Hydrobiological studies on the artificially constructed ponds (‘tamé-ike’ ponds) of japan

Abstract

1. Ponds, as lakes and rivers, are one of the important inland water. In Japan where rice-culture is carried on extensively, there is a wide distribution of man-made ‘tame-ike’ ponds in addition to natural ones. Unlike lakes, they are small both in area and in depth, and besides being easily subject to the influences of environmental conditions, they have a distinctive character of their water-volume which is able to be regulated artificially. The studies of such ‘tame-ike’ ponds have so far been rather neglected, and many problems still remain unsettled about them, and in particular as the basis of utilizing for pisciculture. The present paper aims at the analytical study of their environmental factors, the elucidation of the relationship between such factors and plankton communities, with which the writer tried to make clear the organic production and metabolism in such a kind of ponds. 2. From the above-stated viewpoints, an attempt was made, (1) to make comparative studies extensively, (2) to perform detailed observations of representative ‘tame-ike’ ponds in regard to their physical and chemical factors, as well as diurnal and seasonal fluctuations of plankton communities. With the three dimensional aspect obtained from the vertical distribution of temperature, pH, O2, & c., and the recovery of planktonic organisms from the drying-up subsequent to drainage, the writer has made an endeavour to reveal the characters of ‘tame-ike’ ponds. 3. In making comparative studies, the pond groups on different geological formations were taken up in the suburbs of Osaka. Aside from the alluvium, geological formations had little effect with the difference from one pond to another. A fairly remarkable difference due to artificial contamination among the pond groups on the diluvium was detected in the water quality, and in the number and quantity of planktonic species. 4. The coastal areas of the Inland Sea have a dense distribution of ‘tame-ike’ ponds hardly seen elsewhere in Japan. As a result of comparative studies of representative ponds in such prefectures as Osaka, Hyĉgo, Okayama, Kagawa and Ehime, natural eutrophication was usually found in a more advanced stage with inland ‘tame-ike’ ponds. Those ‘tame-ike’ pond groups lying near the seashore exposed to either monsoons or typhoons have a larger Cl- content. On the Islands of Sadoga-shima and Okino-shima, where there comes a strong monsoon from the continent, the pond groups on the western coast have a larger Cl- content than those on the eastern coast, which shows the effects of sea-breezes undoubtedly. The Cl-content, however, is seldom found to exceed 100 mg/l and the ponds remain within the confines of freshwater ones, so that the plankton communities in them are composed of freshwater species. The same is not true only in those ponds which are invaded by seawater or which had at one time been connected with the sea. 5. In the coastal areas of the Japan Sea, the pond groups at the seaside of the Tottori sand dunes, or at Kisagata and Konoura beach, Akita pref., at Tsugaru, Aomori pref. are all exposed to the onset of strong monsoons in winter, so that, as a matter of course, they all have a larger Cl- content than any of inland ‘tame-ike’ ponds, but with 44 mg/l at Kidaka beach, Tottori pref. as its maximum, the rest of these pond groups shows smaller contents without exceptions. The ‘tame-ike’ ponds in Akita and Aomori prefectures are not so typical dystrophic as those in Hokkaido, but they have nevertheless a distinctive character of dystrophic ponds in the cold northern districts. © 1961, The Japanese Society of Limnology. All rights reserved.