Abstract
Characteristics of water quality, seasonal variation of DOC and total nitrogen (T-N) concentrations, in the floating-leaved plant Trapa stand were studied in western part of Lake Imba-numa, Chiba Prefecture during three years from April 1990 to April 1993.
Water was sampled in inside and outside of the Trapa stand once a month during the experimental period. Each sample was filtered through a 0.45 μm membrane filter and used for the water quality analysis.
The results obtained in this study are as follows ; the annual change of DOC concentration is steady, 7.8 mg·l-1, in the inside of Trapa stand. The concentration of T-N has seasonal variation, lower than annual mean value (2.2 mg·l-1) of the quality in summer season and higher than the mean value in winter season respectively, in the inside of Trapa stand.
Similarly, the hourly variations of DOC and T-P concentrations have steady in the inside of Trapa stand.
It is suggested from the experimental study that the variation of DOC and T-N concentrations is strongly affected by the production of vigorous growing plants of Trapa in the western part of Lake Imba-numa.
