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| Registros recuperados: 19 | |
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| Labry, Claire; Youenou, Agnes; Delmas, Daniel; Michelon, Pascale. |
| The speciation of particulate phosphorus (TPP) into inorganic (PIP) and organic phosphorus (POP), has been scarcely investigated in suspended particulate matter (SPM), contrary to numerous sediment studies. This work evaluates the actual capacity of methods for TPP, POP and PIP determination in SPM to measure efficiently and specifically each pool. Methods were tested on a range of plankton-associated organic and inorganic P compounds, on microalgal cultures and estuarine samples. Then results are specifically discussed reviewing P speciation in phytoplankton. For TPP analysis, the method of Solorzano and Sharp (1980) is recommended compared with that of Aspila et al. (1976), originally dedicated to sediment, as there is one step less, the protocol is more... |
| Tipo: Text |
Palavras-chave: Phosphorus; Speciation; Waters; Phytoplankton; HTC; CWO. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00149/26046/26385.pdf |
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| Arzul, Genevieve; Videau, Christiane; Bodennec, Guy; Crassous, Marie-pierre; Youenou, Agnes. |
| Pour mieux connaître les facteurs qui agissent sur les interactions trophiques entre le phytoplancton et le milieu nutritif, nous avons étudié la capacité hétérotrophe du phytoplancton en conditions contrôlées, non axéniques, au laboratoire. Les expériences réalisées avec la [U-14C] glutamine, étaient basées sur l'étude des vitesses d'assimilation. Les résultats obtenus avec deux espèces du genre Gymnodinium et une diatomée ont été vérifiés lors d'efflorescences en eau côtière et estuarienne, montrant l'adaptation des algues au milieu riche en substances organiques et leur capacité hétérotrophe en fonction de l'éclairement. L'effet de l'éclairement sur la capacité phagotrophe de Gymnodinium a été observé au laboratoire. L'étude réalisée sur les particules... |
| Tipo: Text |
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| Ano: 2002 |
URL: http://archimer.ifremer.fr/doc/00105/21599/19179.pdf |
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| Labry, Claire; Erard-le Denn, Evelyne; Chapelle, Annie; Fauchot, Juliette; Youenou, Agnes; Crassous, Marie-pierre; Le Grand, Jacqueline; Lorgeoux, Benedicte. |
| The understanding of the dominance of one species with respect to others is a pertinent challenge in HAB growth dynamics studies and the nutrient supply mode is one of the factors potentially involved. The competition for phosphorus (P) between a toxic species, Alexandrium minutum, and a non-toxic species, Heterocapsa triquetra, was studied (1) along a gradient of P depletion, (2) testing different P depletion degrees before a single PO4 supply and (3) experimenting different PO4 supply frequencies. In conditions Of PO4 depletion, H. triquetra stopped growing after two days both in monospecific and mixed batch cultures whereas A. minutum grew progressively from day 2 until the end of the experiment. This time-lag growth of A. minutum is associated to its... |
| Tipo: Text |
Palavras-chave: Semi continuous culture; Batch culture; Ecophysiology; Pulse; Phosphorus storage; Dinoflagellates; Heterocapsa triquetra; Alexandrium minutum. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-4067.pdf |
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| Labry, Claire; Delmas, Daniel; Moriceau, Brivaela; Gallinari, Morgane; Quere, Julien; Youenou, Agnes. |
| Phosphorus (P) limitation of phytoplankton growth is known to affect the accumulation and release of carbohydrates (CHO) by micro-algae. However, relatively little is known about the fate of algal exudates, notably their bacterial degradation. The CHO chemical characterization is also not exhaustive, especially in ‘functional’ pools relevant for phytoplankton physiology (particulate reserve [R] or structural [S] CHO) and for bacterial degradation (dissolved mono- [MDCHO] and polysaccharides [P-DCHO]). In this study, we investigated how P depletion and repletion affect the CHO composition in diatom Thalassiosira weissflogii cultures, and the shortterm response of free and diatom-attached bacteria in terms of abundance and potential βglucosidase activity... |
| Tipo: Text |
Palavras-chave: P limitation; Phytoplankton; Diatom; Bacteria; Mineralization; Carbohydrate; Glucosidase. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00628/74045/73532.pdf |
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| Labry, Claire; Erard-le Denn, Evelyne; Chapelle, Annie; Youenou, Agnes; Crassous, Marie Pierre; Martin-jezequel, Véronique; Le Grand, Jacqueline. |
| Suite à un premier criblage des facteurs environnementaux favorables à la croissance d'Alexandrium minutum comparativement à celle d'une espèce compétitrice en rivière de Penzé, Heterocapsa triquetra (rapport ART3 2002-2003) cette étude vise à préciser et quantifier les réponses physiologiques respectives des deux espèces à différentes conditions d'apports en phosphate (taux de croissance, vitesse d'assimilation des phosphates, capacité à stocker le phosphore intracellulaire). Elle montre qu'Alexandrium minutum a plutôt une stratégie de « stockage », capable d'assimiler rapidement le phosphate après un apport mais le stockant pour une meilleure croissance ultérieure quand la ressource sera à nouveau épuisée. Comparativement, Heterocapsa triquetra aurait,... |
| Tipo: Text |
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| Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/00105/21598/19178.pdf |
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| Chapelle, Annie; Le Bec, Claude; Amzil, Zouher; Dreanno, Catherine; Guillou, Laure; Klouch, Khadidja; Labry, Claire; Le Gac, Mickael; Pineau-guillou, Lucia; Siano, Raffaele; Abernot, Chantal; Andrieux, Francoise; Caradec, Florian; Destombe, Christophe; Dia, A.; Doner, Anne; Duval, Julia; Gouriou, Jeremie; Lazure, Pascal; Le Brun, Luc; Le Gal, Dominique; Malestroit, Pascale; Petton, Sebastien; Plus, Martin; Quere, Julien; Savar, Veronique; Schmitt, Sophie; Terre, A.; Youenou, Agnes. |
| Suite à l’événement de grande ampleur d’efflorescence d’Alexandrium minutum et des toxicités associées en Rade de Brest en 2012, un projet a été élaboré avec la Région Bretagne dans le cadre du développement du port de Brest. L’Ifremer a organisé un échantillonnage dans l’estuaire de la rivière de Daoulas, zone la plus touchée en 2012, au cours des printemps-été 2013 et 2014. Un suivi de la présence d’A. minutum dans les sédiments a également été réalisé en hiver 2014. De ces suivis, des mesures réalisées au laboratoire à ce jour, des simulations du modèle Prévimer ainsi que des résultats du réseau Rephy et Velyger, il ressort que: * La rade de Brest peut aujourd’hui être considérée comme une zone à risque pour Alexandrium minutum. En effet, depuis 2012... |
| Tipo: Text |
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| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00254/36487/35029.pdf |
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| Labry, Claire; Delmas, Daniel; Youenou, Agnes; Quere, Julien; Leynaert, Aude; Fraisse, Stephane; Raimonet, Melanie; Ragueneau, Olivier. |
| The occurrence of alkaline phosphatase activity (APA) that hydrolyses organic phosphorus into phosphate (PO4) is commonly related to PO4 deficiency of oceanic, coastal and fresh waters. APA is almost never investigated in PO4-rich estuaries, since very low activities are expected to occur. As a consequence, microbial mineralization of organic phosphorus into PO4 has often been ignored in estuaries. In this study, we examined the importance of potential APA and the associated microbial dynamics in two estuaries, the Aulne and the Elorn (Northwestern France), presenting two different levels of PO4 concentrations. Unexpected high potential APA was observed in both estuaries. Values ranged from 50 to 506 nmol L−1 h−1, which range is usually found in very... |
| Tipo: Text |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00337/44840/44428.pdf |
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| Lunven, Michel; Guillaud, Jean-francois; Crassous, Marie Pierre; Youenou, Agnes; Gohin, Francis; Huret, Martin; Danielou, Marie-madeleine; Kerouel, Roger; Labry, Claire; Aminot, Alain. |
| Inscrite dans le cadre du Grand Défi Golfe de Gascogne, la campagne VILOIR a été réalisée du 19 au 26 Juin 2003 à bord du Côtes de la Manche avec pour objectif l’étude en période estivale des structures hydrologiques et phytoplanctoniques des panaches de la Loire et de la Vilaine. Elle fait suite, sur la même thématique, à la campagne hivernale NUTRIGAS (2001) et à la campagne printanière GASPROD (2002). |
| Tipo: Text |
Palavras-chave: Surveillance; Littoral; Phytoplancton; Phycotoxines; Bretagne; Pays de Loire. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/00144/25494/23648.pdf |
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| Andrieux, Francoise; Azandegbe, Afi; Caradec, Florian; Philippon, Xavier; Kerouel, Roger; Youenou, Agnes; Nicolas, Jean-louis. |
| This study aims to compare the impact of oyster cultures on diagenetic processes and the phosphorus cycle in the sediments of the Aber Benoît and the Rivière d’Auray, estuary of Brittany, France. Our results showed clear evidence of the seasonal impact of oyster cultures on sediment characteristics (grain size, organic matter parameters), and the phosphorus cycle, especially in the Aber Benoît. At this site, seasonal variations of sulfide and Fe concentrations in pore waters, as well as Fe-P concentrations in the solid-phase highlighted a shift from a system governed by iron reduction (Reference) to a system governed by sulphate reduction (Beneath Oyster). This could be partly explained by the increase in labile organic matter (ie, biodeposits) beneath... |
| Tipo: Text |
Palavras-chave: Sediment; Phosphorus; Sulfide; Dissolved Fe/P ratios; Labile organic matter; Oyster cultures. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00209/32003/30441.pdf |
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| Lema, Anais Kimberley; Metegnier, Gabriel; Quéré, Julien; Latimier, Marie; Youenou, Agnes; Lambert, Christophe; Fauchot, Juliette; Le Gac, Mickael. |
| Untangling the functional basis of divergence between closely related species is a step towards understanding species dynamics within communities at both the evolutionary and ecological scales. We investigated cellular (i.e: growth, domoic acid production, nutrient consumption) and molecular (transcriptomic analyses) responses to varying nutrient concentrations across several strains belonging to three species of the toxic diatom genus Pseudo-nitzschia. Three main results were obtained. First, strains from the same species displayed similar transcriptomic, but not necessarily cellular, responses to the experimental conditions. It showed the importance of considering intra-specific diversity to investigate functional divergence between species. Second, a... |
| Tipo: Text |
Palavras-chave: Phenotype; Transcriptomics; Pseudo-nitzschia; Divergence; Nutrients. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00482/59392/62157.pdf |
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| Gentien, Patrick; Lunven, Michel; Lazure, Pascal; Youenou, Agnes; Crassous, Marie-pierre. |
| Karenia mikimotoi is one of the most common red-tide dinoflagellates proliferating in the eastern North Atlantic and around Japan. Kills of marine fauna are associated with its blooms. In mixed water columns it migrates vertically, while in stratified water columns, the population remains confined within pycnocline layers. Wind events, increasing mixing and agitation initiate declines in its populations. This paper is focused on the formulation of mortality rate relative to shear rate. Autotoxicity is demonstrated by the use of a synthetic toxin. Bioconvection observed in cultures allows the establishment of a trade-off between phototropism, which leads to the local accumulation of cells, and their autotoxicity, which would prevent cell concentration. The... |
| Tipo: Text |
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| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2436.pdf |
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| Lunven, Michel; Guillaud, Jean-francois; Youenou, Agnes; Crassous, Marie-pierre; Berric, Roger; Le Gall, Erwan; Kerouel, Roger; Labry, Claire; Aminot, Alain. |
| A new Fine Scale Sampler (FSS) was designed and used in the Loire River plume (Bay of Biscay, France) in order to study phytoplankton distribution in highly stratified water columns. The FSS consists of a linear array of 15 sampling bottles, set horizontally at 20 cm intervals. Data acquired from the CTD and fluorescence probe of the FSS enable it to be precisely positioned at the depth of the highest density gradient or at the chlorophyll a maximum. The FSS made it possible to investigate fine scale vertical distribution of phytoplankton and relationships with water density, nutrient concentrations or light availability, for spring and summer conditions. Under spring conditions, the entire upper layer exhibited a dominant diatom population (Chaetoceros... |
| Tipo: Text |
Palavras-chave: Plankton patchiness; Density discontinuity; Sampling; Thin layer; Nutrients; Phytoplankton. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/2005/publication-533.pdf |
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| Andrieux-loyer, Francoise; Philippon, Xavier; Bally, Gabriel; Kerouel, Roger; Youenou, Agnes; Le Grand, Jacqueline. |
| The macrotidal estuary of Penze (Brittany, Western part of the Channel, France) has been subjected to recurrent annual toxic blooms of Alexandrium minutum since 1988. This study aims to specify the phosphorus dynamics and bioavailability in sediments in order to improve our understanding of Alexandrium occurrences. Sediment-P pools and diffusive phosphate fluxes were studied under similar hydrodynamic conditions, in the intermediate estuary in May, June and July 2003 and along the salinity gradient from August 2004 to June 2005. The results highlight a decrease in bioavailable phosphorus (iron and organic bound) from the inner part of the estuary seaward. The ratio of iron-bound phosphorus to iron-oxyhydroxides is lower in the inner and intermediate... |
| Tipo: Text |
Palavras-chave: Sequential extraction; Sediment phosphorus; Pore water; Phosphate fluxes; Estuary; Alexandrium minutum. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-4306.pdf |
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| Daniel, Anne; Kerouel, Roger; Aminot, Alain; Youenou, Agnes. |
| Cet essai interlaboratoire (EIL) pour l’analyse des sels nutritifs en milieu marin a été organisé par le laboratoire DYNECO/PELAGOS de l’IFREMER le 14 février 2006. Il a été proposé en septembre 2005 aux Laboratoires Environnement Ressources (LER) de l’IFREMER, aux sous-traitants ou collaborateurs des LER, aux laboratoires effectuant des analyses dans le cadre du RNO-hydrologie, aux laboratoires du CNRS participant à SOMLIT (Service d’Observation du Milieu LITtoral) et aux laboratoires de l’IRD. Les 26 laboratoires qui ont participé à cet essai sont listés en Annexe 1. Aucune consigne n’a été donnée sur le choix de la technique analytique : chaque laboratoire a utilisé sa méthode de routine. |
| Tipo: Text |
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| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/00020/13144/10186.pdf |
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| Aoyama, M; Becker, S; Dai, M; Daimon, H; Gordon, L; Kasai, H; Kerouel, Roger; Kress, N; Masten, D; Murata, A; Nagai, N; Ogawa, H; Ota, H; Saito, H; Saito, K; Shimizu, T; Takano, H; Tsuda, A; Yokouchi, K; Youenou, Agnes. |
| An intercomparison exercise was conducted using the recently developed Reference Material for Nutrients in Seawater (RMNS). Discrepancies of reported values among laboratories were greater than the homogeneity of RMNS samples and the reported analytical precision of nutrients. The variability of in-house standards of the participating laboratories might be the most likely source of interlaboratory discrepancies. Therefore, the use of common reference materials, i.e. certified RM, is essential to establish and improve the comparability of nutrient data of the world's oceans. |
| Tipo: Text |
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| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-3010.pdf |
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| Farrell, Hazel; Gentien, Patrick; Fernand, Liam; Lazure, Pascal; Lunven, Michel; Youenou, Agnes; Reguera, Beatriz; Raine, Robin. |
| Investigations into the phytoplankton of the Bay of Biscay in July 2006 revealed an extensive bloom of an unidentified haptophyte species. High-resolution sampling techniques identified the region in the vicinity of the mouth of the Loire estuary as an area of high (106–107 cells l−1) cell densities of the haptophyte in a thin sub-surface layer. This organism dominated the phytoplankton population regionally. Measurements of the vertical distribution of horizontal shear showed that the population, located at ca. 20 m depth, was confined to a layer lying between two density discontinuities with high shear. Physical measurements indicated that the population was being advected southeastwards, along the coast. Seaward spreading of the population was also... |
| Tipo: Text |
Palavras-chave: Haptophyte; Bay of Biscay; Horizontal dispersal; Thin layers. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00160/27129/25327.pdf |
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| Lunven, Michel; Guillaud, Jean-francois; Youenou, Agnes; Crassous, Marie-pierre; Berric, Roger; Le Gall, Erwan; Kerouel, Roger; Labry, Claire; Aminot, Alain. |
| Many studies in coastal areas have shown the existence of thin chemical and biological layers. Their thickness and vertical extension are mainly controlled by hydrological and physical forcing. An accurate description of the phytoplankton communities growing within these layers is difficult to obtain without a well-adapted sampling system. A new Fine Scale Sampler (FSS) has been designed in Ifremer in order to study phytoplankton distribution and associated dissolved properties in high stratified water column. This FSS consists in a vertical array of 15 sampling bottles, horizontally laid with 20 cm intervals. Data acquired from a CTD and Fluorescence probe provide a precise FSS positioning at the depth of highest density gradient or at chlorophyll a... |
| Tipo: Text |
Palavras-chave: Surveillance; Littoral; Phytoplancton; Phycotoxine. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/00144/25493/23647.pdf |
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| Registros recuperados: 19 | |
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