Temporal variability in phytoplankton pigments, picoplankton and coccolithophores along a transect through the North Atlantic and tropical southwestern Pacific
Biogeochemical processes in the sea are triggered in various ways by chlorophyll-containing phytoplankton groups. While the variability of chlorophyll concentration at sea has been observed from satellites for several years, these groups are known only from cruises which are limited in space and time. The Geochemistry, Phytoplankton and Color of the Ocean programme (GeP&CO) was set up to describe and understand the variability of phytoplankton composition on large spatial scales under a multi-year sampling strategy. It was based on sea-surface sampling along the route of the merchant ship Contship London which travelled four times a year from Le Havre (France) to Noumea (New Caledonia) via New York, Panama and Auckland. Observations included the measurement of photosynthetic pigments, counts of picoplanktonic cells by flow cytometry (Prochlorococcus, Synechococcus, and picoeucaryotes) and counting and identification of coccolithophores. The results confirmed that tropical areas have low seasonal variability and are characterized by relatively high divinyl-chlorophyll a and zeaxanthin concentration and that the variability is strongest at high latitudes-where the phytoplankton biomass and population structure are found to have large seasonal cycles. Thus, the spring bloom in the North Atlantic and an austral winter bloom north of New Zealand are marked by chlorophyll concentrations which are often higher than 0.5 mu g l(-1) and by high concentration of fucoxanthin (a pigment used as an indicator for diatoms), while summer populations are dominated by Prochlorococcus sp. and have low chlorophyll concentrations. Apart from this yearly bloom at temperate latitudes, fucoxanthin is scarce, except in the equatorial upwelling zone in the eastern Pacific Ocean, where it is found in moderate amounts. In this region, relatively high chlorophyll concentrations extend generally as far as 14 degrees S and do not respond to the seasonal strengthening of the equatorial upwelling during the austral winter. Prochlorococcus, which is known to dominate in oligotrophic tropical seas and to disappear in cold conditions, in fact has its minimum during the spring bloom in the North Atlantic, rather than during the winter. Coccolithophores are ubiquitous, showing a succession of species ill response to oceanic conditions and provinces. 19'Hexanoyloxyfucoxanthin, the pigment generally considered as all indicator of coccolithophores, is relatively abundant at all times and in all regions, but its abundance is generally not tightly correlated with that of coccolithophores. The regional differences revealed by these results are in overall agreement with Longhurst's division of the ocean into ecological provinces. (c) 2006 Elsevier Ltd. All rights reserved.
(Deep Sea Research Part I: Oceanographic Research Papers. vol. 53, n° 0967-0637, pp. 689-712, 24/10/2026)
LOCEAN, IPSL, ENS-PSL, PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, IP Paris, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, CYROCO, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LOBB, OOB, UPMC, CNRS, UPMC, INSU - CNRS, CNRS
TRACE FOSSILS FROM NEARSHORE TO OFFSHORE ENVIRONMENTS: LOWER DEVONIAN OF BOLIVIA
Abundant and diverse trace fossils occur in deposits, recording an Early Devonian transgression in Bolivia. The very well-exposed Presto-El Peral section is located in the Interandean Belt 50 km northeast of Sucre. Trace fossils can be assigned to five associations from nearshore to offshore environments (namely Skolithos, Diplocraterion, Altichnus, Palaeophycus, and Zoophycos associations). They clearly illustrate the different colonization phases of the benthos with increasing marine influence. A deeper-water Helminthopsis association occurs in other complementary sections on the Eastern Cordillera. Variation of bioturbation intensity, ichnodiversity, and preservation potential is evaluated. The morphology of traces, mainly deep burrows, shows a significant gradient related to the behavior of tracemakers and the environmental changes. Main trends are consistent with the Seilacherian bathymetric model which is detailed here and/or emended with a well-exposed field example. A precise correlation is proposed with fossil benthic associations dominated by brachiopods. The whole gives an accurate model for benthos colonization and benthic marine zonation
(Journal of Paleontology. vol. 80, n° 0022-3360, pp. 1205-1226, 24/10/2026)
PEPS, UCBL, INSU - CNRS, CNRS, LDO, INSU - CNRS, UBO EPE, CNRS
Cytochrome c Oxydase Subunit I Gene is Up-regulated by Cadmium in Freshwater and Marine Bivalves
Inhibition of the mitochondrial electron transfer chain and induction of reactive oxygen species (ROS) production are one of the roots of cadmium (Cd) toxicity. To appreciate the impact of Cd on mitochondria, we focused on the expression of CoxI gene which encodes the subunit I of the Cytochrome c oxidase (complex IV of the respiratory chain). CoxI gene expression was studied by real-time quantitative PCR in three species: two freshwater bivalves (Corbicula fluminea and Dreissena polymorpha) and one marine bivalve (diploid or triploid Crassostrea gigas). Bivalves were exposed for 10 or 14 days to 0.13 μM Cd$^2$$^+$ and 15.3 μM Zn$^2$$^+$ in controlled laboratory conditions. We demonstrate that in the three mollusk species CoxI gene was up-regulated by Cd. Zinc (Zn), which is known to have antioxidant properties, had no effect on CoxI gene expression. In the presence of Cd and Zn, CoxI gene inducibility was lower than after a single Cd exposure, in each species; result that could not be fully explained by a decreased Cd accumulation. CoxI gene induction by Cd was 4.8-fold higher in triploid oysters than in diploid ones, indicating a possible influence of triploidy on animal responses to Cd contamination.
(BioMetals. vol. 19, n° 0966-0844, pp. 237-244, 24/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Metallothionein gene identification and expression in the cockle ( Cerastoderma edule) under parasitism (trematodes) and cadmium contaminations
Among benthic organisms, bivalves are often used as bioindicators of environmental pollution because of their high bioaccumulation capacities for heavy metals leading to metallothioneins (MT) induction. MT are small cytosolic metal-binding proteins involved in metal homeostasis and detoxification in living organisms. These proteins can also be induced by a wide range of factors, such as hormones, physical stress, parasitism. MT quantification in relation to parasitism is rarely reported in literature, while parasites are omnipresent and have deleterious impacts on bivalves. Moreover, only a few number of MT genes have been characterized in molluscs. This study describes the partial sequence of the MT gene (Cemt1) in the edible cockle Cerastoderma edule. The cockle's MT cDNA was sequenced and showed over 80% homology to several other bivalve MT sequences. This sequence was then used to determine MT specific primers which can be used in quantitative real time PCR. MT protein and gene expression levels were quantified for individuals selected under different conditions: free from or infected by the digenean trematode Himasthla elongata, and under cadmium exposure at 15 mu g Cd L-1. Results evidenced that MT concentrations were significantly increased by both treatments; parasite infection and Cd exposure. Moreover, congruent results between MT protein and gene expression levels were obtained.
(Aquatic Living Resources. vol. 20, n° 0990-7440, pp. 43-49, 24/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Le tuf de Caours (Somme, France) : mise en évidence d'une séquence eemienne et d'un site paléolithique associé
Les nouvelles investigations menées sur les tufs du bassin de la Somme dans le cadre du programme SITEP (CNRS) ont permis de mettre en évidence une formation tufacée reposant sur une nappe alluviale en position de très basse terrasse à Caours (Scardon). La séquence de tufs est sé-parée de la nappe alluviale périglaciaire sous-jacente par des limons fluviatiles calcaires se terminant par un petit sol de marais coiffé par un liseré de tourbe compactée. La formation tufacée proprement dite comporte essentiellement des faciès palustres à nombreux restes végétaux encroûtés en place et des concrétions travertineuses de type stromatolithes. En direction de la vallée actuelle l'ensemble passe rapidement à des faciès nettement fluviatiles à oncolithes structurés en grandes lentilles à stratifications obliques. La séquence de tuf ainsi que les limons fluviatiles ont livré une abondante faune malacologique qui a permis de décrire une évolution climatique contemporaine des phases initiales d'un interglaciaire, suivi d'un optimum climatique, puis d'une phase de réouverture du milieu exprimant le déclin des conditions tempérées. La base du tuf comporte plusieurs horizons organiques qui ont livré des restes de grands mammifères et de rongeurs contemporains de l'optimum interglaciaire déterminé par les assemblages malacologiques. Dans ces horizons, plusieurs niveaux du Paléolithique moyen ont été découverts en place, en association avec des restes de grande faune interglaciaire fortement fracturés par l'action de l'homme et présentant des traces de découpe. Compte tenu de sa position dans le sys-tème de la Somme, des datations par U/Th obtenues sur le tuf (moyenne : ± 120 ka BP) et des conclusions des études bioclimatiques, la séquence de Caours représente le premier témoin de l'interglaciaire Eemien en contexte fluviatile dans le bassin de la Somme. Enfin, les niveaux archéologiques découverts à Caours constituent un exemple unique d'occupation humaine contemporaine du dernier interglaciaire dans la France septentrionale.
(Quaternaire. vol. 17, n° 1142-2904, pp. 281--320, 24/10/2026)
LGP, UP1, UPEC UP12, CNRS, Evo-Eco-Paléo (EEP), CNRS, Inrap, PEQENO, CNRS, GEOTOP, EPM, UdeM, UQAT, UQAR, UQAM, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, OCEANIS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, HQMC, MNHN, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IRAMAT, UTBM, UO, UBM, CNRS, GEOTRAC, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, MNHN, CNRS
DNA adduct measurements in zebra mussels, Dreissena polymorpha Pallas. Potential use for genotoxicant biomonitoring of fresh water ecosystems
(Aquatic Toxicology. vol. 79, n° 0166-445X, pp. 55-64, 24/10/2026)
ANTICIPE, UNICAEN, NU, CHU Caen Normandie, NU, UNICANCER/CRLC, NU, INSERM, UNICANCER/CRLC, NU, UB, UB, GRECAN, UNICAEN, NU, UNICANCER/CRLC, NU, ABTE, UNICAEN, NU, UNIROUEN, NU, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Support of Subtidal Tracer Studies to Quantify the Complex Morphodynamics of a River Outlet: the Bevano, NE Italy.
Evolution of tidal inlets or river outlets has been widely described all over the world. However, most conceptual models are based on the long term perspective and field measurements to confirm these evolution schemes are scarce. The objective of the present study is to quantify the processes occurring at a small river outlet, the Bevano, during fair weather conditions. Subtidal fluorescent sand tracer method involving a new detection tool were used in the inlet and along the adjacent coast to assess sediment transport and bypassing processes. At the river mouth, sediment fluxes confirm an efficient bypass of sand through the inlet's channel. However, this sediment transport is combined with migration processes of the channel (40min 2 months), and yields a self-alimentation of both updrift and downdrift coasts. As it has already been observed at small tidal inlets, migration of the Bevano river mouth results from the erosion of the downdrift coast, and readjustment of the cross-section by the longshore transport on the updrift coast. The detection device used for subtidal tracing has given encouraging results and will be improved in order to work in more dynamic environments.
(Journal of Coastal Research. vol. SI39, n° 0749-0208, pp. 602-606, 24/10/2026)
UniFE, BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Contributions respectives des courants et de la houle dans la mobilité sédimentaire d'une plate-forme interne estuarienne. Exemple : le seuil interinsulaire, au large du pertuis d'Antioche, France. Respective contributions of currentsnext term and swell to the sediment mobility in an internal estuarine platform. Example of the inner shelf seaward of the ‘pertuis Charentais', France
Respective contributions of currents and swell to the sediment mobility in an internal estuarine platform. Example of the inner shelf seaward of the ‘pertuis Charentais', France. This paper investigates the relative influence of waves, wind-induced current and tidal current on the sediment mobility of a macro-tidal environment belonging to the inner shelf seaward of the ‘pertuis Charentais' (France). This study, mainly based on three-week hydrodynamic in-situ measurements, shows that, for a water depth of 23 m, the swell (rather than wind waves) orbital velocity is large enough to initiate the motion of medium sands that are then transported by currents. Estimations show that medium sand of 0.2 mm is transported during 92% of the measurements, whereas coarse sand and gravel move sporadically, during storm, synchronously with spring tides. Further more, bedload fluxes appear strongly larger when waves are taken into account (370 times larger for 0.2-mm sands)
(Comptes Rendus. Géoscience. vol. 338, n° 1631-0713, pp. 718-726, 24/10/2026)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CLDG, ULR
Tsunami Deposits Related to Flank Collapse in Oceanic Volcanoes: The Agaete Valley Evidence, Gran Canaria, Canary Islands
(Marine Geology. vol. 227, pp. 135--149, 24/10/2026)
GEOLAB, UBP, IR SHS UNILIM, UNILIM, UCA [2017-2020], CNRS, UCA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LGP, UP1, UPEC UP12, CNRS, DIMAR, UFPE
Le tuf calcaire de la Celle-sur-Seine (Seine et Marne): nouvelles données sur un site clé du stade 11 dans le Nord de la France.
De nouvelles études morphostratigraphiques et biostratigraphiques ainsi que des datations ont été entreprises sur le célèbre dépôt de tuf calcaire de La Celle‑sur‑Seine afin d’obtenir une reconstruction détaillée des successions paléoenvironnementales et climatiques enregistrées dans cette formation interglaciaire du Pléistocène moyen. L’approche développée a privilégié l’aspect pluridisciplinaire afin d’exploiter la richesse paléontologique du gisement, de mieux appréhender ses caractères morphostratigraphiques et de préciser sa position chronologique. Les premiers résultats obtenus à partir des études malacologiques montrent que le dépôt, composé de tufs et de niveaux limono‑argileux, s’est construit en progradant le long du versant. Ainsi l’épaisseur totale de la formation atteint près de 9 mètres. Les malacofaunes permettent de reconstituer une évolution paléoenvironnementale correspondant au début puis à l’optimum d’une phase climatique interglaciaire. Les niveaux sommitaux sont, eux, caractérisés par un net recul de la couverture forestière. La création de nouveaux profils stratigraphiques a permis la découverte dans un niveau de limon gris tufacé d’une abondante faune de mammifères accompagnée par quelques silex taillés. Cet horizon appartient à la malacozone la plus riche en taxons thermophiles qui est interprétée comme la phase optimum de l’Interglaciaire. La signification environnementale et climatique du cortège mammalogique, qui comprend en particulier de l’hippopotame et du macaque, corrobore les résultats malacologiques. L’industrie lithique est de type bifacial en cohérence avec les récoltes de bifaces acheuléens effectuées à la fin du 19e siècle. La composition du cortège de mollusques permet de rapprocher la faune de La Celle de « l’assemblage à Lyrodiscus », caractéristique des tufs du stade 11 dans le Nord‑Ouest de l’Europe. Cette attribution chronologique est confirmée par les premières mesures radiométriques obtenus par U‑Th sur des échantillons de tuf induré et par RPE/U‑Th sur une dent de cheval. Enfin la révision des collections paléontologiques d’empreintes foliaires permet, en conjonction avec les données malacologiques, d’initier la discussion sur l’interprétation paléoclimatique du biome à Lyrodiscus. L’association floristique et faunique de La Celle qui comprend quelques taxons arboréens méditerranéens et nombre de gastéropodes éteints ou de répartition actuelle centre‑européenne et océanique rend compte d’un environnement tempéré de forêt humide. La présence de ces espèces allochtones dans le Nord de la France est mise en parallèle avec la durée exceptionnellement longue du Stade Isotopique Marin (SIM) 11 et de faibles amplitudes de températures saisonnières, qui auraient permis à plusieurs taxons méridionaux de coloniser cette zone septentrionale, plutôt qu’avec un climat plus tempéré que l’actuel.
(pp. 17(2) : 5-29, 24/10/2026)
LGP, UP1, UPEC UP12, CNRS, PEQENO, CNRS, HQMC, MNHN, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, MNHN, UPMC, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA