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Registros recuperados: 28
Primeira ... 12 ... Última
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Relation concentration-débit et évolution temporelle du nitrate dans 25 rivières de la région Bretagne (France) ArchiMer
Guillaud, Jean-francois; Bouriel, Luc.
The study of the twenty-five largest rivers of Brittany showed that nitrate concentrations are positively correlated with river flow, in 90 % of the cases. The hydrogeological characteristics of the watersheds had an influence on these relationships. In this respect, river basins characterized by prevalent surficial water runoff exhibited higher correlation coefficients and lower lag times between river flow sequences and nitrate concentrations. The multi-year trend in riverine nitrate concentrations indicated a fourfold increase over 30 years. Nevertheless, 80% of rivers exhibited a recent decrease in nitrate concentrations, independent of inter-annual river flow fluctuations. The highest annual rates of nitrate decrease corresponded to river basins for...
Tipo: Text Palavras-chave: Eutrophication; River flow; Multiple regression analysis; Multi year trend; Nitrate; Brittany; Eutrophisation; Débit fluvial; Régression multiple; Évolution pluriannuelle; Nitrate; Bretagne.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-2568.pdf
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Satellite and in situ observations of a late winter phytoplankton bloom, in the northern Bay of Biscay ArchiMer
Gohin, Francis; Lampert, Luis; Guillaud, Jean-francois; Herbland, Alain; Nezan, Elisabeth.
A phytoplankton bloom was observed in late winter 2000, on the continental shelf offshore of southern Brittany, in northwestern Bay of Biscay. This bloom appeared initially along the 120-m isobath, in stratified and clear waters, at the interface between the oceanic water and the plumes of southern Brittany rivers (mainly the Loire and Vilaine). The development of the bloom was triggered by favourable meteorological conditions, characterised by solar irradiance reaching the maximum level expected for that period of the year. Outside of the bloom area, the phytoplankton photosynthesis was irradiance limited: inshore, because of the stronger attenuation of the light; offshore, because of the weak stratification. The hydrological conditions at the onset of...
Tipo: Text Palavras-chave: Bay of Biscay; Coscinodiscus; Algal bloom; Phytoplankton; Ocean colour; Satellite sensing.
Ano: 2003 URL: http://archimer.ifremer.fr/doc/2003/publication-463.pdf
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Seasonal variation of riverine nutrient inputs in the northern Bay of Biscay (France), and patterns of marine phytoplankton response ArchiMer
Guillaud, Jean-francois; Aminot, Alain; Delmas, Daniel; Gohin, Francis; Lunven, Michel; Labry, Claire; Herbland, Alain.
Seasonal variations in nutrient inputs are described for the main rivers (Loire and Vilaine) flowing into the northern Bay of Biscay. The river plumes are high in N/P ratio in late winter and spring, but not in the inner plume during the summer. Conservative behavior results in most nutrients entering the estuary and eventually reaching the coastal zone. Temporal and spatial aspects of phytoplankton growth and nutrient uptake in the northern Bay of Biscay distinguish the central area of salinity 34 from the plume area. The first diatom bloom appears offshore in late winter, at the edge of the river plumes, taking advantage of haline stratification and anticyclonic "weather windows." In spring, when the central area of the northern shelf is...
Tipo: Text Palavras-chave: Northern Bay of Biscay; Phytoplankton; Continental shelf; Riverine inputs; Nutrients.
Ano: 2008 URL: http://archimer.ifremer.fr/doc/2007/publication-2354.pdf
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Spéciation du phosphore et apports en baie de Seine orientale ArchiMer
Aminot, Alain; Guillaud, Jean-francois; Andrieux, Francoise.
The Bay of Seine receives the French river with the highest nutrient concentrations, especially phosphorus. Dissolved (phosphate) and particulate phosphorus fluxes have been determined from fortnightly serial data collected by the Port Autonome de Rouen. These determinants exhibit behaviour opposite to that of the river flow: phosphate concentration decreases hyperbolically and particulate phosphorus increases linearily. An approach based on the rate of domestic effluent treatment agrees well (20%) with the measured phosphate flux. The determination of the main particulate phosphorus forms (adsorbed, apatite, non-apatite inorganic, organic) was undertaken over the whole estuarine salinity range. The speciation of particulate phosphorus exhibits a great...
Tipo: Text Palavras-chave: PHOSPHORUS; SPECIATION; FLUX; ESTUARY; SEINE.
Ano: 1993 URL: http://archimer.ifremer.fr/doc/00100/21126/18746.pdf
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Suivi à long terme des apports de matières organiques et nutritives par les effluents urbains de Morlaix ArchiMer
Aminot, Alain; Guillaud, Jean-francois; Le Guellec, Anne-marie.
La qualité des effluents de la station d'épuration de Morlaix a été suivie pendant six mois. Les rendements ont été évalués et comparés à ceux observés précédemment avant réfection du réseau de collecte. Les flux sont comparés à ceux de la rivière en période pluvieuse et en période sèche.
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Ano: 1990 URL: http://archimer.ifremer.fr/doc/00080/19135/16730.pdf
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Two- or three-layered box-models versus fine 3D models for coastal ecological modelling? A comparative study in the English Channel (Western Europe) ArchiMer
Menesguen, Alain; Cugier, Philippe; Loyer, Sophie; Vanhoutte Brunier, Alice; Hoch, Thierry; Guillaud, Jean-francois; Gohin, Francis.
The general trend in ecosystem modelling is to improve the spatial resolution by shifting from rough box-models to fine 3D models. Despite the continuous speeding-up of computing, 3D models involving numerous state variables may remain intractable, especially for parameter calibration, when processes with long half-life periods (i.e, from years to decades) are introduced, such as the behaviour of organic matter in sediment and population dynamics of benthic species. In these cases, a first approach can be provided by fast-running box-models, if they take into account the most crucial hydrodynamic properties of the system. In a macrotidal shelf sea such as the English Channel, the long-term horizontal transport can be summarized by the tidal residual...
Tipo: Text Palavras-chave: English Channel; Stratification; Diatom/dinoflagellate succession; 3D model; Layered box model.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-2315.pdf
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Vers une modélisation opérationnelle du devenir des nutriments dans la bande côtière bretonne ArchiMer
Pénard, Cédric; Ménesguen, Alain; Dumas, Franck; Guillaud, Jean-francois.
Eutrophication of French Brittany coastal shelf is a recurrent problem, more and more worrying. This eutrophication exhibits two main forms :– “green tides”, which are constituted by local proliferations and strandings of green macro-algae (particularly the Ulva species) in nitrogen-enriched areas.– phytoplanktonic blooms, which are responsible of coloured water events. Toxic species can be present (Pseudonitzschia, Alexandrium, Dinophysis), and induce banning of shellfish consumption.Several programs and directives compel authorities to initiate actions in order to diminish these problems. (WFD, OSPAR). This implies a better understanding of these phenomena.This work deals with the influences of the plumes of Loire, Vilaine and bay of Brest rivers (Elorn...
Tipo: Text
Ano: 2007 URL: https://archimer.ifremer.fr/doc/00480/59153/61782.pdf
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Vertical distribution of phytoplankton communities and relationships with physico-chemical parameters resolved by a fine scale sampler ArchiMer
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
Registros recuperados: 28
Primeira ... 12 ... Última
 

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