Dynamics of particulate organic matter composition in coastal systems: a spatio-temporal study at multi-systems scale
In coastal systems, the multiplicity of sources fueling the pool of particulate organic matter (POM) leads to divergent estimations of POM composition. Eleven systems (two littoral systems, eight embayments and semi-enclosed systems and one estuary) distributed along the three maritime façades of France were studied for two to eight years in order to quantify the relative contribution of organic matter sources to the surface-water POM pool in coastal systems. This study was based on carbon and nitrogen elemental and isotopic ratios, used for running mixing models. The POM of the estuary is dominated by terrestrial material (93% on average), whereas the POM of the other systems is dominated by phytoplankton (84% on average). Nevertheless, for the latter systems, the POM composition varies in space, with 1) systems where POM is highly composed of phytoplankton (≥ 93%), 2) systems characterized by a non-negligible contribution of benthic (8 to 19%) and/or riverine (7 to 19%) sources, and 3) the Mediterranean systems characterized by the contribution of diazotroph organisms (ca. 14%). A continent-to-ocean gradient of riverine and/or benthic POM contribution is observed. Finally, time series reveal 1) seasonal variations of POM composition, 2) differences in seasonality between systems, and 3) an inshore-offshore gradient of seasonality within each system that were sampled at several stations. Spatial and seasonal patterns of POM composition are mainly due to local to regional processes such as hydrodynamics and sedimentary hydrodynamic (e.g. resuspension processes, changes in river flows, wind patterns influencing along-shore currents) but also due to the geomorphology of the systems (depth of the water column, distance to the shore). Future studies investigating the link between these forcings and POM composition would help to better understand the dynamics of POM composition in coastal systems.
(Progress in Oceanography. vol. 156, n° 0079-6611, pp. 221-239, 01/08/2017)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CHIM, AD2M, SU, CNRS, SBR, SU, CNRS, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], ULCO, LOMIC, INSU - CNRS, SU, CNRS, OOB, SU, CNRS, CRESCO, MNHN, IFREMER, BOREA, UNICAEN, NU, MNHN, IRD, SU, CNRS, UA, CEFREM, UPVD, INSU - CNRS, CNRS, LIENSs, INSU - CNRS, ULR, CNRS, LEMAR, IRD, IFREMER, UBO EPE, CNRS, LOV, OOVM, UPMC, INSU - CNRS, CNRS, UPMC, INSU - CNRS, CNRS, MIO, IRD, AMU, INSU - CNRS, UTLN, CNRS, EFEB, AD2M, SU, CNRS, SBR, SU, CNRS, CRESCO, MNHN, IFREMER, MNHN, SBR, SU, CNRS, FR2424, SBR, SU, CNRS, IUEM, IRD, INSU - CNRS, UBO EPE, CNRS, OASU, UB, INSU - CNRS, ULR, CNRS, INRAE, CREC, UNICAEN, NU, AD2M, SU, CNRS, SBR, SU, CNRS
Additional records of Elasmopus vachoni Mateus & Mateus, 1966 (Crustacea: Amphipoda: Maeridae) from European waters (Tarifa, southern Spain)
Additional records of Elasmopus vachoni Mateus and Mateus, 1966 together with description of its its poorly-known mouthparts is provided, based on material from Tarifa Island (southern Spain). The known geographical distribution of this species extends from the Gulf of Guinea to the northern part of the Iberian Peninsula, all along its Atlantic and Mediterranean coast, also extending to Canary and Azores Archipelagos. Additionally, an identification key of Elasmopus species mentioned in European waters (ERMS area) is also given.
(Zootaxa. vol. 4299, n° 1175-5326, pp. 561, 31/07/2017)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Video monitoring of sandbar-shoreline response to an offshore submerged structure at a microtidal beach
In early 2013, an 800-m long and 12-m wide submerged breakwater with its crest in 2-m depth was implemented at the wave-dominated barred beach of Sète, SE France, to fight against erosion and submersion hazards. Daily video images from April 2011 to April 2016 covering an alongshore distance of 3.5 km are used to analyse the response of both the sandbar(s) and the shoreline to the structure implementation. Results show that the breakwater had a profound impact on the nearshore system, both shoreward of the structure and well away from it alongshore. A progressive rotation and linearisation of the sandbar was observed shoreward of the submerged breakwater. This resulted in the splitting of the sandbar adjacent to the structure during a net offshore sandbar migration event driven by a severe storm in December 2013. The typical formation of a salient or tombolo was not observed. Instead, shoreline coupled to the sandbar geometry, which resulted in a slight seaward migration of the shoreline in front of the structure. Overall, this study highlights that the role of the sandbar is critical to shoreline response to the implementation of breakwaters on barred beaches.
(Geomorphology. vol. 295, n° 0169-555X, pp. 297-305, 20/07/2017)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Evidence for the Trophic Transfer of Perfluoroalkylated Substances in a Temperate Macrotidal Estuary
The present survey examines the trophodynamics of a suite of 19 perfluoroalkyl substances (PFASs) in a temperate macrotidal estuary (Gironde, SW France). Across the 147 biota samples (18 taxa) collected, perfluorooctane sulfonate (PFOS), perfluorooctane sulfonamide (FOSA), and C8−C14 perfluoroalkyl carboxylates (PFCAs) were the mostrecurrent analytes. ΣPFASs ranged between 0.66−45 ng per g of wet weight of the whole body. Benthic organisms had relatively high ΣPFASs compared to demersal organisms and displayed specific composition profiles with higher relative abundances of C8 and C9 PFCAs. Trophic magnification factors (TMFs) were determined through the use of linear mixed effect models including censored data, thereby considering data below detection limits as well as the interspecific variability of δ15N and PFAS levels (random effects). TMFs were almost consistently >1 in the benthic food web as well as when considering all data pooled together, providing evidence for the biomagnification of several PFASs in estuarine environments. In addition, in contrast with previous observations, TMFs determined in the estuarine benthic web were found to significantly decrease with increasing chain length for C8−C14 PFCAs and C6−C8 perfluoroalkyl sulfonates. This suggests that PFAS chemical structure might not be necessarily predictive of TMFs, which are also influenced by the trophic web characteristics.
(Environmental Science and Technology. vol. 51, n° 0013-936X, pp. 8450-8459, 13/07/2017)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LPTC, UB, CNRS, IRSTEA, UR EABX, IRSTEA
Biomonitoring of fluoroalkylated substances in Antarctica seabird plasma: Development and validation of a fast and rugged method using on-line concentration liquid chromatography tandem mass spectrometry
We report on a fast, accurate and rugged analytical procedure to determine a wide span of perfluoroalkyl and polyfluoroalkyl substances (PFASs) in seabird plasma. The 26 investigated compounds included perfluoroalkyl carboxylates (C5–C14 PFCAs), perfluoroalkyl sulfonates (C4, C6, C7, C8, C10 PFSAs), perfluorooctane sulfonamide (FOSA) and N-alkyl derivatives (MeFOSA, EtFOSA), N-alkyl perfluorooctane sulfonamido acetic acids (MeFOSAA, EtFOSAA), fluorotelomer sulfonates (4:2 FTSA, 6:2 FTSA, 8:2 FTSA), polyfluoroalkyl phosphate diesters (diPAPs) and perfluorooctane sulfonamide phosphate diester (diSAmPAP). The method described herein requires a reduced sample amount (25 μL) and involves rapid and simple sample preparation (protein precipitation with acetonitrile but without acidification) prior to analysis by on-line solid phase extraction (Oasis HLB sorbent) coupled to high performance liquid chromatography negative electrospray ionization tandem mass spectrometry. The optimization was conducted using experimental designs to account for potential interactions between variables. Out of the 26 target analytes, 23 compounds showed excellent accuracy (± 25% of the expected values). Intermediate precision and matrix effects remained acceptable for most analytes thanks to efficient internal standardization. A human serum standard reference material (NIST SRM 1957) was included in the validation scheme to evaluate method trueness, which proved satisfactory (│Z-scores│<2 for most compounds). Notwithstanding the small initial sample intake, limits of detection as low as 0.003–0.1 ng g⁻¹ plasma were obtained. This allowed the determination of 11 target PFASs in Antarctic seabird plasma samples. ΣPFASs in Antarctic seabird plasma ranged from 0.37 to 19 ng g⁻¹, with a predominance of PFOS (>54% of ΣPFASs on average). The reduced plasma amount required implies that the present method could also be applied to the analysis of PFASs in the plasma of smaller biological models
(Journal of Chromatography A. vol. 1513, n° 0021-9673, pp. 107-117, 07/07/2017)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CEBC, INRA, ULR, CNRS
Développement du thermomètre Δ47 appliqué sur coccolithes : de la calibration en laboratoire à l’applicabilité au registre sédimentaire
Le géothermomètre Δ47 est basé sur la relation entre l’abondance des liaisons 13C–18O des carbonates et la température de calcification. Ce proxy contourne potentiellement les limites des autres thermomètres (δ18O, Mg/Ca) pour reconstruire les paléo-températures des océans, expliquant son développement exponentiel depuis dix ans. Cette thèse teste pour la première fois le potentiel et les limites de la thermométrie Δ47 sur les coccolithes, des nannofossiles calcaires produits par des organismes calcifiants dans la zone photique. Ces biominéraux calcitiques et ubiquistes constituent une part importante de l’archive sédimentaire. Des cultures in vitro nous ont permis d’établir que trois espèces de coccolithes actuelles enregistrent la même relation Δ47 – T que la calcite inorganique, alors qu'elles présentent de très larges effets vitaux en δ18O (±5‰). Nous concluons que ces espèces de coccolithes d'importance géologique ne présentent pas d’effets vitaux en Δ47. Nous avons ensuite appliqué le Δ47 à l’étude des sédiments enregistrant l’événement d’anoxie océanique du Toarcien (–183 Ma) au cours duquel les reconstructions de températures restent encore ambigües, notamment du fait de la méconnaissance de la composition isotopique en oxygène de l’eau de mer. Sur la base des données Δ47 acquises, nous proposons des températures élevées (de l’ordre de 36°C), mais restant relativement stables sur l'intervalle d'étude. En couplant ces températures aux données de δ18O des carbonates, nous suggérons une variation importante du δ18O de l'eau de mer dans le Bassin de Paris lors de la mise en place des faciès black shales. Enfin, sur des sédiments pélagiques subactuels, l’une des espèces étudiées présente des déséquilibres isotopiques en Δ47 non observés en culture et explicables par d’autres paramètres environnementaux comme l’intensité lumineuse. Cette thèse illustre le potentiel du thermomètre Δ47 des coccolithes en différents contextes, ouvrant un vaste champ d’application de reconstruction des paléo-environnements sur le Méso-Cénozoïque
(05/07/2017)
IPGP, INSU - CNRS, UPD7, UR, IPG Paris, CNRS
Trojan Horse Strategy for Non-invasive Interference of Clock Gene in the Oyster Crassostrea gigas
RNA interference is a powerful method to inhibit specific gene expression. Recently, silencing target genes by feeding has been successfully carried out in nematodes, insects, and small aquatic organisms. A non-invasive feeding-based RNA interference is reported here for the first time in a mollusk bivalve, the pacific oyster Crassostrea gigas. In this Trojan horse strategy, the unicellular alga Heterocapsa triquetra is the food supply used as a vector to feed oysters with Escherichia coli strain HT115 engineered to express the double-stranded RNA targeting gene. To test the efficacy of the method, the Clock gene, a central gene of the circadian clock, was targeted for knockout. Results demonstrated specific and systemic efficiency of the Trojan horse strategy in reducing Clock mRNA abundance. Consequences of Clock disruption were observed in Clock-related genes (Bmal, Tim1, Per, Cry1, Cry2, Rev.-erb, and Ror) and triploid oysters were more sensitive than diploid to the interference. This non-invasive approach shows an involvement of the circadian clock in oyster bioaccumulation of toxins produced by the harmful alga Alexandrium minutum.
(Marine Biotechnology. vol. 19, n° 1436-2228, pp. 361-371, 03/07/2017)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Abrupt Northward Shift of SPCZ position in the late-1920s Indicates Coordinated Atlantic and Pacific ITCZ Change
(Past Global Changes Magazine. vol. 25, n° 2411-605X, pp. 52-56, 01/07/2017)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Causes of dust size variability in central East Antarctica (Dome B): Atmospheric transport from expanded South American sources during Marine Isotope Stage 2
Marine isotope stage 2 Micron-size particle Raman mineralogy a b s t r a c t We here investigate the spatial and temporal variability of eolian dust particle sorting recorded in the Dome B (77 05 0 S, 94 55' E) ice core, central East Antarctica, during Marine Isotope Stage (MIS) 2. We address the question whether such changes reflect variable transport pathways from a unique source area or rather a variable apportionment from diverse Southern Hemisphere sources transported at different elevation in the troposphere. The Sr-Nd radiogenic isotope composition of glacial dust samples as well as single-particle Raman mineralogy support the hypothesis of a single dust provenance both for coarse and fine mode dust events at Dome B. The southern South American provenance of glacial dust in Antarctica deduced from these results indicate a dust composition coherent with a mixture of volcanic material and minerals derived from metamorphic and plutonic rocks. Additionally, Dome B glacial samples contain aragonite particles along with diatom valves of marine benthic/epiphytic species and freshwater species living today in the northern Antarctic Peninsula and southern South America. These data suggest contribution from the exposed Patagonian continental shelf and glacial outwash plains of southern Patagonia at the time when sea level reached its minimum. Our results confirm that dust sorting is controlled by the relative intensity of the two main patterns of tropospheric dust transport onto the inner Plateau, i.e. fast low-level advection and long-range high-altitude transport including air subsidence over Antarctica.
(Quaternary Science Reviews. vol. 168, n° 0277-3791, pp. 55-68, 01/07/2017)
DISAT, UNIMI, UNIMIB, IGE, IRD, Grenoble INP, INSU - CNRS, CNRS, UGA [2016-2019], Fédération OSUG, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ENEA
Soil erosion in relation to land-use changes in the sediments of Amik Lake near Antioch antique city during the last 4 kyr
The Amik Basin in the Eastern Mediterranean region occupied since 6000–7000 BC has sustained a highly variable anthropic pressure culminating during the late Roman Period when the Antioch city reached its golden age. The present 6-m-long sedimentary record of the Amik Lake occupying the central part of the Basin constrains major paleoenvironmental changes over the past 4000 years using multi-proxy analyses (grain size, magnetic susceptibility, and x-ray fluorescence (XRF) geochemistry). An age model is provided by combining short-lived radionuclides with radiocarbon dating. A lake/marsh prevailed during the last 4 kyr with a level increase at the beginning of the Roman Period possibly related to optimum climatic condition and water channeling. The Bronze/Iron Ages are characterized by a strong terrigenous input linked to deforestation, exploitation of mineral resources, and the beginning of upland cultivation. The Bronze/Iron Age transition marked by the collapse of the Hittite Empire is clearly documented. Erosion continued during the Roman Period and nearly stopped during the early Islamic Period in conjunction with a decreasing population and soil depletion on the calcareous highland. The soil-stripped limestone outcrops triggered an increase in CaO in the lake water and a general decrease in ZrO2 released in the landscape that lasts until the present day. During the Islamic Period, pastoralism on the highland sustained continued soil erosion of the ophiolitic Amanus Mountains. The Modern Period is characterized by a higher pressure particularly on the Amanus Mountains linked to deforestation, road construction, ore exploitation, and drying of the lake for agriculture practices.
(The Holocene. vol. 28, n° 0959-6836, pp. 104-118, 30/06/2017)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS