Use of valvometry as an alert tool to signal the presence of toxic algae Alexandrium catenella by Mytilus edulis
Valvometry is a non-invasive technique used to continuously monitor gaping behaviour of bivalves at high frequency. In previous laboratory studies, valvometry has revealed a behavioural sensitivity of bivalves to the presence of toxic microalgae in seawater. However, the application of valvometry as an early-warning system for detecting natural occurrences of toxic microalgae and their resulting toxicity in bivalves remains largely unexplored. In this study, valvometry was used to characterise changes in blue mussels ( Mytilus edulis ) gaping behaviour during gradual exposure to the toxic dinoflagellate, Alexandrium catenella , which produces paralytic shellfish toxins (PST). Laboratory experiments were first performed to identify specific gaping behaviour changes and these responses were subsequently validated in natural seawater conditions in a second experiment. Under both laboratory and natural seawater conditions, mussels exposed to A. catenella tended to remain open (yawning) longer than non-exposed mussels. This change in gaping behaviour was observed at PST concentration as low as 30 μg STXeq 100 g–1 of mussel tissue. We suggest that increased opening is likely related to temporary muscular paralysis induced by toxic algae, as this mechanism has been previously reported in other bivalve species. Furthermore, we observed that biological rhythms of valve behaviour related to tidal and daily rhythms were modified when mussels were intoxicated by PSP (Paralytic Shellfish Poisoning). In conclusion, the effects of toxic algae on mussel gaping behaviour reveals that valvometry could be used as an early-warning tool for the presence of toxic Alexandrium sp. in the environment prior to mussels reaching the regulatory threshold (80 μg STXeq 100 g –1 ) for harvest interdiction.
(Frontiers in Marine Science. vol. 9, n° 2296-7745, 23/09/2022)
ISMER, UQAR, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UQAR
Attribution of multi-annual to decadal changes in the climate system: The Large Ensemble Single Forcing Model Intercomparison Project (LESFMIP)
Multi-annual to decadal changes in climate are accompanied by changes in extreme events that cause major impacts on society and severe challenges for adaptation. Early warnings of such changes are now potentially possible through operational decadal predictions. However, improved understanding of the causes of regional changes in climate on these timescales is needed both to attribute recent events and to gain further confidence in forecasts. Here we document the Large Ensemble Single Forcing Model Intercomparison Project that will address this need through coordinated model experiments enabling the impacts of different external drivers to be isolated. We highlight the need to account for model errors and propose an attribution approach that exploits differences between models to diagnose the real-world situation and overcomes potential errors in atmospheric circulation changes. The experiments and analysis proposed here will provide substantial improvements to our ability to understand near-term changes in climate and will support the World Climate Research Program Lighthouse Activity on Explaining and Predicting Earth System Change.
(Frontiers in Climate. vol. 4, n° 2624-9553, 16/09/2022)
MOHC, CCCma, ECCC, NCAR, CMCC, CEN, UHH, GFI / BiU, UiB, IPSL (FR_636), ENS-PSL, PSL, UVSQ, CEA, INSU - CNRS, X, IP Paris, CNES, SU, CNRS, UPCité, GFDL, NOAA, LOCEAN-VARCLIM, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, PNNL, MPI-M, NCAS, NERC, JSG, EMPS, GISS, GSFC, NIES, UOR, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, DMI, LASG, UCAS, CAS
Spatiotemporal dynamics of surface sediment characteristics and benthic macrofauna compositions in a temperate high-energy River-dominated Ocean Margin
The benthic compartment of River-dominated Ocean Margins (RiOMar) is largely affected by sedimentary processes, as well as by natural and anthropogenic disturbances. Recent studies have confirmed the major importance of riverine inputs and local hydrodynamics in the spatial structuration of low- and high-energy temperate RiOMar, respectively. Differences in the nature of these structuring factors could also affect the temporal dynamics of these two types of systems. The present study is aiming at: (1) quantifying spatiotemporal changes in surface sediment and benthic macrofauna within the West Gironde Mud Patch (WGMP; high-energy system) over both short (2016–2018) and longer (2010/2016–2018) time scales, (2) identifying the main environmental factors explaining those changes, and (3) achieving a comparison with the Rhône River Prodelta (RRP; low-energy system) in view of further characterizing the functioning of the benthic components of these two temperate RiOMar. Surface sediment characteristics (grain size, quantitative and qualitative descriptors of particulate organic matter) and benthic macrofauna compositions were assessed based on 4 seasonal sampling of 5 stations located along a depth gradient within the WGMP. Results highlighted the existence of spatial patterns for both surface sediment and benthic macrofauna, which are both better explained by local hydrodynamics. Most variables presented seasonal changes. Benthic macrofauna compositions also showed pluri-annual changes, which were attributed to a cicatrization process following a major disturbance caused by the 2013–2014 series of severe winter storms, and suggests the major role of local hydrodynamics in explaining 2010/2016–2018 temporal changes in WGMP benthic macrofauna compositions. The comparison with the RRP further highlighted major discrepancies between the two systems in the main processes (i.e., hydrodynamics versus river hydrological regime) explaining surface sediment characteristics and benthic macrofauna compositions, which supports current RiOMar typologies.
(Continental Shelf Research. vol. 247, n° 0278-4343, pp. 104833, 15/09/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, DYNECO, IFREMER, CHROME, UNIMES
Land-Use and Land Cover Is Driving Factor of Runoff Yield: Evidence from A Remote Sensing-Based Runoff Generation Simulation
The spatial distribution of water storage capacity has always been the critical content of the study of saturation-excess runoff. Xin’anjiang model uses the water storage capacity curve (WSCC) to characterize the distribution of water storage capacity for runoff yield calculation. However, the mathematical and physical foundations of WSCC are unclear, which is impossible to simulate runoff generation with complex basins accurately. To fill this gap, we considered the dominant role of basin physical characteristics in water storage capacity and developed a new integrated approach to solve the spatial distribution of water storage capacity (L-WSCC) to account for the spatiotemporal dynamics of their impact on runoff generation. The main contribution of L-WSCC was to confer WSCC more physical meaning and the spatial distribution of water storage capacity was explicitly represented more accurately, so as to better express the runoff generation and provide a new approach for runoff yield calculation in non-data basin. L-WSCC was applied to Misai basin in China and promising results had been achieved, which verified the rationality of the method (the mean Nash–Sutcliffe efficiency (NSE):0.86 and 0.82 in daily and hourly scale, respectively). Compared with WSCC, the performance of L-WSCC was improved (mean NSE: 0.82 > 0.78, mean absolute value of flood peak error (PE): 12.74% < 21.66%). Moreover, the results of local sensitivity analyses demonstrated that land-use and land cover was the major driving factor of runoff yield (the change of mean absolute error (ΔMAE): 131.38%). This work was significant for understanding the mechanisms of runoff generation, which can be used for hydrological environmental management and land-use planning.
(Water. vol. 14, n° 2073-4441, pp. 2854, 13/09/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Changements culturels et adaptations aux changements climatiques et environnementaux des derniers Néandertaliens dans le sud de la France
Ce travail a pour but d’améliorer la résolution temporelle des séquences paléoenvironnementales et de leurs chronologies ainsi que la chronologie des différents technocomplexes et cultures du sud de la France de la fin du Paléolithique moyen au début du Paléolithique supérieur. À cette fin, deux études multiproxy ont été menées, utilisant deux carottes profondes du golfe de Gascogne et du golfe du Lion pour reconstruire la végétation et les changements climatiques dans le Sud-Ouest et le Sud-Est de la France en réponse aux réchauffements et refroidissements du Groenland (cycles Dansgaard-Oeschger, D-Os) et aux refroidissements de l'Atlantique Nord (événements d’Heinrich, HEs). Les résultats montrent des amplitudes différentes dans l'expansion de la forêt associée aux réchauffement D-O en fonction de la latitude et liées à différentes configurations orbitales. Pendant les stades de Heinrich (HSs), les différentes amplitudes de l'expansion semi-désertique dans les deux régions seraient le résultat de différentes intensités de la circulation thermohaline et des processus océaniques locaux associés à l'instabilité de la calotte laurentienne. La datation IRSL de la carotte MD04-2845 et l'application du récent modèle âge-profondeur (ChronoModel & ArchaeoPhases) utilisant des statistiques bayésiennes et des contraintes stratigraphiques sur les deux carottes ont permis d'affiner les chronologies des changements environnementaux. La construction de bases de données archéologiques critiques pour les deux régions et l'application de ChronoModel aux séquences archéologiques ont amélioré la chronologie des changements technologiques des Néandertaliens et des Hommes Anatomiquement Modernes (HAM) en Europe occidentale. Malgré l'amélioration des chronologies, l'identification de synchronies potentielles reste difficile en raison des incertitudes associées aux différentes chronologies. Néanmoins, cette étude suggère que l'aridification progressive du paysage pendant la dernière période glaciaire a favorisé l'arrivée des HAM en Europe occidentale, entraînant une compétition avec les Néandertaliens pour les mêmes niches écologiques et produisant la disparition de ces derniers.
(12/09/2022)
UB, UBM, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Headland Rip Very-low-Frequency Fluctuations and Surf Zone Eddies during High-Energy Wave Events
Abstract A wave group-resolving model is used to investigate the driving mechanisms and the spatio-temporal variability of very-low-frequency (VLF) fluctuations of an headland deflection rip, measured during a 4-m oblique wave event. Surf zone eddies (SZE) occurring in the presence of a strongly-sheared longshore current V at a longshore-uniform beach are first modelled. The spectral signature and the variability of SZE are displayed and compared with the literature. The model is then used to explore the dynamics of vorticity in the surf zone and against a headland under energetic oblique wave conditions. The resulting weakly-sheared V is found to host large-scale SZE propagating towards the headland at a speed decreasing seaward. Vorticity animations and spectral diagrams indicate that VLF fluctuations of the deflection rip are driven by the deflection of the upstream SZE. In line with measurements, periods of 40 min to 1 h dominate the spectrum hundreds of meters from the headland at low tide. At high tide, vorticity spectra in the rip are much narrower than in the surf zone, suggesting that the headland enforces the merging of SZE. This mechanism is further analysed using idealized simulations with varying headland lengths, aiming at extending traditional deflection patterns at the VLF scale. Finally, we discuss the existence of a continuum in SZE driving mechanisms, going from fully wave group-driven to both wave group and shear instability-driven SZE for weakly- and strongly-sheared V, respectively. This continuum suggests the importance of wave groups to produce SZE under energetic wave conditions.
(Journal of Physical Oceanography, n° 0022-3670, 09/09/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Impact of Holocene coastal changes on past human communities : results from an interdisciplinary approach in the Gironde estuary mouth (North-Médoc, SW France
(06/09/2022)
UBM, CNRS, PRODIG (UMR_8586 / UMR_D_215 / UM_115), UP1, IRD, SU, CNRS, UPCité, LETG - Brest, UBO EPE, UR2, CNRS, LETG, UBO EPE, UR2, CNRS, Nantes Univ - IGARUN, LASCARBX, UB, UBM, PRODIG, UP1, IRD, EPHE, PSL, UP4, UPD7, CNRS, PRODIG (UMR_8586 / UMR_D_215 / UM_115), UP1, IRD, UPD7, SU, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UBO EPE
Sorption of benzo(a)pyrene and of a complex mixture of petrogenic polycyclic aromatic hydrocarbons onto polystyrene microplastics
Microplastics (MPs) largely occur in aquatic ecosystems due to degradation of larger plastics or release from MP-containing products. Due to the hydrophobic nature and large specific surface of MPs, other contaminants, such as polycyclic aromatic hydrocarbons (PAHs), can potentially sorb onto MPs. Several studies have addressed the potential impact of MPs as vectors of PAHs for aquatic organisms. Therefore the role of MPs as sorbents of these compounds should be carefully investigated. The present study aimed to determine the sorption capacity of benzo(a)pyrene (B(a)P), as a model pyrolytic PAH, to polystyrene (PS) MPs of different sizes (4.5 and 0.5 μm). In addition, the sorption of PAHs present in the water accommodated fraction (WAF) of a naphthenic North Sea crude oil to 4.5 μm MPs was also studied as a model of a complex mixture of petrogenic PAHs that could appear in oil-polluted environments. The results indicated that 0.5 μm MPs showed higher maximum sorption capacity (Q max ) for B(a)P (145–242.89 μg/g) than 4.5 μm MPs (30.50–67.65 μg/g). From the WAF mixture, naphthalene was sorbed at a higher extent than the other PAHs to 4.5 μm MPs but with weak binding interactions (K f = 69.25 L/g; 1/n = 0.46) according to the analysis of the aqueous phase, whereas phenanthrene showed stronger binding interactions (K f = 0.24 L/g; 1/n = 0.98) based on the analysis of the solid phase. Sorption of PAHs of the complex WAF mixture to 4.5 μm MPs was relatively limited and driven by the hydrophobicity and initial concentration of each PAH. Overall, the results indicate that sorption estimations based solely on the analysis of the aqueous phase could overestimate the capacity of MPs to carry PAHs. Therefore, controlled laboratory assays assessing the “Trojan Horse effect” of MPs for aquatic organisms should consider these findings in order to design accurate and relevant experimental procedures.
(Frontiers in Environmental Chemistry. vol. 3, 02/09/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UPV / EHU
Did eustatic sea-level control deep-water systems at Milankovitch and timescales?: An answer from Quaternary Pearl River margin
As one of the most important forcing factors, sea level fluctuations exert a major influence on deep-water depositional processes, however, it is still not well understood how they control the evolution of the specific deep-water system over different timescales. For relatively longer (1 My) and shorter (100 Ky) timescales, we characterize deep-water sedimentary records on the Pearl River margin using seismic and borehole data, and then compare them with the contemporaneous sea-level curve to exam the varied roles sea levels have played in impacting the development of the deep-marine system. Results indicate that over both the 1 My-scale and the 100 Ky-scale, the studied deep-water system shows systematic variations that are strongly suggested to arise from the modulation of sea levels. Specifically, over the 1 My-scale, facies and depocenters of the deep-water system all show significant changes. Large fan lobes (consisting of both turbidites and mass-transport deposits) with more distal depocenters likely correspond with low-amplitude and high-frequency sea level fluctuations and slightly rising shelf edge trajectories, whereas smaller turbidite fan lobes with more proximal depocenters likely reflect high-amplitude and low-frequency sea level fluctuations and steeply rising shelf-edge trajectories. In contrast, within the 100 Ky-scale of a glacial-interglacial cycle, the composition of deep-water deposits also shows significant variations. Coarser-grained deposits with higher organic carbon (TOC) content and lower calcium carbonate (CaCO3) content are interpreted to reflect periods of glacial sea-level lowstand, whereas finer-grained sediments having lower TOC and higher CaCO3 content reflect interglacial sea-level highstand. Moreover, the spectrum characteristics of these constituent curves are very similar to those of contemporaneous sea levels, reflecting Milankovitch climatic forcings and further validating the tight coupling between sea-level stands and sediment compositions. These correlations between sedimentary records and sea level behaviors suggest that it was mainly a long-term change in the amplitude and frequency of eustatic cycles that controlled the overall architecture of the deep-water system, whereas it was shorter term, changing sea-level stands that played a role and impacted the deep-water sediment composition.
(Sedimentary Geology. vol. 439, n° 0037-0738, 01/09/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Phenolic fingerprints of the Pacific seagrass Phyllospadix torreyi - Structural characterization and quantification of undescribed flavonoid sulfates
Four undescribed flavonoid sulfates were isolated from Phyllospadix torreyi S. Watson foliar tissue. In addition, nine known flavonoid sulfates and three phenolic acids were isolated from the same extract, of which seven had never been reported for the genus Phyllospadix. Structural elucidation of individual phenolics was assigned using complementary informations from their spectral evidence (HPLC-DAD, LC-MS, NMR, and UV) and chemical behavior. The inter-annual variation in phenolic concentrations was determined by quantitative HPLC-DAD over a three-year period. The results showed a relative constancy of phenolic content over time and the high prevalence of flavonoid disulfates (70–90% of the total flavonoids detected). All samples were found dominated by the unreported nepetin 7, 3′-disulfate and 5-methoxyluteolin 7, 3′-disulfate, followed by luteolin 7, 3′-disulfate. Considering the economic potential of flavonoid sulfates in the pharmaceutical and nutraceutical segments, a sample of detrital leaves was also analyzed. The same phenolic pattern was found and the concentration of the individuals, although lower than in fresh material, makes this abundant biomass of interest for dietary and pharmaceutical applications.
(Phytochemistry. vol. 201, n° 0031-9422, 01/09/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS