Environmental significance of kaolinite variability over the last centuries in crater lake sediments from Central Mexico
Environmental conditions have a notable impact on clay minerals, primarily because of the chemical reactions they undergo with their immediate environment. These reactions are more pronounced in hot and humid tropical regions, and therefore, the study of clays deposited at the bottom of lakes in tropical regions can yield valuable insight into past environmental conditions. Here we present multiproxy records, including physical (magnetic susceptibility, grey-scale level and grain size), mineralogical (X-ray diffraction, Simultaneous Thermal Analysis, Fourier-Transform Infrared Spectroscopy), and geochemical (elemental composition by XRF-core scanner, organic geochemistry by IRMS) data, from three 210Pb-dated sediment cores (spanning recent centuries < CE 1470) retrieved from crater lakes Los Espinos, Tacámbaro and Teremendo in the Trans-Mexican Volcanic Belt (TMVB), central Mexico. The mineralogical results showed that disordered kaolinite, formed by hydrolysis and hydrothermal alteration, was the predominant mineral in the sediments of the three lakes. The abundance of kaolinite changed in line with organic carbon and organic matter-related elements (Br, S and Ni) and showed opposite trends with lithogenic elements (Ti, K, and Fe). The geochemical data further suggested that increases in kaolinite abundance are linked to the formation of organo-mineral aggregates related to periods of elevated lake productivity that in turn may reflect lake level changes in the closed basins. In Lake Tacámbaro, following the construction of a canal in the early 20th century and subsequent regulation of lake level, the relationship between organic material and kaolinite was no longer present
(Applied Clay Science. vol. 247, n° 0169-1317, pp. 107211, 21/06/2026)
AGEs, ULiège, INCIT-UMSNH, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ULiège, BGS, UB, CNRS
Late Miocene onset of the modern Antarctic Circumpolar Current
The Antarctic Circumpolar Current plays a pivotal role in global climate through its strong influence on the global overturning circulation, ocean heat and CO 2 uptake. However, when and how the Antarctic Circumpolar Current reached its modern-like characteristics remains disputed. Here we present neodymium isotope and sortable silt records from sediment cores in the Southwest Pacific and South Indian oceans spanning the past 31 million years. Our data indicate that a circumpolar current like that of today did not exist before the late Miocene cooling. These findings suggest that the emergence of a homogeneous and deep-reaching strong Antarctic Circumpolar Current was not linked solely to the opening and deepening of Southern Ocean Gateways triggering continental-scale Antarctic Ice Sheet expansion during the Eocene-Oligocene Transition (∼34 Ma). Instead, we find that besides tectonic pre-conditioning, the expansion of the Antarctic Ice Sheet and sea ice since the middle Miocene Climate Transition (∼14 Ma) played a crucial role. This led to stronger density contrast and intensified Southern Westerly Winds across the Southern Ocean, establishing a vigorous deep-reaching circumpolar flow and an enhanced global overturning circulation, which amplified the late Cenozoic global cooling. The Antarctic Circumpolar Current (ACC), driven by the interplay among Southern Westerly Winds (SWW), buoyancy forcing and bathymetry 1 , is the largest ocean current on Earth. It actively regulates the transport of heat, moisture, carbon and nutrients between the Southern Ocean and the low-latitude regions, thus substantially influencing atmospheric CO 2 and global climate 1. To assess the future response of the ACC to ongoing climate warming and its impacts on Antarctic Ice Sheet dynamics, global circulation and climate 2 , it is critical to unravel
(Nature Geoscience. vol. 17, n° 1752-0894, pp. 165 - 170, 21/06/2026)
UB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEGOS, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, UTAS, NORCE, BCCR, BIO / UiB, UiB, GET, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS
Quantifying particulate organic matter: source composition and fluxes at the river-estuary interface
Particulate organic matter (POM) characteristics and variability have been widely studied along the land-ocean aquatic continuum, yet, gaps remain in quantifying its source composition, fluxes, and dynamics at the river-estuary interface. POM in rivers consists of a complex mixture of sources, derived both from locally produced (i.e. phytoplankton) and from adjacent ecosystems (e.g. terrestrial POM). Each source differ in its trophic and biogeochemical characteristics, hence impacting its integration into local food webs, its transfer to estuaries and sea, and its contribution to biogeochemical processes. In this study, we use a robust approach based on in situ POM to characterize river POM end-members, to quantify POM composition and dynamics, and to identify the related key drivers. This study was performed at the River-Estuary interface of one of the main rivers in Western Europe (the Loire River, France). For 3 years, we conducted bimonthly measurements of carbon and nitrogen isotopic (δ 13 C, δ 15 N) and elemental (C/N) ratios to quantify the contribution of two sources (phytoplankton and terrestrial POM) to the POM mixture and calculated annual fluxes of particulate organic carbon (POC) and nitrogen (PN) sources. Throughout the year, POM consisted of ~65% phytoplankton and 35% terrestrial POM. The mean annual export fluxes were 40.6 tPOC/year and 2.45 tPN/year over the studied period, with half of it originating from phytoplankton (53 and 55% for POC and PN, respectively). We observed a clear seasonal pattern in POM composition: phytoplankton predominated from March to October, in relation to high primary production, while terrestrial contributions were the highest from November to February, driven by greater autumn-winter hydrodynamics. Our study illustrate the interest of such an approach to quantify POM composition in aquatic system and estimate source fluxes, and provide fundamental results for estimating seasonal baselines in food webs, establishing biogeochemical budgets, and quantifying POM exports to estuarine and marine environments. Applying this methodology across a broad spectrum of aquatic systems should enhance our understanding of biogeochemical processes and organic matter transformation along the land-ocean continuum and illustrates the contribution of these ecosystems to global biogeochemical cycles.
(Frontiers in Freshwater Science. vol. 2, n° 2813-7124, 21/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Millennial‐Scale Climate Variability Potentially Shaped the Early Interglacial Optimum in Southern Europe
The seasonal and latitudinal distribution of insolation is considered the main factor controlling the magnitude and timing of interglacial periods. However, despite small differences in insolation forcing, vegetation and hydrology in southern Europe during past interglacials are variable and the gradual change in insolation cannot explain the observed short‐lived forest optimum. Here we focus on vegetation and hydroclimatic changes at orbital‐ and suborbital‐scales in southwestern Europe during two past warm interglacial periods with reduced ice‐sheets, namely Marine Isotope Stages (MIS) 9e and 5e. We provide new pollen and sea surface temperatures records for MIS 9e from IODP Site U1385. This pollen record shows a forest expansion in southern Iberia over a 14 ky interval, bracketed by the millennial‐scale cooling events of Termination IV and MIS 9d. Between 334.5 and 332.5 ka, forest expansion reached a maximum, suggesting increased winter moisture during early MIS 9e. Model‐data comparison for MIS 9e and 5e shows that insolation is the main driver of the orbital‐scale vegetation and precipitation changes in Iberia, atmospheric CO2 forcing playing a secondary role. The high‐frequency component of the MIS 9e and 5e forest timeseries highlights the early interglacial forest and precipitation maxima as prominent suborbital events lasting ∼2 ky. We propose that the primarily insolation‐driven forest and precipitation optima were fostered by the non‐equilibrium conditions generated by the millennial‐scale deglacial variability during the early interglacials. Additionally, the early end of these optima may have been favored by a cooling and drying event that is part of the persistent intra‐interglacial variability.
(Paleoceanography and Paleoclimatology. vol. 39, n° 2572-4525, pp. e2024PA004846, 21/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CCMAR, UAlg, IPMA, IDAEA, CSIC
Observations of Tide- and Wave-Driven Groundwater Dynamics in Meso-Tidal Sandy Beach
This study focuses on the non-hydrostatic groundwater dynamics of a meso-tidal sandy beach under the influence of tides and waves. A field campaign was conducted at Lacanau Beach, France, during four consecutive tide cycles in March 2022. Groundwater dynamics was monitored based on a network of buried pressure sensors. The data analysis revealed the combined influences of waves and tides on the groundwater circulation. Tidal-scale groundwater flows are predominantly seaward, primarily controlled by the head gradient resulting from a high coastal aquifer. A circulation cell develops under the swash zone and moves across the beachface following the tidal oscillations. On a daily scale per alongshore and vertical units, the observed flow is 2.5 m$^3$ .m$^{-2}$ .day$^{-1}$, i.e., 912.5 m$^3$.m$^{-2}$.year$^{-1}$. Extrapolating the present dataset, it may be expected that combined events, such as drought-induced aquifer depletion with high tides, could lead to beach-scale gradient reversal, potentially causing salinisation of the continental aquifer.
(Water. vol. 16, n° 2073-4441, 21/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, MIO, IRD, AMU, INSU - CNRS, UTLN, CNRS, SIAME, UPPA
Influence of a hydroelectric dam on fish mercury contamination along the Sinnamary River (French Guiana)
The Petit Saut hydroelectric dam and the upstream and downstream areas of the Sinnamary River in French Guiana (Amazon basin) have been studied from 1993 to 2020. The nearly thirty-years-long study of the monitoring of total mercury concentration in fish and the physicochemical survey of the environment made it possible to demonstrate the impact of the flooding of the forest and the role of the hydroelectric dam on the methylation of mercury. Results show that the physicochemical modifications generated by the construction of the dam led to a significant production of methylmercury (MeHg) in the anoxic part of the reservoir and downstream of the river leading to a strong spatio-temporal impact of the dam. Seven species of fishes are studied and their mercury concentrations vary according to many parameters: fish diet, position in the water column, site, lake oxycline level and time.
(Ecotoxicology and Environmental Safety. vol. 269, n° 0147-6513, pp. 115771, 21/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Concurrent Asian monsoon strengthening and early modern human dispersal to East Asia during the last interglacial
The relationship between initial Homo sapiens dispersal from Africa to East Asia and the orbitally paced evolution of the Asian summer monsoon (ASM)—currently the largest monsoon system—remains underexplored due to lack of coordinated synthesis of both Asian paleoanthropological and paleoclimatic data. Here, we investigate orbital-scale ASM dynamics during the last 280 thousand years (kyr) and their likely influences on early H. sapiens dispersal to East Asia, through a unique integration of i) new centennial-resolution ASM records from the Chinese Loess Plateau, ii) model-based East Asian hydroclimatic reconstructions, iii) paleoanthropological data compilations, and iv) global H. sapiens habitat suitability simulations. Our combined proxy- and model-based reconstructions suggest that ASM precipitation responded to a combination of Northern Hemisphere ice volume, greenhouse gas, and regional summer insolation forcing, with cooccurring primary orbital cycles of ~100-kyr, 41-kyr, and ~20-kyr. Between ~125 and 70 kyr ago, summer monsoon rains and temperatures increased in vast areas across Asia. This episode coincides with the earliest H. sapiens fossil occurrence at multiple localities in East Asia. Following the transcontinental increase in simulated habitat suitability, we suggest that ASM strengthening together with Southeast African climate deterioration may have promoted the initial H. sapiens dispersal from their African homeland to remote East Asia during the last interglacial.
(Proceedings of the National Academy of Sciences of the United States of America. vol. 121, n° 0027-8424, pp. e2308994121, 21/06/2026)
IEE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CUG
Wave input reduction approach to compute the alongshore distribution of breaking wave conditions along the North Médoc coast
This study introduce an input reduction (IR) methodology that we developed specifically to enhance computational efficiency in nearshore wave modeling for the complex area of the Nord Médoc coast, adjacent to one of the margest estuary in Europe (Gironde). This methodology combines simulated annealing optimization with wave modeling. We apply it to an extensive 15-year offshore wave time series obtained from MARC's WavevatchIII-based simulaton and prediction system (LOPS). The IR effectiveness is assessed by comparinf the original and simplified offshore wave time series, simulated with the spectral wave model SWAN, at three nearshore locations in our study zone. Results indicate a strong agreement nearshore between the original and simplified offshore wave time series, with mean absolute errors ranging from 8 to 20 cm for the significant wave height, 0.7 to 1 s for peak wave period and 1.2 to 3.8° for wave direction. Using an optimal number of 30 clusters, the simulated annealing optimization affectively clusters wave data. Further validation of this IR-method involves analyzing its impact on long-term sediment transport using a reduced complexity shoreline model (LX-shore). This study lays the groundwork for the set-up of the reduced-complexity shoreline model to be applied in this intricate hydro-morphodynamic zone.
(pp. 121-130, 21/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM
Environmental controls on lifeguard-estimated surf-zone hazards, beach crowds, and resulting life risk at a high-energy sandy beach in southwest France
Understanding and predicting surf zone risks is of paramount importance to prevent drowning incidents and severe spine injuries on beaches globally. This study holistically addressed life risk at La Lette Blanche beach, southwest France, during the lifeguard-patrolled summer period (July-August) 2022, where intense rip currents and shore-break waves co-exist at different times and locations along the beach. Beach crowds and the levels of rip current and shore-break wave hazards were estimated hourly by lifeguards during patrolling hours. Wave, tide and weather conditions were also continuously recorded, providing comprehensive insights into the primary environmental controls on surf zone hazards and beach attendance. Results show that the daily average rip current hazard increases with large, long-period and near shore-normal waves, while the shore-break wave hazard is increased for long-period, near shore-normal waves and large tide ranges. Beachgoer crowd numbers increase on warm, sunny and light wind days although a severe heat wave occurring in July 2022 significantly decreased daily average beach crowd and deeply affected beach use. Days characterized by strong hazards and large beach attendance were associated with the largest amount of lifeguard rescues and drowning incidents, although correlations decreased by the end of the summer. This is hypothesized 1 to be the signature of evolving lifeguard strategies (e.g. preferred locations of the supervised bathing zone, prevention measures) as they progressively increase their understanding of the surf zone hazards variability in both time and space at their beach as a function of tidal stage and incident wave conditions. Warm, sunny and light-wind sunny days (maximizing beach crowds), with large, longperiod shore-normally incident waves and large tide range (maximizing surf zone hazards) were the most risky days, with shore-break waves and rip current hazards notably peaking at different times of the day. This study shows that lifeguards can be a valuable source of data to improve understanding of the environmental controls on beach crowd, surf zone hazards and life risk at the beach, which provides critical information to the development of holistic beach risk predictors.
(Natural Hazards. vol. 120, n° 0921-030X, pp. 1557–1576, 21/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR ETTIS, INRAE
Cardiac and neurobehavioral impairments in three phylogenetically distant aquatic model organisms exposed to environmentally relevant concentrations of boscalid.
Boscalid (2-Chloro-N-(4′-chlorobiphenyl-2-yl) nicotinamide), a pyridine carboxamide fungicide, is an inhibitor of the complex II of the respiration chain in fungal mitochondria. As boscalid is only moderately toxic for aquatic organisms (LC$_{50}$ > 1–10 mg/L), current environmental levels of this compound in aquatic ecosystems, in the range of ng/L-μg/L, are considered safe for aquatic organisms. In this study, we have exposed zebrafish (Danio rerio), Japanese medaka (Oryzias latipes) and Daphnia magna to a range of concentrations of boscalid (1–1000 μg/L) for 24 h, and the effects on heart rate (HR), basal locomotor activity (BLA), visual motor response (VMR), startle response (SR), and habituation (HB) to a series of vibrational or light stimuli have been evaluated. Moreover, changes in the profile of the main neurotransmitters have been determined. Boscalid altered HR in a concentration-dependent manner, leading to a positive or negative chronotropic effect in fish and D. magna, respectively. While boscalid decreased BLA and increased VMR in Daphnia, these behaviors were not altered in fish. For SR and HB, the response was more species- and concentration-specific, with Daphnia exhibiting the highest sensitivity. At the neurotransmission level, boscalid exposure decreased the levels of L-aspartic acid in fish larvae and increased the levels of dopaminergic metabolites in D. magna. Our study demonstrates that exposure to environmental levels of boscalid alters cardiac activity, impairs ecologically relevant behaviors, and leads to changes in different neurotransmitter systems in phylogenetically distinct vertebrate and invertebrate models. Thus, the results presented emphasize the need to review the current regulation of this fungicide.
(Environmental Pollution. vol. 347, n° 0269-7491, pp. 123685, 21/06/2026)
IDAEA, CSIC, URL, CID-CSIC, CSIC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS