Étude du mercure dans le biote : détermination des concentrations de fond dans les poissons de Guyane
La Guyane présente une forte problématique liée au mercure, d’origine à la fois naturelle et anthropique (orpaillage). En application de la Directive cadre sur l’eau (DCE) en Guyane, les services de l’état en Guyane doivent mettre en place la surveillance du mercure, substance prioritaire dangereuse, dans le biote du réseau hydrographique continental. Les objectifs de cette étude de surveillance du milieu, reposent sur la détermination d’un ou plusieurs organismes sentinelles (poissons). Au cours de cette étude, plusieurs difficultés ont été rencontrées, notamment en lien avec la configuration particulière du réseau hydrographique. En effet, 20% seulement du réseau guyanais est représenté par les fleuves et 80% par les petites masses d’eau (PME), petits ruisseaux très peu étudiés. Les premiers résultats révèlent que les espèces répertoriées dans les PME sont différentes de celles présentes dans les fleuves. Ainsi, il paraît difficile de trouver indicateur commun aux fleuves et aux PME. De plus, la situation géographique de la Guyane, entraîne une biodiversité de l’ichtyofaune importante et peu connue avec un total de 416 espèces dont la répartition est différente selon les bassins versants. Dans un premier temps, un effort important a été réalisé pour constituer une base de données. Ce travail de synthèse et d’harmonisation a été effectué à partir des données existantes issues des différents programmes de recherche réalisés depuis 1990 en Guyane sur la contamination par le mercure des poissons (soit 8 projets réalisés par l’université de Bordeaux et le laboratoire HYDRECO). Cette base de données poissons a été renseignée pour de nombreux critères analysés, mesurés ou identifiés: concentration en mercure total dans le muscle, longueur standard, poids, famille, espèce, niveau trophique, localisation des stations de collecte, niveau de pressions anthropiques des stations. Les données capitalisées correspondent à la collecte de 6200 poissons pour les fleuves et de 3000 poissons pour les PME. Des traitements statistiques et géographiques ont été réalisés sur certains bassins versants bien renseignés dans la base de données. Ainsi, plusieurs espèces bioindicatrices d’une contamination en mercure des cours d’eau vont pouvoir être proposées en fonction des systèmes hydrographiques spécifiques de la Guyane (fleuve ou crique). L’identification de sites de référence reste toutefois une tâche très délicate, étant donné que l'orpaillage a été initié en Guyane depuis les années 1850, et que près de 700 tonnes de mercure ont été répandus sur l’ensemble du territoire depuis cette date. Ce mercure ancien partiellement remobilisé par l'orpaillage actuel clandestin, associé au faible nombre d’études réalisées sur les têtes de bassin versant, rend très difficile l’identification de zones indemnes de pollution. Des investigations/prélèvements complémentaires seront probablement nécessaires pour affiner les premiers résultats obtenus.
(pp. 1, 25/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR MALY, IRSTEA
Caractérisation du standard d’eau de rivière slrs-6 (nrc-cnrc) compilation interlaboratoire du silicium, des terres rares et de 21 autres éléments en trace
L’analyse des eaux nécessite, généralement, des matériaux de référence certifiés afin d’assurer la qualité des mesures. En Géosciences, il existe peu de standards d’eau de rivière naturelle ayant un nombre important d’éléments certifiés. Or, depuis plusieurs années, une dizaine de laboratoires étudient les éléments majeurs et en traces dans les solutions naturelles (groupe de travail de l’atelier du CNRS ”Isotrace”) et valident leurs mesures avec les 19 éléments certifiés de l’eau de rivière d’Ottawa SLRS produit par le NRC-CNRC. D’autres éléments non certifiés de cette eau sont régulièrement analysés par ces laboratoires à l’aide d’ICP-MS (Inductively Coupled Plasma Mass-Spectrometry) et d’ICP-OES (Inductively Coupled Plasma Optical-Emission Spectrometry). Ces travaux ont fait l’objet de deux publications sur les lots SLRS- 4 et SLRS-5. Le nouveau lot SLRS-6 est disponible depuis fin 2015 et le groupe de travail propose, dès à présent, les valeurs pour une vingtaine d’éléments en traces non certifiés par le producteur. Comme pour les lots précédents, il a été vérifié que les résultats obtenus étaient cohérents pour les éléments certifiés par le producteur. Ensuite, des valeurs moyennes et leurs incertitudes associées sont proposées pour des éléments non certifiés par NRC-CNRC tels que le silicium et une vingtaine d’éléments en traces dont les terres rares. L’ensemble des valeurs obtenues est comparé au lot SLRS-5 précédent : SLRS-6 est caractérisé par des teneurs généralement plus faibles que SLRS-5 ce qui en fait un matériau plus difficile à étudier, proches des limites de détection des techniques utilisées. Enfin, pour comprendre les biais éventuels observés dans les laboratoires, il est aussi discuté individuellement des variations pour chaque élément.
(pp. 334, 25/04/2026)
CRPG, INSU - CNRS, UL, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GR, UR, INSU - CNRS, CNRS, GET, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS
Extreme wave activity during 2013/2014 winter and morphological impacts along the Atlantic coast of Europe
Studies of coastal vulnerability due to climate change tend to focus on the consequences of sea level rise, rather than the complex coastal responses resulting from changes to the extreme wave climate. Here we investigate the 2013/2014 winter wave conditions that severely impacted the Atlantic coast of Europe and demonstrate that this winter was the most energetic along most of the Atlantic coast of Europe since at least 1948. Along exposed open-coast sites, extensive beach and dune erosion occurred due to offshore sediment transport. More sheltered sites experienced less erosion and one of the sites even experienced accretion due to beach rotation induced by alongshore sediment transport. Storm wave conditions such as were encountered during the 2013/2014 winter have the potential to dramatically change the equilibrium state (beach gradient, coastal alignment, and nearshore bar position) of beaches along the Atlantic coast of Europe.
(Geophysical Research Letters. vol. 43, n° 0094-8276, pp. 2135–2143, 25/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LETG - Brest, LETG, UNICAEN, NU, UA, EPHE, PSL, UBO EPE, UR2, CNRS, IGARUN, UN, LDO, INSU - CNRS, UBO EPE, CNRS
The Sawqirah contourite drift system in the Arabian Sea (NW Indian Ocean): A case study of interactions between margin reactivation and contouritic processes
The relationships between oceanic circulation in the Arabian Sea and Late Cenozoic climate changes, including variations in monsoon intensity at the million year time-scale, remain poorly investigated. Using multibeam and seismic data, we provide the first description of a contourite drift in the Arabian Sea, along the south-eastern Oman margin. This contourite drift is referred as the “Sawqirah Contourite Drift System”. Late Miocene reactivation of the south-eastern Oman margin resulted in the formation of a complex anticline system, which shaped the seafloor topography above which the Sawqirah Drift subsequently developed. The drift resulted from the circulation of bottom currents within the North Intermediate Indian Water. Major seismic unconformities identified within the Sawqirah Drift were tied to Ocean Drilling Program (ODP) drill holes, and allowed defining distinct episodes of drift construction. At least two of these unconformities record reorganizations of the oceanic circulation at ~ 4.5–4.8 Ma and ~ 2.4 Ma. The 4.5–4.8 Ma-old unconformity is coeval with the onset of upwelling of deep and cold waters in the Owen Basin. The 2.4 Ma-old unconformity records a major episode of Indian monsoon intensification (at the million year time scale) over the Arabian Sea, indicating strong coupling between oceanic and atmospheric circulation processes.
(Marine Geology. vol. 381, n° 0025-3227, pp. 1-16, 25/04/2026)
LGENS, INSU - CNRS, CNRS, ENS-PSL, PSL, UWA, iSTeP, UPMC, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Reconstructions of biomass burning from sediment-charcoal records to improve data-model comparisons
The location, timing, spatial extent, and frequency of wildfires are changing rapidly in many parts of the world, producing substantial impacts on ecosystems, people, and potentially climate. Paleofire records based on charcoal accumulation in sediments enable modern changes in biomass burning to be considered in their long-term context. Paleofire records also provide insights into the causes and impacts of past wildfires and emissions when analyzed in conjunction with other paleoenvironmental data and with fire models. Here we present new 1000-year and 22 000-year trends and gridded biomass burning reconstructions based on the Global Charcoal Database version 3 (GCDv3), which includes 736 charcoal records (57 more than in version 2). The new gridded reconstructions reveal the spatial patterns underlying the temporal trends in the data, allowing insights into likely controls on biomass burning at regional to global scales. In the most recent few decades, biomass burning has sharply increased in both hemispheres but especially in the north, where charcoal fluxes are now higher than at any other time during the past 22 000 years. We also discuss methodological issues relevant to data-model comparisons and identify areas for future research. Spatially gridded versions of the global data set from GCDv3 are provided to facilitate comparison with and validation of global fire simulations.
(Biogeosciences. vol. 13, n° 1726-4170, pp. 3225-3244, 25/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LCE, CNRS, UFC, UBFC
Study of benthic foraminiferal faunas along the French Mediterranean coasts: a new biotic index in the EU Water Framework Directive
(25/04/2026)
LPG-ANGERS, LPG, UA, UN UFR ST, UN, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Gene transcription profiling in wild and laboratory-exposed eels: Effect of captivity and in situ chronic exposure to pollution
Aquatic ecosystems are subjected to a variety ofman-induced stressors but also vary spatially and temporally due to variation in natural factors. In such complex environments, it remains difficult to detect, dissociate and evaluate the effects of contaminants in wild organisms. In this context, the aim of this study was to test whether the hepatic transcriptome profile of fish may be used to detect in situ exposure to a particular contaminant. Transcriptomic profiles from laboratory-exposed and wild eels sampled along a contamination gradient were compared. During laboratory experiments, fish were exposed during 45 days to different pollutants (Hg, PCBs, OCPs or Cd) or natural factors (temperature, salinity or lowfood supply) at levels close to those found in the sampling sites. A strong differencewas observed between the transcriptomic profiles obtained fromwild and laboratory-exposed animals (whatever the sites or experimental conditions), Suggesting a general stress induced by captivity in the laboratory. Among the biological functions that were up-regulated in laboratory eels in comparison to wild eels, histonemodification was the most represented. This finding suggests that laboratory conditions could affect the epigenome of fish and thus modulate the transcriptional responses developed by fish in response to pollutant exposure. Among experimental conditions, only the transcription profiles of laboratory animals exposed to cold temperature were correlated with those obtained from wild fish, and more significantly with fish from contaminated sites. Common regulated genes were mainly involved in cell differentiation and liver.
(Science of the Total Environment. vol. 571, n° 0048-9697, pp. 92-102, 25/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IRSTEA, ULaval, UR EABX, IRSTEA
Indicator-based assessment of marine biological diversity – lessons from 10 case studies across the European Seas
The Marine Strategy Framework Directive requires the environmental status of European marine waters to be assessed using biodiversity as one out of 11 descriptors, but the complexity of marine biodiversity and its large span across latitudinal and salinity gradients have been a challenge to the scientific community aiming to produce approaches for integrating information from a broad range of indicators. The Nested Environmental status Assessment Tool (NEAT), developed for the integrated assessment of the status of marine waters, was applied to ten marine ecosystems to test its applicability and compare biodiversity assessments across the four European regional seas. We evaluate the assessment results as well as the assessment designs of the ten cases, and how the assessment design, particularly the choices made regarding the area and indicator selection, affected the results. The results show that only 2 out of the 10 case study areas show more than 50 % probability of being in good status in respect of biodiversity. No strong pattern among the ecosystem components across the case study areas could be detected, but marine mammals, birds, and benthic vegetation indicators tended to indicate poor status while zooplankton indicators indicated good status when included into the assessment. The analysis shows that the assessment design, including the selection of indicators, their target values, geographical resolution and habitats to be assessed, has potentially a high impact on the result, and the assessment structure needs to be understood in order to make an informed assessment. Moreover, recommendations are provided for the best practice of using NEAT for marine status assessments.
(Frontiers in Marine Science. vol. 3, n° 2296-7745, pp. 159, 25/04/2026)
SYKE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, NIVA, NIOZ
An interlaboratory study on passive sampling of emerging water pollutants
An inter-laboratory study was organised for the monitoring of emerging aquatic pollutants (pharmaceuticals, pesticides, steroids, brominated diphenyl ethers and others) using passive samplers. Thirty laboratories participated in the sampler comparison exercise. Various samplers designs were exposed at a single sampling site to treated waste water. The organisers deployed in parallel multiple samplers of a single type, which were distributed for evaluation of the contribution of the different analytical procédures to the data variability. Between laboratory variation of results from passive samplers was about factor 5 larger than within laboratory variability. Similar results obtained for different passive samplers analysed by individual laboratories and also low within laboratory variability indicate that the passive sampling process is causing less variability than the analysis. Concentrations in composite water samples were within the range obtained by passive samplers. In future a significant improvement of analytical precision and calibration of adsorption based passive samplers is needed.
(Trends in Analytical Chemistry. vol. 76, n° 0165-9936, pp. 153-165, 25/04/2026)
MU / MUNI, IRSTEA, IRSTEA, JRC, UR EABX, IRSTEA, UR MALY, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IRSTEA, EAWAG, IRSTEA, IRSTEA, IRSTEA, IRSTEA
Seasonal and long-term changes in elemental concentrations and ratios of marine particulate organic matter
What is the temporal variability of the elemental stoichiometry of marine microbial communities across ocean regions? To answer this question, we present an analysis of environmental conditions, particulate organic carbon, nitrogen, and phosphorus concentrations and their ratios across 20 time series (3-25 years duration) representing estuarine, coastal, and open ocean environments. The majority of stations showed significant seasonal oscillations in particulate organic elemental concentrations and ratios. However, shorter-term changes contributed most to overall variance in particulate organic matter concentrations and ratios. We found a correlation between the seasonal oscillations of environmental conditions and elemental ratios at many coastal but not open ocean and estuarine stations. C:N peaked near the seasonal temperature minimum and nutrient maximum, but some stations showed other seasonal links. C:N ratios declined with time over the respective observation periods at all open ocean and estuarine stations as well as at five coastal station but increased at the nine other coastal stations. C:P (but not N:P) declined slightly at Bermuda Atlantic Time-series Study but showed large significant increases at Hawaii Ocean Time-series and Arendal stations. The relationships between long-term changes in environmental conditions and particulate organic matter concentrations or ratios were ambiguous, but interactions between changes in temperature and nutrient availability were important. Overall, our analysis demonstrates significant changes in elemental ratios at long-term and seasonal time scales across regions, but the underlying mechanisms are currently unclear. Thus, we need to better understand the detailed mechanisms driving the elemental composition of marine microbial ecosystems in order to predict how oceans will respond to environmental changes.
(Global Biogeochemical Cycles. vol. 30, n° 0886-6236, pp. 1699-1711, 25/04/2026)
UPMC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS