Difference of the epilithic microorganism communities on the upper surface and the lower surface of stones in Lake Biwa and the Koza River were investigated.
As regards to the results of the studies made at Lake Biwa in December 1965 and March 1966, the commu-nities of the upper surfaces were evidently different from those of the lower surfaces. The upper surface communities consist mainly of diatoms, green algae and blue-green algae, while in the lower surface the com-munities consist of protozoa and bacteria. (cf. Tab. I and Tab. 2) The components of the upper surface communities are mainly the producers and those of the lower are mainly the comsumers and the decomposers.
It is because, I suppose, near the lower side of the stone, water movement is slower, organic materials deposit more, and also the oxygen is probably less, compared with the upper surface.
If any storm comes, such conditions near the stones will be changed. Detritus will be cleaned from the shore bottom, attached microorganisms will be also removed. The stone surface communities start their new succession. Example of this early state of success sion is the case (Tab. 3) observed in September 1966. In this example the lower surface communities are little different from the upper surface ones.
As for the case of May 1966 at the Koza River, the lower surface communities is little different from the upper one, especially in the rapids of the river. (Tab. 4)
As for the case of August 1971 in the same river,
Homoeothrix janthina's community is found on the upper surface and the diatoms are dominant on the lower surface. (Tab. 5 and Fig. 7)
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