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, 23/04/2026)
UNIBE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ANSES
Étude de la contamination de la masse d’eau en pesticides, comparatif entre prélèvements ponctuels et échantillonnage passif – applications à des eaux naturelles et à des effluents de zones industrielles de la région bordelaise
Cent dix-neuf pesticides ont été recherchés dans des eaux naturelles de la Jalle d’Eysines, un cours d’eau aquitain, et dans des effluents de zones industrielles bordelaises, au cours de deux campagnes de prélèvement. Les molécules ont été quantifiées à partir de prélèvements moyennés sur 24 h. En parallèle, des échantillonneurs passifs de type POCIS (Polar Organic Chemicals Integrative Sampler) ont permis d’établir un suivi qualitatif. Les profils moléculaires au sein d’un même type de masse d’eaux sont identiques, mais diffèrent entre une eau naturelle et un effluent de zone industrielle. L’approche qualitative via les POCIS a permis de quantifier des molécules non détectées lors des prélèvements moyennés, tant pour les eaux de la Jalle d’Eysines que pour celles des zones industrielles. Les échantillonneurs passifs semblent donc prometteurs pour la caractérisation de masses d’eaux de différentes origines, en ce qui concerne les pesticides dont le log KOW est compris entre un et quatre. Il est cependant nécessaire de développer la démarche PRC (Performance Reference Compounds) afin d’y ajouter une visée quantitative.
(Revue des Sciences de l'Eau / Journal of Water Science. vol. 28, n° 0992-7158, pp. 223-228, 23/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UB
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, 23/04/2026)
UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Divergent biophysical controls of aquatic CO2 and CH4 in the World's two largest rivers
Carbon emissions to the atmosphere from inland waters are globally significant and mainly occur at tropical latitudes. However, processes controlling the intensity of CO2 and CH4 emissions from tropical inland waters remain poorly understood. Here, we report a data-set of concurrent measurements of the partial pressure of CO2 (pCO2) and dissolved CH4 concentrations in the Amazon (n = 136) and the Congo (n = 280) Rivers. The pCO2 values in the Amazon mainstem were significantly higher than in the Congo, contrasting with CH4 concentrations that were higher in the Congo than in the Amazon. Large-scale patterns in pCO2 across different lowland tropical basins can be apprehended with a relatively simple statistical model related to the extent of wetlands within the basin, showing that, in addition to non-flooded vegetation, wetlands also contribute to CO2 in river channels. On the other hand, dynamics of dissolved CH4 in river channels are less straightforward to predict and are related to the way hydrology modulates the connectivity between wetlands and river channels.
(Scientific Reports. vol. 5, n° 2045-2322, pp. 15614, 23/04/2026)
ULiège, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, KU Leuven, UENF
Mercury mobilization and speciation linked to bacterial iron oxide and sulfate reduction: A column study to mimic reactive transfer in an anoxic aquifer
Mercury (Hg) mobility and speciation in subsurface aquifers is directly linked to its surrounding geochemical and microbial environment. The role of bacteria on Hg speciation (i.e., methylation, demethylation and reduction) is well documented, however little data is available on their impact on Hg mobility. The aim of this study was to test if (i) Hg mobility is due to either direct iron oxide reduction by iron reducing bacteria (IRB) or indirect iron reduction by sulfide produced by sulfate reducing bacteria (SRB), and (ii) to investigate its subsequent fate and speciation. Experiments were carried out in an original column setup combining geochemical and microbiological approaches that mimic an aquifer including an interface of iron-rich and iron depleted zones. Two identical glass columns containing iron oxides spiked with Hg(II) were submitted to (i) direct iron reduction by IRB and (ii) to indirect iron reduction by sulfides produced by SRB. Results show that in both columns Hg was leached and methylated during the height of bacterial activity. In the column where IRB are dominant, Hg methylation and leaching from the column was directly correlated to bacterial iron reduction (i.e., FeII release). In opposition, when SRB are dominant, produced sulfide induced indirect iron oxide reduction and rapid adsorption of leached Hg (or produced methylmercury) on neoformed iron sulfides (e.g., Mackinawite) or its precipitation as HgS. At the end of the SRB column experiment, when iron-oxide reduction was complete, filtered Hg and Fe concentrations increased at the outlet suggesting a leaching of Hg bound to FeS colloids that may be a dominant mechanism of Hg transport in aquifer environments. These experimental results highlight different biogeochemical mechanisms that can occur in stratified sub-surface aquifers where bacterial activities play a major role on Hg mobility and changes in speciation.
(Journal of Contaminant Hydrology. vol. 180, n° 0169-7722, pp. 56 - 68, 23/04/2026)
BRGM, UNIGE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
The region of the Strandja Sill (North Turkey) and the Messinian events
The two sides of the Strandja Sill show a highly discontinuous stratigraphic succession since the Late Oligocene. This area, together with the Sea of Marmara Basin, is usually proposed as the gateway for the Paratethyan freshwaters and organisms that constituted the Lago Mare facies in the Mediterranean Sea during the Messinian Salinity Crisis (MSC). Our investigations involving new field observations and datings, together with previous studies, suggest that the sill has possibly experienced such a connection at around 8 Ma, i.e. significantly before the crisis. The proposal of a sea-level drop of the Black Sea before 7 Ma is not supported by our data on dinoflagellate cysts. Consistency of calcareous nannofossil succession at DSDP Site 380 is reinforced, allowing to reassert that subaerial erosion impacted both the southwestern Black Sea and the central Marmara – Dardanelles area during the peak of the MSC. At that time, this region was crossed by two oppositely directed fluvial networks, further supporting the absence of a marine gateway through the Strandja Sill. It is concluded that none of the Lago Mare events recorded in the Mediterranean during the MSC were the consequence of the passage of Paratethyan waters and organisms through this area. In the Black Sea, the well-dated Messinian fluvial erosion can be followed offshore. The overlying prograding deltaic deposits attest to a fast marine reflooding after the crisis. This constitutes a comprehensive erosion-sedimentation model in an area intensively explored for hydrocarbons.
(Marine and Petroleum Geology. vol. 66, n° 0264-8172, pp. 149-164, 23/04/2026)
iSTeP, UPMC, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ITÜ, IFREMER, IPGP, INSU - CNRS, UPD7, UR, IPG Paris, CNRS, GeoEcoMar, CR2P, MNHN, UPMC, CNRS, CEREGE, IRD, INRA, AMU, CdF (institution), INSU - CNRS, CNRS, AYBE, ITÜ, Cerema, NIHWM
Pervasive multidecadal variations in productivity within the Peruvian Upwelling System over the last millennium
There is no agreement on the pluri-decadal expression of El Ni~ noeSouthern Oscillation (ENSO) in the Pacific over the last millennium. Marine records from the Peruvian margin indicate humid conditions (El Ni~ no-like mean conditions) over the Little Ice Age, while precipitation records from the eastern equatorial Pacific infer arid conditions (La Ni~ na-like mean conditions) for the same period. We here studied diatom assemblages, nitrogen isotopes, and major and minor elements at the lamination level in three laminated trigger cores located between 11 S and 15 S on the Peruvian shelf within the oxygen minimum zone (OMZ) to reconstruct precipitation and ocean productivity at the multiannual to multidecadal timescales over the last millennium. We respected the sediment structure, thus providing the first records of the mean climatic conditions at the origin of the lamination deposition, which ones represent several years. Light laminations were deposited under productive and dry conditions, indicative of La Ni~ na-like mean conditions in the system, while dark laminations were deposited under non-productive and humid conditions, representative of El Ni~ no-like mean conditions. La Ni~ na-like mean conditions were predominant during the Medieval Warm Period (MWP; 1000e600 years BP) and Current Warm Period (CWP; 150 years BP to present), while El Ni~ no-like mean conditions prevailed over the Little Ice Age (LIA; 600e150 years BP). We provide evidence for persistent multidecadal variations in productivity over the last millennium, which were disconnected from the mean climate state. Multidecadal variability has been stronger over the last 450 years concomitantly to increased variability in the NAO index. Two intervals of strong multidecadal variability were also observed over the MWP, congruent to decreased solar irradiance and increased volcanic activity.
(Quaternary Science Reviews. vol. 125, n° 0277-3791, pp. 78-90, 23/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CAU
Is the toxicity of pesticide mixtures on river biofilm accounted for solely by the major compounds identified?
Pesticides are present as a cocktail of compounds at low concentrations in water bodies. Nevertheless, studies assessing the toxic effects of pesticide mixtures at realistic environmental concentrations are still scarce. Polar Organic Chemical Integrative Sampler (POCIS) allows the concentration of several organic chemicals from large volumes of natural water [1]. This high pre-concentration of compounds makes POCIS a powerful tool to assess extract toxicity via biological testing and therefore to study the impact of realistic mixtures . PE can be used as a black box with the advantages of dealing with mixtures “as they came”; this approach gives an estimation of an integrative measure of the toxic potential of a group of compounds including unknown toxicants without using an a priori approach. With this protocol, the global toxicity of the extract is assessed although the compounds responsible for the observed toxicity are not identified. The present study aimed to characterize the effects of long-term and low-dose exposure to POCIS extracts in a context of contamination by cereal crops on a natural biofilm community and to evaluate whether the effects observed due to exposure to PE were explained by the major compounds identified in the extracts [2].
(pp. 2, 23/04/2026)
UR EABX, IRSTEA, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Herbicide toxicity on river biofilms assessed by pulse amplitude modulated (PAM) fluorometry
The use of Rapid light curves (RLCs) as a toxicity endpoint for river biofilms was examined in this studyand compared to "classical fluorescence parameters" i.e. minimal fluorescence (F0), optimal and effectivequantum yields of photosystem II (Fv/Fmand PSII). Measurements were performed after exposure tofive concentrations of diuron (from 0.3 to 33.4 g L-1), its main degradation product (DCPMU) (from1.0 to 1014 g L-1) and norflurazon (from 0.6 to 585 g L-1) with the lowest exposure concentrationscorresponding to levels regularly encountered in chronically contaminated sites. Biofilm responses wereevaluated after 1, 5, 7 and 14 days of exposure to the different toxicants.Overall, the responses of both "classical fluorescence parameters" and RLC endpoints were highly timedependent and related to the mode of action of the different compounds. Interestingly, parameters cal-culated from RLCs (ETRmaxand Ik) were useful early markers of pesticide exposure since they revealedsignificant effects of all the tested toxicants from the first day of exposure. In comparison, classicalfluorescence endpoints (F0and Fv/Fm) measured at day 1 were only affected in the DCPMU treatment.Our results demonstrated the interest of RLCs as early markers of toxicant exposure particularly whenworking with toxicants with less specific mode of action than PSII inhibitors.
(Aquatic Toxicology. vol. 165, n° 0166-445X, pp. 160-171, 23/04/2026)
UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CESAM, CNRS
Polychlorinated biphenyl exposure and corticosterone levels in seven polar seabird species
The role of polychlorinated biphenyls (PCBs) on exposure-related endocrine effects has been poorly investigated in wild birds. This is the case for stress hormones including corticosterone (CORT). Some studies have suggested that environmental exposure to PCBs and altered CORT secretion might be associated. Here we investigated the relationships between blood PCB concentrations and circulating CORT levels in seven free-ranging polar seabird species occupying different trophic positions, and hence covering a wide range of PCB exposure. Blood P7PCB concentrations (range: 61e115,632 ng/g lw) were positively associated to baseline or stress-induced CORT levels in three species and negatively associated to stress-induced CORT levels in one species. Global analysis suggests that in males, baseline CORT levels generally increase with increasing blood P7PCB concentrations, whereas stress-induced CORT levels decrease when reaching high blood P7PCB concentrations. This study suggests that the nature of the PCB-CORT relationships may depend on the level of PCB exposure.
(Environmental Pollution (1970). vol. 197, n° 0013-9327, pp. 173-180, 23/04/2026)
CEBC, INRA, ULR, CNRS, NINA, NINA, NINA, NILU, TOXEN, UQAM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UC