Data/hora: 12/06/2024 15:28:31

Provedor de dados: | Institutional Archive of Ifreme (ArchiMer)
País: | France
Título: | Fonctionnement des marais maritimes atlantiques: échanges d'énergie et effets des flux aquacoles diffus
Autores: | Bel Hassen, Malika.
Data: | 2000-02-29
Ano: | 2000
Palavras-chave: | Aquaculture; Exportation; Matière dissoute; Fiers d'Ars; Systèmes d'Information Géographique; Importation; Usages; Lumière; Micorphytobenthos; Modélisation; Nutriments; Matière organique; Matière particulaire; Phytoplancton; Sédimentation; Aquaculture; Export; Dissolved matter; Fier d'Ars Bay; Geographic Information Systems; Import; Land use; Light; Microphytobenthos; Modelling; Nutrients; Organic matter; Particulate matter; Phytoplankton; Sedimentation.
Resumo: | French estuaries, from the Atlantic coast to the English channel, have been characterized by a poor phytoplankton biomass. The turbidity has always been considered as the limiting factor for phytoplankton. Estuarine ecosystems are situated at the boundary between the land and the sea. Consequently, they are subject to an enrichment by nutrient loadings from upland ecosystems. Although it has been demonstrated that a part of the nutrient loadings support an important benthic production. The part, which escapes to the estuarine benthic and planktonic food web and is exported to adjacent estuarine ecosystems, still remains undetermined. Quantifying the nu trient and particulate matter exchange between a macrotidal Bay, the Fier d'Ars, and the adjacent ocean was among the objectives of this study. The technique already performed was based on the regression estimation, usi ng the hydrometeorological parameters as predictor variables of instantaneous nutrjent fluxes . This method allowed us to establish the direction of net flux with tight confidence bounds on net annual flux. It also takes into account a large variability, inherent to the periodic phenomenon, such as hydrodynamics and also to nonperiodic variations, relative to the meteorological fluctuations. The assessment of nonpoint source loadings was performed using a simple model that accounts for the spatial pattern in topography and land use. This model was based on spatial analyses using Geographie Information System (GIS ) databases. The spatial distribution of nitrogen and phosphorus loadings was performed using the kriging interpolator. An 8-direction-model, particularly its derivative function, the weighted accumulation model, allowed the assessment of nutrient loading in each instream location. The study of the phytoplankton standing crops, highlighted a low biomass throughout the year. Showing a pattern of recurring variations within factors regulating phytoplankton biomass, which incriminated both light and nutrient availability (nitrogen and phosphorus). It was demonstrated that the study system produced more inorganic nitrogen than can be consumed, the excess was exported to the adjacent coastal ecosystem. A net export of inorganic dissolved carbon was also assessed. The system imported particulate matter, more than 70% was minerai forrn, which engendered a progressive sedimentation of the system. The GIS- based assessment of nu trient loading highlighted the major contribution of intensive activities to the enrichment of the coastal area with nitrogen loading. Atmospheric loading represented low proportions ( 4% - 12%) of the potential aquacultural loading. Nevertheless, internal processes, such as denitrification and nitrogen fixation, susceptible to reduce the quantities exported to the ocean, are not enough weil studied to establish the total balance of the system. Perspectives are proposed in this way, they concern the spatialisation of the different internaI processes with the determination of their weight locally.
Tipo: | Text
Idioma: | Francês

Identificador:

http://archimer.ifremer.fr/doc/00450/56185/57738.pdf

http://archimer.ifremer.fr/doc/00450/56185/

Editor: | Université de Bretagne Occidentale
Formato: | application/pdf

Fonte:

2000 Université de Bretagne Occidentale

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