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  • 1
    Electronic Resource
    Electronic Resource
    A short synthesis of the tricyclic ring system of vinigrol (1993)
    s.l. : American Chemical Society
    The @journal of organic chemistry 58 (1993), S. 2349-2350 
    Details
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jo00061a002
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  • 2
    Electronic Resource
    Electronic Resource
    Estimation of bacterial production through the coupling of (methyl 3H) Thymidine incorporation and several parameters over a Microcystis aeruginosa bloom in a hypereutrophic reservoir (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Lakes & reservoirs 3 (1998), S. 0 
    Details
    ISSN: 1440-1770
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geography
    Notes: The coupling of the changes in bacterial quantitative and metabolic aspects during Microcystis aeruginosa bloom conditions together with several environmental parameters was studied in the hypereutrophic Villerest reservoir, France. Bacterial abundance varied from 5.20 to 21.28 × 106 bacteria-mL−1, while bacterial biomass ranged between 75 and 507 μg C mL−1. These results confirmed the highly eutrophic status of the Villerest reservoir. The relative quantitative importance of attached bacteria increased as Microcystis proliferated. Methyl-3H incorporation and D-(U-14C) glucose uptake varied from 8.99 to 60.57 × 106 cells-mL−1, and 0.016 to 1.587 μg CL−1 h−1, respectively. Correlations between several abiotic and biotic parameters showed that phytoplankton regulated bacterial growth by releasing organic carbon which is directly uptaken by heterotrophic bacteria. In the hypolimnion, the sedimentation of decaying algae represented a substantial substrate for bacterial growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1770.1998.tb00030.x
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  • 3
    Electronic Resource
    Electronic Resource
    Proteolytic and glycolytic activities in size-fractionated surface water samples from an oligotrophic reservoir in relation to plankton communities (1999)
    Springer
    Aquatic sciences 61 (1999), S. 279-292 
    Details
    ISSN: 1420-9055
    Keywords: Key words: Proteolytic activity, glycolytic activities, bacteria, organic matter, reservoir.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract: From February to August 1996, the following parameters were determined in surface water samples from an oligotrophic reservoir: concentrations of dissolved combined amino acids (DCAA), monosaccharides (DFCHO) and polysaccharides (DCCHO); activities of glycolytic and proteolytic enzymes associated with three size fractions (0-0.2 μm, 0.2-2 μm, and 2-100 μm); densities and biomass of free-living and attached bacteria, nanoflagellates, and metazoan zooplankton. The mean concentrations of DCAA, DFCHO and DCCHO were 2.7, 0.5 and 1.4 mg C l-1 respectively. Both βGlcA and αGlcA showed a high substrate affinity. The enzyme activities associated with all size fractions fluctuated throughout the year. Highest activities were generally associated with the 2-100 μm fraction; the mean percentages of leucine-aminopeptidase (LeuA), β-glucosidase (βGlcA), α-glucosidase (αGlcA) and β-N-acetylglucosaminidase (βGlcNAcA) activities were 58%, 62%, 76%, and 59%, respectively. Activities of αGlcA and βGlcNAcA in the 0.2-2 μm fraction were correlated with the abundance of free-living picobacteria (bacteria 〈2 μm). The biomass-specific activity of attached bacteria was 18 to 64 fold higher for attached compared to free-living bacteria. The abundances of autotrophic and mixotrophic nanoflagellates (ANF) were correlated with LeuA (r = 0.59, P 〈 0.05) and the βGlcA (r = 0.64, P 〈 0.05) activities in the 2-100 μm fraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000270050066
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  • 4
    Electronic Resource
    Electronic Resource
    Numerical modeling of thermal stratification in a lake reservoir. Methodology and case study (2000)
    Springer
    Aquatic sciences 62 (2000), S. 105-124 
    Details
    ISSN: 1420-9055
    Keywords: Key words: Numerical modeling, hydrodynamics, lake.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract: A numerical model of the hydrodynamic and thermal structure of an artificial lake was designed and developed as a basis for an ecological water-quality model. It allows the quantification of the vertical mixing processes that govern not only the thermal structure but also the nutrient exchanges, and more generally the distribution of dissolved and particulate matter between the different parts of the lake. The vertical temperature profiles were calculated by solving the one-dimensional heat transfer equation that takes into account the internal heat sources and sinks, advection due to inflow and outflow and the molecular and eddy diffusions. A finite-difference discretization of first-order in time and second-order in space was chosen. The numerical time-step was three hours and layers were one-meter in thickness. These time- and space-scales are well-suited to perform a precise simulation of the different processes occurring over a seasonal period. Moreover, this simulation requires only a reasonable amount of computer time.¶This model was used to study an artificial lake, (i.e. a reservoir), located in the high Loire valley (Roanne, France). To precisely identify the physical processes followed with an accurate numerical modeling, on-site data were acquired intensively over three years. Temperatures were monitored hourly at 11 different levels in the three main reaches of the reservoir to study the lake hydrodynamics and thermal behaviour. Meterological measurements were made every 20 minutes. One-year data were used for calibration, whereas the model was validated using the data collected over the other two years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000270050001
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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Examination through a principal component analysis of the phosphorus exchanges between sediments and water in trophically different reservoirs (1995)
    Springer
    Hydrobiologia 300-301 (1995), S. 383-389 
    Details
    ISSN: 1573-5117
    Keywords: reservoirs ; phosphorus ; sediments ; exchanges ; euthrophication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé Les échanges de phosphore au niveau de l'interface eau-sédiment couplés á la distribution temporelle de divers éléments chimiques et biologiques ont été étudiés dans divers réservoirs de niveaux trophiques différents, au Maroc et en France. Nos résultats mettent clairement en évidence une influence directe de l'environnement physico-chimique, de la nature géologique des bassins versants et de l'état trophique du lac sur la dynamique du phosphore au sein de cette interface. De plus, il apparait que dans le lac hypereutrophe de Villerest (Roanne, France), le phosphore est majoritairement complexé au fer alors que dans les retenues marocaines, ce sont les complexes phosphore-calcium qui prédominent. Nous préconisons un contrôle drastique des apports en phosphore á travers l'installation et la multiplication d'unités de déphosphatation afin d'éviter d'une part, la prolifération massive de la Cyanobactérie Microcystis aeruginosa á Villetest (Aleya et al., 1994) et d'autre part la dissociation des complexes phhosphore-calcium au sein des retenues marocaines avec libération de phosphore biodisponible.
    Notes: Abstract Phosphorus exchange at the sediment-water interface coupled with several parameters were assessed in several reservoirs with geologically different catchment basins and different trophic status in Morocco and France. The results showed that these exchanges were regulated by a combination of factors: physical chemical variability of the environment, the geological composition of catchment basins and the trophic status of the lake. In the hypereutrophic Villerest, iron-bound phosphorus is the major form of phosphorus trapped by the sediment whereas, in Moroccan reservoirs, calcium-bound phosphorus prevailed. We suggest that a drastic control of phosphorus inputs into the waters must be done through a large program of dephosphatization of tributaries to avoid Microcystis aeruginosa bloom formation in Villerest (Aleya et al., 1993) and calcium-bound phosphorus dissociation in Moroccan reservoirs with upward release of bioavailable phosphorus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00024479
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  • 7
    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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  • 8
    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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  • 9
    Electronic Resource
    Electronic Resource
    Seasonal changes in alkaline phosphatase activity of bacteria and microalgae in Lake Pavin (Massif Central, France) (1997)
    Springer
    Hydrobiologia 347 (1997), S. 175-195 
    Details
    ISSN: 1573-5117
    Keywords: lake ; bacteria ; microalgae ; alkalinephosphatase activity ; seasonal and diel changes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seasonal changes in alkalinephosphatase activity of bacteria and microalgae werestudied in the dimictic Lake Pavin (Massif Central,France), to test whetherthis activity is primarily algal or bacterial andwhether the APA presents seasonal variations coupledwith abiotic and biotic variables. Samples werecollected at different depths from May 1992 to May1993. The specific phosphatase activities wereanalysed spectrophotometrically with p-NitrophenylPhosphate (p-NPP) as substrate and were related to theprotein concentrations. No correlation was foundbetween alkaline phosphatase activity and solublereactive phosphorus (SRP) concentrations across anannual cycle. The specific activities of the smallclass (0.2–1.2 μm) were the highest and thecontribution of this picoplanktonic size class(0.2–1.2 μm) increased with depth. In addition, thelinear correlations between alkaline phosphataseactivity and protein concentration seemed to indicatethat most of these enzymes are constitutive. However,it cannot be excluded that the high phosphorusconcentrations repress APA.Finally, the measure of APA does not seem to be avalid quantitative test of the deficiency ofphosphorus for aquatic microorganisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003044008455
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  • 10
    Electronic Resource
    Electronic Resource
    Répartition des rotifères dans deux lacs-tourbières du Massif Central (France) (1985)
    Springer
    Hydrobiologia 128 (1985), S. 265-276 
    Details
    ISSN: 1573-5117
    Keywords: rotifers ; peat-bog ecosystem ; distribution ; species associations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In rotifer communities of two french peat-bogs, characteristic species associations can be described for each stage in the formation of this ecosystem. The oligotrophic lowmoor with Sphagnum angustifolium has the highest proportion of characteristic species. The affinity between the open water fauna (used as a standard) and the Sphagnum fauna decreases with a gradient in water content. The latter was a dominant factor in the distribution of rotifer species in the peat-bog.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00006823
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