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| Registros recuperados: 11 | |
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| Rabitti, S; Bianchi, F; Boldrin, A; Daros, L; Socal, G; Totti, C. |
| Some results of a cruise carried out within the Project on the Physical Oceanography of the Eastern Mediterranean (POEM BC-091, October 1991) are reported and discussed. The major aim of this work was to study, in the upper layers of the Ionian basin the distribution of particulate matter, phytoplankton and bacteria, with emphasis on the influence of North Atlantic Water. Some tentative conclusions may be drawn from the results: the examined situation (October) is representative of the final stage of a probably annual cycle of production in an oligotrophic system; the well-developed Deep Chlorophyll Maximum between 75 and 100 m (mainly due to degradation products) does not match the biomass maximum. Possible explanations of this are: a) phytoplankton... |
| Tipo: Text |
Palavras-chave: IONIAN SEA; PARTICULATE MATTER; CHLOROPHYLL; PHYTOPLANKTON; BACTERIA. |
| Ano: 1994 |
URL: http://archimer.ifremer.fr/doc/00098/20892/18506.pdf |
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| Jenkinson, Ian. |
| Deformation and mixing in any medium are controlled by its viscosity and elasticity. The present study provides preliminary information, at oceanic shear rates, on the viscosity and elasticity in the bulk phase of seawater. Thirty-two samples of seawater, obtained on cruises at four times of year in a meso-oligotrophic part of the Mediterranean, were measured for bulk-phase viscoelastic properties in an oscillating-shear Couette flow with measuring gap 0.5 mm, over shear rates gamma from 0.0021 to 0.286 s-1. Fifteen samples were obtained on a single cruise in the German Bight, North Sea, when Phaeocystis blooms were taking place, and these were similarly measured at gamma from 0.0021 to 0.973 s-1. The bulk-phase measurements suffered interference... |
| Tipo: Text |
Palavras-chave: RHEOLOGY; PHYTOPLANKTON; ORGANIC AGGREGATES; SURFACE MICROLAYER; DISSOLVED ORGANIC MATTER (DOM). |
| Ano: 1993 |
URL: http://archimer.ifremer.fr/doc/00099/21057/18683.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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| Ignatiades, L. |
| This paper describes the quantitative relationships between phytoplankton abundance and species number, dominance and niche breadth during ''bloom'' and ''non-bloom'' stages in a coastal marine environment of the Eastern Mediterranean Sea. Analysis of the relative frequency distribution of the species breadth per sample showed each assemblage to be a mixture of species with narrow (< 3), moderate (4-8) and broad (> 8) niche breadth. Assemblages with higher (> 30) numbers of species tended to have a greater proportion (up to 25-30 %) of species with narrow breadth in relation to the samples with fewer taxa. In ''bloom'' assemblages, the total cell abundance increased above the concentration level of ''non-bloom'' assemblages (baseline population)... |
| Tipo: Text |
Palavras-chave: PHYTOPLANKTON; DOMINANCE; NICHE BREADTH; BLOOM. |
| Ano: 1994 |
URL: http://archimer.ifremer.fr/doc/00099/21022/18648.pdf |
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| Hoch, Thierry; Menesguen, Alain; Bentley, D. |
| A simple model of the nitrogen cycle in the Channel is proposed. Based on the long-term circulation, this box-model permits the description of the spring phytoplankton bloom in the whole Channel. Spring western thermal stratification has not been taken into account; consequently, the earliest phytoplanktonic development is observed in the eastern Channel, followed by the western, deeper part. This model also shows the influence of nutrient supply from the rivers on the Channel ecosystem, and particularly the influence of the river Seine on the chlorophyll concentrations along the eastern French coast. Comparison of calculated data with measurements shows a fairly good agreement in the eastern Channel but discrepancies are encountered for the western part.... |
| Tipo: Text |
Palavras-chave: CHANNEL; BOX-MODEL; NITROGEN; PHYTOPLANKTON. |
| Ano: 1993 |
URL: http://archimer.ifremer.fr/doc/00100/21128/18748.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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| Sournia, Alain; Belin, Catherine; Billard, Chantal; Catherine, Martial; Erard-le Denn, Evelyne; Fresnel, Jacqueline; Lassus, Patrick; Pastoureaud, Annie; Soulard, René. |
| A dinoflagellate has produced green-water events along the Atlantic and English Channel coasts of France since 1982. It differs morphologically from each of the 12 taxa or so of green gymnodinoid dinoflagellates previously known. As some morphological details, as well as their variability, remain to be ascertained, this organism is illustrated and described here under the provisional designation of Gymnodinium "sp. 1982". The presence of chlorophyll b has been confirmed by HPLC analysis but it could not be ascertained whether true chloroplasts are present, or symbionts. The distribution is coastal and estuarine. The number and intensity of the outbreaks may be related to river runoff and to the amount of preceding rainfall. An encysted stage is described.... |
| Tipo: Text |
Palavras-chave: Bloom; Océan Atlantique; Manche; Morphologie; Chlorophylle b; Répartition géographique; Zone côtière; Milieu marin; Phytoplancton; Basse Normandie; France; Europe; Pyrrophycophyta; Algae; Thallophyta; Gymnodinium; BLOOMS; DINOFLAGELLATES; GREEN WATERS; GYMNODINIUM; PHYTOPLANKTON. |
| Ano: 1992 |
URL: http://archimer.ifremer.fr/doc/00133/24470/22487.pdf |
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| Dauchez, S; Queguiner, B; Treguer, P; Zeyons, C. |
| Nitrogen (N-15) and carbon (C-14) uptake rates and hydrological, chemical and biological parameters were monitored at a single station during spring (March-April 1989) in a coastal eutrophic ecosystem of western Europe : the Bay of Brest. Before the spring growth of phytoplankton populations, total nitrogen and carbon uptake rates were low (almost-equal-to 0.3-mu-mol C.1(-1).h-1 and almost-equal-to 0.025-mu-mol N.l(-1).h-1). During the spring bloom, these uptake rates reached high values (0.5-mu-mol C.1(-1).h-1 and 0.28-mu-mol N.1(-1).h-1); at this time, nitrate was the main source of nitrogen production, although relative preference index (RPI) values showed that ammonium was the preferred nitrogen form for phytoplankton (RPI (NO3) < 1 ; RPI (NH4) >... |
| Tipo: Text |
Palavras-chave: CARBON UPTAKE; EUTROPHIC ECOSYSTEM; NITROGEN UPTAKE; PARTICULATE MATTER; PHYTOPLANKTON. |
| Ano: 1991 |
URL: http://archimer.ifremer.fr/doc/00102/21282/18891.pdf |
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| Andre, Jm; Morel, A. |
| In a previous study (Bricaud and Morel, Oceanologica Acta, 1987), a reflectance model developed for oceanic Case 1 waters was introduced into CZCS data processing, mainly with the aim of improving the atmospheric correction scheme and permitting discrimination between Case 1 and turbid Case 2 waters. The present paper, not limited to CZCS, examines the possible extension of the use of this reflectance model. In particular, it is proposed that the relationships required in iterative computations when estimating marine radiances in the four (visible) channels be those which derive from the model rather than the empirical expressions. Also, in order to ensure an internal coherency, it is proposed to operate the modelled relationships between the reflectance... |
| Tipo: Text |
Palavras-chave: REMOTE-SENSING; OCEAN COLOR; REFLECTANCE MODEL; PHYTOPLANKTON; AEROSOL. |
| Ano: 1991 |
URL: http://archimer.ifremer.fr/doc/00101/21260/18871.pdf |
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| Druet, C; Zielinski, A. |
| The paper presents a one-dimensional mathematical model describing the vertical distribution of chlorophyll a and nutrients in a stratified sea. The model takes into account the most important physical, chemical and biological processes controlling the evolution of this function. This model was tested with data obtained in situ during the Baltic research expedition of R/V Prof. Siedlecki in 1980. The vertical distributions of temperature field, chlorophyll a and nutrient concentrations were taken as initial conditions for various simulations. The results of numerical simulations explained the influence of biological processes on the variability of phytoplankton concentration in time and space under various dynamic conditions. The variable dynamic... |
| Tipo: Text |
Palavras-chave: MATHEMATICAL MODEL; STRATIFIED SEA; TURBULENT DIFFUSION; PHYTOPLANKTON. |
| Ano: 1994 |
URL: http://archimer.ifremer.fr/doc/00099/21036/18662.pdf |
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| Registros recuperados: 11 | |
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