Impact de la température et de l'hypoxie sur la physiologie et le comportement des larves d'esturgeon (Acipenser sturio)
European sturgeon (Acipenser sturio) is an anadromous fish which has been in sharp decline. Its last natural reproduction occurred in 1994. Because of global change, temperature have risen, frequency and severity of hypoxic events have increased. The goal of this paper is to determine the sensitivity of A. sturio early life stages to temperature and oxygen saturation. Embryo-larvae were exposed to combined temperature conditions, ranged from 12°C to 30°C, and dissolved oxygen, ranged from 30 to 90 % O2 saturation (% O2 sat). Acute and subacute effects were evaluated using embryonic and larval mortality, hatching success, malformation rate, routine metabolic rate (RMR) and swimming speed. Embryonic survival peaked at 20°C and no survival was recorded at 30°C. No hatching occurred at 50 % O2 sat or below. Malformation appeared to be minimum at 20°C, 90 % O2 sat. Maximum RMR were recorded at 20°C at 90 % O2 sat and 16°C at 70 % O2 sat. At 20°C, RMR at 70% O2 sat was lower than at 90% O2 sat. Swimming speed peaked at 16°C. A. sturio's temperature optimum is close to 20°C. Its upper tolerance limit is between 26 and 30°C and its lower tolerance limit is below 12°C. Oxygen depletion induce subacute effects at 70 % O2 sat and lethal effects at 50 % O2 sat. Current conditions in the basin are sustainable for A. sturio. Observing its sensitivity to oxygen depletion, a slight decrease would have large impact on European sturgeon survival capacity in the basin.
(pp. 70-77, 30/08/2026)
UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Impact du métolachlore sur la physiologie et le comportement de la diatomée dulçaquicole Gomphonema gracile
Les micro-algues jouent un rôle fondamental dans les écosystèmes aquatiques : elles sont à la base des réseaux trophiques et ce en raison de leur statut de producteurs primaires. Au sein des milieux aquatiques, elles peuvent ainsi être directement impactées par des molécules de type herbicide provenant des écosystèmes terrestres et retrouvées dans le milieu par des phénomènes de ruissellement, drainage, infiltration et lessivage des sols. Cependant, les descripteurs actuels (croissance, fluorescence chlorophyllienne) s’avèrent parfois peu sensibles pour détecter les impacts toxiques de molécules dont la cible n’est pas le photosystème. Dans ce contexte, cette étude a pour but de quantifier l’impact de l’herbicide métolachlore (inhibiteur des élongases) sur une espèce de diatomée dulçaquicole Gomphonema gracile Ehrenberg, mise en culture et isolée du milieu d’étude, la Leyre (principal tributaire du bassin d’Arcachon). Cet herbicide est le contaminant majoritaire du bassin versant (en termes de fréquence de quantification et de concentration). Sa toxicité est évaluée sur des paramètres physiologiques (croissance, photosynthèse, concentration en ATP) et comportementaux (mobilité). Alors que les descripteurs classiques (par exemple l’activité photosynthétique) ne permettent pas de mettre en évidence d’impact toxique du métolachlore, et ce quelle que soit la concentration testée, les descripteurs de mobilité (pourcentage de cellules mobiles, vitesse de déplacement) démontrent des impacts toxiques, pour des concentrations environnementales. Nos résultats soulignent l’importance de l’utilisation de descripteurs d’effet diversifiés, et démontrent le potentiel prometteur d’indicateurs comportementaux pour la mise en évidence de contaminations toxiques.
(pp. 22, 30/08/2026)
UR EABX, IRSTEA, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Retreat history of the East Antarctic Ice Sheet since the Last Glacial Maximum
The East Antarctic Ice Sheet (EAIS) is the largest continental ice mass on Earth, and documenting its evolution since the Last Glacial Maximum (LGM) is important for understanding its present-day and future behaviour. As part of a community effort, we review geological evidence from East Antarctica that constrains the ice sheet history throughout this period (∼30,000 years ago to present). This includes terrestrial cosmogenic nuclide dates from previously glaciated regions, 14C chronologies from glacial and post-glacial deposits onshore and on the continental shelf, and ice sheet thickness changes inferred from ice cores and continental-scale ice sheet models. We also include new 14C dates from the George V Land – Terre Adélie Coast shelf. We show that the EAIS advanced to the continental shelf margin in some parts of East Antarctica, and that the ice sheet characteristically thickened by 300–400 m near the present-day coastline at these sites. This advance was associated with the formation of low-gradient ice streams that grounded at depths of >1 km below sea level on the inner continental shelf. The Lambert/Amery system thickened by a greater amount (800 m) near its present-day grounding zone, but did not advance beyond the inner continental shelf. At other sites in coastal East Antarctica (e.g. Bunger Hills, Larsemann Hills), very little change in the ice sheet margin occurred at the LGM, perhaps because ice streams accommodated any excess ice build up, leaving adjacent, ice-free areas relatively unaffected. Evidence from nunataks indicates that the amount of ice sheet thickening diminished inland at the LGM, an observation supported by ice cores, which suggest that interior ice sheet domes were ∼100 m lower than present at this time. Ice sheet recession may have started ∼18,000 years ago in the Lambert/Amery glacial system, and by ∼14,000 years ago in Mac.Robertson Land. These early pulses of deglaciation may have been responses to abrupt sea-level rise events such as Meltwater Pulse 1a, destabilising the margins of the ice sheet. It is unlikely, however, that East Antarctica contributed more than ∼1 m of eustatic sea-level equivalent to post-glacial meltwater pulses. The majority of ice sheet recession occurred after Meltwater Pulse 1a, between ∼12,000 and ∼6000 years ago, during a period when the adjacent ocean warmed significantly. Large tracts of East Antarctica remain poorly studied, and further work is required to develop a robust understanding of the LGM ice sheet expansion, and its subsequent contraction. Further work will also allow the contribution of the EAIS to post-glacial sea-level rise, and present-day estimates of glacio-isostatic adjustment to be refined.
(Quaternary Science Reviews. vol. 100, n° 0277-3791, pp. 10-30, 30/08/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BTP, LOCEAN, IPSL, ENS-PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS
The changing Arctic and Subarctic environment: proxy- and model-based reconstructions of Holocene climate variability in the northern North Atlantic : Preface
This special issue originates from the EU FP7-Marie Curie initiative “CASE” (The Changing Arctic and Subarctic Environment),an Initial Training Network (ITN) on marine biotic indicators of recent climate changes in the high latitudes of the North Atlantic (http://caseitn.epoc.u-bordeaux1.fr/).
(Climate of the Past. vol. 10, n° 1814-9324, pp. 589-590, 30/08/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, VU, LMD, UPMC, INSU - CNRS, X, IP Paris, ENPC, CNRS, ENS-PSL, PSL
Importance, but not intensity of plant interactions relates to species diversity under the interplay of stress and disturbance
The lack of clarity on how the intensity and importance of plant interactions change under the co-occurrence of stress and disturbance strongly impedes assessing the relative importance of plant interactions for species diversity. We addressed this issue in subalpine grasslands of the French Pyrenees. A natural soil moisture gradient further experimentally stretched at both ends was used and a mowing disturbance treatment was applied at each position along the soil moisture gradient. Changes in intensity and importance of plant interactions were assessed by a neighbour removal experiment using four target ecotypes. A structural equation modelling approach was used to assess the relative impact of stress, disturbance, the intensity and importance of plant interactions on diversity at both the neighbourhood and community scales. Without mowing, changes in intensity and importance of plant interactions only diverged in the dry part of the soil moisture gradient. The intensity of plant interactions linearly shifted from competition to facilitation with increasing stress, while the importance followed a hump-shaped relationship. Species diversity components were tightly related to the importance of plant interactions only, both the neighbourhood and community scales. Mowing disturbance strongly reduced the importance of facilitation along the soil moisture gradient, and suppressed the relationship between the importance of plant interactions and diversity components. Together, our results highlight that 1) the importance is the best predictor of variations in species diversity in this subalpine herbaceous system, and 2) that fine-scale processes such as plant interactions can affect the entire plant communities. Finally, our results suggest that high level of constraints due to co-occurring stress and disturbance can inhibit the effects of plant interactions on species diversity, highlighting their potential role in regulating diversity and the maintenance/extinction of plant communities.
(Oikos. vol. 123, n° 0030-1299, pp. 777–785, 30/08/2026)
UB, BioGeCo, INRA, UB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Influence des hydrophytes envahissants sur la biogéochimie des lacs peu profonds
Influence des hydrophytes envahissants sur la biogéochimie des lacs peu profonds (influence sur les dynamiques de l'oxygène et du carbone dissous, dont le méthane).
(pp. 14, 30/08/2026)
UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
High-resolution morphobathymetric analysis and evolution of Capbreton submarine canyon head (Southeast Bay of Biscay French Atlantic Coast) over the last decade using descriptive and numerical modeling
n this study, the Capbreton canyon head, just off the coast, is investigated using high-resolution multibeam bathymetry datasets, sediment samples and numerical modeling. The HR bathymetty analysis reveals a morphological connection between the longshore trough and the head of the canyon. The analysis of recent sediment samples shows a clear correlation between the sediment of the canyon head and that of the nearshore. Hydrodynamic modeling (a coupled wave-flow model) shows that for high-energy waves, the rotational nature of surfzone circulation reverses and wave-induced currents have the potential to transport large quantities of nearshore sands toward the canyon head. All these arguments support the assumption that the canyon head captures a part of the sand transported by longshore drift. Over the 15 years of observation (1998-2013), time-lapse bathymetry shows that the floor of the canyon head and one lateral gully network experienced significant morphological reworking. In terms of hazards, despite this strong activity, the position of the canyon head and the profile of its longitudinal slope remained stable and appear as a comforting factor. However, the activity of unusual lateral erosions needs to be monitored.
(Marine Geology. vol. 351, n° 0025-3227, pp. 1-12, 30/08/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IFREMER, SHOM, BRGM
Quantitative estimate of the paleo-Agulhas leakage
The Indian-Atlantic water exchange south of Africa (Agulhas leakage) is a key component of the global ocean circulation. No quantitative estimation of the paleo-Agulhas leakage exists. We quantify the variability in interocean exchange over the past 640,000 years, using planktic foraminiferal assemblage data from two marine sediment records to define an Agulhas leakage efficiency index. We confirm the validity of our new approach with a numerical ocean model that realistically simulates the modern Agulhas leakage changes. Our results suggest that, during the past several glacial-interglacial cycles, the Agulhas leakage varied by ~10 sverdrup and more during major climatic transitions. This lends strong credence to the hypothesis that modifications in the leakage played a key role in changing the overturning circulation to full strength mode. Our results are instrumental for validating and quantifying the contribution of the Indian-Atlantic water leakage to the global climate changes.
(Geophysical Research Letters. vol. 41, n° 0094-8276, pp. 1238-1246, 30/08/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, VU, IFM-GEOMAR, GEOMAR, ICREA, ICTA, UAB
Developmental toxicity of PAH mixtures in fish early life stages. Part II: adverse effects in Japanese medaka
In aquatic environments, polycyclic aromatic hydrocarbons (PAHs) mostly occur as complex mixtures, for which risk assessment remains problematic. To better understand the effects of PAH mixture toxicity on fish early life stages, this study compared the developmental toxicity of three PAH complex mixtures. These mixtures were extracted from a PAH-contaminated sediment (Seine estuary, France) and two oils (Arabian Light and Erika). For each fraction, artificial sediment was spiked at three different environmental concentrations roughly equivalent to 0.5, 4, and 10 μg total PAH g−1 dw. Japanese medaka embryos were incubated on these PAH-spiked sediments throughout their development, right up until hatching. Several endpoints were recorded at different developmental stages, including acute endpoints, morphological abnormalities, larvae locomotion, and genotoxicity (comet and micronucleus assays). The three PAH fractions delayed hatching, induced developmental abnormalities, disrupted larvae swimming activity, and damaged DNA at environmental concentrations. Differences in toxicity levels, likely related to differences in PAH proportions, were highlighted between fractions. The Arabian Light and Erika petrogenic fractions, containing a high proportion of alkylated PAHs and low molecular weight PAHs, were more toxic to Japanese medaka early life stages than the pyrolytic fraction. This was not supported by the toxic equivalency approach, which appeared unsuitable for assessing the toxicity of the three PAH fractions to fish early life stages. This study highlights the potential risks posed by environmental mixtures of alkylated and low molecular weight PAHs to early stages of fish development.
(Environmental Science and Pollution Research. vol. 21, n° 0944-1344, pp. 13732-13743, 30/08/2026)
UB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LPGP, INRA, Biosit : Biologie - Santé - Innovation Technologique, BE, IFREMER
Réduction des micropolluants par les traitements complémentaires : procédés d'oxydation avancée, adsorption sur charbon actif (ARMISTIQ – Action A)
L’objectif de l’action A du projet ARMISTIQ est de hiérarchiser les procédés complémentaires applicables pour la réduction des substances réfractaires aux traitements conventionnels (primaires et secondaires) des eaux des station de traitement des eaux usées (STEU) domestiques. Les procédés choisis dans cette étude sont l’ozonation, l’adsorption sur charbon actif en grain et les procédés d’oxydation avancée (POA) impliquant l’ozone, le peroxyde d’hydrogène et les rayons UV. Les procédés d’osmose inverse et de nano-filtration n’ont pas été sélectionnés a priori à cause de leur surcoût élevé et de leur importante consommation d’énergie. Les traitements complémentaires ont été étudiés à l’échelle pilote avec une capacité de traitement d’effluent de 60 à 500 L/h. Un pilote de procédés d’oxydation avancée (POA) a été installé dans deux stations d’épuration avec deux traitements en amont différents: un bioréacteur à membranes et une boue activée à faible charge suivie d’un filtre à sable. Un pilote d’adsorption avec du charbon actif en grain a été testé pendant 6 mois en continu après traitement biologique à boues activées faible charge suivie d’un filtre à sable et d’ozonation pour la désinfection. Au total, 64 micropolluants ont été analysés dans les échantillons collectés avec plusieurs méthodes analytiques basées sur la spectrométrie de masse (GC/MS, GC/MS/MS, LC/MS/MS, ICP/MS). Les composés analysés médicaments, herbicides, pesticides, alkylphénols, HAP et métaux) ont été choisis en fonction de leur occurrence dans les eaux traitées en sortie de stations d’épuration et de leurs propriétés physico-chimiques. Les traitements complémentaires étudiés aux conditions d’application utilisées (ozonation, POA et adsorption sur charbon actif) ont été trouvés efficaces pour l’élimination de la plupart des micropolluants quantifiés dans cette étude, excepté les métaux. L’ajout de peroxyde d’hydrogène à l’ozone a augmenté le nombre de substances bien éliminées (R>70%), mais n’a pas permis d’augmenter le rendement d’élimination des substances réactives à l’ozone (comme les bétabloquants ou la carbamazépine). Les autres POA (ozone/H2O2 et UV/H2O2) n’ont pas permis d’augmenter le nombre de substances organiques bien éliminées par rapport à l’ozone seul. Le charbon actif en grains était toujours efficace (R>70%) au bout de 6 mois de fonctionnement 24h sur 24 pour la plupart des médicaments et les pesticides des familles urées et triazines. Les 5 technologies étudiées ont été dimensionnées à pleine échelle afin d’évaluer leurs coûts d’investissement et d’exploitation en vue d’atteindre deux niveaux d’objectifs en taux d’élimination de micropolluants pour 2 tailles de STEU différentes. Selon cette étude, la mise en place de traitements complémentaires intensifs sur une STEU de 60 000 ou de 200 000 EH entraînerait un surcoût de traitement de 1,5 à 17,6 centimes d’euros par m3 traité, selon la technologie mise en place, la liste des substances choisie et l’objectif visé. Ces résultats sont dépendants du contexte et des conditions de l’étude. Concernant l’impact environnemental, pour la STEU de capacité plus élevée, le charbon actif est plus impactant que les autres procédés sur tous les impacts évalués sauf un. On peut classer les systèmes d’oxydation avancée par ordre croissant d’impact : ozone < ozone/H2O2 < ozone/UV ~ UV/H2O2. Pour la STEU de capacité moyenne, en revanche, le charbon actif n’est plus le procédé le plus impactant excepté en ce qui concerne les impacts sur l’occupation du sol (liés notamment à la fin de vie du charbon actif en décharge). Il devient comparable aux autres solutions au niveau de l’impact environnemental.
(pp. 71, 30/08/2026)
IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR MALY, IRSTEA