Diatoms in Akita Prefecture, northern part of Japan, part 5—Diatom assemblage from a drainage waterway (LD-G1)in Hachirogata polder

摘要

A diatom assemblage in a drainage waterway (LD-G1) of the Hachirogata polder in Akita Prefecture was investigated. The waterway receives spring water with high concentrations of phosphate, and salinity load from the soils of paddy fields. The assemblage comprised 18 genera and 27 taxa, dominated by Navicula gregaria (48%), and followed by Navicula slesvicensis (22%), Navicula salinarum (12%), Nitzschia tubicola (7%) and Navicula lanceolata (7%). The most abundant taxa are eutraphentic or indifferent to saprobity, and circumneutral to alkaliphilous. Moreover, N. salinarum and N. tubicola usually grow in brackish water. Our results suggest that the high concentrations of phosphate, nitrogen and salinity in the LD-G1 water have an influence on the diatom composition.