環境

Benthic diatom flora was studied in five sites of Tama River estuarine area from June 2016 to August 2018 and relationship between diatom assemblage component and environmental factors was examined. Diatom assemblage samples were classified into 3 clusters based on the species component, which were affected by maximum salinity, maximum water temperature and ratio of coarse/fine grains of sediment. 14 diatoms were isolated from sampling sites followed by cultivation in media of various salinities. The result of cultural experiment supported the presence of these diatoms ordinated in CCA. Comparison of the estuarine diatoms with that of Banzu tidal flat, which is located opposite shore 18 km beyond Tokyo Bay showed big difference in their floras. 295 taxa were recorded in Tama River estuary and 286 taxa in Banzu tidal flat. However, common species were 76 taxa in both places. About 60 % of diatoms seemed to be brackish species in the estuary but 60 % marine species in the tidal flat.

Yoshihiko Taguchi

Hiromsa Nomura