Chapter 7 - The Younger Dryas Stadial
The Younger Dryas (YD) stadial is the last extreme cold event detected in the northern hemisphere during the last deglaciation. Many theories have been proposed to explain the causes of this event. Currently, the most accepted one is that the increased meltwater discharges into the North Atlantic or Arctic Sea produced a series of changes in ocean circulation and sea ice cover that triggered substantial shifts in the atmospheric circulation patterns. The impact of these changes is marked by a series of climate shifts within the YD stadial with a complex spatial distribution of hydroclimate in Europe in each phase.
(pp. 51-57, 01/01/2023)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Trajectories of nutrients concentrations and ratios in the French coastal ecosystems: 20 years of changes in relation with large-scale and local drivers
used to determine ecosystem trajectories as well as typologies of ecosystem trajectories. It appeared that most of the French coastal ecosystems exhibited trajectories towards a decrease in nutrients concentrations. Differences in trajectories mainly depended on continental and human influences, as well as on climatic regimes. One single ecosystem exhibited very different trajectories, the Arcachon Bay with an increase in nutrients concentrations. Ecosystem trajectories based on ordination techniques were proven to be useful tools to monitor ecosystem changes. This study highlighted the importance of local environments and the need to couple uni-and multi-ecosystem studies. Although the studied ecosystems were influenced by both local and large-scale climate, by anthropogenic activities loads, and that their trajectories were mostly similar based on their continental influence, non-negligible variations resulted from their internal functioning.
(Science of the Total Environment. vol. 857, n° 0048-9697, pp. 159619, 01/01/2023)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, AD2M, CNRS, SBR, SU, CNRS, LOMIC, INSU - CNRS, SU, CNRS, OOB, SU, CNRS
Seasonal, Diurnal, and Tidal Variations of Dissolved Inorganic Carbon and pCO2 in Surface Waters of a Temperate Coastal Lagoon (Arcachon, SW France)
We report on diurnal, tidal, and seasonal variations of dissolved inorganic carbon (DIC), water partial pressure of CO2 (pCO2), and associated water–air CO2 fluxes in a tidal creek of a temperate coastal lagoon with 70% of intertidal flats, during eight tidal/diurnal cycles and two consecutive years covering all seasons. Surface waters of the lagoon were always slightly oversaturated in CO2 with respect to the atmosphere with an average pCO2 value of 496 ± 36 ppmv. Seasonally, subsurface water pCO2 values were controlled by both temperature and biological/tidal advection effects that compensated each other and resulted in weak annual variations. High-resolution temporal pCO2 records reveal that the highest fluctuations (192 ppmv) occurred at the tidal/diurnal scale as a result of biological activity, advection from the tidal flat, and porewater pumping that all contributed to water pCO2 and carbonate chemistry variations. Total alkalinity (TA) versus salinity plots suggest a net production of alkalinity in the lagoon attributed to benthic carbonate dissolution and/or anaerobic degradation of organic matter. We specifically highlighted that for the same salinity range, during flooding, daytime pCO2 were generally lower than nighttime pCO2 values because of photosynthesis, whereas during ebbing, daytime pCO2 were higher than nighttime pCO2 values because of heating. Waters in the lagoon were a relatively weak CO2 source to the atmosphere over the year compared to other estuarine and lagoon waters elsewhere, and to sediment-air fluxes measured simultaneously by atmospheric Eddy Covariance (EC) in the Arcachon lagoon. Because of low values and small variations of the air-sea pCO2 gradient, the variability of fluxes calculated using the piston velocity parameterization was greatly controlled by the wind speed at the diurnal and, to a lesser extent, seasonal time scales. During the emersion, the comparison of these pCO2 data in the tidal creek with EC fluxes measured 1.8 km away on the tidal flat suggests high heterogeneity in air-sea CO2 fluxes, both spatially and at short time scales according to the inundation cycle and the wind speed. In addition to tidal pumping when the flat becomes emerged, our data suggest that lateral water movement during the emersion of the flat generates strong spatial heterogeneity in water–air CO2 flux.
(Estuaries and Coasts. vol. 46, n° 1559-2723, pp. 128-148, 01/01/2023)
LERPC, COAST, IFREMER, MARE, ULiège, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IFREMER, LPG, UM, UA, INSU - CNRS, CNRS, Nantes univ - UFR ST, Nantes Univ, BOREA, UNICAEN, NU, MNHN, IRD, SU, CNRS, UA
New Southern Ocean transfer function for subsurface temperature prediction using radiolarian assemblages
(Marine Micropaleontology. vol. 178, n° 0377-8398, pp. 102198, 01/01/2023)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Expedition 397 Preliminary Report: Iberian Margin Paleoclimate
From 11 October to 11 December 2022, International Ocean Discovery Program Expedition 397 took place off the coast of Portugal southwest of Lisbon. The main objective was to recover the exceptional sedimentary archive preserved beneath the seafloor on the Iberian margin to study past climate change at high temporal resolution. During the expedition, which carried 26 international scientists, four sites were drilled, recovering 6.2 km of marine sediments that accumulated rapidly, thereby providing a high-fidelity record of past climate change on timescales of hundreds to thousands of years and extending back millions of years ago. Climate signals from these marine sediment cores will be correlated precisely to polar ice cores from both hemispheres and with European pollen records, providing a rare opportunity to link oceanic, atmospheric, and terrestrial climate and environmental changes. The four drill sites are located at different water depths (1339, 2590, 3479 and 4691 m below sea level), permitting scientists to study how deep-ocean circulation and chemistry changed in the past, including its role in deep-sea carbon storage and atmospheric CO2 changes. The sediment cores recovered during Expedition 397 will provide benchmark records of North Atlantic climate change at high temporal resolution from the late Miocene (about 8 million years ago) to present. This period includes the last 3 million years when changes in the Earth's orbit resulted in the growth and decay of large ice sheets in the Northern Hemisphere and a warmer world before this time when atmospheric CO2 was similar to today. All cores recovered show strong changes in physical properties (such as color) that represent a response to known cyclic changes in Earth’s orbit, which will aid in accurately dating the sediment. Many years of research will be needed to extract the detailed climatic signals from the kilometers of core recovered during Expedition 397, but the records to be produced will be vital for testing numerical climate models and understanding how the climate system works and how it might change in the future.
(International Ocean Discovery Program Preliminary Reports, n° 2372-9562, pp. 397, 24/02/2026)
IPGP - UMR_7154, INSU - CNRS, IGN, UR, IPG Paris, CNRS, UPCité, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Transgenerational endocrine disruptor effects of cadmium in zebrafish and contribution of standing epigenetic variation to adaptation
Evidence has emerged that environmentally-induced epigenetic changes can have long-lasting effects on gene transcription across generations. These recent findings highlight the need to investigate the transgenerational impacts of pollutants to assess their long term effects on populations. In this study, we investigated the transgenerational effect of cadmium on zebrafish across 4 generations. A first whole methylome approach carried out on fish of the first two generations led us to focus our investigations on the estradiol receptor alpha gene (esr1). We observed a sex-dependent transgenerational inheritance of Cd-induced DNA methylation changes up to the last generation. These changes were associated with single nucleotide polymorphisms (SNPs) that were themselves at the origin of the creation or deletion of methylation sites. Thus, Cd-induced genetic selection gave rise to DNA methylation changes. We also analyzed the transcription level of various sections of esr1 as well as estrogen responsive genes. While Cd triggered transgenerational disorders, Cd-induced epigenetic changes in esr1 contributed to the rapid transgenerational adaptation of fish to Cd. Our results provide insight into the processes underpinning rapid adaptation and highlight the need to maintain genetic diversity within natural populations to bolster the resilience of species faced with the global environmental changes.
(Journal of Hazardous Materials. vol. 455, n° 0304-3894, pp. 131579, 24/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UMS POREA, INSU - CNRS, CNRS, INRAE, CBIB, TRI-Genotoul, UT3, Comue de Toulouse, INSERM, CNRS, INRAE, IBGC, UB, CNRS
Contribution des méthodes d'imagerie drone à l'étude des bassins fracturés : application à la plate-forme mésozoïque nord-Aquitaine.
Dans les bassins sédimentaires, la connaissance du réseau de fractures et de la manière dont il s'est développé au cours du temps permettent de mieux contraindre les conditions actuelles de migration des fluides (eaux, saumures, hydrocarbures, CO2). Bien que souvent associés aux données de reconnaissances (sismique 3D, forages...), ces réseaux peuvent également être observés et caractérisés à partir d'affleurements sur le terrain. Les surfaces stratigraphiques, en particulier, font l'objet d'un nombre croissant d'études avec le développement de l'imagerie à haute résolution à partir de drone. L'objectif de cette étude est de caractériser le réseau de fracturation de la partie nord du bassin Aquitain afin de reconnaître les principaux épisodes de fracturations. Pour cela, des ortho-images drone ont été acquises sur le littoral Atlantique entre la Vendée et la Charente Maritime. L'âge des terrains varient depuis l'Hettangien au nord jusqu'au Tithonien au sud. Cet enregistrement sédimentaire permet potentiellement d'estimer l'âge des déformations sur l'intervalle 200-150 Ma à l'aide des critères de chronologie relative. Cette approche est complétée par datation U/Pb sur cristaux de calcite qui remplissent certaines populations de fractures. Les premiers résultats mettent en évidence une période de calme tectonique entre 200 et 150 Ma, suivie par deux phases d'ouverture de fractures orientées E-W à la fin du Jurassique et au milieu du Crétacé supérieur. Localement, une reprise en compression selon une direction NNW-SSE recoupe l'ensemble des fractures en ouverture et est attribuée à la propagation en champ lointain de contraintes Pyrénéennes.
(24/02/2026)
LPG - Le Mans, LPG, UM, UA, INSU - CNRS, CNRS, Nantes univ - UFR ST, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GR, UR, INSU - CNRS, CNRS
The effects of artificial light at night on behavioral rhythm and related gene expression are wavelength dependent in the oyster Crassostrea gigas
Artificial light at night (ALAN) constitutes a growing threat to coastal ecosystems by altering natural light cycles, which could impair organisms’ biological rhythms, with resulting physiological and ecological consequences. Coastal ecosystems are strongly exposed to ALAN, but its effects on coastal organisms are poorly studied. Besides ALAN’s intensity, ALAN’s quality exposure may change the impacts on organisms. This study aims to characterize the effects of different ALAN’s spectral compositions (monochromatic wavelength lights in red (peak at 626 nm), green (peak at 515 nm), blue (peak at 467 nm), and white (410–680 nm) light) at low and realistic intensity (1 lx) on the oyster Crassostrea gigas daily rhythm. Results reveal that all ALAN’s treatments affect the oysters’ daily valve activity rhythm in different manners and the overall expression of the 13 studied genes. Eight of these genes are involved in the oyster’s circadian clock, 2 are clock-associated genes, and 3 are light perception genes. The blue light has the most important effects on oysters’ valve behavior and clock and clock-associated gene expression. Interestingly, red and green lights also show significant impacts on the daily rhythm, while the lowest impacts are shown with the green light. Finally, ALAN white light shows the same impact as the blue one in terms of loss of rhythmic oysters’ percentage, but the chronobiological parameters of the remaining rhythmic oysters are less disrupted than when exposed to each of the monochromatic light’s treatments alone. We conclude that ALAN’s spectral composition does influence its effect on oysters’ daily rhythm, which could give clues to limit physiological and ecological impacts on coastal environments.
(Environmental Science and Pollution Research. vol. 30, n° 0944-1344, pp. 120375-120386, 24/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Temperature variations in caves induced by atmospheric pressure variations-Part 2: Unveiling hidden thermal signals
In underground cavities, temperature variations of the order of 10-3 °C are permanently induced by the variations of atmospheric pressure, even at great depths, with couplings of the order of 0.2 to 20 × 10-3 °C/hPa depending on frequency. In the first part of this study, we established the atmospheric pressure to temperature transfer function (TF) as a function of frequency from 8 × 10-7 to 8 × 10-4 Hz. Here, we use this TF to calculate the expected PIT variations, which, after being subtracted from the observed time-series, provide residual temperature time-series. We calculated such temperature residuals in four natural caves in France: Esparros, Aven d'Orgnac, Pech Merle and Chauvet-Pont d'Arc Caves, the last two containing unique prehistoric wall paintings. Temperature signals, as small as a few 10-3 °C, due to human presence, are then conspicuous, with evidence of relaxation longer than several days and long-term cumulative effects. In addition, we observe temperature signals suggesting non-stationary states characterized by several processes which are not necessarily easy to separate, such as transient air currents, due to barometric winds or locally semi-confined convection cells, transient infiltration, or energy dissipation by evaporation-condensation at the rock surface. This background thermal agitation displays a scale-free amplitude spectrum, from 2 × 10-5 to 4 × 10-4 Hz, of the form f-α, with α varying from 0.1 to 0.6 depending on the site. Furthermore, at the Chauvet Cave, a weak but unambiguous peak emerges during some months at a period of about 82.2 ± 0.8 minutes, suggesting a Helmholtz-type resonance. Small but significant temperature signals are therefore detected in underground cavities once the effect of atmospheric pressure variations is corrected for. These signals reveal subtle coupled processes whose knowledge is essential to evaluate preservation strategies and to establish conditions for resilience of underground systems under artificial or natural influence including climate change.
(Geosystems and Geoenvironment. vol. 2, 24/02/2026)
IPGP - UMR_7154, INSU - CNRS, IGN, UR, IPG Paris, CNRS, UPCité, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GET, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS
Settling dynamics of cohesive sediments in a highly turbid tidal river
An optical settling column was used in the Garonne Tidal River to estimate the settling velocity of suspended matter in surface waters over a period characterized by contrasting hydrological conditions. A time and space variability of settling velocity was observed during this study. The settling velocities of surface suspended matter ranged from 0.018 to 0.268 mm.s −1 , and the median diameter of dispersed particles varied from 4.74 to 14.38 µm. The data revealed the physical processes influencing the sediment settling dynamics throughout different time scales in a highly turbid tidal river. On tidal and fortnightly time scales, resuspension, deposition and advection mechanisms were the major drivers of the settling velocity variability, while it is likely that the estuarine turbidity maxima (ETM) was responsible for seasonal variations. The findings of this work suggest that in tidal rivers, salinity is too low to promote flocculation, whereas ETM can play a key role in enhancing this process. The stronger variability in settling velocity occurs on a tidal timescale, with median values up to four times higher at the end of the ebb tide than at high water. These variations cannot be correlated to salinity or sediment concentration. On a seasonal timescale, flocculation appears to be strongly correlated with the presence of the ETM and associated fluid mud layer. A simple correlation based on tidal variations seems to be a better predictor than the relationships based on the sediment concentration.
(Marine Geology. vol. 457, n° 0025-3227, pp. 106995, 24/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IGE, IRD, INSU - CNRS, CNRS, INRAE, Fédération OSUG, UGA, Grenoble INP, UGA