Diatoms in Akita Prefecture, northern Japan, part 4—Diatoms and water quality in the Kosaka River, and high concentrations of heavy metals

摘要

Diatom assemblages and water quality were investigated at a site in the Kosaka River into which drainage flows from a non-ferrous metal refinery. At the site electrical conductivity was 1,529 μS/cm and the concentrations of inorganic nitrogen, copper, and zinc were 5.11 mg/L, 14 μg/L, and 130 μg/L, respectively. Only five diatom taxa were recorded; dominant and subdominant species were Achnanthidium minutissimum (88%) and Cyclostephanos fritzii (11%), respectively. A. minutissimum has a special copper-resistance mechanism and is an indicator species of heavy metal-polluted rivers, while the heavy metal tolerance of the other four taxa has never been reported.