Modelling analysis of tidal bore formation in convergent estuaries
(26/10/2026)
CARDAMOM, IMB, UB, Bordeaux INP, CNRS, Inria, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Influence des hydrophytes sur la biogéochimie : le cas des isoétides et des exotiques dans les lacs aquitains
Durant les dernières décennies, plusieurs études ont caractérisé les communautés de macrophytes des lacs aquitains (sud-ouest de la France). Parmi elles, les pelouses littorales amphibies à Lobelia dortmanna et Littorella uniflora, présentent un fort intérêt en termes de valeur patrimoniale et de biodiversité. Ces lacs sont également le lieu de colonisations par des plantes exotiques à caractère envahissant, dont les hydrophytes caulescentes Egeria densa et Lagarosiphon major. La présence de ces deux types de communautés aux caractéristiques biologiques et écologiques relativement éloignées, engendre des conséquences divergentes dans l’évolution du niveau trophique des eaux et l’accumulation de matières organiques dans les lacs. L’objectif principal des travaux présentés dans ce rapport est de mieux comprendre comment ces deux communautés végétales, isoétides et hydrophytes caulescentes, modifient l’environnement qu’elles colonisent, dans un contexte d’étude des processus d'eutrophisation des plans d’eau peu profonds et d’élaboration de leur gestion. Les travaux menés pendant la période 2013-2014 ont porté sur l’étude des flux de gaz et nutriments au sein d’herbiers de macrophytes, notamment le niveau d’oxygénation des eaux et les concentrations en carbone inorganique susceptibles d’être rejetées dans l’atmosphère sous forme de méthane. Le projet a consisté en des approches de modélisation et des méthodes expérimentales sur le terrain, appliquées à différentes échelles spatio-temporelles. Des incubations en chambres benthiques ont été conduites pour mesurer les flux de gaz et de nutriments ; des cycles de prélèvements de 24 heures ont été effectués dans les herbiers ; les données obtenues sur plusieurs stations ont été traitées statistiquement pour souligner des corrélations entre certains paramètres hydromorphologiques des lacs et la typologie des communautés végétales analysées. Les données obtenues ont ainsi permis de répondre à un certain nombre d’hypothèses concernant le fonctionnement écologique de deux communautés des macrophytes dans le lac de Lacanau et dans le lac de Cazaux-Sanguinet. Dans les cas du biotope à isoétides, il s’agit d’un système autotrophe où la présence de ces plantes contribue de façon importante à l’oxygénation du sédiment, à l’oxydation du méthane et la fixation du carbone. C’est donc un argument de plus pour intensifier la conservation et la protection des milieux colonisés par ces plantes. Dans le cas du biotope à hydrophytes caulescentes, il s’agit d’un système très productif qui retient une grande quantité de carbone dans les biomasses végétales. En même temps, il s’agit d’un milieu où l’accumulation progressive de biomasse constitue un risque pour l’oxygénation des eaux et pour la mobilisation de nutriments dans la colonne d’eau. Cependant, les prospections effectuées dans les lacs médocains ont montré l’absence de progression et une faible dynamique des herbiers, ceux-ci restant confinés dans les secteurs particuliers des lacs, tels que les anses, criques et les secteurs aménagés par l’homme.
(pp. 16, 26/10/2026)
UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
First isolation of a rhabdovirus from perch Perca fluviatilis in Switzerland
Perca fluviatilis is a fish species of increasing interest to the Swiss fish farming industry. In recent years, recirculation systems have been specifically set up to increase production. In one of these farms, abnormal spiral swimming associated with elevated mortalities occurred in repeated batches of imported perch shortly after stocking on several occasions. No bacterial or parasitic etiology was detected, but a virus grown in bluegill fry (BF-2) cells was identified as perch rhabdovirus. Subsequent investigations of other samples suggested a viral tropism for the central nervous system (CNS). Phylogenetic analysis of the partial N and entire G gene sequences positioned this isolate in genogroup C of the species Perch rhabdovirus, with high nucleotide and amino acid (aa) sequence identities with the DK5533 strain isolated in Denmark in 1989. Comparative studies using other closely related isolates allowed the distinction of 2 serological patterns among perch rhabdoviruses and the identification of a proline substitution by a serine in position 147 of the glycoprotein potentially involved in antigenic differentiation. Even if perch imported onto the farm tested negative by virus isolation prior to transport, they may have been the origin of this outbreak since CNS tissue was not included in the samples that were analyzed. Another possibility might be a sub-clinical infection with a viral load in resident fish too low to be detected. This study reports the first isolation of a perch rhabdovirus in Switzerland, and emphasizes the necessity of optimizing diagnostic tools that facilitate better control of the risks associated with fish translocation.
(Diseases of Aquatic Organisms. vol. 116, n° 0177-5103, pp. 93-101, 26/10/2026)
UNIBE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ANSES
Seasonal changes in stable carbon and nitrogen isotope compositions of bat guano (Guadeloupe)
Stable isotope compositions of fossil bat guano have recently been developed as a proxy for reconstructing terrestrial paleoenvironments. However, our understanding of exactly how accurately these isotope compositions reflect seasonal variations remains limited. Here, we present a study of modern guano of phytophagous bats collected monthly over a one-year period at two roosting sites in Guadeloupe. The aim is to assess the degree to which seasonal climate and environmental variations are reflected in carbon and nitrogen isotope compositions from bat guano, as well as to evaluate the potential use of guano from phytophagous bats as a paleoenvironmental record. Our results show that stable isotope compositions vary locally, suggesting that guano of phytophagous bats accurately records local environmental conditions. Additionally, stable isotope compositions reflect seasonal variations influencing bat diet that lead to modifications of up to 2‰ of the carbon isotope compositions from feces. However, these variations are not correlated solely with climate variables as there is no straightforward relationship between climate, vegetation and bat diet over a one-year period. Moreover, these seasonal variations drive one of the bat colonies to occasionally consume insects, which can be traced as a seasonal shift in %N (up to 4.5%) and carbon isotope compositions (up to 5.6‰). Seasonal changes in isotope compositions are still lower than expected variations from fossil feces, confirming the potential use of feces from phytophagous bats as a reliable paleoenvironmental proxy.
(Palaeogeography, Palaeoclimatology, Palaeoecology. vol. 440, n° 0031-0182, pp. 524-532, 26/10/2026)
PACEA, UB, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
The ocean sampling day consortium
Ocean Sampling Day was initiated by the EU-funded Micro B3 (Marine Microbial Biodiversity, Bioinformatics, Biotechnology) project to obtain a snapshot of the marine microbial biodiversity and function of the world’s oceans. It is a simultaneous global mega-sequencing campaign aiming to generate the largest standardized microbial data set in a single day. This will be achievable only through the coordinated efforts of an Ocean Sampling Day Consortium, supportive partnerships and networks between sites. This commentary outlines the establishment, function and aims of the Consortium and describes our vision for a sustainable study of marine microbial communities and their embedded functional traits.
(GigaScience. vol. 4, pp. 27, 26/10/2026)
NERC, AD2M, SBR, UPMC, CNRS, UPMC, CNRS, IOLR, AWI, HCMR, DTU, SBR, UPMC, CNRS, UCC, IRB, OFFIS, ULISBOA, ISMAR, CNR, GEOMAR, SYKE, NOAA, UiB, CIIMAR, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CINVESTAV, USC, LOMIC, OOB, UPMC, CNRS, UPMC, CNRS, UDELAR, CSIRO, SARDI, VLIZ, CEFAS, UAlg, LOV, OOVM, UPMC, INSU - CNRS, CNRS, UPMC, INSU - CNRS, CNRS, UTAS, CRIOBE, UPVD, EPHE, PSL, CNRS, UPV / EHU, UM5, USMBA, UAE, BAS, EMBL-EBI, EMBL, UBO EPE, DEÜ, Unipd, NTU, IPMA, IGS, AMU, CNRS, OGS, RUSL, USM, UiO, ICM, CSIC, MU, SZN, UNIVPM, BAS, NERC, UAF, MBL, ANL, UC Berkeley, UC
La restauration écologique comme nouveau paradigme d'aménagement ?
Bien que les politiques aménagistes aient permis d'améliorer la maîtrise globale des fleuves, elles ont également généré de nombreuses perturbations et altérations. Aujourd'hui, la restauration des cours d'eau fait l'objet de nouvelles expérimentations. Dans le sud-ouest de la France, sur le fleuve Garonne et l'estuaire de la Gironde, elles se traduisent notamment par des remises en eau des marais liées au passage de tempêtes (dynamique de dépoldérisation). Plus en amont, dans la moyenne Garonne toulousaine, les réflexions en cours concernent la réouverture de bras morts ou la création de zones d'expansion de crues. Nous proposons, de questionner l'émergence de ce nouveau paradigme, dans une perspective pluridisciplinaire, par une évaluation géohistorique, géochimique, écologique et sociologique.
(Cahiers de géographie du Québec. vol. 59, n° 0007-9766, pp. 293-314, 26/10/2026)
GEODE, UT2J, Comue de Toulouse, CNRS, UR ETBX, IRSTEA, UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GET, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS
Stratification of surface waters during the last glacial millennial climatic events: a key factor in subsurface and deep-water mass dynamics
The last glacial period was punctuated by abrupt climatic events with extrema known as Heinrich and Dansgaard–Oeschger events. These millennial events have been the subject of many paleoreconstructions and model experiments in the past decades, but yet the hydrological processes involved remain elusive. In the present work, high-resolution analyses were conducted on the 12–42 ka BP section of core MD99-2281 retrieved southwest of the Faeroe Islands, and combined with analyses conducted in two previous studies (Zumaque et al., 2012; Caulle et al., 2013). Such a multiproxy approach, coupling micropaleontological, geochemical and sedimentological analyses, allows us to track surface, subsurface, and deep hydrological processes occurring during these rapid climatic changes. Records indicate that the coldest episodes of the studied period (Greenland stadials and Heinrich stadials) were characterized by a strong stratification of surface waters. This surface stratification seems to have played a key role in the dynamics of subsurface and deep-water masses. Indeed, periods of high surface stratification are marked by a coupling of subsurface and deep circulations which sharply weaken at the beginning of stadials, while surface conditions progressively deteriorate throughout these cold episodes; conversely, periods of decreasing surface stratification (Greenland interstadials) are characterized by a coupling of surface and deep hydrological processes, with progressively milder surface conditions and gradual intensification of the deep circulation, while the vigor of the subsurface northward Atlantic flow remains constantly high. Our results also reveal different and atypical hydrological signatures during Heinrich stadials (HSs): while HS1 and HS4 exhibit a "usual" scheme with reduced overturning circulation, a relatively active North Atlantic circulation seems to have prevailed during HS2, and HS3 seems to have experienced a re-intensification of this circulation during the middle of the event. Our findings thus bring valuable information to better understand hydrological processes occurring in a key area during the abrupt climatic shifts of the last glacial period.
(Climate of the Past. vol. 11, n° 1814-9324, pp. 1507-1525, 26/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UQAM, IFREMER, LDO, INSU - CNRS, UBO EPE, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
Spatial heterogeneity of benthic biogeochemistry in two contrasted marine environments (Arcachon Bay and Bay of Biscay, SW France)
We have studied the heterogeneity of vertical profiles of biogeochemical components obtained from sediment core slicing. Sediment cores were collected in the intertidal zone of the Arcachon Bay and on the continental slope of the Bay of Biscay, at 550 and 1000 m depth. At each station of the Arcachon Bay, five 1 m-side zones were delimited at low tide. In each square, 3 cores were collected. Spatial heterogeneity on the continental slope was obtained from the study of 3 cores of multi-corer while 2 or 3 multi-corer deployments were used during the same oceanographic cruise. Similarity between profiles was determined to estimate the spatial heterogeneity at different scales. In the Arcachon Bay, results showed a spatial heterogeneity at a decimetre scale on apparently homogeneous areas. Despite the spatial variability, all the replicated profiles in Arcachon Bay sediments had similar trends, suggesting homogeneous benthic properties. However, a sampling with replicate cores handling is required for seasonal monitoring or study of biogeochemical mechanisms in coastal environments. We observe that the spatial variability on the continental margin of the Bay of Biscay is lower than in coastal environment of the Arcachon Bay. Heterogeneity is equivalent at a decimetre scale and at a hundred meters scale, which is the precision of the sampling positioning due to the drift of the boat and the tilt of the corer cable. In addition, our 10-year-long database for the Bay of Biscay showed that differences in the shape of profiles obtained in sediment cores collected at the same stations throughout this long period may not be interpreted in terms of evolution with time, because the observed variability is as high as the spatial heterogeneity.
(Estuarine, Coastal and Shelf Science, n° 0272-7714, pp. 51–65, 26/10/2026)
BIAF, UA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Programme PIREN-Seine - Phase 6 Axe 4 : « Ecologie & Ecotoxicologie » Les déterminants de la qualité écologique du milieu aquatique
Les organismes vivants dans le milieu aquatique sont soumis à de multiples pressions combinées : chimique, hydro- morphologique, thermique, trophique (matière organique, eutrophisation...), qui impactent, et éventuellement perturbent leur fonctionnement. La santé des individus qui composent la biocénose peut aussi être altérée par ces différentes pressions. S'il est possible de faire des relations causales entre une pression et une réponse biologique, l'enjeu aujourd'hui est de pouvoir prédire les conséquences sur les différentes composantes de la biocénose de l'ensemble des pressions qui interagissent. L'observation des organismes vivants, à différents niveaux d'organisation (la cellule, l'organe, l'organisme, la population, ou la communauté) est proposée depuis plusieurs années pour renseigner sur l'état de santé des organismes, des communautés (bio- indication de type DCE), sur l'état écologique global du milieu, ou sur l'impact des contaminants chimiques (biomarqueurs en écotoxicologie). Au cours de la phase 6 PIREN -Seine, nous avons étudié à la fois comment les observations faites sur la biocénose peuvent nous renseigner sur les impacts des différentes pressions, y compris la pression chimique (domaine de l'écotoxicologie), mais aussi comment la multiplicité de ces pressions (caractéristique d'un bassin versant très anthropisé comme l'est celui de la Seine), ou les modifications de ces pressions, impactent le vivant.
(pp. 172, 26/10/2026)
SEBIO, INERIS, URCA, ULH, NU, URCA, CNRS, UR HBAN, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ULB, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, LSPE - UP-S, UR MALY, IRSTEA
Climbing experience in glass eels: a cognitive task or a matter of physical capacities?
The European eel is a panmictic species, whose decline has been recorded since the last 30 years. Among human induced environmental factors of decline, the impact of water dams during species migration is questioned. Indeed, water impoundments can be a severe obstacle for young eels trying to reach the upstream freshwater zones, even if they are equipped with fish-friendly passes. The passage by such devices could be an important event shaping the outcome of the future life and life history traits of eels. We studied what phenotypic traits were associated with the event of experience of passage by water obstacles. We analyzed specific enzyme activities and/or gene transcription levels in the muscle and brain to test whether the obstacle passage is rather a physical or cognitive task.Wefound that after a long period of maintenance under homogenous conditions, transcription levels of several genes linked to synaptic plasticity, neurogenesis and thyroid activity differed among the field-experience groups. In contrast, muscle gene transcription levels or enzymatic activities did not show any differences among fish groups.We suggest that cognitive processes such as learning and memory acquisition rather than swimming-related metabolic capacities are involved in passage of water obstacles by young eels.
(Physiology & behavior. vol. 151, n° 0031-9384, pp. 448-455, 26/10/2026)
UR EABX, IRSTEA, SEEM, UT3, Comue de Toulouse, CNRS, EDB, IRD, UT3, Comue de Toulouse, CNRS, EDF [E.D.F.], EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS