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  • shallow lakes  (5)
  • laboratory scale enclosure  (4)
  • Biosynthesis  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Phosphate uptake capacity of summer phytoplankton of the Loosdrecht Lakes in relation to phosphorus loading and irradiance (1986)
    Springer
    Aquatic ecology 20 (1986), S. 101-107 
    Details
    ISSN: 1573-5125
    Keywords: phytoplankton ; laboratory scale enclosure ; phosphorus loading ; phosphate uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Summer populations of the phytoplankton of the Loosdrecht Lakes were enclosed in laboratory scale enclosures (LSE), supplied with 7.5 μg P.l−1.d−1 and 105 μg P.l−1.d−1, respectively. The maximum initial phosphate uptake rate (Vm) was related to irradiance and primary production. At phosphate uptake saturating light-irradiance Vm values up to 4 times the Vm values in the dark were measured. The phosphate uptake capacity per unit dry weight remained more or less constant throughout the experiments in the LSE receiving the lower amount of phosphorus, and declined in the LSE receiving the higher amount of phosphorus. Within the range of Vm values measured (〈10 μg P.mg DW−1.h−1 or 1,3 μg P. μg chla −1.h−1), the growth rate of the phytoplankton was not influenced by alterations in phosphorus availability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02291155
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  • 2
    Electronic Resource
    Electronic Resource
    A comparison of primary production measurements using two laboratory systems with differences in light quality (1986)
    Springer
    Aquatic ecology 20 (1986), S. 93-99 
    Details
    ISSN: 1573-5125
    Keywords: primary production ; oxygen technique ; light quality ; incubator ; laboratory scale enclosure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Primary production measurements were carried out simultaneously, using two laboratory systems with different light conditions: (1) a'classical' incubator and (2) a Laboratory Scale Enclosure. The model used for calculating primary production (STEELE, 1965) does not correct for spectral changes caused by high phytoplankton biomass. In the incubator, light of almost all wavelengths decreased more or less according to the attenuation of total PhAR in water. In the LSE, high absorption was found of the blue light and some of the red light, which was due to the high sestonic concentration. The Steele function provided a good fit for both sets of data. The depth integrated gross production values derived from the simultaneous measurements were not significantly different.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02291154
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  • 3
    Electronic Resource
    Electronic Resource
    Optical teledetection of the vertical attenuation coefficient for downward quantum irradiance of photosynthetically available radiation in turbid inland waters (1997)
    Springer
    Aquatic ecology 31 (1997), S. 299-311 
    Details
    ISSN: 1573-5125
    Keywords: irradiance reflectance ; large rivers ; phytoplankton production ; remote sensing ; shallow lakes ; underwater light
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Depth profiles of downward quantum irradiance of photosynthetically available radiation in situ and spectral subsurface irradiance reflectance, obtained from water-leaving radiance, were determined in different inland water types. These included the large, shallow and eutrophic IJssel lagoon in the Netherlands, eighteen Dutch lakes differing in depth and trophic state, and the large, shallow and eutrophic Lake Tai in China. The attenuation coefficient for downward irradiance ranged from 0.7 to 5.4 m-1. An empirical relationship with the backscattering coefficient in the near-infrared waveband, derived from the reflectance, and three spectral reflectance band ratios explained 91% of the variation. The potential assessment of the spatial distribution of phytoplankton production through shipboard optical teledetection of the concentration of chlorophyll-a and the attenuation coefficient for downward irradiance is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009902627476
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  • 4
    Electronic Resource
    Electronic Resource
    Progress in the research of artemisinin-related antimalarials: An update (1994)
    Springer
    Pharmacy world & science 16 (1994), S. 169-180 
    Details
    ISSN: 1573-739X
    Keywords: Antimalarials ; Artemisia annua L ; Artemisinin ; Biosynthesis ; Chemistry ; Clinical trials ; Pharmacology ; Phytochemistry ; Sesquiterpenes ; Toxicology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Artemisinin, a sesquiterpene lactone endoperoxide isolated fromArtemisia annua L., and a number of its semisynthetic derivatives have shown to possess antimalarial properties. They are all eflective againstPlasmodium parasites that are resistant to the newest and commonly used antimalarial drugs. This article gives a survey of the literature dealing with artemisinin-relaled antimalarial issues that have appeared from the end of 1989 up to the beginning of 1994. A broad range of medical and pharmaceutical disciplines is covered, including phytochemical aspects like the selection of high-producing plants, analytical procedures, and plant biotechnology. Furthermore, the organic synthesis of artemisinin derivatives is discussed, as well as their mechanism of action and antimalarial activity, metabolism and pharmacokinetics, clinical studies, sideeffects and toxicology, and biological activities other than antimalarial activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01872865
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  • 5
    Electronic Resource
    Electronic Resource
    Artemisia annua L.: a source of novel antimalarial drugs (1990)
    Springer
    Pharmacy world & science 12 (1990), S. 169-181 
    Details
    ISSN: 1573-739X
    Keywords: Artemisia annua L. ; Artemisinin ; Biosynthesis ; Chemistry, analytical ; Clinical trials ; Pharmacology ; Sesquiterpene lactones ; Structure—activity relationship
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Artemisia annua L. contains artemisinin, an endoperoxide sesquiterpene lactone, mainly in its leaves and inflorescences. This compound and a series of derivatives have attracted attention because of their potential value as antimalarial drugs. In this review a survey of the currently available literature data is given. It includes phytochemical aspects, such as constituents ofA. annua, the artemisinin content during the development of the plant and its biosynthesis, isolation, analysis and stability. Total chemical synthesis of artemisinin is referred to, as well as structure—activity relationships of derivatives and simplified analogues. Pharmacological studies are summarized, including the mechanism of action, interaction of the antimalarial activity with other drugs, possible occurrence of resistance to artemisinin, clinical results, toxicological aspects, metabolism and pharmacokinetics. Finally, plant cell biotechnologyy is mentioned as a possible means to obtain plants and cell cultures with higher artemisinin contents, allowing an industrial production of pharmaceuticals containing this novel drug.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01980041
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  • 6
    Electronic Resource
    Electronic Resource
    Interspecific variation in pigmentation: implications for production estimates for shallow eutrophic lakes using an incubator (1992)
    Springer
    Hydrobiologia 238 (1992), S. 197-202 
    Details
    ISSN: 1573-5117
    Keywords: primary production ; spectral light distribution ; incubator ; laboratory scale enclosure ; Oscillatoria limnetica ; Prochlorothrix hollandica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In shallow, eutrophic Lake Loosdrecht, light attenuation and spectral changes with depth are pronounced due to high concentration of algae and tripton. Calculations of integrated daily primary production have been based on the photosynthesis-irradiance relationship (P/E-curve) obtained with the incubator technique. The suitability of this technique for estimating primary production in such a turbid lake was investigated by comparing P/E-curves for two differently pigmented algae, Oscillatoria limnetica and Prochlorothrix hollandica, in two laboratory systems differing in light regime. System (1) consisted of an incubator filled with tapwater, and system (2) was an algal culture in a laboratory scale enclosure (LSE). For O. limnetica the P/E-curves were identical. The P/E-curves for P. hollandica diverged considerably: the photosynthetic efficiency in the LSE (0.19 mg O2 (mg Chl)−1 h−1 (W m−2)−1 was about half of that obtained in the incubator (0.35 mg O2 (mg Chl)−1 h−1 (W m−2)−1. These results were explained by the interspecific variation in pigmentation. The photosynthetic efficiency of P. hollandica changed due to the dependence on the chlorophyll specific absorption for the whole photosynthetic waveband on the spectral light distribution, which for O. limnetica was approximately the same in the two light regimes. Column-integrated primary production computed with the photosynthetic characteristics of P. hollandica obtained in LSE, was 10–30% lower than the production based on incubator data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00048789
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  • 7
    Electronic Resource
    Electronic Resource
    Coupling of phytoplankton and detritus in a shallow, eutrophic lake (Lake Loosdrecht, The Netherlands) (1992)
    Springer
    Hydrobiologia 233 (1992), S. 51-59 
    Details
    ISSN: 1573-5117
    Keywords: phytoplankton ; Oscillatoria limnetica ; Prochlorothrix hollandica ; detritus ; shallow lakes ; lake restoration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An oscillating steady state is described of phytoplankton, dominated by Prochlorothrix hollandica and Oscillatoria limnetica, and sestonic detritus in shallow, eutrophic Lake Loosdrecht (The Netherlands). A steady-state model for the coupling of the phytoplankton and detritus is discussed in relation to field and experimental data on phytoplankton growth and decomposition. According to model predictions, the phytoplankton to detritus ratio decreases hyperbolically at increasing phytoplankton growth rate and is independent of a lake's trophic state. The seston in L. Loosdrecht contains more detritus than phytoplankton as will apply to many other lakes. The model provides a basis for estimating the loss rate of the detritus, including decomposition, sedimentation and hydraulic loss. In a shallow lake like L. Loosdrecht detritus will continue to influence the water quality for years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00016095
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  • 8
    Electronic Resource
    Electronic Resource
    Dynamics of phytoplankton detritus in a shallow, eutrophic lake (Lake Loosdrecht, The Netherlands) (1992)
    Springer
    Hydrobiologia 233 (1992), S. 61-67 
    Details
    ISSN: 1573-5117
    Keywords: phytoplankton ; epipelon ; Oscillatoria limnetica ; detritus ; shallow lakes ; lake restoration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A study was made of the mortality and aerobic decomposition of light- and phosphorus-limited cultures of Oscillatoria limnetica, a dominant phytoplankton species in shallow, eutrophic Lake Loosdrecht (The Netherlands). When placed in the dark at 20 °C, most cells died and lysed within twelve days. The labile organic matter was completely decomposed within three weeks. Absorbance spectra indicated that blue green algae may contributed significantly to the refractory dissolved substances in the lake. Refractory particulate matter constituted from 7 to 24% of the biomass of O. limnetica, depending on the growth rate before incubation in the dark. The decomposition rate of this fraction was 0.005 d−1. On a basis of a steady-state model of the dynamics of phytoplankton detritus, the areal organic dry weight concentration of the detritus in the lake is ca. 60 g m−2. This means the quantities of detritus in the seston and epipelon are about equal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00016096
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  • 9
    Electronic Resource
    Electronic Resource
    Characterization of the light field in laboratory scale enclosures of eutrophic lake water (Lake Loosdrecht, The Netherlands) (1992)
    Springer
    Hydrobiologia 238 (1992), S. 99-109 
    Details
    ISSN: 1573-5117
    Keywords: laboratory scale enclosure ; underwater light field ; shallow lakes ; phytoplankton ; cyanobacteria ; spectral light distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Light conditions in laboratory scale enclosures (LSE) of shallow, eutrophic Lake Loosdrecht (The Netherlands), including a method for simulating a ‘natural’ incident light course, are described. Total PAR (400–700 nm) and spectral irradiance distribution were measured at sestonic chlorophyll a and dry weight concentrations ≥ 100 mg m−3 and 16 g m−3, respectively. Phytoplankton was dominated by Oscillatoria spp. The euphotic depth (Z eu) was 0.7–1.0 m. Shortly after filling the LSE with lake water, diffuse attenuation coefficients ranged from 14 m−1 for blue to 5 m−1 for red light. Around Z eu, attenuation in the blue region was markedly lower and irradiance reflectance (R) continued to increase; these anomalies were caused by lateral incident light from the LSE's waterbath. Spectrophotometry indicated that absorption was mainly by particles, but dissolved humic substances (gilvin) were also important. The particles were likely to be dominated by detritus absorbing more blue relative to red light. Subsurface R in lake water in the LSE had a maximum around 705 nm and low values in the blue band, but was lower than that previously reported for measurements in situ. Wash-out of detritus, presumably both dissolved and particulate fractions, by flow-through with synthetic medium, greatly affected the spectral reflectance measured outside the LSE. The maximum value of R decreased from 0.022 to 0.009, and the peak shifted to 550 nm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00048778
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  • 10
    Electronic Resource
    Electronic Resource
    The ‘true’ growth efficiency of phytoplankton as influenced by light attenuation and insolation: implications of the photosynthesis-irradiance relationship (1992)
    Springer
    Hydrobiologia 238 (1992), S. 169-176 
    Details
    ISSN: 1573-5117
    Keywords: growth efficiency ; areal quantum efficiency ; light attenuation ; Oscillatoria limnetica ; shallow lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ‘true’ growth efficiency (c) relates the light energy absorbed by phytoplankton to the production of biomass corrected for constant energy requirement of maintenance. Continuous culture studies have shown that, at constant incident irradiance, the value of c for both prokaryotic and eukaryotic species is constant. Culture data for the relevant conditions of incident light may be used for directly estimating the growth rate from daily insolation of optically deep, fully mixed lakes, when the light absorption by the phytoplankton can be established. In order to examine the influence of vertical light attenuation and daily insolation on c, computations were made on a basis of a photosynthesis-irradiance curve of light-limited Oscillatoria limnetica. For steady state growth, the ‘true’ growth efficiency is linearly related to the areal quantum efficiency of photosynthesis (ϕ a ). The computations showed that ϕ a remains constant at fluctuating vertical light attenuation, no matter whether the concentration of tripton or phytoplankton changes. The effect of insolation is great: ϕ a is 0.108 mol O2/E at very low light, but only 0.014 mol O2/E at 400 W m−2 subsurface downward irradiance. The results imply that a c-value obtained from cultures for summer averaged insolation must be corrected: between cloudy and clear days the value may vary by a factor of 2. The ‘true’ growth efficiency for cultures will decrease by about 10% when the same daily irradiation is dosed sinusoidally instead of constantly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00048785
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