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, 26/04/2026)
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, 26/04/2026)
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, 26/04/2026)
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, 26/04/2026)
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, 26/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LCE, CNRS, UFC, UBFC
Atmospheric particulate mercury in the megacity Beijing: Efficiency of mitigation measures and assessment of health effects
Atmospheric particulate mercury (HgP) was studied before, during, and after the Olympic Summer Games in Beijing, China, in August 2008 in order to investigate the efficiency of the emission control measures implemented by the Chinese Government. These source control measures comprised traffic reductions, increase in public transportation, planting of vegetation, establishment of parks, building freeze at construction sites, cleaner production techniques for industries and industry closures in Beijing and also in the surrounding areas. Strictest measures including the ;odd-even ban; to halve the vehicle volume were enforced from the 20th of July to the 20th of September 2008. The Olympic period provided the unique opportunity to investigate the efficiency of these comprehensive actions implemented in order to reduce air pollution on a large scale. Therefore, the sampling period covered summer (August, September) and winter (December and January) samples over several years from December 2005 to September 2013. Average HgP concentrations in total suspended particulates (TSP) sampled in August 2008 were 81 ± 39 pg/m3 while TSP mass concentrations were 93 ± 49 μg/m3. This equals a reduction by about 63% for TSP mass and 65% for HgP, respectively, compared to the previous two years demonstrating the short-term success of the measures. However, after the Olympic Games, HgP concentrations increased again to pre-Olympic levels in August 2009 while values in August 2010 decreased again by 30%. Moreover, winter samples, which were 2- to 11-fold higher than corresponding August values, showed decreasing concentrations over the years indicating a long-term improvement of HgP pollution in Beijing. However, regarding adverse health effects, comparisons with soil guideline values and studies from other cities highlighted that HgP concentrations in TSP remained high in Beijing despite respective control measures. Consequently, future mitigation measures need to be tailored more specifically to further reduce HgP concentrations in Beijing.
(Atmospheric Environment. vol. 124, n° 1352-2310, pp. 396-403, 26/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Palaeohydrological changes over the last 50 ky in the central Gulf of Cadiz: complex forcing mechanisms mixing multi-scale processes
New dinoflagellate cyst (dinocyst) analyses were carried out at high resolution in core MD99-2339, retrieved from a contouritic field in the central part of the Gulf of Cadiz, for the Marine Isotope Stage (MIS) 3 interval, allowing for discussion of palaeohydrological changes over the last 50 ky in the subtropical NE Atlantic Ocean. Some index dinocyst taxa, according to their (palaeo)ecological significance, shed light on significant sea-surface changes. Superimposed on the general decreasing pattern of dinocyst export to the seafloor over the last 50 ky, paralleling the general context of decreasing aeolian dust fertilization, a complex variability in dinocyst assemblages was detected at the millennial timescale. Enhanced fluvial discharges occurred during Greenland Interstadials (GIs), especially GI 1, 8 and 12, while enhanced upwelling cell dynamics were suggested during the Last Glacial Maximum and Heinrich Stadials. Finally, during the early Holocene, and more specifically during the Sapropel 1 interval (around 7-9 ka BP), we evidenced a strong decrease in dinocyst fluxes, which occurred synchronously to a strong reduction in Mediterranean Outflow Water strength and which we attributed to an advection of warm and nutrient-poor subtropical North Atlantic Central Waters. Over the last 50 ky, our study thus allows for capturing and documenting the fine tuning existing between terrestrial and marine realms in North Atlantic subtropical latitudes, in response to not only the regional climate pattern but also monsoonal forcing interfering during precession-driven Northern Hemisphere insolation maxima. This mechanism, well expressed during the Holocene, is superimposed on the pervasive role of the obliquity as a first major trigger for explaining migration of dinocyst productive centres in the NE Atlantic margin to the subtropical (temperate) latitudes during glacial (interglacial) periods.
(Biogeosciences. vol. 13, n° 1726-4170, pp. 5357-5377, 26/04/2026)
LDO, INSU - CNRS, UBO EPE, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
To boldly climb: behavioural and cognitive differences in migrating European glass eels
European eel (Anguilla anguilla) is a catadromous fish species that received substantial attention as its population has markedly declined in the last three decades. The possible causes of this decline include habitat fragmentation factors such as dams and weirs. In some cases, these obstacles are equipped with fish friendly passage devices that may select young eels according to their climbing behaviour. We tested how individual climbing tendency was related to the event of fishway passage experienced in the field and classified fish climbing profiles as climbing ‘leaders', ‘followers', ‘finishers' and ‘no climbers'. Moreover, we analysed the brain transcription level of genes related to neurogenesis and synaptic plasticity and compared it to climbing profiles.We found that fish from the upstream segments of an impounded river had a higher climbing propensity. Their behaviour was also more repeatable throughout the whole test than the obstacle-naive fish from the downstream segment. Moreover, we found that boldly climbing ‘leaders' had lower levels of transcription of synapse-related genes than the climbing ‘followers'. These differences could be related to coping styles of fish, where proactive ‘leaders' express a routine and risky behaviour, whereas reactive fish need an environmental assessment before exploratory behaviour. Our study showed that differences in climbing propensity exist in glass eels separated by water obstacles. Moreover, eels could adopt climbing different strategies according to the way they deal with environmental stress and to the cognitive abilities they possess.
(Royal Society Open Science. vol. 3, n° 2054-5703, pp. 150665, 26/04/2026)
UR EABX, IRSTEA, SETE, UT3, Comue de Toulouse, CNRS, EDF R&D STEP, EDF R&D, EDF [E.D.F.], EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Norwegian fjord sediments reveal NAO related winter temperature and precipitation changes of the past 2800 years
The North Atlantic Oscillation (NAO) is the leading mode of atmospheric circulation variability in the North Atlantic region. Associated shifts of storm tracks, precipitation and temperature patterns affect energy supply and demand, fisheries and agricultural, as well as marine and terrestrial ecological dynamics. Long-term NAO records are crucial to better understand its response to climate forcing factors, and assess predictability and shifts associated with ongoing climate change. A recent study of instrumental time series revealed NAO as main factor for a strong relation between winter temperature, precipitation and river discharge in central Norway over the past 50 years. Here we compare geochemical measurements with instrumental data and show that primary productivity recorded in central Norwegian fjord sediments is sensitive to NAO variability. This observation is used to calibrate paleoproductivity changes to a 500-year reconstruction of winter NAO (Luterbacher et al., 2001). Conditioned on a stationary relation between our climate proxy and the NAO we establish a first high resolution NAO proxy record (NAO TFJ) from marine sediments covering the past 2800 years. The NAO TFJ shows distinct co-variability with climate changes over Greenland, solar activity and Northern Hemisphere glacier dynamics as well as climatically associated paleo-demographic trends. The here presented climate record shows that fjord sediments provide crucial information for an improved understanding of the linkages between atmospheric circulation, solar and oceanic forcing factors.
(Earth and Planetary Science Letters. vol. 435, n° 0012-821X, pp. 84-93, 26/04/2026)
UiT, UiT, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Etude à haute résolution temporelle de la Terminaison I dans l’Atlantique Nord-Est : Apport des proxies basés sur les foraminifères benthiques
(26/04/2026)
LPG-ANGERS, LPG, UA, UN UFR ST, UN, INSU - CNRS, CNRS, GM, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA