Multi-disciplinary investigation of fluid seepage on an unstable margin: The case of the Central Nile deep-sea fan.
We report on a multidisciplinary study of cold seeps explored in the Central Nile deep-sea fan of the Egyptian margin. Our approach combines in situ seafloor observation, geophysics, sedimentological data, measurement of bottom-water methane anomalies, pore-water and sediment geochemistry, and 230Th/U dating of authigenic carbonates. Two areas were investigated, which correspond to different sedimentary provinces. The lower slope, at ∼ 2100 m water depth, indicates deformation of sediments by gravitational processes, exhibiting slope-parallel elongated ridges and seafloor depressions. In contrast, the middle slope, at ∼ 1650 m water depth, exhibits a series of debris-flow deposits not remobilized by post-depositional gravity processes. Significant differences exist between fluid-escape structures from the two studied areas. At the lower slope, methane anomalies were detected in bottom-waters above the depressions, whereas the adjacent ridges show a frequent coverage of fractured carbonate pavements associated with chemosynthetic vent communities. Carbonate U/Th age dates (∼ 8 kyr BP), pore-water sulphate and solid phase sediment data suggest that seepage activity at those carbonate ridges has decreased over the recent past. In contrast, large (∼ 1 km2) carbonate-paved areas were discovered in the middle slope, with U/Th isotope evidence for ongoing carbonate precipitation during the Late Holocene (since ∼ 5 kyr BP at least). Our results suggest that fluid venting is closely related to sediment deformation in the Central Nile margin. It is proposed that slope instability leads to focused fluid flow in the lower slope and exposure of 'fossil' carbonate ridges, whereas pervasive diffuse flow prevails at the unfailed middle slope
(Marine Geology. vol. 261, n° 0025-3227, pp. 92-104, 01/06/2009)
GM, IFREMER, IMAGES, UPVD, GEOAZUR 6526, IRD, UPMC, UNS, INSU - CNRS, UniCA, CNRS, LEP, EEP, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, SAE, IRD, UPMC, CNRS, LOCEAN, IPSL, ENS-PSL, PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, IP Paris, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, IFREMER, NIOZ
Comparative analysis of gene expression in brain, liver, skeletal muscles, and gills of zebrafish (Danio rerio) exposed to environmentally relevant waterborne uranium concentrations
The effects of waterborne uranium (U) exposure on gene expression were examined in four organs (brain, liver, skeletal muscles, and gills) of the zebrafish (Danio rerio). Adult male fish were exposed to three treatments: No added uranium (control), 23 ± 6 μg U/L, and 130 ± 34 μg U/L. After 3, 10, 21, and 28 d of exposure and an 8-d depuration period, gene expression and uranium bioaccumulation were analyzed. Bioaccumulation decreased significantly in liver during the depuration phase, and genes involved in detoxification, apoptotic mechanism, and immune response were strongly induced. Among these genes, abcb3l1, which belongs to the adenosine triphosphate (ATP)-binding cassette transporter family, was induced 4- and 24-fold in organisms previously exposed to 23 ± 6 and 130 ± 34 μg U/L, respectively. These results highlight the role of liver in detoxification mechanisms. In gills, at the highest uranium concentration, gpx1a, cat, sod1, and sod2 genes were up-regulated at day 21, indicating the onset of an oxidative stress. Mitochondrial metabolism and DNA integrity also were affected, because cox1, atp5f1, and rad51 genes were up-regulated at day 21 and during the depuration phase. In skeletal muscles, coxI, atp5f1, and cat were induced at day 3, suggesting an impact on the mitochondrial metabolism and production of reactive oxygen species. In brain, glsI also was induced at day 3, suggesting a need in the glutamate synthesis involved with neuron transmission. No changes in gene expression were observed in brain and skeletal muscles at days 21 and 28, although bioaccumulation increased. During the depuration phase, uranium excretion was inefficient in brain and skeletal muscles, and expression of most of the tissue-specific genes was repressed or unchanged. © 2009 SETAC.
(Environmental Toxicology and Chemistry. vol. 28, pp. 1271-1278, 01/06/2009)
IRSN/DEI/SECRE/LRE, IRSN/DEI/SECRE, IRSN, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Benthic indicators and index approaches in the three main estuaries along the French Atlantic coast (Seine, Loire and Gironde)
The three main estuaries in the French Atlantic coast – the Seine, Loire and Gironde, all with high tidal regimes – are interfaces between the continental and the coastal ecosystems. The Seine and Gironde are highly contaminated, whereas the Loire remains in a more natural state. Both the Seine and Gironde have suffered from harbour construction, and as a result, their biological units are extremely compartmentalized. Benthic species and communities have adapted to tolerate temporal physical and chemical changes (e.g. salinity, substrata, depth, and levels of fine particles and oxygen) and human activities (e.g. dredging, shipping traffic, and habitat reduction). Although numerous bio-indicators and indices are used to define the ecological quality status (EcoQS) of coastal waters, very few of them were developed specifically for environments with a mosaic of conditions and salinity levels, including freshwater. The main problem appears to be that all the indices for determining anthropogenic stress examine the abundances of stress-tolerant species, which may also be able to tolerate natural stressors such as those occurring in estuaries. This paper takes a look at the development status of the benthic indicators and index approaches used in the three main estuaries along the French Atlantic coast. In addition, it examines the adaptation of the different benthic indicators to the taxonomic sufficiency principle, and the adaptation of the Benthic Opportunistic Polychaetes Amphipods index (BOPA) and the Benthic Opportunistic Annelida Amphipod index (BO2A) for use in the freshwater zones of transitional waters (i.e. up to the upper limit of the tidal range). Several perspectives are discussed in light of the diverse disturbances and the heterogeneity of such stressed zones, such as the use of multimetric and scoring approaches.
(Marine Ecology. vol. 30, n° 0173-9565, pp. 228-240, 01/06/2009)
LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, Nantes univ - UFR ST, Nantes Univ
Solid-phase extraction and liquid chromatography-tandem mass spectrometry development for the analysis of antibiotics in manure
Pharmaceuticals are now well known micro-pollutants of aquatic systems. They are studied due to sanitary and environmental risks they could represent and especially the antibiotics because of the antibiotic resistance phenomenon. We have focused our research on that group of compounds. Antibiotics mainly enter into the environment either via sewage treatment plant (SWTP) effluent (human origin) or via runoff of land fertilized with sludge from SWTP or manure from livestock (veterinary origin). We have worked on that second origin and studied 2 different types of process before the manure spreading: i) the simple storage of the manure during few months in huge tank ; ii) the treatment process with solid/liquid separation system and 2 different ways of treatment for each phase. Whatever the origin of the contamination, it appears to be a chronic contamination and it is necessary to quantify compounds at trace level (ng/L). For this purpose, we have developed a method for the simultaneous quantification of 23 antibiotics belonging to 9 families. The first step is an extraction of molecules by SPE on Oasis HLB cartridges and the second one is the analysis by Rapid Resolution Liquid Chromatography-tandem mass spectrometry (RRLC/MS/MS) with a 5 cm C18 column and an electrospray ionisation source. The preliminary results show an important contamination of stored pig manure by lincomyin, tetracycline, oxytetracycline and sulfadiazine. The results are discussed according to various ways of manure treatment and uses.
(31/05/2009)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR GERE, CEMAGREF
Multiresidue analysis of pesticides in duck muscle and liver by liquid chromatography–triple quadrupole mass spectrometry.
(31/05/2009)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UPPA, IPREM, UPPA, INC-CNRS, CNRS
Impact of cadmium on aquatic bird Cairina moschata
The impact on palmiped Cairina moschata of two levels of dietary cadmium (Cd) contamination (C1: 1 mg kg-1 and C10: 10 mg kg-1) was investigated on liver gene expression by real-time PCR. Genes involved in mitochondrial metabolism, in antioxidant defences, detoxification and in DNA damage repair were studied. Metallothionein (MT) protein levels and Cd bioaccumulation were also investigated in liver, kidneys and muscle. Male ducks were subjected to three periods of exposure: 10, 20 and 40 days. Cd was mainly bioaccumulated in kidneys first and in liver. The concentrations in liver and kidneys appeared to reach a stable level at 20 days of contamination even if the concentrations in muscle still increased. Cd triggered the enhancement of mitochon-drial metabolism, the establishment of antioxidant defences (superoxide dismutase Mn and Cu/Zn; catalase) and of DNA repair from 20 days of contamination. Discrepancies were observed in liver between MT protein levels and MT gene up-regulation. MT gene expression appeared to be a late hour biomarker.
(31/05/2009)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IPREM, UPPA, INC-CNRS, CNRS, UPPA
Multi-scale slope instabilities along the Nile deep-sea fan, Egyptian margin: A general overview
The Nile deep-sea fan (NDSF), turbiditic system reaching a size of about 90,000 km2, has been investigated since 1998 by several geophysical methods (multibeam bathymetry, backscatter imagery, seismic data, 3–5 kHz echo-sounding). The analysis of this important data set evidenced that the NDSF is the locus of numerous multi-scale slope instabilities. Three main types of instabilities have been defined, mainly on the basis of their size or origin. (1) First type of instabilities related to the generalized gravity spreading of the Plio-Quaternary deep-sea fan on Messinian salt layers. This global spreading is accommodated by numerous localized slides. (2) Second type of instabilities correspond to giant mass movements probably triggered either by earthquakes, fluids, or climate and eustatic oscillations. Finally, (3) third type of instabilities correspond either to localized levee liquefactions or to thin-skinned slides on the steep slopes of the Eratosthenes seamount. The deposits generated by these slope movements greatly participate in the building of the NDSF. The characterization of these different instabilities, in a petroleum province as the NDSF, has important implications in terms of risk assessments when considering drilling operations.
(Marine and Petroleum Geology. vol. 26, n° 0264-8172, pp. 633-646, 22/05/2009)
IMAGES, UPVD, LDO, INSU - CNRS, UBO EPE, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GEOAZUR 6526, IRD, UPMC, UNS, INSU - CNRS, UniCA, CNRS
Tectonic shortening and gravitational spreading in the Gulf of Cadiz accretionary wedge: Observations from multi-beam bathymetry and seismic profiling
The Gulf of Cadiz lies astride the complex plate boundary between Africa and Eurasia west of the Betic-Rif mountain belt. We report on the results of recent bathymetric swathmapping and multi-channel seismic surveys carried out here. The seafloor is marked by contrasting morphological provinces, spanning the SW Iberian and NW Moroccan continental margins, abyssal plains and an elongate, arcuate, accretionary wedge. A wide variety of tectonic and gravitational processes appear to have shaped these structures. Active compressional deformation of the wedge is suggested by folding and thrusting of the frontal sedimentary layers as well as basal duplexing in deeper internal units. There is evidence for simultaneous gravitational spreading occurring upslope. The very shallow mean surface and basal slopes of the accretionary wedge (1° each) indicate a very weak decollement layer, geometrically similar to the Mediterranean Ridge accretionary complex. Locally steep slopes (up to 10°) indicate strongly focused, active deformation and potential gravitational instabilities. The unusual surface morphology of the upper accretionary wedge includes “raft-tectonics” type fissures and abundant sub-circular depressions. Dissolution and/or diapiric processes are proposed to be involved in the formation of these depressions.
(Marine and Petroleum Geology. vol. 26, n° 0264-8172, pp. 647-659, 21/05/2009)
LDO, INSU - CNRS, UBO EPE, CNRS, UEB, UAG, INSU - CNRS, UM, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UAlg, ULISBOA, INETI
Do trematode parasites affect cockle ( Cerastoderma edule) secondary production and elimination?
Digenean trematodes are omnipresent in the cockle Cerastoderma edule, a common coastal bivalve of (semi-)sheltered north-eastern Atlantic coasts. They can use their host as a second intermediate host where they remain in a relatively latent stage as metacercariae. Cockle population dynamics and trematode parasite load were monitored for two years in two sites, Arcachon (France) and Merja Zerga (Morocco) for the cockle cohort of 2005. Individual growth was slightly higher at Arcachon than at Merja Zerga (Von Bertalanffy parameters: K = 1.5 yr−1 in both sites but L∞ = 31.2 mm at Merja Zerga against 38.3 mm at Arcachon). Production during cockle life was twice as high at Merja Zerga (48.5 compared to 22.2 gDW.m−2 at Arcachon). Elimination compensated production at Merja Zerga while elimination was low at Arcachon (8.1 gDW.m−2) due to sediment dynamics which concentrated cockles within the sampling area. P/B was similar in both sites (2.4–2.6 yr−1) while E/B was higher at Merja Zerga (2.2 yr−1 versus 1.0 yr−1). Trematode communities were similar in both sites in terms of species and abundance. During the cockle cohort lifespan, there were 3 to 5 events in the parasite abundance survey that suggested parasite-dependent mortality. At Merja Zerga, trematodes metacercariae did not affect P/B (2.4 yr−1) but increased E/B (+14%). At Arcachon, they also had no effect on P/B (2.6 yr−1) but on the contrary increased E/B (+20%). The threshold of metacercariae abundance beyond which cockles are affected was lower for Echinostomatid trematodes at Merja Zerga, suggesting an interaction with other factors such as temperature which is higher at the southern limit of cockle distribution.
(Journal of the Marine Biological Association of the United Kingdom. vol. 89, n° 0025-3154, pp. 1395, 15/05/2009)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Evolution of the Nile deep-sea turbidite system during the Late Quaternary: influence of climate change on fan sedimentation
This paper presents an overview of the evolution of the Nile deep-sea turbidite system during the last 200 kyr, over a series of glacial to interglacial cycles. Six individual deep-sea fans were identified from an extensive field data set. Each fan comprises a canyon, channel system and terminal lobes. Two of these fan systems were possibly active at the same time, at least during some periods. Large-scale slope failures destroyed channel segments and caused the formation of new submarine fan systems. These slope failures thus played an important role in the overall evolution of the turbidite system. During the last glacial maximum (ca 25 to 14·8 ka) the central and eastern parts of the Nile deep-sea turbidite system were relatively inactive. This inactivity corresponds to a lowstand in sea-level, and a period of arid climate and relatively low sediment discharge from the Nile fluvial system. Rapid accumulation of fluvial flood-derived deposits occurred across the shallower part of the submarine delta during sea-level rise between ca 14·8 and 5 ka. The most recent deep-sea channel–lobe system was very active during this period of rising sea-level, which is also associated with a wetter continental climate and increased sediment and water discharge from the Nile. Increased sediment deposition in shallower water areas led to occasional large-scale slope failure. The Nile deep-sea turbidite system was largely inactive after ca 5 ka. This widespread inactivity is due to retreat of the coastline away from the continental shelf break, and to a more arid continental climate and reduced discharge of sediment from the Nile. The Nile deep-sea turbidite system may be more active during periods of rising and high sea-level associated with wetter climates, than during lowstands, and may rapidly become largely inactive during highstands in sea-level coupled with arid periods. These acute responses to climate change have produced sedimentary/stratigraphic features that diverge from traditional sequence models in their nature and timing. This large-scale sedimentary system responded to monsoon-driven climate change and sea-level change in a system-wide and contemporaneous manner.
(Sedimentology. vol. 56, n° 0037-0746, pp. 2061-2090, 08/05/2009)
GEOAZUR 6526, IRD, UPMC, UNS, INSU - CNRS, UniCA, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, INTECHMER, Cnam, ISMAR, ISMAR, CNR, ETH Zürich