The Rance tidal power station: Toward a better understanding of sediment dynamics in response to power generation
A three-dimensional coupled hydrodynamic and morphodynamic numerical model was developed to analyze sediment dynamics in the Rance estuary, in response to the tidal power station (TPS) built near the mouth in the 1960s. The Rance estuary is a relatively small low-discharge steep-sided ria, located along the Brittany coast in northern France, with a maximum spring tidal range of 13.5m. Taking advantage of this significant tidal regime, the first and currently the second largest operational tidal power station in the world was built at the estuary’s mouth, with peak output capacity of 240MW. After calibration and validation of the model for present-day conditions, suspended sediment concentration (SSC) and bed level evolution were evaluated at tidal and fortnightly scales for different scenarios, with and without TPS. Peak SSC are reached during spring tides and specifically during the estuary’s infilling (flood) stage where both turbines and sluice gates are open. Unbalanced with sediment transport during ebb, sediments are accumulated in the main channel of the upper estuary. Under natural tidal forcing (i.e., without TPS), simulations show that an estuarine turbidity maximum forms in the upper estuary, and sediment deposition is significant. However, sedimentation rates are two times lower than those observed in the presence of the TPS. A possible alternative for reducing sediment accumulation in the upper estuary would be the opening of sluice gates simultaneously with the turbines during falling tide, to enhance ebb currents that would allow particles transport towards the estuary’s downstream.
(Renewable Energy. vol. 201, n° 0960-1481, pp. 323-343, 01/12/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Coastal plumes contribution to the suspended sediment transport in the Southwest Atlantic inner continental shelf
Global coastal zones are constantly changing due to the actions of various physical forces. Recent studies show that the supply of suspended sediment of continental origin plays an important role in these changes. Once in the coastal region, this sediment significantly influences the sedimentation process on the inner shelf. Thus, understanding the transport and destination of these suspended sediments is crucial to interpret the morphodynamic evolution of the seabed and biogeochemical processes in the ocean. The Southwest Atlantic Shelf is the largest continental shelf in the Southern Hemisphere and one of the most important in biological production, because of the great continental contribution exercised by both Río de la Plata and Patos Lagoon. Studies in the region showed that these effluents are significantly affected by the El Niño–Southern Oscillation (ENSO) effect, which can interfere with the availability of suspended material inserted into the coastal region. Despite the great efforts of several authors to understand these changes and their interactions with the environment, some questions remain unanswered. Thus, this work aims to fill this gap by answering questions related to the contribution of suspended sediment of continental origin and its behaviour on the Southwest Atlantic Inner Shelf. The behaviour of suspended sediment was investigated in two distinct periods using the hydro-morphodynamic model TELEMAC-3D: one representing normal years, that is, without the effect of ENSO (2005–2006) and the other experiencing the effect of ENSO (2008–2009).The model was calibrated and validated using field data for both studied periods. R esults were based on statistical analysis, such as wavelet and empirical orthogonal function (EOF) analysis, in addition to time series analysis. Results showed that the Southwest Atlantic Inner Shelf is mainly influenced by the fluvial discharge of Río de la Plata and Patos Lagoon, and by the local wind. Río de la Plata is the largest exporter of suspended sediment in the region, with an approximate rate of 1.2 × 108 tons.year-1 in neutral (normal) years and 3.0 × 108 tons.year-1 in years under the influence of ENSO. The Patos Lagoon, on the other hand, exports approximately 1.25 × 107 tons.year-1 in the period without the ENSO effect and 1.35 × 107 tons.year-1 in the period influenced by ENSO. Results also showed that the fluvial discharge interacts with the suspended sediment in seasonal to interannual scales, while the wind contributes to the concentration of suspended sediment on synoptic scales. Still on the wind regime, results show that the local wind regime gains importance particularly when the suspended sediment reaches the coastal region.
(Journal of Marine Systems. vol. 236, n° 0924-7963, 01/12/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Fiches descriptives des habitats marins benthiques de la Manche, de la Mer du Nord et de l’Atlantique
Ce catalogue présente l’ensemble des fiches descriptives des 108 unités de niveau 2 de la troisième version de la typologie NatHab-Atl (habitats marins benthiques de la Manche, de la Mer du Nord et de l’Atlantique), pour servir d’outil d’aide à l’identification et la conservation des habitats. Les habitats ont été décrits sur la base des descriptions existantes dans d’autres typologies complétées par les connaissances disponibles. Ce travail a permis de mettre à jour la typologie en modifiant le libellé de 10 unités pour clarifier leur contenu ou suivre les évolutions taxonomiques de leurs espèces caractéristiques, en supprimant une unité de niveau 3 et déplaçant les unités de niveau 4 qu’elle contenait. Ce travail a également permis d’identifier que le statut de présence en France de 22 unités était à confirmer. Toutes les fiches descriptives ainsi que des photos illustratives supplémentaires sont disponibles en ligne sur les pages habitats de l’INPN.
(pp. 578 pages, 01/12/2022)
PatriNat, MNHN, CNRS, OFB, LEFE, INEE-CNRS, CNRS, UT3, Comue de Toulouse, CNRS, Toulouse INP, Comue de Toulouse, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, DGD.REVE, MNHN, LEMAR, IRD, IFREMER, UBO EPE, CNRS, FR2424, SBR, SU, CNRS, SBR, SU, CNRS, BEEP, IFREMER, UBO EPE, CNRS, IUEM, IRD, INSU - CNRS, UBO EPE, CNRS
Early warning signal for a tipping point suggested by a millennial Atlantic Multidecadal Variability reconstruction
Abstract Atlantic multidecadal variability is a coherent mode of natural climate variability occurring in the North Atlantic Ocean, with strong impacts on human societies and ecosystems worldwide. However, its periodicity and drivers are widely debated due to the short temporal extent of instrumental observations and competing effects of both internal and external climate factors acting on North Atlantic surface temperature variability. Here, we use a paleoclimate database and an advanced statistical framework to generate, evaluate, and compare 312 reconstructions of the Atlantic multidecadal variability over the past millennium, based on different indices and regression methods. From this process, the best reconstruction is obtained with the random forest method, and its robustness is checked using climate model outputs and independent oceanic paleoclimate data. This reconstruction shows that memory in variations of Atlantic multidecadal variability have strongly increased recently—a potential early warning signal for the approach of a North Atlantic tipping point.
(Nature Communications. vol. 13, n° 2041-1723, pp. 5176, 01/12/2022)
IMAU, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BSC-CNS, LOCEAN-VARCLIM, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, Maynooth University
Evaluation of animal and plant diversity suggests Greenland’s thaw hastens the biodiversity crisis
Abstract Rising temperatures can lead to the occurrence of a large-scale climatic event, such as the melting of Greenland ice sheet, weakening the AMOC and further increasing dissimilarities between current and future climate. The impacts of such an event are still poorly assessed. Here, we evaluate those impacts across megadiverse countries on 21,146 species of tetrapods and vascular plants using the pessimistic climate change scenario (RCP 8.5) and four different scenarios of Greenland’s ice sheet melting. We show that RCP 8.5 emission scenario would lead to a widespread reduction in species’ geographic ranges (28–48%), which is projected to be magnified (58–99%) with any added contribution from the melting of Greenland. Also, declines in the potential geographical extent of species hotspots (12–89%) and alterations of species composition (19–91%) will be intensified. These results imply that the influence of a strong and rapid Greenland ice sheet melting, resulting in a large AMOC weakening, can lead to a faster collapse of biodiversity across the globe.
(Communications Biology. vol. 5, n° 2399-3642, pp. 985, 01/12/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Impact of environmental micropollutants and diet composition on the gut microbiota of wild european eels (Anguilla anguilla)
In fish, the gut microbiome plays a crucial role in homeostasis and health and is affected by several organic and inorganic environmental contaminants. Amphidromous fish are sentinel species, particularly exposed to these stressors. We used whole metagenome sequencing to characterize the gut microbiome of wild European eels (Anguilla anguilla) at a juvenile stage captured from three sites with contrasted pollution levels in term of heavy metals and persistent organic pollutants. The objectives were to identify what parameters could alter the gut microbiome of this catadromous fish and to explore the potential use of microbiota as bioindicators of environment quality. We identified a total of 1079 microbial genera. Overall, gut microbiome was dominated by Proteobacteria, Firmicutes and Actinobacteria. Alpha and beta diversity were different amongst sites and could be explained by a reduced number of environmental and biological factors, specifically the relative abundance of fish preys in eels’ diet, PCB101, γHCH (lindane), transnonachlor and arsenic. Furthermore, we identified a series of indicator taxa with differential abundance between the three sites. Changes in the microbial communities in the gut caused by environmental pollutants were previously undocumented in European eels. Our results indicate that microbiota might represent another route by which pollutants affect the health of these aquatic sentinel organisms.
(Environmental Pollution. vol. 314, n° 0269-7491, pp. 120207, 01/12/2022)
UR EABX, INRAE, MIAT INRAE, INRAE, GENOTOUL, UT3, Comue de Toulouse, ENVT, Toulouse INP, INSERM, CNRS, Toulouse INP, Comue de Toulouse, INRAE, MIAT INRAE, INRAE, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GeT-PlaGe, GET, GENOTOUL, UT3, ENVT, INSERM, CNRS, Toulouse INP, INRAE, INRAE
New insights into detecting alizarin from autofluorescence in marked glass eels
Alizarin detection in fish fins is extensively employed because it is easy to use. However, in eels, the eelGFP fluorescent protein may impede the detection of the fluorescent markers in the eel tissues. The study tests the effectiveness of three of the most up-to-date alizarin-detecting technologies on the living body and fins of European glass eels ( Anguilla anguilla L.). The findings demonstrated that the control group had a high autofluorescence at alizarin and eelGFP maxima bands. With fluorescence reflectance imaging (FRI), the eel living body autofluorescence impeded the detection of the marked eels. In contrast with experimental excitation-emission-matrix (EEM) fluorescence analyses, 99% of the marked eels were correctly assigned to their group from fluorescence analyses of their fin cellular contents. With epifluorometry (EPI), 100% of the marked eels were detected with the caudal fin tips when excited at 450–490 nm wavelengths due to a weaker autofluorescence signal. EEM and FRI assays unveiled an average fluorescence quenching 60% and 44% of the marked group respectively, in the alizarin and eelGFP maxima bands. The fluorescence quenching observed is discussed. Results will benefit experimental design by examining autofluorescence effects on mark detection and the development of non-invasive detection methods in this critically endangered species.
(Scientific Reports. vol. 12, n° 2045-2322, pp. 15985, 01/12/2022)
UR EABX, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IMOTION, UB
The effect of the main physicochemical properties of polycyclic aromatic hydrocarbons on their water/sediments distribution
Polycyclic aromatic hydrocarbons (PAHs) are environmental contaminants that continue to attract researchers' attention until these days due to their toxicity and their multisource emission. In this study, levels of 17 active molecules of PAHs were investigated in marine and continental Lebanese aquatic systems. The results showed that Lebanese seawater is more contaminated than several other sites on the Mediterranean Sea. On the marine side, the total concentration of PAHs ranges from 55.7 to 2683.8 ng L−1 in water and from 19.09 to 2025.03 ng g−1 in sediments. On the continental side, the total concentration ranges from 465.7 to 1399.9 ng L−1 in water and from 72.6 to 1074.7 ng g−1 in sediments presenting higher contamination and detection frequency than the marine sites. Pearson test was applied to determine the preference of PAHs toward one of the phases and showed that when the number of rings, the molecular mass and the log Ko/w increase, PAHs accumulate in sediments, and when the water solubility and the vapor pressure of PAHs increase, they tend to remain in the aqueous phase. Moreover, PAHs in Lebanese sediments were combustion-originated and resulted mainly from industrial sites set next to aquatic systems and heavy traffic especially along the Lebanese coastline. Regarding the toxicity effect, the use of the ERL/ERM approach revealed that few sites have individual PAHs levels that may occasionally cause biological adverse effects to benthic organisms; nevertheless, the ecosystem risk of PAHs in Lebanese sediments is low.
(International Journal of Environmental Science and Technology. vol. 20, n° 1735-2630, pp. 10261-10270, 28/11/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Contrasting soil‐ and canopy‐nurse effects in metalliferous systems may be explained by dominant plant functional strategies
Plant-plant interaction studies in metalliferous systems have focused either on the role of facilitation or on negative effects of elemental allelopathy. However, no studies have investigated both of these effects in the same system, and their relationships with the functional strategy of the nurse species, although this is crucial for the ecological restoration of polluted sites. We assessed the effects of two dominant nurse species, with apparent contrasting strategies, on two target species on a slag heap in the Pyrenees (France). We quantified both long-term soil-engineering and short-term canopy effects on the growth of two target species. We also measured morphological traits and leaf metal concentration of the two nurse species and their effects on air moisture, temperature and vapour pressure deficit. Nurse functional strategies, as inferred from morphological traits and leaf metal concentration seem to drive their long-term soil engineering effects on target species: Gypsophila repens, the relative larger and more exploitative species with high leaf metal concentration, had negative long-term effects likely due to elemental allelopathy, whereas Minuartia verna, the relative smaller and more conservative species with lower amount of metals in leaves, had neutral long-term effects. Although Gypsophila repens had a slightly stronger positive effect on microclimate than Minuartia verna, this did not turn into higher short-term effects for the target species. Synthesis and applications: Our study highlights the diverse long and short-term nurse effects on companion species in metalliferous systems. Different nurse species can improve the performance of companion species by mitigation of climatic stress, and ultimately help speed-up the restoration of polluted environments. However, species status regarding leaf metal accumulation has to be verified. For species having a higher metal concentration in their leaves, positive microclimatic effects may be offset by local increase of soil contamination on the long-term.
(Journal of Applied Ecology. vol. 60, n° 0021-8901, pp. 278 - 290, 25/11/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UMR ISPA, Bordeaux Sciences Agro, INRAE
Forest canopy and mistletoe infestation alter the facilitative effects of Juniperus oxycedrus s.l. on woody seedlings on Mount Lebanon (Lebanon)
Questions In this study we investigated the direct effect of the shrub Juniperus oxycedrus s.l. on Mediterranean woody species regeneration, and how this interaction can be modified by the juniper habit, the forest canopy and/or infestation of the juniper by the plant parasite Arceuthobium oxycedri. We also aimed at identifying species response groups in relation to their ecological requirements and successional strategies. Location North of Mount Lebanon, in Horsch Ehden natural reserve, a humid montane Mediterranean forest. Methods We compared the regeneration of all occurring woody species below and outside 111 Juniperus oxycedrus canopies using the random pair sampling method. We calculated eight relative interaction intensity indexes (RIIJuniper) corresponding to the eight treatment combinations of the three factors: forest canopy (forest/gap), mistletoe infestation (with/without) and juniper habit (spreading/erect). We analyzed the RII values at three different levels: community (all species grouped), species group and species. Results Overall, the regeneration of the woody community was facilitated by Juniperus oxycedrus. However, the forest cover significantly reduced the facilitative effect of Juniperus oxycedrus when the latter was not infested by Arceuthobium oxycedri. We identified three species response groups (A: highly facilitated; B: slightly facilitated to neutral; and C: neutral) determined by their response to both Juniperus oxycedrus canopy and forest cover. The most facilitated species were shade-tolerant/drought-intolerant late-successional species. Conclusions The results suggest the importance of shade tolerance in the complex mechanism of forest regeneration that is also affected by a parasite plant (Arceuthobium oxycedri), which boosts regeneration dynamics under forest cover by reducing shrub canopy cover.
(Journal of Vegetation Science. vol. 33, n° 1100-9233, 24/11/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS