Dynamics of organic matter in the Seine Estuary (France): Bulk and structural approaches
Estuaries are important ecosystems from environmental and economical point of views and are the place of numerous transformations of organic matter (OM) during the transfer from land to the ocean. The dynamics of OM in estuarine systems is complex and was only rarely investigated at the structural or molecular level, even though OM transformation in the estuarine aquatic and sediment compartments involves processes taking place at this level. The aim of this study was to constrain the sources and fate of the OM in the Seine Estuary, one of the largest estuaries in France. The spatiotemporal dynamics of the OM along the estuary was investigated by comparing the bulk (elemental and isotopic composition) and structural (solid state 13C nuclear magnetic resonance) features of the different pools of OM – dissolved OM (DOM), particulate OM (POM) and sediment OM collected during five sampling campaigns. Reverse osmosis coupled with electrodialysis (RO/ED) was used to concentrate and isolate DOM, yielding an average organic carbon recovery of 59% (± 15%). RO/ED had a limited effect on DOM properties, DOM showing >75% of similarity with initial estuarine samples based on 3D fluorescence measurements. Bulk and structural analyses of DOM, POM and sedimentary OM showed that OM is mainly of aquatic origin in the Seine Estuary, regardless the OM pool. Nevertheless, significant differences in chemical composition between the three OM pools were observed: higher C/N ratios, carbohydrate, lipid and protein content as well as lower char and lignin contents in DOM than in the other two compartments. Spatial variations of OM properties, for POM and to a lesser extent DOM, were observed along the Seine Estuary based on δ13C and Δ14C analyses and 13C NMR-derived protein and lipid contents, showing the transition from a riverine to a marine-dominated system. In the mixing zone of the estuary, the Δ14C composition of the sediment OM was related to the tidal strength, with strong tides leading to the resuspension of recent sediment OM and weak tides allowing the deposition of recent aquatic OM. Altogether, the combination of bulk and structural techniques showed that the Seine Estuary OM quality is mainly related to the compartment (DOM/POM/sediment) and to a lesser extent to the sampling zone (upstream/maximum turbidity zone/downstream). The approach proposed for the characterization of the Seine Estuary OM could be applied to other estuaries, allowing a better understanding of the complex OM dynamics in such ecosystems.
(Marine Chemistry. vol. 212, n° 0304-4203, pp. 108-119, 01/05/2019)
METIS, EPHE, PSL, INSU - CNRS, SU, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ECOBIO, UR, INEE-CNRS, CNRS, CNRS, IPGP - UMR_7154, INSU - CNRS, IGN, UR, IPG Paris, CNRS, UPCité
Millennial-scale variations of the Holocene North Atlantic mid-depth gyre inferred from radiocarbon and neodymium isotopes in cold water corals
Variations in North Atlantic Ocean mid-depth circulation during the Holocene are poorly understood. It is believed that they had a significant influence on the properties of water entering the Nordic Sea by redistributing heat and freshwater, potentially affecting deep-water formation and climate. To improve our knowledge of the NE Atlantic mid-depth circulation, radiocarbon and neodymium isotope analyses have been then carried out on precisely dated (U-Th) L. pertusa and M. oculata coral fragments from two sediment cores taken at ∼750 m water depth on the SW Rockall Trough margin. Cold-water coral (CWC) εNd values vary between −12.2 ± 0.3 and −16.6 ± 0.4 and result from variable contributions of unradiogenic mid-depth subpolar gyre (mid-SPG) water (∼-15) and more radiogenic Eastern North Atlantic Water (ENAW) (∼-11) which is transported northward to the Rockall Trough by boundary currents along the European margin. Increased coral εNd reflects a westward contraction of the mid-SPG water and a higher proportion of ENAW. The mid-Holocene (from 8.8 to 6.8 ka BP) is marked by unradiogenic coral εNd (from −16.6 ± 0.4 to −14.6 ± 0.5) indicating a greater eastward extension of the mid-SPG. This is followed by a shift from 6.8 to 5 ka BP toward more radiogenic εNd values (from −15.4 ± 0.3 to −13.3 ± 0.2) suggesting a westward contraction of the mid-SPG and a higher proportion of ENAW. The mid-Holocene long-term change in εNd is characterized by millennial variations of up to 2.5 epsilon units well marked during the Late Holocene, indicating that eastward extension of the mid-SPG coeval with warm periods in northern Europe (e.g. the Medieval Climatic Anomaly and the Roman Warm Period). Most of the CWC-derived Δ14C values match the global ocean values indicating that the water masses bathing the corals were generally well ventilated; the exceptions are a few short intervals of eastward extension of the mid-SPG, which are characterized by lower Δ14C during the late Holocene. We propose that these minor Δ14C fluctuations in the Rockall Trough may be related to local changes in the mixed layer depth or to variability in the advection of water from the Labrador Sea where deep convection gives rise to thermocline waters that are relatively depleted in terms of Δ14C. The eastward extension of the mid-SPG between 8.8 and 6.8 ka BP is associated with the Holocene climatic optimum, concurrent with a maximum strength of the Iceland-Scotland Overflow Water (ISOW), which is indicative of an increase in the Atlantic Meridional Overturning Circulation (AMOC). This period is followed by a transition in the North Atlantic circulation, which occurred around 6.8 ka BP, and coincides with the onset of Labrador Sea Water formation, a decrease of the ISOW strength and a contraction of the mid-SPG leading to a greater intrusion of saline subtropical water into the subpolar Atlantic.
(Quaternary Science Reviews. vol. 211, n° 0277-3791, pp. 93-106, 01/05/2019)
GEOPS, UP11, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GEOTRAC, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, UGent, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CLIM, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
Modelling camera viewing angle deviation to improve nearshore video monitoring
Video monitoring the nearshore can provide high-frequency remotely-sensed optical information from which morphological changes and hydrodynamic data can be derived. Although overlooked in most of the studies, it is acknowledged that camera viewing angles can substantially vary in time for a variety of reasons, reducing consistently data accuracy. This paper aims to identify the primary environmental parameters controlling camera shifts at the video monitoring station of Sète (SE France) and develops an empirical model to routinely reduce these deviations. Our model simulates camera movements with an excellent skill (BSS = 0.87) and shows that camera viewing angles’ deviation is primarily controlled by the position of the sun during sunny days, making it predictable. This study opens new perspective to routinely improve camera geometry of video monitoring systems.
(Coastal Engineering. vol. 147, n° 0378-3839, pp. 99-106, 01/05/2019)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CEOAS, OSU
Temporal variations of perfluoroalkyl substances partitioning between surface water, suspended sediment, and biota in a macrotidal estuary
A one-year monitoring study was conducted in a macrotidal estuary to assess the temporal variations and partitioning behavior of perfluoroalkyl and polyfluoroalkyl substances (PFASs). Surface water, suspended particulate matter (SPM), and invertebrates including zooplankton (copepods, mysids) and shrimps were sampled on a monthly basis in the Gironde Estuary (SW France). Environmental parameters such as suspended solid loads, salinity, and river water flow rate were highly variable at the study site. However, moderate seasonal variations were observed in terms of PFAS levels and profiles. Summed PFAS (S22PFASs) concentrations averaged 6.5 ± 2.7 ng L-1 in the dissolved phase and 3.0 ± 1.2 ng g-1 dry weight in the SPM. The S22PFASs was in the range of 1.7 - 13 ng g-1 wet weight in invertebrates. C5-C8 perfluoroalkyl carboxylates (PFCAs) generally prevailed in the dissolved phase, while perfluorooctane sulfonate (PFOS) was dominant in the SPM and biota. Suspended sediment-water partitioning coefficients Log KD and Log KOC were correlated with the perfluoroalkyl chain length, as were the particle bound fraction and bioaccumulation factors (Log BAF). Compound-specific Log BAFs varied within a limited range over the period surveyed. Biomagnification factors (mysids/copepods) were consistently >1 for PFOS, perfluorooctane sulfonamide, and long-chain PFCAs (perfluorodecanoate and perfluorododecanoate), suggesting biomagnification at the base of the estuarine food web.
(Chemosphere. vol. 233, n° 0045-6535, pp. 319-326, 01/05/2019)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IRSTEA, UR EABX, IRSTEA, ISM, UB, INC-CNRS, CNRS, LPTC, UB, CNRS
Changes in protein expression in mussels Mytilus galloprovincialis dietarily exposed to PVP/PEI coated silver nanoparticles at different seasons
Potential toxic effects of Ag NPs ingested through the food web and depending on the season have not been addressed in marine bivalves. This work aimed to assess differences in protein expression in the digestive gland of female mussels after dietary exposure to Ag NPs in autumn and spring. Mussels were fed daily with microalgae previously exposed for 24 h to 10 μg/L of PVP/PEI coated 5 nm Ag NPs. After 21 days, mussels significantly accumulated Ag in both seasons and Ag NPs were found within digestive gland cells and gills. Two-dimensional electrophoresis distinguished 104 differentially expressed protein spots in autumn and 142 in spring. Among them, chitinase like protein-3, partial and glyceraldehyde-3-phosphate dehydrogenase, that are involved in amino sugar and nucleotide sugar metabolism, carbon metabolism, glycolysis/gluconeogenesis and the biosynthesis of amino acids KEGG pathways, were overexpressed in autumn but underexpressed in spring. In autumn, pyruvate metabolism, citrate cycle, cysteine and methionine metabolism and glyoxylate and dicarboxylate metabolism were altered, while in spring, proteins related to the formation of phagosomes and hydrogen peroxide metabolism were differentially expressed. Overall, protein expression signatures depended on season and Ag NPs exposure, suggesting that season significantly influences responses of mussels to NP exposure.
(Aquatic Toxicology. vol. 210, n° 0166-445X, pp. 56-68, 01/05/2019)
UPV / EHU, CIMA, UAlg, LIEC, INSU - CNRS, UL, CNRS, LIST, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Sources and sinks of dissolved inorganic carbon in an urban tropical coastal bay revealed by δ13C-DIC signals
(Estuarine, Coastal and Shelf Science. vol. 220, n° 0272-7714, pp. 185-195, 01/05/2019)
UFF, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BOREA, UNICAEN, NU, MNHN, IRD, SU, CNRS, UA
Evidence for the widespread occurrence of short- and medium-chain chlorinated paraffins in fish collected from the Rhône River basin (France)
Chlorinated paraffins (CPs) are high-volume chemicals used in numerous industrial applications. Their quantitative analysis is extremely challenging and this work presents the optimization of an analytical method based on gas chromatography hyphenated with electron capture negative ionization time-of-flight high-resolution mass spectrometry (GC-ECNI-TOF HRMS) for the simultaneous determination of short-chain and medium-chain CPs (SCCPs and MCCPs, respectively) in fish tissues (i.e. dorsal muscle). The resolution of the TOF-MS analyzer reduced or eliminated isobaric interferences and the CP response was optimized through Design of Experiment. A simple clean-up
(Chemosphere. vol. 223, n° 0045-6535, pp. 232-239, 01/05/2019)
SISYPHE, UPMC, EPHE, PSL, PSL, CNRS, UB, LPTC, UB, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IRSTEA, ONEMA
Pesticide exposure of workers during treatment and re-entry tasks in apple-growing: Results from the CANEPA study in France
(29/04/2019)
BPH, UB, INSERM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UNICAEN, NU, INSERM, UNICANCER/CRLC, NU, EPICENE, BPH, UB, INSERM, LABÉO, PRISMM, PLATON, UNICAEN, NU, UNICAEN, NU
Settlement potential and constraints on the Lower Médoc coastline: results of the LITAQ project and considerations on coastal palaeo-risks in protohistoric times
The adaptation of territorial systems to the ongoing climate change is an issue which implies to test past populations abilities to cope, to “bounce back” or to adapt during similar past environmental changes. The chronostratigraphical and archaeological results, obtained in the frame of the LITAQ project, make it possible to better understand changes encountered by a coastal system (now on the shore front) whose intense occupation since the Neolithic period was linked to the exploitation of specific resources (salt, grazing), then inherent to a fluvial mouth and estuarine system, at present fossilized under the modern dune. One of the issues raised by these results is linked to the decline of salt-related activities during the whole Bronze period, whereas it is bracketed by a period of growing during the Neolithic (for which we were far from measuring the real amplitude) and by the first Iron Age during which salt production appears to be the main motivation for the settlement and the use of coastal marshes. However, the chronological gap, of about thirteen centuries, recorded between the Early Bronze Age (~2200 BC) and the Late Bronze Age (~900 BC), prevents us from using climate changes as a deterministic and unique factor of land-use changes of the Médoc Peninsula around the first millennium. The complex rhythms, that accompany those changes during this period and the subsequent Iron Age, invite us to consider the territorial vulnerability in a context of hydrogeomorphological modifications of the coast synchronously to those of natural components involved in the salt production process. Modalities of the spatial development of this activity (as deduced from the analysis of inventoried remains) in a context of restricted tidal exchanges (i.e. barred estuary), testify to the adaptability of protohistoric Médocan communities, which faced a slow and progressive disturbance of the coastal system; they attest also to the past resilience, in its systemic sense, of a territory nowadays far from major influences.
(Quaternaire. vol. 30, n° 1142-2904, pp. 97-111, 25/04/2019)
PRODIG, UP1, IRD, EPHE, PSL, UP4, UPD7, CNRS, UBM, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, PRODIG (UMR_8586 / UMR_D_215 / UM_115), UP1, IRD, UPD7, SU, CNRS, LETG - Brest, LETG, UNICAEN, NU, UA, EPHE, PSL, UBO EPE, UR2, CNRS, IGARUN, UN, LETG - Caen, LETG, UNICAEN, NU, UA, EPHE, PSL, UBO EPE, UR2, CNRS, IGARUN, UN