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, 23/06/2026)
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, 23/06/2026)
UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CESAM, CNRS
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, 23/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CAU
Gonadal transcriptome analysis of wild contaminated female European eels during artificial gonad maturation
Since the early 1980s, the population of European eels (Anguilla anguilla) has dramatically declined. Nowadays, the European eel is listed on the red list of threatened species (IUCN Red List) and is considered as critically endangered of extinction. Pollution is one of the putative causes for the collapse of this species. Among their possible effects, contaminants gradually accumulated in eels during their somatic growth phase (yellow eel stage) would be remobilized during their reproductive migration leading to potential toxic events in gonads. The aim of this study was to investigate the effects of organic and inorganic contaminants on the gonad development of wild female silver eels. Female silver eels from two sites with differing contamination levels were artificially matured. Transcriptomic analyses by means of a 1000 candidate gene cDNA microarray were performed on gonads after 11 weeks of maturation to get insight into the mechanisms of toxicity of contaminants. The transcription levels of several genes, that were associated to the gonadosomatic index (GSI), were involved in mitotic cell division but also in gametogenesis. Genes associated to contaminants were mainly involved in the mechanisms of protection against oxidative stress, in DNA repair, in the purinergic signaling pathway and in steroidogenesis, suggesting an impairment of gonad development in eels from the polluted site. This was in agreement with the fact that eels from the reference site showed a higher gonad growth in comparison to contaminated fish.
(Chemosphere. vol. 139, n° 0045-6535, pp. 303--309, 23/06/2026)
BOREA, UNICAEN, NU, MNHN, IRD, SU, CNRS, UA, IBIS, ULaval, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, µVIS X-ray Imaging Centre, UR EABX, IRSTEA, INRS, LPTC, UB, CNRS, ISM, UB, INC-CNRS, 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, 23/06/2026)
CEBC, INRA, ULR, CNRS, NINA, NINA, NINA, NILU, TOXEN, UQAM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UC
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, 23/06/2026)
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
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, 23/06/2026)
BRGM, UNIGE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Spatial and seasonal contrasts of sedimentary organic matter in floodplain lakes of the central Amazon basin
(Biogeosciences Discussions. vol. 12, n° 1810-6277, pp. 8747 - 8787, 23/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UMR ISEM, Cirad, IRD, EPHE, PSL, UM, CNRS, BOME, MNHN, UPMC, CNRS, IRD [Burkina Faso]
Differences in brain gene transcription profiles advocate for an important role of cognitive function in upstream migration and water obstacles crossing in European eel
Background: European eel is a panmictic species, whose decline has been recorded since the last 20 years. Among human-induced environmental factors of decline, the impact of water dams during species migration is questioned. The main issue of this study was to pinpoint phenotypic traits that predisposed glass eels to successful passage by water barriers. The approach of the study was individual-centred and without any a priori hypothesis on traits involved in the putative obstacles selective pressure. We analyzed the transcription level of 14,913 genes. Results: Transcriptome analysis of three tissues (brain, liver and muscle) from individuals sampled on three successive forebays separated by water obstacles indicated different gene transcription profiles in brain between the two upstream forebays. No differences in gene transcription levels were observed in liver and muscle samples among segments. A total of 26 genes were differentially transcribed in brain. These genes encode for, among others, keratins, cytokeratins, calcium binding proteins (S100 family), cofilin, calmodulin, claudin and thy-1 membrane glycoprotein. The functional analysis of these genes highlighted a putative role of cytoskeletal dynamics and synaptic plasticity in fish upstream migration. Conclusion: Synaptic connections in brain are solicited while eels are climbing the obstacles with poorly designed fishways. Successful passage by such barriers can be related to spatial learning and spatial orientation abilities when fish is out of the water.
(BMC Genomics. vol. 16, n° 1471-2164, pp. 10 p., 23/06/2026)
UR EABX, IRSTEA, Unipd, JCU, EDF R&D LNHE, EDF R&D, EDF [E.D.F.], EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Technical Note: Large overestimation of pCO2 calculated from pH and alkalinity in acidic, organic-rich freshwaters
Inland waters have been recognized as a significant source of carbon dioxide (CO2) to the atmosphere at the global scale. Fluxes of CO2 between aquatic systems and the atmosphere are calculated from the gas transfer velocity and the water–air gradient of the partial pressure of CO2 (pCO2). Currently, direct measurements of water pCO2 remain scarce in freshwaters, and most published pCO2 data are calculated from temperature, pH and total alkalinity (TA). Here, we compare calculated (pH and TA) and measured (equilibrator and headspace) water pCO2 in a large array of temperate and tropical freshwaters. The 761 data points cover a wide range of values for TA (0 to 14 200 μmol L−1), pH (3.94 to 9.17), measured pCO2 (36 to 23 000 ppmv), and dissolved organic carbon (DOC) (29 to 3970 μmol L−1). Calculated pCO2 were >10% higher than measured pCO2 in 60% of the samples (with a median overestimation of calculated pCO2 compared to measured pCO2 of 2560 ppmv) and were >100% higher in the 25% most organic-rich and acidic samples (with a median overestimation of 9080 ppmv). We suggest these large overestimations of calculated pCO2 with respect to measured pCO2 are due to the combination of two cumulative effects: (1) a more significant contribution of organic acids anions to TA in waters with low carbonate alkalinity and high DOC concentrations; (2) a lower buffering capacity of the carbonate system at low pH, which increases the sensitivity of calculated pCO2 to TA in acidic and organic-rich waters. No empirical relationship could be derived from our data set in order to correct calculated pCO2 for this bias. Owing to the widespread distribution of acidic, organic-rich freshwaters, we conclude that regional and global estimates of CO2 outgassing from freshwaters based on pH and TA data only are most likely overestimated, although the magnitude of the overestimation needs further quantitative analysis. Direct measurements of pCO2 are recommended in inland waters in general, and in particular in acidic, poorly buffered freshwaters.
(Biogeosciences. vol. 12, n° 1726-4170, pp. 67–78, 23/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ULiège, KU Leuven