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Maguer, Jf; Lecorre, P; Madec, C. |
Seasonal changes in inorganic (NH4+; NO3-; NO2-) and organic (urea) nitrogen uptake were studied with N-15 as a tracer at a shallow station (depth: 22 m) in permanently well-mixed waters of the Western English Channel. Uptake of all the four nutrients was maximum in spring. Nitrate uptake accounted for a third of the total during spring phytoplankton growth, but decrease in summer. This decrease was related to the low ambient nitrate concentrations in early summer and to an inhibition of uptake by high concentrations in late summer. Ammonium was taken up in significant amounts from the beginning of spring (46 % of total uptake), increasing to 59 % in summer. In contrast with nitrate, ammonium concentrations during summer were sufficiently high to saturate... |
Tipo: Text |
Palavras-chave: Nitrogen; Uptake; Seasonal variations; Western English Channel. |
Ano: 1996 |
URL: http://archimer.ifremer.fr/doc/00096/20723/18360.pdf |
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Lhelguen, S; Madec, C; Lecorre, P. |
Uptake of nitrogenous nutrients (NO3-, NO2-, NH4+ and urea) by phytoplankton was measured over an annual cycle at a coastal station in the well-mixed waters of the western English Channel. Seasonal changes of nitrogen uptake showed a single, but spread-out, maximum in summer. The phytoplankton took up the various forms of nitrogen simultaneously. Ammonium uptake accounted for 48% of the total nitrogen uptake and was quantitatively important from the beginning of spring until early autumn. Nitrate uptake was relatively less important (32% of total nitrogen uptake) though nitrate was the major component of available inorganic nitrogen. Nitrate uptake rates were comparable to those of ammonium in winter and spring, but were much lower than the latter in... |
Tipo: Text |
Palavras-chave: NITROGEN; UPTAKE; PHYTOPLANKTON; ENGLISH CHANNEL; SEASONAL CYCLE. |
Ano: 1993 |
URL: http://archimer.ifremer.fr/doc/00100/21129/18749.pdf |
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