摘要：Seasonal changes in the quality of water and in planktons was investigated in the moat around the Imperial Palace. At present the moat is not polluted by industrial or domestic waste water. The sampling stations were placed at eight points in the moat and the following results were obtained. 1) Changes in the quality of water and in planktons showed a seasonal characteristic pattern. 2) It is considered that water of the moat is eutroph because of the alkalinity and excessive saturation of dissolved oxygen in the water during four seasons and formation of the so-called"aquatic blossom." 3) The prosperity and decay of planktons in the moat are related to BOD, DO, dissolved silicate, and sulfide.
