Limnological Studies on the Three Dammed Lakes, constructed in the Watercourse of the Monobe River, Kochi Prefecture

概要

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Three reservoirs in the Monobe River were surveyed in July 1973, and February and March, of 1974. The rate of water exchange is low in the Nagase Reservoir and high in the other two, the Sugita and Yoshino, both of which have no thermal stratification and have the retention time less than 2 hours. In July the plankton of the Nagase Reservoir is considerably different from the other two. In the former, Chroococcus limneticus (blue-green alga) and Synedra ulna (diatom) are dominant. In the Sugita and the Yoshino Reservoirs, however, there are found two dominant diatoms, Melosira varians and Cymbella tumida, both of which seem to have been liberated from the flora attached to the upper river bed. The two reservoirs in the lower reaches have no plankton of the lakes themselves, because the mean staying time of water is too short. In February the plankton of the lower two lakes is the same as that of the upper lake, though Peridinium willei did not occur in the lower two lakes. This dinoflagellida makes the water red in the Nagase Reservoir in March. Nagase, Sugita, Yoshino Reservoirs were investigated in 1973 in regard to their benthos. Chironomus plumosus, characteristic of eutrophic lakes, was found abundantly on the bottom in the Nagase Reservoir. Cryptochironomus sp. (B) and Phaenopsectra sp. (C), both of which are characteristic species of mesotrophic lakes were found on the bottom in the Sugita and Yoshino Reservoirs.
日本陸水学会の論文