Effects of metals and persistent organic pollutants on the fitness and health of juveniles of the endangered European sturgeon Acipenser sturio exposed to water and sediments of the Garonne and Dordogne rivers
The last remaining population of European sturgeon (Acipenser sturio) lives in the Gironde-Garonne-Dordogne (France) catchment (GGD). Captive young individuals are released into the GGD hydrosystem each year, as part of a restocking programme. This study aims to assess the health status of juveniles A. sturio to current conditions in the GGD hydrosystem, to evaluate their capacity to survive and grow in a moderately anthropized ecosystems. 3-month-old farmed sturgeons were exposed for one month in experimental conditions that mimic the environmental conditions in the Garonne and Dordogne rivers, followed by five months of depuration. After one month of exposure, fish exposed to Dordogne and Garonne waters bioaccumulated higher levels of metals and persistent organic pollutants, displayed a reduced hepato-somatic index, and had depleted levels of lipids and glycogen content in their liver, when compared with the Reference group. However, metabolic and swimming performance, as well as the costs of swimming were not impaired. After the 5 months depuration, a significant decrease of K was observed for all exposure conditions. HSI also decreased with time. The overall health status and adaptive capacity of juvenile A. sturio appeared to be maintained over the experimental 6 months' period. Juveniles of A. sturio seem to have the adaptive capacity to survive and grow in the GGD hydrosystem, after being released as part of a restocking programme.
(Ecotoxicology and Environmental Safety. vol. 225, n° 0147-6513, pp. 112720, 01/12/2021)
LBBM, EDF [E.D.F.], SU, CNRS, OOB, SU, CNRS, LIENSs, INSU - CNRS, ULR, CNRS, UR EABX, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, APEX, PAnTher, ONIRIS, INRAE, PAnTher, ONIRIS, INRAE
Impact de la pollution lumineuse sur le rythme comportemental de l’huître Crassostrea gigas
(Médecine du sommeil. vol. 18, n° 1769-4493, pp. 196, 01/12/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Stranded in the high tide line: spatial and temporal variability of beached microplastics in a semi-enclosed embayment (Arcachon, France)
Coastal environments are a predominant ultimate destination of marine debris, becoming a key focus of studies assessing microplastic (MP) contamination. Here, we described the visible fraction of MP (from 0.5 to 5 mm) that washed up during the high tide at different sites of a semi-enclosed mesotidal bay and investigated the main abiotic factors driving MP beaching. Three contrasted beaches of the Arcachon Bay (SW France) were monitored on a monthly basis during 2019. Samplings were made along a 100 m longitudinal transect at the high-water strandline (4 quadrats of 0.25m2) and at an intermediate tidal range. Each sampled particle was characterized by morphometric data (e.g. size, shape, color, roughness) and polymer identification was performed by ATR-FTIR technique. Results show that MP concentration was higher on the beach located at the mouth of the bay (36.0 ± 39.2 MP.m-2) than at the back and the outside of the bay (respectively 2.7 ± 4.4 and 1.7 ± 2.4 MP.m-2). This may be related to the strong currents at the entry of the embayment and the beach orientation, exposed to predominant winds. Beached MP were mainly pre-production pellets and fragments as they represented respectively 49% and 39% of all analyzed shapes. Polymers with low density were particularly abundant. Polyethylene represented 69% of all the particles while polypropylene accounted for 17% and polystyrene for 10%. We also observed that MP were mostly washed up when wind, waves and river flow were more intense. Analysis suggest that wind direction and speed are key factors influencing beaching as strong onshore wind enhance this process.
(Science of the Total Environment. vol. 797, n° 0048-9697, pp. 149144, 27/11/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CBMN, UB, ENITAB, INC-CNRS, CNRS
Application of an iterative source localization strategy at a chlorinated solvent site
This study presents an inverse modeling strategy for organic contaminant source localization. The approach infers the hydraulic conductivity field, the dispersivity, and the source zone location. Beginning with initial observed data of contaminant concentration and hydraulic head, the method follows an iterative strategy of adding new observations and revising the source location estimate. Non-linear optimization using the Gauss-Levenberg-Marquardt Algorithm (PEST++) is tested at a real contaminated site. Then a limited number of drilling locations are added, with their positions guided by the Data Worth analysis capabilities of PYEMU. The first phase of PEST++, with PYEMU guidance, followed by addition of monitoring wells provided an initial source location and identified four additional drilling locations. The second phase confirmed the source location, but the estimated hydraulic conductivity field and the Darcy flux were too far from the measured values. The mismatch led to a revised conceptual site model that included two distinct zones, each with a plume emanating from a separate source. A third inverse modelling phase was conducted with the revised site conceptual model. Finally, the source location was compared to results from a Geoprobe@ MiHPT campaign and historical records, confirming both source locations. By merging measurement and modeling in a coupled, iterative framework, two contaminant sources were located through only two drilling campaigns while also reforming the conceptual model of the site. © 2021 The Authors
(Journal of Hydrology X. vol. 13, n° 2589-9155, 26/11/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Abrupt climatic variability: Dansgaard-Oeschger events
This chapter describes the millennial-scale climatic variability in the atmosphere of Greenland during the Last Glacial Cycle (MIS 5e–MIS 1, 116–14.7 cal ka BP), that is, the Dansgaard–Oeschger (D–O) cycles, and the associated global changes in greenhouse gas atmospheric concentrations, particularly CO2 and CH4, and atmospheric circulation (Ca2+ concentration and d-excess). This chapter highlights the contrasting regional impact of the D–O cycles on the North Atlantic Sea surface temperatures and the vegetation and climate across Europe, as well as the synchronicity between changes in Greenland temperature and the hydrological cycle in the tropics and midlatitudes of the Northern Hemisphere. By contrast, the shape and phasing of millennial-scale events between Greenland and Antarctica differ between the two regions. The mechanisms underlying such a variability are still under debate.
(pp. 175-180, 19/11/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Abrupt (or millennial or suborbital) climatic variability: Heinrich events/stadials
The causes and consequences of the episodic iceberg-discharge events from the Hudson Strait Ice Stream of the Laurentide Ice Sheet, or Heinrich events (HE), are one of the most explored topics in Pleistocene palaeoclimatology. In this chapter, we summarise three decades of intense research while introducing recent results from both the European and Cordilleran Ice Sheets that could call for a paradigm shift in our understanding of the HE.
(pp. 181-187, 19/11/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
An overview of the Last Glacial Cycle
This introductory chapter succinctly describes the evolution of the European Ice Sheet configuration during the Last Glacial Period, from the end of Marine Isotopic Stage (MIS) 5e to the onset of MIS 1 (116–14.7 cal ka BP), and defines the millennial-scale changes that have punctuated this time period, that is, the Dansgaard–Oeschger cycles and the different episodes of iceberg discharges, including the Heinrich events. A short description of the impact of these millennial-scale changes on European vegetation and climate is also provided as a prelude to the following chapters.
(pp. 165-169, 19/11/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Relation between orbital velocities, pressure and surface elevation in non-linear nearshore water waves
The inability of the linear wave dispersion relation to characterize the dispersive properties of non-linear shoaling and breaking waves in the nearshore has long been recognised. Yet, it remains widely used with linear wave theory to convert between sub-surface pressure, wave orbital velocities and the free surface elevation associated with non-linear nearshore waves. Here, we present a non-linear fully dispersive method for reconstructing the free surface elevation from sub-surface hydrodynamic measurements. This reconstruction requires knowledge of the dispersive properties of the wave field through the dominant wavenumbers magnitude κ , representative in an energy-averaged sense of a mixed sea-state composed of both free and forced components. The present approach is effective starting from intermediate water depths - where non-linear interactions between triads intensify - up to the surf zone, where most wave components are forced and travel approximately at the speed of non-dispersive shallow-water waves. In laboratory conditions, where measurements of κ are available, the non-linear fully dispersive method successfully reconstructs sea-surface energy levels at high frequencies in diverse non-linear and dispersive conditions. In the field, we investigate the potential of a reconstruction that uses a Boussinesq approximation of κ , since such measurements are generally lacking. Overall, the proposed approach offers great potential for collecting more accurate measurements under storm conditions, both in terms of sea-surface energy levels at high frequencies and wave-by-wave statistics ( e.g. wave extrema). Through its control on the efficiency of non-linear energy transfers between triads, the spectral bandwidth is shown to greatly influence non-linear effects in the transfer functions between sub-surface hydrodynamics and the sea-surface elevation.
(Journal of Physical Oceanography, n° 0022-3670, 19/11/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IMB, UB, Bordeaux INP, CNRS, LEGI, CNRS, Fédération OSUG, UGA, Grenoble INP, UGA
Tree genotypes affect rock lichens and understory plants: examples of trophic-independent interactions
Genetic variation in foundation tree species can strongly influence communities of trophic-dependent organisms, such as herbivorous insects, pollinators, and mycorrhizal fungi. However, the extent and manner in which this variation results in unexpected interactions that reach trophic-independent organisms remains poorly understood, even though these interactions are essential to understanding complex ecosystems. In pinyon–juniper woodland at Sunset Crater (Arizona, USA), we studied pinyon (Pinus edulis) that were either resistant or susceptible to stem-boring moths (Dioryctria albovittella). Moth herbivory alters the architecture of susceptible trees, thereby modifying the microhabitat beneath their crowns. We tested the hypothesis that this interaction between herbivore and tree genotype extends to affect trophic-independent communities of saxicolous (i.e., growing on rocks) lichens and bryophytes and vascular plants beneath their crowns. Under 30 pairs of moth-resistant and moth-susceptible trees, we estimated percent cover of lichens, bryophytes, and vascular plants. We also quantified the cover of leaf litter and rocks as well as light availability. Four major findings emerged. (1) Compared to moth-resistant trees, which exhibited monopodial architecture, the microhabitat under the shrub-like susceptible trees was 60% darker and had 21% more litter resulting in 68% less rock exposure. (2) Susceptible trees had 56% and 87% less cover, 42% and 80% less richness, and 38% and 92% less diversity of saxicolous and plant communities, respectively, compared to resistant trees. (3) Both saxicolous and plant species accumulated at a slower rate beneath susceptible trees, suggesting an environment that might inhibit colonization and/or growth. (4) Both saxicolous and plant communities were negatively affected by the habitat provided by susceptible trees. The results suggest that herbivory of moth-susceptible trees generated litter at high enough rates to reduce rock substrate availability, thereby suppressing the saxicolous communities. However, our results did not provide a causal pathway explaining the suppression of vascular plants. Nonetheless, the cascading effects of genetic variation in pinyon appear to extend beyond trophic-dependent moths to include trophic-independent saxicolous and vascular plant communities that are affected by specific tree–herbivore interactions that modify the local environment. We suggest that such genetically based interactions are common in nature and contribute to the evolution of complex communities.
(Ecology. vol. 103, n° 0012-9658, 17/11/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Révision des vers spaghetti (Annélides, Terebellidae sensu lato) des côtes françaises
Cette thèse a pour objectif de réviser la taxonomie des espèces françaises d’annélides polychètes appartenant aux cinq familles des Terebellidae sensu lato (Polycirridae, Telothelepodidae, Terebellidae sensu stricto, Thelepodidae et Trichobranchidae). Ces vers spaghetti sont caractérisés par la présence de nombreux tentacules buccaux non rétractables servant à leur nutrition et leur assurant un régime déposivore.Les individus étudiés dans le cadre de cette thèse ont été prélevés lors de différents projets de recherche et d’observation menés par les équipes hébergées dans les stations marines françaises, mais également lors d’échantillonnages spécifiques. Des matériels types, archivés au Museum National d’Histoire Naturelle, ont également été empruntés. Cette étude est au centre du « Spaghetti Project », projet collaboratif impliquant les taxonomistes benthiques des différentes stations marines françaises (RESOMAR, RESeau des Stations et Observatoires MARins).Les eaux côtières françaises sont des zones étudiées depuis plusieurs siècles par les premiers taxinomistes et les écologistes benthiques. Cependant, l’étude de nombreux spécimens de vers spaghetti à l’aide de nouveaux outils, comme la microscopie électronique à balayage ou l’analyses moléculaire, a révélé l’existence de 31 espèces nouvelles pour la science.Ces espèces ont probablement « toujours » été présentes le long des côtes mais mal identifiées pendant des décennies. Plusieurs raisons peuvent expliquer ces lacunes. La première est que ces vers sont extrêmement complexes à identifier car les caractères morphologiques nécessitent des observations pointues et des outils modernes. Deuxièmement, la plupart des espèces européennes ont été décrites aux 18ème et 19ème siècles. Les standards taxonomiques de l’époque étaient très différents, avec des descriptions très brèves et des illustrations (quand elles étaient présentes) de qualité médiocre. De plus, les matériels types étaient rarement déposés dans une collection d’un muséum, et quand ils l’étaient ont malheureusement souvent été endommagés ou perdus, empêchant des comparaisons avec des spécimens nouvellement collectés. Enfin, il y a eu jusque dans les années 1980, une idée largement répandue selon laquelle les espèces de polychètes à large distribution étaient très communes. L’étude de ces espèces soi-disant cosmopolites a révélé l’existence de nombreuses espèces cryptiques dans le monde entier en général, et en France en particulier.
(09/11/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS