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  • 1
    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
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  • 2
    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
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  • 3
    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
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  • 4
    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
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