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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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| Morin, P; Lecorre, P; Marty, Y; Lhelguen, S. |
| The evolution of nutrient distribution has been followed in spring on the Armorican shelf in association with hydrological features and phytoplankton development. Data were collected on a sampling grid of 20 stations on the continental shelf during four cruises (SATIR 8 to 11) between March and June 1982. Haline fronts (Ushant haline front, coastal haline front) were found in late winter and early spring; their outlines follow closely the outlines of the summer thermal fronts. The origin of these haline fronts comes mainly from the outflow towards the English Channel of the waters of the Loire river on the South Brittany shelf. At this time of the year, a conservative mixing is observed between offshore waters with relatively low nutrient concentrations... |
| Tipo: Text |
Palavras-chave: NUTRIENTS; CONTINENTAL SHELF; NORTH-WEST EUROPE; TIDAL FRONTS; PHYTOPLANKTON. |
| Ano: 1991 |
URL: http://archimer.ifremer.fr/doc/00101/21256/18869.pdf |
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| Lambert, Ce; Nicolas, E; Veron, A; Buatmenard, P; Klinkhammer, G; Lecorre, P; Morin, P. |
| We have investigated total Pb distributions in the water column from various sites in the north-east Atlantic. Sea water samples were collected during the Fluxatlante cruise in 1985. Total Pb ranged from 35 to 45 ng.l-1 (170-220 pmol l-1) in surface waters and decreased with depth in a manner consistent with previous findings. The high concentrations in surface waters probably reflect an important anthropogenic input of Pb from the atmosphere. Concentrations of total Pb are higher than in the western Atlantic. This difference seems to be closely related to the difference in atmospheric inputs of anthropogenic Pb. Three of the stations exhibit a specific Pb excess at the depth of the Mediterranean waters outflowing in the intermediate Atlantic waters; such... |
| Tipo: Text |
Palavras-chave: TOTAL PB; NORTH ATLANTIC; MEDDY; POLLUTION. |
| Ano: 1991 |
URL: http://archimer.ifremer.fr/doc/00102/21279/18888.pdf |
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