Quantitative assessments of moisture sources and temperature governing rainfall δ18O from 20 years' monitoring records in SW-France: Importance for isotopic-based climate reconstructions
(Journal of Hydrology. vol. 591, n° 0022-1694, pp. 125327, 01/12/2020)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, I2M-BX, UB, CNRS, INRAE, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GLACCIOS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GEOTRAC, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
An Invasive Mussel (Arcuatula senhousia, Benson 1842) Interacts with Resident Biota in Controlling Benthic Ecosystem Functioning
The invasive mussel Arcuatula senhousia has successfully colonized shallow soft sediments worldwide. This filter feeding mussel modifies sedimentary habitats while forming dense populations and efficiently contributes to nutrient cycling. In the present study, the density of A. senhousia was manipulated in intact sediment cores taken within an intertidal Zostera noltei seagrass meadow in Arcachon Bay (French Atlantic coast), where the species currently occurs at levels corresponding to an early invasion stage. It aimed at testing the effects of a future invasion on (1) bioturbation (bioirrigation and sediment mixing) as well as on (2) total benthic solute fluxes across the sediment-water interface. Results showed that increasing densities of A. senhousia clearly enhanced phosphate and ammonium effluxes, but conversely did not significantly affect community bioturbation rates, highlighting the ability of A. senhousia to control nutrient cycling through strong excretion rates with potential important consequences for nutrient cycling and benthic-pelagic coupling at a broader scale. However, it appears that the variability in the different measured solute fluxes were underpinned by different interactions between the manipulated density of A. senhousia and several faunal and/or environmental drivers, therefore underlining the complexity of anticipating the effects of an invasion process on ecosystem functioning within a realistic context.
(Journal of Marine Science and Engineering. vol. 8, n° 2077-1312, pp. 963, 26/11/2020)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Label free imaging with harmonic generation microscopy and endogeneous fluorescence investigations for food, ecotoxicology and health issues
(24/11/2020)
PAnTher, ONIRIS, INRAE, APEX, PAnTher, ONIRIS, INRAE, ONIRIS, GEPEA-MAPS2, GEPEA, IUT Nantes, UN, UN UFR ST, UN, IUT Saint-Nazaire, UN, EPUN, UN, ONIRIS, CNRS, UBL, IMT Atlantique, IMT, IUT La Roche-sur-Yon, UN, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
16 years of topographic surveys of rip-channelled high-energy meso-macrotidal sandy beach
Sandy beaches are highly dynamic environments buffering shores from storm waves and providing outstanding recreational services. Long-term beach monitoring programs are critical to test and improve shoreline, beach morphodynamics and storm impact models. However, these programs are relatively rare and mostly restricted to microtidal alongshore-uniform beaches. The present 16year dataset contains 326 digital elevation models and their over 1.635 × 10 6 individual sand level measurements at the high-energy meso-macrotidal rip-channelled Truc Vert beach, southwest France. Monthly to bimonthly topographic surveys, which coverage progressively extended from 300 m to over 2000 m to describe the alongshore-variable changes, are completed by daily topographic surveys acquired during a 5-week field campaign. The dataset captures daily beach response at the scale of a storm to three large cycles of interannual variability, through the impact of the most energetic winter since at least 75 years and prominent seasonal erosion/recovery cycles. The data set is supplemented with high-frequency time series of offshore wave and astronomical tide data to facilitate its future use in beach research.
(Scientific Data. vol. 7, n° 2052-4463, 20/11/2020)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Caractérisation des variations climatiques du dernier millénaire à l'aide de nouvelles méthodes statistiques : reconstructions paléoclimatiques et intégration dans un modèle de circulation globale du climat
La variabilité climatique joue un rôle considérable dans de nombreux domaines de nos vies. L’augmentation globale des températures, forcée par les émissions croissantes de gaz à effet de serre d’origine anthropique, a connu une période de hiatus entre 1998 et 2012. Les causes de cette séquence font l’objet de controverses scientifiques concernant les rôles relatifs de la variabilité intrinsèque au système climatique, et des forçages externes. Afin de résoudre ce type de débat, il est nécessaire de mieux comprendre les modes de variabilité décennaux, issus de l’organisation à grande échelle du système climatique. Cependant, 150 années d’observations instrumentales ne permettent pas d’estimer de manière rigoureuse leurs caractéristiques et donc de comprendre leur dynamique.Cette thèse cherche à parfaire la compréhension de la variabilité climatique multi-décennale en produisant des reconstructions sur le dernier millénaire d’indices ou de grilles climatiques. Pour cela, on se propose d’introduire des méthodes statistiques modernes, dites de machine learning, appliquées à des données paléoclimatiques issues d’archives naturelles (cernes d’arbres, carottes de glace..). La base de données PAGES 2K récemment développée propose plus de 700 enregistrements sur le dernier millénaire et sera abondamment utilisée pour construire les modèles statistiques proposés.Des métriques mathématiques objectives permettent de montrer que l’application d’une méthode non-linéaire telle que la forêt aléatoire produit en général des résultats plus robustes que les méthodes linéaires usuelles. On utilise donc la forêt aléatoire pour reconstruire des variations du mode principal des températures de surface océanique (SST) de l’Atlantique Nord, l’Atlantic Multidecadal Variability (AMV), notamment liée à la circulation océanique de retournement dans ce bassin (AMOC). Cette reconstruction suggère que des changements dans cette circulation, survenus à la fin du XIIe siècle, furent probablement le catalyseur d’une entrée précoce dans le petit âge de glace, une période relativement froide du dernier millénaire. Les importantes activités volcaniques des XIIIe, XVe et XIXe siècles sont cependant identifiées comme les causes principales de la prolongation du petit âge de glace dont le paroxysme se situe au XIXe siècle. De plus, des changements récents dans la variabilité de l’AMV semblent, d’après la théorie des systèmes dynamiques, être un signal d’approche d’un point de bascule de l’AMOC.Une reconstruction des SST sur une grille a également été produite par forêt aléatoire sur tout le millénaire. Cette reconstruction montre que les phases positives de l’AMV auraient tendance à conduire, environ une décennie après, à une phase négative du mode principal des SST du Pacifique, l’Interdecadal Pacific Variability (IPV). Comme les observations montrent que le hiatus de 1998-2012 correspond à une phase négative de l’IPV, ces résultats soutiennent l’hypothèse que l’AMV est l’un des moteurs principaux de telles périodes de hiatus. Dans la lignée des hypothèses de ralentissement de l’AMOC déduites du spectre de l’AMV reconstruite, cette grille suggère que celle-ci atteint aujourd‘hui un niveau bas sans précédent, depuis au moins l’an 850.Enfin, cette même grille de reconstruction a été assimilée par méthode de rappel en SST au sein du modèle de circulation globale IPSL-CM5A2-LR. Bien que la simulation reproduit convenablement les températures et paléo-températures mesurées, la méthode de rappel semble moins efficace que des méthodes d’assimilation plus complexes tel que le filtre de Kalman. De plus, l’AMOC simulée dans cette réanalyse ne correspond pas à son estimation à partir de méthodes statistiques, sans doute du fait que la salinité, est déterminante pour forcer la convection océanique et l’AMOC. Ainsi, assimiler la salinité semble nécessaire pour reproduire correctement les variations d’AMOC sur le dernier millénaire à l’aide d’un modèle.
(13/11/2020)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Impact of Old and Recent Gold Mining Sites on Mercury Fluxes in Suspended Particulate Matter, Water and Sediment in French Guiana
In 2006 the use of mercury (Hg) was banned for gold mining in French Guiana. However, mining of old placers could mobilize Hg accumulated in soils and sediment. This study aimed to measure the current impact of a mining concession (Boulanger site) on the Hg load in the watershed. Turbidity, Total Mercury (THg), and Monomethylmercury (MMHg) were measured in water, suspended particulate matter (SPM), river sediment and sediments from old tailing ponds along a river section of 30 km up and downstream from a mining concession in French Guiana during a dry and a rainy season. Total dissolved Hg (THg D) concentrations varied little from up-to downstream but were all higher (fourfold on average) during the rainy season (3.2 to 4.4 ng L −1), than during the dry season and consistent with previous data known for the Amazonian area. Dissolved MMHg (MMHg D) represented up to 30% of THg D during the dry season, which is higher than previous results (typically around 2%). Mercury concentrations in sediments were highest in the vicinity of areas affected by old (before 2006) rather than new gold mining practices. Even though Hg was banned in 2006, present gold mining practices still release natural Hg and Hg inherited from older mining practices into the watershed.
(Applied Sciences. vol. 10, n° 2076-3417, pp. 7829, 04/11/2020)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Revision of the French Polycirridae (Annelida, Terebelliformia), with descriptions of eight new species
Polycirridae from French waters are revised based on material available in French marine stations and newly collected specimens. This work is the third part of the Spaghetti Project aiming to revise French species of "Spaghetti" terebellid worms. It describes eight new species using both morphological (for all species) and molecular (for some species) tools: Amaeana gremarei n. sp., Polycirrus catalanensis n. sp., P glasbyi n. sp., P gujanensis n. sp., P idex n. sp., P. nogueirai n. sp., P. pennarbedae n. sp. and P readi n. sp., in addition to a previously described species. An identification key for European species of Polycirridae is also provided.
(Zootaxa. vol. 4869, n° 1175-5326, pp. 151-186, 02/11/2020)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UMS POREA, INSU - CNRS, CNRS, INRAE
Assessing the potential risk and relationship between microplastics and phthalates in surface seawater of a heavily human-impacted metropolitan bay in northern China
The impacts of microplastics (MPs) and phthalates (PAEs), a class of MP-associated contaminants, on the marine environment are not thoroughly understood despite concern over their adverse effects on humans and ecosystems. Field studies linking MPs and PAEs in seawater have not yet been reported. We investigate for the first time the correlation between MPs contamination and the presence of PAEs in the surface seawater of Jiaozhou Bay (JZB), a semi-enclosed metropolitan bay in northern China heavily impacted by human activity. The abundance of MPs, dominated by polyethylene and polyethylene terephthalate mostly smaller than 2 mm, ranged between 24.44 items/m3 and 180.23 items/m3, with the majority being black and transparent fibers and fragments. Concentrations of PAEs varied from 129.96 ng/L to 921.22 ng/L. Relatively higher abundances of MPs and higher concentrations of PAEs were generally found in areas near riverine inputs and sewage treatment plants. There was a strong correlation between PAEs concentration and MPs abundance, suggesting that they are closely linked. In a risk assessment combining PAEs and MPs, the risk quotients (RQs) indicated that the ecological risk of di-n-butyl phthalate in JZB was relatively high (0.046 (Ecotoxicology and Environmental Safety. vol. 204, n° 0147-6513, pp. 111067, 01/11/2020) EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Frequency of exceptional Nile flood events as an indicator of Holocene hydro-climatic changes in the Ethiopian Highlands
Climate conditions in Africa have varied substantially during the Late Quaternary with alternating humid and arid periods controlled mainly by the African monsoonal regime. However, the duration and termination of the last African Humid Period (14–6 ka BP) and its internal climatic variability are still debated. Using a laminated sequence from the Nile Deep-Sea Fan, we reconstruct for the first time the monsoon-induced frequency of exceptional Nile floods at centennial resolution during the African Humid Period. By combining sedimentological, geochemical and microscopic tools and comparing our record with two proximal piston cores and with regional paleoclimatic records, we show: a) the occurrence of recurrent high-energy floods between 10.1 and 9 ka BP, during the height of the African Humid Period; b) a shift in the hydro-climatic regime as early as 9 ka BP, with a progressive reduction in flood frequency and magnitude until 8.2 ka BP, likely related to a southward migration of the monsoon rainfall belt; c) a drastic reduction of flood activity between 8.2 and 7.8 ka BP; d) an unstable Ethiopian-Nile hydrological system from 7.8 ka BP, followed by a further decrease in river runoff until ∼4 ka BP. The occurrence of a stepwise hydro-climatic deterioration over the Ethiopian Highlands from ∼9 ka BP brings into question the climatic linkages and feedbacks between low and high latitudes during the Early to Mid-Holocene and in particular around the 8.2 ka BP North Atlantic cooling event. Our unique record of flood frequency at centennial-resolution therefore allows us to draw new insights on fluvial and geomorphic feedbacks of the Nile hydrologic system to monsoonal regimes during a period of major environmental shifts.
(Quaternary Science Reviews. vol. 247, n° 0277-3791, pp. 106543, 01/11/2020)
GEOAZUR 7329, INSU - CNRS, UniCA, CNRS, IRD [Occitanie], UniCA, INSU - CNRS, UM, CNRS, UA, EDYTEM, USMB [Université de Savoie] [Université de Chambéry], CNRS, Fédération OSUG, CEPAM, UNS, CNRS, UniCA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Metal pollution trajectories and mixture risk assessed by combining dated cores and subsurface sediments along a major European river (Rhône River, France)
In European rivers, research and monitoring programmes have targeted metal pollution from bed and floodplain sediments since the mid-20th century by using various sampling and analysis protocols. We propose to characterise metal contamination trajectories since the 1960s based on the joint use of a large amount of data from dated cores and subsurface sediments along the Rhône River (ca. 512 km, Switzerland–France). For the reconstruction of spatio-temporal trends, enrichment factors (EF) and geo-accumulation (Igeo) approaches were compared. The latter index was preferred due to the recurrent lack of grain-size and lithogenic elements in the dataset. Local geochemical backgrounds were established near (1) the Subalps and (2) the Massif Central to consider the geological variability of the watershed. A high contamination (Igeo = 3–5) was found for Cd, Cu and Zn from upstream to downstream over the period 1980–2000. This pattern is consistent with long-term emissions from major cities and the nearby industrial areas of the Upper Rhône (Geneva, Arve Valley), and Middle Rhône (Lyon, Chemical Corridor, Gier Valley). Hotspots due to Cu and Zn leaching from vineyards, mining, and highway runoff were also identified, while Pb was especially driven by industrial sources. The recovery time of pollution in sediment varied according to the metals and was shorter upstream of Lyon (15–20 years) than downstream (30–40 years). More widely, it was faster on the Rhône than along other European rivers (e.g. Seine and Rhine). Finally, the ecotoxicological mixture risk of metal with Persistent Organic Pollutants (POPs) for sediment-dwelling organisms showed a medium “cocktail risk” dominated by metals upstream of Lyon, although it is enhanced due to POPs downstream, and southward to the delta and the Mediterranean Sea. Overall, this study demonstrates the heterogeneity of the contamination trends along large fluvial corridors such as the Rhône River.
(Environment International. vol. 144, n° 0160-4120, pp. 106032, 01/11/2020)
LEHNA IAPHY, LEHNA, UCBL, ENTPE, CNRS, LEHNA, UCBL, ENTPE, CNRS, RiverLy, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, EVS, ENS de Lyon, Mines Saint-Étienne MSE, IMT, UL2, UJML, INSA Lyon, INSA, UJM, ENTPE, ENSAL, CNRS, ALLHiS, UJM