Exploitation of trophic resources by fish under stressful estuarine conditions
Despite the high complexity and variability of estuaries, these ecosystems are very productive and play an important role in fish feeding. This paper constitutes a preliminary investigation to test how fish optimize the use of the available trophic resources, by studying trophic preference variability and feeding strategies of some pelagic and demersal fish in the Gironde estuary (southwest France). Fish and their prey were collected approximately every two months from July 2003 to June 2004 in the upstream area of the saline estuary. Stomach content analyses were realized to describe the variability of fish feeding according to their size and the time of year. Intra- and interspecific food niche overlap was evaluated using Schoener's index and a cross-calculation method was used to highlight the general fish trends in predation strategy. Stomach content results showed interspecific and intraspecific variability in fish feeding, which can be explained by their different or evolutionary ecomorphology. Their diets are composed mainly of zooplankton and hyperbenthic crustaceans with temporal variations in the consumed taxa. Optimization of the available trophic resource use, a key element in estuarine resilience, is thus possible due to the temporal adaptation of this structural trophic web. However, in spite of their temporal adaptation capacity, most fish species exhibited a specialist feeding strategy. This result was not expected, especially in the high turbidity of the Gironde estuary; the loss of one of these species could affect the fish trophic web structure and hence the resilience of the system.
(Marine Ecology Progress Series. vol. 400, n° 0171-8630, pp. p. 207 - p. 219, 27/10/2026)
UR EPBX, CEMAGREF, LIENSs, INSU - CNRS, ULR, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Live benthic foraminiferal faunas along a bathymetrical transect (140–4800 m) in the Bay of Biscay (NE Atlantic)
In a 10-stations bathymetrical transect in the Bay of Biscay, we observed important changes in the density, composition and microhabitats of live foraminiferal faunas from the outer continental shelf to the abyssal plain. Four zones are recognised: (1) at the upper continental shelf (140 m water depth), foraminiferal densities are very high and the superficial sediment is occupied by Bolivina subaenariensis and Valvulineria bradyana. Globobulimina spp., Chilostomella oolina and Nonion fabum dominate the infaunal niches, which are positioned close to the sediment–water interface due to a strong compaction of the vertical succession of redox zones. (2) At the upper continental slope stations (300–1000 m), foraminiferal densities are high and the superficial sediments are dominated by Uvigerina mediterranea/peregrina. Deeper in the sediment, intermediate infaunal niches are occupied by Melonis barleeanus. Due to a deeper oxygen penetration, the deep infaunal taxa Globobulimina spp. and C. oolina live at a considerable depth in the sediment. (3) At the mid and lower slope stations (1000–2000 m) in the superficial sediment Cibicidoides kullenbergi and Hoeglundina elegans progressively replace U. mediterranea. U. peregrina is still a dominant taxon, reflecting its preference for a somewhat intermediate organic flux level. Deep infaunal taxa become increasingly rare. (4) At the lower slope and abyssal plane stations (deeper than 2000 m), faunal densities are very low and the fauna is composed exclusively by shallow infaunal species, such as Nuttallides umboniferus and Melonis pompilioides. The foraminiferal data together with the pore water data in the sediment give evidence of the presence of a trophic gradient from very eutrophic settings at the upper continental shelf towards oligotrophic settings at the abyssal area.
(Revue de Micropaléontologie. vol. 53, n° 0035-1598, pp. 139 - 162, 27/10/2026)
LPGN, UN, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Spatial variability of live benthic foraminiferal faunas on the Portuguese margin
We investigated benthic foraminiferal densities, composition, and microhabitats at three sampling stations on the Portuguese margin, at 980, 1860 and 3125m water depth. For each site, we studied two sets of three replicate cores, sampled during two successive multi-corer deployments. Our results show an overall trend of decreasing foraminiferal densities from the shallowest to the deepest site, in response to a decreasing labile organic matter flux to the sea floor. Faunas at 980m are strongly dominated by Uvigerina mediterranea, which shows a conspicuous faunal density maximum close to the sediment surface. At 1860m, the surface faunas are much poorer, and no longer dominated by a single taxon. Cibicidoides robertsonianus, C. kullenbergi, Uvigerina peregrina, Gavelinopsis translucens and Hoeglundina elegans are present in about equal quantities. The deep infaunal community at these two stations is dominated by Globobulimina affinis, and has comparable densities. At 3125m, the faunas are very poor in 5 of the 6 cores, and mainly consist of agglutinant taxa. At all three stations, important differences are observed between the 6 studied cores. At 980m, the faunal density is about 4 times higher in one of the cores, mainly due to high numbers of Uvigerina mediterranea. This could be explained by the position of this core in a topographical depression, where organic matter concentrates. At 1860m, two sets of three cores, taken during two successive multicorer deployments, contain different amounts of deep infaunal taxa. Finally, at 3125m, one of the 6 cores contains an exceptionally rich deep infaunal community (up to 450 individuals per 50cm), dominated by the calcareous taxa Fursenkoina bradyi, Globobulimina affinis and Chilostomella oolina. The fact that the subrecent fossil faunas of three studied cores from this site are all enriched in these taxa indicates that the observed high infaunal standing stocks are a recurrent phenomenon, in response to a currently unidentified process that strongly concentrates metabolisable organic matter in deeper sediment layers.
(Micropaleontology. vol. 56, n° 0026-2803, pp. 297 - 322, 27/10/2026)
LPG-ANGERS, LPG, UA, UN UFR ST, UN, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Effect of dietary cadmium on lipid metabolism and storage of aquatic bird Carina moschata
In environment, birds often fast in connection with breeding, migration or drastic climatic conditions and need to mobilize lipid reserves during these periods. The impairment of lipid metabolism by cadmium (Cd; 1 mg kg(-1) added in diet) was investigated on palmiped Cairina moschata. Expression levels of genes involved in lipid metabolism, mitochondrial metabolism and detoxification were investigated in liver and muscle of ducks. Lipid content in muscle and liver were analysed and plasma triglycerides were quantified. After 20 days, ducks exposed to Cd displayed a lower body weight and lower lipid content in liver than controls. In muscle, the increase of lipid content was only significant for control ducks but not for exposed ducks. Exposed ducks appeared unable to sufficiently transport and store lipids into peripheral tissues. Cd impairs lipid metabolism by several ways. First, Cd triggered the down-regulation of fatty acids synthesis in liver even if the NADPH production and the mitochondrial metabolism are enhanced, suggesting a stronger energy needs. Secondly, the associated decrease of plasma triglycerides and lipoprotein lipase activity with Cd are consistent with impairment of lipids storage in peripheral tissues.
(Ecotoxicology, n° 0963-9292, pp. 163-170, 27/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UEPFG, INRA, IPREM, UPPA, INC-CNRS, CNRS
Recovery potential of periphytic biofilm exposed to industrial contamination: field and experimental studies
This study was conducted in a context of impacted hydrosystem remediation in France. The Gironde fluvio-estuarine system has been subjected to polymetallic pollution (Cadmium and Zinc) for over a century, coming from an industrial site specialized in zinc ore treatment carrying contaminated wastes into a small tributary, located about 400 km upstream from the estuary. Since 2007 a major remediation phase has been initiated in the industrial site. This study aims to assess first biological modifications due to remediation procedure on periphytic diatoms biofilms, dominant primary producers in freshwaters. Therefore a yearly biomonitoring of the contamination was conducted in situ through 24 days colonizations cycles along the pollution gradient. The experiments were renewed every 48 days during a year. Glass slides were exposed in three stations located upstream the industrial site and one station dowstream the factory (Joany). After 24 days of colonization the glass slides were scraped to collect biofilm. Different tests were then performed: analyses of metal bioaccumulation, taxonomic investigations, numerations of diatom densities and biomass, and Chlorophyll a concentrations, completed by physicochemical measurements in water. Cadmium and zinc bioaccumulation concentrations were discriminating factors for biofilms from Joany, reaching maximum concentrations in dry weights (DW) of 861 ± 387 μg Cd.g-1 and 21 256 ± 5 701 μg Zn.g-1. Joany biofilms presented high densities too and low BDI values in comparison with the three other stations of colonization, located upstream the industrial site probably in relation with the important nutrients concentrations at this station due to urban wastewaters. Moreover, special attention was devoted to abnormal forms in the taxonomic investigations as it is established in the literature that contaminants promote abnormal forms frequencies. Maximum abnormality rate was observed in biofilms from Joany with 12, value significantly higher compared to biofilm from the 3 other stations below 5. Consequently, initial results show yet a persistence of metallic contamination in situ and high bioaccumulation in biofilms located dowstream industrial site. However, remediation is already perceivable in comparison with previous studies in which bioaccumulation (DW) reached 1809 ± 200 μg Cd.g-1 and 23 750 ± 2 469μg Zn.g-1 after 24 days of colonization at Joany in August 2004. Regarding the frequency of abnormal forms, it remains in the same order of magnitude of 10 to 20 at Joany according to this previous study . To understand in a detailed and integrated way whether the periphytic biofilm can initiate total or partial recovery, laboratory decontamination experiments free of environmental variations have thus been developped. The aim was to characterize the kinetics of biofilm recovery under controlled conditions after in situ and artificial expositions to Cd and Zn following the same analysis criteria than used for in situ experiments. Firsts results have shown a rapid decrease of metallic bioaccumulation with a return to control concentrations after 14 days under recovery conditions. This kind of results suggests the resurgence of sensitive species and the decrease of abnormal forms frequencies and put out diatom biofilm as an appropriate model to reveal effective recovery of polluted freshwater ecosystems.
(pp. 2, 27/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR REBX, CEMAGREF
Distribution of the organic matter in the channel-levees systems of the Congo mud-rich deep-sea fan (West Africa). Implication for deep offshore petroleum source rocks and global carbon cycle
The Corinth Rift is superimposed on the Hellenic nappe stack that formed at the expense of the Apulian continental crust above the subducting African slab. Extension started in the Pliocene and the major steep normal faults that control the geometry of the present-day rift were born very recently, some 600 kyr ago only. They root into a shallow-dipping zone of microseismicity recorded near the base of the upper crust. The significance of this seismogenic zone is debated. Considering the northward dip of the zone of microseismicity, the depth of microearthquakes and their focal mechanisms, we observe a strong similarity with the northern Cycladic detachments in terms of expected pressure, temperature conditions and kinematics. We herein show (1) that the formation of the Corinth Rift can be considered a part of a continuum of extension that started some 30–35 Ma in the Aegean and that was recently localised in a more restricted area, (2) that the present-day structure and kinematics of the Corinth Rift can be explained with a series of decollements relayed by steeper ramps that altogether formed a mechanically weak, crustal-scale detachment, and (3) that the deformation, fluid behaviour and metamorphic features seen in the northern Cycladic metamorphic core complexes can be good analogues of the processes at work below the Corinth Rift.
(Marine and Petroleum Geology. vol. 27, n° 0264-8172, pp. 995–1010, 27/10/2026)
iSTeP, UPMC, CNRS, ISTO, INSU - CNRS, UO, UT, NEOLAiA, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GM, IFREMER
Laboratory experiment on rip current circulations over a moveable bed: Drifter measurements
This study describes a laboratory experiment on rip current circulations over a moveable bed. Rip current characteristics over eight contrasting nature-like beach morphologies are investigated. The seabed varied from reasonably alongshore uniform to strongly alongshore nonuniform with crescentic patterns and bar-rip morphologies, representative of a full morphological down-state sequence. The same offshore shore-normal waves were generated by the wavemaker for the eight situations with the same mean water level to study the sensitivity of rip current characteristics as a function of the beach morphology only. In each case, a 30 to 60 min video run was used to track a large number of drifters released within the surf zone. Results show the presence of classic rip current patterns with counterrotating cells and a relatively narrow offshore-directed jet varying from shore-normal to strongly skewed. Wave-driven circulations were strongly unstable. Computed standard deviations of flow intensity and direction provide high-resolution information on the spatial variability of rip current instabilities. Highly pulsating and weakly directionally variable offshore-directed flow is observed in the rip neck for well-developed bar-rip morphologies that turns into a weakly pulsating and highly directional variable rip current flow with decreasing beach alongshore nonuniformity. Proposing a definition of rip current intensity based on the rip current circulation geometry, rip current intensity was found to linearly increase with increasing measure of beach alongshore nonuniformity within both the low-energy and moderate-energy rip current regimes. To date, our laboratory experiment provides the first extensive quantitative rip current information during a full down-state sequence for a given wave condition.
(Journal of Geophysical Research. vol. 115, n° 0148-0227, pp. C12008, 27/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEGI, UJF, Grenoble INP, CNRS, Géosciences Montpellier, UAG, INSU - CNRS, UM, CNRS
Modélisation physique de la morphodynamique d'une plage barrée tridimensionnelle
Des expériences dans un bassin de 30 m x 30 m ont été réalisées dans l'objectif de caractériser la dynamique d'un courant d'arrachement et les évolutions morphologiques associées. La plage de sable fin (diamètre médian 166 microns) couvrait la largeur du bassin (30 m en longshore ) pour un profil total de 20 m cross-shore . La formation de courants sagittaux a été forcée par une houle frontale (spectre de Jonswap) avec un déficit d'énergie au centre du bassin. Une séquence accrétive complète de plage intermédiaire à simple barre (selon classification de WRIGHT & SHORT, 1984) a été reproduite. La barre s'est progressivement tridimensionnalisée en forme de croissant puis s'est connectée au haut de plage avec la présence de deux chenaux profonds qui se sont ensuite comblés pour obtenir une plage à terrasse au bout de plusieurs dizaines d'heures. L'association des mesures hydrodynamiques et morphodynamiques montre que le comblement des chenaux est alimenté par le haut de plage.
(pp. 45, 27/10/2026)
LEGI, UJF, Grenoble INP, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UAG, INSU - CNRS, UM, CNRS, UQAR, LSEET, INSU - CNRS, UTLN, CNRS
Changes in precipitation regimes over North America during the Holocene as recorded by mineralogy and geochemistry of Gulf of Mexico sediments
Changes in terrigenous-transfer patterns from North America toward the Gulf of Mexico via the Mississippi River during the Holocene were investigated using mineralogical and geochemical records from the northern Gulf of Mexico (Pigmy Basin). Clay mineralogy (smectite/illite + chlorite) and geochemical signatures (K and Ti intensities) indicate fluctuations in the detrital sedimentation during the Holocene in the Pigmy Basin. They likely reflect alternations between at least two dominant terrigenous sources: the smectite-rich NW Mississippi watershed, and the illite-and chlorite-rich Great Lakes province and NE Mississippi watershed. These recurring and rapid modifications of erosional processes over this period suggest changes in the hydrological regime via rainfall patterns. Such a modification during the Holocene is likely linked with the rapid atmospheric reorganization following the final collapse of the Laurentide Ice Sheet. Indeed, mineralogical and geochemical proxies indicate east-to-west migrations of the main detrital source (from the Great Lakes and northeastern province toward the northwestern province) associated with Mississippi River megaflood episodes. These modifications of the main detrital sources likely record migrations of the precipitation belt, which are constrained by atmospheric configuration (Jet Stream, Bermuda High and Intertropical Convergence Zone position) and subtropical oceanic hydrological properties (meridional extension of the Atlantic Warm Pool). In the frame of previously published rainfall patterns over the Caribbean and North America, our results highlight some marked modifications of moisture transfer throughout the Holocene. These changes are interpreted as resulting from two atmospheric configurations that have driven alternately the precipitation distribution over North America for the last 10 ka with an apparent cyclicity of~2.5 ka. The coherent common cyclicity between the Gulf of Mexico detrital parameters and Greenland atmospheric proxies over the Holocene suggests that the initial external forcing was rapidly transferred latitudinally through atmospheric processes.
(Global and Planetary Change. vol. 74, n° 0921-8181, pp. 132 - 143, 27/10/2026)
CNRS, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], IUEM, IRD, INSU - CNRS, UBO EPE, CNRS, USF, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Structural vs functional approaches: A first comparison between WFD indicators and Ecological Network Analysis indices on French estuaries
At summary: general context, issue indicators, material and methods data, results.
(pp. 22, 27/10/2026)
UR EPBX, CEMAGREF, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LIENSs, INSU - CNRS, ULR, CNRS