On the Fossil Diatoms from the Boring Core of Lake Suwa, Nagano Prefecture

Abstract

Fossil diatoms found in seven boring care samples from the bottom of Lake Suwa were investigated. In these samples, 25 genera, 61 species and 22 varieties, including unidentified 3 taxa were found. The composition of the species in samples 1 to 7 and sample 8 of surface mud was almost the same, and Melosira granulata, Melosira japonica, Cyclotella comta, and Fragilaria construens appeared to be dominant. The frequency of Melosira granulata in the current deposit was found to be notably decreasing compared to that in the old deposits. However, whether or not this was caused by the progress of pollution must be studied in detail in the future.