Variations in benthic foraminiferal assemblages in the Tagus mud belt during the last 5700 years: Implications for Tagus River discharge
We analyzed a 10-m sediment core retrieved at 82 m water depth off the coast of the Tagus River (Western Iberian Margin, Portugal) to investigate a linkage between variations in benthic foraminiferal assemblages and Tagus River discharge over the last 5700 years. Benthic foraminiferal assemblages were studied at high resolution in combination with the stable carbon and oxygen isotopic composition of fossil shells of Nonion scaphum, bulk and molecular organic matter properties (TOC, TN, C/N ratio, delta C-13(TOC), delta N-15(bulk), and BIT index), magnetic susceptibility, and XRF analyses. Three periods of environmental changes were identified: 1) high Tagus River discharge in 5750-2200 calendar year before present (cal yr BP), 2) lower discharge characterized by intense upwelling conditions (2250-1250 cal yr BP), and 3) both intense upwelling and Tagus River discharge (1250 cal yr BP-present). The data reveal alternating intense upwelling periods, as shown by the dominance of Cassidulina carinata, Valvulineria bradyana, or Bulimina marginata, whereas periods of increased river discharge are indicated by increase of N. scaphum, Ammonia beccarii, and Planorbulina mediterranensis. The Tagus River discharge was the strongest during the first period, transporting riverine material further offshore and preventing the establishment of a mud belt on the mid-shelf (around 100 m depth). During the second period, a decrease in Tagus River discharge favored the formation of the Tagus mud belt and strongly influenced the benthic environment by creating an organic matter stock. During the third period, intense upwelling and increased Tagus River discharge were recorded by benthic foraminiferal distribution, with an increase of terrestrial elements present in the mud belt. Furthermore, our results showed that variations in benthic foraminiferal assemblages corresponded to the well-known climatic periods in the study area, such as the Roman Period, the Dark Ages, the Medieval Warm Period, and the Little Ice Age. Our study strongly suggests that benthic foraminiferal assemblages can be used as a bio-indicator to trace the influence of past river discharge.
(Palaeogeography, Palaeoclimatology, Palaeoecology. vol. 496, n° 0031-0182, pp. 225-237, 20/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LGO, UBS, IFREMER, UBO EPE, CNRS, LEMAR, IRD, IFREMER, UBO EPE, CNRS, NIOZ
Nouvelles recherches sur le site de la Lède du Gurp (Grayan-et-l’Hôpital, Gironde) : résultats préliminaires
Face à la destruction inéluctable des derniers niveaux archéologiques de la Lède du Gurp par l’érosion littorale, une opération de fouille a été menée en 2014. Ce site de référence présente une stratigraphique exceptionnelle, presque continue du 9e au 1er millénaire av. J.-C. Plusieurs tranchées de diagnostic ont permis d’identifier les différentes phases d’occupation dont la chronologie a été établie à partir du croisement des études du mobiliers et de dates radiocarbones. La découverte de structures aménagées (fosses, clayonnages) et d’abondants rejets (céramiques, faune) indiquent une fréquentation des lieux importante à la fin du Néolithique moyen (Chasséen), au Néolithique récent I (culture Matignons) et II (Peu-Richard maritime) -probablement liée à l’exploitation du sel-, ainsi qu’au Bronze ancien-moyen. Une étude paléoparasitologique a pu être réalisée grâce à la conservation des éléments organiques en milieux humides.
(pp. 209-220, 20/06/2026)
UBM, CNRS, TRACES, EHESS, UT2J, Comue de Toulouse, MCC, Inrap, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CReAAH, UM, UR, UR2, CNRS, UFR HHAA, UN, MC
Manganese incorporation in living (stained) benthic foraminiferal shells: a bathymetric and in-sediment study in the Gulf of Lions (NW Mediterranean)
Manganese geochemistry in deep-sea sediments is known to vary greatly over the first few centimeters, which overlaps the in-sediment depth habitats of several benthic foraminiferal species. Here we investigated manganese incorporation in benthic foraminiferal shell carbonate across a six-station depth transect in the Gulf of Lions, NW Mediterranean, to unravel the impacts of foraminiferal ecology and Mn pore water geochemistry. Over this transect water depth increases from 350 to 1987m, while temperature ( ∼ 13°C) and salinity ( ∼ 38.5) remained relatively constant. Manganese concentrations in the tests of living (rose bengal stained) benthic foraminiferal specimens of Hoeglundina elegans, Melonis barleeanus, Uvigerina mediterranea, and Uvigerina peregrina were measured using laser ablation inductively coupled mass spectrometry (laser ablation ICP-MS). Pore water manganese concentrations show a decrease from shallow to deeper waters, which corresponds to a generally decreasing organic-matter flux with water depth. Differences in organic-matter loading at the sediment–water interface affects oxygen penetration depth into the sediment and hence Mn pore water profiles. Mn∕Ca values for the investigated foraminiferal species reflect pore water geochemistry and species-specific microhabitat in the sediment. The observed degree of variability within a single species is in line with known ranges in depth habitat and gradients in redox conditions. Both the Mn∕Ca ratio and interspecific variability hence reflect past Mn cycling and related early diagenetic processes within the sediment, making this a potential tool for bottom-water oxygenation and organic-matter fluxes. Dynamics of both in-sediment foraminiferal depth habitats and Mn cycling, however, limit the application of such a proxy to settings with relatively stable environmental conditions.
(Biogeosciences. vol. 15, n° 1726-4170, pp. 6315-6328, 20/06/2026)
LPG-ANGERS, LPG, UA, UN UFR ST, UN, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
High-Content Screening of Plankton Alkaline Phosphatase Activity in Microfluidics
One way for phytoplankton to survive orthophosphate depletion is to utilize dissolved organic phosphorus by expressing alkaline phosphatase. The actual methods to assay alkaline phosphate activity—either in bulk or as a presence/absence of enzyme activity—fail to provide information on individual living cells. In this context, we develop a new microfluidic method to compartmentalize cells in 0.5 nL water-in-oil droplets and measure alkaline phosphatase activity at the single-cell level. We use enzyme-labeled fluorescence (ELF), which is based on the hydrolysis of ELF-P substrate, to monitor in real time and at the single-cell level both qualitative and quantitative information on cell physiology (i.e., localization and number of active enzyme sites and alkaline phosphatase kinetics). We assay the alkaline phosphatase activity of Tetraselmis sp. as a function of the dissolved inorganic phosphorus concentration and show that the time scale of the kinetics spans 1 order of magnitude. The advantages of subnanoliter-scale compartmentalization in droplet-based microfluidics provide a precise characterization of a population with single-cell resolution. Our results highlight the key role of cell physiology to efficiently access dissolved organic phosphorus.
(Analytical Chemistry. vol. 90, n° 0003-2700, pp. 4174 - 4181, 20/06/2026)
CRPP, UB, INC-CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
On the influence of reflection over a rhythmic swash zone on surf zone dynamics
The reflection of incident gravity waves over an irregular swash zone morphology and the resulting influence on surf zone dynamics remains mostly unexplored. The wave-phase resolving SWASH model is applied to investigate this feedback using realistic low-tide terraced beach morphology with well-developed beach cusps. The rhythmic reflection generates a standing wave that mimics a subharmonic edge wave, from the superimposition of incident and two-dimensional reflected waves. This mechanism is enhanced by shore-normal, narrow-banded waves in both direction and frequency. Our study suggests that wave reflection over steep beaches could be a mechanism for the development of rhythmic morphological features such as beach cusps and rip currents.
(Ocean Dynamics. vol. 68, n° 1616-7341, pp. 899-909, 20/06/2026)
LEGOS, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Intraspecific trade-offs between facilitation and competition in the non-native mollusc Crepidula fornicata
We tested the hypothesis that high-density populations of the non-indigenous gastropod Crepidula fornicata increase settlement of conspecific recruits (facilitation process), and that this facilitation is balanced by competition processes. To verify our hypothesis, we sampled C. fornicata at 2 drastically different densities for 10 yr. We found that at high densities, the number of 1 yr old individuals per square meter colonizing the habitat and individual growth performances were higher in comparison with the low-density condition (Allee effect). In contrast, the production/biomass ratio (P/B), a good indicator of population fitness, was lower at higher densities. We relate this lower P/B ratio to the deficit of young individuals compared to adult biomass. We conclude that the net effect of high density on the conspecific colonization processes of the population is positive, thanks to the higher available hard substrate for larvae (facilitation). However, intraspecific competition also occurs and mitigates this positive effect. Therefore, we suggest that it is particularly important to take into account the ‘net’ balance between costs and benefits (i.e. what we observe) when analyzing population growth, in order to better understand its dynamics.
(Marine Ecology Progress Series. vol. 604, n° 0171-8630, pp. 163-171, 20/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UMN, UMN
Le Golfe de Gascogne: zone clef pour tester les fonctions de transfert d´eriv´ees des microfossiles planctoniques
(20/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, HESAM, LPG-ANGERS, LPG, UA, UN UFR ST, UN, INSU - CNRS, CNRS
Développement et validation d'une méthode d'analyse des chloroalcanes à chaine courte et moyenne dans le biote. Application à la détermination de l'état de contamination de tissus de poissons d'eau douce
La Directive 2013/39 /UE modifiant les Directives 2000/60/CE et 2008/105/CE concernant les substances prioritaires dans le domaine de l'eau a introduit quinze nouvelles substances prioritaires au niveau communautaire, et promulgué les normes de qualité environnementale (NQE) correspondantes. Parmi les substances récemment introduites, on trouve les chloroalcanes dits « à chaine courte » (C10 à C13), constitués de mélanges complexes de n-alcanes polychlorés, composés répondant aux critères PBT (persistants, bioaccumulables et toxiques). Ces composés, ainsi que les chloroalcanes à chaine moyenne (C14-C17) et longue (C20-C30), sont hydrophobes, chimiquement et thermiquement stables, sont ou ont été employés dans de nombreuses applications industrielles. Les données existantes suggèrent le caractère ubiquiste de ces composés produits en quantité importantes à l'échelle globale ; ces données demeurent néanmoins relativement fragmentaires en raison de la difficulté à analyser et quantifier ces composés. Les travaux réalisés dans le cadre de cette étude ont permis le développement et la validation d'une méthode de dosage des chloroalcanes à chaine longue et moyenne dans les tissus de poisson. Cette méthode repose sur l'utilisation de l'extraction assistée par micro-ondes, sur la purification des extraits organiques par chromatographie d'adsorption et sur l'utilisation de la chromatographie en phase gazeuse couplée à la spectrométrie de masse haute résolution de type « temps de vol » (résolution de 15000 à m/z = 400) pour la détection des analytes. L'optimisation de la méthode a permis l'obtention de limites de détection dans la gamme 0,03-0,4 ng.g-1 pf pour les différents groupes (CnH2n+2-zClz), compatibles avec les niveaux environnementaux attendus. L'application de cette méthode à l'analyse de tissus de poisson (barbeau) prélevés dans le bassin du Rhône a permis de confirmer le caractère ubiquiste de ces micropolluants ; dans les échantillons sélectionnés, les niveaux de MCCP (1,25 - 72,7) apparaissent 2 à 57 fois plus élevés que ceux des SCCP (0,16 - 10,6 ng.g-1 poids frais), ces derniers étant systématiquement inférieurs à la NQEbiote applicable aux SCCP (16,6 µg.g-1 pf).
(pp. 19, 20/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IRSTEA
Microbial Dark Matter Investigations: How Microbial Studies Transform Biological Knowledge and Empirically Sketch a Logic of Scientific Discovery
Microbes are the oldest and most widespread, phylogenetically and metabolically diverse life forms on Earth. However, they have been discovered only 334 years ago, and their diversity started to become seriously investigated even later. For these reasons, microbial studies that unveil novel microbial lineages and processes affecting or involving microbes deeply (and repeatedly) transform knowledge in biology. Considering the quantitative prevalence of taxonomically and functionally unassigned sequences in environmental genomics data sets, and that of uncultured microbes on the planet, we propose that unraveling the microbial dark matter should be identified as a central priority for biologists. Based on former empirical findings of microbial studies, we sketch a logic of discovery with the potential to further highlight the microbial unknowns.
(Genome Biology and Evolution. vol. 10, n° 1759-6653, pp. 707 - 715, 20/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, AIRE, UAG, UPMC, UNS, CNRS
Quantitative comparison of taxa and taxon concepts in the diatom genus Fragilariopsis : a case study on using slide scanning, multiexpert image annotation, and image analysis in taxonomy 1
Semiautomated methods for microscopic image acquisition, image analysis, and taxonomic identification have repeatedly received attention in diatom analysis. Less well studied is the question whether and how such methods might prove useful for clarifying the delimitation of species that are difficult to separate for human taxonomists. To try to answer this question, three very similar Fragilariopsis species endemic to the Southern Ocean were targeted in this study: F. obliquecostata, F. ritscheri, and F. sublinearis. A set of 501 extended focus depth specimen images were obtained using a standardized, semiautomated microscopic procedure. Twelve diatomists independently identified these specimen images in order to reconcile taxonomic opinions and agree upon a taxonomic gold standard. Using image analyses, we then extracted morphometric features representing taxonomic characters of the target taxa. The discriminating ability of individual morphometric features was tested visually and statistically, and multivariate classification experiments were performed to test the agreement of the quantitatively defined taxa assignments with expert consensus opinion. Beyond an updated differential diagnosis of the studied taxa, our study also shows that automated imaging and image analysis procedures for diatoms are coming close to reaching a broad applicability for routine use.
(European Journal of Phycology. vol. 54, n° 0967-0262, pp. 703-719, 20/06/2026)
AWI, BAS, NERC, UNLP, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, MPI-BGC