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, 27/08/2026)
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
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, 27/08/2026)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, SISYPHE, UPMC, EPHE, PSL, PSL, CNRS
Evènements extrêmes en Afrique de l'ouest durant le dernier glaciaire et l'Holocène
(27/08/2026)
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
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, 27/08/2026)
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, 27/08/2026)
BAS, NERC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ANU
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, 27/08/2026)
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, 27/08/2026)
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, 27/08/2026)
LPG-ANGERS, LPG, UA, UN UFR ST, UN, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Abrupt climate changes of the last deglaciation detected in a Western Mediterranean forest record
Abrupt changes in Western Mediterranean climate during the last deglaciation (20 to 6 cal ka BP) are detected in marine core MD95-2043 (Alboran Sea) through the investigation of high-resolution pollen data and pollen-based climate reconstructions by the modern analogue technique (MAT) for annual precipitation (Pann) and mean temperatures of the coldest and warmest months (MTCO and MTWA). Changes in temperate Mediterranean forest development and composition and MAT reconstructions indicate major climatic shifts with parallel temperature and precipitation changes at the onsets of Heinrich stadial 1 (equivalent to the Oldest Dryas), the Bölling-Allerød (BA), and the Younger Dryas (YD). Multi-centennial-scale oscillations in forest development occurred throughout the BA, YD, and early Holocene. Shifts in vegetation composition and (Pann reconstructions indicate that forest declines occurred during dry, and generally cool, episodes centred at 14.0, 13.3, 12.9, 11.8, 10.7, 10.1, 9.2, 8.3 and 7.4 cal ka BP. The forest record also suggests multiple, low-amplitude Preboreal (PB) climate oscillations, and a marked increase in moisture availability for forest development at the end of the PB at 10.6 cal ka BP. Dry atmospheric conditions in the Western Mediterranean occurred in phase with Lateglacial events of high-latitude cooling including GI-1d (Older Dryas), GI-1b (Intra-Allerød Cold Period) and GS-1 (YD), and during Holocene events associated with high-latitude cooling, meltwater pulses and N. Atlantic ice-rafting. A possible climatic mechanism for the recurrence of dry intervals and an opposed regional precipitation pattern with respect to Western-central Europe relates to the dynamics of the westerlies and the prevalence of atmospheric blocking highs. Comparison of radiocarbon and ice-core ages for well-defined climatic transitions in the forest record suggests possible enhancement of marine reservoir ages in the Alboran Sea by 200 years (surface water age 600 years) during the Lateglacial.
(Climate of the Past. vol. 6, n° 1814-9324, pp. 245-264, 27/08/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, EPHE, PSL, LCE, CNRS, UMLP, UBFC
Deciphering of six blocks of Gondwanan origin within Eastern Indonesia (South East Asia)
The French Indonesian research programs, both conducted on land and offshore in the Banda Sea basins area, have led us to formulate a new interpretation of the East Indonesian geological components. In this area we distinguish, within the three main tectonic plates (Eurasian, Indo-Australian and Philippine-Pacific), seven blocks. Six blocks are deciphered as issued from the north-eastern Gondwanan margin and only one (the Halmahera block) issued from the Pacific plate. Among the Gondwanan blocks, two of them, namely Timor (probably originates from "Greater India") and Kolonodale (or the Argo block) came from the north-west Australian margin. The Lucipara, Seram and Banggai-Sula blocks originated from the western extension of the Papua-New Guinea Island while the Irian Jaya block is still linked to the North Australian margin. The last one, the Halmahera block, originated from the Pacific plate, moved westward along the North Papua-New-Guinea margin up to its present position in the northern part of the Banda Sea area. Our interpretation is mainly based on the lithostratigraphic succession, the geological evolution and the Early Mesozoic paleoposition of these blocks with respect to the climatic environment deduced from micropaleontological studies. According to previous studies, the Timor and Kolonodale blocks were detached from Gondwana during the Jurassic whereas the Lucipara, Seram and Banggai-Sula blocks were detached from Papua-New Guinea Island during the Neogene period. All these Gondwanan blocks collided with the Eurasian active margin, in the vicinity of Sulawesi Island: Timor and Kolonodale had joined the Eurasian margin by the end of the Paleogene, while Lucipara, Seram and Banggai-Sula collided with Sulawesi Island between the Middle Miocene to Middle Pliocene. After the collisions the last three blocks together with the Kolonodale block did not move again but suffered the opening of North and South Banda back-arc basins, by the Late Miocene. On the contrary, part of the Timor block moved south together with the southern margin of the south Banda basin and, later on during the middle Pliocene, collided with the northern Australian margin. The detachment of these blocks from the Gondwana margin, and their amalgamation with the Eurasian margin, are discussed and illustrated through palaeogeographic maps.
(Gondwana Research. vol. 18, n° 1342-937X, pp. 420-437, 27/08/2026)
FRE 2761, CNRS, UNIGE, LDO, INSU - CNRS, UBO EPE, CNRS, PEPS, UCBL, INSU - CNRS, CNRS, CEREGE, IRD, INRA, AMU, CdF (institution), INSU - CNRS, CNRS, Unhas, ISTO, INSU - CNRS, UO, UT, NEOLAiA, CNRS, iSTeP, UPMC, CNRS, LPGN, UN, CNRS