Post-failure Processes on the Continental Slope of the Central Nile Deep-Sea Fan: Interactions Between Fluid Seepage, Sediment Deformation and Sediment-Wave Construction,
Voluminous mass-transport deposits (MTD) have been identified on seismic profiles across the central Nile Deep-Sea Fan (NDSF). The youngest MTDs are buried under 30-100 m of well-stratified slope deposits that, in water depths of 1,800-2,600 m, are characterized by undulating reflectors correlated with slope-parallel seabed ridges and troughs. Seabed imagery shows that, in the western part of the central NDSF, short, arcuate undulations are associated with fluid venting (carbonate pavements, gas flares), while to the east, long, linear undulations have erosional furrows on their downslope flanks and fluid seeps are less common. Sub-bottom profiles suggest that the western undulations correspond to rotated fault-blocks above the buried MTDs, while those in the east are sediment waves generated by gravity flows. We suggest that fluids coming from dewatering of MTDs and/or from deeper layers generate overpressures along the boundary between MTDs and overlying fine-grained sediment, resulting in a slow downslope movement of the sediment cover and formation of tilted blocks separated by faults. Fluids can migrate to the seafloor, leading to the construction of carbonate pavements. Where the sediment cover stabilizes, sediment deposition by gravity flows may continue building sediment waves. These results suggest that complex processes may follow the emplacement of large MTDs, significantly impacting continental-slope evolution.
(Advances in Natural and Technological Hazards Research. vol. 37, pp. 117-127, 23/04/2026)
GEOAZUR 7329, INSU - CNRS, UniCA, CNRS, IRD [Occitanie], UniCA, OGS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Chronic dietary exposure of zebrafish to PAH mixtures results in carcinogenic but not genotoxic effects
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants that can be present at high levels as mixtures in polluted aquatic environments. Many PAHs are potent mutagens and several are well-known carcinogens. Despite numerous studies on individual compounds, little is known about the toxicity of PAHs mixtures that are encountered in environmental situations. In the presentwork, zebrafish were continuously fed from 5 days post-fertilisation to 14 months post-fertilisation (mpf) with a diet spiked with fractions of either pyrolytic (PY), petrogenic light oil (LO), or petrogenic heavy oil (HO) origin at three concentrations. A decrease in survival was identified after 3 mpf in fish fed with the highest concentration of HO or LO, but not for PY. All PAH fractions caused preneoplastic and neoplastic disorders in longterm-exposed animals. Target tissues were almost exclusively of epithelial origin, with the bile duct epithelium being themost susceptible to chronic exposure to all PAH fractions, and with germ cells being the second most responsive cells. Significantly higher incidences of neoplasms were observed with increasing PAH concentration and exposure duration. Themost severe carcinogenic effects were induced by dietary exposure to HO compared to exposure to LO or PY (45, 30 and 7 %, respectively, after 9 to 10 months of exposure to an intermediate concentration of PAHs). In contrast, earliest carcinogenic effects were detected as soon as 3 mpf after exposure to LO, including the lowest concentration, or to PY. PAHbioactivation and genotoxicity in blood was assessed by ethoxyresorufin-Odeethylase activity quantification and comet and micronuclei assays, respectively, but none of these were positive. Chronic dietary exposure of zebrafish to PAH mixtures results in carcinogenotoxic events that impair survival and physiology of exposed fish.
(Environmental Science and Pollution Research. vol. 21, n° 0944-1344, pp. 13833-13849, 23/04/2026)
PAnTher, ONIRIS, INRAE, UNAM, ONIRIS, LIENSs, INSU - CNRS, ULR, CNRS, BE, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LPGP, INRA, Biosit : Biologie - Santé - Innovation Technologique
Unexpected biotic resilience on the Japanese seafloor caused by the 2011 Tohoku-Oki tsunami
On March 11th, 2011 the Mw 9.0 2011 Tohoku-Oki earthquake resulted in a tsunami which caused major devastation in coastal areas. Along the Japanese NE coast, tsunami waves reached maximum run-ups of 40 m, and travelled kilometers inland. Whereas devastation was clearly visible on land, underwater impact is much more difficult to assess. Here, we report unexpected results obtained during a research cruise targeting the seafloor off Shimokita (NE Japan), shortly (five months) after the disaster. The geography of the studied area is characterized by smooth coastline and a gradually descending shelf slope. Although high-energy tsunami waves caused major sediment reworking in shallow-water environments, investigated shelf ecosystems were characterized by surprisingly high benthic diversity and showed no evidence of mass mortality. Conversely, just beyond the shelf break, the benthic ecosystem was dominated by a low-diversity, opportunistic fauna indicating ongoing colonization of massive sand-bed deposits.
(Scientific Reports. vol. 4, n° 2045-2322, pp. 7517, 23/04/2026)
JAMSTEC, LPG, UA, UN UFR ST, UN, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CEFREM, UPVD, INSU - CNRS, CNRS, CEREGE, IRD, INRA, AMU, CdF (institution), INSU - CNRS, CNRS, NIOZ, BIAF, UA
Chronic dietary exposure to pyrolytic and petrogenic mixtures of PAHs causes physiological disruption in zebrafish - part I: survival and growth
The release of polycyclic aromatic hydrocarbons (PAHs) into the environment has increased very substantially over the last decades leading to high concentrations in sediments of contaminated areas. To evaluate the consequences of long-term chronic exposure to PAHs, zebrafish were exposed, from their first meal at 5 days post fertilisation until they became reproducing adults, to diets spiked with three PAH fractions at three environmentally relevant concentrations with the medium concentration being in the range of 4.6–6.7 μg g−1 for total quantified PAHs including the 16 US-EPA indicator PAHs and alkylated derivatives. The fractions used were representative of PAHs of pyrolytic (PY) origin or of two different oils of differing compositions, a heavy fuel (HO) and a light crude oil (LO). Fish growth was inhibited by all PAH fractions and the effects were sex specific: as determined with 9-month-old adults, exposure to the highest PY inhibited growth of females; exposure to the highest HO and LO inhibited growth of males; also, the highest HO dramatically reduced survival. Morphological analysis indicated a disruption of jaw growth in larvae and malformations in adults. Intestinal and pancreatic enzyme activities were abnormal in 2-month-old exposed fish. These effects may contribute to poor growth. Finally, our results indicate that PAH mixtures of different compositions, representative of situations encountered in the wild, can promote lethal and sublethal effects which are likely to be detrimental for fish recruitment.
(Environmental Science and Pollution Research. vol. 21, n° 0944-1344, pp. 13804-13817, 23/04/2026)
BE, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEMAR, IRD, IFREMER, UBO EPE, CNRS, LIENSs, INSU - CNRS, ULR, CNRS, LRHLR, HGS, IFREMER, LPGP, INRA, Biosit : Biologie - Santé - Innovation Technologique
Developmental toxicity of PAH mixtures in fish early life stages. Part II: adverse effects in Japanese medaka
In aquatic environments, polycyclic aromatic hydrocarbons (PAHs) mostly occur as complex mixtures, for which risk assessment remains problematic. To better understand the effects of PAH mixture toxicity on fish early life stages, this study compared the developmental toxicity of three PAH complex mixtures. These mixtures were extracted from a PAH-contaminated sediment (Seine estuary, France) and two oils (Arabian Light and Erika). For each fraction, artificial sediment was spiked at three different environmental concentrations roughly equivalent to 0.5, 4, and 10 μg total PAH g−1 dw. Japanese medaka embryos were incubated on these PAH-spiked sediments throughout their development, right up until hatching. Several endpoints were recorded at different developmental stages, including acute endpoints, morphological abnormalities, larvae locomotion, and genotoxicity (comet and micronucleus assays). The three PAH fractions delayed hatching, induced developmental abnormalities, disrupted larvae swimming activity, and damaged DNA at environmental concentrations. Differences in toxicity levels, likely related to differences in PAH proportions, were highlighted between fractions. The Arabian Light and Erika petrogenic fractions, containing a high proportion of alkylated PAHs and low molecular weight PAHs, were more toxic to Japanese medaka early life stages than the pyrolytic fraction. This was not supported by the toxic equivalency approach, which appeared unsuitable for assessing the toxicity of the three PAH fractions to fish early life stages. This study highlights the potential risks posed by environmental mixtures of alkylated and low molecular weight PAHs to early stages of fish development.
(Environmental Science and Pollution Research. vol. 21, n° 0944-1344, pp. 13732-13743, 23/04/2026)
UB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LPGP, INRA, Biosit : Biologie - Santé - Innovation Technologique, BE, IFREMER
In situ oxygen and methane benthic fluxes measurements within isoetids meadows
Mesures des flux benthiques d'oxygène et méthane sur des pelouses à isoétides.
(pp. 13, 23/04/2026)
UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Quantitative estimate of the paleo-Agulhas leakage
The Indian-Atlantic water exchange south of Africa (Agulhas leakage) is a key component of the global ocean circulation. No quantitative estimation of the paleo-Agulhas leakage exists. We quantify the variability in interocean exchange over the past 640,000 years, using planktic foraminiferal assemblage data from two marine sediment records to define an Agulhas leakage efficiency index. We confirm the validity of our new approach with a numerical ocean model that realistically simulates the modern Agulhas leakage changes. Our results suggest that, during the past several glacial-interglacial cycles, the Agulhas leakage varied by ~10 sverdrup and more during major climatic transitions. This lends strong credence to the hypothesis that modifications in the leakage played a key role in changing the overturning circulation to full strength mode. Our results are instrumental for validating and quantifying the contribution of the Indian-Atlantic water leakage to the global climate changes.
(Geophysical Research Letters. vol. 41, n° 0094-8276, pp. 1238-1246, 23/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, VU, IFM-GEOMAR, GEOMAR, ICREA, ICTA, UAB
High-resolution morphobathymetric analysis and evolution of Capbreton submarine canyon head (Southeast Bay of Biscay French Atlantic Coast) over the last decade using descriptive and numerical modeling
n this study, the Capbreton canyon head, just off the coast, is investigated using high-resolution multibeam bathymetry datasets, sediment samples and numerical modeling. The HR bathymetty analysis reveals a morphological connection between the longshore trough and the head of the canyon. The analysis of recent sediment samples shows a clear correlation between the sediment of the canyon head and that of the nearshore. Hydrodynamic modeling (a coupled wave-flow model) shows that for high-energy waves, the rotational nature of surfzone circulation reverses and wave-induced currents have the potential to transport large quantities of nearshore sands toward the canyon head. All these arguments support the assumption that the canyon head captures a part of the sand transported by longshore drift. Over the 15 years of observation (1998-2013), time-lapse bathymetry shows that the floor of the canyon head and one lateral gully network experienced significant morphological reworking. In terms of hazards, despite this strong activity, the position of the canyon head and the profile of its longitudinal slope remained stable and appear as a comforting factor. However, the activity of unusual lateral erosions needs to be monitored.
(Marine Geology. vol. 351, n° 0025-3227, pp. 1-12, 23/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IFREMER, SHOM, BRGM
Le système Capbreton-Santander : illustration des processus sédimentaires actifs dans les canyons modernes depuis 15 000 ans
Le canyon de Capbreton se singularise des autres canyons du Golfe de Gascogne par sa proximité à la côte. La tête du canyon s’initie dès 30 mètres d’eau et donne naissance à un thalweg sinueux encaissé dans un canyon étroit aux flancs raides. Le thalweg de Capbreton s’étend sur plus de 270 km jusqu’à 3 000 mètres de profondeur où il connaît un brusque changement de direction vers le Nord pour se prolonger dans le canyon de Santander. A cette profondeur, le canyon de Santander présente une morphologie en U, plus large et moins haute que le canyon de Capbreton, illustrant la transition entre canyon profondément incisé et chenal profond. En parallèle de cette évolution morphologique, les différents carottages réalisés dans ces canyons illustrent une évolution de la dynamique sédimentaire depuis l’amont du canyon de Capbreton jusqu’à la terminaison du canyon de Santander. A 80 km de la tête du canyon de Capbreton, perpendiculaire au thalweg, un transect de quatre carottes illustre les différents processus en action dans le canyon sur une même verticale : (1) une sédimentation gravitaire en masse au c ?ur du thalweg, (2) des évènements turbiditiques fins sur les terrasses basses (< 200 m par rapport au thalweg), à une fréquence moyenne d’une turbidite/an lors des derniers 2 000 ans et (3) de la décantation liée aux nuages néphéloïdes, alimentés par les panaches turbides sur les terrasses hautes (> 200 m). Dans la terminaison du canyon de Santander, prélevée le long d’un méandre considéré jusqu’alors abandonné, une carotte montre 8 m de dépôts turbiditiques sableux dont l’analyse stratigraphique indique une alimentation continue au cours des derniers 15 000 ans, mais avec des taux de sédimentation holocènes 6 fois plus faibles que sur les terrasses du canyon de Capbreton. Ainsi même si le canyon de Capbreton, et plus particulièrement ses terrasses, fonctionnent comme de véritables pièges à sédiments régionaux, une part non négligeable de ses apports sédimentaires atteint tout de même les grands fonds à l’Holocène, ce qui est tout à fait singulier en comparaison des autres grands canyons du Golfe de Gascogne
(pp. 89, 23/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
On the use of the Radon Transform in studying nearshore wave dynamics
In the nearshore, describing the complex individual wave dynamics remains a key challenge. In this paper we test the ability of the Radon Transform to produce estimates of individual wave celerities and to separate incoming and outgoing waves conserving the temporal characteristics. The Radon Transform is a projection of a two-dimensional field into polar space. Oblique features such as propagating crests in a spatio-temporal space are identified with density peaks in the polar space. In this paper, the Radon Transform is applied to synthetic test cases including a wide range of beach slopes and wave conditions. The Radon Transform shows good skills at estimating individual celerity and separating incoming and outgoing components with a relative RMS error lower than 10%, even a standing wave node. The accuracy is fairly insensitive to wave characteristics whereas the main limitations rise from the sampling scheme and are the number and density of wave gauges. The distance between gauges should be less than one third of the shortest wavelength, while the set of gauges should cover more than one third of the longest wavelength.
(Coastal Engineering. vol. 92, n° 0378-3839, pp. 24-30, 23/04/2026)
LEGOS, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, LEGI, UJF, Grenoble INP, CNRS, PUC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS