Seasonal succession of phytoplankton in Lake Yogo over 2 years: effect of artificial manipulation |
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Authors: | Hajime Tsukada Shigeo Tsujimura Hiroyuki Nakahara |
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Institution: | (1) Department of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kitashirakawaoiwakecho, Sakyo-ku, Kyoto 606-8502, Japan;(2) Lake Biwa Environmental Research Institute, Otsu, Japan |
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Abstract: | We studied the seasonal variation in concentrations of nutrients and phytoplankton in Lake Yogo for 2 years, from May 2000
to May 2002, in order to clarify the seasonal succession of phytoplankton and the effect of various manipulations on it. It
was revealed that in spite of the installation of aeration systems and the pumping of mesotrophic water from Lake Biwa during
the summer season, the trophic state of Lake Yogo overall has not improved during the past few decades. However, the pumping
of water from Lake Biwa did affect the concentrations of nutrients and the periods of cyanobacterial bloom during the summer.
The pumping period was different in each year, and the cyanobacterial bloom occurred during the period without pumping in
both years. The aeration destratification was not strong enough to prevent cyanobacterial blooms. Cyanobacteria and Bacillariophyceae
contributed most to the phytoplankton biomass in both years. Aphanizomenon, Anabaena, and Microcystis were the main genera among cyanobacteria. The bloom of Aphanizomenon or Anabaena occurred early in the summer, and was then replaced by Microcystis. Aphanizomenon was almost always present, and often formed bloom even in winter. The seasonal succession of Bacillariophyceae was almost
the same in both years and was well categorized: winter-growing species such as Aulacoseira pusilla (F. Meister) Tuji et Houki and species of Thalassiosiraceae, spring-growing species such as Asterionella formosa Hassall, Fragilaria crotonensis Kitton, and Synedra cf. acus, and fall-growing species such as Aulacoseira ambigua (Grunow) Simonsen, and Aulacoseira granulata (Ehrenb.) Simonsen. |
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Keywords: | Phytoplankton community Artificial manipulation Waterbloom Seasonal succession Water temperature |
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