The standing crop and productive structure of phytoplankton communities in some lakes of central Japan have mainly been investigated by chlorophyll extraction method.
1.Remarkable difference of chlorophyll content with lake type was ascertained. In summer, average values of the chlorophyll content in epilimnion are in maximum ca. 50mg/m
3 in eutrophic lakes, and less than 1mg/m
3 in oligotrophic and dystrophic ones.
2. The chlorophyll content in lakes varied not only in quantity but also in the vertical distribution, -the productive structure of phytoplankton community-, of which two main types, i.e., homogeneous distribution and stratum one (Fig. 3), were recognized and both the types appeared alter nately in the course of year, The process of the transformation of the two types was analysed on the basis of metabolism of phytoplankton.
3.The standing crop of phytoplankton was investigated with the amount of chlorophyll. It showed that in summer the seston was mainly composed of phytoplankton but in winter mainly inorganic matter and non-chlorophyllic organisms.
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