Do benthic foraminifera and their geochemical signature from the Celtic margin differentiate the effects of European and Laurentide Ice Sheets meltwaters on the AMOC across Termination 1?
(27/04/2026)
LPG-ANGERS, LPG, UA, UN UFR ST, UN, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
Holocene sea ice variability driven by wind and polynya efficiency in the Ross Sea
The causes of the recent increase in Antarctic sea ice extent, characterised by large regional contrasts and decadal variations, remain unclear. In the Ross Sea, where such a sea ice increase is reported, 50% of the sea ice is produced within wind-sustained latent-heat polynyas. Combining information from marine diatom records and sea salt sodium and water isotope ice core records, we here document contrasting patterns in sea ice variations between coastal and open sea areas in Western Ross Sea over the current interglacial period. Since about 3600 years before present, an increase in the efficiency of regional latent-heat polynyas resulted in more coastal sea ice, while sea ice extent decreased overall. These past changes coincide with remarkable optima or minima in the abundances of penguins, silverfish and seal remains, confirming the high sensitivity of marine ecosystems to environmental and especially coastal sea ice conditions.
(Nature Communications. vol. 8, n° 2041-1723, pp. 1334, 27/04/2026)
UNISI, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GLACCIOS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, UniPi, UniPi, ENEA, UniFI, ENEA
Main Ecological Features of Benthic Macrofauna in Mediterranean and Atlantic Intertidal Eelgrass Beds: A Comparative Study
The present study compares the intertidal eelgrass macrofauna in two geographically and ecologically disparate localities (central Mediterranean and eastern Atlantic). Both coastal ecosystems are developed on extensive large mudflats with eelgrass beds, hosting a great diversity of water birds and providing important socioeconomic assets. These two distinct and distant geographical ecosystems are affected by numerous anthropogenic pressures. By reflecting the response of the structure and functioning of benthic communities to climate change, the two eelgrass ecosystems provide a natural laboratory to investigate global warming. The macrobenthic fauna community of Zostera (Zosterella) noltei eelgrass beds was studied by sampling 34 stations in the Kneiss Islands and 48 stations in Arcachon Bay. A total of 148 species are identified in the Kneiss islands and 117 species in Arcachon Bay, but only 23 species are common to both ecosystems. Diversity, abundance and community structure are significantly different between the two study areas, which could be explained by differences between Mediterranean and Atlantic climatic conditions and by anthropic factors (e.g. fishing pressure, pollution, nutrient inputs) affecting each ecosystem. Multidimensional scaling (n-MDS) analysis identifies two distinct geographical station groups on the basis of species and family-level abundance. On the contrary, three assemblages are identified on the basis of trophic groups distributed between the separate ecosystems. In terms of ecological quality status, the Kneiss site appears to have a good ecological condition and hosts a variety of sensitive species. On the other hand, biotic indices indicate that the Arcachon site is moderately perturbed and that the benthic communities are unbalanced. It is expected that the present-day functioning of the Kneiss Islands ecosystem will become typical of the situation in Arcachon Bay in several decades time, with the development of warmer and drier conditions.
(Journal of Marine Biology & Oceanography. vol. 6, pp. 100174, 27/04/2026)
FSS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS
Fragilariopsis kerguelensis size variability from the Indian subtropical Southern Ocean over the last 42 000 years
In the open Southern Ocean (SO), both modern and past size changes of the diatom Fragilariopsis kerguelensis appear to be strongly controlled by iron availability. Conversely, sea surface temperatures (SST) and sea ice seasonal dynamics take over in the seasonal sea-ice zone where iron is not limiting. No information exists on F. kerguelensis biometry from the subtropical SO, on the other extreme of the thermal and nutrient gradients. We present here new data on mean valve area of F. kerguelensis (FkergArea) from a sediment core covering the last ~ 42 cal kyrs from the southern Subtropical Front (SSTF) of the Indian sector of the SO, where iron and silica stocks are thought to have been consistently low over this period. Our results suggest that larger F. kerguelensis valves occurred during the Last Glacial period, and declined during the Holocene period. These findings indicate that more favourable SST, within the F. kerguelensis ecological range, during the Last Glacial period may have enabled F. kerguelensis to make better use of the low silica stocks prevailing in the subtropical zone leading to larger valves. Conversely, declining FkergArea during the deglacial and the Holocene periods may have been a result of higher SST which hampered the utilization of silica.
(Antarctic Science. vol. 29, n° 0954-1020, pp. 139-146, 27/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Proposition de concentrations de références en mercure dans l'ichtyofaune de Guyane
La pollution des écosystèmes aquatiques par le mercure est un problème majeur de la Guyane française, soumis à l'orpaillage illégal intensif depuis de nombreuses années. Au niveau européen, une norme de qualité environnementale pour le biote (NQEbiote : 0,02 mg Hg.kg-1 poids frais) a été définie dans le cadre de la directive cadre sur l'eau (DCE). Ce rapport a pour but d'aider à la mise en place de la NQEbiote en Guyane française par : 1/ si possible, l'identification de sites non pollués par le mercure d'origine anthropique ; 2/ la détermination de concentrations de références en mercure pour l'ichtyofaune associées à ces sites ; 3/ l'identification d'espèces de poissons sentinelles potentielles de cette pollution. Une base de données d'environ 9000 poissons (3000 pour les criques et 6000 pour les fleuves) a été constituée à partir des résultats des programmes de recherche et de surveillance depuis 1993. Les concentrations en mercure mesurées dans le muscle de ces poissons se révèlent presque toujours supérieures à la NQEbiote (100% pour les criques et 89 % pour les fleuves). Peu de zones de références potentielles ont été identifiées sur plus de 200 stations échantillonnées. Ainsi pour les criques, 7 stations réparties sur 6 bassins versants différents présentent des concentrations significativement plus faibles que les autres stations. Sur les fleuves, seulement 2 zones (groupe de stations) ont été identifiées comme références potentielles sur le bassin versant de l'Oyapock. L'analyse de ces données a permis de proposer plusieurs espèces sentinelles, c'est à dire intégratives d'une contamination mercurielle. Pour les criques, il s'agit de Copella carsevennensis, Pyrrhulina filamentosa, Jupiaba (abramoides et keithi), Moenkhausia oligolepis, Pimelodella (cristata, geryi et macturki), Gymnotus carapo et Sternopygus macrurus. Pour les fleuves, 3 genres et espèces ont été retenus : Ageneiosus inermis, Acestrorhynchus (falcatus et microlepis) et Hoplias aïmara. Des recommandations opérationnelles sont proposées pour le suivi de la DCE telles que : i/ échantillonner moins de stations (en privilégiant celles suivies par l'OMS), ii/ espacer la fréquence des suivis (tous les 2 ans), iii/ mais, en contrepartie, augmenter l'effort de pêche sur les espèces sentinelles proposées.
(pp. 78, 27/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR MALY, IRSTEA
How does climate change make fish late for dinner?
Imagine you are a young and hungry fish looking for food in an estuary (the part of a river where it meets the ocean). You need to grow big and strong before you migrate to the ocean, and depend on tiny floating creatures (plankton) for food. However, the occurrence of these tiny creatures in the estuary varies seasonally. Lucky for you, nature has synchronized both your time in the estuary and that of your prey, and you survive. This synchronization depends on many different factors, among them the temperature of the water. Now imagine someone turning up the heat (like we humans are doing by changing the climate). Could the rising water temperatures mess up the timing for you, the predator, and your prey? To answer this question we looked at climate related changes in the synchronization of predator and prey in the biggest estuary in Western Europe. And indeed, we found signs of temporal mismatches in its aquatic food web. We fear that the observed changes can put this important ecosystem and its role as a big fish nursery at risk.
(Environmental Science Journal for Teens, pp. 5, 27/04/2026)
UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Utilisation des échantillonneurs passifs pour évaluer la contamination des écosystèmes aquatiques par les produits phytosanitaires - Application à un bassin versant viticole
L'échantillonnage passif représente une alternative aux prélèvements ponctuels pour la détermination de la contamination en pesticides. Les échantillonneurs présentent l'avantage d'intégrer la contamination du milieu pendant la période d'exposition de l'outil et permettent un abaissement des limites de détection grâce à l'accumulation des substances. Parmi les outils existants, les échantillonneurs passifs intégratifs pour les contaminants organiques polaires (POCIS : Polar Organic Chemical Integrative Samplers) ont été utilisés avec succès pour évaluer la contamination des hydrosystèmes en contexte agricole [1]. Ces POCIS peuvent être adaptés pour permettre la surveillance de milieux exigus ou de milieux à écoulements épisodiques tels que les fossés agricoles. Ces adaptations consistent à modifier les dimensions de l'outil, la surface membranaire, la quantité de phase ou encore la porosité des membranes pour influencer la quantité de substances accumulées [2]. Le projet de recherche multidisciplinaire PhytoCOTE étudie l'usage des pesticides dans les agrosystèmes, leurs transferts dans les écosystèmes connexes, leur bioaccumulation, et leur toxicité potentielle chez les organismes aquatiques. Le site d'étude est localisé dans une zone d'exploitation viticole sur la rive droite de l'estuaire de la Gironde. Dans ce cadre, un suivi annuel de la variabilité spatio-temporelle des concentrations en pesticides a été mis en place. Le suivi des cours d'eau permanents (ordre 1, 2 et 3) repose sur le déploiement de POCIS classiques à une fréquence mensuelle. Le suivi des fossés repose sur le déploiement de POCIS adaptés (miniPOCIS et POCIS-T) pendant la période d'application des pesticides. Parallèlement, des prélèvements d'eau sont réalisés à une fréquence mensuelle ou bimensuelle. Le suivi de la contamination est basé sur une liste de plus de 200 substances parmi lesquels les pesticides utilisés sur le bassin versant (54 substances). Différentes techniques d'extraction et d'analyse par LC-MS/MS et GC-MS/MS ont été développées pour permettre la quantification de ces composés.
(pp. 2, 27/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR ETBX, IRSTEA
Transient Surf Zone Circulation Induced by Rhythmic Swash Zone at a Reflective Beach
The influence of cuspate swash dynamics on transient surf zone circulation is investigated using both field observation at the low-tide terraced Grand Popo beach and wave-phase resolving numerical simulations. The ability of the model to describing low-tide terrace beach hydrodynamic is tested, and the model is further applied to investigate the role of wave reflection over a rhythmic swash zone pattern on surf zone wave and current. In the numerical simulations, these mechanisms drive higher surf zone irregularities with beach cusps than for an alongshore-uniform swash zone morphology. Rhythmic swash-based reflection generates a standing wave pattern visible in current and wave fields. The positive feedback of reflection on incoming waves drives occasional strong flash rips occurring with different frequencies than individual waves or groups. The so called breakpoint-swash system is thought to pulse with its own temporal characteristics, which depends on wave forcing but also on surf zone terrace and cuspate morphology.
(27/04/2026)
LEGOS, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, BRGM, FLUMINANCE, IRMAR, UR, INSA Rennes, INSA, ENS Rennes, UR2, CNRS, Institut Agro, IRSTEA, Inria, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CNRS, UB
On the robustness of near term climate predictability regarding initial state uncertainties
(Climate Dynamics. vol. 48, n° 0930-7575, pp. 353 - 366, 27/04/2026)
LOCEAN, IPSL, ENS-PSL, PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, IP Paris, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, NOC, CEP, UNIBE, OCCR, UNIBE, PARVATI, LOCEAN, IPSL, ENS-PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Shoreline resilience to individual storms and storm clusters on a meso-macrotidal barred beach
This study investigates the impact of individual storms and storm clusters on shoreline recovery for the meso-to macrotidal, barred Biscarrosse beach in SW France, using 6 years of daily video observations. While the study area experienced 60 storms during the 6-year study period, only 36 storms were analysed due to gaps in the video data. Based on the 36 individual storms and 13 storm clusters analysed, our results show that clustering impact is cumulatively weak and shoreline retreat is governed by the first storms in clusters, while the impact of subsequent events is less pronounced. The average post-storm beach recovery period at this site is 9 days, consistent with observations at other beaches. Apart from the dominant effect of present storm conditions, shoreline dynamics are also significantly affected by previous storm influence, while recovery is strongly modulated by tidal range and the bar location. Our results reveal that not only is the storm energy important but also the frequency of recurrence (storms result in greater retreat when time intervals between them are longer), which suggests an interaction between short storm events and longer-term evolution.
(Geomorphology. vol. 290, n° 0169-555X, pp. 265-276, 27/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEGOS, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS