Antarctic sea-ice and palaeoproductivity variation over the last 156,000 years in the Indian sector of Southern Ocean
(Marine Micropaleontology. vol. 160, n° 0377-8398, pp. 101894, 01/09/2020)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Impacts of land reclamation on sediment transport and sedimentary environment in a macro-tidal estuary
During the past decades, extensive coastal areas have been reclaimed along the coastline of China, while the physical mechanisms of human pressures on estuarine-sedimentation are largely unknown. This study investigates the impacts of a land reclamation activity on estuarine sedimentation in the Yalu River Estuary (YE), China. For this purpose, we perform a multidisciplinary approach that combines rare earth element (REE) sediment records and numerical simulations. REE pattern of two sediment core samples from the main estuarine branch changed from diverse to homogenous after the early 1970s, which indicates that the estuarine sedimentary environment experienced dramatic change after the land reclamation activity completed in 1975. In order to explore physical drivers behind this change, hydro-sedimentary dynamics were simulated using Finite Volume Coastal Ocean Model (FVCOM) and an improved Track Marine Plastic Debris (TrackMPD) models. After the land reclamation, model results show that: (1) the degree of flood dominance decreased, and the tidal-choking effect was enhanced in the main branch. (2) The estuary became more well-mixed due to the stronger tidal current; (3) Suspended-sediment concentration (SSC), especially SSC in the bottom layer was increased. (4) The landward sediment flux caused by tidal pumping decreased significantly and the YE may turn into a sediment source instead of a sink if more land is reclaimed in the future. Furthermore, sediments in the main branch were likely from different sources before reclamation but became a homogenous mixture afterwards. This study qualitatively demonstrates the human-induced impacts on estuarine sedimentation using a multidisciplinary method.
(Estuarine, Coastal and Shelf Science. vol. 242, n° 0272-7714, pp. 106861, 01/09/2020)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Satellite and in situ monitoring of Chl-a, Turbidity, and Total Suspended Matter in coastal waters: experience of the year 2017 along the French Coasts
The consistency of satellite and in situ time series of Chlorophyll-a (Chl-a), Turbidity and Total Suspended Matters (TSM) was investigated at 17 coastal stations throughout the year 2017. These stations covered different water types, from relatively clear waters in the Mediterranean Sea to moderately turbid regions in the Bay of Biscay and the southern bight of the North-Sea. Satellite retrievals were derived from MODIS/AQUA, VIIRS/NPP and OLCI-A/Sentinel-3 spectral reflectance. In situ data were obtained from the coastal phytoplankton networks SOMLIT (CNRS), REPHY (Ifremer) and associated networks. Satellite and in situ retrievals of the year 2017 were compared to the historical seasonal cycles and percentiles, 10 and 90, observed in situ. Regarding the sampling frequency in the Mediterranean Sea, a weekly in situ sampling allowed all major peaks in Chl-a caught from space to be recorded at sea, and, conversely, all in situ peaks were observed from space in a frequently cloud-free atmosphere. In waters of the Eastern English Channel, lower levels of Chl-a were observed, both in situ and from space, compared to the historical averages. However, despite a good overall agreement for low to moderate biomass, the satellite method, based on blue and green wavelengths, tends to provide elevated and variable Chl-a in a high biomass environment. Satellite-derived TSM and Turbidity were quite consistent with in situ measurements. Moreover, satellite retrievals of the water clarity parameters often showed a lower range of variability than their in situ counterparts did, being less scattered above and under the seasonal curves of percentiles 10 and 90.
(Journal of Marine Science and Engineering. vol. 8, n° 2077-1312, pp. 665, 28/08/2020)
IFREMER, LERBL, COAST, IFREMER, LIENSs, INSU - CNRS, ULR, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], SBR, SU, CNRS, FR2424, SBR, SU, CNRS, LOMIC, INSU - CNRS, SU, CNRS, OOB, SU, CNRS, LERPAC, COAST, IFREMER, IHPE, UPVD, IFREMER, CNRS, UM, MIO, IRD, AMU, INSU - CNRS, UTLN, CNRS
Flash Rips in Voodoo Land
(Journal of Coastal Research. vol. 101, n° 0749-0208, 26/08/2020)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Linking carbonate sediment transfer to seafloor morphology: Insights from Exuma Valley, the Bahamas
The depositional record of carbonate slopes provides a valuable archive of past environmental and climatic changes. Modern carbonate slopes reveal morphological variabilities (for example, gullies and canyons) shaped by episodic slope collapses and turbidity currents. Furthermore, climate-induced fluctuations in sea level regulate sediment availability and delivery to the deep-sea. Morphological and climatic controls on calciclastic sediment transfer are often complex to decipher. The aim of this study is to link seafloor morphology and depositional processes in an active carbonate submarine channel (Exuma Valley, the Bahamas) over the last 40 kyr. The dataset includes multibeam and seismic surveys, and two sediment cores retrieved from the valley axis. A series of abrupt slope-breaks, called knickpoints, occurs along Exuma Valley, and plays a key role in sediment transport and accumulation. Initiation processes proposed for knickpoint formation include bank-collapse, side gully erosion and loss of confinement. Slope collapses detected on the bathymetry prevail in the upstream muddy section of the submarine valley, as attested to by a planktic-rich debrite–turbidite couplet in the first core. In contrast, the second core collected downstream of the knickpoints train, includes 32 bioclastic sandy event-beds (i.e. turbidites). Hydrodynamic sorting generates grain segregation (for example, Halimeda-rich base versus planktic-rich top) and geochemical contrasts (Sr/Ca) in turbidites. Turbidite frequency and grain composition within beds reflect the variation of carbonate sources during glacial–interglacial periods. This research allows to link slope morphology with deposits of a modern large-scale carbonate factory, and to deduce sea-level changes over that last 40 kyr in the Bahamas. These results can provide new perspectives on the understanding of ‘source to sink’ mechanisms in carbonate systems.
(Sedimentology. vol. 68, n° 0037-0746, pp. 609-638, 26/08/2020)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Assessment of the Environmental Significance of Heavy Metals Pollution in Surficial Sediments of South Brittany Waters, France: An Ecological Risk Assessment Approach
Distribution patterns of selected heavy metals content in sediments from the Bay of Quiberon and Gulf of Morbihan were studied to understand the current heavy metals contamination due to urbanization and mariculture activities in the coastal area. Therefore, a survey was conducted and 196 sediments collected were characterized for heavy metals content using Inductively Coupled Plasma -Mass Spectrometry (ICP-MS) after mix acid digestion process.
The distribution maps of the concentrations of the heavy metals studied were produced as an isopleth map based on data interpolation by the ArcGIS software application. The association with the adverse effects on aquatic organisms was determined by the classification of the sediment according to the sediment quality guidelines. Therefore, two approaches were employed namely; direct comparison with Sediment Quality Guidelines (SQGs) by USEPA and comparison with other numerical SQGs, threshold effect level/probable effect level, and effect range low /effect range medium. In order to estimate the effect of multiple contaminations of heavy metals, the mean-ERM-quotient was calculated at each sampling point.
(06/08/2020)
NTOU, LGO, UBS, IFREMER, UBO EPE, CNRS, LBCM, UBS, UBO EPE, IUEM, IRD, INSU - CNRS, UBO EPE, CNRS, CNRS, GEO-OCEAN, UBS, IFREMER, INSU - CNRS, UBO EPE, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Corbicula fluminea: A sentinel species for urban Rare Earth Element origin
The increase in the global population, coupled with growing consumption of Rare Earth Elements (REEs), has led to increasing transfer of these emerging contaminants into the environment, particularly through the effluents from wastewater treatment plants (WWTP). The objectives of this study were to determine the geochemical quality of a French river subject to strong urban pressure (the Jalle River in the Bordeaux area) and to examine the bioavailability of natural and anthropogenic REEs in a model species of freshwater bivalve, the Asian clam Corbicula fluminea. To this end, two fractions (dissolved and total) of the water from the Jalle River were sampled and the bivalves were exposed by in situ caging during a three-month monitoring period. The REE patterns obtained showed the presence of Gadolinium (Gd) anomalies in the dissolved and total fractions as well as in Corbicula fluminea. The apparent bioavailability of natural REEs was in the following order for the dissolved fraction: Medium REEs (MREEs) > Light REEs (LREEs) > Heavy REEs (HREEs) and for the particulate fraction: MREEs > LREEs = HREEs. These results highlight the importance of the particulate fraction in the study of the bioavailability of REEs in bivalves. An increase of anthropogenic Gd (Gdanth) was observed in the dissolved fraction between the upstream site (3.4 ng.L−1) and the WWTP Downstream site (48.4 ng.L−1). The Gd anomaly observed in the water was also observed in Corbicula fluminea with a significant increase in the bioaccumulation of Gdanth, from 1.5 ± 1 ng.gDW−1 upstream to 4.1 ± 0.7 ng.gDW−1 downstream of the WWTP effluents, thus confirming the enhanced bioavailability of medical-origin Gd to freshwater bivalves. This study strongly suggests that Corbicula fluminea can be used as a sentinel species in the monitoring of Gd contamination of medical origin. It would thus appear important to consider the potential entry of this contaminant into the human food chain via other, commercially exploited bivalve species.
(Science of the Total Environment. vol. 732, n° 0048-9697, pp. 138552, 01/08/2020)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
An overview and brief description of common marine organic-walled dinoflagellate cyst taxa occurring in surface sediments of the Northern Hemisphere
Organic-walled resting cysts of planktonic dinoflagellates occur commonly in modern marine sediment where they represent, with rare exceptions, the only geologically preservable part of the life cycle. Although many species do not produce fossilizable resting cysts, upper Quaternary sediments contain a diverse cyst record that is used frequently for paleoenvironmental reconstruction and stratigraphic analysis. Reconstructions of past sea-surface conditions rely on an understanding of the distributions of dinoflagellate cysts in modern sediments linked to their respective environmental parameters, underpinned by sound taxonomy and standardized nomenclature. Stratigraphic studies additionally require knowledge of morphological details to distinguish extant from similar extinct taxa. Here, 51 dinoflagellate cyst species and two informal cyst morphotypes that are commonly encountered during routine palynological analysis of upper Quaternary marine sediments from the Northern Hemisphere are briefly described taxonomically and illustrated. In addition, their lowest stratigraphic occurrences are provided.
(Marine Micropaleontology. vol. 159, n° 0377-8398, pp. 101814 (46p.), 01/08/2020)
UNB, SEOS, UVIC, LERBO, COAST, IFREMER, AWI, GEOTOP, EPM, UdeM, UQAT, UQAR, UQAM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LGO, UBS, IFREMER, UBO EPE, CNRS, UQAM, ISMER, UQAR
A high-resolution elemental record of post-glacial lithic sedimentation in Upernavik Trough, western Greenland: History of ice-sheet dynamics and ocean circulation changes over the last 9100 years
A better understanding of the past dynamics of local sectors of the Greenland ice sheet (GIS) with regards to ocean circulation and climate changes can be developed from proxy records derived from marine sedimentary archives. Here we investigate the post 9.1 cal. Kyr BP history of the western sector of the GIS from the XRF core scanner-derived geochemistry of a sediment core retrieved from Upernavik Trough, Melville Bay. The elemental signature of material derived from Melville Bay glaciers, Upernavik Isstrom and Rink Isbrae can be inferred from the geology of the bedrocks drained by these major ice streams of the western GIS. Changes in abundance of Fe-rich basaltic material reflect changes in West Greenland Current (WGC) strength. Contributions from Melville Bay glaciers were dominant during the early part of the record as a result of the rapid retreat of this stretch of the NW GIS. Atmospheric warming and strengthened WGC between 7.5 and 5 cal. Kyrs BP promoted contributions from distal southern sources of lithic material to the sedimentation over Upernavik Trough. The Neoglacial shift in climate and ocean circulation led to a general reduction in the delivery of lithic material from western GIS glacier outlets glaciers. The particular geomorphology of the fjord hosting Rink Isbrae as well as the important depth of the Uummannaq Trough likely explain the high relative contribution of this glacier to the lithic sedimentation over Upernavik Trough during the later part of the Holocene despite a weakened WGC.
(Global and Planetary Change. vol. 191, n° 0921-8181, pp. 103217, 01/08/2020)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ULaval, INSU - CNRS, CNRS, UQAR, GEOTOP, EPM, UdeM, UQAT, UQAR, UQAM, LOCEAN-VOG, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité
Distribution of common modern dinoflagellate cyst taxa in surface sediments of the Northern Hemisphere in relation to environmental parameters: The new n=1968 database
(Marine Micropaleontology. vol. 159, n° 0377-8398, pp. 101796, 01/08/2020)
GEOTOP, EPM, UdeM, UQAT, UQAR, UQAM, UQAM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ISMER, UQAR, UNB, AWI, UBO EPE, GEO-OCEAN, UBS, IFREMER, INSU - CNRS, UBO EPE, CNRS, IUEM, IRD, INSU - CNRS, UBO EPE, CNRS, SEOS, UVIC