兵庫県南部の４湖沼における植物プランクトンの季節的消長：特に黄金藻について

Abstract

Seasonal fluctuation of phytoplankton with special reference to chrysophytes was studied in four ponds and lakes, Doro - ike, Hoshino - ike, Sengari Reservoir and Yasuba- ike, which are situated in the southern part of Hyogo Prefecture, Japan, and are in different stages of eutrophication. The chrysophytes increased in cell number from autumn to spring. The maximum density of the chrysophytes was recorded in March in all the ponds and lakes ; 5, 900 cells·ml-1 in Doro-ike Pond, 13, 000 cells·ml-1in Hoshino - ike Pond, 190 cells·ml-1 in Sengari Reservoir and 6, 900 cells·ml-1 in Yasuba- ike Pond. The chrysophytes were an abundant algal group in the low temperature period and Mallomonas akrokomos, Synura mammillosa, Chrysococcus rufescens and Dinobryon sociale were dominant in the freezing time. Many chrysophyte species occurred not only in oligotrophic waters but also in eutrophic ones, and the number of species increased with eutrophication. The chrysophytes appeared all the year round in oligotrophic waters, whereas, in eutrophic waters, they appeared in the low temperature period with higher density than in oligotrophic waters. But in heavily polluted waters where water blooms of the cyanophytes occurred, the number of species and the density were very low. Based on these, the chrysophytes are regarded as representatives of eutrophic waters as well as of oligotrophic ones.