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Ecological adaptation and acclimatization of natural phytoplankters within a nutrient gradient were studied in an oligotrophic pond with special reference to the diel fluctuations of cell volumes and frequency of dividing cells (FDC) at each season using an in situ gradostat. The predominant phytoplankters (Cryptomonas ovata in spring and autumn, Crucigenia(More)
A new in situ gradostat was devised to study the dynamics of natural communities having nutrient gradients within aquatic habitats. This semi-enclosed mesocosm consisted of three components: i.e. three transparent, concentric cylindrical culture chambers, with diameters of 70, 60 and 40 cm, and 20 cm deep, supported by four flotation buoys, a medium(More)
The Gram stain method was applied to the photometric characterization of aquatic bacterial populations with a charge-coupled device camera and an image analyzer. Escherichia coli and Bacillus subtilis were used as standards of typical gram-negative and gram-positive bacteria, respectively. A mounting agent to obtain clear images of Gram-stained bacteria on(More)
  • H Seki
  • 1982
The monitoring of eutrophication can be performed by measuring the turnover times of amino acids in watermasses using the Wright-Hobbie uptake kinetics approach.The substrate specificity of amino acids varies greater with turnover times than with sampling location in watermasses with a certain water type. Thus a specific substrate among the essential amino(More)
—A portable human skin detector based on active infrared illumination is proposed in this paper. The system aims at detecting human skin in realtime based on two infrared bands under various background illumination conditions. Safe, realtime and robust detection is realized by combining the active pulse illumination of two low power LEDs, i.e. 1070nm and(More)
  • H Seki
  • 1986
The population density of bacterioplankton and the concentration of dissolved organic carbon combined is a useful indicator to monitor subtle variations in the amount of eutrophication. Both parameters can be measured precisely and readily by widely accepted routine techniques that require little skill. Thresholds of eutrophication can be established to(More)
Species succession of a natural bacterial community was indicated by the Gram stain index (GSI) using an experimental nutrient gradient in an oligotrophic pond created with an in situ gradostat. Various trophic conditions, ranging from eutrophic to mesotrophic, were formed experimentally with continuous inflow of sterile peptone solution in the gradostat,(More)
  • H Seki
  • 1976
A method, based on quantitating 14CO2 produced from [14C]hexadecane, has been developed for estimating the rate of hexadecane decomposition in seawater of Tokyo Bay during the summer stagnation period. The rate of hexadecane decomposition was from 0.1 to 1.3 mug/h per liter of seawater at the surface layer in the polluted gyre of the inner part of Tokyo Bay(More)
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