Data/hora: 05/06/2024 14:34:11

Provedor de dados: | 5
País: | France
Título: | Inventaire des ulves en Bretagne. Année 1997. Rapport de synthese
Autores: | Merceron, Michel.
Data: | 1998-02
Ano: | 1998
Palavras-chave: | Bretagne; Nitrate; Prolifération; Ulve; Eutrophisation; Brittany; Nitrate; Proliferation; Ulva; Eutrophication.
Resumo: | The yearly study of Ulva in Brittany aims at building a time series of its proliferations and corresponding nutrient loadings. The goal is to detect results of wilful loading reductions, and to distinguish them from natural variations. This first actually quantified study is the starting bench-mark of the process. Forty-five concerned sites were listed in 1997. They are nearly the same as in 1988, 1991 and 1994 (previous rough census). The Côtes d'Armor and then the Finistère are the most affected departments. The Morbihan is less and file et Vilaine not at all. Ulva biomass was precisely quantified in about fifteen locations during the growing season, along with nitrogen loadings of local streams (mostly nitrate). The fluxes of nitrogen - the limiting factor in association with a long flushing time of seawater and a large sandy beach - were very low during the end of spring and summer beginning of 1997. So in the mid part of the bay of Douarnenez, they were only 55-60 % of 1996. The 1997 season is to be considered as a dry reference year. But it seems that it did not induce a substantial lowering of the Ulva biomass, at least in the bay of Saint-Brieuc (possibly due to a saturation of the site by nutrients, or winds favouring algae beaching ...). On the Brittany coasts as a whole, the Ulva observed stocks amounted to 20 000 metric tons, and the collected production to 43 000 t. The bays of Saint-Brieuc and Lannion were the most loaded. The ratio between the maximum Ulva biomass (observed or collected) and that, theoretical, obtained by converting the whole nitrogen flux of June to Ulva was computed. This index is very different among the sites. It displays their more or less efficient ability to make the available nitrogen to be utilized by Ulva proliferation. An offshore Ulva stock probably also exists. Its study must begin in 1998. In future, algae biomass on beaches must be estimated from mid-June to mid-July just before summer collecting. In order to pick up the nitrogen fluxes of summer (short) floods, it is recommended to fit out the most irregular streams with discharge recorders.
Tipo: | Text
Idioma: | Francês

Identificador:

http://archimer.ifremer.fr/doc/1998/rapport-1580.pdf

http://archimer.ifremer.fr/doc/00000/1580/

Formato: | application/pdf

Fonte:

1998 Ifremer

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