Abstract
We have treated the result of the analysis of the diatom assemblages contained in the surface layers of the bottom sediments and those attached at aquatic plants, which were gathered in five lakes around Mikata Town, in Fukui Pref., two lakes around Kaga City in Ishikawa Pref., and Kahoku Lagoon. We studied chiefly about the relation between chlorine content, pH and the diatom assemblages. In our study the identified taxon were 44 genera, 135 species, 10 varieties and one form. In the chemical feature of water, the five lakes around Mikata are sea water to mesohaline water, Kahoku Lagoon is mesohaline water, and the two lakes around Kaga City are oligohaline water to fresh water. In the five lakes around Mikata, marine to brackish epiphytic forms are dominant and oceanic planktonic forms are not found at all. Characteristic species are Melosira moniliformis, Cocconeis scutellum, Navicula arenaria. In Kahoku Lagoon brackish epiphytic forms are also dominant, and especially Amphora robusta, Cyclotella striata, Cyclotella meneginiana, Navicula delta and Navicula arenaria are present. The two lakes around Kaga City are characterized by oligohaline species and mesohaline species. The difference between biocoenosis and thanatocoenosis could be recognized, but both of them may be controled by chlorine conditions in the water area.
