Abstract
Epilithic diatoms were collected on F e bruary 23 and 24,2002 from two spas,1t45S pa and Yugawara Spa, located in central part of Japan. A total of 20 samples were collected, of which 12 contained diatoms. At sampling sites where diatoms were found, the water temperature ranged from 18-45t, the pH was 6.7-8.7 and the concentration of NaC1 was 0.05-0.16%. A total of 17 diatom taxa were observed. The commonest taxon was Pinnularia joculata which is regarded as a tropical species, followed by Nitzschia amphibia, Achnanthes minutissima, Navicula veneta and Nitzschia microcephala which were considered to be alkalifilous taxa. Dominant taxa were almost the same as the common taxa, though the order was slightly different. Of the 16 identified taxa, only 9 were salt tolerant with a relative frequency of 56.3%, which is reasonable value under low NaCl concentration (0.05-0.16%).
