Artificial cold-adapted microbial mats cultured from Antarctic lake samples. 1. Formation and structure
(Aquatic Microbial Ecology. vol. 26, n° 0948-3055, pp. 115-125, 18/05/2026)
LEFE, INEE-CNRS, CNRS, UT3, Comue de Toulouse, CNRS, Toulouse INP, Comue de Toulouse, ECOLAG, UM2, IFREMER, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Recent Holocene paleo-environmental evolution and coastline changes of Kition, Larnaca, Cyprus, Mediterranean Sea
Sedimentological, paleontological analysis and 14C dating of 17 cores obtained in the vicinity of the Phoenician military harbor (VIII–IV BC) of Kition Bamboula (Cyprus) provide new paleo-environmental information for the reconstruction of shoreline changes for Kition and Larnaca Bay over the last 4000 years. We propose that a communication existed between the inner harbor of Bamboula (presently 400 m inland) and the northern district of Lichines, which was a marine embayment. Our core data led us to revisit the previous hypothesis of a direct east–west channel between the harbor and the open sea (Nicolaou, K., 1976. The historical topography of Kition. Studies in Mediterranean Archaeology, Göteborg, vol. 153, pp. 1–373; Gifford, J.A., 1978. Paleogeography of archaelogical sites of the Larnaca lowlands, southeastern Cyprus. PhD Thesis, University of Minnesota, pp. 1–192). We propose instead that a spit of coarse material isolated the lagoon from the open sea from 2600 to 1600 years BP.
(Marine Geology. vol. 170, n° 0025-3227, pp. 205-230, 01/10/2000)
CEREGE, IRD, INRA, AMU, CdF (institution), INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, URA 1761 / ESA 7073 / FRE 2400, MNHN, UPMC, CNRS, MOM, UL2, CNRS
Short- and long-term sedimentation on Montportail–Brouage intertidal mudflat, Marennes–Oléron Bay (France)
The intertidal mudflat of Montportail-Brouage is 4 km wide and extends over about 30% of intertidal area of the Bay of Marennes-Oléron. The sampling area was a cross-shore transect (east–west) in the mid-part of the mudflat, so as to overlap the different geomorphological features, from the shore to the central channel. Particularly distinctive were zones of shore-oblique ridges and runnels, and small channels. The short-term erosion-sedimentation processes related to these bedforms, and their effects on the long-term stability of these structures are poorly known. Thus, sediment budget is difficult to assess in the long term, due to temporal variations. Monthly sedimentological surveys were performed from March 1997 to May 1998. Six stations were sampled by coring for determination of water content, dry density, grain size and carbonate content of the sandy fraction, measured on the topmost 5 cm. Within the ridge and runnel zone, this sampling was done on both structures along with the determination of depth profiles of macrofauna species. Radiographic profiles to a depth of 50 cm were made at each of the 6 stations for description of the sedimentary facies, and radioisotope profiles () were made at four stations. Wet bulk density appeared to be roughly constant (1.39–1.44 kg m−3) over the whole mudflat below 2 or 3 cm. For the levels 0–1 and 1–2 cm, the bulk density showed much more variation, in particular in the runnels. These variations were due to episodic deposits of fluid mud (wet bulk density <1.25 kg m−3). The sand content decreased from the lower part of the mudflat to the upper part, particularly in the fluid mud. On the contrary, the carbonate content of the sand fraction increased in the upper part by accumulation of foraminifera associated with shell lag deposits. 7 Be measurements revealed a short-term sedimentation of fluid mud (up to 21.04 cm yr−1), particularly in runnels from the upper mudflat, thus indicating a temporary deposit, easily resuspended by wave action. 210 Pbexc measurements showed a long-term sedimentation rate which was 4 times higher in the lower part (0.97 cm yr−1) of the mudflat (near oyster reefs and mussel “bouchots”) than in the upper part (0.26 cm yr−1). In the middle mudflat, ridges and runnels exhibited a large difference of the long-term sedimentation rates, 0.70 cm yr−1 on ridges and only 0.07 cm yr−1 in runnels, that could be considered as a passageway for fluid mud transport. In the middle mudflat, where ridges and runnels occurred, synopsis of observations indicated that a 30 yr old and 18 cm thick ridge layed on a more than 100 yr old basement mudflat. This bedform is maintained through short- and long-term sedimentations. In the runnels, always flooded by water even at low tide, the short-term sedimentation was 21.04 cm yr−1, but these sediments can be easily resuspended by tidal currents, inducing a weak long-term sedimentation (0.07 cm yr−1). In the ridges, the short-term sedimentation was 7.27 cm yr−1; however, due to potential impacts of drying processes, along biostabilization by epipelic diatoms during subaerial exposure at low tide, the short-term sedimentation contributed to a long-term sedimentation of 0.70 cm yr−1.
(Continental Shelf Research. vol. 20, n° 0278-4343, pp. 1513 - 1530, 10/09/2000)
CREMA, IFREMER, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LIENSs, INSU - CNRS, ULR, CNRS
Physiography and recent sediment distribution of the Celtic Deep-Sea Fan, Bay of Biscay
(Marine Geology. vol. 169, n° 0025-3227, pp. 207-237, 01/09/2000)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IFREMER, SHOM, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
A census of macroparasites in an intertidal bivalve community, Arcachon Bay, France.
Amongst the potential biotic factors affecting bivalve population dynamics, parasitism has received little attention. Examination of the three dominant bivalves (the edible cockle Cerastoderma edule, the blue mussel Mytilus edulis, and the Manila clam Tapes philippinarum) on an intertidal sandflat in the Bay of Arcachon (French Atlantic coast) revealed the occurrence of a rich community of macroparasites. These parasites belong to digenean trematodes (ten species), turbellarians (one species), cestodes (one species) and copepods (one species). The mean number of parasite species increased with shell length and reached 4 in cockles (maximum = 7 per ind.), 2.6 in mussels (max. = 5 per ind.) and only 1.7 in clams (max. = 4 per ind.). Total parasite prevalence was higher in cockles and mussels (84.9 and 72.3 %, respectively) than in clams (49.7 %). Host specificity was much higher for non-encysted larvae than for encysted metacercariae or non digenes. The occurrence of sporocysts of the digene Labratrema minimus in cockles seems to induce a lower infection by other parasite. The youngest bivalves (less than 10 mm in shell size) were nearly free of parasites. From the ‘shell size/parasite intensity’ relationship, the macroparasites are highly suspected to increase the mortality of recruits and adult bivalves. © 2000 Ifremer/CNRS/IRD/Éditions scientifiques et médicales Elsevier SAS
(Oceanologica Acta, n° 0399-1784, 01/08/2000)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Modeling δ15N evolution: First palaeoceanographic applications in a coastal upwelling system
The delta(15)N Signal in marine sediments appears to be a good palaeoceanographic tracer. It records biological processes in the water column and is transferred to and preserved in the sediments. Changes in forcing factors in upwelling systems may be recorded by delta(15)N. These forcing conditions can be of a biogeochemical nature, such as the initial isotopic signal of the nutrients or the trophic structure, or of a physical nature, such as wind stress, insolation, temperature or dynamic recycling. A simple nitrogen-based trophic chain model was used to follow the development of the nitrogen isotopic signal in nutrients, phytoplankton, zooplankton and detritus. Detrital delta(15)N, influenced by the isotopic signature of the upwelled nutrients and isotopic fractionation along the trophic chain (photosynthesis and zooplankton excretion), was then compared to the sedimentary signal measured off Mauritania. In our model, the biological variables are transported at shallow depths by a simple circulation scheme perpendicular to the coast depicting a continental shelf recirculation cell. Because cell length depends on the extension of the continental shelf, modifications of the cell length mimic sea level changes. Long cell length (high sea lever) scenarios produce higher delta(15)N values whereas short cell length scenarios result in lower values as in the glacial low sea level periods. Despite changes in many climatic parameters throughout this period, our results show that changing the sea level is sufficient to reconstruct the main pattern of the sedimentary delta(15)N variations offshore of the Mauritanian upwelling, i.e. an increase from about 3 parts per thousand to 7 parts per thousand during the deglaciation, without invoking any change in nitrogen fixation or denitrification.
(Journal of marine research. vol. 58, n° 0022-2402, pp. 609-630, 01/07/2000)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEGOS, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS
Coccolith evidence for instabilities in surface circulation south of Iceland during Holocene times
(Earth and Planetary Science Letters. vol. 179, n° 0012-821X, pp. 257-268, 01/06/2000)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, LDEO
Un paléolac du dernier interglaciaire pléistocène dans l'Extrême-Sud hyperaride de la Jordanie
(Comptes Rendus de l'Académie des Sciences - Series IIA - Earth and Planetary Science. vol. 330, n° 1778-4107, pp. 259-264, 01/02/2000)
JU, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ESEP, UJF, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GEOTRAC, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, LGQ, CNRS
Phylogenetic relationships of Pleurotus species according to the sequence and secondary structure of the mitochondrial small-subunit rRNA V4, V6 and V9 domains
A comparative study of the V4, V6 and V9 domains of the mitochondrial small-subunit (SSU) rRNA was conducted to evaluate the use of these sequences to investigate phylogenetic relatedness within the genus Pleurotus. The PCR products encompassing these regions from 48 isolates belonging to 16 Pleurotus species were sequenced and compared. From this comparison, the length and sequence of the three domains were found to be constant within a species. Significant inter-species variations due to insertion/deletion events were found, in most cases occurring in regions not directly involved in the maintainance of the standard SSU rRNA secondary structure. Phylogenetic analysis based upon these mitochondrial sequences was in agreement with relationships previously established by morphological descriptions and with previous studies based upon the nuclear genome or isozymes; moreover such analysis resolved some ambiguities in earlier analyses. It was confirmed that P. ostreatus and P. florida represent a single species, as well as P. pulmonarius and P. sajor-caju. The phylogenetic analysis also made it possible to assess the relative positions of P. rattenburyi, P. lampas, P. sapidus, P. colombinus and P. eryngii. The results clearly showed that sequences of the V4, V6 and V9 domains of the mitochondrial SSU rRNA could provide good markers for use in the taxonomy and phylogeny of species of Basidiomycota. Because of their nucleotide conservation, the major advantage of these species-specific markers was the possibility to study only one isolate from each species to determine phylogenetic relatedness.
(Microbiology. vol. 146, n° 1350-0872, pp. 209-221, 01/01/2000)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Premières observations sur la morphologie et les processus sédimentaires récents de l’Éventail celtique
First observations on the morphology and recent sedimentary processes of the Celtic Deep Sea Fan. During the SEDIFAN 1 cruise we surveyed the bathymetry and the acoustic properties of the surface sediment of the Celtic Deep Sea Fan. We also collected Küllenberg cores in order to study recent sedimentary processes. From the bathymetry survey it is relatively easy to recognize the main areas of modern fan. The upper fan included a large sedimentary ridge which constitutes the right levee of the prominent meandering Whittard valley. After its confluence with the Shamrock valley the course of the Whittard valley is abruptly deflected to the south. At a short distance to the south the valley divides into two upper-fan channels, the Celtic channel to the west being the deeper one. This point constitutes the centre of a radiating pattern which is developed on a 150° quadrant and a radius of about 100 km. The acoustic imagery displays contrasted features, related to change in lithology within the first metre beneath the sea bottom and to the sea floor roughness. The Austell ridge exhibits a contrasted pattern of elongated areas with high and low acoustic backscattering levels. This pattern is related to the development of abyssal dunes, the amplitude of which is of metric order. Particularly remarkable is a lobe-shaped low back-scattering area in the western part of the middle fan, also noteworthy are a lineated facies to the west and a braided facies to the east of the fan. The laminated silty-clayey sequences deposited on the Whittard ridge and on the Trevelyan levee were deposited during the deglaciation. We interpret these as turbidity currents overflow deposits from the Whittard valley. At the end of isotopic stage 3 and during stage 2, the English Channel was a large plain flooded by the Channel River. During this period a broad delta developed at 100 m below the present-day depth and a wide spectrum of material was bound to be supplied to the deep sea and contributed particularly to the deposition of the Whittard ridge silty-clayey sequences. The stage 2 deposits are characterized by rhythmic levels enriched in monosulfides. These types of deposits are common in areas affected by fluvial discharges. Excluding the sedimentary ridge and the channel levees the surface deposits sampled with the Küllenberg corer are sandy. These sands are deposited in various contexts on the interfluve between the western and eastern channels and at channel mouths. They were emplaced during high sea level stands as a result of high energy gravity processes. The precise sources of these sands have not yet been identified, however benthic foraminifers from included ooze pebbles have living depths of between 500 and 1 000 m. The gravity processes which eroded this marly ooze may have been triggered on the upper slope. The Celtic shelf is presently a high energy platform where the conjunction of storms and spring tides can lead to enhanced sediment transport from near-shore to the deep sea. The relict or palimpsest deposits of the glacial delta also constitute a large reservoir of sandy material which can also be subject to reworking. © 2000 Ifremer/CNRS/IRD/Éditions scientifiques et médicales Elsevier SASdeep-sea fan / Quaternary / sediment / turbidity / palaeoclimate
(Oceanologica Acta. vol. 23, n° 0399-1784, pp. 109-116, 01/01/2000)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS