Algae. 1989; 4(2): 135-142.
Succession of Diatom Assemblage in Lake Tairo-Ike, Miyakejima Island
Department of Biology, College of Arts and Sciences, the University of Tokyo
From 1984 a succession process of attached diatom assemblage in Lake Tairo-ike which damaged by fallout of scoria or so due to the volcanic eruption occurred on October 3, 1983 has been observed. After the eruption floristic composition of diatom assemblage changed drastically though water conditions changed not so much. Before the eruption dominant species of attached diatom assemblage in the lake were Rhopalodia gibba, Rhop. gibberula, Epithemia sorex, Synedra ulna, Cymbella cistula and so on. After the eruption dominant species are Synedra ulna, its varieties and Fragilaria brevistriata. It was reported that they were dominant planktonic species before the eruption. And they are still dominant in planktonic diatom assemblage after the eruption. It appears that they have come to form new attached assemblage after original attached diatoms had been buried under the scoria. Some other species such as Anomoeoneis exilis, Cymbella microcephala, Achnanthes minutissima, and so on had increased from 1984 to 1986. In this time some construction works were done around the lake, therefore soil or mud were brought into the lake. It is considered that the reasons of the increase of those species are decrease of salinity due to the input of the soil and immigration of those species mixed in the soil.
diatom, immigration, succession, volcanic eruption