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, 11/04/2026)
LPGN, UN, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
A method to calculate sediment fluxes from infrequent data: application to 65 rivers of the French river quality database
Improving knowledge of sediment exports represents one major challenge for environmental sciences considering their role in geochemical cycles and their link with Earth's surface processes. Because suspended sediment (SS) fluxes in rivers reflect the integration of combined erosion, transport and deposition processes that occur within the drained area, their calculation is thus essential in surface processes studies. Suspended sediment fluxes are estimated from discharge measurements and SS concentrations, either by averaging methods or by predicting sediment concentration values from continuous discharge data. In the latter case, a power function (or power law relation) is often defined between the observed SS concentrations and the corresponding discharge data. However it seems unrealistic to consider a single relation between SS concentrations and river discharges. The reason is hat sediment production processes are not homogeneous in time, showing local and seasonal effects for example in agricultural areas where land cover varies inside a year or in mountainous regions where snow melting has a strong influence. Moreover, these processes are also spatially heterogeneous, due to spatial patterns in landscape characteristics, meteorological phenomena and geomorphology. In addition, important gaps persist when calculating SS fluxes, mainly due to SS measurements are not always carried out with high frequency. Based on 65 river basins in France, with various sizes, geomorphologies and land uses, this study aims at testing methods for an estimation of annual sediment loads, based on infrequent SPM concentration data spanning over several decades.
(pp. 12206-1, 11/04/2026)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, SISYPHE, UPMC, EPHE, PSL, PSL, CNRS
Zooplankton community structure in a highly turbid environment (Charente estuary, France): Spatio-temporal patterns and environmental control
Zooplankton assemblages were studied from January 2007 to January 2008 along the salinity gradient of the Charente estuary (France). A Lagrangian survey was performed monthly at five sampling stations defined by salinity (freshwater, 0.5, 5, 15 and 25) in order to collect zooplankton and measure the main environmental parameters (concentrations of suspended particulate matter, particulate organic carbon, chlorophyll a and phaeopigments). A combination of multivariate cluster analysis, species indicator index and canonical correspondence analysis was used to relate the spatio-temporal patterns of the zooplankton assemblages with environmental drivers. The estuary was divided into three different zones by means of environmental parameters while four zooplankton assemblages were identified along the salinity gradient. The Charente estuary appeared as one of the most turbid systems in Europe, with suspended particulate matter (SPM) concentration reaching 3.5 g l-1 in the Maximum Turbidity Zone (MTZ). Algal heterotrophy and microphytobenthos resuspension from the wide mudflats could be responsible for the relatively high chlorophyll a concentrations measured within this MTZ. Salinity and SPM affected significantly the spatial distribution of zooplankton species while temperature and river flow seemed to control their temporal variations. From a zooplanktonic viewpoint, the highly turbid Charente estuary seemed to match an "ecotone-ecocline" model: the succession of species assemblages along the salinity gradient matched the concept of ecocline while the MTZ, which is a stressful narrow area, could be considered as an ecotone. Although such ecoclinal characteristics seemed to be a general feature of estuarine biocenoses, the ecotone could be more system-specific and biological compartment-specific. © 2010 Elsevier Ltd. All rights reserved.
(Estuarine, Coastal and Shelf Science. vol. 88, n° 0272-7714, pp. 219--232, 11/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LIENSs, INSU - CNRS, ULR, CNRS, BOREA, UNICAEN, NU, MNHN, IRD, SU, CNRS, UA, CNRS, UNICAEN, NU, NU, CRELA, IFREMER, ULR, CNRS
Highstand vs. lowstand turbidite system growth in the Makran active margin: Imprints of high-frequency external controls on sediment delivery mechanisms to deep water systems
Late Quaternary turbidite system growth along the Makran convergent margin is investigated through a set of deep-sea cores from upper slope and piggy-back basins to deep basin plain settings. High-resolution stratigraphy in these various depositional environments permits reconstruction of the evolution of sand-to-mud ratio, sedimentation rates, frequencies, and thickness of turbidite deposits during the last 25 ka BP. This study demonstrates how tectonics, climate and eustasy can interplay at high resolution (< 20 ka) and control the input of terrigeneous sediment along the tectonically active Makran convergent margin, in a source-to-sink perspective. The Makran turbidite system growth has been continuous throughout sea-level lowstand, transgressive, and highstand conditions. However, the frequency, rates, and nature of sediment supply varied in response to climate, sea-level, and tectonically induced changes in source-to-sink sediment dispersal modes. These changes include conditions of sediment production and availability in the drainage basin, capacity of transport from fluvial systems, and rates of sediment storage on the shelf and upperslope areas. Climate in the hinterland appears as a first-order control on the properties of turbidity currents that feed the turbidite system, controlling the average sand-to-mud ratio in the deep water deposits. The onset of sea-level highstand after ∼ 8 ka BP resulted in a notable change in turbidite system growth, characterized by the occurrence of large volume, thick turbidity currents (> 300 m thick along the continental slope) originated from successive, multiple slide or slump-induced surges. Their related deposits have low recurrence intervals, close to those calculated from the large magnitude earthquake and tsunami record in the Makran area. Comparison with the Nile and Indus turbidite systems growth during the Late Quaternary provides an evaluation of the relative importance of shared forcing parameters (i.e. monsoon-induced phases of arid/humid conditions and post-glacial sea-level rise), in significantly different basin settings. The Indus fan appears mainly controlled by eustasy during the last 25 ka. Inversely, similarities are found between the Nile and Makran turbidite systems, where sea-level changes are modulated by the climate impact on fluvial dynamics in the hinterland. However, the Makran turbidite system growth is continuous through times, because both the uplift in the coastal area and the fluvial dynamics of short, mountainous river systems allow high sediment transfer rates to the marine basin, even though arid conditions and associated low water fluxes. Earthquake-induced highstand turbidite deposits form a thick sedimentary succession in the Oman abyssal plain, and are significant in the geologic record. This study finally illustrates how the complex interplay between external (allogenic) forcings can complicate the interpretation of high-resolution sedimentary successions in turbidite-filled basins.
(Marine Geology. vol. 274, n° 0025-3227, pp. 187 - 208, 11/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IFP, VU, SHOM, IFREMER, UNS, UniCA
Post-depositional redistribution of trace metals in reservoir sediments of a mining/smelting-impacted watershed (the Lot River, SW France)
Mining/smelting wastes and reservoir sediment cores from the Lot River watershed were studied using mineralogical (XRD, SEM-EDS, EMPA) and geochemical (redox dynamics, selective extractions) approaches to characterize the main carrier phases of trace metals. These two approaches permitted determining the role of post-depositional redistribution processes in sediments and their effects on the fate and mobility of trace metals. The mining/smelting wastes showed heterogeneous mineral compositions with highly variable contents of trace metals. The main trace metal-bearing phases include spinels affected by secondary processes, silicates and sulfates. The results indicate a clear change in the chemical partitioning of trace metals between the reservoir sediments upstream and downstream of the mining/smelting activities, with the downstream sediments showing a 2-fold to 5-fold greater contribution of the oxidizable fraction. This increase was ascribed to stronger post-depositional redistribution of trace metals related to intense early diagenetic processes, including dissolution of trace metal-bearing phases and precipitation of authigenic sulfide phases through organic matter (OM) mineralization. This redistribution is due to high inputs (derived from mining/smelting waste weathering) at the water-sediment interface of (i) dissolved SO4 promoting more efficient OM mineralization, and (ii) highly reactive trace metal-bearing particles. As a result, the main trace metal-bearing phases in the downstream sediments are represented by Zn- and Fe-sulfides, with minor occurrence of detrital zincian spinels, sulfates and Fe oxyhydroxides. Sequestration of trace metals in sulfides at depth in reservoir sediments does not represent long term sequestration owing to possible resuspension of anoxic sediments by natural (floods) and/or anthropogenic (dredging, dam flush) events that might promote trace metal mobilization through sulfide oxidation. It is estimated that, during a major flood event, about 870 t of Zn, 18 t of Cd, 25 t of Pb and 17 t of Cu could be mobilized from the downstream reservoir sediments along the Lot River by resuspension-induced oxidation of sulfide phases. These amounts are equivalent to 13-fold (Cd), not, vert, similar6-fold (Zn), 4-fold (Pb) the mean annual inputs of the respective dissolved trace metals into the Gironde estuary.
(Applied Geochemistry. vol. 25, n° 0883-2927, pp. 778-794, 11/04/2026)
LMTG, UT3, Comue de Toulouse, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GRESE, UNILIM, ISTO, INSU - CNRS, UO, UT, CNRS, UWr, UWr
A robust statistical framework for QTL analysis
(11/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LMBA, UBS, UBO EPE, CNRS, MSH
Spatio-temporal patterns of perkinsosis in the Manila clam Ruditapes philippinarum from Arcachon Bay (SW France)
Pathogens belonging to the genus Perkinsus infect many bivalve molluscan species around the world, including the Manila clam Ruditapes phihppinarum. We investigated the spatial distribution of this parasite at 34 stations throughout Arcachon Bay (SW France). Prevalence of perkinsosis was 93% and mean infection abundance was 96 x 10(3) cells g(-1) wet gill. Lowest mean abundances were found close to the Leyre River mouth and a significant negative correlation was observed between mean abundance and salinity. Perkinsosis was rare at the oceanic site where salinities and other environmental parameters were stable. A second aim of this study was to survey perkinsosis during annual cycles at 4 sites within Arcachon Bay. Prevalence and intensities (+/-SE) of the disease were high, on average between 70 and 100%, and 130 x 10(3) +/- 6.7 x 10(3) cells g(-1) wet gill. No seasonal cycle was evident. Clams were infected at 9 mm shell length and infection increased with clam size. The third objective was to determine the disinfection and infection kinetics through a 21 mo reciprocal transplantation between a nearly Perkinsus sp.-free area and a highly affected site. Disinfection appeared to be a very slow process and was similar at the site with favorable conditions for Perkinsus sp. as at the site with unfavorable conditions. Conversely, infection acquisition appeared to be episodic with spatially defined areas. Consequently, the overall lack of a clear seasonal infection pattern is interpreted as the combination of episodic infection events and slow disinfection kinetics.
(Diseases of Aquatic Organisms. vol. 91, n° 0177-5103, pp. 151-159, 11/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LRHA, HGS, IFREMER
Potential and limitations of marine and ice core sea ice proxies: an example from the Indian Ocean sector
Diatom assemblages in marine cores and sea salt deposition fluxes in ice cores have been used as sea ice proxies in the southern hemisphere. Here, a marine and an ice core proxy record for the Indian Ocean covering the last two glacial cycles are compared in order to illustrate their potential and limitations. The marine core was extracted in a location completely ice free under present-day conditions, and therefore was unable to record changes to the recent sea ice extent. Similarly, no sea ice was recorded at that location during the previous interglacial period. During the last glacial period, however, the site was seasonally covered by sea ice, and the diatom assemblages allowed an estimation of average seasonal sea ice presence. The ice core data originated from the East Antarctic plateau. The marine sodium present in the ice core was used as a proxy of the sea-ice coverage and, on average, a larger sea ice surface led to an increased sea-salt aerosol flux, seen e.g. at the last glacial inception. However, the response of the sea salt flux to increasing sea ice extent diminished during peak glacial conditions when only minimal variability was recorded in the ice core record. A first-order approximation is used to take this non-linear response of the ice core sea ice proxy into account. Based on the ice core proxy record, sea ice extent was reduced considerably during the warm episodes of the previous two interglacial periods compared to modern sea ice extent, in particular during the peak warmth of the Last Interglacial. The ice core proxy also showed a very strong precessional variability (pronounced spectral peak at 23 ka period) over the past 240 ka. The advantage of combining the two proxy records lies in the complementary nature of their response. While the ice core proxy showed limited sensitivity during full glacial conditions, the marine proxy recorded the seasonal sea-ice coverage. Once the sea ice retreated south of the location of the marine core, the ice core proxy responded to changes in sea ice extent. A composite of marine and ice core records may thus provide a data basis for a more detailed reconstruction of sea ice around Antarctica over the last few glacial-interglacial cycles.
(Quaternary Science Reviews. vol. 29, n° 0277-3791, pp. 296-302, 11/04/2026)
BAS, NERC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ANU
Evènements extrêmes en Afrique de l'ouest durant le dernier glaciaire et l'Holocène
(11/04/2026)
OASU, UB, INSU - CNRS, ULR, CNRS, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, L3AB, UB, INSU - CNRS, CNRS, OASU, UB, INSU - CNRS, ULR, CNRS, INRAE, LAB, UB, INSU - CNRS, CNRS, UB, LGF, UP1, CNRS
Long-term evolution (1988-2008) of Zostera spp. meadows in Arcachon Bay (Bay of Biscay)
The spatial variability of seagrass meadows in Arcachon Bay, was studied between 1988 and 2008 using a combination of mapping techniques based on aerial photographs for intertidal dwarf-grass ( Zostera noltii) beds and acoustic sonar for permanently submerged eelgrass ( Zostera marina) populations. The results show a severe decline over the period for both species, as well as an acceleration of the decline since 2005 for Z. noltii. The total surface regression over the studied period is estimated to be 22.8 km 2 for Z. noltii and 2.7 km 2 for Z. marina, which represent declines of 33 and 74% respectively. Environmental data time series spanning the same period were investigated in order to seek the causes for such a decline. The calculated inter-annual trends for temperature, salinity, nitrate plus nitrite, ammonia, suspended sediment and chlorophyll a did not identify any clear environmental change capable of explaining the observed seagrass regression. For instance, no evident sign of eutrophication was observed over the study period. On the other hand, we suggest that the observed variations of ammonia in the inner part of the lagoon are a symptom of the seagrasses' disappearance and thus, a first sign indicating a change of the Arcachon Bay ecosystem towards more instability and vulnerability. Several hypotheses to explain the observed seagrass decay are proposed.
(Estuarine, Coastal and Shelf Science. vol. 87, n° 0272-7714, pp. 357-366, 11/04/2026)
IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS