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  • 1
    Electronic Resource
    Electronic Resource
    Glutamine Synthetase activity in limnetic phytoplankton (1996)
    Springer
    Aquatic sciences 58 (1996), S. 103-119 
    Details
    ISSN: 1420-9055
    Keywords: Lake ; phytoplankton ; N-assimilation ; N-uptake ; Glutamine Synthetase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The seasonal distribution of potential Glutamine Synthetase (GS) activities was studied in eutrophic Lake Aydat (France, Massif Central). The validity of this index of N-assimilation in field studies was tested by a comparison with the coupling of distributions of inorganic nitrogen uptake rate based on14C incorporation into proteins and the amino acids to protein ratio together with several abiotic and biotic parameters. The potential GS activities recorded during the seasonal succession of phytoplankton (characterized by the dominance of diatoms) were in the same order of magnitude of those reported from the very poor literature on this subject. Over high N-NO 3 - availability, the potential GS activities recorded were close to indirect estimations of N-uptake rates. During nitrogen depletion, high potential GS activities (which coincided with a development of small diatoms) were recorded suggesting that cell metabolism adapted to N-nutrient constraints. In addition, potential GS activity evolved concomitantly to other indicators of N-uptake and N-status. However, N-assimilation rates based on the enzymatic approach were lower than those obtained through indirect isotopic determination of uptakes rates. We suggest therefore that GS was not the unique pathway of ammonium assimilation in field populations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877110
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  • 2
    Electronic Resource
    Electronic Resource
    Contribution a l'etude limnologique du lac pavin (France) I: Facteurs abiotiques et phytoplancton (1980)
    Springer
    Hydrobiologia 68 (1980), S. 167-189 
    Details
    ISSN: 1573-5117
    Keywords: lake ; physico-chemistry ; phytoplankton ; mathematical analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Located at 1197 m in the Massif Central Français, lake Pavin has a volcanic origin. It is a dimictic and meromictic lake of 44 ha of area and 92 m depth. Samples were collected bimonthly at 8 depth (0 to 40 m) from May 1973 to April 1974. Physicochemical parameters (light energy, temperature, pH, conductivity, Oxygen, Nitrogen, Phosphorus, Silice, Carbon) and dynamics of phytoplanktonic populations (cells counts, standing crop, primary production, photosynthetic pigments) were studied. The waters of this lake are clear, with low conductivity and high concentrations of oxygen in the first 40 meters. In a water column, 0–40 meters, the means of nitrogen concentrations are between 45 and 279 µg/l and between 0 and 161 µg/l for phosphorus. Phytoplankton is caracterised by an important development of Diatoms (Melosira italica subsp. subarctica and Asterionella formosa) in winter and spring, opposed to low standing crops of Chlorophycea (Coenococcus, Sphaerocystis, Chlamydomonas) in summer. The annual mean of primary production is about 360 mg C ass./m2.J. The highes values of the activity coefficient (P/B) are found during the development of Chlorophycea, but photosynthetic efficiency is maximum in winter for Diatom populations. To summarize physico-chemical parameters and phytoplankton relationships, a synthetical mathematical model was made by Principal Components Analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00019702
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  • 3
    Electronic Resource
    Electronic Resource
    Growth rate of four freshwater algae in relation to light and temperature (1990)
    Springer
    Hydrobiologia 207 (1990), S. 221-226 
    Details
    ISSN: 1573-5117
    Keywords: phytoplankton ; growth rate ; model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Four algae of freshwater phytoplankton were studied in monospecific culture: Chlorella vulgaris, Fragilaria crotonensis, Staurastrum pingue and Synechocystis minima. Experiments were performed to determine the growth rate over a wide range of light intensities (5–800 µE m−2 s−1, 15/9 light/dark photoperiod) and temperatures (10–35 °C). The results provide a set of parameters (particularly the maximal growth rate associated to optimal conditions of light and temperature) for a three-equation model used to described the growth rate response of a non-nutrient-limited culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00041459
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  • 4
    Electronic Resource
    Electronic Resource
    Diel changes in the alkaline phosphatase activity of bacteria and phytoplankton in the hypereutrophic Villerest reservoir (Roanne, France) (1995)
    Springer
    Hydrobiologia 300-301 (1995), S. 49-56 
    Details
    ISSN: 1573-5117
    Keywords: reservoir ; phytoplankton ; bacteria ; alkaline phosphatase activity ; diel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The diel changes of the size fractioned alkaline phosphatase activity (APA) were studied in relation to several abiotic and biotic factors in Villerest reservoir (located on the Loire river, near the city of Roanne, France), bihourly during two days in July 1992. The APA measured in this work exceeded considerably those reported in the literature, suggesting that dissolved mineral phosphorus was not available to microorganisms. At 1 m, the APA was primarily due to bacteria which actively assimilated organic P compounds released by photosynthetic algal metabolism. At 5, 10 and 20 m, the APA was predominantly algal. The high concentrations in SRP (soluble reactive phosphorus) would indicate that orthophosphates were not bioavailable. The reverse (i. e availability to phytoplankton) would have resulted in undetectable levels of P-PO inf4 sup3− due to the massive proliferation of algae in Villerest reservoir.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00024447
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  • 5
    Electronic Resource
    Electronic Resource
    Diel changes in the biochemical composition of the particulate matter coupled with several parameters in the hypereutrophic Villerest reservoir (Roanne, France) (1995)
    Springer
    Hydrobiologia 300-301 (1995), S. 85-91 
    Details
    ISSN: 1573-5117
    Keywords: reservoirs ; phytoplankton ; biochemical composition ; diel changes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The diel changes of the biochemical composition of particulate matter was studied in Villerest reservoir (located on the Loire river, near the city of Roanne, France) during July 92. Several biomass and metabolic indicators (proteins, carbohydrates, lipids, chlorophyll a and primary production) were assessed bihourly over 2 days. Since the P/C is largely recognized as a good integrator of the metabolic functions of the cells, we examined its distribution pattern concomitantly with aforementioned parameters. The results demonstrated enhanced P/C ratios clearly indicating that nutrients were sufficiently available for growth. In addition, this index showed a diel significant variation with levels higher in the night than in the day. Moreover, these results suggest that phytoplankton species during the night used the day-synthesized carbohydrates to insure the cell metabolic functioning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00024450
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  • 6
    Electronic Resource
    Electronic Resource
    Experimental study of the impacts of silver carp on plankton communities of eutrophic Villerest reservoir (France) (1999)
    Springer
    Aquatic ecology 33 (1999), S. 193-204 
    Details
    ISSN: 1573-5125
    Keywords: biomanipulation ; eutrophic reservoir ; mesocosm ; phytoplankton ; silver carp ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined the impact of five silver carp biomass levels (0, 8, 16, 20, and 32 g m−3) on plankton communities and water quality of Villerest eutrophic reservoir (France). We realized the experiments using outdoor mesocosms. The presence of silver carp led to changes in zooplankton and phytoplankton assemblages. High fish biomass strongly reduced cladoceran abundance (through predation). Silver carp inefficiently grazed down particles 〈 20 μm. More importantly, however, the suppression of herbivorous cladocerans resulted in the increase of small size algae which were relieved from grazing and benefit from high nutrient concentrations. In contrast, in mesocosms without fish, the dominance of cladocerans (mainly Daphnia) controlled small size algae and probably also larger size algae (colonial chlorophytes, cyanobacteria). Thus, the Secchi disc transparency increased markedly. Through cascade effects, the modification of grazers communities led to changes in the utilization patterns of the added nutrients by phytoplankton communities. In high fish biomass treatments, nutrients were more efficiently accumulated into particulate fractions compared with no-fish and low-fish biomass treatments that were characterized by higher dissolved nutrients concentrations. Zooplankton was an essential source of food for silver carp. The productivity of zooplankton sustained a moderate silver carp biomass (up to 16 g m−3). In the presence of the highest fish biomass, the productivity of zooplankton was not large enough and silver carps fed on additional phytoplankton. Although mesocosms with high fish biomass were characterized by a slight cyanobacteria development compared with other fish mesocosms, silver carp was not effective in reducing cyanobacteria dominance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009984713183
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