323,541 research outputs found
Benthic macrofauna and sediment reworking quantification in contrasted environments in the Thau Lagoon
No full textAs part of the Microbent-PNEC Program: ‘‘Biogeochemical processes at the wateresediment interface in eutrophicated environment’’, the aim of this work was to specifically investigate and quantify the relationships between macrobenthos and sediment reworking in the Thau Lagoon in order to provide information on the potential contaminant distribution and movements at the wateresediment interface. In order to achieve this, three cores were sampled at two stations (in the central part of the Thau Lagoon and near the shellfish farming zone) in the Thau Lagoon, in December 2001, April 2002, August 2002, January 2003 and May 2003. On the basis of quantification of macrobenthos and sediment reworking, evidence is provided of: (1) similar sediment mixing intensities for different species composition at the two stations; (2) the major role of functional bioturbation groups (e.g., biodiffusors and gallery-diffusors) modulated by seasonal variability on sediment mixing; (3) an increase of intensity in summer suggesting potentially different patterns of redistribution, bioaccumulation and chemical fate (e.g., speciation) of deposited contaminants
Sedimentary processes in the Thau Lagoon (France): From seasonal to century time scales
No full textAs a part of the MICROBENT programme, an investigation of the sedimentation framework was carried out at the water-sediment interface in the Thau Lagoon (French Mediterranean coast). Two main sites, C4 in the middle of the lagoon and C5 near oyster farms, were visited six times between December 2001 and May 2003. Interface sediments were studied using classical sedimentology parameters (radiography RX, grain size distribution) and analysis of selected radionuclides (234Th, 7Be, 210Pb, 226Ra). On a century time scale, excess 210Pb (210Pbxs) presents classical profiles with an upper mixed layer, followed by an exponential decrease of activities to undetectable levels below 20 – 30 cm. At the central site, C4, cores seem to register episodic changes in mean grain size, presenting recurrently peaks. The upper 10 cm of 210Pbxs profiles at site C5 exhibit a mixed layer associated with coarser sediments: this could be related to biological activity. Sedimentation rates derived from 210Pbxs varied from 0.15 cm y−1 at the edge of the basin, to 0.25 cm y−1 at the central site. On a seasonal time scale, 234Th and 7Be both show significant variations in activities and in penetration within the sediment. Bioturbation rates derived from both radionuclides agree well and range between 1–10 cm2 y−1 at site C4 and 1–31 cm2 y−1 at site C5. 234Th and 7Be fluxes at the water-sediment interface show too seasonal variations, more pronounced for site C5. This latter site presents especially a higher variability that is well marked with season, probably in relation with its position near oyster farms
Influence of shellfish farming activities on nitrification, nitrate reduction to ammonium and denitrification at the water-sediment interface of the Thau lagoon, France
No full textThe seasonal patterns of nitrification, denitrification and dissimilatory ammonium production (DAP) rates were studied in the sediment of 2 stations in the Thau lagoon (south of France). The station ZA was located within the shellfish farming zone and thestation B was the reference site. A marked effect of shellfish farming on bacterial activities was observed. Spatial differences were associated with discrepancies in the organic content and the reduction state of sediments, i.e. highest reductive processes (denitrification and DAP) were noted in shellfish farming area, whereas the oxidative process (nitrification) was predominant outside the farming zone. At both stations, the DAP activity increased in September (autumn) concomitant with an increase of the C/N ratio in the sediment due to the sedimentation of the summer phytoplanktonic production. Nitrification and denitrification rates exhibited maxima in November (winter) corresponding to dissolved inorganic nitrogen inputs from the surrounding land. In the shellfish farming site, 98% of nitrate was reduced to NH4+ and 2% to N2O, showing that the most of the NO3- was reduced to ammonium and remained available for the ecosystem
Coupling of carbon, nitrogen and oxygen cycles in sediments from a Mediterranean lagoon: a seasonal perspective
No full textExperimental data and simulations were used to investigate the seasonal coupling between carbon, nitrogen and oxygen cycles in marine sediments from a eutrophic shallow lagoon in the Mediterranean Sea area. A negative seasonal correlation was observed between oxygen consumption and coupled nitrification–denitrification rates in surface sediments. Elevated values of oxygen consumption rates were reached during warm periods (up to 87.7 mmol m–2 d–1) whereas nitrification and denitrification rates remained close to the lowest rates reported for coastal sediments (values around 0.021 to 0.35 mmol N m–2 d–1 for nitrification and 0.014 to 0.045 mmol N m–2 d–1 for denitrification). A steady-state diagenetic model closely represented the seasonal negative correlation of oxygen uptake, coupled nitrification–denitrification rates, the vertical distribution patterns of pore water oxygen and the solid phase distribution of organic carbon when nitrification inhibition by sulfide was included. Simulation adjusted to field data also highlighted the importance of oxygen penetration depth in the seasonal variation of nitrification. The modelling indicated that anaerobic metabolism was the most significant pathway (65 to 80%) during organic matter mineralization with a clear seasonal increase during warm periods. These warm periods were also characterized by the higher benthic demand of oxygen mostly used to re-oxidize the by-products from anaerobic reactions (from 57 to 82%), the other part being used for carbon mineralization.
Population status of the Critically Endangered fan mussel Pinna nobilis in Thau Lagoon (France)
No full textInternational audienceSince 2016, the noble pen shell Pinna nobilis , a unique and emblematic giant bivalve endemic to the Mediterranean Sea, has been affected by mass mortality events (MMEs), primarily due to the pathogen Haplosporidium pinnae . To date, all known populations located in the open sea have been decimated by epizootics, and P. nobilis is currently classified as a Critically Endangered species. The last refuge areas with P. nobilis populations are now in coastal lagoons. This study assesses the status, size, density, and spatial distributions of P. nobilis populations in Thau Lagoon (Occitany, France). At the end of January 2024, 1931 live individuals were recorded at 30 different surveyed sites. Our surveys indicate various size-class distributions ranging from young recruits to adults. Examining the spatial distribution of P. nobili s revealed high-density populations in specific areas (up to 25 ind. 100 m -2 ). P. nobilis is present from the edges of the lagoon to the central and deeper zones (up to 9 m deep). Although Thau Lagoon experienced a localized MME at the end of 2020, driven by the presence of H. pinnae , this study reveals the occurrence of new individuals in previously infected areas, indicating signs of population recovery and potential resilience. All these observations suggest that Thau Lagoon represents one of the very last sanctuaries for P. nobilis in the Mediterranean Sea
A Diagnostic Thau Observer for a Class of Unmanned Vehicles
No full textThis paper addresses the problem of sensor fault detection for a wide class of Unmanned Vehicles (UVs). First a general model for UVs, based on the dynamics of a 6 Degrees Of Freedom (6-DOF) rigid body, subject to gravity and actuation forces, is presented. This model is shown to satisfy the necessary conditions to the existence of a non-linear observer (Thau) when proper assumptions for the actuation forces are made. The observer can thus be used to generate diagnostic residuals inside a Fault Detection (FD) system. Finally, the proposed approach is customized for sensor fault detection on an unmanned quad-rotor vehicle, and simulation results show the effectiveness of the adopted solution
Diffusive author(s), cohesive author: Analysis of S/N (1994)
No full textThis study indicates the ways in which various aspects of the author(s) are brought forth in Dumb type’s performance art, the S/N production. Previous research has suggested a non-hierarchical organization of Dumb type and the absence of a “privileged author” in Dumb type’s collaborative work, S/N. However, the results that I have investigated from member’s interviews on the creative process of S/N along with my analysis of the recorded images of S/N, indicate a different aspect of the author(s). First, S/N was created through, so to speak, the collective ideas of the members of Dumb type. Further, S/N has at least nine quotations from previous performances, installations, and printed writings, besides the work-in-progress technique. Explicating one of the “author functions” as given by Michel Foucault, each text has plural subjects of the author. However, it has been revealed from members’ interviews that Teiji Furuhashi had a decision-making role in selecting the members’ ideas within the performance. Since then, S/N has had plural subjects of creation; however, Furuhashi is one of the subjects of creation along with the “privileged author.” S/N has plural authors (diffusive authors) yet at the same time, it has a “privileged author,” Teiji Furuhashi (cohesive author)
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Norovirus foodborne outbreaks associated with the consumption of oysters from the Etang de Thau, France, December 2002.
No full textIn January 2003, the Institut de Veille Sanitaire received notification of clusters of gastroenteritis (GE) thought to be associated with consumption of oysters harvested from Etang de Thau in the south of France. At the same time Italy reported an outbreak (200+ cases) associated with oysters from the Etang de Thau. An investigation was carried out to determine the source and vehicle of the outbreaks. Descriptive analysis of reported clusters in France, microbiological analysis of stool and oyster samples, genotyping of noroviruses and an environmental investigation of the Etang de Thau were carried out. A retrospective cohort study was also undertaken among those attending a number of family meals in Paris. Thirteen family clusters in four districts of France (69 cases) could be attributed to the consumption of Thau oysters based on descriptive evidence. Oysters distributed at an office in Paris and consumed at fourteen family meals between 19 and 24 December led to a further outbreak. In this outbreak the attack rate was 21/36 (58%) for Thau oyster consumers and 0/22 for non-consumers (p=0.00002). Noroviruses (genogroups I and II) were found in stool samples from four clusters and oysters from three clusters (including Paris). Environmental investigations revealed heavy rainfall, an overflow of a water purification station and faecal contamination of the Etang de Thau in December. Oysters from the Etang de Thau were responsible for a number of clusters of norovirus GE in winter 2002 in France and also in Italy. High Escherichia Coli levels in Thau water and shellfish led to an official request, mid-December, for oyster purification before distribution. This was not possible, due to lack of purification facilities. This investigation has contributed to a change in the way that shellfish harvesting areas are classified in France
Differences in serum bile acid composition between unoperated cirrhotic patients and patients with portacaval or mesocaval shunt
No full textSerum bile acids were determined in 13 cirrhotic patients with portacaval shunt and in 15 with mesocaval shunt. 20 nonshunted cirrhotics were used as controls. Serum bile acid levels were higher in portacaval (26.7 +/- 14.3 micrograms/ml) than in mesocaval shunt patients (16.9 +/- 8.1 micrograms/ml) and controls (14.1 +/- 11.5 micrograms/ml). The cholic/chenodeoxycholic ratio was lower after portacaval shunt than after mesocaval shunt (0.36 +/- 0.15 and 0.63 +/- 0.26, respectively). It is hypothesized that these findings may be consistent with a larger hepatic blood flow present in mesocaval shunted patients and with chenodeoxycholic absorption in the upper small intestine
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