• Animal cells and systems
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• 제5권2호
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• pp.117-126
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• 2001

Occurence, seasonal changes and vertical distribution of the silica-scaled chrysophytes in a small fish-free pond were studied using electron microscopy (EM) and light microscopy (LM) from October 1998 to July 1999. The phytoplankton community was characterized by Chrysophyta and Cryptophyta. Ten species of the silica-scaled chrysophytes of genera Mallomonas, Synura, Chrysosphaerella and Spiniferomonas were identified by EM, and the most abundant species were Mallomonas akrokomos and M. portae-ferreae. The maximum population density of M. akrokomos was observed in December and several peaks appeared periodically at about one to two month intervals, whereas M. portae-ferreae developed the maximum density in March. The diurnal vertical distribution of M. akrokomos exhibited clear downward migration at night and slightly upward migration in the morning. A complex interaction among physico-chemical and biological factors seemed to affect the vertical distribution of M. akrokomos. However, the seasonal changes of M. akrokomos did not show significant corre1ations with the physico-chemical and some biologica1 factors. Although M. akrokomos was evenly distributed throughout the water column during some experimental periods, the diurnal patterns found in the two diurnal cycles showed consistency in that it clearly avoided the surface water during the day. This suggested that M. akrokomos may be a shade plankton with maximum densities below surface layer.

• ALGAE
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• 제17권1호
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• pp.1-9
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• 2002

Diel vertical distribution of phytoflagellates and interactions between the phytoplankton components and environmental and biological factors were studied in a small artificial pond for three days on the December 18, 1998 and April 9 to 10, 1999. The phytoplankton population was dominated by Mallomonas akrokomos of chrysophytes and Cryptomonas marssonii and Chroomonas sp. of cryptophytes. The vertical distribution of these phytoflagellates taxa exhibited clear diel migration pattern. Moreover their migration patterns are showed differential fluctuation between M. akrokomos, C. marssonii and Chroomonas sp. The later two species upward migrated in the evening as well as night, whereas the former species migrated downward. Their distinctive migration pattern was found during the night but was not observed in the morning. During daytime C. marssonii and Chroomonas sp. showed maximum density above 2 m depth but M. akrokomos below 2 m depth. The diel vertical distribution of the dominant phytoflagellates did not show significant correlation between physical, chemical and biotic factors.