High-resolution, large-scale laboratory measurements of a sandy beach and dynamic cobble berm revetment
(Scientific Data, 21/04/2026)
SBMS, LEGOS, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, UGent, UGent, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, FZK
Reinterpreting the Bruun Rule in the Context of Equilibrium Shoreline Models
Long-term (>decades) coastal recession due to sea-level rise (SLR) has been estimated using the Bruun Rule for nearly six decades. Equilibrium-based shoreline models have been shown to skillfully predict short-term wave-driven shoreline change on time scales of hours to decades. Both the Bruun Rule and equilibrium shoreline models rely on the equilibrium beach theory, which states that the beach profile shape equilibrates with its local wave and sea-level conditions. Integrating these two models into a unified framework can improve our understanding and predictive skill of future shoreline behavior. However, given that both models account for wave action, but over different time scales, a critical re-examination of the SLR-driven recession process is needed. We present a novel physical interpretation of the beach response to sea-level rise, identifying two main contributing processes: passive flooding and increased wave-driven erosion efficiency. Using this new concept, we analyze the integration of SLR-driven recession into equilibrium shoreline models and, with an idealized test case, show that the physical mechanisms underpinning the Bruun Rule are explicitly described within our integrated model. Finally, we discuss the possible advantages of integrating SLR-driven recession models within equilibrium-based models with dynamic feedbacks and the broader implications for coupling with hybrid shoreline models
(Journal of Marine Science and Engineering. vol. 9, n° 2077-1312, pp. 974, 21/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM, USGS
Pesticide mixture toxicity assessment through in situ and laboratory approaches using embryo-larval stages of the pacific oyster (Magallana gigas)
Worsened state of oysters in French Arcachon Bay, demand an investigation of possible causes. This study evaluated the effects of an environmentally relevant mixture of five common pesticides on the early-life stages of the Pacific oyster (Magallana gigas). Laboratory assays with artificial mixture and in situ transplantation were complementarily used to investigate a series of sublethal endpoints. The laboratory exposure revealed developmental toxicity at 0.32 μg/L, which corresponds to mixture concentrations in Arcachon Bay. Downregulation of some gene transcriptions was observed at environmental level. No difference in larvae development was revealed among the three sites in Arcachon Bay. This study was the first to evaluate locomotion of oyster larvae exposed in situ. Suspected poor water quality in the inner part of Arcachon Bay was reflected by impairment at the molecular level. In conclusion, current concentrations of the tested pesticides in Arcachon Bay hinder larval development and affect several biological functions.
(Marine Environmental Research. vol. 169, n° 0141-1136, pp. 105390, 21/04/2026)
MU / MUNI, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Fluvial sand, Amazon mud, and sediment accommodation in the tropical Maroni River estuary: Controls on the transition from estuary to delta and chenier plain
The Maroni River, South America, is a tropical estuary encased in a narrow lower valley with a limited area of estuarine tidal flat development, and displays a channel with large downstream-migrating sandy bedforms linked to a large sand-filled shallow mouth. The sand-rich nature of the lower Maroni River reflects significant fluvial bedload supply, and the Maroni is among rivers with the lowest suspension-sized sediment load in the world. During the dry season, the estuary shows high suspended sediment concentrations near the bottom (several g/l) that are due to the ingress of mud streaming alongshore from the Amazon River delta. However, Amazon mud is expelled from the estuary during the high-discharge rainy-season, and seems to be essentially restricted to this seasonal intrusion along the main channel with little net estuarine sedimentation because of limited chan- nel overbank sediment accommodation space. Sand actively supplied by the Maroni River to the coast has been diverted by wave-generated longshore transport westwards, towards the Suriname coast. This has resulted in the construction of numerous sandy cheniers within a muddy coastal plain built from Amazon mud. This sedi- ment-source dichotomy is an important original feature of the Guiana Shield estuaries. The asymmetric prograda- tion at the mouth of the Maroni fingerprints the westward growth, in the vicinity of river mouths, of the muddy, chenier-studded, coastal plain of the Guianas. The propensity for these rivers to supply sand to the coast, even- tually evolving into deltas, depends on the ability of their estuaries to limit westward (downdrift) deflection by long-term updrift coastal sedimentation. The Maroni estuary has tended to evolve towards a delta built from both Maroni river sand and Amazon mud, a stage, among the Guiana Shield Rivers, that only the large Essequibo River estuary in Guyana has achieved. Further studies will be needed in order to constrain the infill pattern of the Maroni River estuary and its mouth.
(Regional Studies in Marine Science. vol. 41, n° 2352-4855, pp. 101548, 21/04/2026)
LEEISA, IFREMER, UG, CNRS, CEREGE, IRD, AMU, CdF (institution), INSU - CNRS, CNRS, INRAE, IEPA, Cerema, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
The Seine River Basin
Among the six hydrographic basins of metropolitan France, the Seine-Normandy basin is the most human-impacted. This territory of 76,000 km 2 and 17 million people receives the highest anthropogenic pressure, due to its industrial and agri- cultural activities linked to the development of the urban area of Paris, which has been and still is the economic and social heart of France. These pressures have gradually impacted the hydrological, chemical, and ecological functioning of the basin, leading to a maximum chemical degradation between the 1960s and the 1990s. The very poor chemical and ecological status of water bodies in the 1980s led a small group of researchers to propose a PIREN-Seine, i.e. an interdisciplinary environmental research program created by the French National Centre for Scien- tific Research (CNRS). This program was launched in 1989 in the context of insufficient wastewater treatment in the Paris conurbation. Its first achievement consisted in developing models to better understand the river hydrological and biogeochemical functioning. These tools have made it possible to bring together research teams on a common object of study, the whole Seine watershed; the program has also been a forum for dialogue between the basin ’ s institutional partners and researchers, enabling the latter to make management proposals to establish investment priorities based on the results of these models. Over the past 30 years, the PIREN-Seine program has grown up, has attracted social scientists, and has generated a vast number of disciplinary and interdisci- plinary publications, more than 100 PhD theses, hundreds of publications in scientific journals, and as many communications in international workshops and conferences. Nevertheless, the collective visibility of this group of scientists and institutional partners is still relatively low internationally, since most publication credits are given to individuals, to their laboratories, or to their research institutions. Moreover, the names of these laboratories and institutions have also evolved over time, making the recognition of this collective effort even more difficult. This book is the opportunity to present the most salient or recent results of the program, presented here as trajectories that relate environmental changes, societal changes, and the state of the Seine River basin waterbodies, which is nowadays largely controlled by the balance between pressures, water and river uses, and social responses. The book covers a broad range of topics such as (1) the estimation of fluxes transported from headwaters to the coastal zone, at a very fine spatial scale, using models, (2) long-term analyses (50–200 years) of the socio-ecosystem Seine, using archives, retro and prospective modeling, (3) the identification and quantification of sources and transfer of a wide variety of elements and pollutants (nutrients, carbon, trace metals, POPs, pharmaceuticals, pesticides, microplastics, etc.), (4) the study of microbial contaminations, and (5) the analysis of the impact of water quality and contaminations on biota. Studies considering the Seine River basin as a socio-ecological system are increasingly present within the PIREN-Seine program, which has been included in the Zone Atelier Seine (ZA Seine). The latter coordinates the research activities on the Paris city, the Seine River basin, and the Seine River estuary. It is also part of the European Long-Term Socio-Economic and Ecosystem Research (LTSER) pro- grams. The large size of the basin and the longue-dure´e approach (up to 200 years) make this territory a rare and fully documented example of the multiple and evolving interrelations between a river, its large basin and their society which characterize the Anthropocene era.
(. vol. 90, 21/04/2026)
GEOSCIENCES, PSL, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, METIS, EPHE, PSL, INSU - CNRS, SU, CNRS
Uncertainties in Shoreline Projections to 2100 at Truc Vert Beach (France): Role of Sea‐Level Rise and Equilibrium Model Assumptions
Sandy shorelines morphodynamics responds to a myriad of processes interacting at different spatial and temporal scales, making shoreline predictions challenging. Shoreline modeling inherits uncertainties from the primary driver boundary conditions (e.g., sea-level rise and wave forcing) as well as uncertainties related to model assumptions and/or misspecifications of the physics. This study presents an analysis of the uncertainties associated with future shoreline evolution at the cross-shore transport dominated sandy beach of Truc Vert (France) over the 21st century. We explicitly resolve wave-driven shoreline change using two different equilibrium modeling approaches to provide new insight into the contributions of sea-level rise, and free model parameters uncertainties on future shoreline change in the frame of climate change. Based on a Global Sensitivity Analysis, shoreline response during the first half of the century is found to be mainly sensitive to the equilibrium model parameters, with the influence of sea-level rise emerging in the second half of the century (∼2050 or later), under several simulated scenarios. The results reveal that the seasonal and interannual variability of the predicted shoreline position is sensitive to the choice of the wave-driven equilibrium-based model. Finally, we discuss the importance of the chronology of wave events in future shoreline change, calling for more continuous wave projection time series to further address uncertainties in future wave conditions. Our contribution demonstrates that unmitigated climate change can result in shoreline retreat of several tens of meters by 2100, even for sectors that have been stable or slightly accreting over the last century.
(Journal of Geophysical Research: Earth Surface. vol. 126, n° 2169-9003, pp. e2021JF006160, 21/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM
Satellite-derived shoreline detection at a high-energy meso-macrotidal beach
Publicly available satellite imagery can now provide multi-decadal time series of shoreline data from local to global scale, enabling analysis of sandy beach shoreline variability across a spectrum of temporal scales. Such data can, however, be associated with large uncertainties, particularly for beaches experiencing a large tidal range (>2 m) and energetic incident waves. We use a decade of bi-monthly topographic surveys at the high-energy meso-macrotidal beach of Truc Vert, southwest France, and concurrent wave and water-level hindcast to investigate the uncertainties associated with satellite-derived time series of the shoreline position. We show that consideration of the water level and wave runup elevation is critical for accurately estimating waterline position and, in turn, shoreline position. At Truc Vert, including non-tidal water level residuals (e.g. wind-driven surge) and accounting for time- and elevation-varying beach slope for horizontal correction did not improve satellite-derived shoreline position. A new total water level threshold is proposed to maximize the number of usable images while minimizing errors. Accounting for wave runup and the new water level threshold at Truc Vert, the number of usable satellite images is doubled and shoreline position errors are at least halved compared to previous work at this site. Using the 1984–2019 reconstructed shoreline, we also show that the satellite-derived shoreline trends and interannual variability are in better agreement with field measurements. Although the approach proposed here needs to be tested on other sites in different tidal/wave forcing environments with different morphological and sediment characteristics, we anticipate that it will improve the temporal and spatial description of shoreline change on most surf tidal beaches where accurate continuous water level and wave hindcasts and/or observations are available.
(Geomorphology. vol. 383, n° 0169-555X, pp. 107707, 21/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, SBMS
Morphological and ecological responses of a managed coastal sand dune to experimental notches
In northern Europe, coastal dune remobilization by restoring natural processes is considered by some to maintain the coastal dune in chronically eroding sectors by migrating landward and to restore dune ecology. In wet climatic contexts, this nature-based solution has been shown to induce an increase in both sand bare areas and vegetation diversity. However, it has never been tested in the coastal dunes of southern Europe with a drier climate and, thus, more stressful conditions, where disturbance may inversely decrease vegetation diversity. An original experiment was set up in 2018 on a 4-km stretch of coastal dune in southwest France where Experimental Notches (EN) were excavated in the incipient foredune, referred to as West Experimental Notch (WEN), and in the established foredune, referred as to East Experimental Notch (EEN). Morphological and ecological responses were monitored using UAV photogrammetry and vegetation sampling along transects during two years with contrasted winter storm conditions. During the first winter characterized by calm wind conditions, a rapid filling of the WENs and the initiation of deposition lobes landward of the EENs were observed. Stronger winds during the second winter led to the development of deposition lobes of the EENs, increasing both their volume, up to 6 times, and their cross-shore elongation. The increase in disturbance induced by the notches had a significant impact on vegetation. New sandy bares were colonized by pioneer species leading to an increase in species richness and rejuvenation, in particular landward of the EENs. Although longer-term monitoring is required to draw conclusions, these results suggest that the excavation of foredune notches are able to re-establish an ecomorphological dynamic in the dunes of southwest France on the time scales of years, promoting landward sand transport and, thus, the foredune landward translation, while not threatening diversity. Such approach may become a relevant adaptation strategy to sea level rise and increased erosion in this region of the world.
(Science of the Total Environment. vol. 782, n° 0048-9697, pp. 146813, 21/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ONF
Multidecadal Evolution of the Turbidity Maximum Zone in a Macrotidal River Under Climate and Anthropogenic Pressures
Climate and human pressures can influence the evolution of estuarine sediment dynamics concurrently, but the understanding and quantification of their cause–effect relationships are still challenging due to the occurrence of complex hydro-morpho-sedimentary feedbacks. The Garonne Tidal River (GTR, upper Gironde Estuary, France) is a clear example of a system stressed by both anthropogenic and climate change, as it has been subject to decreasing river discharges, natural morphological changes, and gravel extraction. To understand the relative effect of each hydrological and geomorphological pressure on the turbidity maximum zone (TMZ), the sediment dynamics in the GTR over the last six decades was evaluated using the width-averaged idealized iFlow model. Model results show a gradual increase in tidal amplitude and currents over the decades that has led to the upstream shift of the landward sediment-transport capacity components (external M4 tide, spatial settling lag, and tidal return flow). The upstream displacement of the TMZ between the 1950s and the 2010s was estimated to be at least 19 km, of which about three fourth was induced by geomorphological changes and one fourth by hydrological changes. Concerning the geomorphological changes, the natural evolution of the lower Gironde morphology was the main pressure inducing the displacement of the TMZ in the GTR. Anthropogenic and natural changes in morphology and bed roughness in the GTR itself also contributed to this evolution. The natural geomorphological changes were, in turn, probably promoted by the evolution of sediment dynamics, so this study reveals the closed circle that governs the intensification of the TMZ.
(Journal of Geophysical Research. Oceans. vol. 126, n° 2169-9275, pp. e2020JC016273, 21/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, TU Delft
Climate and the Evolution of the Ocean: The Paleoceanographic Data
The idea of reconstructing the history of oceans and climates in the past using marine sediment cores arrived quite late after the beginnings of oceanography. It was initiated in the twentieth century, well after the first attempts to measure variations in seawater temperature down the water column, which date back to the eighteenth century with the great circumnavigation expeditions. Land geologists were the first to propose paleoceanographic reconstructions from exposed marine series, limiting the collected information to former coastal waters.
(pp. 225-254, 21/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, IFREMER, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, LGO, UBS, IFREMER, UBO EPE, CNRS