An assessment of European and Atlantic sturgeons’ paleoniches during the Holocene
The use of species distribution models (SDMs) in paleoecology enhances its contribution to ecology and conservation biology, such as estimating climate change impacts and informing conservation efforts. Acipenser sturio and A. oxyrinchus are closely related sturgeon species currently arranged in two disjunct distributions across the Atlantic Ocean. However, paleogenetic findings highlighted that both species were present in European waters over at least five millennia. Their joint European history during the Holocene period might have been driven by the thermal hypothesis, with A. oxyrinchus being a cooler-water species than A. sturio . Given their current poor state of conservation, quantifying their environmental preferences at a time when the two species were more abundant could help shape future conservation/restoration measures. Paleo-species distribution models were built for each species based on paleoclimate variables and archeozoological remains, most of which were genetically identified at the species level. Response curves for air temperature and precipitation were then applied to estimate relative continental paleohabitat suitability (HSI) in watersheds across four regions (i.e., the Baltic Sea, the Northern Seas, the South European Atlantic shelf, and the Mediterranean Sea) throughout the Holocene. The estimated niches confirmed the thermal sensitivity difference between the two species, with A. oxyrinchus having a narrower thermal range towards colder annual temperatures. Comparing HSI suitability between the two species, the four regions were globally all suitable for A. sturio but not for A. oxyrinchus , which showed much greater variability. Catchments with outlets to the Mediterranean Sea and the South European Atlantic shelf were mainly suitable for A. sturio . In contrast, those with an outlet in the Baltic Sea were slightly more suitable for A. oxyrinchus than for A. sturio . Catchments with outlets to the Northern Seas showed comparable suitability for both species. This superposition in near-past suitable habitats implied that the two species can potentially exist under the same environmental conditions and as such suggested future risks of biotic interactions which should be further acknowledged in potential stocking practices.
(Frontiers in Ecology and Evolution. vol. 14, n° 2296-701X, 16/03/2026)
UR EABX, INRAE, BioArch, MNHN, CNRS, CRAVO, MNHN, CReAAH, UM, UR, UR2, CNRS, MC, Nantes Univ - UFR HHAA, Nantes Univ, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UB, MIZ PAN = MIZ PAS
Explosive volcaniclastic sedimentation in the Comoros Archipelago over the past 1.5 Myr (western Indian Ocean)
A new chronostratigraphic framework for deep-sea volcaniclastic sedimentation in the Somali Basin provides key constraints on the timing, magnitude, and recurrence of explosive volcanism associated with the Comoros Archipelago over the past ~1.5 Myr. Multibeam bathymetry, high-resolution seismic reflection data, and seven sediment cores recovered north of the archipelago are combined to establish basin-scale correlations of volcaniclastic turbidites. Temporal control is achieved through tuning of oxygen isotope stratigraphies.Seismic–core correlations reveal multiple regionally extensive event deposits, with individual layers covering minimum areas ranging from ~20 km² to more than 130,000 km². Petrographic observations and geochemical analyses show that the turbidites are dominated by basaltic to trachybasaltic glass fragments (sideromelane and tachylite), consistent with a Comorian volcanic provenance. The large volumes, widespread dispersal, and sharp basal contacts of these deposits support direct syn-eruptive emplacement by eruption-fed sediment gravity flows, rather than post-eruptive remobilization. Such deposits require highly energetic explosive activity, consistent with Surtseyan to (sub-)Plinian eruptions capable of generating large quantities of pyroclastic material and transporting it hundreds of kilometers into the deep basin.The resulting chronostratigraphy documents recurrent phases of intensified volcaniclastic sedimentation at ~1.63–1.35 Ma, ~1.03–0.72 Ma, and ~0.40–0.13 Ma, indicating episodic but long-lived explosive volcanism in the Comoros region during the Quaternary. These findings highlight the Comoros Archipelago as a major center of explosive basaltic volcanism in the western Indian Ocean and underscore the importance of deep-marine sedimentary records for assessing the frequency, magnitude, and hazard potential of large-scale submarine eruptions.
(14/03/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LGSR, UR, IPG Paris, IPGP - UMR_7154, INSU - CNRS, IGN, UR, IPG Paris, CNRS, UPCité, OPGC, INSU - CNRS, CNRS, UCA, BRGM, SHOM, CEREGE, IRD, AMU, CdF (institution), INSU - CNRS, CNRS, INRAE, ITES, ENGEES, UNISTRA, INSU - CNRS, CNRS
Challenges of monitoring contaminants in soils: insights from the French experience
Soil pollution is one of the major threats upon soil health. However, the main knowledge of the extent and the diversity of contaminants in soils has been obtained during the last years and there is still a big knowledge gap. If the most campaigns were focusing on trace elements or well-known organic contaminants such as PAH or PCB, the bigger challenge lies ahead when looking at emerging contaminants such as PFAS, pesticides or microplastics. The recent EU directive on soil monitoring might be an opportunity to tackle these knowledge gaps about diffuse soil contamination and the risk they may pose along with a better distribution of the knowledge across countries. This presentation aims to showcase what has been done the last 20 years in France regarding soil contaminants, and specifically since 2020 about trace elements, organic contaminants but also pesticides and microplastics and what are the challenges going-on. Major results and lessons from these monitoring in France could be used when building the European monitoring to ensure the most efficient choices to advice and answer policy questions and enlighten decisions regarding contaminants.
(14/03/2026)
Info&Sols, INRAE, InfoSol, INRAE, LPTC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, AFNOR, GeePs, SU, CNRS
A second track of the Réunion hotspot in the Mascarene Basin
Hotspots are generally interpreted as the surface expression of lithospheric plates moving over mantle plumes, progressively forming volcanic chains aligned with plate motion. However, it is increasingly recognized that hotspots—such as Hawaii, Samoa, and Tristan–Gough— can exhibit two volcanic lineaments that are not necessarily parallel and display distinct geochemical characteristics. Here we report the discovery of a previously unrecognized volcanic chain related to the Réunion hotspot in the Mascarene Basin (western Indian Ocean), which we term the Mascarene Chain (MASC). This chain extends from the Seychelles across the seafloor through a series of seamounts and records a southward progression of volcanism from ca. 67 to 6 Ma. This age progression is constrained by multi-technique geochronology (⁴⁰Ar/³⁹Ar on biotite; U–Pb on zircon; (U–Th)/He on zircon and apatite) performed on dredged volcanic samples. Petrology, whole-rock major and trace elements and Sr–Nd–Pb isotopes, as well as zircon trace elements and δ¹⁸O–Hf isotopes, indicate that these volcanoes formed from extremely low (<1%) degrees of partial melting of a fertile, metasomatized mantle source with a clear enriched-mantle affinity, distinct from the Réunion plume signature. The MASC is synchronous with the main Réunion hotspot track, from the Deccan Traps (67–65 Ma) to Réunion Island (5–0 Ma), and converges toward the current apex of the Réunion plume. The chain also lies along the boundary of an uplifted region in the Mascarene Basin, interpreted as resulting from plume-related buoyancy forces. We therefore propose that the MASC represents a secondary track of the Réunion hotspot, generated by the indirect action of the plume uplifting the Mascarene lithosphere. The progressive convergence of volcanism is consistent with a decreasing radius of influence as the plume waned. Our results further suggest that secondary hotspot tracks are generated by plume-induced upper-mantle melting, rather than by compositional heterogeneities within the plume source.
(13/03/2026)
LGSR, UR, IPG Paris, ITES, ENGEES, UNISTRA, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CEREGE, IRD, AMU, CdF (institution), INSU - CNRS, CNRS, INRAE, NMT, NMC, GEOPS, INSU - CNRS, CNRS, IPGP - UMR_7154, INSU - CNRS, IGN, UR, IPG Paris, CNRS, UPCité, iSTeP, INSU - CNRS, SU, CNRS, CY, LMV, IRD, INSU - CNRS, CNRS, UCA
Observations and Modelling of Coastal Dune Dynamics Along the Gironde Coast, France
Considered as reservoirs of biodiversity, coastal dunes also represent natural barrier against coastal flooding and large source of sediment to mitigate coastal erosion. Dynamics of coastal dunes are forced and controlled by marine, aeolian and biological processes. A better understanding of the interactions between all these processes based on field observations or numerical modelling is crucial to define management strategies that aim to develop the resilience of coastal dune against sea level rise. The analysis of multi-annual topographic data collected along the Gironde coast in SW France show a strong landward migration of the coastal dunes caused by strong wind events and a decrease in vegetation cover. The same data were also used to calibrate and validate a numerical model, AeoLiS, that simulated Aeolian sediment transport. This model showed good performance to reproduce the landward migration of non-vegetated dune.
(. vol. 41, pp. 141-146, 05/03/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM
Holocene climatic changes in the Kerguelen archipelago (South Indian Ocean) based on marine and lacustrine palaeoclimatic archives
Climatic variability in the Southern Hemisphere is largely controlled by the latitudinal position of the Southern Hemisphere Westerly Winds (SHW), whose migration influences precipitation, temperature, and Antarctic upwelling. This study presents the results of analyses of two lacustrine sediment cores from Lake Armor, located on the subantarctic Kerguelen Islands (49 • 15′S, 69 • 10′E), within the SHW belt. Lipid biomarkers (Glycerol Dialkyl Glycerol Tetraethers, n-alkanes, and their hydrogen isotopes) were used to reconstruct mean annual air temperature above freezing (MAF) and humidity conditions. These records are compared with a high-resolution diatom-based summer sea surface temperature (SST) reconstruction from marine core MD11-3353, situated 150 km southwest of Lake Armor. In the late glacial and Early Holocene, our results reveal a period of warm air temperature, comparable to current values and very warm sea surface temperature, 5°C above the current values. Around 9000 cal a BP, an abrupt transition occurred, marked by a cooling of 5°C in SST and 1.5°C in MAF, interpreted as a northward migration of the SHW and associated oceanic fronts. The Mid-to-Late Holocene period is characterized by pronounced MAF variability, including a notably warm interval between 3000 and 2000 cal a BP, when n-alkane dD suggests the prevalence of wetter conditions. Since ~250 cal a BP, a southward migration of the SHW has produced a 2.5°C rise in MAF. Our findings are overall consistent with previous studies from the Indian Ocean, but permit us to go a step further as by comparing SSTs and air temperatures. This suggests that SST is not a reliable predictor of air temperature on the Kerguelen Islands, particularly during the Early Holocene. We hence argue that Kerguelen air temperature is predominantly controlled by the position of westerly winds, as an indicator of reorganisations in air mass trajectories.
(Quaternary Science Reviews. vol. 375, n° 0277-3791, pp. 109753, 01/03/2026)
EDYTEM, USMB [Université de Savoie] [Université de Chambéry], CNRS, Fédération OSUG, LGL-TPE, ENS de Lyon, UCBL, INSU - CNRS, UJM, UJM EPE, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, MIO, IRD, AMU, INSU - CNRS, UTLN, CNRS, LOCEAN-VOG, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, LOCEAN-VALCO, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, UiB, IP, INSU - CNRS, CNRS, JAMSTEC, INEE-CNRS, CNRS, INSU - CNRS
Origin and evolution of giant comet marks along the North Atlantic Deep-Water flow on the Demerara plateau
The Demerara Plateau, located in the equatorial Atlantic, is particularly well-suited for recording the activity of the Deep Western Boundary Current (DWBC), which transports North Atlantic Deep Water (NADW) southward into the Atlantic basin. This current, active between 1500 and 3500 m depth, constitutes the deep part of the global thermohaline circulation and plays a crucial role in climate regulation. The Demerara Plateau is remarkable for the abundance and wide distribution of comet mark-type sedimentary structures, which can reach several kilometres in length. These hydrodynamic bedforms, interpreted as erosional features associated with strong bottom currents, are currently used as proxies for deep currents velocities, with minimum formation thresholds estimated between 0.60 and 0.75 m/s according to the literature (Rebesco et al., 2014; Werner et al., 1980). The DIADEM (Dive At DEMerara) oceanographic cruise (Basile and Loncke, 2023) enabled detailed investigation of one such structure using a combination of complementary tools with the aim of better understanding their functioning and evolution with in-situ observation, physical records, and sampling. Those new data were also combined with formerly acquired high-resolution seismic data, allowing a new vision of these bedforms their formation, and their evolution over time. The main findings are the following: (1) comet-marks localize on carbonate mass transported blocs outcropping on the seafloor; (2) Clearly show a polyphase evolution of the bedforms of comet mark presenting alternations of erosion and sedimentation phases. The bedforms therefore record long-term variations in bottom current activity with an alternation of intense hydrodynamic events (erosion) and quieter hydrodynamic periods (deposition) through time, reflecting a complex hydrodynamic history; (3) At present, comet-marks recorded a significant decrease in current velocity within the erosional zones located inside the comet tails associated with fined-grained sediments infill in this area, highlighting the need for cautious interpretation of such features as direct indicators of present-day current intensity; (4) Finally, a result that was not necessarily anticipated but documented by exploring those bedforms with the Nautile submersible, comet-marks host quite important benthic and epibenthic biodiversity with a wide variety of associated species.
(Marine Geology. vol. 493, n° 0025-3227, pp. 107717, 01/03/2026)
CEFREM, UPVD, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LOCEAN-CYBIOM, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, LOCEAN-VALCO, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, LOPS, IRD, IFREMER, INSU - CNRS, UBO EPE, CNRS, GEO-OCEAN, UBS, IFREMER, INSU - CNRS, UBO EPE, CNRS, ENTROPIE [Réunion], IRD, UR, CNRS, ISTerre, IRD, INSU - CNRS, USMB [Université de Savoie] [Université de Chambéry], CNRS, Fédération OSUG, UGA
Polar Front System Variability and Its Control on Export Rain Ratio Over the Past 800 ka: Implication for Atmospheric p CO 2 Changes
Little is known about long-term variability in the organic carbon to carbonate carbon export rain ratio, despite its key role in the global carbon cycle. Here, we reconstruct glacial-interglacial changes in the sedimentary rain ratio over the Southern Ocean, using micropaleontological (coccoliths and foraminifera) and geochemical (CaCO 3 , Total Organic Carbon (TOC), δ 13 C, C/N) records from sediment core MD04-2718, located in the Polar Front Zone (PFZ, Indian sector), complemented with published data sets from across the Subantarctic Zone (SAZ). We show that sedimentary CaCO 3 primarily reflects the export of biogenic calcium carbonate by calcifying phytoplankton and zooplankton, while TOC captures the export of phytoplanktonderived organic carbon. The sedimentary TOC/CaCO 3 ratio thus serves as a robust proxy for past variations in the balance between organic and inorganic carbon export and hence, of the export rain ratio. Our results indicate higher rain ratios during glacial periods, driven by enhanced organic carbon export, as colder conditions and intensified iron-rich dust inputs stimulated diatom productivity. In contrast, lower rain ratios during interglacials reflect strengthened biogenic carbonate export, as warmer conditions and elevated macronutrient supply from reinvigorated Southern Ocean upwelling supported coccolithophore and foraminifera blooms. These shifts reflect an ecological seesaw between silicifying and calcifying phytoplankton modulated by changes in westerly wind intensity and the position of the Polar Front. The negative correlation between rain ratios from the SAZ-PFZ and atmospheric pCO 2 suggests that enhanced organic carbon export during glacials likely promoted deepocean carbon sequestration, modulating atmospheric CO 2 levels.
Plain Language Summary Marine phytoplankton uses sunlight to convert atmospheric carbon dioxide (CO 2 ) into organic matter, which helps to store carbon in the ocean. However, certain plankton species produce calcium carbonate shells, a process that reduces this carbon storage by increasing CO 2 levels in surface waters. The balance between organic carbon and carbonate export-known as the "rain ratio"-is an important indicator of how marine life influences atmospheric CO 2 . In this study, we reconstructed changes in the rain ratio over the past 800,000 yrs from sediment samples collected in the Southern Ocean. We found that during cold glacial periods, a higher rain ratio corresponds to increased productivity of plankton with silica-based shells. During warmer interglacial periods, a lower rain ratio reflects dominance by plankton with calcium carbonate shells. These shifts between plankton communities are driven by changes in ocean conditions-cold, iron-rich waters favor silica-forming plankton, while warmer, nutrient-rich waters promote calcifiers. These environmental changes are linked to the strength of westerly winds and movements of ocean fronts. Our findings suggest that biological productivity in the Southern Ocean has played an important role in regulating Earth's carbon cycle and atmospheric CO 2 levels over long climate cycles.
(Paleoceanography and Paleoclimatology. vol. 41, n° 2572-4525, 01/03/2026)
GEOPS, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, NIOZ, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, EPHE, PSL, UB, CR2P, MNHN, SU, CNRS, ESE, CNRS, UNIBE, UNIL
Reconstruction of last millennium sea surface temperature on 1° grid using a random forest algorithm
Climate models and theoretical evidence show that the ocean drives climate from sub-decadal to centennial timescales through a variety of processes and their interactions. The range of direct climate observations, arelhowever, is too short to understand the exact role of the ocean in shaping observed and future climate variability on top of anthropogenic climate change. In the present study, we use a large set of paleoclimate records combined with a random forest algorithm to reconstruct a gridded dataset of sea surface temperatures since 850 C.E. to provide a better framework for the study of ocean surface variability. In line with modeling and paleodata studies, our reconstruction suggests that natural climate forcings have importantly influenced the last millennium climate variability. Our reconstruction also suggests that North Atlantic SST multidecadal variability influences Pacific SST on decadal timescales. However, the latter result is shown to be strongly dependent on background climate conditions. This new reconstruction offers a useful resource for testing the capabilities of climate models to reproduce the linkages between Atlantic and Pacific as well as the response to external forcings.
(Global and Planetary Change. vol. 258, n° 0921-8181, pp. 105279, 01/03/2026)
AOPP, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LOCEAN, IPSL, ENS-PSL, PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, IP Paris, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS
Multi-annual evolution of coastal dunes: Transition from fixed to transgressive dunes state
Most of coastal dunes located in temperate latitudes, especially in the Northern Hemisphere, are relatively stable. However, along the Gironde coast (SW France) substantial dune remobilization has been observed over the last decade following major marine erosion events during the 2013-2014 winter. This study is based on the analysis of a robust dataset including (i) 10 high-resolution Digital Terrain Models (DTMs) derived from airborne LiDAR surveys conducted over a 12-year period (2011-2023) and (ii) 7 Satellite-derived Digital maps of dune vegetation cover derived from Sentinel-2 satellite images acquired between 2017 and 2023. These morphological and biological parameters are linked to forcing parameters derived from observed wind data, to provide a comprehensive analysis of coastal dune changes related to the transition from vegetation-fixed dunes to the development of transgressive dunes. For the first time, morphological and vegetation dynamics are explored over a large spatial scale (tens of km), covering a range of initial dune morphology and sediment supply.
Dunes have transitioned from stable to transgressive states primarily driven by sediment stoss slope recycling process (cannibalism) across a gradient of alongshore variable dune sediment budget, ranging from slightly negative to notably positive (+10 to 15 m 3 /m/yr), Along this coast, transgressive dunes defined as dune migrating via similar stoss and lee slope migration rates, have tripled in number over the last 10 years (reaching ≈ 15 km or 17.3 % of the studied coast). At the center of the Gironde coast where dunes are heavily remobilised, the lee slope of the dune translates landward at a rate of several meters to more than 10 m/year. In the following years, dunes will probably continue to migrate and remobilise across a broader scale if no re-stabilization management plan is implemented.
(CATENA. vol. 264, n° 0341-8162, pp. 109787, 01/03/2026)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CEFREM, UPVD, INSU - CNRS, CNRS, ONF