastewater advanced treatments
One of the main objective of the ECHIBIOTEB program (Innovating tools for sampling, chemical and biological analyses for the diagnostic of wastewater advanced treatments and sludge treatments, 2011-2014, financed by the French National Research Agency, coordinated by Irstea) is to study some advanced processes such as ozonation (O3) or Granular Activated Carbon (GAC) as example used to treat wastewaters in tertiary stage of wastewater treatment plants (WWTP). The challenges when studying such processes is first to be able to measure organic micropollutants at very low concentrations (sub ng/L level) and second to link the occurrence of contaminants to adverse biological effects. To achieve these goals, 2 strategies were combined: i) targeted chemical analyses on passive sampler (PS) extracts vs. water grab samples, and ii) biological analyses on the same PS extracts and water grab samples. Targeted chemical analyses were performed on POCIS (Polar Organic Chemical Integrative Sampler) extracts for 119 hydrophilic compounds belonging to pharmaceutical, hormone, pesticide and alkylphenol classes and on SPMD (Semi-Permeable Membrane Device) extracts for 46 lipophilic compounds belonging to chlorine pesticides, PAH (Polycyclic Aromatic Hydrocarbon), PCB (PolyChloroBiphenyl), PBDE (PolyBrominated DiphenylEthers) classes. PS extracts were also tested with in vitro bioassays using cell lines with different reporter genes or in order to evaluate oestrogenic and androgenic activities, HAP-like and dioxin-like disruptions and geno- and cytotoxicity. Two one-month-long sampling campaigns were carried out in a same WWTP (Normandie, France) using activated sludge and sand filter as secondary treatment. In the first one, conducted from September 20th to October 18th 2011, ozonation followed by GAC were studied as tertiary treatment. In the second one, from March 13th to April 10th 2012, we focused on ozonation process only. In both campaigns, POCIS were exposed in water during 14 days and SPMD during 28 days. In order to be able to compare these 2 campaigns and the molecule concentrations upstream and downstream the tertiary treatment, POCIS and SPMD were always immersed in an aquarium in the same controlled experimental conditions of flow (280 mL/min), temperature (20° C) and light. To insure quality of data, POCIS and SPMD were exposed in triplicate and field blanks were realized (i.e. PS exposed to the ambient air). In parallel, 2h composite water samples were collected at D0, D14 and D28. The average sampling time of 2h is reliable considering the water residence time in the secondary treatment. As examples of results concerning the use of POCIS to characterize the O3 + GAC process: By comparing the cumulated concentrations in POCIS, the O3 + GAC process was shown efficient to eliminate some organic micropollutants. Indeed, -blockers and more generally pharmaceuticals were very well removed with a concentration in the effluent a thousand times smaller than in the influent. The conclusions were the same with grab sampling. Moreover, the contamination profiles (or fingerprint) were compared between PS and grab sampling. As example, in case of -blockers they are equivalent. We have also compared the time weighted average concentration obtained with POCIS, with water concentrations from grab sampling. POCIS sampling also allowed to decrease limits of detection in tertiary effluent for some molecules. Indeed, 7 compounds were detected in POCIS extracts and not in grab water samples. As example atenolol, sotalol, propranolol, metoprolol, nordiazepam, amitryptilline and alprazolam were detected in POCIS extracts downstream the tertiary treatment and clenbuterol, gemfibrozil, imipramine and doxepine were detected in POCIS extracts upstream the process. As a consequence, POCIS appeared as an interesting tool to characterize tertiary stages of WWTPs with analysis of organic micropollutants at very low concentrations, near the ng/L range. From the biological point of view, oestrogenic, anti-androgenic as well as HAP-like and dioxin-like disruptions were observed in POCIS exposed before the O3 + GAC process. No more biological activity was detected in these POCIS exposed after the process. These biological results matched with the decrease of contaminant concentrations up and downstream the process. Both chemical and biological analyses were in accordance and revealed a good efficiency of the O3 + GAC advance treatment process.
(pp. 1, 27/06/2013)
UR MALY, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, INERIS, ESE, UP11, CNRS
Les petits pélagiques dans l'estuaire de la Gironde : 30 ans de suivi d'abondance face à 30 ans de changements globaux
Les conséquences écologiques du changement global (changement climatique + pressions anthropiques) ont été montrées pour les communautés écologiques de l'estuaire de la Gironde dans plusieurs études récentes. La marinisation et le réchauffement de l'eau, principaux effets, entrainent de profondes modifications dans la structure et la dynamique des communautés ichtyologiques. Cependant, ces récentes études sur les poissons notamment, n'ont pas explicitement montré le lien entre les facteurs environnementaux et les réponses des communautés. Objectifs : caractériser explicitement les modifications de structure et de dynamique temporelle des poissons pélagiques et le lien avec les facteurs environnementaux.
(pp. 1, 19/06/2013)
UR EPBX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Removal efficiency of micropollutants from mass balances in sludge biological and thermal treatment facilities
Removal efficiency of micropollutants from mass balances in sludge biological and thermal treatment facilities.
(pp. 1, 16/06/2013)
UR MALY, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS