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Institution

University of the Littoral Opal Coast

EducationDunkirk, France
About: University of the Littoral Opal Coast is a education organization based out in Dunkirk, France. It is known for research contribution in the topics: Catalysis & Dielectric. The organization has 1242 authors who have published 2383 publications receiving 46230 citations. The organization is also known as: ULCO.


Papers
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Journal ArticleDOI
TL;DR: The abundance and size distribution of lakes is critical to quantifying limnetic contributions to the global carbon cycle as discussed by the authors, however, estimates of global lake abundance are not accurate and are unreliable.
Abstract: An accurate description of the abundance and size distribution of lakes is critical to quantifying limnetic contributions to the global carbon cycle. However, estimates of global lake abundance are ...

996 citations

Journal ArticleDOI
26 Apr 2007-Nature
TL;DR: It is found that a large phytoplankton bloom over the Kerguelen plateau in the Southern Ocean was sustained by the supply of iron and major nutrients to surface waters from iron-rich deep water below, suggesting that changes in iron supply from below may have a more significant effect on atmospheric carbon dioxide concentrations than previously thought.
Abstract: The availability of iron limits primary productivity and the associated uptake of carbon over large areas of the ocean. Iron thus plays an important role in the carbon cycle, and changes in its supply to the surface ocean may have had a significant effect on atmospheric carbon dioxide concentrations over glacial-interglacial cycles. To date, the role of iron in carbon cycling has largely been assessed using short-term iron-addition experiments. It is difficult, however, to reliably assess the magnitude of carbon export to the ocean interior using such methods, and the short observational periods preclude extrapolation of the results to longer timescales. Here we report observations of a phytoplankton bloom induced by natural iron fertilization--an approach that offers the opportunity to overcome some of the limitations of short-term experiments. We found that a large phytoplankton bloom over the Kerguelen plateau in the Southern Ocean was sustained by the supply of iron and major nutrients to surface waters from iron-rich deep water below. The efficiency of fertilization, defined as the ratio of the carbon export to the amount of iron supplied, was at least ten times higher than previous estimates from short-term blooms induced by iron-addition experiments. This result sheds new light on the effect of long-term fertilization by iron and macronutrients on carbon sequestration, suggesting that changes in iron supply from below--as invoked in some palaeoclimatic and future climate change scenarios--may have a more significant effect on atmospheric carbon dioxide concentrations than previously thought.

712 citations

Journal ArticleDOI
TL;DR: An overview of the plankton studies conducted during the last 25 years in the epipelagic offshore waters of the Mediterranean Sea is presented, finding a "multivorous web" is shown by the great variety of feeding modes and preferences and by the significant and simultaneous grazing impact on phytoplankton and ciliates by mesozooplankon.
Abstract: . We present an overview of the plankton studies conducted during the last 25 years in the epipelagic offshore waters of the Mediterranean Sea. This quasi-enclosed sea is characterized by a rich and complex physical dynamics with distinctive traits, especially in regard to the thermohaline circulation. Recent investigations have basically confirmed the long-recognised oligotrophic nature of this sea, which increases along both the west-east and the north-south directions. Nutrient availability is low, especially for phosphorous (N:P up to 60), though this limitation may be buffered by inputs from highly populated coasts and from the atmosphere. Phytoplankton biomass, as chl a, generally displays low values (less than 0.2 μg chl a l−1) over large areas, with a modest late winter increase. A large bloom (up to 3 μg l−1) is observed throughout the late winter and spring exclusively in the NW area. Relatively high biomass values are recorded in fronts and cyclonic gyres. A deep chlorophyll maximum is a permanent feature for the whole basin, except during the late winter mixing. It is found at increasingly greater depths ranging from 30 m in the Alboran Sea to 120 m in the easternmost Levantine basin. Primary production reveals a west-east decreasing trend and ranges between 59 and 150 g C m−2 y−1 (in situ measurements). Overall, the basin is largely dominated by small autotrophs, microheterotrophs and egg-carrying copepod species. The microorganisms (phytoplankton, viruses, bacteria, flagellates and ciliates) and zooplankton components reveal a considerable diversity and variability over spatial and temporal scales, although the latter is poorly studied. Examples are the wide diversity of dinoflagellates and coccolithophores, the multifarious role of diatoms or picoeukaryotes, and the distinct seasonal or spatial patterns of the species-rich copepod genera or families which dominate the basin. Major dissimilarities between western and eastern basins have been highlighted in species composition of phytoplankton and mesozooplankton, but also in the heterotrophic microbial components and in their relationships. Superimposed to these longitudinal differences, a pronounced biological heterogeneity is also observed in areas hosting deep convection, fronts, cyclonic and anti-cyclonic gyres or eddies. In such areas, the intermittent nutrient enrichment promotes a switching between a small-sized microbial community and diatom-dominated populations. A classical food web readily substitutes the microbial food web in these cases. These switches, likely occurring within a continuum of trophic pathways, may greatly increase the flux towards higher trophic levels, in spite of the apparent heterotrophy. Basically, the microbial system seems to be both bottom-up and top-down controlled. A "multivorous web" is shown by the great variety of feeding modes and preferences and by the significant and simultaneous grazing impact on phytoplankton and ciliates by mesozooplankton.

492 citations

Journal ArticleDOI
TL;DR: A tool for the direct visualization of Pel in biofilms is developed by combining Pel-specific Wisteria floribunda lectin staining with confocal microscopy and the results indicate that Pel cross-links eDNA in the biofilm stalk via ionic interactions.
Abstract: Biofilm formation is a complex, ordered process. In the opportunistic pathogen Pseudomonas aeruginosa, Psl and Pel exopolysaccharides and extracellular DNA (eDNA) serve as structural components of the biofilm matrix. Despite intensive study, Pel’s chemical structure and spatial localization within mature biofilms remain unknown. Using specialized carbohydrate chemical analyses, we unexpectedly found that Pel is a positively charged exopolysaccharide composed of partially acetylated 1→4 glycosidic linkages of N-acetylgalactosamine and N-acetylglucosamine. Guided by the knowledge of Pel’s sugar composition, we developed a tool for the direct visualization of Pel in biofilms by combining Pel-specific Wisteria floribunda lectin staining with confocal microscopy. The results indicate that Pel cross-links eDNA in the biofilm stalk via ionic interactions. Our data demonstrate that the cationic charge of Pel is distinct from that of other known P. aeruginosa exopolysaccharides and is instrumental in its ability to interact with other key biofilm matrix components.

426 citations

Journal ArticleDOI
TL;DR: It is revealed that 11 psl genes, pslACDEFGHIJKL, are required for Psl production and surface attachment and the first structural analysis of the psl‐dependent polysaccharide, which consists of a repeating pentasaccharide containing d‐mannose, d‐glucose and l‐rhamnose.
Abstract: Exopolysaccharides contribute significantly to attachment and biofilm formation in the opportunisitc pathogen Pseudomonas aeruginosa. The Psl polysaccharide, which is synthesized by the polysaccharide synthesis locus (psl), is required for biofilm formation in non-mucoid strains that do not rely on alginate as the principal biofilm polysaccharide. In-frame deletion and complementation studies of individual psl genes revealed that 11 psl genes, pslACDEFGHIJKL, are required for Psl production and surface attachment. We also present the first structural analysis of the psl-dependent polysaccharide, which consists of a repeating pentasaccharide containing d-mannose, d-glucose and l-rhamnose: [See text]. In addition, we identified the sugar nucleotide precursors involved in Psl generation and demonstrated the requirement for GDP-d-mannose, UDP-d-glucose and dTDP-l-rhamnose in Psl production and surface attachment. Finally, genetic analyses revealed that wbpW restored Psl production in a pslB mutant and pslB promoted A-band LPS synthesis in a wbpW mutant, indicating functional redundancy and overlapping roles for these two enzymes. The structural and genetic data presented here provide a basis for further investigation of the Psl proteins and potential roles for Psl in the biology and pathogenesis of P. aeruginosa.

335 citations


Authors

Showing all 1273 results

NameH-indexPapersCitations
Tong Wu6659119325
Bernard Coq501487111
Antoine Aboukaïs432186290
Karine Anselme431399671
Edward J. Anthony432155659
Pierre Collet413227871
Jean-François Lamonier411414625
Serge Berthoin411406291
Jean Demaison394096858
Guillaume Garçon391023692
Pierre Hardouin38936145
Sami Souissi381978837
John C. Wenger371126644
François G. Schmitt371894953
Pirouz Shirali37863253
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202319
2022101
2021153
2020156
2019170
2018152