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  • 1
    Electronic Resource
    Electronic Resource
    Parallel plastic tank experiments with cultures of marine diatoms (1977)
    Springer
    Helgoland marine research 30 (1977), S. 201-216 
    Details
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The reproductibility of tank experiments concerning unicellular marine algal development was analyzed by means of parallel experiments with cultures ofThalassiosira rotula andSkeletonema costatum, using large flexible plastic tanks under semi-natural conditions. The tanks (3–4 m3, 4–5 m deep) were exposed in the German Bight at a station in the outer harbour of helgoland. The water was obtained from the open North Sea in towable tanks; it was filtered (plate filter), enriched with nitrate (20–30 μgat dm−3), phosphate (1.3–2.3 μgat dm−3) and silicate (15–23 μgat dm−3)-nearly natural springtime concentrations in this area-and inoculated with 103–105 cells dm−3. The water was mixed with non-metal stirring equipment. Within 5 days, concentrations of 106–107 cells dm−3 in an exponential growth phase were obtained. In experiments withT. rotula a parallel development was achieved in spite of some contamination by surrounding water. This is the case for nearly all parameters analyzed (nutrient salts, phytoplankton, bacteria, C, N and particulate carbohydrates). The heterotrophic bacteria, which were determined by means of the plate method, reached concentrations of up to 106 (T. rotula) and 105 (S. costatum) CFU cm−3, respectively. They showed a consistent retrograde development at diatom concentrations above a certain level. The crop did not increase again until the diatoms had reached the stationary phase. During exponential growth ofT. rotula (G=8.9–11.7 h) a partially synchronous cell division was observed. There were also rhythms with respect to cell size (pervalvar axes) and chain length (number of cells). For the experiments withS. costatum (G=10–11.4 h) diurnal variations of cell size and chain length occurred. The present results indicate acceptable reproducibility of algal development and related phenomena in enclosed water bodies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02207836
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  • 2
    Electronic Resource
    Electronic Resource
    Experimentelle Untersuchungen zur Ökologie der marinen Kieselalge Thalassiosira rotula. II. Der Einfluß des Salzgehaltes (1974)
    Springer
    Marine biology 27 (1974), S. 287-298 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of salinity (8 to 38‰) on the marine plankton diatom Thalassiosira rotula Meunier were investigated with respect to different temperature and light conditions. Two ecological aspects were examined separately: (1) the effect of various salinities, constant over a long period, was studied using well adapted cultures; (2) mixing processes were simulated by transferring cell chains from water of 33.9 or 20‰ S into lower salinities, as well as from 33.9 into 38‰ S. At 12° and 17°C, growth occurred at salinities from 12 to 38‰. In cold water (6°C), T. rotula did not grow below 16‰ S. Generation time was not influenced by salinities within the tolerance range if adapted cultures were grown under optimal illumination (1000 lux, light-dark cycle of 14:10 h; 12°C) or temperature (17°C; 2000 lux, light-dark cycle of 14:10 h). With increasing illumination or decreasing temperature, the other factors remaining constant, maximum growth rates were obtained with a salinity range of 20 to 32‰. Various salinities affected division rates most obviously if cultures were grown under continuous illumination; the optimum for cell division then ranged from 24 to 28‰ S only. Using adapted cultures again, the effect of different salinities on final cell yield is presumably more intense than their influence on generation time. T. rotula responded to sudden salinity changes only if transferred from water of 20‰ S into lower concentrations and from 33.9 into 38‰ S. Particularly at 12 and 38‰ S, growth rate and colony size (cells per chain) were reduced during the first few days. Increase of generation time and decrease of chain size occur coincidentally. The influence of different salinities on the occurrence of T. rotula in the sea is discussed in conjunction with experimental results on other ecological factors, and the present results are compared with the few available data obtained in nature by other authors. Accordingly, in the sea, a salinity range of 20 to 33‰ should prove optimal for T. rotula, 34 to 38‰ S would presumably represent still adequate conditions, while below 20‰ S T. rotula would probably rarely or never occur.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00394364
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  • 3
    Electronic Resource
    Electronic Resource
    Experimentelle Untersuchungen zur Ökologie der marinen Kieselalge Thalassiosira rotula. I. Temperatur und Licht (1972)
    Springer
    Marine biology 13 (1972), S. 284-291 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung 1. Die marine Kieselalge Thalassiosira rotula Meunier wurde in teilsynthetischem Nordseewasser kultiviert und bei Zelldichten untersucht, die den natürlichen Planktonkonzentrationen in der Nordsee entsprechen. 2. Die Generationszeit von T. rotula wurde bei 11 verschiedenen Licht-Temperatur-Konstellationen ermittelt. Kurze Verdoppelungszeiten um 9 Std waren bei mittleren Beleuchtungsstärken (2400 Lux) an hohe Temperaturen (22°C) und bei mittleren Temperaturen (12°C) an hohe Beleuchtungsstärken (5500 Lux) geknüpft. Die längste Generationszeit betrug etwa 40 Std, bedingt durch niedere Temperaturen (4°C) oder geringe Beleuchtungsstärken (600 Lux). 3. Bei Ostende und Helgoland isolierte und zu verschiedenen Jahreszeiten (Frühjahr und Herbst) kultivierte Stämme von T. rotula wiesen die gleiche Generationszeit auf (15,5 Std bei 2400 Lux und 12°C). Außerdem blieb die Verdoppelungszeit über eine Folge von mindestens 70 Generationen hin unverändert. 4. Die Kettenlänge (Zellzahl pro Kette) von T. rotula kann durch Temperatur und Beleuchtungsstärke beeinflußt werden. Eine hohe Temperatur von 22°C hatte bei Lichtsättigung sehr kurze Zellketten zur Folge. Die geringe Beleuchtungsstärke von 1200 Lux verursachte bei mittleren Temperaturen die Bildung ungewöhnlich langer Zellketten. 5. Spezifisches Gewicht von T. rotula und Beleuchtungsstärke verhielten sich proportional zueinander. Mit zunehmender Beleuchtungsstärke vergrößerte sich die Sinkgeschwindigkeit der Kieselalge. 6. T. rotula erweist sich als Schwachlichtalge. Die optimalen Beleuchtungsstärken für die Zellteilung liegen zwischen 1000 und 3000 Lux. Die Art erreicht nur bei sehr begrenzten Licht-Temperatur-Konstellationen Generationszeiten, die eine größere Beteiligung am Phytoplanktonbestand im Meere ermöglichen. Günstigste Entwicklungsbedingungen werden bei etwa 14°C und 2000 bis 3000 Lux erwartet.
    Notes: Abstract The marine plankton diatom Thalassiosira rotula Meunier was isolated from the North Sea and cultivated in enriched sea water. The influence of temperature and light was investigated with regard to generation time, sinking rate and colony size (cells per chain). Petri dishes containing 10 ml culture medium were used as culture vessels for experimental work. Cell concentrations during experiments are comparable to natural concentrations of many North Sea plankton diatoms. Generation time was investigated using 11 different combinations of temperature and light. The doubling time varies between 9 h (2400 lux, 22°C; 5500 lux, 12°C) and 40 h (2400 lux, 4°C; 600 lux, 12°C). Two different isolates from Ostend and Helgoland, cultivated at different seasons (spring and autumn), exhibit the same generation time (15.5 h; 2400 lux, 12°C). Furthermore, doubling time does not change over a period of 70 generations. Colony size may be influenced by temperature and light intensity. High temperature (22°C) combined with light intensity. High temperature (22°C) combined with light saturation causes very short cells chains, low light intensity (1200 lux) unusually long cell chains. The specific gravity of T. rotula is proportional to light intensity. With increasing light intensity the sinking rate also increases. T. rotula prefers low light intensities, with an optimal range presumably between 1000 and 3000 lux. Generation times effecting a large cell density are limited by special constellations of temperature and light, which are rarely found in the sea. Optimum growth rates in the sea should be possible near 14°C and 2000 to 3000 lux.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00348075
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  • 4
    Electronic Resource
    Electronic Resource
    The development of a natural plankton population in an outdoor tank with nutrient-poor sea water. I. Phytoplankton succession (1977)
    Springer
    Marine biology 43 (1977), S. 1-17 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Due to complex hydrodynamic and biological inhomogeneities, the phytoplankton species succession cannot be satisfactorily observed, apart from the seasonal blooms which occur in temperate waters. Large flexible plastic tanks have proved to be useful for such observations. In 1972, for 28 days, a phytoplankton succession in nutrient-poor water in the outer harbor of Helgoland was observed in a flexible plastic tank (3 m3). During this period, 3 phytoplankton biomass maxima were formed with many significant correlations. In the first 7 days the ammonia concentration decreased from over 6 to 2 μ mol 1-1 for 14 days. The nitrate concentration remained in the range of 3–6 μ mol 1-1 and then fell abruptly to 0–2 μ mol 1-1. The phosphate concentration was about 0.1 μ mol 1-1. Lauderia borealis dominated the first period, and its increase was significantly correlated with the decrease in ammonia. The diatom was succeeded by two dinoflagellates, Dinophysis acuminata and Prorocentrum micans. The last period of the experiment was characterized by a stronger development of Rhizosolenia species. The rapid recovery of the crop in the nutrient-poor water points to intensive remineralization processes. The irregular occurrence of ammonia near the surface was correlated with the appearance of Noctiluca miliaris at this depth. It is expected that repetitions of this type of experiment will permit further explanations of statistical correlations which are not yet clear. As a first step, in order to test hypotheses, a correlation analysis was employed to eliminate the statistically non-significant correlations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392567
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